U.S. patent application number 15/583268 was filed with the patent office on 2017-11-23 for systems and methods for correcting for leakage and distortion in radar systems.
This patent application is currently assigned to Autoliv ASP, Inc.. The applicant listed for this patent is Autoliv ASP, Inc.. Invention is credited to Xueru Ding, Walter Poiger, Jeff Schaefer.
Application Number | 20170336502 15/583268 |
Document ID | / |
Family ID | 52339288 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170336502 |
Kind Code |
A1 |
Ding; Xueru ; et
al. |
November 23, 2017 |
Systems and Methods for Correcting for Leakage and Distortion in
Radar Systems
Abstract
Methods and systems for correcting leakage and/or distortion in
radar systems include defining an integration time period, dividing
the integration time period into a first sub-period and a second
sub-period, at least partially transmitting a transmission radar
signal during the first sub-period of the integration time period,
not transmitting at all during the second sub-period of the
integration time period, integrating the detected signal during
both the first sub-period and the second sub-period, and
subtracting a last sampled integrated value of the second
sub-period from a last sampled integrated value of the first
sub-period to generate a corrected integrated value for the
integration time period.
Inventors: |
Ding; Xueru; (Newton,
MA) ; Poiger; Walter; (Bad Neustadt, DE) ;
Schaefer; Jeff; (Chelmsford, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Autoliv ASP, Inc. |
Ogden |
UT |
US |
|
|
Assignee: |
Autoliv ASP, Inc.
Ogden
UT
|
Family ID: |
52339288 |
Appl. No.: |
15/583268 |
Filed: |
May 1, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14162085 |
Jan 23, 2014 |
9638794 |
|
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15583268 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 13/4454 20130101;
G01S 7/038 20130101; G01S 2007/2886 20130101 |
International
Class: |
G01S 13/44 20060101
G01S013/44; G01S 7/03 20060101 G01S007/03 |
Claims
1. A method of correcting for leakage in a radar sensor system,
comprising: defining an integration time period, the radar sensor
system being configured to integrate a detected signal during the
integration time period; dividing the integration time period into
a first sub-period and a second sub-period, the radar sensor system
at least partially transmitting a transmission radar signal during
the first sub-period of the integration time period, and the radar
sensor system not transmitting at all during the second sub-period
of the integration time period; integrating the detected signal
during both the first sub-period of the integration time period and
the second sub-period of the integration time period to generate a
plurality of sampled integrated values; and subtracting a last
sampled integrated value of the second sub-period of the
integration time period from a last sampled integrated value of the
first sub-period of the integration time period to generate a
corrected integrated value for the integration time period.
2. The method of claim 1, wherein each integration time period is
associated with a transmitted radar signal of a different
frequency.
3. The method of claim 1, wherein: the radar sensor system
comprising a first transmitter and a second transmitter; the first
transmitter at least partially transmits the transmission radar
signal during the first sub-period of the integration time period
and does not transmit during the second sub-period of the
integration time period; the second transmitter at least partially
transmits a second transmission radar signal during a first
sub-period of a second integration time period and does not
transmit at all during a second sub-period of the second
integration time period.
4. The method of claim 3, wherein the first and second transmission
radar signals are of the same frequency.
5. The method of claim 3, further comprising: integrating the
detected signal during both the first sub-period of the second
integration time period and the second sub-period of the second
integration time period to generate a second plurality of sampled
integrated values; and subtracting a last sampled integrated value
of the second sub-period of the second integration time period from
a last sampled integrated value of the first sub-period of the
second integration time period to generate a second corrected
integrated value for the integration time period.
6. The method of claim 3, wherein the first and second integration
time periods define a pair of integration time periods.
7. The method of claim 6, wherein each of a plurality of pairs of
integration time periods is associated with a different frequency
of the first and second transmission radar signals of the pair of
integration time periods.
8. The method of claim 1, wherein the detected signal is one of an
in-phase (I) and quadrature (Q) signal of the radar sensor
system.
9. A radar sensor system with correction for leakage, comprising: a
transmitter; a receiver; and a controller and/or processor for
processing signals associated with the radar sensor system, the
controller and/or processor: (i) defining an integration time
period, the radar sensor system being configured to integrate a
detected signal during the integration time period, (ii) dividing
the integration time period into a first sub-period and a second
sub-period, the transmitter at least partially transmitting a
transmission radar signal during the first sub-period of the
integration time period, and the transmitter not transmitting at
all during the second sub-period of the integration time period,
(iii) integrating the detected signal during both the first
sub-period of the integration time period and the second sub-period
of the integration time period to generate a plurality of sampled
integrated values, and (iv) subtracting a last sampled integrated
value of the second sub-period of the integration time period from
a last sampled integrated value of the first sub-period of the
integration time period to generate a corrected integrated value
for the integration time period.
10. The system of claim 9, wherein each integration time period is
associated with a transmitted radar signal of a different
frequency.
11. The system of claim 9, further comprising a second transmitter;
wherein: the first transmitter at least partially transmits the
transmission radar signal during the first sub-period of the
integration time period and does not transmit at all during the
second sub-period of the integration time period; and the second
transmitter at least partially transmits a second transmission
radar signal during a first sub-period of a second integration time
period and does not transmit at all during a second sub-period of
the second integration time period.
12. The system of claim 11, wherein the first and second
transmission radar signals are of the same frequency.
13. The system of claim 11, wherein the controller and/or
processor: integrates the detected signal during both the first
sub-period of the second integration time period and the second
sub-period of the second integration time period to generate a
second plurality of sampled integrated values; and subtracts a last
sampled integrated value of the second sub-period of the second
integration time period from a last sampled integrated value of the
first sub-period of the second integration time period to generate
a second corrected integrated value for the integration time
period.
14. The system of claim 11, wherein the first and second
integration time periods define a pair of integration time
periods.
15. The system of claim 14, wherein each of a plurality of pairs of
integration time periods is associated with a different frequency
of the first and second transmission radar signals of the pair of
integration time periods.
16. The system of claim 9, wherein the detected signal is one of an
in-phase (I) and quadrature (Q) signal of the radar sensor
system.
17. A method of correcting for leakage in a radar sensor system,
comprising: defining an integration time period, the radar sensor
system being configured to integrate a detected signal during the
integration time period; dividing the integration time period into
a first sub-period and a second sub-period, the radar sensor system
at least partially transmitting a transmission radar signal during
the first sub-period of the integration time period, and the radar
sensor system not transmitting at all during the second sub-period
of the integration time period; integrating the detected signal
during both the first sub-period of the integration time period and
the second sub-period of the integration time period to generate a
plurality of sampled integrated values; inverting a polarity of a
signal used in generating the detected signal during the second
sub-period of the integration time period; and generating a
corrected integrated value for the integration time period using a
last sampled integrated value of the plurality of sampled
integrated values.
18. The method of claim 17, further comprising transmitting a
transmission radar signal during the integration time period.
19. The method of claim 17, wherein the signal used in generating
the detected signal is an intermediate frequency (IF) signal
generated by the radar sensor system.
20. The method of claim 17, wherein a controllable switch is used
to invert the polarity of the signal used in generating the
detected signal.
21. The method of claim 21, wherein the controllable switch is a
double-pole, double-throw (DPDT) switch.
22. The method of claim 17, wherein the detected signal is one of
an in-phase (I) and quadrature (Q) signal of the radar sensor
system.
23. A radar sensor system with correction for leakage, comprising:
a transmitter; a controllable circuit; and a controller and/or
processor for processing signals associated with the radar sensor
system, the controller and/or processor: (i) defining an
integration time period, the radar sensor system being configured
to integrate a detected signal during the integration time period,
(ii) dividing the integration time period into a first sub-period
and a second sub-period, the radar sensor system at least partially
transmitting a transmission radar signal during the first
sub-period of the integration time period, and the radar sensor
system not transmitting at all during the second sub-period of the
integration time period; (iii) integrating the detected signal
during both the first sub-period of the integration time period and
the second sub-period of the integration time period to generate a
plurality of sampled integrated values, (iv) generating a control
signal to control the controllable circuit to invert a polarity of
a signal used in generating the detected signal during the second
sub-period of the integration time period, and (v) generating a
corrected integrated value for the integration time period using a
last sampled integrated value of the plurality of sampled
integrated values.
24. The system of claim 23, wherein the transmitter transmits a
transmission radar signal during the integration time period.
25. The system of claim 23, wherein the signal used in generating
the detected signal is an intermediate frequency (IF) signal
generated by the radar sensor system.
26. The system of claim 23, wherein the controllable circuit is a
controllable switch used to invert the polarity of the signal used
in generating the detected signal.
27. The system of claim 26, wherein the controllable switch is a
double-pole, double-throw (DPDT) switch.
28. The system of claim 23, wherein the detected signal is one of
an in-phase (I) and quadrature (Q) signal of the radar sensor
system.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 14/162,085, filed Jan. 23, 2014, title
"Systems and Methods for Correcting for Leakage and Distortion in
Radar Systems," which is incorporated by reference herein in its
entirety for all purposes.
TECHNICAL FIELD
[0002] The present disclosure relates generally to the field of
radar systems. More particularly, this disclosure relates to
corrections for leakage and/or pattern distortion in radar
systems.
BACKGROUND
[0003] Due to production cost considerations, many radar system and
radar sensors are limited to non-ideal constraints on and/or
corrections for the radio frequency (RF) and local oscillator (LO)
signal leakage. The RF and LO signal leakage, when improperly
constrained or corrected for, impairs antenna patterns and phase
differencing, for example, by causing pattern distortions, which
ultimately affects radar performance.
SUMMARY
[0004] In one aspect, at least one embodiment described herein
provides a method of correcting for leakage in a radar sensor
system. The method includes defining an integration time period,
the radar sensor system being configured to integrate a detected
signal during the integration time period. The method also includes
dividing the integration time period into a first sub-period and a
second sub-period, the radar sensor system at least partially
transmitting a transmission radar signal during the first
sub-period of the integration time period, and the radar sensor
system not transmitting at all during the second sub-period of the
integration time period. The method also includes integrating the
detected signal during both the first sub-period of the integration
time period and the second sub-period of the integration time
period to generate a plurality of sampled integrated values. The
method also includes subtracting a last sampled integrated value of
the second sub-period of the integration time period from a last
sampled integrated value of the first sub-period of the integration
time period to generate a corrected integrated value for the
integration time period.
[0005] Any of the aspects and/or embodiments described herein can
include one or more of the following embodiments. In some
embodiments, each integration time period is associated with a
transmitted radar signal of a different frequency. In some
embodiments, the radar sensor system includes a first transmitter
and a second transmitter. In some embodiments, the first
transmitter at least partially transmits the transmission radar
signal during the first sub-period of the integration time period
and does not transmit during the second sub-period of the
integration time period. In some embodiments, the second
transmitter at least partially transmits a second transmission
radar signal during a first sub-period of a second integration time
period and does not transmit at all during a second sub-period of
the second integration time period. In some embodiments, the first
and second transmission radar signals are of the same
frequency.
[0006] In some embodiments, the method includes integrating the
detected signal during both the first sub-period of the second
integration time period and the second sub-period of the second
integration time period to generate a second plurality of sampled
integrated values. In some embodiments, the method includes
subtracting a last sampled integrated value of the second
sub-period of the second integration time period from a last
sampled integrated value of the first sub-period of the second
integration time period to generate a second corrected integrated
value for the integration time period. In some embodiments, the
first and second integration time periods define a pair of
integration time periods. In some embodiments, each of a plurality
of pairs of integration time periods is associated with a different
frequency of the first and second transmission radar signals of the
pair of integration time periods. In some embodiments, the detected
signal is one of an in-phase (I) and quadrature (Q) signal of the
radar sensor system.
[0007] In one aspect, at least one embodiment described herein
provides a radar sensor system with correction for leakage. The
system includes a transmitter and a receiver. The system also
includes a controller and/or a processor for controlling and
processing signals received by the receiver associated with the
radar sensor system. The controller and/or processor is configured
for defining an integration time period, the radar sensor system
being configured to integrate a detected signal during the
integration time period. The controller and/or processor is also
configured for dividing the integration time period into a first
sub-period and a second sub-period, the transmitter at least
partially transmitting a transmission radar signal during the first
sub-period of the integration time period, and the transmitter not
transmitting at all during the second sub-period of the integration
time period. The controller and/or processor is also configured for
integrating the detected signal during both the first sub-period of
the integration time period and the second sub-period of the
integration time period to generate a plurality of sampled
integrated values. The controller and/or processor is also
configured for subtracting a last sampled integrated value of the
second sub-period of the integration time period from a last
sampled integrated value of the first sub-period of the integration
time period to generate a corrected integrated value for the
integration time period.
[0008] Any of the aspects and/or embodiments described herein can
include one or more of the following embodiments. In some
embodiments, each integration time period is associated with a
transmitted radar signal of a different frequency. In some
embodiments, the system includes a second transmitter. In some
embodiments, the first transmitter at least partially transmits the
transmission radar signal during the first sub-period of the
integration time period and does not transmit at all during the
second sub-period of the integration time period. In some
embodiments, the second transmitter at least partially transmits a
second transmission radar signal during a first sub-period of a
second integration time period and does not transmit at all during
a second sub-period of the second integration time period. In some
embodiments, the first and second transmission radar signals are of
the same frequency.
[0009] In some embodiments, the controller and/or processor
integrates the detected signal from the receiver during both the
first sub-period of the second integration time period and the
second sub-period of the second integration time period to generate
a second plurality of sampled integrated values. In some
embodiments, the processor subtracts a last sampled integrated
value of the second sub-period of the second integration time
period from a last sampled integrated value of the first sub-period
of the second integration time period to generate a second
corrected integrated value for the integration time period. In some
embodiments, the first and second integration time periods define a
pair of integration time periods. In some embodiments, each of a
plurality of pairs of integration time periods is associated with a
different frequency of the first and second transmission radar
signals of the pair of integration time periods. In some
embodiments, the detected signal from the receiver is one of an
in-phase (I) and quadrature (Q) signal of the radar sensor
system.
[0010] In one aspect, at least one embodiment described herein
provides a method of correcting for leakage in a radar sensor
system. The method includes defining an integration time period,
the radar sensor system being configured to integrate a detected
signal during the integration time period. The method also includes
dividing the integration time period into a first sub-period and a
second sub-period, the radar sensor system at least partially
transmitting a transmission radar signal during the first
sub-period of the integration time period, and the radar sensor
system not transmitting at all during the second sub-period of the
integration time period. The method also includes integrating the
detected signal from the receiver during both the first sub-period
of the integration time period and the second sub-period of the
integration time period to generate a plurality of sampled
integrated values. The method also includes inverting a polarity of
a signal used in generating the detected signal during the second
sub-period of the integration time period. The method also includes
generating a corrected integrated value for the integration time
period using a last sampled integrated value of the plurality of
sampled integrated values.
[0011] Any of the aspects and/or embodiments described herein can
include one or more of the following embodiments. In some
embodiments, the method includes transmitting a transmission radar
signal during the integration time period. In some embodiments, the
signal used in generating the detected signal is an intermediate
frequency (IF) signal generated by the radar sensor system. In some
embodiments, a controllable switch is used to invert the polarity
of the signal used in generating the detected signal. In some
embodiments, the controllable switch is a double-pole, double-throw
(DPDT) switch. In some embodiments, the detected signal from the
receiver is one of an in-phase (I) and quadrature (Q) signal of the
radar sensor system.
[0012] In one aspect, at least one embodiment described herein
provides a radar sensor system with correction for leakage. The
system includes a transmitter and a receiver. The system also
includes a controllable circuit as a part of the receiver. The
system also includes a controller and/or processor for controlling
and processing signals from the receiver associated with the radar
sensor system. The controller and/or processor is configured for
defining an integration time period, the radar sensor system being
configured to integrate a detected signal during the integration
time period. The controller and/or processor is also configured for
dividing the integration time period into a first sub-period and a
second sub-period, the radar sensor system at least partially
transmitting a transmission radar signal during the first
sub-period of the integration time period, and the radar sensor
system not transmitting at all during the second sub-period of the
integration time period. The controller and/or processor is also
configured for integrating the detected signal from the receiver
during both the first sub-period of the integration time period and
the second sub-period of the integration time period to generate a
plurality of sampled integrated values. The controller and/or
processor is also configured for generating a control signal to
control the controllable circuit to invert a polarity of a signal
used in generating the detected signal during the second sub-period
of the integration time period. The controller and/or processor is
also configured for generating a corrected integrated value for the
integration time period using a last sampled integrated value of
the plurality of sampled integrated values.
[0013] Any of the aspects and/or embodiments described herein can
include one or more of the following embodiments. In some
embodiments, the transmitter transmits a transmission radar signal
during the integration time period. In some embodiments, the signal
used in generating the detected signal from the receiver is an
intermediate frequency (IF) signal generated by the radar sensor
system. In some embodiments, the controllable circuit is a
controllable switch used to invert the polarity of the signal used
in generating the detected signal. In some embodiments, the
controllable switch is a double-pole, double-throw (DPDT) switch.
In some embodiments, the detected signal is one of an in-phase (I)
and quadrature (Q) signal of the radar sensor system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present disclosure is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of embodiments of the
present disclosure, in which like reference numerals represent
similar parts throughout the several views of the drawings.
[0015] FIG. 1A is a schematic functional block diagram illustrating
a radar system in accordance with various embodiments.
[0016] FIG. 1B is a graphical illustration of ideal magnitude
versus azimuth angle antenna patterns for TX1 and TX2.
[0017] FIG. 1C is a graphical illustration of ideal phase
difference versus azimuth angle for TX1/TX2.
[0018] FIG. 2A is a graphical illustration of signal flows in the
radar system of FIG. 1A, operated in accordance with the prior
art.
[0019] FIG. 2B is a graphical illustration of measured magnitude
versus radiation angle antenna patterns for TX1 and TX2 in
accordance with the prior art operation of FIG. 2A.
[0020] FIG. 2C is a graphical illustration of measured phase
difference versus radiation angle for TX1/TX2 in accordance with
the prior art operation of FIG. 2A.
[0021] FIG. 2D is a graphical illustration of measured leakage
values, i.e., magnitude measured with both TX1 and TX2 off, versus
radiation angle for TX1 and TX2.
[0022] FIG. 3A is a logical flow diagram illustrating a logical
flow of a method for correcting leakage and/or distortion in
accordance with various embodiments.
[0023] FIG. 3B is a graphical illustration of the signal flows in
the radar system of FIG. 1A operated according to the method of
FIG. 3A in accordance with various embodiments.
[0024] FIG. 4A is a graphical illustration of subtracted magnitude
versus azimuth angle antenna patterns for TX1 and TX2 in accordance
with various embodiments.
[0025] FIG. 4B is a graphical illustration showing the subtracted
phase difference versus azimuth angle for TX1/TX2 in accordance
with various embodiments as compared to the prior art results of
FIG. 2C.
[0026] FIG. 5A is a schematic functional block diagram illustrating
another radar system in accordance with various embodiments.
[0027] FIG. 5B is a schematic functional block diagram illustrating
still another radar system in accordance with various
embodiments.
[0028] FIG. 5C is a graphical illustration of signal flows in a
radar system such as the radar systems of FIGS. 5A and 5B in
accordance with various embodiments.
DETAILED DESCRIPTION
[0029] The details described and illustrated herein are by way of
example and for purposes of illustrative description of the
exemplary embodiments only and are presented in the case of
providing what is believed to be the most useful and readily
understood description of the principles and conceptual aspects of
the disclosure. In this regard, no attempt is made to show
structural details of the subject matter in more detail than is
necessary for the fundamental understanding of the disclosure, the
description taken with the drawings making apparent to those
skilled in that how the several forms of the present disclosure may
be embodied in practice. Further, like reference numbers and
designations in the various drawings indicate like elements.
[0030] FIG. 1A illustrates an exemplary monopulse radar sensor
(radar system) 100, the sensor having two transmitter channels and
one receiver channel. Radar system 100 includes a microcontroller
unit (MCU) 101 which controls a phase-locked loop (PLL) 103 which
in turn transmits a signal to a voltage-controlled oscillator (VCO)
105, the output signal of which is then split at VCO power splitter
107. A portion of the output signal of the VCO 105 is routed to a
transmitter driver 111 and, when a transmitter switch 113 is
activated, the output signal is amplified by power amplifier 115,
split by antenna power splitter 117, and, upon activation of
respective trigger switches 119a, 119b, emitted by transmission
frequency (TX) antennas 121a, 121b, respectively.
[0031] The transmitted signal is then reflected by a target and
received by receiver frequency (RX) antenna 123 as a radio
frequency (RF) signal. The RF signal is then amplified using a low
noise amplifier 125, divided by divider 127, and fed into I-mixer
129 for processing of the in-phase component of the received signal
and Q-mixer 131 for processing the quadrature-phase component of
the RF signal.
[0032] Additionally, a second portion of the output signal of the
VCO 105 is routed through a local oscillator (LO) switch 133,
driven by a LO driver 135, fed into a LO splitter 137, and fed into
the I-mixer 129 and the Q-mixer 131. The I-mixer 129 and Q-mixer
131 then output intermediate frequency (IF) signals, which are each
amplified in a variable gain amplifier 139a, 139b, converted from a
differential signal to a single-ended signal in a
differential-to-single-ended transformer 140a, 140b, and fed into
an integrator 141a, 141b. The integrators 141a, 141b are
operatively connected to a sample and hold 143a and a sample and
hold reset 143b for sampling the signal. The outputs of the
integrators 141a, 141b are fed into a buffer circuit 145a, 145b and
then converted from an analog signal to a digital signal using
analog to digital converters (I-ADC 147, Q-ADC 149). The MCU 101
then provides the digital signal to the digital signal processor
(DSP) 151 for subsequent processing.
[0033] A completed monopulse radar system can also have one
transmitter channel and two receiver channels. Two detected signal
TX/RX1 and TX/RX2 will be processed in a similar way as TX1/RX and
TX2/RX as radar system 100.
[0034] FIG. 1B illustrates ideal magnitude versus azimuth angle
patterns (two-way antenna patterns) for each TX antenna 121a, 121b.
FIG. 1C illustrates an ideal phase difference (delta) versus
azimuth angle curve, where the phase difference is the difference
between the phase of a reflected signal received in response to
transmissions from a first TX antenna (TX1) 121a and the phase of a
reflected signal received in response to transmissions from a
second TX antenna (TX2) 121b. However, due to hardware limitations
and various leakage phenomena, actual measured results vary from
these ideal curves.
[0035] FIG. 2A illustrates a conventional approach of the
TX-control scheme for the two way signal detection to obtain the
amplitude with TX1 121a and TX2 121b as well as the TX1/TX2 phase
delta. In accordance with the conventional approach, TX-triggers
119a, 119b control the radar transmission power ON and OFF, and
logic 1 (high) means TX-ON, and 0 (low) means TX-OFF. The
conventional approach integrates over a first integration period
201 where the TX1 trigger 119a is set to ON, the TX2 trigger 119b
is set to OFF, and TX1 121a transmits a RF signal, and, then,
during a second integration period 203, the TX1 trigger 119a is set
to OFF, the TX2 trigger 119b is set to ON, and TX2 121b transmits a
RF signal. The system 100 then calculates the TX1/TX2 phase
difference during an inactive period 205 before looping to repeat
the process.
[0036] For both the first integration period 201 and the second
integration period 203, integrators 141a, 141b of the RX antenna
123 integrate for the entire designated integration time.
Traditionally, this is assumed to be necessary because the leakage
signal is present all the time. However, during a duty cycle of the
main transmission signal, the leakage signal ends up with a higher
integration gain than the main signal. Therefore, the unwanted
leakage signal is enhanced and makes the distortion of the expected
antenna patterns and the TX1/TX2 phase difference curve much worse,
as described below with reference to FIGS. 2B-2D.
[0037] FIGS. 2B-2C illustrate the measured antenna patterns of TX1
121a and TX2 121b as well as the TX1/TX2 phase delta curve of the
radar system 100 of FIG. 1A as measured by the conventional
approach. As shown in FIG. 2B, the 2-way TX1 121a and TX2 121b
antenna patterns are very different from each other in amplitude.
For example, the amplitude difference for the radiation angle
beyond +/-45 degree reaches over 12-dB. The majority of the
differences between measured amplitudes of TX1 121a and measured
amplitudes of TX2 121b are caused by differing leakage levels,
especially the difference in leakage signal phase distributions
when TX1 121a and/or TX2 121b is ON.
[0038] FIG. 2D illustrates the measured two-way leakage patterns of
the radar system 100. Comparing the data shown in FIG. 2D with the
data shown in FIG. 2B, it is apparent that the leakage level is
high relative to the measured magnitude and, for some azimuth
angles, e.g. beyond +/-30 degrees, the leakage magnitude associated
with TX2 121b is higher than the measured magnitude of the
radiation pattern of TX1 121a.
[0039] As shown in FIG. 2C the TX1/TX2 phase delta curve for
azimuth angle less than -30 degrees exhibits flatness and for
azimuth angle greater than +30 degrees exhibits ripple and phase
wrapping. These distortions are primarily due to the presence of
the unwanted leakage signal. Because the TX1/TX2 phase delta curve
is widely used to detect target bearing information, such
distortion of the phase delta curve results in radar target report
errors, in some cases to the point of impairing basic radar
functions.
[0040] Described herein are devices and techniques for correcting
leakage and/or distortion in radar systems implemented by way of
software solutions and by way of circuitry hardware solutions.
Exemplary Embodiments
[0041] FIGS. 3A-3B illustrate an approach of the TX-control scheme
for the corrected two way signal detection to obtain the amplitude
with TX1 121a and TX2 121b as well as the TX1/TX2 phase delta curve
according to some exemplary embodiments. In accordance with this
approach, TX-triggers 119a, 119b control the radar transmission
power ON and OFF, and logic 1 (high) means TX-ON, and 0 (low) for
TX-OFF. The software approach integrates over a subdivided first
integration period 301 where the TX1 trigger 119a is set to ON for
a TX1-ON sub-period 301a while the TX2 trigger 119b is set to OFF
and TX1 121a transmits a RF signal. The TX1 trigger 119a is then
set to OFF for a TX1-OFF sub-period 301b while the TX2 trigger 119b
remains OFF so that both TX1 121a and TX2 121b are off and neither
transmits a RF signal.
[0042] Then, the approach integrates over a subdivided second
integration period 303 where the TX2 trigger 119b is set to ON for
a TX2-ON sub-period 303a while the TX1 trigger 119a remains OFF,
and TX2 121b transmits a RF signal. The TX2 trigger 119a is then
set to OFF for a TX2-OFF sub-period 303b while the TX1 trigger 119a
remains OFF so that both TX1 121a and TX2 121b are off and neither
transmits a RF signal.
[0043] The system 100 then calculates the TX1/TX2 phase difference
during an inactive period 305 before looping 307, 309 to repeat the
process. After each frequency point has been integrated, the
results are then provided to the digital signal processor 151 for
subsequent processing.
[0044] Because each integration period, e.g., first integration
period 301 or second integration period 303, is divided into two
equal-length sub-periods with the first sub-period TX-ON 301a, 303a
and the second sub-period TX-OFF 301b, 303b the integrations of the
detected signal and/or interference can be done separately for
those two sub-periods. The integration results from the TX-OFF
301b, 303b sub-period (labeled "interference (offset)" in FIG. 3B)
are then subtracted from the TX-ON 301a, 303a sub-period
integration results (labeled "actual detection" in FIG. 3B) in the
data processing from a digital signal processor embedded in the
radar, e.g. DSP 151 as shown in FIG. 1A. This subtraction produces
clean, signal-only results (labeled "signal only" in FIG. 3B).
[0045] As described in FIG. 3A, the amplitude subtraction results,
e.g., as shown in FIG. 4A, for each integration period 301, 303 are
actually determined by subtracting the results as sampled and held
(stored) by the sample and hold 143a and the sample and hold reset
143b at the last point of each integration sub-period 301a, 301b,
303a, 303b. Therefore, the results for the first integration period
301 are determined by subtracting the amplitude of the last point
of the TX1-OFF sub-period 301b from the amplitude of the last point
of the TX1-ON sub-period 301a.
[0046] Comparing the antenna patterns of TX1 121a and TX2 121b of
the exemplary embodiments described in connection with FIGS. 3A and
3B (see FIG. 4A) with the conventional approach antenna patterns
(see FIG. 2B), it is clear that the approach of the exemplary
embodiments described in connection with FIGS. 3A and 3B more
closely mirrors the ideal magnitude versus azimuth angle patterns
(two-way antenna patterns) shown in FIG. 1B. Additionally, the
2-way TX1 121a and TX2 121b antenna patterns are much closer to
each other in amplitude because the leakage and interference have
been cancelled.
[0047] Comparing the TX1/TX2 phase delta curve of the exemplary
embodiments described in connection with FIGS. 3A and 3B (see
"corrected phase delta" of FIG. 4B) with the conventional approach
TX1/TX2 phase delta curve (see FIG. 2C or "uncorrected phase delta"
of FIG. 4B), it is clear that the approach of the exemplary
embodiments described in connection with FIGS. 3A and 3B more
closely mirrors the ideal phase difference (delta) versus azimuth
angle curve shown in FIG. 1C. Additionally, the prominent ripple
and phase wrapping of the conventional approach have been
significantly reduced by the approach of the exemplary embodiments
described in connection with FIGS. 3A and 3B. Therefore, detected
target bearing information is more accurate, reducing radar target
report errors and preventing impairment of basic radar functions.
Advantageously, the approach of the exemplary embodiments described
in connection with FIGS. 3A and 3B can be implemented without
changing any pre-existing circuitry hardware in the radar
system.
[0048] According to other exemplary embodiments, a pair double-pole
double throw (DPDT) switch can, in accordance with various
embodiments, be added in the differential IF-chain of the receiver
I-/Q-circuits. These DPDTs can be arranged anywhere between the
differential I-/Q-mixer outputs and the inputs of the
differential-to-single-ended transformer circuit. In these
embodiments there is no sample-and-hold reset required between the
TX-ON and TX-OFF as in the exemplary embodiments described in
connection with FIGS. 3A and 3B. Instead, an IF-polarity control
signal is used to switch I-/Q-signal polarities and a combined
integration process is used for both the TX-ON and TX-OFF
states.
[0049] FIG. 5A illustrates a modified radar system with a single
ended IF-chain 500 for correcting leakage and/or distortion in
radar systems such as the monopulse radar sensor (radar system) 100
shown in FIG. 1A, according to these latter exemplary embodiments.
As shown in FIG. 5A, radar systems with a single ended IF-chain 500
can, in accordance with various embodiments, be implemented by
removing the variable gain amplifiers 139a, 139b of the radar
system 100 and replacing them with a single-ended double-pole
double-throw (DPDT) circuit. The single-ended DPDT circuit, in
accordance with various embodiments, can include DPDT switch pairs
503a, 503b configured to receive the output IF signals from the
I-mixer 129 and the Q-mixer 131 and variable gain amplifier pairs
505+/-, 507+/- configured to receive positive and negative outputs
from the DPDT switch pairs 503a, 503b and output to the
differential-to-single-ended transformers 140a, 140b, which feed
into the integrators 141a, 141b.
[0050] FIG. 5B illustrates a radar system with a differential
IF-chain 501 for correcting leakage and/or distortion in radar
systems such as the monopulse radar sensor (radar system) 100 shown
in FIG. 1A, according to these latter embodiments. As shown in FIG.
5B, modified radar systems 501 can, in accordance with various
embodiments, be implemented by removing the variable gain
amplifiers 139a, 139b and the integrators 141a, 141b of the radar
system 100 and replacing them with a differential double-pole
double-throw (DPDT) circuit. As shown in FIG. 5B, the differential
DPDT circuit, in accordance with various embodiments, can include
DPDT switch pairs 503a, 503b configured to receive the output IF
signals from the I-mixer 129 and the Q-mixer 131, variable gain
amplifier pairs 505+, 505-, 507+, 507- configured to receive
positive and negative outputs from the DPDT switch pairs 503a,
503b, and differential integrator pairs 509a, 509b configured to
receive outputs from the variable gain amplifier pairs 505+, 505-,
507+, 507- and output to the differential-to-single-ended
transformers 140a, 140b, which feed into the buffer circuits 145a,
145b.
[0051] FIG. 5C illustrates an approach of the TX-control scheme for
the corrected two way signal detection to obtain the amplitude with
TX1 121a and TX2 121b as well as the TX1/TX2 phase delta curve
according to the exemplary embodiments described in connection with
FIGS. 5A and 5B. In accordance with these exemplary embodiments,
TX-triggers 119a, 119b control the radar transmission power ON and
OFF, and logic 1 (high) means TX-ON, and 0 (low) means TX-OFF. The
approach of the exemplary embodiments described in connection with
FIGS. 5A and 5B integrates over a subdivided first integration
period 591 where, for a TX1-POS sub-period 591a the TX1 trigger
119a is set to ON, the DPDT switch pairs 503a, 503b are set to
positive polarity, the TX2 trigger 119b is set to OFF, and TX1 121a
transmits a RF signal. Then, for a TX1-NEG sub-period 591b, the TX1
trigger 119a is set to OFF and the DPDT switch pairs 503a, 503b are
switched to negative polarity while the TX2 trigger 119b remains
OFF so that both TX1 121a and TX2 121b are off and neither
transmits a RF signal.
[0052] Then, the approach of the exemplary embodiments described in
connection with FIGS. 5A and 5B integrates over a subdivided second
integration period 593 where, for a TX2-POS sub-period 593a the TX2
trigger 119b is set to ON, the DPDT switch pairs 503a, 503b are set
to positive polarity, the TX1 trigger 119a is set to OFF, and TX2
121b transmits a RF signal. Then, for a TX2-NEG sub-period 593b,
the TX2 trigger 119b is set to OFF and the DPDT switch pairs 503a,
503b are switched to negative polarity while the TX1 trigger 119a
remains OFF so that both TX1 121a and TX2 121b are off and neither
transmits a RF signal.
[0053] The modified radar system 500, 501 then calculates the
TX1/TX2 phase difference during an inactive period 595 before
looping to repeat the process. After each frequency point has been
integrated, the results are then provided to the digital signal
processor 151 for subsequent processing.
[0054] As shown in FIG. 5C, by switching the I/Q signal polarity
control, the interference (leakage signal) reverses direction,
thereby causing the integrated I/Q signal output to go in a first
direction, e.g., increasing magnitude as shown in FIG. 5C, during
the TX1-POS 591a and TX2-POS 593a sub-periods, while the I/Q signal
output goes in the opposite direction, e.g., decreasing magnitude
as shown in FIG. 5C, during the TX1-NEG 591b and TX2-NEG 593b
sub-periods. Because there is no sample and hold reset between the
sub-periods, e.g., between TX1-POS 591a and TX1-NEG 591b, the peak
I/Q signal output is a starting point for the negative polarity
integration. Because no signal is transmitted during the negative
polarity integration, the peak I/Q signal output is reduced only by
the decreasing interference signal and the interference
contribution to the integration output is cancelled out by the end
of the integration cycle. Therefore, when the signal output is
sampled at the end of the integration period 591, 593, the signal
output is equal to the clean signal output. Therefore, results
equivalent to those illustrated in FIGS. 4A-4B can be achieved
through the approach of the exemplary embodiments described in
connection with FIGS. 5A-5C. Advantageously, the exemplary
embodiments described in connection with FIGS. 5A-5C described
herein require no extra data processing to remove the leakage
contribution. Additionally, in accordance with various embodiments,
by integrating the DPDT circuitry of the exemplary embodiments
described in connection with FIGS. 5A-5C into an application
specific integrated circuit (ASIC) of the modified radar system
500,501, increases in system production costs and data process
complexity can be avoided.
[0055] In theory, reduction of the active transmission signal time
by half could, without offsetting considerations, cause a
significant and disadvantageous reduction in signal to noise ratio
(SNR). However, because the overall transmitted RF-signal is
decreased, the transmitted RF-power can be increased to meet the
regulatory limit of the root mean square (rms) RF-power if no peak
power violation is caused, thereby mitigating the reduction in SNR.
Moreover, by subtracting or negating the leakage contribution, the
exemplary embodiments described herein can also suppress the noise
floor caused by the interference. Therefore, the actual signal SNR
reduction caused by implementing the software solution will, in a
worst case scenario, result in minimal SNR reduction and, in
accordance with various embodiments, can increase SNR. Further
advantageously, the exemplary embodiments described herein reduce
the DC-offset of the IF-signal, which, in some cases, would
otherwise paralyze the whole system. Also advantageously, the
direct radar target bearing report accuracy is improved by the
cancellation or reduction of the unwanted leakage, distortion,
and/or other interference signal.
[0056] Various embodiments of the above-described systems and
methods may be implemented in digital electronic circuitry, in
computer hardware, firmware, and/or software. The implementation
can be as a computer program product (i.e., a computer program
tangibly embodied in an information carrier). The implementation
can, for example, be in a machine-readable storage device and/or in
a propagated signal, for execution by, or to control the operation
of, data processing apparatus. The implementation can, for example,
be a programmable processor, a computer, and/or multiple
computers.
[0057] A computer program can be written in any form of programming
language, including compiled and/or interpreted languages, and the
computer program can be deployed in any form, including as a
stand-alone program or as a subroutine, element, and/or other unit
suitable for use in a computing environment. A computer program can
be deployed to be executed on one computer or on multiple computers
at one site.
[0058] Method steps can be performed by one or more programmable
processors and/or controllers executing a computer program to
perform functions of the invention by operating on input data and
generating output. Method steps can also be performed by, and an
apparatus can be implemented as, special purpose logic circuitry.
The circuitry can, for example, be a FPGA (field programmable gate
array) and/or an ASIC (application-specific integrated circuit).
Modules, subroutines, and software agents can refer to portions of
the computer program, the processor, the special circuitry,
software, and/or hardware, e.g., a controller such as a
microcontroller, that implements that functionality.
[0059] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor receives instructions and
data from a read-only memory or a random access memory or both. The
essential elements of a computer are a processor for executing
instructions and one or more memory devices for storing
instructions and data. Generally, a computer can be operatively
coupled to receive data from and/or transfer data to one or more
mass storage devices for storing data, e.g., magnetic,
magneto-optical disks, or optical disks.
[0060] Data transmission and instructions can also occur over a
communications network. Information carriers suitable for embodying
computer program instructions and data include all forms of
non-volatile memory, including by way of example semiconductor
memory devices. The information carriers can, for example, be
EPROM, EEPROM, flash memory devices, magnetic disks, internal hard
disks, removable disks, magneto-optical disks, CD-ROM, and/or
DVD-ROM disks. The processor and the memory can be supplemented by
and/or incorporated in special purpose logic circuitry.
[0061] To provide for interaction with a user, the above described
techniques can be implemented on a computer having a display
device. The display device can, for example, be a cathode ray tube
(CRT) and/or a liquid crystal display (LCD) monitor. The
interaction with a user can, for example, be a display of
information to the user and a keyboard and a pointing device, e.g.,
a mouse or a trackball, by which the user can provide input to the
computer, e.g., interact with a user interface element. Other kinds
of devices can be used to provide for interaction with a user.
Other devices can, for example, be feedback provided to the user in
any form of sensory feedback, e.g., visual feedback, auditory
feedback, or tactile feedback. Input from the user can, for
example, be received in any form, including acoustic, speech,
and/or tactile input.
[0062] The above described techniques can be implemented in a
distributed computing system that includes a back-end component.
The back-end component can, for example, be a data server, a
middleware component, and/or an application server. The above
described techniques can be implemented in a distributing computing
system that includes a front-end component. The front-end component
can, for example, be a client computer having a graphical user
interface, a Web browser through which a user can interact with an
example implementation, and/or other graphical user interfaces for
a transmitting device. The components of the system can be
interconnected by any form or medium of digital data communication,
e.g., a communication network. Examples of communication networks
include a local area network (LAN), a wide area network (WAN), the
Internet, wired networks, and/or wireless networks.
[0063] The system can include clients and servers. A client and a
server are generally remote from each other and typically interact
through a communication network. The relationship of client and
server arises by virtue of computer programs running on the
respective computers and having a client-server relationship to
each other.
[0064] Packet-based networks can include, for example, the
Internet, a carrier internet protocol (IP) network, e.g., local
area network (LAN), wide area network (WAN), campus area network
(CAN), metropolitan area network (MAN), home area network (HAN)), a
private IP network, an IP private branch exchange (IPBX), a
wireless network, e.g., radio access network (RAN), 802.11 network,
802.16 network, general packet radio service (GPRS) network,
HiperLAN), and/or other packet-based networks. Circuit-based
networks can include, for example, the public switched telephone
network (PSTN), a private branch exchange (PBX), a wireless
network, e.g., RAN, Bluetooth, code-division multiple access (CDMA)
network, time division multiple access (TDMA) network, global
system for mobile communications (GSM) network), and/or other
circuit-based networks.
[0065] The computing system can also include one or more computing
devices. A computing device can include, for example, a computer, a
computer with a browser device, a telephone, an IP phone, a mobile
device, e.g., cellular phone, personal digital assistant (PDA)
device, laptop computer, electronic mail device, and/or other
communication devices. The browser device includes, for example, a
computer, e.g., desktop computer, laptop computer, with a World
Wide Web browser, e.g., Microsoft.RTM. Internet Explorer.RTM.
available from Microsoft Corporation, Mozilla.RTM. Firefox
available from Mozilla Corporation. The mobile computing device
includes, for example, a Blackberry.RTM., iPAD.RTM., iPhone.RTM. or
other smartphone device.
[0066] Whereas many alterations and modifications of the disclosure
will no doubt become apparent to a person of ordinary skill in the
art after having read the foregoing description, it is to be
understood that the particular embodiments shown and described by
way of illustration are in no way intended to be considered
limiting. Further, the subject matter has been described with
reference to particular embodiments, but variations within the
spirit and scope of the disclosure will occur to those skilled in
the art. It is noted that the foregoing examples have been provided
merely for the purpose of explanation and are in no way to be
construed as limiting of the present disclosure.
[0067] While the present disclosure has been described with
reference to example embodiments, it is understood that the words
that have been used herein, are words of description and
illustration, rather than words of limitation. Changes may be made,
within the purview of the appended claims, as presently stated and
as amended, without departing from the scope and spirit of the
present disclosure in its aspects.
[0068] Although the present disclosure has been described herein
with reference to particular means, materials and embodiments, the
present disclosure is not intended to be limited to the particulars
disclosed herein; rather, the present disclosure extends to all
functionally equivalent structures, methods and uses, such as are
within the scope of the appended claims.
* * * * *