U.S. patent application number 16/028091 was filed with the patent office on 2018-11-01 for system and method for sensing distance and/or movement.
The applicant listed for this patent is TransRobotics, Inc.. Invention is credited to Sayf AL-ALUSI.
Application Number | 20180313946 16/028091 |
Document ID | / |
Family ID | 46652291 |
Filed Date | 2018-11-01 |
United States Patent
Application |
20180313946 |
Kind Code |
A1 |
AL-ALUSI; Sayf |
November 1, 2018 |
SYSTEM AND METHOD FOR SENSING DISTANCE AND/OR MOVEMENT
Abstract
A method (e.g., a method for measuring a separation distance to
a target object) includes transmitting an electromagnetic first
transmitted signal from a transmitting antenna toward a target
object that is a separated from the transmitting antenna by a
separation distance. The first transmitted signal includes a first
transmit pattern representative of a first sequence of digital
bits. The method also includes receiving a first echo of the first
transmitted signal that is reflected off the target object,
converting the first echo into a first digitized echo signal, and
comparing a first receive pattern representative of a second
sequence of digital bits to the first digitized echo signal to
determine a time of flight of the first transmitted signal and the
echo.
Inventors: |
AL-ALUSI; Sayf; (Hayward,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TransRobotics, Inc. |
Hayward |
CA |
US |
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|
Family ID: |
46652291 |
Appl. No.: |
16/028091 |
Filed: |
July 5, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15798911 |
Oct 31, 2017 |
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16028091 |
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14668395 |
Mar 25, 2015 |
9835720 |
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15798911 |
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13400261 |
Feb 20, 2012 |
9019150 |
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14668395 |
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61521378 |
Aug 9, 2011 |
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61445026 |
Feb 21, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 13/325 20130101;
G01S 17/32 20130101; G01S 17/36 20130101; G01S 7/03 20130101; G01S
13/36 20130101; G01S 7/352 20130101; G01S 2007/358 20130101; G01S
7/497 20130101; G01S 7/41 20130101; G01S 13/103 20130101; G01S
13/88 20130101; G01S 13/867 20130101 |
International
Class: |
G01S 13/36 20060101
G01S013/36; G01S 17/36 20060101 G01S017/36; G01S 13/10 20060101
G01S013/10; G01S 13/86 20060101 G01S013/86; G01S 7/41 20060101
G01S007/41; G01S 7/03 20060101 G01S007/03 |
Claims
1. A digital radar method comprising the steps of: generating a
transmission signal from a transmission sequence including a
digital transmit pattern; transmitting the transmission signal from
a first antenna; receiving an analog echo signal at a second
antenna, the analog echo signal including reflections of the
transmission signal off one or more objects; generating a baseband
echo signal from the analog echo signal; prior to performing any
comparisons with any echo signal, digitizing the baseband echo
signal to generate a digital echo pattern; and comparing the
digital echo pattern to a digital receive pattern.
2. The digital radar method of claim 1, wherein generating the
transmission signal includes inserting the digital transmit pattern
into a digital stream to create the transmission sequence.
3. The digital radar method of claim 1, wherein generating the
transmission signal includes identifying the digital transmit
pattern in a digital stream to create the transmission
sequence.
4. The digital radar method of claim 1, further comprising:
calculating a time of flight of the transmission signal based on
the compared signal.
5. The digital radar method of claim 4, further comprising:
calculating a separation distance from the first antenna to the one
or more objects based on the time of flight.
6. The digital radar method of claim 1, wherein the digital
transmit pattern is representative of a first sequence of bits and
the digital receive pattern is representative of a second sequence
of bits.
7. The digital radar method of claim 6, wherein the first sequence
of bits and the second sequence of bits are different.
8. The digital radar method of claim 6, wherein the first sequence
of bits and the second sequence of bits are the same.
9. The digital radar method of claim 7, wherein the difference
between the first sequence of bits and second sequence of bits is
at least one of: bit length, and one or more bit value
differences.
10. The digital radar method of claim 6, wherein comparing the
digital echo pattern to the digital receive pattern further
comprises: comparing the second sequence of bits to segments of the
digital echo pattern to calculate correlation values for each
segment, each correlation value representing a degree of match
between the second sequence of bits and each segment of the digital
echo pattern.
11. The digital radar method of claim 10, wherein at least one
segment of the digital echo pattern is identified as a segment of
interest based on its correlation value exceeding a threshold
value, and wherein the time of flight is determined based on a time
delay between transmission of the transmitted signal and an
occurrence time of the segment of interest determined from the
digital echo pattern.
12. The digital radar method of claim 1, wherein the digital
transmit pattern includes a plurality of repeating patterns.
13. The digital radar method of claim 1, wherein the digital
transmit pattern includes a plurality of different patterns
provided sequentially.
14. The digital radar method of claim 1, wherein the first and
second antennas are the same antenna.
15. The digital radar method of claim 1, wherein at least one of
the first and second antennas is directional.
16. A digital radar system comprising: a transmitter configured to
generate a transmission signal from a transmission sequence
including a digital transmit pattern and transmit the transmission
signal from a first antenna; a receiver configured to receive an
analog echo signal at a second antenna, to generate a baseband echo
signal from the analog echo signal, and prior to performing any
comparisons with any echo signal, to digitize the received baseband
echo signal to generate a digital echo pattern, and a correlator
configured to compare the digital echo pattern to a digital receive
pattern, wherein the analog echo signal includes reflections of the
transmission signal off one or more objects.
17. The digital radar method of claim 16, wherein generating the
transmission signal includes inserting the digital transmit pattern
into a digital stream to create the transmission sequence.
18. The digital radar method of claim 16, wherein generating the
transmission signal includes identifying the digital transmit
pattern in a digital stream to create the transmission
sequence.
19. The digital radar system of claim 16, further comprising: a
processor configured to calculate a time of flight of the
transmission signal based on the compared signal.
20. The digital radar system of claim 19, wherein the processor is
further configured to calculate a separation distance from the
transmitter to the one or more objects based on the time of
flight.
21. The digital radar system of claim 16, wherein the digital
transmit pattern is representative of a first sequence of bits and
the digital receive pattern is representative of a second sequence
of bits.
22. The digital radar system of claim 21, wherein the first
sequence of bits and the second sequence of bits are different.
23. The digital radar method of claim 21, wherein the first
sequence of bits and the second sequence of bits are the same.
24. The digital radar system of claim 22, wherein the difference
between the first sequence of bits and second sequence of bits is
at least one of: bit length, or one or more bit value
differences.
25. The digital radar system of claim 21, wherein the correlator is
further configured to compare the second sequence of bits to
segments of the digital echo pattern to calculate correlation
values for each segment, each correlation value representing a
degree of match between the second sequence of bits and each
segment of the digital echo pattern.
26. The digital radar system of claim 25, wherein at least one
segment of the digital echo pattern is identified as a segment of
interest based on its correlation value exceeding a threshold
value, and wherein the time of flight is determined based on a time
delay between transmission of the transmitted signal and an
occurrence time of the segment of interest determined from the
digital echo pattern.
27. The digital radar system of claim 16, wherein the digital
transmit pattern includes a plurality of repeating patterns.
28. The digital radar system of claim 16, wherein the digital
transmit pattern includes a plurality of different patterns
provided sequentially.
29. The digital radar system of claim 16, wherein the first and
second antennas are the same antenna.
30. The digital radar system of claim 16, wherein at least one of
the first and second antennas is directional.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/798,911 filed Oct. 31, 2017, which is a
continuation of U.S. patent application Ser. No. 14/668,395 filed
Mar. 25, 2015, now U.S. Pat. No. 9,835,720, which is a continuation
of U.S. patent application Ser. No. 13/400,261 filed on Feb. 20,
2012, now U.S. Pat. No. 9,019,150, and claims priority benefit to
U.S. Provisional Application No. 61/445,026, which was filed on
Feb. 21, 2011 and U.S. Provisional Application No. 61/521,378,
which was filed on Aug. 9, 2011, all of which are hereby
incorporated by reference in their entirety for all purposes as if
fully set forth herein.
BACKGROUND
[0002] One or more embodiments of the subject matter described
herein relate to distance and/or motion sensing systems and
methods, such as radar and/or optical remote sensing systems and
methods.
[0003] Known radar systems transmit analog electromagnetic waves
toward targets and receive echoes of the waves that reflect off the
targets. Based on the distance between antennas that transmit the
analog waves and the target objects, and/or movement of the target
objects, the strength and/or frequency of the received echoes may
change. The strength, frequency, and/or time-of-flight of the
echoes may be used to derive the distance to the targets and/or
movement of the targets.
[0004] Some known radar systems are limited in the accuracy at
which the systems can measure distances to the targets. For
example, the resolution at which these systems may be able to
calculate the distance to targets may be relatively large.
Moreover, some of these systems may have circuitry, such as a
transmit/receive switch, that controls when the systems transmit
waves or receive echoes. The switch can require a non-zero period
of time to allow the systems to switch from transmitting waves to
receiving echoes. This period of time may prevent the systems from
being used to measure distances to targets that are relatively
close, as the transmitted waves may reflect off the targets back to
the receiving antennas before the systems can switch from
transmission to reception. Additionally, some known systems have
energy leakage from the transmitting antenna to the receiving
antenna. This energy leakage can interfere with and/or obscure the
measurement of distances to the targets and/or the detection of
motion.
BRIEF DESCRIPTION
[0005] In one embodiment, a method (e.g., a method for measuring a
separation distance to a target object) is provided. The method
includes transmitting an electromagnetic first transmitted signal
from a transmitting antenna toward a target object that is a
separated from the transmitting antenna by a separation distance.
The first transmitted signal includes a first transmit pattern
representative of a first sequence of digital bits. The method also
includes receiving a first echo of the first transmitted signal
that is reflected off the target object, converting the first echo
into a first digitized echo signal, and comparing a first receive
pattern representative of a second sequence of digital bits to the
first digitized echo signal to determine a time of flight of the
first transmitted signal and the echo.
[0006] In another embodiment, a system (e.g., a sensing system) is
provided that includes a transmitter, a receiver, and a correlator
device. The transmitter is configured to generate an
electromagnetic first transmitted signal that is communicated from
a transmitting antenna toward a target object that is a separated
from the transmitting antenna by a separation distance. The first
transmitted signal includes a first transmit pattern representative
of a sequence of digital bits. The receiver is configured to
generate a first digitized echo signal that is based on an echo of
the first transmitted signal that is reflected off the target
object. The correlator device is configured to compare a first
receive pattern representative of a second sequence of digital bits
to the first digitized echo signal to determine a time of flight of
the first transmitted signal and the echo.
[0007] In another embodiment, another method (e.g., for measuring a
separation distance to a target object) is provided. The method
includes transmitting a first transmitted signal having waveforms
representative of a first transmit pattern of digital bits and
generating a first digitized echo signal based on a first received
echo of the first transmitted signal. The first digitized echo
signal includes waveforms representative of a data stream of
digital bits. The method also includes comparing a first receive
pattern of digital bits to plural different subsets of the data
stream of digital bits in the first digitized echo signal to
identify a subset of interest that more closely matches the first
receive pattern than one or more other subsets. The method further
includes identifying a time of flight of the first transmitted
signal and the first received echo based on a time delay between a
start of the data stream in the first digitized echo signal and the
subset of interest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present subject matter will be better understood from
reading the following description of non-limiting embodiments, with
reference to the attached drawings, wherein below:
[0009] FIG. 1 is a schematic diagram of one embodiment of a sensing
system;
[0010] FIG. 2 is a schematic diagram of one embodiment of a sensing
apparatus shown in FIG. 1;
[0011] FIG. 3A is a schematic diagram of a coarse stage
determination of a time of flight for a transmitted signal and
corresponding echo in accordance with one embodiment.
[0012] FIG. 3B is another schematic diagram of the coarse stage
determination of a time of flight for a transmitted signal and
corresponding echo in accordance with one embodiment.
[0013] FIG. 4 illustrates one example of correlation values that
are calculated and averaged over several transmitted signals shown
in FIG. 1;
[0014] FIG. 5 is another schematic diagram of part or one
implementation of the sensing assembly shown in FIG. 2;
[0015] FIG. 6 is a schematic diagram of one embodiment of a front
end of the sensing assembly shown in FIG. 2;
[0016] FIG. 7 is a circuit diagram of one embodiment of a baseband
processing system of the system shown in FIG. 1;
[0017] FIG. 8 is a schematic diagram of one example of how a
comparison device compares a bit of interest of a baseband echo
signal shown in FIG. 2 with a pattern bit of a pattern signal shown
in FIG. 2 in one embodiment;
[0018] FIG. 9 illustrates another example of how the comparison
device shown in FIG. 7 compares a bit of interest of the baseband
echo signal shown in FIG. 2 with a pattern bit of the pattern
signal shown in FIG. 2;
[0019] FIG. 10 illustrates another example of how the comparison
device shown in FIG. 7 compares a bit of interest of the baseband
echo signal shown in FIG. 2 with a pattern bit of the pattern
signal shown in FIG. 2;
[0020] FIG. 11 illustrates examples of output signals shown in FIG.
7 provided by measurement devices shown in FIG. 7 and energy
thresholds used by a CPU device shown in FIG. 2 in accordance with
one example;
[0021] FIG. 12 is a circuit diagram of another embodiment of a
baseband processing system of the system shown in FIG. 1;
[0022] FIG. 13 illustrates projections of in-phase (I) and
quadrature (Q) components of a digitized echo signal shown in FIG.
2 in accordance with one embodiment;
[0023] FIG. 14 illustrates a technique for distinguishing between
echoes shown in FIG. 1 that are reflected off different target
objects 104 shown in FIG. 1 in accordance with one embodiment;
[0024] FIG. 15 is a schematic view of an antenna in accordance with
one embodiment;
[0025] FIG. 16 is a schematic diagram of one embodiment of a front
end of the sensing assembly shown in FIG. 1;
[0026] FIG. 17 is a cross-sectional view of one embodiment of the
antenna shown in FIG. 15 along line 17-17 in FIG. 16;
[0027] FIG. 18 illustrates one embodiment of a containment
system;
[0028] FIG. 19 illustrates one embodiment of a zone restriction
system;
[0029] FIG. 20 illustrates another embodiment of a volume
restriction system;
[0030] FIG. 21 is a schematic diagram of one embodiment of a mobile
system;
[0031] FIG. 22 is a schematic diagram of several object motion
vectors in accordance with one example;
[0032] FIG. 23 is a schematic diagram of one example of using the
sensing assembly shown in FIG. 1 in a medical application;
[0033] FIG. 24 is a two-dimensional image of human subjects in
accordance with one example of an application of the system shown
in FIG. 1;
[0034] FIG. 25 is a schematic diagram of another embodiment of a
sensing system;
[0035] FIG. 26 is a schematic diagram of another embodiment of a
sensing system;
[0036] FIGS. 27A-B illustrate one embodiment of a method for
sensing separation distances from a target object and/or motion of
the target object;
[0037] FIG. 28 is a schematic diagram of a sensing system in
accordance with another embodiment;
[0038] FIG. 29 is a schematic diagram representative of lateral
size data of a target object that is obtained by the sensing system
shown in FIG. 28; and
[0039] FIG. 30 is another view of a sensing assembly and the target
object shown in FIGS. 28 and 29.
DETAILED DESCRIPTION
[0040] In accordance with one or more embodiments of the presently
described inventive subject matter, systems and methods are
provided for determining distances between a sensing apparatus and
one or more targets. The distances may be determined by measuring
times of flight of transmitted signals (e.g., radar, light, or
other signals) that reflect off the targets. As one example, a
signal that includes a known or designated transmit pattern (such
as waveforms that represent a sequence of bits) is transmitted and
echoes of this signal are received. This transmit pattern can be
referred to as a coarse stage transmit pattern. The echoes may
include information representative of the pattern in the
transmitted signal. For example, the echoes may be received and
digitized to identify a sequence or stream of data that is
representative of noise, partial reflections of the transmitted
signal off one or more objects other than the target, and
reflections off the target.
[0041] A coarse stage receive pattern can be compared to the
digitized data stream that is based on the received echoes to
determine a time of flight of the transmitted signal. The coarse
stage receive pattern can be the same as the transmit pattern or
differ from the transmit pattern by having a different length
and/or sequence of bits (e.g., "0" and "1"). The coarse stage
receive pattern is compared to different portions of the digitized
data stream to determine which portion of the data stream more
closely matches the receive pattern than one or more other
portions. For example, the coarse stage receive pattern may be
shifted (e.g., with respect to time) along the data stream to
identify a portion of the data stream that matches the coarse stage
receive pattern. A time delay between the start of the data stream
and the matching portion of the coarse stage receive pattern may
represent the time of flight of the transmitted signal. This
measurement of the time of flight may be used to calculate a
separation distance to the target. As described below, this process
for measuring the time of flight may be referred to as coarse stage
determination of the time of flight. The coarse stage determination
may be performed once or several times in order to measure the time
of flight. For example, a single "burst" of a transmitted signal
may be used to measure the time of flight, or several "bursts" of
transmitted signals (having the same or different transmit
patterns) may be used.
[0042] A fine stage determination may be performed in addition to
or in place of the coarse stage determination. The fine stage
determination can include transmitting one or more additional
signals (e.g., "bursts") toward the target and generating one or
more baseband echo signals based on the received echoes of the
signals. The additional signals may include a fine stage transmit
pattern that is the same or different pattern as the coarse stage
transmit pattern. The fine stage determination can use the time of
flight measured by the coarse stage determination (or as input by
an operator) and compare a fine stage receive pattern that is
delayed by the measured time of flight to a corresponding portion
of the data stream. For example, instead of shifting the fine stage
receive pattern along all or a substantial portion of the baseband
echo signal, the fine stage receive pattern (or a portion thereof)
can be time shifted by an amount that is equal to or based on the
time delay measured by the coarse stage determination.
Alternatively, the fine stage receive pattern may be shifted along
all or a substantial portion of the baseband echo signal. The
time-shifted fine stage receive pattern can be compared to the
baseband echo signal to determine an amount of overlap or,
alternatively, an amount of mismatch between the waveforms of the
time-shifted fine stage receive pattern and the baseband echo
signal. This amount of overlap or mismatch may be translated to an
additional time delay. The additional time delay can be added with
the time delay measured by the coarse stage determination to
calculate a fine stage time delay. The fine stage time delay can
then be used to calculate a time of flight and separation distance
to the target.
[0043] In one embodiment, an ultrafine stage determination may be
performed in addition to or in place of the coarse stage
determination and/or the fine stage determination. The ultrafine
stage determination can involve a similar process as the fine stage
determination, but using a different component of the receive
pattern and/or the data stream. For example, the fine stage
determination may examine the in-phase (I) component or channel of
the receive pattern and the data stream to measure the overlap or
mismatch between the receive pattern and the data stream. The
ultrafine stage determination can use the quadrature (Q) component
or channel of the receive pattern and the data stream to measure an
additional amount of overlap or mismatch between the waveforms of
the receive pattern and the data stream. Alternatively, the
ultrafine stage determination may separately examine the I channel
and Q channel of the receive pattern and the data stream. The use
of I and Q channels or components is provided as one example
embodiment. Alternatively, one or more other channels or components
may be used. For example, a first component or channel and a second
component or channel may be used, where the first and second
components or channels are phase shifted relative to each other by
an amount other than ninety degrees.
[0044] The amounts of overlap or mismatch calculated by the
ultrafine stage determination can be used to calculate an
additional time delay that can be added to the time delays from the
coarse stage and/or the fine stage to determine a time of flight
and/or separation distance to the target. Alternatively or
additionally, the amount of overlap or mismatch between the
waveforms in the I channel and Q channel can be examined to resolve
phases of the echoes in order to detect motion of the target.
[0045] Alternatively or additionally, the ultrafine stage
determination may involve a similar process as the coarse stage
determination. For example, the coarse stage determination may
examine the I channel of the receive pattern and the data stream to
determine correlation values of different subsets of the data
stream and, from those correlation values, determine a subset of
interest and a corresponding time-of-flight, as described herein.
The ultrafine stage determination can use the Q channel of the
receive pattern and the data stream to determine correlation values
of different subsets of the data stream and, from those correlation
values, determine a subset of interest and a time-of-flight. The
times-of-flight from the I channel and Q channel can be combined
(e.g., averaged) to calculate a time of flight and/or separation
distance to the target. The correlation values calculated by the
ultrafine stage determination can be used to calculate an
additional time delay that can be added to the time delays from the
coarse stage and/or the fine stage to determine a time of flight
and/or separation distance to the target. Alternatively or
additionally, the correlation values of the waveforms in the I
channel and Q channel can be examined to resolve phases of the
echoes in order to calculate separation distance or motion of the
target.
[0046] The coarse, fine, and ultrafine stage determinations can be
performed independently (e.g., without performing one or more of
the other stages) and/or together. The fine and ultrafine stage
determinations can be performed in parallel (e.g., with the fine
stage determination examining the I channel and the ultrafine stage
determination examining the Q channel) or sequentially (e.g., with
the ultrafine stage determination examining both the I and Q
channels). The coarse and ultrafine stage determinations can be
performed in parallel (e.g., with the coarse stage determination
examining the I channel and the ultrafine stage determination
examining the Q channel) or sequentially (e.g., with the ultrafine
stage determination examining both the I and Q channels).
[0047] In one embodiment, a receive pattern mask may be applied to
the digitized data stream to remove (e.g., mask off) or otherwise
change one or more portions or segments of the data stream. The
masked data stream can then be compared to the receive pattern of
the corresponding stage determination (e.g., coarse stage, fine
stage, or ultrafine stage) to measure the time of flight, as
described herein.
[0048] In one embodiment, the various patterns (e.g., the coarse
stage transmit pattern, the fine stage transmit pattern, the coarse
stage receive pattern, the fine stage receive pattern, and/or the
receive pattern mask) may be the same. Alternatively, one or more
(or all) of these patterns may differ from each other. For example,
different ones of the patterns may include different sequences of
bits and/or lengths of the sequences. The various patterns (e.g.,
the coarse stage transmit pattern, the fine stage transmit pattern,
the coarse stage receive pattern, the fine stage receive pattern,
and/or the receive pattern mask) that are used in the ultrafine
stage may also differ from those used in the coarse or fine stages
alone, and from each other.
[0049] FIG. 1 is a schematic diagram of one embodiment of a sensing
system 100. The system 100 can be used to determine distances
between a sensing apparatus 102 and one or more objects 104 and/or
to identify movement of the one or more target objects 104, where
the target objects 104 may have positions that may change or that
are not known. In one embodiment, the sensing apparatus 102
includes a radar system that transmits electromagnetic pulse
sequences as transmitted signals 106 toward the target object 104
that are at least partially reflected as echoes 108. Alternatively,
the sensing apparatus 102 can include an optical sensing system,
such as a LIght Detection And Ranging (LIDAR) system, that
transmits light toward the target object 104 as the transmitted
signals 106 and receives reflections of the light off the target
object 104 as the echoes 108. In another embodiment, another method
of transmission may be used, such as sonar, in order to transmit
the transmitted signals 106 and receive the echoes 108.
[0050] A time of flight of the transmitted signals 106 and echoes
108 represents the time delay between transmission of the
transmitted signals 106 and receipt of the echoes 108 off of the
target object 104. The time of flight can be proportional to a
distance between the sensing apparatus 102 and the target object
104. The sensing apparatus 102 can measure the time of flight of
the transmitted signals 106 and echoes 108 and calculate a
separation distance 110 between the sensing apparatus 102 and the
target object 104 based on the time of flight.
[0051] The sensing system 100 may include a control unit 112
("External Control Unit" in FIG. 1) that directs operations of the
sensing apparatus 102. The control unit 112 can include one or more
logic-based hardware devices, such as one or more processors,
controllers, and the like. The control unit 112 shown in FIG. 1 may
represent the hardware (e.g., processors) and/or logic of the
hardware (e.g., one or more sets of instructions for directing
operations of the hardware that is stored on a tangible and
non-transitory computer readable storage medium, such as computer
software stored on a computer memory). The control unit 112 can be
communicatively coupled (e.g., connected so as to communicate data
signals) with the sensing apparatus 102 by one or more wired and/or
wireless connections. The control unit 112 may be remotely located
from the sensing apparatus 102, such as by being disposed several
meters away, in another room of a building, in another building, in
another city block, in another city, in another county, state, or
country (or other geographic boundary), and the like.
[0052] In one embodiment, the control unit 112 can be
communicatively coupled with several sensing assemblies 102 located
in the same or different places. For example, several sensing
assemblies 102 that are remotely located from each other may be
communicatively coupled with a common control unit 112. The control
unit 112 can separately send control messages to each of the
sensing assemblies 102 to individually activate (e.g., turn ON) or
deactivate (e.g., turn OFF) the sensing assemblies 102. In one
embodiment, the control unit 112 may direct the sensing assembly
102 to take periodic measurements of the separation distance 110
and then deactivate for an idle time to conserve power.
[0053] In one embodiment, the control unit 112 can direct the
sensing apparatus 102 to activate (e.g., turn ON) and/or deactivate
(e.g., turn OFF) to transmit transmitted signals 106 and receive
echoes 108 and/or to measure the separation distances 110.
Alternatively, the control unit 112 may calculate the separation
distance 110 based on the times of flight of the transmitted
signals 106 and echoes 108 as measured by the sensing apparatus 102
and communicated to the control unit 112. The control unit 112 can
be communicatively coupled with an input device 114, such as a
keyboard, electronic mouse, touchscreen, microphone, stylus, and
the like, and/or an output device 116, such as a computer monitor,
touchscreen (e.g., the same touchscreen as the input device 114),
speaker, light, and the like. The input device 114 may receive
input data from an operator, such as commands to activate or
deactivate the sensing apparatus 102. The output device 116 may
present information to the operator, such as the separation
distances 110 and/or times of flight of the transmitted signals 106
and echoes 108. The output device 116 may also connect to a
communications network, such the internet.
[0054] The form factor of the sensing assembly 102 may have a wide
variety of different shapes, depending on the application or use of
the system 100. The sensing assembly 102 may be enclosed in a
single enclosure 1602, such as an outer housing. The shape of the
enclosure 1602 may depend on factors including, but not limited to,
needs for power supply (e.g., batteries and/or other power
connections), environmental protection, and/or other communications
devices (e.g., network devices to transmit measurements or
transmit/receive other communications). In the illustrated
embodiment, the basic shape of the sensing assembly 102 is a
rectangular box. The size of the sensing assembly 102 can be
relatively small, such as three inches by six inches by two inches
(7.6 centimeters by 15.2 centimeters by 5.1 centimeters), 70 mm by
140 mm by 10 mm, or another size. Alternatively, the sensing
assembly 102 may have one or more other dimensions.
[0055] FIG. 2 is a schematic diagram of one embodiment of the
sensing apparatus 102. The sensing apparatus 102 may be a
direct-sequence spread-spectrum radar device that uses a relatively
high speed digital pulse sequence that directly modulates a carrier
signal, which is then transmitted as the transmitted signals 106
toward a target object 104. The echoes 108 may be correlated to the
same pulse sequence in the transmitted signals 106 in order to
determine the time of flight of the transmitted signals 106 and
echoes 108. This time of flight can then be used to calculate the
separation distance 110 (shown in FIG. 1).
[0056] The sensing apparatus 102 includes a front end 200 and a
back end 202. The front end 200 may include the circuitry and/or
other hardware that transmits the transmitted signals 106 and
receives the reflected echoes 108. The back end 202 may include the
circuitry and/or other hardware that forms the pulse sequences for
the transmitted signals 106 or generates control signals that
direct the front end 200 to form the pulse sequences for inclusion
in the transmitted signals 106, and/or that processes (e.g.,
analyzes) the echoes 108 received by the front end 200. Both the
front end 200 and the back end 202 may be included in a common
housing. For example (and as described below), the front end 200
and the back end 202 may be relatively close to each other (e.g.,
within a few centimeters or meters) and/or contained in the same
housing. Alternatively, the front end 200 may be remotely located
from the back end 202. The components of the front end 200 and/or
back end 202 are schematically shown as being connected by lines
and/or arrows in FIG. 2, which may be representative of conductive
connections (e.g., wires, busses, and the like) and/or wireless
connections (e.g., wireless networks).
[0057] The front end 200 includes a transmitting antenna 204 and a
receiving antenna 206. The transmitting antenna 204 transmits the
transmitted signals 106 toward the target object 104 and the
receiving antenna 206 receives the echoes 108 that are at least
partially reflected by the target object 104. As one example, the
transmitting antenna 204 may transmit radio frequency (RF)
electromagnetic signals as the transmitted signals 106, such as RF
signals having a frequency of 24 gigahertz ("GHz").+-.1.5 GHz.
Alternatively, the transmitting antenna 204 may transmit other
types of signals, such as light, and/or at another frequency. In
the case of light transmission the antenna may be replaced by a
laser or LED or other device. The receiver may be replaced by a
photo detector or photodiode.
[0058] A front end transmitter 208 ("RF Front-End," "Transmitter,
and/or "TX" in FIG. 2) of the front end 200 is communicatively
coupled with the transmitting antenna 204. The front end
transmitter 208 forms and provides the transmitted signal 106 to
the transmitting antenna 204 so that the transmitting antenna 204
can communicate (e.g., transmit) the transmitted signal 106. In the
illustrated embodiment, the front end transmitter 208 includes
mixers 210A, 210B and an amplifier 212. Alternatively, the front
end transmitter 208 may not include the amplifier 212. The mixers
210A, 210B combine (e.g., modulate) a pulse sequence or pattern
provided by the back end 202 with an oscillating signal 216 (e.g.,
a carrier signal) to form the transmitted signal 106 that is
communicated by the transmitting antenna 204. In one embodiment,
the mixers 210A, 210B multiply pattern signals 230A, 230B
("Baseband signal" in FIG. 2) received from one or more transmit
(TX) pattern generators 228A, 228B by the oscillating signal 216.
The pattern signal 230 includes the pattern formed by the pattern
code generator 228. As described below, the pattern signal 230 can
include several bits arranged in a known or designated
sequence.
[0059] An oscillating device 214 ("Oscillator" in FIG. 2) of the
front end 200 generates the oscillating signal 216 that is
communicated to the mixers 210A, 210B. As one example, the
oscillating device 214 may include or represent a voltage
controlled oscillator (VCO) that generates the oscillating signal
216 based on a voltage signal that is input into the oscillating
device 214, such as by a power source (e.g., battery) disposed in
the sensing apparatus 102 and/or as provided by the control unit
112 (shown in FIG. 1). The amplifier 212 may increase the strength
(e.g., gain) of the transmitted signal 106.
[0060] In the illustrated embodiment, the mixer 210A receives an
in-phase (I) component or channel of a pattern signal 230A and
mixes the I component or channel of the pattern signal 230A with
the oscillating signal 216 to form an I component or channel of the
transmitted signal 106. The mixer 210B receives a quadrature (Q)
component or channel of a pattern signal 230B and mixes the I
component or channel of the pattern signal 230B with the
oscillating signal 216 to form a Q component or channel of the
transmitted signal 106.
[0061] The transmitted signal 106 (e.g., one or both of the I and Q
channels) is generated when the TX baseband signal 230 flows to the
mixers 210. The digital output gate 250 may be disposed between the
TX pattern generator and the mixers 210 for added control of the TX
baseband signal 230. After a burst of one or more transmitted
signals 106 is transmitted by the transmitting antenna 204, the
sensing assembly 102 may switch from a transmit mode (e.g., that
involves transmission of the transmitted signals 106) to a receive
mode to receive the echoes 108 off the target object 104. In one
embodiment, the sensing assembly 102 may not receive or sense the
echoes 108 when in the transmit mode and/or may not transmit the
transmitted signals 106 when in the receive mode. When the sensing
assembly 102 switches from the transmit mode to the receive mode,
the digital output gate 250 can reduce the amount of time that the
transmit signal 106 generated by the transmitter 208 to the point
that it is eliminated (e.g., reduced to zero strength). For
example, the gate 250 can include tri-state functionality and a
differential high-pass filter (which is represented by the gate
250). The baseband signal 230 passes through the filter before the
baseband signal 230 reaches the upconversion mixer 210. The gate
250 can be communicatively coupled with, and controlled by, the
control unit 112 (shown in FIG. 1) so that the control unit 112 can
direct the filter of the gate 250 to enter into a tri-state (e.g.,
high-impedance) mode when the transmitted signal 106 (or burst of
several transmitted signals 106) is transmitted and the sensing
assembly 102 is to switch over to receive the echoes 108. The
highpass filter across differential outputs of the gate 250 can
reduce the input transmit signal 106 relatively quickly after the
tri-state mode is initiated. As a result, the transmitted signal
106 is prevented from flowing to the transmitting antenna 204
and/or from leaking to the receiving antenna 206 when the sensing
assembly 102 receives the echoes 108.
[0062] A front end receiver 218 ("RF Front-End," "Receiver," and/or
"RX") of the front end 200 is communicatively coupled with the
receiving antenna 206. The front end receiver 218 receives an echo
signal 224 representative of the echoes 108 (or data representative
of the echoes 108) from the receiving antenna 206. The echo signal
224 may be an analog signal in one embodiment. The receiving
antenna 206 may generate the echo signal 224 based on the received
echoes 108. In the illustrated embodiment, an amplifier 238 may be
disposed between the receive antenna 206 and the front end receiver
218. The front end receiver 218 can include an amplifier 220 and
mixers 222A, 222B. Alternatively, one or more of the amplifiers
220, 238 may not be provided. The amplifiers 220, 238 can increase
the strength (e.g., gain) of the echo signal 224. The mixers 222A,
222B may include or represent one or more mixing devices that
receive different components or channels of the echo signal 224 to
mix with the oscillating signal 216 (or a copy of the oscillating
signal 216) from the oscillating device 214. For example, the mixer
222A can combine the analog echo signal 224 and the I component of
the oscillating signal 216 to extract the I component of the echo
signal 224 into a first baseband echo signal 226A that is
communicated to the back end 202 of the sensing apparatus 102. The
first baseband echo signal 226A may include the I component or
channel of the baseband echo signal. The mixer 222B can combine the
analog echo signal 224 and the Q component of the oscillating
signal 216 to extract the Q component of the analog echo signal 224
into a second baseband echo signal 226B that is communicated to the
back end 202 of the sensing apparatus 102. The second baseband echo
signal 226B can include the Q component or channel of the baseband
echo signal. In one embodiment, the echo signals 226A, 226B can be
collectively referred to as a baseband echo signal 226. In one
embodiment, the mixers 222A, 222B can multiply the echo signal 224
by the I and Q components of the oscillating signal 216 to form the
baseband echo signals 226A, 226B.
[0063] The back end 202 of the sensing apparatus 102 includes a
transmit (TX) pattern code generator 228 that generates the pattern
signal 230 for inclusion in the transmitted signal 106. The
transmit pattern code generator 228 includes the transmit code
generators 228A, 228B. In the illustrated embodiment, the transmit
code generator 228A generates the I component or channel pattern
signal 230A ("I TX Pattern" in FIG. 2) while the transmit code
generator 228B generates the Q component or channel pattern signal
230B ("Q TX Pattern" in FIG. 2). The transmit patterns generated by
the transmit pattern code generator 228 can include a digital pulse
sequence having a known or designated sequence of binary digits, or
bits. A bit includes a unit of information that may have one of two
values, such as a value of one or zero, high or low, ON or OFF, +1
or -1, and the like. Alternatively, a bit may be replaced by a
digit, a unit of information that may have one of three or more
values, and the like. The pulse sequence may be selected by an
operator of the system 100 shown in FIG. 1 (such as by using the
input device 114 shown in FIG. 1), may be hard-wired or programmed
into the logic of the pattern code generator 228, or may otherwise
be established.
[0064] The transmit pattern code generator 228 creates the pattern
of bits and communicates the pattern in the pattern signals 230A,
230B to the front end transmitter 208. The pattern signals 230A,
230B may be individually or collectively referred to as a pattern
signal 230. In one embodiment, the pattern signal 230 may be
communicated to the front end transmitter 208 at a frequency that
is no greater than 3 GHz. Alternatively, the pattern signal 230 may
be communicated to the front end transmitter 208 at a greater
frequency. The transmit pattern code generator 228 also
communicates the pattern signal 230 to a correlator device 232
("Correlator" in FIG. 2). For example, the pattern code generator
228 may generate a copy of the pattern signal that is sent to the
correlator device 232.
[0065] The backend section 202 includes or represents hardware
(e.g., one or more processors, controllers, and the like) and/or
logic of the hardware (e.g., one or more sets of instructions for
directing operations of the hardware that is stored on a tangible
and non-transitory computer readable storage medium, such as
computer software stored on a computer memory). The RX backend
section 202B receives the pattern signal 230 from the pattern code
generator 228 and the baseband echo signal 226 (e.g., one or more
of the signals 226A, 226B) from the front end receiver 200. The RX
backend section 202B may perform one or more stages of analysis of
the baseband echo signal 226 in order to determine the separation
distance 110 and/or to track and/or detect movement of the target
object 104.
[0066] The stages of analysis can include a coarse stage, a fine
stage, and/or an ultrafine stage, as described above. In the coarse
stage, the baseband processor 232 compares the pattern signal 230
with the baseband echo signal 226 to determine a coarse or
estimated time of flight of the transmitted signals 106 and the
echoes 108. For example, the baseband processor 232 can measure a
time delay of interest between the time when a transmitted signal
106 is transmitted and a subsequent time when the pattern in the
pattern signal 230 (or a portion thereof) and the baseband echo
signal 226 match or substantially match each other, as described
below. The time delay of interest may be used as an estimate of the
time of flight of the transmitted signal 106 and corresponding echo
108.
[0067] In the fine stage, the sensing assembly 102 can compare a
replicated copy of the pattern signal 230 with the baseband echo
signal 226. The replicated copy of the pattern signal 230 may be a
signal that includes the pattern signal 230 delayed by the time
delay of interest measured during the coarse stage. The sensing
assembly 102 compares the replicated copy of the pattern signal 230
with the baseband echo signal 226 to determine a temporal amount or
degree of overlap or mismatch between the replicated pattern signal
and the baseband echo signal 226. This temporal overlap or mismatch
can represent an additional portion of the time of flight that can
be added to the time of flight calculated from the coarse stage. In
one embodiment, the fine stage examines I and/or Q components of
the baseband echo signal 226 and the replicated pattern signal.
[0068] In the ultrafine stage, the sensing assembly 102 also can
examine the I and/or Q component of the baseband echo signal 226
and the replicated pattern signal to determine a temporal overlap
or mismatch between the I and/or Q components of the baseband echo
signal 226 and the replicated pattern signal. The temporal overlap
or mismatch of the Q components of the baseband echo signal 226 and
the replicated pattern signal may represent an additional time
delay that can be added to the time of flight calculated from the
coarse stage and the fine stage (e.g., by examining the I and/or Q
components) to determine a relatively accurate estimation of the
time of flight. Alternatively or additionally, the ultrafine stage
may be used to precisely track and/or detect movement of the target
object 104 within the bit of interest. The terms "fine" and
"ultrafine" are used to mean that the fine stage may provide a more
accurate and/or precise (e.g., greater resolution) calculation of
the time of flight (t.sub.F) and/or the separation distance 110
relative to the coarse stage and that the ultrafine stage may
provide a more accurate and/or precise (e.g., greater resolution)
calculation of the time of flight (t.sub.F) and/or the separation
distance 110 relative to the fine stage and the coarse stage.
Alternatively or additionally, the time lag of the waveforms in the
I channel and Q channel can be examined to resolve phases of the
echoes in order to calculate separation distance or motion of the
target.
[0069] As described above, the ultrafine stage determination may
involve a similar process as the coarse stage determination. For
example, the coarse stage determination may examine the I channel
of the receive pattern and the data stream to determine correlation
values of different subsets of the data stream and, from those
correlation values, determine a subset of interest and a
corresponding time-of-flight, as described herein. The ultrafine
stage determination can use the I and/or Q channel of the receive
pattern and the data stream to determine correlation values of
different subsets of the data stream and, from those correlation
values, determine a subset of interest and a time-of-flight. The
times-of-flight from the I channel and Q channel can be combined
(e.g., averaged) to calculate a time of flight and/or separation
distance to the target. The correlation values calculated by the
ultrafine stage determination can be used to calculate an
additional time delay that can be added to the time delays from the
coarse stage and/or the fine stage to determine a time of flight
and/or separation distance to the target. Alternatively or
additionally, the correlation values of the waveforms in the I
channel and Q channel can be examined to resolve phases of the
echoes in order to calculate separation distance or motion of the
target.
[0070] The backend 202 can include a first baseband processor 232A
("I Baseband Processor" in FIG. 2) and a second baseband processor
232B ("Q Baseband Processor" in FIG. 2). The first baseband
processor 232A may examine the I component or channel of the echo
signal 226A and the second baseband processor 232B may examine the
Q component or channel of the echo signal 226B. The backend 202 can
provide a measurement signal 234 as an output from the analysis of
the baseband echo signal 226. In one embodiment, the measurement
signal 234 includes an I component or channel measurement signal
234A from the first baseband processor 232A and a Q component or
channel measurement signal 234B from the second baseband processor
232B. The measurement signal 234 may include the separation
distance 110 and/or the time of flight. The total position estimate
260 can be communicated to the control unit 112 (shown in FIG. 1)
so that the control unit 112 can use data or information
representative of the separation distance 110 and/or the time of
flight for one or more other uses, calculations, and the like,
and/or for presentation to an operator on the output device 116
(shown in FIG. 1).
[0071] As described below, a correlation window that also includes
the pattern (e.g., the pulse sequence of bits) or a portion thereof
that was transmitted in the transmitted signal 106 may be compared
to the baseband echo signal 226. The correlation window may be
progressively shifted or delayed from a location in the baseband
echo signal 226 representative of a start of the echo signal 226
(e.g., a time that corresponds to the time at which the transmitted
signal 106 is transmitted, but which may or may not be the exact
beginning of the baseband echo signal) and successively, or in any
other order, compared to different subsets or portions of the
baseband echo signal 226. Correlation values representative of
degrees of match between the pulse sequence in the correlation
window and the subsets or portions of the baseband echo signal 226
can be calculated and a time delay of interest (e.g., approximately
the time of flight) can be determined based on the time difference
between the start of the baseband echo signal 226 and one or more
maximum or relatively large correlation values. The maximum or
relatively large correlation value may represent at least partial
reflection of the transmitted signals 106 off the target object
104, and may be referred to as a correlation value of interest.
[0072] As used herein, the terms "maximum," "minimum," and forms
thereof, are not limited to absolute largest and smallest values,
respectively. For example, while a "maximum" correlation value can
include the largest possible correlation value, the "maximum"
correlation value also can include a correlation value that is
larger than one or more other correlation values, but is not
necessarily the largest possible correlation value that can be
obtained. Similarly, while a "minimum" correlation value can
include the smallest possible correlation value, the "minimum"
correlation value also can include a correlation value that is
smaller than one or more other correlation values, but is not
necessarily the smallest possible correlation value that can be
obtained.
[0073] The time delay of interest can then be used to calculate the
separation distance 110 from the coarse stage. For example, in one
embodiment, the separation distance 110 may be estimated or
calculated as:
d = t F .times. c 2 ( Equation #1 ) ##EQU00001##
where d represents the separation distance 110, t.sub.F represents
the time delay of interest (calculated from the start of the
baseband echo signal 226 to the identification of the correlation
value of interest), and c represents the speed of light.
Alternatively, c may represent the speed at which the transmitted
signals 106 and/or echoes 108 move through the medium or media
between the sensing apparatus 102 and the target object 104. In
another embodiment, the value of t.sub.F and/or c may be modified
by a calibration factor or other factor in order to account for
portions of the delay between transmission of the transmitted
signals 106 and receipt of the echoes 108 that are not due to the
time of flight of the transmitted signals 106 and/or echoes
108.
[0074] With continued reference to the sensing assembly 102 shown
in FIG. 2, FIGS. 3A and 3B are schematic diagrams of a coarse stage
determination of a time of flight for a transmitted signal 106 and
corresponding echo 108 in accordance with one embodiment. By
"coarse," it is meant that one or more additional measurements or
analyses of the same or different echo signal 224 (shown in FIG. 2)
that is generated from the reflected echoes 108 may be performed to
provide a more accurate and/or precise measurement of the time of
flight (t.sub.F) and/or separation distance 110. The use of the
term "coarse" is not intended to mean that the measurement
technique described above is inaccurate or imprecise. As described
above, the pattern generated by the pattern code generator 228 and
the baseband echo signal 226 are received by the RX backend 202B.
The baseband echo signal 226 can be formed by mixing (e.g.,
multiplying) the echo signal 224 by the oscillating signal 216 in
order to translate the echo signal 224 into a baseband signal.
[0075] FIG. 3A illustrates a square waveform transmitted signal 322
representative of the transmitted signal 106 (shown in FIG. 1) and
the digitized echo signal 226. The echo signal 226 shown in FIG. 3A
may represent the I component or channel of the echo signal 226
(e.g., the signal 226A). The signals 322, 226 are shown alongside
horizontal axes 304 representative of time. The transmitted signal
322 includes pattern waveform segments 326 that represent the
pattern that is included in the transmitted signal 106. In the
illustrated embodiment, the pattern waveform segments 326
correspond to a bit pattern of 101011, where 0 represents a low
value 328 of the transmitted signal 322 and 1 represents a high
value 330 of the transmitted signal 322. Each of the low or high
values 328, 330 occurs over a bit time 332. In the illustrated
embodiment, each pattern waveform segment 326 includes six bits
(e.g., six 0s and 1s), such that each pattern waveform segment 326
extends over six bit times 332. Alternatively, one or more of the
pattern waveform segments 326 may include a different sequence of
low or high values 328, 330 and/or occur over a different number of
bit times 332.
[0076] The baseband echo signal 226 includes in one embodiment a
sequence of square waves (e.g., low and high values 328, 330), but
the waves may have other shapes. The echo signal 226 may be
represented as a digital echo signal 740 (shown and described below
in connection with FIG. 3B). As described below, different portions
or subsets of the digital echo signal 740 can be compared to the
pattern sequence of the transmitted signal 106 (e.g., the pattern
waveform segments 326) to determine a time delay of interest, or
estimated time of flight. As shown in FIG. 3A, the square waves
(e.g., low and high values 328, 330) of the baseband echo signal
226 may not exactly line up with the bit times 332 of the
transmitted signal 322.
[0077] FIG. 3B illustrates the digitized echo signal 740 of FIG. 3A
along the axis 304 that is representative of time. As shown in FIG.
3B, the digitized echo signal 740 may be schematically shown as a
sequence of bits 300, 302. Each bit 300, 302 in the digitized echo
signal 740 can represent a different low or high value 328, 330
(shown in FIG. 3A) of the digitized echo signal 740. For example,
the bit 300 (e.g., "0") can represent low values 328 of the
digitized echo signal 740 and the bit 302 (e.g., "1") can represent
high values 330 of the digitized echo signal 740.
[0078] The baseband echo signal 226 begins at a transmission time
(t.sub.0) of the axis 304. The transmission time (t.sub.0) may
correspond to the time at which the transmitted signal 106 is
transmitted by the sensing assembly 102. Alternatively, the
transmission time (t.sub.0) may be another time that occurs prior
to or after the time at which the transmitted signal 106 is
transmitted.
[0079] The baseband processor 232 obtains a receive pattern signal
240 from the pattern generator 228, similar to the transmit pattern
(e.g., in the signal 230) that is included in the transmitted
signal 106, the receive pattern signal 240 may include a waveform
signal representing a sequence of bits, such as a digital pulse
sequence receive pattern 306 shown in FIG. 3. The baseband
processor 232 compares the receive pattern 306 to the echo signal
226. In one embodiment, the receive pattern 306 is a copy of the
transmit pattern of bits that is included in the transmitted signal
106 from the pattern code generator 228, as described above.
Alternatively, the receive pattern 306 may be different from the
transmit pattern that is included in the transmitted signal 106.
For example, the receive pattern 306 may have a different sequence
of bits (e.g., have one or more different waveforms that represent
a different sequence of bits) and/or have a longer or shorter
sequence of bits than the transmit pattern. The receive pattern 306
may be represented by one or more of the pattern waveform segments
326, or a portion thereof, shown in FIG. 3A.
[0080] The baseband processor 232 uses all or a portion of the
receive pattern 306 as a correlation window 320 that is compared to
different portions of the digitized echo signal 740 in order to
calculate correlation values ("CV") at the different positions. The
correlation values represent different degrees of match between the
receive pattern 306 and the digitized echo signal 740 across
different subsets of the bits in the digitized echo signal 740. In
the example illustrated in FIG. 3, the correlation window 320
includes six bits 300, 302. Alternatively, the correlation window
320 may include a different number of bits 300, 302. The correlator
device 731 can temporally shift the correlation window 320 along
the echo signal 740 in order to identify where (e.g., which subset
of the echo signal 226) more closely matches the pattern in the
correlation window 320 more than one or more (or all) of the other
portions of the echo signal 740. In one embodiment, when operating
in the coarse stage determination, the first baseband processor
232A compares the correlation window 320 to the I component or
channel of the echo signal 226.
[0081] For example, the correlator device 731 may compare the bits
in the correlation window 320 to a first subset 308 of the bits
300, 302 in the digitized echo signal 740. For example, the
correlator device 731 can compare the receive pattern 306 with the
first six bits 300, 302 of the digitized echo signal 740.
Alternatively, the correlator device 731 can begin by comparing the
receive pattern 306 with a different subset of the digitized echo
signal 740. The correlator device 731 calculates a first
correlation value for the first subset 308 of bits in the digitized
echo signal 740 by determining how closely the sequence of bits
300, 302 in the first subset 308 match the sequence of bits 300,
302 in the receive pattern 306.
[0082] In one embodiment, the correlator device 731 assigns a first
value (e.g., +1) to those bits 300, 302 in the subset of the
digitized echo signal 740 being compared to the correlation window
320 that match the sequence of bits 300, 302 in the correlation
window 320 and a different, second value (e.g., -1) to those bits
300, 302 in the subset of the digitized echo signal 740 being
examined that do not match the sequence of bits 300, 302 in the
correlation window 320. Alternatively, other values may be used.
The correlator device 731 may then sum these assigned values for
the subset of the digitized echo signal 740 to derive a correlation
value for the subset.
[0083] With respect to the first subset 308 of bits in the
digitized echo signal, only the fourth bit (e.g., zero) and the
fifth bit (e.g., one) match the fourth bit and the fifth bit in the
correlation window 320. The remaining four bits in the first subset
308 do not match the corresponding bits in the correlation window
320. As a result, if +1 is assigned to the matching bits and -1 is
assigned to the mismatching bits, then the correlation value for
the first subset 308 of the digitized echo signal 740 is calculated
to be -2. On the other hand, if +1 is assigned to the bits and 0 is
assigned to the mismatching bits, then the correlation value for
the first subset 308 of the digitized echo signal 740 is calculated
to be +2. As described above, other values may be used instead of
+1 and/or -1.
[0084] The correlator device 731 then shifts the correlation window
320 by comparing the sequence of bits 300, 302 in the correlation
window 320 to another (e.g., later or subsequent) subset of the
digitized echo signal 740. In the illustrated embodiment, the
correlator device 731 compares the correlation window 320 to the
sixth through seventh bits 300, 302 in the digitized echo signal
740 to calculate another correlation value. As shown in FIG. 3, the
subsets to which the correlation window 320 is compared may at
least partially overlap with each other. For example, each of the
subsets to which the correlation window 320 is compared may overlap
with each other by all but one of the bits in each subset. In
another example, each of the subsets may overlap with each other by
a fewer number of the bits in each subset, or even not at all.
[0085] The correlator device 731 may continue to compare the
correlation window 320 to different subsets of the digitized echo
signal 740 to calculate correlation values for the subsets. In
continuing with the above example, the correlator device 731
calculates the correlation values shown in FIG. 3 for the different
subsets of the digitized echo signal 740. In FIG. 3, the
correlation window 320 is shown shifted below the subset to which
the correlation window 320 is compared, with the correlation value
of the subset to which the correlation window 320 is compared shown
to the right of the correlation window 320 (using values of +1 for
matches and -1 for mismatches). As shown in the illustrated
example, the correlation value associated with the fifth through
tenth bits 300, 302 in the digitized echo signal 226 has a
correlation value (e.g., +6) that is larger than one or more other
correlation values of the other subsets, or that is the largest of
the correlation values.
[0086] In another embodiment, the receive pattern 306 that is
included in the correlation window 320 and that is compared to the
subsets of the digitized echo signal 740 may include a portion, and
less than the entirety, of the transmit pattern that is included in
the transmitted signal 106 (shown in FIG. 1). For example, if the
transmit pattern in the transmitted signal 106 includes a waveform
representative of a digital pulse sequence of thirteen (or a
different number) of bits 300, 302, the correlator device 731 may
use a receive pattern 306 that includes less than thirteen (or a
different number) of the bits 300, 302 included in the transmit
pattern.
[0087] In one embodiment, the correlator device 731 can compare
less than the entire receive pattern 306 to the subsets by applying
a mask to the receive pattern 306 to form the correlation window
320 (also referred to as a masked receive pattern). With respect to
the receive pattern 306 shown in FIG. 3, the correlator device 731
may apply a mask comprising the sequence "000111" (or another mask)
to the receive pattern 306 to eliminate the first three bits 300,
302 from the receive pattern 306 such that only the last three bits
300, 302 are compared to the various subsets of the digitized echo
signal 740. The mask may be applied by multiplying each bit in the
mask by the corresponding bit in the receive pattern 306. In one
embodiment, the same mask also is applied to each of the subsets in
the digitized echo signal 740 when the correlation window 320 is
compared to the subsets.
[0088] The correlator 731 may identify a correlation value that is
largest, that is larger than one or more correlation values, and/or
that is larger than a designated threshold as a correlation value
of interest 312. In the illustrated example, the fifth correlation
value (e.g., +6) may be the correlation value of interest 312. The
subset or subsets of bits in the digitized echo signal 740 that
correspond to the correlation value of interest 312 may be
identified as the subset or subsets of interest 314. In the
illustrated example, the subset of interest 314 includes the fifth
through tenth bits 300, 302 in the digitized echo signal 740. In
this example, if the start of the subset of interest is used to
identify the subset of interest then the delay of interest would be
five. Multiple subsets of interest may be identified where the
transmitted signals 106 (shown in FIG. 1) are reflected off of
multiple target objects 104 (shown in FIG. 1), such as different
target objects 104 located different separation distances 110 from
the sensing assembly 102.
[0089] Each of the subsets of the digitized echo signal 740 may be
associated with a time delay (t.sub.d) between the start of the
digitized echo signal 740 (e.g., t.sub.0) and the beginning of the
first bit in each subset of the digitized echo signal 740.
Alternatively, the beginning of the time delay (t.sub.d) for the
subset can be measured from another starting time (e.g., a time
before or after the start of the digitized echo signal 740
(t.sub.0) and/or the end of the time delay (t.sub.d) may be at
another location in the subset, such as the middle or at another
bit of the subset.
[0090] The time delay (t.sub.d) associated with the subset of
interest may represent the time of flight (t.sub.F) of the
transmitted signal 106 that is reflected off a target object 104.
Using Equation #1 above, the time of flight can be used to
calculate the separation distance 110 between the sensing assembly
102 and the target object 104. In one embodiment, the time of
flight (t.sub.F) may be based on a modified time delay (t.sub.d),
such as a time delay that is modified by a calibration factor to
obtain the time of flight (t.sub.F). As one example, the time of
flight (t.sub.F) can be corrected to account for propagation of
signals and/or other processing or analysis. Propagation of the
echo signal 224, formation of the baseband echo signal 226,
propagation of the baseband echo signal 226, and the like, through
the components of the sensing assembly 102 can impact the
calculation of the time of flight (t.sub.F). The time delay
associated with a subset of interest in the baseband echo signal
226 may include the time of flight of the transmitted signals 106
and echoes 108, and also may include the time of propagation of
various signals in the analog and digital blocks (e.g., the
correlator device 731 and/or the pattern code generator 228 and/or
the mixers 210 and/or the amplifier 238) of the system 100.
[0091] In order to determine the propagation time of data and
signals through these components, a calibration routine can be
employed. A measurement can be made to a target of known distance.
For example, one or more transmitted signals 106 can be sent to the
target object 104 that is at a known separation distance 110 from
the transmit and/or receiving antennas 204, 206. The calculation of
the time of flight for the transmitted signals 106 can be made as
described above, and the time of flight can be used to determine a
calculated separation distance 110. Based on the difference between
the actual, known separation distance 110 and the calculated
separation distance 110, a measurement error that is based on the
propagation time through the components of the sensing assembly 102
may be calculated. This propagation time may then be used to
correct (e.g., shorten) further times of flight that are calculated
using the sensing assembly 102.
[0092] In one embodiment, the sensing assembly 102 may transmit
several bursts of the transmitted signal 106 and the correlator
device 731 may calculate several correlation values for the
digitized echo signals 740 that are based on the reflected echoes
108 of the transmitted signals 106. The correlation values for the
several transmitted signals 106 may be grouped by common time
delays (t.sub.d), such as by calculating the average, median, or
other statistical measure of the correlation values calculated for
the same or approximately the same time delays (t.sub.d). The
grouped correlation values that are larger than other correlation
values or that are the largest may be used to more accurately
calculate the time of flight (t.sub.F) and separation distance 110
relative to using only a single correlation value and/or burst.
[0093] FIG. 4 illustrates one example of correlation values that
are calculated and averaged over several transmitted signals 106
shown in FIG. 1. The correlation values 400 are shown alongside a
horizontal axis 402 representative of time (e.g., time delays or
times of flight) and a vertical axis 404 representative of the
magnitude of the correlation values 400. As shown in FIG. 4,
several peaks 406, 408 may be identified based on the multiple
correlation values 400 that are grouped over several transmitted
signals 106. The peaks 406, 408 may be associated with one or more
target objects 104 (shown in FIG. 1) off which the transmitted
signals 106 reflected. The time delays associated with one or more
of the peaks 406, 408 (e.g., the time along the horizontal axis
402) can be used to calculate the separation distance(s) 110 of one
or more of the target objects 104 associated with the peaks 406,
408, as described above.
[0094] FIG. 5 is another schematic diagram of the sensing assembly
102 shown in FIG. 2. The sensing assembly 102 is illustrated in
FIG. 5 as including a radio front end 500 and a processing back end
502. The radio front end 500 may include at least some of the
components included in the front end 200 (shown in FIG. 2) of the
sensing assembly 102 and the processing back end 502 may include at
least some of the components of the back end 202 (shown in FIG. 2)
of the sensing assembly 102, and/or one or more components (e.g.,
the front end transmitter 208 and/or receiver 218 shown in FIG. 2)
of the front end 200.
[0095] As described above, the received echo signal 224 may be
conditioned by circuits 506 (e.g., by the front end receiver 218
shown in FIG. 2) that are used for high-speed optical
communications systems in one embodiment. This conditioning may
include amplification and/or quantization only. The signal 224 may
then pass to a digitizer 730 that creates a digital signal based on
the signal 224, which is then passed to the correlator 731
(described below) for comparison to the original transmit sequence
to extract time-of-flight information. The correlator device 731
and the conditioning circuits may be collectively referred to as
the baseband processing section of the sensing apparatus 102.
[0096] Also as described above, the pattern code generator 228
generates the pattern (e.g., a digital pulse sequence) that is
communicated in the pattern signal 230. The digital pulse sequence
may be relatively high speed in order to make the pulses shorter
and increase accuracy and/or precision of the system 100 (shown in
FIG. 1) and/or to spread the transmitted radio energy over a very
wide band. If the pulses are sufficiently short enough, the
bandwidth may be wide enough to be classified as Ultra-wideband
(UWB). As a result, the system 100 can be operated in the 22-27
GH.sub.Z UWB band and/or the 3-10 GHz UWB band that are available
worldwide (with regional variations) for unlicensed operation.
[0097] In one embodiment, the digital pulse sequence is generated
by one or more digital circuits, such as a relatively low-power
Field-Programmable Gate Array (FPGA) 504. The FPGA 504 may be an
integrated circuit designed to be configured by the customer or
designer after manufacturing to implement a digital or logical
system. As shown in FIG. 5, the FPGA 504 can be configured to
perform the functions of the pulse code generator 228 and the
correlator device 731. The pulse sequence can be buffered and/or
conditioned by one or more circuits 508 and then passed directly to
the transmit radio of the front end 500 (e.g., the front end
transmitter 208).
[0098] FIG. 6 is a schematic diagram of one embodiment of the front
end 200 of the sensing assembly 102 shown in FIG. 2. The front end
200 of the sensing assembly 102 may alternatively be referred to as
the radio front end 500 (shown in FIG. 5) or the "radio" of the
sensing assembly 102. In one embodiment, the front end 200 includes
a direct-conversion transmitter 600 ("TX Chip" in FIG. 6) and
receiver 602 ("RX Chip" in FIG. 6), with a common frequency
reference generator 604 ("VCO Chip" in FIG. 6). The transmitter 600
may include or represent the front end transmitter 208 (shown in
FIG. 2) and the receiver 602 may include or represent the front end
receiver 218 (shown in FIG. 2).
[0099] The common frequency reference generator 604 may be or
include the oscillator device 214 shown in FIG. 2. The common
frequency reference generator 604 may be a voltage-controlled
oscillator (VCO) that produces a frequency reference signal as the
oscillating signal 216. In one embodiment, the frequency of the
reference signal 216 is one half of a designated or desired carrier
frequency of the transmitted signal 106 (shown in FIG. 1).
Alternatively, the reference signal 216 may be another frequency,
such as the same frequency as the carrier frequency, an integer
multiple or divisor of the carrier frequency, and the like.
[0100] In one embodiment, the reference generator 604 emits a
frequency reference signal 216 that is a sinusoidal wave at one
half the frequency of the carrier frequency. The reference signal
is split equally and delivered to the transmitter 600 and the
receiver 602. Although the reference generator 604 may be able to
vary the frequency of the reference signal 216 according to an
input control voltage, the reference generator 604 can be operated
at a fixed control voltage in order to cause the reference
generator 604 to output a fixed frequency reference signal 216.
This is acceptable since frequency coherence between the
transmitter 600 and the receiver 602 may be automatically
maintained. Furthermore, this arrangement can allow for coherence
between the transmitter 600 and the receiver 602 without the need
for a phase locked loop (PLL) or other control structure that may
limit the accuracy and/or speed at which the sensing assembly 102
operates. In another embodiment a PLL may be added to for other
purposes, such as stabilizing the carrier frequency or otherwise
controlling the carrier frequency.
[0101] The reference signal 216 can be split and sent to the
transmitter 600 and receiver 602. The reference signal 216 drives
the transmitter 600 and receiver 602, as described above. The
transmitter 600 may drive (e.g., activate to transmit the
transmitted signal 106 shown in FIG. 1) the transmitting antenna
204 (shown in FIG. 2). The receiver 602 may receive the return echo
signal through the receiving antenna 206 (shown in FIG. 2) that is
separate from the transmitting antenna 204. This can reduce the
need for a T/R (transmit/receive) switch disposed between the
transmitter 600 and the receiver 602. The transmitter 600 can
up-convert the timing reference signal 216 and transmit an RF
transmit signal 606 through the transmitting antenna 204 in order
to drive the transmitting antenna 204 to transmit the transmitted
signal 106 (shown in FIG. 1). In one embodiment, the output of the
transmitter 600 can be at a maximum frequency or a frequency that
is greater than one or more other frequencies in the sensing
assembly 102 (shown in FIG. 1). For example, the transmit signal
606 from the transmitter 600 can be at the carrier frequency. This
transmit signal 606 can be fed directly to the transmitting antenna
204 to minimize or reduce the losses incurred by the transmit
signal 606.
[0102] In one embodiment, the transmitter 600 can take separate
in-phase (I) and quadrature (Q) digital patterns or signals from
the pattern generator 604 and/or the pattern code generator 228
(shown in FIG. 2). This can allow for increased flexibility in the
transmit signal 606 and/or can allow for the transmit signal 606 to
be changed "on the fly," or during transmission of the transmitted
signals 106.
[0103] As described above, the receiver 602 may also receive a copy
of the frequency reference signal 216 from the reference generator
604. The returning echoes 108 (shown in FIG. 1) are received by the
receiving antenna 206 (shown in FIG. 2) and may be fed directly to
the receiver 602 as the echo signal 224. This arrangement can give
the system maximum or increased possible input signal-to-noise
ratio (SNR), since the echo signal 224 propagates a minimal or
relatively small distance before the echo signal 224 enters the
receiver 602. For example, the echo signal 224 may not propagate or
otherwise go through a switch, such as a transmit/receive (TX/RX)
switch.
[0104] The receiver 602 can down-convert a relatively wide block of
frequency spectrum centered on the carrier frequency to produce the
baseband signal (e.g., the baseband echo signal 226 shown in FIG.
2). The baseband signal may then be processed by a baseband analog
section of the sensing assembly 102 (shown in FIG. 1), such as the
correlator device 731 (shown in FIG. 2) and/or one or more other
components, to extract the time of flight (t.sub.F). As described
above, this received echo signal 224 includes a delayed copy of the
TX pattern signal. The delay may be representative of and/or is a
measurement of the round-trip, time-of-flight of the transmitted
signal 106 and the corresponding echo 108.
[0105] The frequency reference signal 216 may contain or comprise
two or more individual signals such as the I and Q components that
are phase shifted relative to each other. The phase shifted signals
can also be generated internally by the transmitter 600 and the
receiver 602. For example, the signal 216 may be generated to
include two or more phase shifted components (e.g., I and Q
components or channels), or may be generated and later modified to
include the two or more phase shifted components.
[0106] In one embodiment, the front end 200 provides relatively
high isolation between the transmit signal 606 and the echo signal
224. This isolation can be achieved in one or more ways. First, the
transmit and receive components (e.g., the transmitter 600 and
receiver 602) can be disposed in physically separate chips,
circuitry, or other hardware. Second, the reference generator 604
can operate at one half the carrier frequency so that feed-through
can be reduced. Third, the transmitter 600 and the receiver 602 can
have dedicated (e.g., separate) antennas 204, 206 that are also
physically isolated from each other. This isolation can allow for
the elimination of a TX/RX switch that may otherwise be included in
the system 100. Avoiding the use of the TX/RX switch also can
remove the switch-over time between the transmitting of the
transmitted signals 106 and the receipt of the echoes 108 shown in
FIG. 1. Reducing the switch-over time can enable the system 100 to
more accurately and/or precisely measure distances to relatively
close target objects 104. For example, reducing this switch-over
time can reduce the threshold distance that may be needed between
the sensing assembly 102 and the target object 104 in order for the
sensing assembly 102 to measure the separation distance 110 shown
in FIG. 1 before transmitted signals 106 are received as echoes
108.
[0107] FIG. 7 is a circuit diagram of one embodiment of a baseband
processing system 232 of the system 100 shown in FIG. 1. In one
embodiment, the baseband processing system 232 is included in the
sensing assembly 102 (shown in FIG. 1) or is separate from the
system 100 but operatively coupled with the system 100 to
communicate one or more signals between the systems 100, 232. For
example, the baseband processing system 232 can be coupled with the
front end receiver 218 (shown in FIG. 2) to receive the echo signal
226 (e.g., the echo signal 226A and/or 226B). For example, at least
part of the system 232 may be disposed between the front end
receiver 218 and the Control and Processing Unit (CPU) 270 shown in
FIG. 7. The baseband processing system 232 may provide for the
coarse and/or fine and/or ultrafine stage determinations described
above.
[0108] In one embodiment, the system 100 (shown in FIG. 1) includes
a fine transmit pattern (e.g., a transmit pattern for fine stage
determination) in the transmitted signal 106 following the coarse
stage determination. For example, after transmitting a first
transmit pattern in a first transmitted signal 106 (or one or more
bursts of several transmitted signals 106) to use the coarse stage
and calculate a time delay in the echo signal 226 (and/or the time
of flight), a second transmit pattern can be included in a
subsequent, second transmitted signal 106 for the fine stage
determination of the time of flight (or a portion thereof). The
transmit pattern in the coarse stage may be the same as the
transmit pattern in the fine stage. Alternatively, the transmit
pattern of the fine stage may differ from the transmit pattern of
the coarse stage, such as by including one or more different
waveforms or bits in a pulse sequence pattern of the transmitted
signal 106.
[0109] The baseband processing system 232 receives the echo signal
226 (e.g., the I component or channel of the echo signal 226A
and/or the Q component or channel of the echo signal 226B from the
front end receiver 218 (shown in FIG. 1). The echo signal 226 that
is received from the front end receiver 218 is referred to as "I or
Q Baseband signal" in FIG. 7. As described below, the system 232
also may receive a receive pattern signal 728 ("I or Q fine
alignment pattern" in FIG. 7) from the pattern code generator 228
(shown in FIG. 2). Although not shown in FIG. 2 or 7, the pattern
code generator 228 and the system 232 may be coupled by one or more
conductive pathways (e.g., busses, wires, cables, and the like) to
communicate with each other. The system 232 can provide output
signals 702A, 702B (collectively or individually referred to as an
output signal 702 and shown as "Digital energy estimates for I or Q
channel" in FIG. 7). In one embodiment, the baseband processing
system 232 is an analog processing system. In another embodiment,
the baseband processing system 232 is a hybrid analog and digital
system comprised of components and signals that are analog and/or
digital in nature.
[0110] The digitized echo signal 226 that is received by the system
232 may be conditioned by signal conditioning components of the
baseband processing system 232, such as by modifying the signals
using a conversion amplifier 704 (e.g., an amplifier that converts
the baseband echo signal 226, such as by converting current into a
voltage signal). In one embodiment, the conversion amplifier 704
includes or represents a trans-impedance amplifier, or "TIA" in
FIG. 7). The signal conditioning components can include a second
amplifier 706 (e.g., a limiting amplifier or "Lim. Amp" in FIG. 7).
The conversion amplifier 704 can operate on a relatively small
input signal that may be a single-ended (e.g., non-differential)
signal to produce a differential signal 708 (that also may be
amplified and/or buffered by the conversion amplifier 704 and/or
one or more other components). This differential signal 708 may
still be relatively small in amplitude. In one embodiment, the
differential signal 708 is then passed to the second amplifier 706
that increases the gain of the differential signal 708.
Alternatively, the second amplifier 706 may not be included in the
system 232 if the conversion amplifier 704 produces a sufficiently
large (e.g., in terms of amplitude and/or energy) output
differential signal 710. The second amplifier 706 can provide
relatively large gain and can tolerate saturated outputs 710. There
may be internal positive feedback in the second amplifier 706 so
that even relatively small input differences in the differential
signal 708 can produce a larger output signal 710. In one
embodiment, the second amplifier 706 quantizes the amplitude of the
received differential signal 708 to produce an output signal
710.
[0111] The second amplifier 706 may be used to determine the sign
of the input differential signal 708 and the times at which the
sign changes from one value to another. For example, the second
amplifier 706 may act as an analog-to-digital converter with only
one bit precision in one embodiment. Alternatively, the second
amplifier 706 may be a high-speed analog-to-digital converter that
periodically samples the differential signal 708 at a relatively
fast rate. Alternatively, the second amplifier may act as an
amplitude quantizer while preserving timing information of the
baseband signal 226. The use of a limiting amplifier as the second
amplifier 706 can provide relatively high gain and relatively large
input dynamic range. As a result, relatively small differential
signals 708 that are supplied to the limiting amplifier can result
in a healthy (e.g., relatively high amplitude and/or
signal-to-noise ratio) output signal 710. Additionally, larger
differential signals 708 (e.g., having relatively high amplitudes
and/or energies) that may otherwise result in another amplifier
being overdriven instead result in a controlled output condition
(e.g., the limiting operation of the limiting amplifier). The
second amplifier 706 may have a relatively fast or no recovery
time, such that the second amplifier 706 may not go into an error
or saturated state and may continue to respond to the differential
signals 708 that are input into the second amplifier 706. When the
input differential signal 708 returns to an acceptable level (e.g.,
lower amplitude and/or energy), the second amplifier 706 may avoid
the time required by other amplifiers for recovery from an
overdrive state (that is caused by the input differential signal
708). The second amplifier 706 may avoid losing incoming input
signals during such a recovery time.
[0112] A switch device 712 ("Switch" in FIG. 7) that receives the
output differential signal 710 (e.g., from the second amplifier
706) can control where the output differential signal 710 is sent.
For example, the switch device 712 may alternate between states
where, in one state (e.g., a coarse acquisition or determination
state), the switch device 712 directs the output differential
signal 710 along a first path 716 to the digitizer 730 and then to
the correlator device 731. The digitizer 730 includes one or more
analog or digital components, such as a processor, controller,
buffers, digital gates, delay lines, samplers and the like, that
digitize received signals into a digital signal, such as the
digital echo signal 740 described above in connection with FIG. 3B.
The first path 716 is used to provide for the coarse stage
determination of the time of flight, as described above. In one
embodiment, the signals 710 may pass through another amplifier 714
and/or one or more other components before reaching the correlator
device 731 for the coarse stage determination. In another state,
the switch device 712 directs the output differential signal 710
along a different, second path 718 to one or more other components
(described below). The second path 718 is used for the fine stage
determination of the time of flight in the illustrated
embodiment.
[0113] The switch device 712 may alternate the direction of flow of
the signals (e.g., the output differential signal 710) from the
first path 716 to the second path 718. Control of the switch device
712 may be provided by the control unit 112 (shown in FIG. 1). For
example, the control unit 112 may communicate control signals to
the switch device 712 to control where the signals flow after
passing through the switch device 712.
[0114] The output differential signals 710 received by the switch
device 712 may be communicated to a comparison device 720 in the
second path 718. Alternatively, the switch device 712 (or another
component) may convert the differential signals 710 into a
single-ended signal that is input into the comparison device 720.
The comparison device 720 also receives the receive pattern signal
728 from the pattern generator 228 (shown in FIG. 2). The receive
pattern signal 728 is referred to as "I or Q fine alignment
pattern" in FIG. 7). The receive pattern signal 728 may include a
copy of the same transmit pattern that is transmitted in the
transmitted signal 106 used to generate the echo signal 226 being
analyzed by the system 232. Alternatively, the receive pattern
signal 728 may differ from the transmit signal that is transmitted
in the transmitted signal 106 used to generate the echo signal 226
being analyzed by the system 232.
[0115] The comparison device 720 compares the signals received from
the switch device 712 with the receive pattern signal 728 to
identify differences between the echo signal 226 and the receive
pattern signal 728.
[0116] In one embodiment, the receive pattern signal 728 includes a
pattern that is delayed by the time delay (e.g., the time of
flight) identified by the coarse stage determination. The
comparison device 720 may then compare this time-delayed pattern in
the pattern signal 728 to the echo signal 226 (e.g., as modified by
the amplifiers 704, 710) to identify overlaps or mismatches between
the time-delayed pattern signal 728 and the echo signal 226.
[0117] In one embodiment, the comparison device 720 may include or
represent a limiting amplifier that acts as a relatively high-speed
XOR gate. An "XOR gate" includes a device that receives two signals
and produces a first output signal (e.g., a "high" signal) when the
two signals are different and a second output signal (e.g., a "low"
signal) or no signal when the two signals are not different.
[0118] In another embodiment, the system may only include the
coarse baseband processing circuits 716 or the fine baseband
processing circuits 718. In this case, the switch 712 may also be
eliminated. For example, this may be to reduce the cost or
complexity of the overall system. As another example, the system
may not need the fine accuracy and the rapid response of the coarse
section 716 is desired. The coarse, fine and ultrafine stages may
be used in any combination at different times in order to balance
various performance metrics. Intelligent control can be manually
provided by an operator or automatically generated by a processor
or controller (such as the control unit 112) autonomously
controlling the assembly 102 based on one or more sets of
instructions (such as software modules or programs) stored on a
tangible computer readable storage medium (such as a computer
memory). The intelligent control can manually or automatically
switch between which stages are used and/or when based on feedback
from one or more other stages. For example, based on the
determination from the coarse stage (e.g., an estimated time of
flight or separation distance), the sensing assembly 102 may
manually or automatically switch to the fine and/or ultrafine stage
to further refine the time of flight or separation distance and/or
to monitor movement of the target object 104.
[0119] With continued reference to FIG. 7, FIG. 8 is a schematic
diagram of one example of how the comparison device 720 compares a
portion 800 of the baseband echo signal 226 with a portion 802 of
the time-delayed pattern signal 728 in one embodiment. Although
only portions 800, 802 of the pattern signal 728 and the echo
signal 226 are shown, the comparison device 720 may compare more,
or all, of the echo signal 226 with the pattern signal 728. The
portion 800 of the echo signal 226 and the portion 802 of the
pattern signal 728 are shown disposed above each other and above a
horizontal axis 804 that is representative of time. An output
signal 806 represents the signal that is output from the comparison
device 720. The output signal 806 represents differences (e.g., a
time lag, amount of overlap, or other measure) between the portion
800 of the echo signal 226 and the portion 802 of the pattern
signal 728. The comparison device 720 may output a single ended
output signal 806 or a differential signal as the output signal 806
(having components 806A and 806B, as shown in FIG. 8).
[0120] In one embodiment, the comparison device 720 generates the
output signal 806 based on differences between the portion 800 of
the echo signal 226 and the portion 802 of the time-delayed pattern
signal 728. For example, when a magnitude or amplitude of both
portions 800, 802 is "high" (e.g., has a positive value) or when
the magnitude or amplitude of both portions 800, 802 is "low"
(e.g., has a zero or negative value), the comparison device 720 may
generate the output signal 806 to have a first value. In the
illustrated example, this first value is zero. When a magnitude or
amplitude of both portions 800, 802 differ (e.g., one has a high
value and the other has a zero or low value), the comparison device
720 may generate the output signal 806 with a second value, such as
a high value.
[0121] In the example of FIG. 8, the portion 800 of the echo signal
226 and the portion 802 of the pattern signal 728 have the same or
similar value except for time periods 808, 810. During these time
periods 808, 810, the comparison device 720 generates the output
signal 806 to have a "high" value. Each of these time periods 808,
810 can represent the time lag, or delay, between the portions 800,
802. During other time periods, the comparison device 720 generates
the output signal 806 to have a different value, such as a "low" or
zero value, as shown in FIG. 8. Similar output signals 806 may be
generated for other portions of the echo signal 226 and pattern
signal 728.
[0122] FIG. 9 illustrates another example of how the comparison
device 720 compares a portion 900 of the baseband echo signal 226
with a portion 902 of the pattern signal 728. The portions 900, 902
have the same or similar values except for time periods 904, 906.
During these time periods 904, 906, the comparison device 720
generates the output signal 806 to have a "high" value. During
other time periods, the comparison device 720 generates the output
signal 806 to have a different value, such as a "low" or zero
value. As described above, the comparison device 720 may compare
additional portions of the baseband signal 226 with the pattern
signal 728 to generate additional portions or waveforms in the
output signal 806.
[0123] FIG. 10 illustrates another example of how the comparison
device 720 compares a portion 1000 of the baseband echo signal 226
with a portion 1002 of the pattern signal 230. The portions 1000,
1002 have the same or similar values over the time shown in FIG.
10. As a result, the output signal 806 that is generated by the
comparison device 720 does not include any "high" values that
represent differences in the portions 1000, 1002. As described
above, the comparison device 720 may compare additional portions of
the baseband signal 226 with the pattern signal 728 to generate
additional portions or waveforms in the output signal 806. The
output signals 806 shown in FIGS. 8, 9, and 10 are provided merely
as examples and are not intended to be limitations on all
embodiments disclosed herein.
[0124] The output signals 806 generated by the comparison device
720 represent temporal misalignment between the baseband echo
signal 226 and the pattern signal 728 that is delayed by the time
of flight or time delay measured by the coarse stage determination.
The temporal misalignment may be an additional portion (e.g., to be
added to) the time of flight of the transmitted signals 106 (shown
in FIG. 1) and the echoes 108 (shown in FIG. 1) to determine the
separation distance 110 (shown in FIG. 1).
[0125] The temporal misalignment between the baseband signal 226
and the pattern signal 728 may be referred to as a time lag. The
time lag can be represented by the time periods 808, 810, 904, 906.
For example, the time lag of the data stream 226 in FIG. 8 may be
the time encompassed by the time period 808 or 810, or the time by
which the portion 802 of the baseband signal 226 follows behind
(e.g., lags) the portion 800 of the pattern signal 728. Similarly,
the time lag of the portion 902 of the baseband signal 226 may be
the time period 904 or 906. With respect to the example shown in
FIG. 10, the portion 1000 of the baseband signal does not lag
behind the portion 1002 of the pattern signal 728. As described
above, several time lags may be measured by comparing more of the
baseband signal 226 with the time-delayed pattern signal 728.
[0126] In order to measure the temporal misalignment between the
baseband signal 226 and the time-delayed pattern signal, the output
signals 806 may be communicated from the conversion device 720 to
one or more filters 722. In one embodiment, the filters 722 are
low-pass filters. The filters 722 generate energy signals 724 that
are proportional to the energy of the output signals 806. The
energy of the output signals 806 is represented by the size (e.g.,
width) of waveforms 812, 910 in the output signals 806. As the
temporal misalignment between the baseband signal 226 and the
pattern signal 728 increases, the size (and energy) of the
waveforms 812, 910 increases. As a result, the amplitude and/or
energy conveyed or communicated by the energy signals 724
increases. Conversely, as the temporal misalignment between the
baseband signal 226 and the time-delayed pattern signal 728
decreases, the size and/or amplitude and/or energy of the waveforms
812, 910 also decreases. As a result, the energy conveyed or
communicated by the energy signals 724 decreases.
[0127] As another example, the above system could be implemented
using the opposite polarity, such as with an XNOR comparison device
that produces "high" signals when the baseband signal 226 and the
time-delayed pattern signal 728 are the same and "low" when they
are different. In this example, as the temporal misalignment
between the baseband signal 226 and the pattern signal 728
increases, the size (and energy) of the waveforms 812, 910
decreases. As a result, the amplitude and/or energy conveyed or
communicated by the energy signals 724 decreases. Conversely, as
the temporal misalignment between the baseband signal 226 and the
time-delayed pattern signal 728 decreases, the size, amplitude,
and/or energy of the waveforms 812, 910 also increases. As a
result, the energy conveyed or communicated by the energy signals
724 increases.
[0128] The energy signals 724 may be communicated to measurement
devices 726 ("ADC" in FIG. 7). The measurement devices 726 can
measure the energies of the energy signals 724. The measured
energies can then be used to determine the additional portion of
the time of flight that is represented by the temporal misalignment
between the baseband signal 226 and the time-delayed pattern signal
728. In one embodiment, the measurement device 726 periodically
samples the energy and/or amplitude of energy signals 724 in order
to measure the energies of the energy signals 724. For example, the
measurement devices 726 may include or represent analog-to-digital
converters (ADC) that sample the amplitude and/or energy of the
energy signals 724 in order to measure or estimate the alignment
(or misalignment) between the echo signal 226 and the pattern
signal 728. The sampled energies can be communicated by the
measurement devices 726 as the output signal 702 to the control
unit 112 or other output device or component (shown as "Digital
energy estimates for I or Q channel" in FIG. 7).
[0129] The control unit 112 (or other component that receives the
output signal 710) may examine the measured energy of the energy
signals 724 and calculate the additional portion of the time of
flight represented by the temporal misalignment between the
baseband signal 226 and the time-delayed pattern signal 728. The
control unit 112 also may calculate the additional portion of the
separation distance 110 that is associated with the temporal
misalignment. In one embodiment, the control unit 112 compares the
measured energy to one or more energy thresholds. The different
energy thresholds may be associated with different amounts of
temporal misalignment. Based on the comparison, a temporal
misalignment can be identified and added to the time of flight
calculated using the coarse stage determination described above.
The separation distance 110 may then be calculated based on the
combination of the coarse stage determination of the time of flight
and the additional portion of the time of flight from the fine
stage determination.
[0130] FIG. 11 illustrates examples of output signals 724 provided
to the measurement devices 726 and energy thresholds used by the
control unit 112 or other component or device (shown in FIG. 2) in
accordance with one example. The output signals 702 are shown
alongside a horizontal axis 1102 representative of time and a
vertical axis 1104 representative of energy. Several energy
thresholds 1106 are shown above the horizontal axis 1102. Although
eight output signals 724A-H and eight energy thresholds 1106A-H are
shown, alternatively, a different number of output signals 724
and/or energy thresholds 1106 may be used.
[0131] The measurement devices 726 may digitize the energy signals
724 to produce the energy data output signals 702. When the output
signals 702 are received from the measurement devices 726 (shown in
FIG. 7) by the CPU 270, the output signals 706 can be compared to
the energy thresholds 1106 to determine which, if any, of the
energy thresholds 1106 are exceeded by the output signals 702. For
example, the output signals 702 having less energy (e.g., a lower
magnitude) than the energies associated with the output signal 702A
may not exceed any of the thresholds 1106, while the output signal
702A approaches or reaches the threshold 1106A. The output signal
702B is determined to exceed the threshold 1106A, but not exceed
the threshold 1106B. As shown in FIG. 11, other output signals 702
may exceed some thresholds 1106 while not exceeding other
thresholds 1106.
[0132] The different energy thresholds 1106 are associated with
different temporal misalignments between the echo signal 226 and
the time-delayed pattern signal 728 in one embodiment. For example,
the energy threshold 1106A may represent a temporal misalignment of
100 picoseconds, the energy threshold 1106B may represent a
temporal misalignment of 150 picoseconds, the energy threshold
1106C may represent a temporal misalignment of 200 picoseconds, the
energy threshold 1106D may represent a temporal misalignment of 250
picoseconds, and so on. For example, 724B may be the result of the
situation shown in FIGS. 8 and 724E may be the result of the
situation in FIG. 9.
[0133] The measured energy of the output signal 702 can be compared
to the thresholds 1106 to determine if the measured energy exceeds
one or more of the thresholds 1106. The temporal misalignment
associated with the largest threshold 1106 that is approached or
reached or represented by the energy of the output signal 702 may
be identified as the temporal misalignment between the echo signal
226 and the time-delayed pattern signal 728. In one embodiment, no
temporal alignment may be identified for output signals 702 having
or representing energies that are less than the threshold
1106A.
[0134] The energy thresholds 1106 may be established by positioning
target objects 104 (shown in FIG. 1) a known separation distance
110 (shown in FIG. 1) from the sensing assembly 102 (shown in FIG.
1) and observing the levels of energy that are represented or
reached or approached by the output signals 702.
[0135] In addition or as an alternate to performing the fine stage
determination of the time of flight, the ultrafine stage may be
used to refine (e.g., increase the resolution of) the time of
flight measurement, track movement, and/or detect movement of the
target object 104 (shown in FIG. 1). In one embodiment, the
ultrafine stage includes comparing different components or channels
of the same or different echo signals 226 as the fine stage
determination. For example, in one embodiment, the coarse stage
determination may measure a time of flight from echo signals 226
that are based on echoes 108 received from transmission of a first
set or burst of one or more transmitted signals 106, as described
above. The fine stage determination may measure an amount of
temporal misalignment or overlap between echo signals 226 that are
based on echoes 108 received from transmission of a subsequent,
second set or burst of one or more transmitted signals 106 (that
may use the same or different transmit pattern as the first set or
burst of transmitted signals 106). The fine stage determination may
measure the temporal misalignment between the echo signals 226 from
the second set or burst of transmitted signals 106 and a receive
pattern signal (which may be the same or different receive pattern
as used by the coarse stage determination) as that is time delayed
by the time of flight measured by the coarse stage, as described
above. In one embodiment, the fine stage determination examines the
I and/or Q component or channel of the echo signals 226. The
ultrafine stage determination may measure the temporal misalignment
of the echo signals 226 from the same second set or burst of
transmitted signals 106 as the fine stage determination, or from a
subsequent third set or burst of transmitted signals 106. The
ultrafine stage determination may measure the temporal misalignment
between the echo signals 226 and a receive pattern signal (that is
the same or different as the receive pattern signal used by the
fine stage determination) that is time-delayed by the time of
flight measured by the coarse stage. In one embodiment, the
ultrafine stage measures the temporal misalignment of the I and/or
Q component or channel of the echo signals 226 while the fine stage
measures the temporal misalignment of the Q and/or I component or
channel of the same or different echo signals 226. The temporal
misalignment of the I component may be communicated to the control
unit 112 (or other component or device) as the output signals 702
(as described above) while the temporal misalignment of the Q
component may be communicated to the control unit 112 (or other
component or device) as output signals 1228. Alternatively or
additionally, the time lag of the waveforms in the I channel and Q
channel can be examined to resolve phases of the echoes in order to
calculate separation distance or motion of the target.
[0136] As described above, the ultrafine stage determination may
alternatively or additionally involve a similar process as the
coarse stage determination. For example, the coarse stage
determination may examine the I channel of the receive pattern and
the data stream to determine correlation values of different
subsets of the data stream and, from those correlation values,
determine a subset of interest and a corresponding time-of-flight,
as described herein. The ultrafine stage determination can use the
Q channel of the receive pattern and the data stream to determine
correlation values of different subsets of the data stream and,
from those correlation values, determine a subset of interest and a
time-of-flight. The times-of-flight from the I channel and Q
channel can be combined (e.g., averaged) to calculate a time of
flight and/or separation distance to the target. The correlation
values calculated by the ultrafine stage determination can be used
to calculate an additional time delay that can be added to the time
delays from the coarse stage and/or the fine stage to determine a
time of flight and/or separation distance to the target.
Alternatively or additionally, the correlation values of the
waveforms in the I channel and Q channel can be examined to resolve
phases of the echoes in order to calculate separation distance or
motion of the target.
[0137] FIG. 12 is a circuit diagram of another embodiment of a
baseband processing system 1200 of the system 100 shown in FIG. 1.
In one embodiment, the baseband processing system 1200 is similar
to the baseband processing system 232 (shown in FIG. 7). For
example, the baseband processing system 1200 may be included in the
sensing assembly 102 (shown in FIG. 1) by being coupled with the
front end receiver 218, the pattern code generator 228, and/or the
baseband processor 232 of the sensing assembly 102. The baseband
processing system 1200 includes two or more parallel paths 1202,
1204 that the I and Q components of the baseband echo signal 226
and the pattern signal can flow through for processing and
analysis. For example, a first path 1202 can process and analyze
the I components of the echo signal 224 and baseband echo signal
226 and the second path 1204 can process and analyze the Q
components of the echo signal 224 and the baseband echo signal 226.
In the illustrated embodiment, each of the paths 1202, 1204
includes the baseband processing system 232 described above.
Alternatively, one or more of the paths 1202, 1204 may include one
or more other components for processing and/or analyzing the
signals. In another embodiment, only a single path 1202 or 1204 may
process and/or analyze multiple, different components of the
baseband echo signal 224 and/or baseband echo signal 226. For
example, the path 1202 may examine the I component of the signal
224 and/or 226 during a first time period and then examine the Q
component of the signal 224 and/or 226 during a different (e.g.,
subsequent or preceding) second time period.
[0138] In operation, the echo signal 224 is received by the front
end receiver 218 and is separated into separate I and Q signals
1206, 1208 (also referred to herein as I and Q channels). Each
separate I and Q signal 1206, 1208 includes the corresponding I or
Q component of the echo signal 224 and can be processed and
analyzed similar to the signals described above in connection with
the baseband processing system 232 shown in FIG. 7. For example,
each of the I signal 1206 and the Q signal 1208 can be received
and/or amplified by a conversion amplifier 1210 (that is similar to
the conversion amplifier 704) in each path 1202, 1204 to output a
differential signal (e.g., similar to the signal 708 shown in FIG.
7) to another amplifier 1212 (e.g., similar to the amplifier 706
shown in FIG. 7). The amplifiers 1212 can produce signals having
increased gain (e.g., similar to the signals 710 shown in FIG. 7)
that are provided to switch devices 1214. The switch devices 1214
can be similar to the switch device 712 (shown in FIG. 7) and can
communicate the signals from the amplifiers 1212 to amplifiers 1216
(which may be similar to the amplifier 714 shown in FIG. 7) and/or
the correlator device 232 for the coarse stage identification of a
time of flight, as described above.
[0139] Similar to as described above in connection with the switch
device 712 (shown in FIG. 7), the switch devices 1214 can direct
the signals from the amplifiers 1212 to comparison devices 1218
(that may be similar to the comparison device 720 shown in FIG. 7),
filters 1220 (that may be similar to the filters 722 shown in FIG.
7), and measurement devices 1222 (that may be similar to the
measurement devices 726 shown in FIG. 7). The comparison devices
1218 may each receive different components of a receive pattern
signal from the pattern code generator 228. For example, the
comparison device 1218 in the first path 1202 may receive an I
component 1224 of a receive pattern signal for the fine stage and
the comparison device 1218 in the second path 1202 may receive the
Q component 1226 of the receive pattern signal for the ultrafine
stage. The comparison devices 1218 generate output signals that
represent temporal misalignments between the I or Q components
1224, 1226 of the receive pattern signal and the I or Q components
of the echo signal 226, similar to as described above. For example,
the comparison device 1218 in the first path 1202 may output a
signal having an energy that represents (e.g., is proportional to)
the temporal misalignment between the I component of the baseband
echo signal 226 and the I component of the time-delayed receive
pattern signal 728. The comparison device 1218 in the second path
1204 may output another signal having an energy that represents the
temporal misalignment between the Q component of the baseband echo
signal 226 and the Q component of the time-delayed pattern signal
728. Alternatively, there may be a single path 700, as shown in
FIG. 7, that may be shared between I and Q operation. This could be
accomplished by alternately providing or switching between the I
and Q components of the baseband echo signal 226A ad 226B.
[0140] As described above, the energies of the signals output from
the comparison devices 1218 can pass through the filters 1220 and
be measured by the measurement devices 1222 to determine each of
the temporal misalignments associated with the I and Q components
of the echo signal 226 and the receive pattern signal. These
temporal misalignments can be added together and added to the time
of flight determined by the coarse stage determination. The sum of
the temporal misalignments and the time of flight from the coarse
stage determination can be used by the baseband processor 232 to
calculate the separation distance 110 (shown in FIG. 1), as
described above. Because the I and Q components of the echo signal
and the time-delayed receive pattern signal are phase shifted by
approximately 90 degrees from each other, separately examining the
I and Q components allows calculation of the carrier phase of the
returning signal 108 according to Equation 2 below and can provide
resolution on the order of one eighth or better (smaller) of the
wavelength of the carrier signal of the transmitted signals 106 and
echoes 108. Alternatively, there may be 3 or more components
separated by an amount other than 90 degrees.
[0141] In one embodiment, the ultrafine stage determination
described above can be used to determine relatively small movements
that change the separation distance 110 (shown in FIG. 1). For
example, the ultrafine stage may be used to identify relatively
small movements within a portion of the separation distance 110
that is associated with the subset of interest in the baseband echo
signal 226.
[0142] FIG. 13 illustrates projections of I and Q components of the
baseband echo signal 226 in accordance with one embodiment. The
ultrafine stage determination can include the baseband processor
232 (shown in FIG. 2) projecting a characteristic of the I and Q
components of the baseband echo signal 226 onto a vector. As shown
in FIG. 13, a vector 1300 is shown alongside a horizontal axis 1302
and a vertical axis 1304. The backend 202 or control unit 112 or
other processing or computation devices by examination of the data
signals 234, 702, 1228, 260, or others or a combination of some or
all of the signals may determine the vector 1300 as a projection of
the characteristic (e.g., amplitude) of the I component 1320 of the
echo signal along the horizontal axis 1302 and a projection of the
characteristic (e.g., amplitude) of the Q component 1321 of the
echo signal along the vertical axis 1304. For example, the vector
1300 may extend to a location along the horizontal axis 1302 by an
amount that is representative of an amplitude of the I component of
the echo signal and to a location along the vertical axis 1304 by
an amount that is representative of an amplitude of the Q component
of the echo signal. The phase of the carrier can then calculated
as:
.PHI. = arctan ( I Q ) ( Equation #2 ) ##EQU00002##
where .PHI. denotes the phase and I is the I projection 1320 and Q
is the Q projection 1321. The carrier phase or the change in
carrier phase can be used to calculate the distance or change in
distance through the equation:
distance = .PHI. .times. .lamda. 360 ( Equation #3 )
##EQU00003##
where .lamda., is the wavelength of the carrier frequency and y is
the phase expressed in degrees as calculated from Equation 2
above.
[0143] The baseband processor 232 (shown in FIG. 2) may then
determine additional vectors 1306, 1308 based on the echoes 108
(shown in FIG. 1) received from additional transmitted signals 106
(shown in FIG. 1). Based on changes in the vector 1300 to the
vector 1306 or the vector 1308, the baseband processor 232 may
identify movement of the target object 104 (shown in FIG. 1) within
the portion of the separation distance 110 (shown in FIG. 1) that
is associated with the subset of interest. For example, rotation of
the vector 1300 in a counter-clockwise direction 1310 toward the
location of the vector 1306 may represent movement of the target
object 104 toward the sensing assembly 102 shown in FIG. 1 (or
movement of the sensing assembly 102 toward the target object 104).
Rotation of the vector 1300 in a clockwise direction 1312 toward
the location of the vector 1308 may represent movement of the
target object 104 away from the sensing assembly 102 (or movement
of the sensing assembly 102 toward the target object 104).
Alternatively, movement of the vector 1300 in the counter-clockwise
direction 1310 may represent movement of the target object 104 away
from the sensing assembly 102 (or movement of the sensing assembly
102 toward the target object 104) while movement of the vector 1300
in the clockwise direction 1312 may represent movement of the
target object 104 toward the sensing assembly 102 shown in FIG. 1
(or movement of the sensing assembly 102 toward the target object
104). The correlator device 232 may be calibrated by moving the
target object 104 toward and away from the sensing assembly 102 to
determine which direction of movement results in rotation of the
vector 1300 in the clockwise direction 1312 or counter-clockwise
direction 1310.
[0144] The coarse, fine, and/or ultrafine stage determinations
described above may be used in a variety of combinations. For
example, the coarse stage determination may be used to calculate
the separation distance 110 (shown in FIG. 1), even if the
approximate distance from the sensing device 102 (shown in FIG. 1)
to the target object 104 (shown in FIG. 1) is not known.
Alternatively, the coarse stage may be used with the fine and/or
ultrafine stage determinations to obtain a more precise calculation
of the separation distance 110. The coarse, fine and ultrafine
stages may be used in any combination at different times in order
to balance various performance metrics.
[0145] As another example, if the separation distance 110 (shown in
FIG. 1) is known, the fine or ultrafine stage determinations can be
activated without the need for first identifying the bit of
interest using the coarse stage determination. For example, the
system 100 (shown in FIG. 1) may be in a "tracking" mode where
updates from the initial known separation distance 110 are
identified and/or recorded using the fine and/or ultrafine state
determinations.
[0146] Returning to the discussion of the system 100 shown in FIG.
1, in another embodiment, the system 100 discern between echoes 108
that are reflected off of different target objects 104. For
example, in some uses of the system 100, the transmitted signals
106 may reflect off of multiple target objects 104. If the target
objects 104 are located different separation distances 110 from the
sensing assembly 102, a single baseband echo signal 226 (shown in
FIG. 2) may represent several sequences of bits that represent
echoes off the different target objects 104. As described below, a
mask may be applied to the baseband echo signal 226 and the pattern
in the correlation window that is compared to the baseband echo
signal 226 in order to distinguish between the different target
objects 104.
[0147] FIG. 14 illustrates a technique for distinguishing between
echoes 108 (shown in FIG. 1) that are reflected off different
target objects 104 (shown in FIG. 1) in accordance with one
embodiment. When a first transmitted signal 106 shown in FIG. 1 (or
a series of first transmitted signals 106) reflect off of multiple
target objects 104, the digital pulse sequence (e.g., the pattern
of bits) in the pattern signal 230 (shown in FIG. 2) may be
modified relative to the digital pulse sequence in the first
transmitted signal 106 for transmission of a second transmitted
signal 106 (or series of second transmitted signals 106). The
echoes 108 and corresponding baseband echo signal 226 (shown in
FIG. 2) of the second transmitted signal 106 may be compared to the
modified digital pulse sequence to distinguish between the multiple
target objects 104 (e.g., to calculate different times of flight
and/or separation distances 110 associated with the different
target objects 104).
[0148] A first digitized echo signal 1400 in FIG. 14 represents the
sequence of bits that may be generated when a transmitted signal
106 (shown in FIG. 1) reflects off a first target object 104 at a
first separation distance 110 (shown in FIG. 1) from the sensing
assembly 102 (shown in FIG. 1). A second digitized echo signal 1402
represents the sequence of bits that may be generated when the
transmitted signal 106 reflects off a different, second target
object 104 that is a different, second separation distance 110 from
the sensing assembly 102. Instead of separately generating the
digitized echo signals 1400, 1402, the sensing assembly 102 may
generate a combined digitized echo signal 1404 that represents the
combination of echoes 108 off the different target objects 104. The
combined digitized echo signal 1404 may represent a combination of
the digitized echo signals 1400, 1402.
[0149] A correlation window 1406 includes a sequence 1414 of bits
that can be compared to either digitized echo signal 1400, 1402 to
determine a subset of interest, such as the subsets of interest
1408, 1410, in order to determine times of flight to the respective
target objects 104 (shown in FIG. 1), as described above. However,
when the echoes 108 (shown in FIG. 1) off the target objects 104
are combined and the combined digitized echo signal 1404 is
generated, the correlation window 1406 may be less accurate or
unable to determine the time of flight to one or more of the
several target objects 104. For example, while separate comparison
of the correlation window 1406 to each of the digitized echo
signals 1400, 1402 may result in correlation values of +6 being
calculated for the subsets of interest 1408, 1410, comparison of
the correlation window 1406 to the combined digitized echo signal
1404 may result in correlation values of +5, +4, and +4 for the
subsets that include the first through sixth bits, the third
through eighth bits, and the seventh through twelfth bits in the
combined digitized echo signal 1404. As a result, the baseband
processor 232 (shown in FIG. 2) may be unable to distinguish
between the different target objects 104 (shown in FIG. 1).
[0150] In one embodiment, a mask 1412 can be applied to the
sequence 1414 of bits in the correlation window 1406 to modify the
sequence 1414 of bits in the correlation window 1406. The mask 1412
can eliminate or otherwise change the value of one or more of the
bits in the correlation window 1406. The mask 1412 can include a
sequence 1416 of bits that are applied to the correlation window
1406 (e.g., by multiplying the values of the bits) to create a
modified correlation window 1418 having a sequence 1420 of bits
that differs from the sequence 1414 of bits in the correlation
window 1406. In the illustrated example, the mask 1412 includes a
first portion of the first three bits ("101") and a second portion
of the last three bits ("000"). Alternatively, another mask 1412
may be used that has a different sequence of bits and/or a
different length of the sequence of bits. Applying the mask 1412 to
the correlation window 1406 eliminates the last three bits ("011")
in the sequence 1414 of bits in the correlation window 1406. As a
result, the sequence 1420 of bits in the modified correlation
window 1418 includes only the first three bits ("101") of the
correlation window 1418. In another embodiment, the mask 1412 adds
additional bits to the correlation window 1406 and/or changes
values of the bits in the correlation window 1406.
[0151] The sequence 1420 of bits in the modified correlation window
1418 can be used to change the sequence of bits in the pattern
signal 230 (shown in FIG. 2) that is communicated to the
transmitter for inclusion in the transmitted signals 106 (shown in
FIG. 1). For example, after receiving the combined digitized echo
signal 1404 and being unable to discern between the different
target objects 104 (shown in FIG. 1), the sequence of bits in the
pattern that is transmitted toward the target objects 104 can be
changed to include the sequence 1420 of bits in the modified
correlation window 1412 or some other sequence of bits to aid in
the discernment of the different target objects 104. An additional
combined digitized echo signal 1422 may be received based on the
echoes 108 of the transmitted signals 106 that include the sequence
1420 of bits.
[0152] The modified correlation window 1418 can then be compared
with the additional digitized echo signal 1422 to identify subsets
of interest associated with the different target objects 104 (shown
in FIG. 1). In the illustrated embodiment, the modified correlation
window 1418 can be compared to different subsets of the digitized
echo signal 1422 to identify first and second subsets of interest
1424, 1426, as described above. For example, the first and second
subsets of interest 1424, 1426 may be identified as having higher
or the highest correlation values relative to other subsets of the
digitized echo signal 1422.
[0153] In operation, when transmitted signals 106 reflect off
multiple target objects 104, the pattern transmitted in the signals
106 can be modified relatively quickly between successive bursts of
the transmitted signals 106 when one or more of the target objects
104 cannot be identified from examination of the digitized echo
signal 226. The modified pattern can then be used to distinguish
between the target objects 104 in the digitized echo signal 740
using the correlation window that includes the modified
pattern.
[0154] In another embodiment, the digital pulse sequence of bits
included in a transmitted signal 106 (shown in FIG. 1) may be
different from the digital pulse sequence of bits included in the
correlation window and compared to the baseband echo signal 226
(shown in FIG. 2). For example, the pattern code generator 228
(shown in FIG. 2) may create heterogeneous patterns and communicate
the heterogeneous patterns in the pattern signals 230 (shown in
FIG. 2) to the transmitter 208 and the baseband processor 232. The
transmitter 208 can mix a first pattern of bits in the transmitted
signal 106 and the baseband processor 232 can compare a different,
second pattern of bits to the baseband echo signal 226 that is
generated based on echoes 108 (shown in FIG. 1) of the transmitted
signals 106. With respect to the example described above in
connection with FIG. 14, the sequence 1414 of bits in the
correlation window 1406 can be included in the transmitted signals
106 while the sequence 1416 of bits in the mask 1412 or the
sequence 1420 of bits in the modified correlation window 1418 can
be compared to the digitized echo signal 1422. Using different
patterns in this manner can allow for the sensing assembly 102
(shown in FIG. 1) to distinguish between multiple target objects
104, as described above. Using different patterns in this manner
can additionally allow for the sensing assembly 102 (shown in FIG.
1) to perform other functions including, but not limited to clutter
mitigation, signal-to-noise improvement, anti-jamming,
anti-spoofing, anti-eavesdropping, and others.
[0155] FIG. 15 is a schematic view of an antenna 1500 in accordance
with one embodiment. The antenna 1500 may be used as the
transmitting antenna 204 and/or the receiving antenna 206, both of
which are shown in FIG. 2. Alternatively, another antenna may be
used for the transmitting antenna 204 and/or the receiving antenna
206. The antenna 1500 includes a multi-dimensional (e.g., two
dimensional) array 1502 of antenna unit cells 1504. The unit cells
1504 may represent or include microstrip patch antennas.
Alternatively, the unit cells 1504 may represent another type of
antenna. Several unit cells 1504 can be conductively coupled in
series with each other to form a series-fed array 1506. In the
illustrated embodiment, the unit cells 1504 are connected in a
linear series. Alternatively, the unit cells 1504 can be connected
in another shape.
[0156] Several series-fed arrays 1506 are conductively coupled in
parallel to form the array 1502 in the illustrated embodiment. The
numbers of unit cells 1504 and series-fed arrays 1506 shown in FIG.
15 are provided as examples. A different number of unit cells 1504
and/or arrays 1506 may be included in the antenna 1500. The antenna
1500 may use the several unit cells 1504 to focus the energy of the
transmitted signals 106 (shown in FIG. 1) through constructive
and/or destructive interference.
[0157] FIG. 16 is a schematic diagram of one embodiment of the
front end 200 of the sensing assembly 102 (shown in FIG. 1). The
antennas 1500 may be used as the transmitting antenna 204 and the
receiving antenna 206, as shown in FIG. 16. Each antenna 1500 may
be directly connected to the receiver 602 or transmitter 600 (e.g.,
with no other components disposed between the antenna 1500 and the
receiver 602 or transmitter 600) by a relatively short length of
transmission line 1600.
[0158] The front end 200 of the sensing assembly 102 may be housed
in an enclosure 1602, such as a metal or otherwise conductive
housing, with radio transmissive windows 1604 over the antennas
1500. Alternatively, the front end 200 may be housed in a
non-metallic (e.g., dielectric) enclosure. The windows over the
antennas 1500 may not be cut out of the enclosure 1602, but may
instead represent portions of the enclosure 1602 that allows the
transmitted signals 106 and echoes 108 pass through the windows
1604 from or to the antennas 1500.
[0159] The enclosure 1602 may wrap around the antennas 1500 so that
the antennas are effectively recessed into the conducting body of
the enclosure 1602, which can further improve isolation between the
antennas 1500. Alternatively, in the case of a non-conducting
enclosure 1602, the antennas 1500 may be completely enclosed by the
enclosure 1602 and extra metal foil, and/or absorptive materials,
or other measures may be added to improve isolation between the
antennas 1500. In one embodiment, if the isolation is sufficiently
high, the transmit and receiving antennas 1500 can be operated at
the same time if the returning echoes 108 are sufficiently strong.
This may be the case when the target is at very close range, and
can allow for the sensing assembly 102 to operate without a
transmit/receive switch.
[0160] FIG. 17 is a cross-sectional view of one embodiment of the
antenna 1500 along line 17-17 in FIG. 16. The antenna 1500 ("Planar
Antenna" in FIG. 17) includes a cover layer 1700 ("Superstrate" in
FIG. 17) of an electrically insulating material (such as a
dielectric or other nonconducting material). Examples of such
materials for the cover layer 1700 include, but are not limited to
quartz, sapphire, various polymers, and the like.
[0161] The antenna 1500 may be positioned on a surface of a
substrate 1706 that supports the antenna 1500. A conductive ground
plane 1708 may be disposed on an opposite surface of the substrate
1706, or in another location.
[0162] The cover layer 1700 may be separated from the antenna 1500
by an air gap 1704 ("Air" in FIG. 17). Alternatively, gap between
the cover layer 1700 and the antenna 1500 may be at least partially
filled by another material or fluid other than air. As another
alternative, the air gap may be eliminated, and the cover layer
1700 may rest directly on the antenna 1500. The cover layer 1700
can protect the antenna 1500 from the environment and/or mechanical
damage caused by external objects. In one embodiment, the cover
layer 1700 provides a lensing effect to focus the energy of the
transmitted signals 106 emitted by the antenna 1500 into a beam or
to focus the energy of the reflected echoes 108 toward the antenna
1500.
[0163] This lensing effect can permit transmitted signals 106
and/or echoes 108 to pass through additional layers 1702 of
materials (e.g., insulators such as Teflon, polycarbonate, or other
polymers) that are positioned between the antenna 1500 and the
target object 104 (shown in FIG. 1). For example, the sensing
assembly 102 can be mounted to an object being monitored (e.g., the
top of a tank of fluid being measured by the sensing assembly 102),
while the lensing effect can permit the sensing assembly 102 to
transmit the signals 106 and receive the echoes 108 through the top
of the tank without cutting windows or openings through the top of
the tank).
[0164] In one embodiment, the substrate 1708 may have a thickness
dimension between the opposite surfaces that is thinner than a
wavelength of the carrier signal of the transmitted signals 106
and/or echoes 108. For example, the thickness of the substrate 1708
may be on the order of 1/20th of a wavelength. The thicknesses of
the air gap 1704 and/or superstrate 1700 may be larger, such as 1/3
of the wavelength. Either one or both of the air gap 1704 and the
superstrate 1700 may also be removed altogether.
[0165] One or more embodiments of the system 100 and/or sensing
assembly 102 described herein may be used for a variety of
applications that use the separation distance 110 and/or time of
flight that is measured by the sensing assembly 102. Several
specific examples of applications of the system 100 and/or sensing
assembly 102 are described herein, but not all applications or uses
of the system 100 or sensing assembly 102 are limited to those set
forth herein. For example, many applications that use the detection
of the separation distance 110 (e.g., as a depth measurement) can
use or incorporate the system 100 and/or sensing assembly 102.
[0166] FIG. 18 illustrates one embodiment of a containment system
1800. The system 1800 includes a containment apparatus 1802, such
as a fluid tank, that holds or stores one or more fluids 1806. The
sensing assembly 102 may be positioned on or at a top 1804 of the
containment apparatus 1802 and direct transmitted signals 106
toward the fluid 1806. Reflected echoes 108 from the fluid 1806 are
received by the sensing assembly 102 to measure the separation
distance 110 between the sensing assembly 102 and an upper surface
of the fluid 1806. The location of the sensing assembly 102 may be
known and calibrated to the bottom of the containment apparatus
1802 so that the separation distance 110 to the fluid 1806 may be
used to determine how much fluid 1806 is in the containment
apparatus 1802. The sensing assembly 102 may be able to accurately
measure the separation distance 110 using one or more of the
coarse, fine, and/or ultrafine stage determination techniques
described herein.
[0167] Alternatively or additionally, the sensing apparatus 102 may
direct transmitted signals 106 toward a port (e.g., a filling port
through which fluid 1806 is loaded into the containment apparatus
1802) and monitor movement of the fluid 1806 at or near the port.
For example, if the separation distance 110 from the sensing
assembly 102 to the port is known such that the bit of interest of
the echoes 108 is known, the ultrafine stage determination
described above maybe used to determine if the fluid 1806 at or
near the port is moving (e.g., turbulent). This movement may
indicate that fluid 1806 is flowing into or out of the containment
apparatus 1802. The sensing assembly 102 can use this determination
as an alarm or other indicator of when fluid 1806 is flowing into
or out of the containment apparatus 1802. Alternatively, the
sensing assembly 102 could be positioned or aimed at other
strategically important locations where the presence or absence of
turbulence and/or the intensity (e.g., degree or amount of
movement) could indicate various operating conditions and
parameters (e.g., amounts of fluid, movement of fluid, and the
like). The sensing assembly 102 could periodically switch between
these measurement modes (e.g., measuring the separation distance
110 being one mode and monitoring for movement being another mode),
and then report the data and measurements to the control unit 112
(shown in FIG. 1). Alternatively, the control unit 112 could direct
the sensing assembly 102 to make the various types of measurements
(e.g., measuring the separation distance 110 or monitoring for
movement) at different times.
[0168] FIG. 19 illustrates one embodiment of a zone restriction
system 1900. The system 1900 may include a sensing assembly 102
directing transmitted signals 106 (shown in FIG. 1) toward a first
zone 1902 (e.g., area on a floor, volume in space, and the like). A
human operator 1906 may be located in a different, second zone 1904
to perform various duties. The first zone 1902 may represent a
restricted area or volume where the operator 1906 is to remain out
of when one or more machines (e.g., automated robots or other
components) operate for the safety of the operator 1906. The
sensing assembly 102 can direct the transmitted signals 106 toward
the first zone 1902 and monitor the received echoes 108 to
determine if the operator 1906 enters into the first zone 1902. For
example, intrusion of the operator 1906 into the first zone 1902
may be detected by identification of movement using the one or more
of the coarse, fine, and/or ultrafine stage determination
techniques described herein. If the sensing assembly 102 knows the
distance to the first zone 1902 (e.g., the separation distance 110
to the floor in the first zone 1902), then the sensing assembly 102
can monitor for movement within the subset of interest in the echo
signal that is generated based on the echoes, as described above.
When the sensing assembly 102 detects entry of the operator 1906
into the first zone 1902, the sensing assembly 102 can notify the
control unit 112 (shown in FIG. 1), which can deactivate machinery
operating in the vicinity of the first zone 1902 to avoid injuring
the operator 1906.
[0169] FIG. 20 illustrates another embodiment of a volume
restriction system 2000. The system 2000 may include a sensing
assembly 102 directing transmitted signals 106 (shown in FIG. 1)
toward a safety volume 2002 ("Safety zone" in FIG. 20). Machinery
2004, such as an automated or manually control robotic device, may
be located and configured to move within the safety volume 2002.
The volume through which the transmitted signals 106 are
communicated may be referred to as a protected volume 2006. The
protected zone 2006 may represent a restricted area or volume where
humans or other objects are to remain out of when the machinery
2004 operates. The sensing assembly 102 can direct the transmitted
signals 106 through the protected volume 2006 and monitor the
received echoes 108 to determine if there is any motion identified
outside of the safety zone 2002 but within the protected zone 2006.
For example, intrusion of a human into the protected volume 2006
may be detected by identification of movement using the ultrafine
stage determination described above. When the sensing assembly 102
detects entry into the protected volume 2006, the sensing assembly
102 can notify the control unit 112 (shown in FIG. 1), which can
deactivate the machinery 2004 to avoid injuring any person or thing
that has entered into the protected volume 2006.
[0170] FIG. 21 is a schematic diagram of one embodiment of a mobile
system 2100 that includes the sensing assembly 102. The system 2100
includes a mobile apparatus 2102 with the sensing assembly 102
coupled thereto. In the illustrated embodiment, the mobile
apparatus 2102 is a mobilized robotic system. Alternatively, the
mobile apparatus 2102 may represent another type of mobile device,
such as an automobile, an underground drilling vessel, or another
type of vehicle. The system 2100 uses measurements made by the
sensing assembly 102 to navigate around or through objects. The
system 2100 may be useful for automated navigation based on
detection of motion and/or measurements of separation distances 110
between the sensing assembly 102 and other objects, and/or for
navigation that is assisted with such measurements and
detections.
[0171] For example, the sensing assembly 102 can measure separation
distances 110 between the sensing assembly 102 and multiple objects
2104A-D in the vicinity of the mobile apparatus 2102. The mobile
apparatus 2102 can use these separation distances 110 to determine
how far the mobile apparatus 2102 can travel before needing to turn
or change direction to avoid contact with the objects 2104A-D.
[0172] In one embodiment, the mobile apparatus 2102 can use
multiple sensing assemblies 102 to determine a layout or map of an
enclosed vicinity 2106 around the mobile apparatus 2102. The
vicinity 2106 may be bounded by the walls of a room, building,
tunnel, and the like. A first sensing assembly 102 on the mobile
apparatus 2102 may be oriented to measure separation distances 110
to one or more boundaries (e.g., walls or surfaces) of the vicinity
2106 along a first direction, a second sensing assembly 102 may be
oriented to measure separation distances 110 to one or more other
boundaries of the vicinity 2106 along a different (e.g.,
orthogonal) direction, and the like. The separation distances 110
to the boundaries of the vicinity 2106 can provide the mobile
apparatus 2102 with information on the size of the vicinity 2106
and a current location of the mobile apparatus 2102. The mobile
apparatus 2102 may then move in the vicinity 2106 while one or more
of the sensing assemblies 102 acquire updated separation distances
110 to one or more of the boundaries of the vicinity 2106. Based on
changes in the separation distances 110, the mobile apparatus 2102
may determine where the mobile apparatus 2102 is located in the
vicinity 2106. For example, if an initial separation distance 110
to a first wall of a room is measured as ten feet (three meters)
and an initial separation distance 110 to a second wall of the room
is measured as five feet (1.5 meters), the mobile apparatus 2102
may initially locate itself within the room. If a later separation
distance 110 to the first wall is four feet (1.2 meters) and a
later separation distance 110 to the second wall is seven feet (2.1
meters), then the mobile apparatus 2102 may determine that it has
moved six feet (1.8 meters) toward the first wall and two feet (0.6
meters) toward the second wall.
[0173] In one embodiment, the mobile apparatus 2102 can use
information generated by the sensing assembly 102 to distinguish
between immobile and mobile objects 2104 in the vicinity 2106. Some
of the objects 2104A, 2104B, and 2104D may be stationary objects,
such as walls, furniture, and the like. Other objects 210C may be
mobile objects, such as humans walking through the vicinity 2106,
other mobile apparatuses, and the like. The mobile apparatus 2102
can track changes in separation distances 110 between the mobile
apparatus 2102 and the objects 2104A, 2104B, 2104C, 2104D as the
mobile apparatus 2102 moves. Because the separation distances 110
between the mobile apparatus 2102 and the objects 2104 may change
as the mobile apparatus 2102 moves, both the stationary objects
2104A, 2104B, 2104D and the mobile objects 2104C may appear to move
to the mobile apparatus 2102. This perceived motion of the
stationary objects 2104A, 2104B, 2104D that is observed by the
sensing assembly 102 and the mobile apparatus 2102 is due to the
motion of the sensing assembly 102 and the mobile apparatus 2102.
To compute the motion (e.g., speed) of the mobile apparatus 2102,
the mobile apparatus 210 can track changes in separation distances
110 to the objects 2104 and generate object motion vectors
associated with the objects 2104 based on the changes in the
separation distances 110.
[0174] FIG. 22 is a schematic diagram of several object motion
vectors generated based on changes in the separation distances 110
between the mobile apparatus 2102 and the objects (e.g., the
objects 2104 of FIG. 21) in accordance with one example. The object
motion vectors 2200A-F can be generated by tracking changes in the
separation distances 110 over time. In order to estimate motion
characteristics (e.g., speed and/or heading) of the mobile
apparatus 2102, these object motion vectors 2200 can be combined,
such as by summing and/or averaging the object motion vectors 2200.
For example, a motion vector 2202 of the mobile apparatus 2102 may
be estimated by determining a vector that is an average of the
object motion vectors 2200 and then determining an opposite vector
as the motion vector 2202. The combining of several object motion
vectors 2200 can tend to correct spurious object motion vectors
that are due to other mobile objects in the environment, such as
the object motion vectors 2200C, 2200F that are based on movement
of other mobile objects in the vicinity.
[0175] The mobile apparatus 2102 can learn (e.g., store) which
objects are part of the environment and that can be used for
tracking movement of the mobile apparatus 2102 and may be referred
to as persistent objects. Other objects that are observed that do
not agree with the known persistent objects are called transient
objects. Object motion vectors of the transient objects will have
varying trajectories and may not agree well with each other or the
persistent objects. The transient objects can be identified by
their trajectories as well as their radial distance from the mobile
apparatus 2102, e.g. the walls of the tunnel will remain at their
distance, whereas transient objects will pass closer to the mobile
apparatus 2102.
[0176] In another embodiment, multiple mobile apparatuses 2102 may
include the sensing system 100 and/or sensing assemblies 102 to
communicate information between each other. For example, the mobile
apparatuses 2102 may each use the sensing assemblies 102 to detect
when the mobile apparatuses 2102 are within a threshold distance
from each other. The mobile apparatuses 2102 may then switch from
transmitting the transmitted signals 106 in order to measure
separation distances 110 and/or detect motion to transmitting the
transmitted signals 106 to communicate other information. For
example, instead of generating the digital pulse sequence to
measure separation distances 110, at least one of the mobile
apparatuses 2102 may use the binary code sequence (e.g., of ones
and zeros) in a pattern signal that is transmitted toward another
mobile apparatus 2102 to communicate information. The other mobile
apparatus 2102 may receive the transmitted signal 106 in order to
identify the transmitted pattern signal and interpret the
information that is encoded in the pattern signal.
[0177] FIG. 23 is a schematic diagram of one example of using the
sensing assembly 102 in a medical application. The sensing assembly
102 may use one or more of the stages described above (e.g., coarse
stage, fine stage, and ultrafine stage) to monitor changes in
position of a patient 2300 and/or relatively small movements of the
patient. For example, the ultrafine stage determination of movement
described above may be used for breath rate detection, heart rate
detection, monitoring gross motor or muscle movement, and the like.
Breath rate, heart rate and activity can be useful for diagnosing
sleep disorders, and since the sensing is non-contact and can be
more comfortable for the patient being observed. As one example,
the separation distance 110 to the abdomen and/or chest of the
patient 2300 can be determined to within one bit of the digital
pulse sequence (e.g., the bit of interest), as described above. The
sensing assembly 102 can then track relatively small motions of the
chest and/or abdomen within the subset of interest to track a
breathing rate and/or heart rate. Additionally or alternatively,
the sensing assembly 102 can track the motions of the chest and/or
abdomen and combine the motions with a known, measured, observed,
or designated size of the abdomen to estimate the tidal volume of
breaths of the patient 2300. Additionally or alternatively, the
sensing assembly 102 can track the motions of the chest and abdomen
together to detect paradoxical breathing of the patient 2300.
[0178] As another example, the sensing assembly 102 may communicate
transmitted signals 106 that penetrate into the body of the patient
2300 and sense the motion or absolute position of various internal
structures, such as the heart. Many of these positions or motions
can be relatively small and subtle, and the sensing assembly 102
can use the ultrafine stage determination of motion or the
separation distance 110 to sense the motion or absolute position of
the internal structures.
[0179] Using the non-contact sensing assembly 102 also may be
useful for situations where it is impossible or inconvenient to use
wired sensors on the patient 2300 (e.g., sensors mounted directly
to the test subject, connected by wires back to a medical monitor).
For example, in high-activity situations where conventional wired
sensors may get in the way, the sensing assembly 102 may monitor
the separation distance 110 and/or motion of the patient 2300 from
afar.
[0180] In another example, the sensing assembly 102 can be used for
posture recognition and overall motion or activity sensing. This
can be used for long-term observation of the patient 2300 for the
diagnosis of chronic conditions, such as depression, fatigue, and
overall health of at-risk individuals such as the elderly, among
others. In the case of diseases with relatively slow onset, such as
depression, the long term observation by the sensing assembly 102
may be used for early detection of the diseases. Also, since the
unit can detect the medical parameters or quantities without
anything being mounted on the patient 2300, the sensing assembly
102 may be used to make measurements of the patient 2300 without
the knowledge or cooperation of the patient 2300. This could be
useful in many situations, such as when dealing with children who
would be made upset if sensors are attached to them. It may also
give an indication of the mental state of a patient 2300, such as
their breath becoming rapid and shallow when they become nervous.
This would give rise to a remote lie-detector functionality.
[0181] In another embodiment, data generated by the sensing
assembly 102 may be combined with data generated or obtained by one
or more other sensors. For example, calculation of the separation
distance 110 by the sensing assembly 102 may be used as a depth
measurement that is combined with other sensor data. Such
combination of data from different sensors is referred to herein as
sensor fusion, and includes the fusing of two or more separate
streams of sensor data to form a more complete picture of the
phenomena or object or environment that is being sensed.
[0182] As one example, separation distances 110 calculated using
the sensing assembly 102 may be combined with two-dimensional image
data acquired by a camera. For example, without the separation
distances 110, a computer or other machine may not be able to
determine the actual physical size of the objects in a
two-dimensional image.
[0183] FIG. 24 is a two-dimensional image 2404 of human subjects
2400, 2402 in accordance with one example of an application of the
system 100 shown in FIG. 1. The image 2404 may be acquired by a
two-dimensional image forming apparatus, such as a camera. The
image forming apparatus may acquire the image for use by another
system, such as a security system, an automatically controlled
(e.g., moveable) robotic system, and the like. The human subjects
2400, 2402 may be approximately the same size (e.g., height). In
reality, the human subject 2400 is farther from the image forming
apparatus that acquired the image 2404 than the human subject 2402.
However, due to the inability of the image forming apparatus to
determine the relative separation distances between the image
forming apparatus and each of the subjects 2400, 2402, the system
that relies on the image forming apparatus to recognize the
subjects 2400, 2402 may be unable to determine if the subject 2400
is located farther away (e.g., is at the location of 2400A) or is a
much smaller human than the subject 2402 (e.g., is the size
represented by 2400B).
[0184] The sensing assembly 102 (shown in FIG. 1) can determine
separation distances 110 (shown in FIG. 1) between the image
forming apparatus (e.g., with the sensing assembly 102 disposed at
or near the image forming apparatus) and each of the subjects 2400,
2402 to provide a depth context to the image 2404. For example, the
image forming apparatus or the system that uses the image 2404 for
one or more operations may use the separation distance 110 to each
of the subjects 2400, 2402 to determine that the subjects 2400,
2402 are approximately the same size, with the subject 2400 located
farther away than the subject 2402.
[0185] With this separation distance 110 (shown in FIG. 1)
information and information about the optics that were used to
capture the two dimensional image 2400, it may be possible to
assign actual physical sizes to the subjects 2400, 2402. For
example, knowing the physical size that is encompassed by different
portions (e.g., pixels or groups of pixels) of the image 2400 and
knowing the separation distance 110 to each subject 2400, 2402, the
image forming apparatus and/or the system using the image 2404 for
one or more operations can calculate sizes (e.g., heights and/or
widths) of the subjects 2400, 2402.
[0186] FIG. 25 is a schematic diagram of a sensing system 2500 that
may include the sensing assembly 102 (shown in FIG. 1) in
accordance with one embodiment. Many types of sensors such as light
level sensors, radiation sensors, moisture content sensors, and the
like, obtain measurements of target objects 104 that may change as
the separation distance 110 between the sensors and the target
objects 104 varies. The sensing systems 2500 shown in FIG. 25 may
include or represent one or more sensors that acquire information
that changes as the separation distance 110 changes and may include
or represent the sensing assembly 102. Distance information (e.g.,
separation distances 110) from the sensing systems 2500 and the
target objects 104 can provide for calibration or correction of
other sensor information that is dependent on the distance between
the sensor and the targets being read or monitored by the
sensor.
[0187] For example, the sensing systems 2500 can acquire or measure
information (e.g., light levels, radiation, moisture, heat, and the
like) from the target objects 104A, 104B and the separation
distances 110A, 110B to the target objects 104A, 104B. The
separation distances 110A, 110B can be used to correct or calibrate
the measured information. For example, if the target objects 104A,
104B both provide the same light level, radiation, moisture, heat,
and the like, the different separation distances 110A, 110B may
result in the sensing systems 2500A, 2500B measuring different
light levels, radiation, moisture, heat, and the like. With the
sensing assembly 102 (shown in FIG. 1) measuring the separation
distances 110A, 110B, the measured information for the target
object 104A and/or 104B can be corrected (e.g., increased based on
the size of the separation distance 110A for the target object 104A
and/or decreased based on the size of the separation distance 110B
for the target object 104B) so that the measured information is
more accurate relative to not correcting the measured information
for the different separation distances 110.
[0188] As another example, the sensing system 2500 may include a
reflective pulse oximetry sensor and the sensing assembly 102. Two
or more different wavelengths of light are directed at the surface
of the target object 104 by the system 2500 and a photo detector of
the system 2500 examines the scattered light. The ratio of the
reflected power can be used to determine the oxygenation level of
the blood in the target object 104. Instead of being directly
mounted (e.g., engaged to) the body of the patient that is the
target object 104, the sensing system 2500 may be spaced apart from
the body of the patient.
[0189] The surface of the patient body can be illuminated with
light sources and the sensing assembly 102 (shown in FIG. 1) can
measure the separation distance 110 to the target object 104 (e.g.,
to the surface of the skin). The oxygenation level of the blood in
the patient can then be calibrated or corrected for the decrease in
the reflected power of the light that is caused by the sensing
system 2500 being separated from the patient.
[0190] In another embodiment, the sensing assembly 102 and/or
system 100 shown in FIG. 1 can be provided as a stand-alone unit
that can communicate with other sensors, controllers, computers,
and the like, to add the above-described functionality to a variety
of sensor systems. A software-implemented system can collect and
aggregate the information streams from the sensors and deliver the
sensed information to the controlling system, where the separation
distance 110 measured by the assembly 102 and/or system 100 is used
in conjunction with the sensed information. Alternatively or
additionally, the separation distances 110 measured by the assembly
102 can be collected along with a time stamp or other marker such
as geographic location without communicating directly with the
other sensors, controller, computer, and the like. The
software-implemented system can then reconcile the separation
distance 110 and other sensor data to align the measurements with
each other.
[0191] The examples of sensor fusion described herein are not
limited to just the combination of the sensing assembly 102 and one
other sensor. Additional sensors may be used to aggregate the
separation distances 110 and/or motion detected by the sensing
assembly 102 with the data streams acquired by two or more
additional sensors. For example, audio data (from a microphone),
video data (from a camera), and the separation distances 110 and/or
motion from the sensing assembly 102 can be aggregated to give a
more complete understanding of a physical environment.
[0192] FIG. 28 is a schematic diagram of a sensing system 2800 that
may include the sensing assembly 102 in accordance with one
embodiment. The sensing system 2800 includes a sensor 2802 that
obtains lateral size data of a target object 2804. For example, the
sensor 2802 may be a camera that obtains a two dimensional image of
a box or package. FIG. 29 is a schematic diagram representative of
the lateral size data of the target object 2804 that is obtained by
the sensor 2802. The sensor 2802 (or a control unit communicatively
coupled with the sensor 2802) may measure two dimensional sizes of
the target object 2804, such as a length dimension 2806 and a width
dimension 2808. For example, a two-dimensional surface area 2900 of
the target object 2804 may be calculated from the image acquired by
the sensor 2802. In one embodiment, the number of pixels or other
units of the image formed by the sensor 2802 can be counted or
measured to determine the surface area 2900 of the target object
2804.
[0193] FIG. 30 is another view of the sensing assembly 102 and the
target object 2804 shown in FIGS. 28 and 29. In order to calculate
the volume or three dimensional outer surface area of the target
object 2804, the sensing assembly 102 may be used to measure a
depth dimension 2810 of the target object 2804. For example, the
sensing assembly 102 may measure the separation distance 110
between the sensing assembly 102 and a surface 3000 (e.g., an upper
surface) of the target object 2804 that is imaged by the sensor
2802. If a separation distance 3002 between the sensing assembly
102 and a supporting surface 3004 on which the target object 2804
is known or previously measured, then the separation distance 110
may be used to calculate the depth dimension 2810 of the target
object 2804. For example, the measured separation distance 110 may
be subtracted from the known or previously measured separation
distance 3002 to calculate the depth dimension 2810. The depth
dimension 2810 may be combined (e.g., by multiplying) with the
lateral size data (e.g., the width dimension 2808 and the length
dimension 2806) of the target object 2804 to calculate a volume of
the target object 2804. In another example, the depth dimension
2810 can be combined with the lateral size data to calculate
surface areas of each or one or more surfaces of the target object
2804, which may then be combined to calculate an outer surface area
of the target object 2804. Combining the depth data obtained from
the sensing assembly 102 with the two dimensional, or lateral, data
obtained by the sensor 2802 may be useful in applications where the
size, volume, or surface area of the target object 2804 is to be
measured, such as in package shipping, identification or
distinguishing between different sized target objects, and the
like.
[0194] FIG. 26 is a schematic diagram of another embodiment of a
sensing system 2600. The sensing system 2600 may be similar to the
system 100 shown in FIG. 1. For example, the system 2600 may
include a sensing assembly 2602 ("Radar Unit") that is similar to
the sensing assembly 102 (shown in FIG. 1). Although the sensing
assembly 2602 is labeled "Radar Unit" in FIG. 26, alternatively,
the sensing assembly 2602 may use another technique or medium for
determining separation distances 110 and/or detecting motion of a
target object 104 (e.g., light), as described above in connection
with the system 100.
[0195] The assembly 2602 includes a transmitting antenna 2604 that
may be similar to the transmitting antenna 204 (shown in FIG. 2)
and a receiving antenna 2606 that may be similar to the receiving
antenna 206 (shown in FIG. 2). In the illustrated embodiment, the
antennas 2604, 2606 are connected to the assembly 2602 using cables
2608. The cables 2608 may be flexible to allow the antennas 2604,
2606 to be re-positioned relative to the target object 104
on-the-fly. For example, the antennas 2604, 2606 may be moved
relative to the target object 104 and/or each other as the
transmitted signals 106 are transmitted toward the target object
104 and/or the echoes 108 are received off the target object 104,
or between the transmission of the transmitted signals 106 and the
receipt of the echoes 108.
[0196] The antennas 2604, 2606 may be moved to provide for
pseudo-bistatic operation of the system 2600. For example, the
antennas 2604, 2606 can be moved around to various or arbitrary
locations to capture echoes 108 that may otherwise be lost if the
antennas 2604, 2606 were fixed in position. In one embodiment, the
antennas 2604, 2606 could be positioned on opposite sides of the
target object 104 in order to test for the transmission of the
transmitted signals 106 through the target object 104. Changes in
the transmission of the transmitted signals 106 through the target
object 104 can indicate physical changes in the target object 104
being sensed.
[0197] This scheme can be used with greater numbers of antennas
2604 and/or 2606. For example, multiple receiving antennas 2606 can
be used to detect target objects 104 that may otherwise be
difficult to detect. Multiple transmitting antennas 2604 may be
used to illuminate target objects 104 with transmitted signals 106
that may otherwise not be detected. Multiple transmitting antennas
2604 and multiple receiving antennas 2606 can be used at the same
time. The transmitting antennas 2604 and/or receiving antennas 2606
can be used at the same time, transmitting copies of the
transmitted signal 106 or receiving multiple echoes 108, or the
sensing assembly 2602 can be switched among the transmitting
antennas 2604 and/or among the receiving antennas 2606, with the
observations (e.g., separation distances 110 and/or detected
motion) built up over time.
[0198] FIGS. 27A-B illustrate one embodiment of a method 2700 for
sensing separation distances from a target object and/or motion of
the target object. The method 2700 may be used in conjunction with
one or more of the systems or sensing assemblies described
herein.
[0199] At 2702, a determination is made as to whether to use to the
coarse stage determination of the time of flight and/or separation
distance. For example, an operator of the system 100 (shown in FIG.
1) may manually provide input to the system 100 and/or the system
100 may automatically determine whether to use the coarse stage
determination described above. If the coarse stage determination is
to be used, flow of the method 2700 proceeds to 2704.
Alternatively, flow of the method 2700 may proceed to 2718. In one
embodiment, the coarse stage uses a single channel (e.g., either
the I channel or the Q channel) of the transmitted signal and
received echo signal to determine the time of flight and/or
separation distance, also as described above.
[0200] At 2704, an oscillating signal is mixed with a coarse
transmit pattern to create a transmitted signal. For example, the
oscillating signal 216 (shown in FIG. 2) is mixed with a digital
pulse sequence of the transmit pattern signal 230 (shown in FIG. 2)
to form the transmitted signal 106 (shown in FIG. 1), as described
above.
[0201] At 2706, the transmitted signal is transmitted toward a
target object. For example, the transmitting antenna 204 (shown in
FIG. 2) may transmit the transmitted signal 106 (shown in FIG. 1)
toward the target object 104 (shown in FIG. 1), as described
above.
[0202] At 2708, echoes of the transmitted signal that are reflected
off the target object are received. For example, the echoes 108
(shown in FIG. 1) that are reflected off the target object 104
(shown in FIG. 1) are received by the receiving antenna 206 (shown
in FIG. 2), as described above.
[0203] At 2710, the received echoes are down converted to obtain a
baseband signal. For example, the echoes 108 (shown in FIG. 1) are
converted into the baseband echo signal 226 (shown in FIG. 2). For
example, the received echo signal 224 may be mixed with the same
oscillating signal 216 (shown in FIG. 2) that was mixed with the
coarse transmit pattern signal 230 (shown in FIG. 2) to generate
the transmitted signal 106 (shown in FIG. 1). The echo signal 224
can be mixed with the oscillating signal 216 to generate the
baseband echo signal 226 (shown in FIG. 2) as the coarse receive
data stream, as described above.
[0204] At 2712, the baseband signal is digitized to obtain the
coarse receive data stream. For example, it may pass through the
baseband processor 232 including the digitizer 730 to produce the
digitized echo signal 740.
[0205] At 2714, a correlation window (e.g., a coarse correlation
window) and a coarse mask are compared to the data stream to
identify a subset of interest. Alternatively, the mask (e.g., a
mask to eliminate or change one or more portions of the data
stream) may not be used. In one embodiment, the coarse correlation
window 320 (shown in FIG. 3) that includes all or a portion of the
coarse transmit pattern included in the transmitted signal 106
(shown in FIG. 1) is compared to various subsets or portions of the
digitized echo signal 740 (shown in FIG. 2), as described above.
Correlation values can be calculated for the various subsets of the
data stream 226, and the subset of interest may be identified by
comparing the correlation values, such as by identifying the subset
having a correlation value that is the greatest or is greater than
one or more other subsets of interest.
[0206] At 2716, a time of flight of the transmitted signal and echo
is calculated based on a time delay of the subset of interest. This
time of flight can be referred to as a coarse time of flight. As
described above, the subset of interest can be associated with a
time lag (t.sub.d) between transmission of the transmitted signal
106 (shown in FIG. 1) and the first bit of the subset of interest
(or another bit in the subset of interest). The time of flight can
be equal to the time lag, or the time of flight can be based on the
time lag, with a correction or correlation factor (e.g., for the
propagation of signals) being used to modify the time lag to the
time of flight, as described above.
[0207] At 2718, a determination is made as to whether the fine
stage determination of the separation distance is to be used. For
example, a determination may be made automatically or manually to
use the fine stage determination to further refine the measurement
of the separation distance 110 (shown in FIG. 1) and/or to monitor
or track motion of the target object 104 (shown in FIG. 1), as
described above. If the fine stage is to be used, then flow of the
method 2700 may proceed to 2720. On the other hand, if the fine
stage is not to be used, then flow of the method 2700 may return to
2702.
[0208] At 2720, an oscillating signal is mixed with a digital pulse
sequence to create a transmitted signal. As described above, the
transmit pattern that is used in the fine stage may be different
from the transmit pattern used in the coarse stage. Alternatively,
the transmit pattern may be the same for the coarse stage and the
fine stage.
[0209] At 2722, the transmitted signal is communicated toward the
target object, similar to as described above in connection with
2706.
[0210] At 2724, echoes of the transmitted signal that are reflected
off the target object are received, similar to as described above
in connection with 2708.
[0211] At 2726, the received echoes are down converted to obtain a
baseband signal. For example, the echoes 108 (shown in FIG. 1) are
converted into the baseband echo signal 226 (shown in FIG. 2).
[0212] At 2728, the baseband signal 226 is compared to a fine
receive pattern. The fine receive pattern may be delayed by the
coarse time of flight, as described above. For example, instead of
comparing the baseband signal with the receive pattern with both
the baseband signal and the receive pattern having the same
starting or initial time reference, the receive pattern may be
delayed by the same time as the time delay measured by the coarse
stage determination. This delayed receive pattern also may be
referred to as a "coarse delayed fine extraction pattern" 728.
[0213] At 2730, a time lag between the fine data stream and the
time delayed receive pattern is calculated. This time lag may
represent the temporal overlap or mismatch between the waveforms in
the fine data stream and the time delayed receive pattern, as
described above in connection with FIGS. 8 through 11. The time lag
may be measured as the energies of the waveforms that represent the
overlap between the fine data stream and the time delayed receive
pattern. As described above, time periods 808, 810, 904, 906 (shown
in FIGS. 8 and 9) representative of the time lag may be
calculated.
[0214] At 2732, the time of flight measured by the coarse stage
(e.g., the "time of flight estimate") is refined by the time lag.
For example, the time lag calculated at 2730 can be added to the
time of flight calculated at 2716. Alternatively, the time lag may
be added to a designated time of flight, such as a time of flight
associated with or calculated from a designated or known separation
distance 110 (shown in FIG. 1).
[0215] At 2734, the time of flight (that includes the time lag
calculated at 2732) is used to calculate the separation distance
from the target object, as described above. Flow of the method 2700
may then return to 2702 in a loop-wise manner. The above methods
can be repeated for the I and Q channels separately or in parallel
using parallel paths as in FIG. 12 or a switch or multiplexed path
as described above to extract differences in the I and Q channels.
These differences can be examined to resolve the phase of the
echoes.
[0216] In one embodiment, performance of the fine stage
determination (e.g., as described in connection with 2720 through
2732) is performed on one of the I or Q components of channels of
the transmit signal and the echo signal, as described above. For
example, the I channel of the echo signal 226 (shown in FIG. 2) may
be examined in order to measure the amount of temporal overlap
between the time-delayed receive pattern and the echo signal 226,
as described above. In order to perform the ultrafine stage
determination, a similar examination may be performed on another
component or channel of the echo signal, such as the Q channel. For
example, the I channel analysis of the echo signal 226 (e.g., the
fine stage) may be performed concurrently or simultaneously with
the Q channel analysis of the same echo signal 226 (e.g., the
ultrafine stage). Alternatively, the fine stage and ultrafine stage
may be performed sequentially, with one of the I or Q channels
being examined to determine a temporal overlap of the echo signal
and the time-delayed receive pattern before the other of the Q or I
channels being examined to determine a temporal overlap. The
temporal overlaps of the I and Q channels are used to calculate
time lags (e.g., I and Q channel time lags), which can be added to
the coarse stage determination or estimate of the time of flight.
This time of flight can be used to determine the separation
distance 110 (shown in FIG. 1), as described above. Alternatively
or additionally, the time lags of the waveforms in the I channel
and Q channel can be examined to resolve phases of the echoes in
order to calculate separation distance or motion of the target.
[0217] As described above, the ultrafine stage determination may
alternatively or additionally involve a similar process as the
coarse stage determination. For example, the coarse stage
determination may examine the I channel of the receive pattern and
the data stream to determine correlation values of different
subsets of the data stream and, from those correlation values,
determine a subset of interest and a corresponding time-of-flight,
as described herein. The ultrafine stage determination can use the
Q channel of the receive pattern and the data stream to determine
correlation values of different subsets of the data stream and,
from those correlation values, determine a subset of interest and a
time-of-flight, as described above. The times-of-flight from the I
channel and Q channel can be combined (e.g., averaged) to calculate
a time of flight and/or separation distance to the target. The
correlation values calculated by the ultrafine stage determination
can be used to calculate an additional time delay that can be added
to the time delays from the coarse stage and/or the fine stage to
determine a time of flight and/or separation distance to the
target. Alternatively or additionally, the correlation values of
the waveforms in the I channel and Q channel can be examined to
resolve phases of the echoes in order to calculate separation
distance or motion of the target.
[0218] In another embodiment, another method (e.g., a method for
measuring a separation distance to a target object) is provided.
The method includes transmitting an electromagnetic first
transmitted signal from a transmitting antenna toward a target
object that is separated from the transmitting antenna by a
separation distance. The first transmitted signal includes a first
transmit pattern representative of a first sequence of digital
bits. The method also includes receiving a first echo of the first
transmitted signal that is reflected off the target object,
converting the first echo into a first digitized echo signal, and
comparing a first receive pattern representative of a second
sequence of digital bits to the first digitized echo signal to
determine a time of flight of the first transmitted signal and the
echo.
[0219] In another aspect, the method also includes calculating the
separation distance to the target object based on the time of
flight.
[0220] In another aspect, the method also includes generating an
oscillating signal and mixing at least a first portion of the
oscillating signal with the first transmit pattern to form the
first transmitted signal.
[0221] In another aspect, converting the first echo into the first
digitized echo signal includes mixing at least a second portion of
the oscillating signal with an echo signal that is based on the
first echo received off the target object.
[0222] In another aspect, comparing the first receive pattern
includes matching the sequence of digital bits of the first receive
pattern to subsets of the first digitized echo signal to calculate
correlation values for the subsets. The correlation values are
representative of degrees of match between the sequence of digital
bits in the first receive pattern and the subsets of the first
digitized echo signal.
[0223] In another aspect, at least one of the subsets of the
digitized echo signal is identified as a subset of interest based
on the correlation values. The time of flight can be determined
based on a time delay between transmission of the transmitted
signals and occurrence of the subset of interest.
[0224] In another aspect, the method also includes transmitting an
electromagnetic second transmitted signal toward the target object.
The second transmitted signal includes a second transmit pattern
representative of a second sequence of digital bits. The method
also includes receiving a second echo of the second transmitted
signal that is reflected off the target object, converting the
second echo into a second baseband echo signal, and comparing a
second receive pattern representative of a third sequence of
digital bits to the second baseband echo signal to determine
temporal misalignment between one or more waveforms of the second
baseband echo signal and one or more waveforms of the second
receive pattern. The temporal misalignment representative of a time
lag between the second receive pattern and the second baseband echo
signal is extracted and then the time lag is then calculated.
[0225] In another aspect, the method also includes adding the time
lag to the time of flight.
[0226] In another aspect, converting the second echo into the
second digitized echo signal includes forming an in-phase (I)
channel of the second baseband echo signal and a quadrature (Q)
channel of the second baseband echo signal. Comparing the second
receive pattern includes comparing an I channel of the second
receive pattern to the I channel of the second digitized echo
signal to determine an I component of the temporal misalignment and
comparing a Q channel of the second receive pattern to the Q
channel of the second digitized echo signal to determine a Q
component of the temporal misalignment.
[0227] In another aspect, the time lag that is added to the time of
flight includes the I component of the temporal misalignment and
the Q component of the temporal misalignment.
[0228] In another aspect, the method also includes resolving phases
of the first echo and the second echo by examining the I component
of the temporal misalignment and the Q component of the temporal
misalignment, where the time of flight calculated based on the
phases that are resolved.
[0229] In another aspect, at least two of the first transmit
pattern, the first receive pattern, the second transmit pattern, or
the second receive pattern differ from each other.
[0230] In another aspect, at least two of the first transmit
pattern, the first receive pattern, the second transmit pattern, or
the second receive pattern include a common sequence of digital
bits.
[0231] In another embodiment, a system (e.g., a sensing system) is
provided that includes a transmitter, a receiver, and a baseband
processor. The transmitter is configured to generate an
electromagnetic first transmitted signal that is communicated from
a transmitting antenna toward a target object that is a separated
from the transmitting antenna by a separation distance. The first
transmitted signal includes a first transmit pattern representative
of a sequence of digital bits. The receiver is configured to
generate a first digitized echo signal that is based on an echo of
the first transmitted signal that is reflected off the target
object. The correlator device is configured to compare a first
receive pattern representative of a second sequence of digital bits
to the first digitized echo signal to determine a time of flight of
the first transmitted signal and the echo.
[0232] In another aspect, the baseband processor is configured to
calculate the separation distance to the target object based on the
time of flight.
[0233] In another aspect, the system also includes an oscillating
device configured to generate an oscillating signal. The
transmitter is configured to mix at least a first portion of the
oscillating signal with the first transmit pattern to form the
first transmitted signal.
[0234] In another aspect, the receiver is configured to receive at
least a second portion of the oscillating signal and to mix the at
least the second portion of the oscillating signal with an echo
signal that is representative of the echo to create the first
baseband echo signal.
[0235] In another aspect, the baseband echo signal may be digitized
into a first digitized echo signal and the correlator device is
configured to compare the sequence of digital bits of the first
receive pattern to subsets of the first digitized echo signal to
calculate correlation values for the subsets. The correlation
values are representative of degrees of match between the first
receive pattern and the digital bits of the digitized echo
signal.
[0236] In another aspect, at least one of the subsets of the
digitized echo signal is identified by the correlator device as a
subset of interest based on the correlation values. The time of
flight is determined based on a time delay between transmission of
the first transmitted signal and occurrence of the subset of
interest in the first digitized echo signal.
[0237] In another aspect, the transmitter is configured to transmit
an electromagnetic second transmitted signal toward the target
object. The second transmitted signal includes a second transmit
pattern representative of a second sequence of digital bits. The
receiver is configured to create a second digitized echo signal
based on a second echo of the second transmitted signal that is
reflected off the target object. The baseband processor is
configured to compare a second receive pattern representative of a
third sequence of digital bits to the second digitized echo signal
to determine temporal misalignment between one or more waveforms of
the second digitized echo signal and one or more waveforms of the
second receive pattern. The temporal misalignment is representative
of a time lag between the second receive pattern and the second
baseband echo signal that is added to the time of flight.
[0238] In another aspect, the receiver is configured to form an
in-phase (I) channel of the second digitized echo signal and a
quadrature (Q) channel of the second digitized echo signal. The
system can also include a baseband processing system configured to
compare an I channel of the second receive pattern to the I channel
of the second digitized echo signal to determine an I component of
the temporal misalignment. The baseband processing system also is
configured to compare a Q channel of the second receive pattern to
the Q channel of the second digitized echo signal to determine a Q
component of the temporal misalignment.
[0239] In another aspect, the time lag that is added to the time of
flight includes the I component of the temporal misalignment and
the Q component of the temporal misalignment.
[0240] In another aspect, the baseband processing system is
configured to resolve phases of the first echo and the second echo
based on the I component of the temporal misalignment and the Q
component of the temporal misalignment. The time of flight is
calculated based on the phases that are resolved. For example, the
time of flight may be increased or decreased by a predetermined or
designated amount based on an identified or measured difference in
the phases that are resolved.
[0241] In another embodiment, another method (e.g., for measuring a
separation distance to a target object) is provided. The method
includes transmitting a first transmitted signal having waveforms
representative of a first transmit pattern of digital bits and
generating a first digitized echo signal based on a first received
echo of the first transmitted signal. The first digitized echo
signal includes waveforms representative of a data stream of
digital bits. The method also includes comparing a first receive
pattern of digital bits to plural different subsets of the data
stream of digital bits in the first digitized echo signal to
identify a subset of interest that indicates the presence and/or
temporal location of the first receive pattern than one or more
other subsets. The method further includes identifying a time of
flight of the first transmitted signal and the first received echo
based on a time delay between a start of the data stream in the
first digitized echo signal and the subset of interest.
[0242] In another aspect, the method also includes transmitting a
second transmitted signal having waveforms representative of a
second transmit pattern of digital bits and generating an in-phase
(I) component of a second baseband echo signal and a quadrature (Q)
component of the second baseband echo signal that is based on a
second received echo of the second transmitted signal. The second
baseband echo signal includes waveforms representative of a data
stream of digital bits. The method also includes comparing a
time-delayed second receive pattern of waveforms that are
representative of a sequence of digital bits to the second baseband
echo signal. The second receive pattern is delayed from a time of
transmission of the second transmitted signal by the time delay of
the subset of interest. An in-phase (I) component of the second
receive pattern is compared to an I component of the second
baseband echo signal to identify a first temporal misalignment
between the second receive pattern and the second baseband echo
signal. A quadrature (Q) component of the second receive pattern is
compared to a Q component of the second baseband echo signal to
identify a second temporal misalignment between the second receive
pattern and the second baseband echo signal. The method also
includes increasing the time of flight by the first and second
temporal misalignments.
[0243] In another aspect, the method also includes identifying
motion of the target object based on changes in one or more of the
first or second temporal misalignments.
[0244] In another aspect, the first transmit pattern differs from
the first receive pattern.
[0245] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the inventive subject matter without departing from its scope.
While the dimensions and types of materials described herein are
intended to define the parameters of the inventive subject matter,
they are by no means limiting and are exemplary embodiments. Many
other embodiments will be apparent to one of ordinary skill in the
art upon reviewing the above description. The scope of the subject
matter described herein should, therefore, be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled. In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Moreover, in the following claims, the terms "first,"
"second," and "third," etc. are used merely as labels, and are not
intended to impose numerical requirements on their objects.
Further, the limitations of the following claims are not written in
means-plus-function format and are not intended to be interpreted
based on 35 U.S.C. .sctn. 112, sixth paragraph, unless and until
such claim limitations expressly use the phrase "means for"
followed by a statement of function void of further structure.
[0246] This written description uses examples to disclose several
embodiments of the inventive subject matter, including the best
mode, and also to enable any person of ordinary skill in the art to
practice the embodiments disclosed herein, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the subject matter is defined by
the claims, and may include other examples that occur to one of
ordinary skill in the art. Such other examples are intended to be
within the scope of the claims if they have structural elements
that do not differ from the literal language of the claims, or if
they include equivalent structural elements with insubstantial
differences from the literal languages of the claims.
[0247] The foregoing description of certain embodiments of the
disclosed subject matter will be better understood when read in
conjunction with the appended drawings. To the extent that the
figures illustrate diagrams of the functional blocks of various
embodiments, the functional blocks are not necessarily indicative
of the division between hardware circuitry. Thus, for example, one
or more of the functional blocks (for example, processors or
memories) may be implemented in a single piece of hardware (for
example, a general purpose signal processor, microcontroller,
random access memory, hard disk, and the like). Similarly, the
programs may be stand alone programs, may be incorporated as
subroutines in an operating system, may be functions in an
installed software package, and the like. The various embodiments
are not limited to the arrangements and instrumentality shown in
the drawings.
[0248] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural of said elements or steps, unless such exclusion
is explicitly stated. Furthermore, references to "one embodiment"
of the present inventive subject matter are not intended to be
interpreted as excluding the existence of additional embodiments
that also incorporate the recited features. Moreover, unless
explicitly stated to the contrary, embodiments "comprising,"
"including," or "having" an element or a plurality of elements
having a particular property may include additional such elements
not having that property.
[0249] Since certain changes may be made in the above-described
systems and methods, without departing from the spirit and scope of
the subject matter herein involved, it is intended that all of the
subject matter of the above description or shown in the
accompanying drawings shall be interpreted merely as examples
illustrating the inventive concepts herein and shall not be
construed as limiting the disclosed subject matter.
* * * * *