U.S. patent application number 17/322352 was filed with the patent office on 2022-01-06 for digital range gated radio frequency sensor.
This patent application is currently assigned to RESMED SENSOR TECHNOLOGIES LIMITED. The applicant listed for this patent is RESMED SENSOR TECHNOLOGIES LIMITED. Invention is credited to Stephen McMahon.
Application Number | 20220000384 17/322352 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-06 |
United States Patent
Application |
20220000384 |
Kind Code |
A1 |
McMahon; Stephen |
January 6, 2022 |
DIGITAL RANGE GATED RADIO FREQUENCY SENSOR
Abstract
A digitally implemented radio frequency sensor for physiology
sensing may be configured to generate oscillation signals for
emitting radio frequency pulses for range gated sensing. The sensor
may include a radio frequency transmitter configured to emit the
pulses and a receiver configured to receive reflected ones of the
emitted radio frequency pulses under control of a microcontroller.
The received pulses may be processed by the microcontroller to
detect physiology characteristics such as motion, sleep,
respiration and/or heartbeat. The microcontroller may be configured
to generate timing pulses such as with a pulse generator for
transmission of radio frequency sensing pulses. The microprocessor
may sample received signals, such as in phase and quadrature phase
analogue signals, to implement digital demodulation and baseband
filtering of the received signals.
Inventors: |
McMahon; Stephen; (Dundrum,
IE) |
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Applicant: |
Name |
City |
State |
Country |
Type |
RESMED SENSOR TECHNOLOGIES LIMITED |
Clonskeagh |
|
IE |
|
|
Assignee: |
RESMED SENSOR TECHNOLOGIES
LIMITED
Clonskeagh
IE
|
Appl. No.: |
17/322352 |
Filed: |
May 17, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15751683 |
Feb 9, 2018 |
11033196 |
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PCT/EP2016/069413 |
Aug 16, 2016 |
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17322352 |
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62205129 |
Aug 14, 2015 |
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International
Class: |
A61B 5/0507 20060101
A61B005/0507; A61B 5/11 20060101 A61B005/11; A61B 5/00 20060101
A61B005/00; G01S 13/18 20060101 G01S013/18; G01S 13/56 20060101
G01S013/56; G01S 7/288 20060101 G01S007/288; G01S 7/282 20060101
G01S007/282; H03B 5/18 20060101 H03B005/18; G01S 13/02 20060101
G01S013/02 |
Claims
1. Digital radio frequency motion sensor apparatus comprising: a
radio frequency transmitter, the transmitter configured to emit
radio frequency signals, the radio frequency signals comprising
pulses; and a receiver configured to receive reflected ones of the
emitted radio frequency signals, a microcontroller configured to
control a timing of the pulses; a pulse generator configured to
generate signal pulses in response to the timing; an oscillator;
and a switched circuit coupled to the pulse generator and the
oscillator, wherein the microcontroller is configured to control
digital filtering of one or more signals or baseband signals from
the receiver, and wherein the microcontroller is configured to
detect movement of a user with a plurality of different sensing
ranges.
2. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is further configured to control
demodulating a combined signal of emitted and received signals to
determine a baseband signal, and modulating the baseband signal to
produce an intermediate frequency (IF) signal at the receiver.
3. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is further configured to control
digital demodulation of an intermediate frequency (IF) signal after
a stage of IF signal amplification to produce a baseband signal at
the receiver.
4. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is further configured to control
digital amplification of one or more baseband signals from the
receiver.
5. The digital radio frequency motion sensor apparatus of claim 1
wherein the pulse generator comprises a logic gate circuit
configured to receive a timing signal generated by the
microcontroller.
6. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is coupled with the receiver to sample
a signal from the receiver representing phase and/or magnitude
differences between received reflected ones of emitted radio
frequency pulses and emitted radio frequency pulses.
7. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is configured to digitally demodulate
the signal from the receiver.
8. The digital radio frequency motion sensor apparatus of claim 1
wherein the receiver generates in phase and quadrature phase
signals for sampling at inputs to the microcontroller.
9. The digital radio frequency motion sensor apparatus of claim 1
wherein the receiver comprises a mixer, wherein the microcontroller
controls timing of the mixer's operation.
10. The digital radio frequency motion sensor apparatus of claim 9
wherein the mixer comprises a switched magnitude detector.
11. The digital radio frequency motion sensor apparatus of claim 1
wherein the microcontroller is configured to generate an indicator
of any one or more of respiration, sleep and heart rate information
from one or more digitally demodulated signals from the
receiver.
12. The digital radio frequency motion sensor apparatus of claim 1,
wherein the microcontroller is configured to trigger sensor
operation by turning the sensor apparatus on and off.
13. The digital radio frequency motion sensor apparatus of any of
claim 1, wherein the microcontroller is configured to control
storing of data from received signals in epochs.
14. The digital radio frequency motion sensor apparatus of claim
13, further comprising a memory, wherein the memory stores the
epochs.
15. The digital radio frequency motion sensor apparatus of claim 1
wherein the sensor apparatus is configured for wireless
transmission from the sensor apparatus of data derived from
received signals.
16. The digital radio frequency motion sensor apparatus of claim 1
further comprising a digital or analogue output connection.
17. The digital radio frequency motion sensor apparatus of claim
16, wherein the digital or analogue output connection is a RS232,
serial or USB connection.
18. The digital radio frequency motion sensor apparatus of claim 1
further comprising an analog output, and wherein the
microcontroller is configured to convert digital signals received
from the receiver into analogue signals for output via the analog
output.
19. The digital radio frequency motion sensor apparatus of claim 18
wherein the analog signals comprise a pulse width modulated
signal.
20. The digital radio frequency motion sensor apparatus of claim 1
further comprising a housing, wherein the sensor is contained
within the housing.
21. The digital radio frequency motion sensor apparatus of claim 1
wherein the transmitter and receiver comprise a single printed
circuit board and wherein the microcontroller is a chip coupled to
the single printed circuit board.
22. The digital radio frequency motion sensor apparatus of claim 1
wherein the receiver comprises two detectors for mixing emitted
radio frequency (RF) pulses and received reflected ones of emitted
radio frequency pulses, the two detectors including one magnitude
detector for in-phase signals and one magnitude detector for
quadrature phase signals, wherein each magnitude detector is
configured to switch on, at a first defined point in time t1 and
for a first defined time duration T1 within each one of a first
number of RF pulses, to effect range gating.
23. The digital radio frequency motion sensor apparatus of claim
22, wherein each detector is switched at a second defined point in
time t0 for a second defined time duration T0 within each one of a
second number of RF pulses, the first defined point in time t1
being different from the second defined point in time t0; and
wherein each detector modulates the mixed pulses at an intermediate
frequency that is higher than a baseband frequency.
24. The digital radio frequency motion sensor apparatus of claim
23, wherein each detector alternates between being switched on at
the first defined point in time t1, during the first number of RF
pulses, and being switched on at the second defined point in time
t0, during the second number of RF pulses.
25. The digital radio frequency motion sensor apparatus of claim
22, wherein the detectors are magnitude detectors.
26. The digital radio frequency motion sensor apparatus of claim
23, wherein the receiver further comprises, for each detector, a
pre-amplifier or an amplifier for amplifying the modulated mixed
pulses at the intermediate frequency.
27. The digital radio frequency motion sensor apparatus of claim
26, wherein the microcontroller is further configured to demodulate
the amplified modulated mixed pulses into baseband signals.
28. The digital radio frequency motion sensor apparatus of claim 1,
wherein the receiver and radio frequency transmitter are digitally
controlled by the microcontroller, to automate changing of at least
some of their parameters.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/751,683, filed on Feb. 9, 2018, which is
national phase entry under 35 U.S.C. .sctn. 371 of International
Application No. PCT/EP2016/069413, filed Aug. 16, 2016, published
in English, which claims priority from U.S. Provisional Patent
Application No. 62/205,129, filed Aug. 14, 2015, all of which are
incorporated herein by reference.
FIELD OF THE TECHNOLOGY
[0002] The present technology relates to radio frequency sensors
for detection of characteristics of moving objects and living
subjects. More particularly, it relates to circuits of such
sensors, such as range gated radio frequency motion sensors
implemented digitally with microcontrollers, with particular
emphasis on detecting physiological characteristics of a user.
BACKGROUND OF THE TECHNOLOGY
[0003] Continuous wave (CW) Doppler radar motion sensors emit a
continuous wave radio frequency (RF) carrier signal and mix the
transmitted RF signal with the return echoes to produce a
difference frequency equal to the Doppler shift produced by a
moving target. These sensors do not have a definite range limit
(i.e., they can receive signals for both near and far objects, with
the received signal being a function of radar cross section). This
can lead to false triggers, i.e., motion artefact interference.
They may also have an undesirably high sensitivity at close range
that leads to false triggering.
[0004] A pulse Doppler motion sensor is described in U.S. Pat. No.
4,197,537 to Follen et al. A short pulse is transmitted and its
echo is self-mixed with the transmitted pulse. The pulse width
defines the range-gated region. When the transmit pulse ends,
mixing ends and target reflections arriving after the end of the
transmit pulse are not mixed and are thereby gated out.
[0005] A Differential pulse motion sensor disclosed in U.S. Pat.
No. 5,966,090, "Differential Pulse Radar Motion Sensor," to McEwan,
alternately transmits two pulse widths. It then subtracts the
responses from each width to produce a range gated sensing region
having a fairly constant response versus range.
[0006] Impulse radar, such as that described in U.S. Pat. No.
5,361,070, "Ultra-Wideband Radar Motion Sensor," to McEwan produces
a very narrow sensing region that is related to the transmitted
impulse width. A two-pulse radar motion sensor, as described in
U.S. Pat. No. 5,682,164, "Pulse Homodyne Field Disturbance Sensor,"
to McEwan, transmits a first pulse and after a delay generates a
second pulse that mixes with echoes from the first pulse. Thus a
range gated sensing band is formed with defined minimum and maximum
ranges. UWB radar motion sensors have the disadvantage of not
having global RF regulatory acceptance as an intentional radiator.
They also can have difficulty sensing objects at medium ranges and
in some embodiments can be prone to RF interference.
[0007] A modulated pulse sensor is described in U.S. Pat. No.
6,426,716 to McEwan. The range gated microwave motion sensor
includes adjustable minimum and maximum detection ranges. The
apparatus includes an RF oscillator with associated pulse
generating and delay elements to produce the transmit and mixer
pulses, a single transmit (TX)/receive (RX) antenna or a pair of
separate TX and RX antennas, and an RF receiver, including a
detector/mixer with associated filtering, amplifying and
demodulating elements to produce a range gated signal from the
mixer and echo pulses.
[0008] In U.S. Pat. No. 7,952,515, McEwan discloses a particular
holographic radar. It adds a range gate to holographic radar to
limit response to a specific downrange region. McEwan states that
cleaner, more clutter-free radar holograms of an imaged surface can
be obtained, particularly when penetrating materials to image
interior image planes, or slices. The range-gating enables stacked
hologram technology, where multiple imaged surfaces can be stacked
in the downrange direction.
[0009] In U.S. Patent Application Publ. no. 2010/0214158, McEwan
discloses an RF magnitude sampler for holographic radar. McEwan
describes that the RF magnitude sampler can finely resolve
interferometric patterns produced by narrowband holographic pulse
radar.
[0010] In U.S. Patent Application Publ. no. US-2014-0024917-A1,
McMahon, et al. teach an analog range gated radio frequency
physiology sensor.
[0011] There may be a need to improve sensors for pulse radio
frequency sensing such as in the case of physiological
characteristic detection.
SUMMARY OF THE TECHNOLOGY
[0012] One aspect of some embodiments of the present technology
relates to an improved circuit design with digital components for a
sensor for detecting physiology characteristics with radio
frequency signals.
[0013] Another aspect of some embodiments of the technology relates
to such a sensor with a circuit configured to generate pulsed radio
frequency (RF) signals such as for range gating.
[0014] A still further aspect of some embodiments of the technology
relates to a sensor with a circuit with improved oscillator
design.
[0015] An additional aspect of some embodiments of the technology
relates to such a sensor configured for improved RF oscillator
frequency stability that also maintains fast switching
characteristics desirable for range gating.
[0016] A further object of some embodiments of the technology is to
provide an RF sensor that is amenable to radio frequency regulatory
requirements as an intentional radiator.
[0017] Some embodiments of the present technology may include a
radio frequency motion sensor. The sensor may include a radio
frequency transmitter. The transmitter may be configured to emit
radio frequency pulses. The sensor may also include a receiver
configured to receive reflected ones of the emitted radio frequency
pulses. The radio frequency transmitter may include a
microcontroller. The microcontroller may be configured to generate
timing pulses. The radio frequency transmitter may also include a
pulse generator configured to generate signal pulses in response to
receiving the timing pulses; an oscillator, such as a dielectric
resonator, configured to generate a stable radio frequency
oscillating signal; and a switched circuit coupled to the pulse
generator and the oscillator. The switch circuit may be configured
to generate a pulsed radio frequency oscillating signal having a
dominant frequency derived from the oscillator.
[0018] Some versions of the present technology may include a
digital radio frequency motion sensor. The sensor may include a
radio frequency transmitter configured to emit radio frequency
pulses. The sensor may include a receiver configured to receive
reflected ones of the emitted radio frequency pulses. The radio
frequency transmitter may include a microcontroller configured to
generate timing pulses; a pulse generator configured to generate
signal pulses in response to the timing pulses; an oscillator
configured to generate a stable radio frequency oscillating signal;
and a switched circuit coupled to the pulse generator and the
oscillator. The switch circuit may be configured to generate a
pulsed radio frequency oscillating signal whose frequency is
derived from the oscillator. The oscillator comprises a dielectric
resonator.
[0019] In some cases, the pulse generator may include a logic gate
circuit configured to receive a timing signal generated by the
microcontroller. The microcontroller may be coupled with the
receiver to sample a signal from the receiver representing phase
and/or magnitude differences between the received reflected ones of
the emitted radio frequency pulses and the emitted radio frequency
pulses. The receiver may include a mixer. The mixer may include a
switched magnitude detector. The microcontroller may control timing
of the mixer's operation. The microcontroller may be configured to
digitally control the timing of the mixer. The microcontroller may
be configured to digitally demodulate the signal from the receiver.
In some cases, the receiver may generate in phase and quadrature
phase signals for sampling at inputs to the microcontroller. In
some versions of the sensor, the microcontroller may be configured
to generate an indicator of any one or more of respiration, sleep
and heart rate information from one or more digitally demodulated
signals from the receiver.
[0020] In some cases, the microcontroller may be configured to
trigger sensor operation by turning the sensor on and off. The
microcontroller may be configured to control storing of data from
received signals in epochs. The sensor may also include a memory,
wherein the memory stores the epochs. The memory may be or include
one or more of SD cards, microSD cards, and flash. The memory may
be integrated into the microcontroller. The sensor is configured
for wireless transmission from the sensor of data derived from
received signals. The wireless transmission may include NFC
communications.
[0021] The microcontroller may be configured to digitally filter
one or more signals from the receiver. The microcontroller maybe
configured to digitally filter one or more baseband signals from
the receiver. The microcontroller may be configured to digitally
amplify one or more baseband signals from the receiver. In some
cases, sensor may also include a digital or analogue output
connection. The digital or analogue output connection may be a
RS232, serial or USB connection. The sensor may include an analog
output, and the microcontroller may be configured to convert
digital signals received from the receiver into analogue signals
for output via the analog output. The analog signals comprise a
pulse width modulated signal.
[0022] The sensor may also include a housing, wherein the sensor is
contained within the housing. The transmitter and receiver may have
a single printed circuit board and the microcontroller may be a
chip coupled, e.g., soldered, to the printed circuit board.
[0023] The receiver may comprise two detectors for mixing the
emitted radio frequency (RF) pulses and the received reflected ones
of the emitted radio frequency pulses. The two detectors may
include one magnitude detector for in-phase signals and one
magnitude detector for quadrature phase signals. Each magnitude
detector may be configured to switch on, at a first defined point
in time t1 and for a first defined time duration T1 within each one
of a first number of RF pulses, to effect range gating capability
of the sensor. In some cases each detector may switched at a second
defined point in time t0 for a second defined time duration T0
within each one of a second number of RF pulses, the first defined
point in time t1 being different from the second defined point in
time t0. In some versions, the first number of RF pulses may be
equal to the second number of RF pulses and/or the first or the
second number of RF pulses may be a number of consecutive
pulses.
[0024] The detectors may each modulate the mixed pulses at an
intermediate frequency that is higher than a baseband frequency.
Each detector may alternate between being switched on at the first
defined time t1, during the first number of RF pulses, and being
switched on at the second defined time t0, during the second number
of further RF pulses. In some instances the first time duration T1
is equal to second time duration T0. The first defined time t1 can
be different from the second defined time t0.
[0025] In some cases the receiver may further include a
pre-amplifier or an amplifier for amplifying the modulated mixed
pulses at the intermediate frequency.
[0026] The microcontroller may be configured to demodulate the
amplified modulated mixed pulses into baseband signals. The
microcontroller may digitally control the receiver and radio
frequency transmitter to automate the change of at least some of
their parameters.
[0027] Some versions of the present technology may include a
circuit for generating signals to produce radio frequency pulses
for range gated physiology sensing. The circuit may include a
microcontroller, which may be configured to generate timing pulses.
The circuit may include a pulse generator configured to generate
signal pulses in response to receiving timing pulses, such as form
the microcontroller. The circuit may include an oscillator
configured to generate a radio frequency oscillating signal. The
circuit may include a switched circuit coupled to the pulse
generator and the oscillator. The switched circuit may be
configured to generate a pulsed radio frequency oscillating signal
in accordance with the signal pulses and radio frequency
oscillating signal. The circuit may include an antenna feed coupled
with an output of the switched circuit to accept the pulsed radio
frequency oscillating signal and emit radio frequency pulses in
accordance with the pulsed radio frequency oscillating signal via
an antenna. The antenna feed may be configured to receive reflected
ones of the emitted radio frequency pulses.
[0028] In some cases, the circuit may include a set of magnitude
detectors coupled with the antenna feed. The magnitude detectors
may detect signals received with the antenna feed based on signals
generated from the switched circuit. The microcontroller may be
configured to sample one or more outputs of the magnitude
detectors. The outputs of the magnitude detectors may include an in
phase signal and a quadrature phase signal representing phase
and/or magnitude differences between the received reflected ones of
the emitted radio frequency pulses and the emitted radio frequency
pulses. The microcontroller may be configured to digitally
demodulate outputs of the magnitude detectors. The microcontroller
may be configured to digitally filter outputs of the magnitude
detectors. The microcontroller may be configured to digitally
filter one or more baseband signals derived from the magnitude
detectors. The microcontroller may be configured to digitally
amplify one or more baseband signals from the magnitude detectors.
The oscillator may include a dielectric resonator. The pulse
generator may include a logic gate circuit configured to receive a
timing signal generated by the microcontroller.
[0029] The microcontroller may be configured to generate an
indicator of any one or more of respiration, sleep and heart rate
information based on one or more signals received via the antenna
feed. The microcontroller may be configured to trigger the
circuit's sensing operations by selectively turning transmissions
on and off. The microcontroller may be configured to control
storing of data from received signals in epochs. The circuit may
also a memory interface. The memory interface may be one or more of
SD card interface, a microSD card interface, and a flash memory
interface. The circuit may also include a wireless transceiver for
transmission of data derived from sensing signals. The wireless
transmission may involve NFC communications.
[0030] The circuit may include a digital and/or analogue output
connection. The digital or analogue output connection may include a
RS232, serial and/or USB connection. The circuit may include an
analog output (e.g., an output interface or connector), and the
microcontroller may be configured to convert digital signals sensed
by the circuit into analogue signals for output via the analog
output. The analog signals may include a pulse width modulated
signal. The circuit may include a single printed circuit board and
the microcontroller may be a chip affixed (e.g., soldered) to the
printed circuit board.
[0031] Other aspects, features, and advantages of this technology
will be apparent from the following detailed description when taken
in conjunction with the accompanying drawings, which are a part of
this disclosure and which illustrate, by way of example, principles
of the technology. Yet further aspects of the technology will be
apparent from the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Further example embodiments of the technology will now be
described with reference to the accompanying drawings, in
which:
[0033] FIG. 1 is an illustration of an example detection apparatus
suitable for implementation with a radio frequency physiology
sensor of the present technology;
[0034] FIG. 2 is a diagram illustrating a conceptual structure and
process flow for evaluation of sensor signals suitable for some
embodiments of the technology;
[0035] FIG. 3 is a depiction of further processing of sensor
signals for the detection of example physiology indicators;
[0036] FIG. 4 shows example components involved in a generation of
range gated radio frequency signals with switched oscillation in
some embodiments of a sensor circuit for the present
technology;
[0037] FIG. 5 is a schematic of components for an architecture of
an example sensor circuit in some embodiments of the
technology;
[0038] FIG. 5A is an schematic of a circuit, such as for a single
printed circuit board (PCB), with an architecture of an example
sensor circuit in some embodiments of the technology;
[0039] FIG. 6 is a block diagram with example components for an
injection locking embodiment of the switched oscillator of FIG.
4;
[0040] FIG. 7 is a block diagram with example components for an
amplifier embodiment of the switched oscillator of FIG. 4;
[0041] FIG. 8 is a circuit diagram with example components for a
power regulation circuit suitable for some embodiments of the
disclosure;
[0042] FIG. 9 is a circuit diagram with example components for a
pulse generation circuit suitable for some embodiments of the
disclosure;
[0043] FIG. 10 is a circuit diagram with example components for a
RF transmission circuit;
[0044] FIG. 11 is a circuit diagram with example components for an
IF pre-amplifier circuit suitable for some embodiments of the
disclosure;
[0045] FIG. 12 is a circuit diagram with example components for a
microcontroller and outputs suitable for some embodiments of the
disclosure; and
[0046] FIG. 13 is an illustration of an interface for displaying
physiology data suitable for some embodiments of the
disclosure.
DETAILED DESCRIPTION
1. Overview
[0047] As illustrated in FIG. 1, some embodiments of the present
technology may implement a radio frequency (RF) sensing or
detection apparatus 100 having digital circuit components, such as
one with a microcontroller or microprocessor involved in the RF
sensing signal generation and/or signal (e.g., baseband, passband,
etc.,) processing. The apparatus is useful for detecting
physiological characteristics of a user 101 or patient in the
vicinity of the apparatus. The sensor may be a standalone sensor or
may be coupled with other apparatus, such as a respiratory
treatment apparatus, so as to provide an automated treatment
response based on an analysis of the physiological characteristics
detected by the sensor of the apparatus. For example, a respiratory
treatment apparatus with a controller and a flow generator may be
configured with such a digital sensor and may be configured to
adjust a pressure treatment generated at a patient interface (e.g.,
mask) in response to physiological characteristics detected by the
digital sensor.
[0048] Other data can be gathered from the user by other sensing
modules via a radio link, or directly from the medication
dispenser, e.g., via an identification chip such as RFID (radio
frequency ID), or from a measuring device such as a spirometer
(peak flow meter). Additionally, further data can be gathered from
the user via accelerometers, ECGs, Oximeters, etc. Additional data
may also be gathered from the user by way of a keyboard, a touch
sensitive pad, mouse, voice recording, etc.
[0049] With the inclusion of a microcontroller or microprocessor as
part of the sensor circuit to control or participate in sensing
operations of the sensor, increased functionality may be provided
and a reduction in the complexity of circuitry may be realized The
reduction in the amount circuitry may allow the size of the sensor
may be reduced, thereby making the sensor small and portable.
Additionally, the power consumption of the sensor may be reduced
with respect to such a sensor essentially formed with analogue
components, allowing the digital sensor to be powered by many
different types of sources (e.g., mains power, battery power,
etc.). As such, the cost, size, power consumption, and reliability
of the sensor including a microcontroller may be improved over
sensors containing complex analog circuitry.
[0050] The microcontroller may include control of the modulation
and demodulation timing of other components within the sensor. As
described in greater detail herein, the microcontroller may provide
timing pulses to control the modulation and demodulation of
transmitted and received RF signals to generate a baseband signal.
The timing pulses may also control the timing of the transmission
of RF signals by a transmitter as well as the receiving of the RF
signals by a receiver. As such, the microcontroller may provide
variable and dynamic range gating for detecting physiological
characteristics of a user 101 or patient within a particular
vicinity of the apparatus (i.e., the ability to manually or
automatically adjust the range of the sensor to, for instance,
monitor a room, monitor a sleeper at a different and/or changing
sensing range (say 1 m distance for a subject close to the sensor,
or 2.5 m for a subject further away from the sensor) etc.)
Additionally, the timing pulses may lower the system noise floor
and mitigate interference by dithering the timing of the
transmitted RF signals. For example, in generating timing signals,
the microcontroller may vary the timing of the timing signals to
dither the timing of the transmitted RF pulses. Dithering of the
timing when combined with averaging, that naturally occurs in the
baseband filters, mitigates harmonic tones and interference.
[0051] Modulation of the baseband signal to an intermediate
frequency (IF) signal, as well as the demodulation of the IF signal
back to a baseband signal may be enhanced by the addition of a
microcontroller to the sensor. The control of the generation and
demodulation of the IF signal by the microcontroller may allow for
complex digital synchronous demodulation schemes without the need
for complex hardware to be added to the sensor. Further, the
microcontroller may allow the sensor to utilize improved digital
filter and noise reduction when compared to sensors with analog
circuits.
[0052] A digitally implemented sensor of such an apparatus may
employ a transmitter to emit radio frequency wave signals, such as
radio frequency pulses for range gated sensing. A receiver, which
may optionally be included in a combined device with the
transmitter, may be configured to receive and process some, or all
of, the transmitted radio frequency pulses that are reflected off
of a user's body (e.g., head, torso, leg, arm, etc.) located in the
vicinity of the sensor. Signal processing may be employed, such as
with a microcontroller of the sensor that activates the sensor, to
derive physiological characteristics based on the received
reflected signals.
[0053] For example, as illustrated in FIG. 2, the RF transmitter
203 transmits a radio-frequency signal 205 towards a subject, e.g.,
a human 201. The source of the RF signal may be a local oscillator
(LO) 207, though other sources may be used. The reflected signal
209 is then received by an RF receiver 211 and amplified by an
amplifier 213. The amplified reflected signal may then be mixed
with a portion of the original signal by a microcontroller 215. The
output of this mixed signal may then be filtered digitally by the
microcontroller. The resulting signal may contain information about
the movement, respiration and cardiac activity of the person, and
is referred to as the raw motion sensor signal 217 and may be
output as digital and/or analogue signal(s).
[0054] FIG. 3 is a diagram illustrating processing of the raw
motion sensor signal to produce indicators of the physiological
characteristics. The raw motion sensor signal 217 may generally
contain components reflecting a combination of bodily movement,
respiration, and cardiac activity. Bodily movement can be
associated with the movement of a user's body and may be identified
by a motion detector 330 which may implement movement detection
algorithms, such as zero-crossing or energy envelope detection
algorithms or other more complex algorithms. Bodily movements
identified by the movement detection algorithms may be used to form
a "motion on" or "motion off" indicator. For example, such movement
detection algorithms may be implemented in accordance with the
methodologies disclosed in U.S. Patent Application Publ. No.
2009/0203972, the entire disclosure of which is incorporated herein
by reference. Further, a microcontroller, such as microcontroller
215, may execute the movement detection algorithms. The respiratory
activity is typically in the range 0.1 to 0.8 Hz, and can be
derived by filtering the original signal with a bandpass filter 320
with a passband in the 0.1 to 0.8 Hz region. The cardiac activity
is reflected in signals at higher frequencies, and this activity
can be accessed by filtering with a bandpass filter 310 with a
passband of a range from 1 to 10 Hz. Such bandpass filtering may be
accomplished by the microcontroller via algorithms running within
the microcontroller.
2. Digital Sensor
[0055] A digital respiration and movement sensor may be a range
gated RF motion detector. The digital sensor may be configured to
accept a DC power supply input and provide digital and analogue
motion channel outputs with both in phase and quadrature components
of the respiration and movement signals of a person within the
detection range. In the case of a pulsed RF motion sensor
implemented with digital control, range gating can help to limit
movement detection to only a preferred zone or range. Thus,
detections made with the sensor may be within a defined distance
from the sensor.
[0056] To achieve range gating in a digital pulsed RF motion
detector system, including a microcontroller, the RF pulses should
have a fast turn on and settling time characteristic. Although
wideband RF oscillators with a low Q factor tuned circuit may be
suitable for such embodiments, such wideband oscillators are prone
to frequency stability issues. However, switching the wideband RF
oscillator ON and OFF can allow the oscillator to generate RF
pulses. Accordingly, embodiments of the present technology may
improve RF oscillator frequency stability while maintaining the
fast switching characteristics required for range gating.
[0057] Illustrated in FIG. 4, is an example of a digital sensor 402
of the present technology which may employ an oscillator 404, such
as a dielectric resonant oscillator (DRO). The DRO may be a high Q
DRO, that is a narrowband oscillator (e.g., a DRO operating at
10.525 GHz). Such an oscillator may incorporate a puck of
dielectric material. The DRO typically generates a stable RF
frequency characteristic and is relatively immune to variation in
temperature, humidity and component parasitics. However, it may
have a very slow turn on time. The slow turn on time may result in
the oscillator being unable to switch ON and OFF quickly enough to
provide an RF signal suitable for a range gated system. For
example, a typical DRO may switch ON about 1000 times too slowly to
meet some sensor range gating requirements.
[0058] Accordingly, to address such issues, the oscillator 404 may
be coupled with a switched oscillation circuit, such as a switched
wideband oscillator 406 or a switched amplifier. In such a case,
the DRO oscillator 404 may produce a stable RF oscillation signal
404-CRF (continuous radio frequency) when it is kept continuously
ON during pulsed transmissions rather than being powered ON and OFF
by switching the DRO oscillator's power source. The stable RF
oscillation signal 404-CRF continuously output from the DRO
oscillator 404 may then be applied to an input of the switched
wideband oscillation circuit 406. Based on a timing pulse signal
408-PRF (pulse repetition frequency) output from a pulse generator
408 to an input of the switched wideband oscillation circuit 406,
the switched wideband oscillation circuit 406 may generate the
radio frequency pulse signals 406-RFPS used for range gating in
synchrony with the pulse signal. The transmission of the pulsed RF
signals may be from a suitable antenna and antenna feed (not shown
in FIG. 4).
[0059] The timing of the pulse generator may be controlled by a
timing signal from a microcontroller (uC) 410. In this regard, the
timing signal from the microcontroller 410 may trigger the pulse
generator 408, or in some cases the microcontroller 410 can serve
as the pulse generator. For example, in response to the triggering
pulses from the microcontroller, the pulse generator may generate a
1 MHz PRF 408-PRF, as well as a 8 kHz intermediate frequency (IF)
demodulation pulse signals, described in detail herein (not shown
in FIG. 4). The digital pulse generator circuit 408 generates the
IF modulation pulse signals necessary to realize range gating under
the control of the IF signal. By varying the time of these IF
demodulation pulse signals, programmable range gating can be
realized; this variation can be under the control of the
microcontroller which in turn realizes such programmable range
gating.
[0060] In the case of this implementation of the switched wideband
oscillator, injection locking may be employed to stabilize the
switched wideband oscillator to provide both frequency stability
and fast oscillator turn on with good OFF attenuation
characteristics. Thus, the switched wideband oscillation circuit
406 may be injection locked by the DRO oscillator 404. In the case
of the implementation of the switched amplifier, the wideband
amplification of the DRO oscillator's RF output signal can provide
both frequency stability and an even faster turn on time.
[0061] Alternatively, in some embodiments, rather than implementing
a switched oscillation circuit to generate the pulsed radio
frequency signal as illustrated in FIG. 4, one or more
semiconductor switches, such as in series, may be implemented to
selectively shunt or pass the radio frequency signal. In such
alternative embodiments, the switch or switches merely permit
selective output of the radio frequency signal due to toggling of
the switches. In this sense, the switch, as opposed to the switched
oscillation circuit, merely passes the received oscillation signal
at certain times. However, there are several disadvantages with
such implementations. One such disadvantage of the semiconductor
switch architecture is that the components are expensive at
microwave frequencies. Another disadvantage with such a switching
architecture is that RF signal attenuation (i.e., the ratio of ON
signal level to OFF signal level) is low. A high attenuation is
required to permit correct range gating performance. Multiple
switches, such as in a "T" switch network, can be implemented to
mitigate such attenuation issues but may undesirably increase its
cost.
[0062] Example digital sensor circuit architectures according to
some embodiments of the present technology are illustrated in the
FIGS. 5 and 5A. The circuit may be a digital bio-motion sensor
implemented as a pulse radar system operating in, for example, the
microwave X-band at a frequency of 10.525 GHz. A high frequency may
allow for RF pulse waveforms which have very sharp lead and end
edges, resulting in a cleaner pulse signal. However, other suitable
RF frequencies may be implemented. Some embodiments may optionally
employ a method for modulation and demodulation of the pulse radar
signal as described in U.S. Pat. No. 6,426,716, the entire
disclosure of which is incorporated herein by reference.
[0063] As illustrated in FIGS. 5 and 5A, the digital sensor circuit
may be formed by four main sections:
[0064] (1) a homodyning transceiver frontend section: This section
may include the switched oscillation circuit 504, such as a
switched 10.525 GHz wideband oscillator or switched amplifier,
which may include a DRO oscillator, an antenna feed 510, antenna(s)
516, and a magnitude detector 512 for generation and reception of
the pulsed RF radar signals;
[0065] (2) a pulse generator section: This section may include a
pulse generator circuit 506. The generator may be configured to
generate the pulse signals 508-PRF, 508-IF (IF standing for
intermediate frequency) for modulation and demodulation of the RF
radar signals (i.e., RF Tx, as shown in FIG. 5). The pulse
generator may also be configured to generate IF modulation pulse
signals for the modulation of the IF signals, as further shown in
FIG. 5;
[0066] (3) a dual channel IF pre-amplifier 514 for the
amplification of the received IF signals, which may subsequently be
sent to the microcontroller 508, to produce an amplified baseband
signal; and
[0067] (4) a microcontroller 508 for generating the timing pulse
signals which trigger the pulse generator 506. Additionally, the
microcontroller may be programmed for digital filtering of the
baseband signals (e.g., digital signal processing of the received
raw motion signal to derive cardiac, respiratory and/or motion
signals). The use of the microcontroller may eliminate the need for
separate analog circuitry, resulting in reduced size, cost, and
energy consumption by the sensor.
[0068] In addition to the above four sections, the digital sensor
may also include sections for power management 502, memory storage
devices 524 (i.e., SD), various input/output connections (i.e.,
Analog IQ 518, USB/RS232 520, NFC 522), and ECG electrodes (not
shown.) As shown in FIG. 5A, all of the sections may be
interconnected and controlled with the microcontroller.
[0069] The digitally implemented sensor may be contained in a
single housing. In this regard, the sensor, as shown in FIG. 5A,
may be positioned within a housing such as the housing 1301 shown
in FIG. 13. In some embodiments, the housing may be formed with of
a combination of metals, plastics, or other materials. The housing
may also include opening for interface connection ports, such as
the Analog I/Q connection ports and USB/RS232 connections shown in
FIG. 5A. Additionally, the housing may include an area for fitting
one or more removable memory modules, such as SD cards, microSD
cards, flash, etc. The memory modules may be made accessible by the
housing through hinges, doors, latches, etc.
[0070] The housing may also include indicators which show the
various states of the digital sensor (e.g., in operation, in
standby, in an error state, etc.). In some embodiments the
indicators may include LEDs, which may blink, change color, or
light up based on the state of operation of the digital sensor.
[0071] In some embodiments the sensor may be placed within housings
of various shapes such as clips, mats, and patches. For example,
the digital sensor may be placed into a phone charger. Such a
design may minimize the need for running extra wires to or from a
power source, such as a smartphone. In another embodiment, the
housing may be in the form of a clip for connecting the sensor to
objects, such as a bed sheet, shirt, or pants. In another
embodiment the sensor may be placed into a mat, which may be
positioned next, above, or below a bed. In yet another embodiment,
the sensor may be placed into a patch which includes an adhesive,
such as tape for connecting the digital sensor directly to an
object such as a user.
2.1 Digital Range Gating
[0072] In a typical range gated sensor, a continuous RF signal is
transmitted into a room. Since the transmitted RF signal is
continuous, there is no range gating because the receiver receives
most, or all, of the room reflections. In this regard, the
continuous RF signal may produce many reflections which may be
received by the sensor. Some of the received RF signals will have a
static RF signal phase difference with regard to that of the
transmitted RF signal, while other received RF signals, such as
those which are reflected off moving targets, will contain a
changing RF signal phase difference with regard to the transmitted
RF signal. As such, "movement information" corresponding to the
targets movements, may be determined based on the phase difference
between the transmitted RF signal and the received RF signal.
[0073] To limit the range of the RF signals received by the
receiver of the sensor, the sensor may transmit a pulsed RF signal
into a room. During the OFF time (i.e., the time when the pulsed RF
signal is not being transmitted,) the RF signals resulting from
reflections of the transmitted pulsed RF signal will diminish, and
eventually fade away. In some embodiments, the time t0 for RF
signals resulting from the reflections after a transmitted pulsed
RF signal has been switched OFF to fade away is about 200 ns (nano
seconds).
[0074] Upon starting the transmission of an RF pulse at time (t),
with a transmission length of T, into a room without any reflected
RF signals, the only signals a receiver can receive are reflections
from targets within a range of c*(t)/2 where c is the speed of
light. For example, 2 ns after an RF pulse is transmitted, the only
reflections received at the RF receiver can come from targets
within the time of flight of the transmitted RF signal, namely 0.5
ns out and 0.5 ns back. As such, the detectable target range of a
0.5 ns RF pulse may be around 0.1 m.
[0075] The introduction of a microcontroller, such as
microcontroller 508 into a sensor may allow for more control over
the range gating of the sensor. In this regard, the microcontroller
508 may control the timing of transmission and reception of RF
pulses. For example, as shown in FIG. 5, to control the
transmission of the RF pulses, the microcontroller may send a
timing pulse to a pulse generator, such as pulse generator 506.
Based on the timing pulse, the pulse generator 506 may send a
pulsed repetition frequency (508-PRF) at a rate such as 1 MHz to a
switched RF oscillator, such as switched RF oscillator 504. The
switched RF oscillator may then transmit, for example, 10.525 GHz.
RF pulses at a 1 MHz rate to an antenna feed, such as antenna feed
510 for transmission by an antenna, such as antenna 516.
[0076] The ability of the sensor to receive and demodulate signals
in a specific time period may also be more readily controlled by
microcontroller 508. In this regard, the magnitude detector 512 may
be a switched magnitude detector (or any other such mixer) that is
switched by the timing control of the microcontroller. The
magnitude detector may then receive both the transmitted signal and
the received signals as a combined signal according to this timing
control. This combined signal from the antenna feed may be
demodulated by the mixer to determine a baseband signal, which
includes the "movement information." This baseband signal may
represent the difference between a) the received signal after the
transmitted signal is removed through the demodulation, and b) the
transmitted signal.
[0077] In this regard, the RF receiver, such as magnitude detector
512, may receive a combined signal of 1) A Sin(.omega.t)+B
Sin(.omega.t+phi), where A Sin(.omega.t) is the transmitted RF
pulse and B Sin(.omega.t+phi) is the received signal, .omega.t is
the angular frequency at time (t), and phi is the phase of
oscillation. Upon the received signal and transmitted signal being
input into the magnitude detector, the magnitude detector may
combine (i.e., mix) the two signals as follows: 2) [A
Sin(.omega.t)+B Sin(.omega.t+phi)]*[A Sin(.omega.t)+B
Sin(.omega.t+phi)]. The resulting output is a demodulated signal
that may be considered a baseband signal.
[0078] In some embodiments an additional magnitude detector(s) may
be added to implement two or more receivers. For example, the two
receivers may be positioned at a known distance apart (e.g.,
lambda/8), such that in-phase and quadrature (I/Q) components of a
signal may be generated in two signals. Thus, one magnitude
detector 512 may produce a single IF signal or baseband signal)
that is an in-phase signal. The other magnitude detector may then
produce a single IF signal or baseband signal) that is a quadrature
phase signal. Post processing of the baseband and IF signals, such
as by the IF pre-amplifier 514 and microcontroller 508 may be
performed on each of the signals produced by the magnitude
detector(s). In some instances each magnitude detector may include
a non-linear diode.
[0079] The magnitude detector 512 may demodulate the combined
signal during the time period it is switched ON by the
microcontroller 508 to determine a difference between the
transmitted RF pulse signals and the received RF signals (i.e., the
movement information), at a certain range. In this regard, the
microcontroller 508 may provide range gating control by sending a
pulse timing signal to the pulse generator 506, which in turn sends
a pulse to cause the magnitude detector to turn on. Continuing the
above example, the magnitude detector may turn on at time (t1) for
a detection time of T seconds. The range gating may be determined
by the time period t1+T, and may produce a range of c*(t1+T)/2. Any
reflections after the time period t1+T are not detected, and hence
range gating is realised.
2.2 IF Signal and Amplification
[0080] In some embodiments the microcontroller may enable the
magnitude detector to switch ON for a second period T0 to provide
an intermediate frequency amplification stage. As previously
discussed, the baseband signal output by the magnitude detector 512
carries the movement signal information. However, the baseband
signal may contain natural noise at the low target moving
frequencies (e.g., breathing frequencies of 0.2 Hz), commonly
referred to as 1/f noise or flicker noise. As such, there may be an
undesirable amount of noise added to the baseband signal when it is
amplified to a signal level for processing.
[0081] The magnitude detector may modulate the baseband signal with
an IF signal to bring the low target moving frequencies up to a
higher frequency which can be amplified with less noise. In order
to create the IF signal, the magnitude detector 512 may demodulate
the combined signal during a second time period further controlled
by additional timing pulses generated by the microcontroller 508 to
determine a difference between the transmitted RF pulse signals and
the received RF signals to determine a reference signal. In this
regard, the microcontroller 508 may provide additional timing
signals to the pulse generator 506, which in turn sends a pulse to
cause the magnitude detector to turn on for a second time, prior
to, or after, the first time period t1. Continuing the above
example, the magnitude detector may turn ON at time (t0) for a
detection time of T seconds. In one example, the previously
introduced time period (starting at t1) may intentionally target an
area of the room where the user's movements were expected to occur,
in order to generate a movement signal. In contrast, the targeted
range of the newly introduced period (starting at t0) may target a
location where not too much movement is anticipated, so as to
generate a reference signal. The range gating may be determined by
the time period t0+T, and may produce a second range of c*(t0+T)/2.
Any reflections after the time period t0+T are not detected during
this first ON period. Although the detection time of T seconds is
shown as the same for the first and second detections, the
detection times may be different. Further, the number of pulses N,
which are detected at t0 and t1, may be non-successive pulses, such
as every other pulse and the number of pulses detected at t0 and t1
may be different. Further still, t1 and t0 may be measured in the
same or different pulses.
[0082] The combined signal received by the magnitude detectors from
the first and the second time periods may be processed by the
microcontroller to determine a baseband reference signal, which is
based on the difference between the movement signal and the
reference signal.
[0083] In one example, in order to modulate the IF signal to a
higher frequency, such as 8 kHz, the magnitude detector 512
may:
[0084] a. Demodulate the RF pulse at time (t0+T) once every pulse
(PRF frequency provided by the pulse generator (i.e., IF Modulation
signal in FIG. 5)), and repeating this process 64 times to obtain
an average; and
[0085] b. Demodulate the RF pulse at time (t1+T) once every pulse
(PRF frequency), and repeating this process 64 times to obtain an
average.
[0086] Upon averaging the demodulated pulses N times, then the IF
signal frequency may be PRF/2N. Continuing the above example, N may
be 64 and PRF may be 1 MHz. As such, the resulting IF frequency may
be 8 kHz. The IF signal may be amplified by an IF Preamplifier 514
for amplification prior to signal processing. In this regard, the
magnitude detector 512 may pass the IF signals to the IF
pre-amplifier which may switch on at 8 kHz, thereby amplifying the
8 kHz IF signal. By amplifying the IF signal at 8 kHz, as opposed
to 0.2 Hz, 1/f noise may be mitigated by a factor of 40000, or more
or less.
[0087] The amplified IF signal may then be forwarded to the
microcontroller, which may demodulate the IF signal back to an
amplified baseband signal. The baseband signal may then be
processed by the microcontroller, as described herein. Thus, with
single demodulation timing, such as t1, the sensor may provide
range gating, but not IF amplification. With double demodulation
timing, such as t0 and t1, the sensor may be capable of providing
both range gating and IF stage amplification.
2.3 Power
[0088] The digital sensor may be powered from a DC source. In this
regard, the digital sensor may be attached to a smartphone via a
smartphone adaptor. For example, as illustrated in FIG. 12, the
digital sensor may include a micro-USB interface 1208. As such,
when the digital sensor is connected to a smartphone via a micro
USB-adapter the digital sensor may then receive power, such as 5V
to 12V at 2-5 Amps, or more or less.
[0089] While only a micro-usb interface is shown in FIG. 12, other
interfaces such as USB A-type, USB B-type, mini USB, firewire,
thunderbolt, etc. may be possible. Further, other power sources may
also be used to power the digital sensor, such as A/C power
supplies and/or other DC power supplies. Additionally, no external
power source may be necessary, as the digital sensor may include an
internal power supply, such as a battery. The battery supply may be
charged via external connection or with wireless charging, such as
inductive charging.
[0090] The power supply may also include power regulation circuit
for controlling the power received by the sensor. For example, as
illustrated in FIG. 12, a power regulating circuit 1210 may receive
power from a source, such as the micro-usb interface 1208 and
condition the power into a consistent power value, such as 5V to
12V at 2-5 Amps. Further, the power regulating circuit 1210 may
attenuate any power surges.
[0091] As illustrated in FIG. 5, the power supply 502 may be used
to power the components included within box 503. In this regard,
the power supply may be directly connected to the switched RF
oscillator, 504, pulse generator 506, microcontroller 508,
magnitude detector 512, IF pre-amplifier 514, analog interface 518,
USB/RS232 520, NFC 522, and memory 524. In some embodiments the
power supply. In addition, the power supply may be used to power
other components such as powered antenna feeds, amplifiers,
etc.
2.4 Pulse Generator
[0092] The pulse generator circuit 506 receives a PRF timing
signal, as shown in FIG. 5, from the microcontroller 508. Upon
receiving the PRF timing signal the pulse generator may generate a
PRF signal, such as a 1 MHz pulse with a 0.5 microsecond duration
every 1 microsecond, or more or less. An example illustration of a
PRF timing signal is illustrated as signal 408-PRF in FIG. 4.
[0093] In addition, the pulse generator 506 may receive an IF
timing pulse signal from the microcontroller 508, and generate an
IF modulation pulse signals. Upon receiving the IF timing pulse
from the microcontroller 508, the pulse generator may send IF
modulation pulse signals to the magnitude detector 512. As
described previously, the pulse generator may send IF modulation
pulses to each receiver in the magnitude detector. For example, the
pulse generator may send an IF modulation pulse to an in-phase
receiver and a quadrature receiver.
[0094] A representation of an example circuit for implementing the
pulse generator is found in FIG. 9. The pulse generator may include
a buffer 902 and a gate generator 904. The buffer 902 assures
proper signal voltage (polarity) is delivered to the gate generator
904. The gate generator 904 may include two or more inverters and
may generate the IF modulation timing pulses for the magnitude
detectors.
2.5 Switched Oscillator
[0095] The PRF timing signal may cause a switched RF oscillator,
such as oscillator 504, to switch on and off, thereby causing the
switched RF oscillator to transmit RF pulse signals. In this
regard, the RF oscillator may operate at 10.525 GHz, and be pulsed
(i.e., turned on and off) at the 1 MHz PRF rate. The output signal
of switched oscillation circuit 406 is the RF pulse signal
illustrated as signal 406-RFPS in FIG. 4 and "RF Tx" in FIG. 5.
[0096] The RF pulse signal may be transmitted to an antenna feed
510, where the RF pulse signal may be output via an antenna 516 at
a duration of 0.5 microseconds every 1 microsecond, or more or
less. Such an RF pulse train with this characteristic may have a
narrow signal bandwidth (e.g., approximately 25 MHz) and may be
suitable for range gating applications and/or meeting RF regulatory
approval certification. RF signals, such as those which are
reflected off moving targets, may be received by the antenna 516
and sent from the antenna feed 510, to a magnitude detector
512.
2.6 Magnitude Detector
[0097] In one example, the magnitude detector 512 will actually
include two magnitude detectors processing the combined transmitted
and reflected signals at a lambda/8 spacing, as indicated in FIG.
5. The magnitude detector may act as a mixer and demodulate the
combined transmitted RF signal and received RF signals so as to
extract the phase difference between the receive signal and the
transmit signal. Further, the magnitude detector may utilise its
switching capability to generate an IF signal from the demodulated
RF signal to mitigate the 1/f noise, as previously described.
[0098] Both the transmitted RF signal and received RF signals, such
as those which are reflected off moving targets, may be presented
to the input of a RF magnitude detector 512 (e.g., a homodyning
receiver peak detector) as a combined signal. The magnitude
detector 512 may operate as a receiver, which may generate a
measure of the magnitude and/or phase of the received signals with
respect to the transmitted signal. The phase and/or magnitude of
the received signal may change with respect to the transmitted
signal when the target moves. As result, the magnitude detector 512
may determine a measure of the movement of a target based upon the
phase difference between the transmitted and reflected signals.
[0099] The magnitude detector receiver may be switched on and off
at offset times "t1" from the start time of the RF pulse. For
instance, the microcontroller 508 may provide range gating control
by sending a pulse timing signal to the pulse generator 506, which
in turn sends a pulse to cause the magnitude detector to turn on.
Additionally, the magnitude detector may receive the transmitted RF
pulse. As such, the magnitude detector may receive both the
transmitted signal and the received signals as a combined signal
during the time the magnitude detector is on. This combined signal
may be demodulated to determine a baseband signal, which includes
the "movement information." In this regard, the difference between
the received signals provides a measure of the movement that has
occurred in the time period from the start of the RF pulse, and
hence the movement that has occurred within the range (c*t1)/2,
where c is the speed of the light. The baseband signal may be the
difference between a) the received signal after the transmitted
signal is removed through the demodulation, and b) the transmitted
signal.
[0100] Continuing the above example and as previously described,
the magnitude detector may turn on for a period T1 at time t1, for
the purpose of range gating. The magnitude detector may also turn
on for a second period T0 at time t0, to provide an intermediate
frequency amplification stage. As previously discussed, the signal
output by the magnitude detector 512 carries the movement signal
information, as well as 1/f noise. As such, the magnitude detector
may modulate the signal with an IF signal to bring the low target
moving frequencies up to a higher frequency which can be amplified
with less noise.
[0101] In order to create the IF signal, the magnitude detector 512
may demodulate the combined (transmitted+reflected) signal during a
second time period further controlled by additional timing pulses
generated by the microcontroller 508 to determine a difference
between the transmitted RF pulse signals and the received RF
signals to determine a reference signal. The difference between
movement signal and the reference signal is the IF signal. The IF
signal may then be modulated to a higher frequency, such as 8 kHz,
as previously described.
[0102] Referring back to the use of two magnitude detectors, this
is done too overcome nulls in movement sensitivity that may occur
every .lamda./2 in space, where .lamda. is the wavelength of the RF
signal, a second "quadrature phase" peak detector receiver may be
placed at a .lamda./8 distance from the first "in phase" receiver.
For example, in the case of a 10.525 GHz frequency RF signal, the
distance .lamda./8 is 3.55 mm. The physical spacing of this second
receive circuit generates a quadrature receiver output which has
maximum movement sensitivity at the point of the "in phase" minimum
sensitivity.
2.7 IF Pre-Amplifier
[0103] The received in phase and quadrature phase IF signals may
then be processed through an IF Pre-amplifier 514. The IF
pre-amplifier 514 may amplify both the in phase and quadrature
phase IF signals separately. The amplified signals may then be
passed onto the microcontroller 508 for sampling and digital
processing, such as digital demodulation and baseband digital
filtering.
[0104] As shown in FIG. 11, the IF pre-amplifier may include two
separate channels. An in phase channel 1104 and a quadrature phase
channel 1106. As further illustrated in FIG. 11, each phase channel
includes two amplification stages, though variations in the number
of stages are possible. For example, each channel may include one,
two, three, four, etc., amplification stages. Additionally, the
channels may include a different number of amplification
stages.
2.8 Microcontroller
[0105] In addition to providing the timing signals, as described
previously, the microcontroller or microprocessor may also
demodulate the amplified IF signals and process the resulting
amplified baseband signals. In this regard the microcontroller's
firmware may be programmed with certain digital signal processing
"DSP" capabilities. For example, the microcontroller may be
programmed to receive and sample the amplified signals at 128 kbps
with 2048 times oversampling, or more or less, each with an
analogue to digital (ADC) converter. In some embodiments the ADC
may use 10 bits, or more or less. The microcontroller may be
programmed to detect the difference between the reference signal
and the movement signal that exists in both the in phase signal and
the quadrature phase signal. As result, the microprocessor
synchronously demodulates the amplified IF modulated receive
signals (I and Q) and produces amplified baseband signals.
[0106] The resulting demodulated signals (I and Q) may then be
filtered by algorithms within the microcontroller. In this regard,
the microprocessor may filter the digital baseband signals. For
example, the microcontroller 616 may be programmed to perform the
bandpass filtering of out of band interfering signals and low
harmonic emissions from the sensor. The circuit may also generate
separate outputs for respiration and movement since movement and
respiration signals are at different frequencies and may be
filtered by different filters. As the microcontroller 508 provides
the timing of the pulse generator 506, including the PRF and IF
timing signals, the microcontroller is aware of the time signals
are sent and received. Accordingly, the microcontroller can
demodulate both the in phase and quadrature phase signals.
[0107] With such operations, an example pulsed RF range gated
motion sensor with a narrow signal bandwidth may be
implemented.
[0108] The microcontroller may be a single integrated chip
including a processor core, memory, and programmable input/output
peripherals.
1. Digital Sensor Embodiments
[0109] An example embodiment of a frontend section for implementing
this range gated pulsed radar system may be considered in reference
to the circuit component diagram of FIG. 6. In this embodiment, the
switched wideband RF oscillator 606 is implemented. Typically, a
wideband oscillator can be prone to frequency stability issues,
such as that caused by humidity and/or temperature variations,
component and batch parasitic variations and housing proximity
effects. However, the present circuit design permits the oscillator
to maintain the RF centre frequency within desired limits (e.g.,
within approximately 10 MHz of 10.525 GHz). It provides fast
switching and a stable pulsed RF signal. It permits a fast turn on
of the oscillation circuit while providing a fast stabilisation of
frequency and amplitude. The turn on time .DELTA.t is related to Q
and hence bandwidth (BW) of the oscillator may be as follows:
.DELTA.t=Q/(nf.sub.0).about.1/BW.
[0110] In some cases, the oscillation circuit may optionally be
hermetically sealed and/or may optionally include a temperature
control circuit.
[0111] The oscillator 606 may be injection locked by the DRO
oscillator 604. Injection locking occurs when the wideband
oscillator 606 is disturbed by the DRO oscillator 604 operating at
a nearby frequency. Since the coupling is strong enough and the
frequencies near enough, the DRO oscillator can capture the
wideband oscillator, causing it to have essentially identical
frequency as the DRO oscillator. Thus, in a typical embodiment,
these two oscillators have a suitable "lock in range" for injection
locking.
[0112] In the circuit variant of FIG. 6, a high stability
Dielectric Resonator Oscillator, DRO, circuit may include a
transistor (not shown), such as a low noise gallium arsenide (GaAs)
Field Effect Transistor (FET) or a Bipolar Junction Transistor
(BJT), configured as an amplifier with feedback provided via a
frequency stable Dielectric Resonator coupled with microstrip lines
to the gate (base) and drain (collector) circuits of this
transistor. Such a DRO oscillator, operating at for example, 10.525
GHz, may be implemented for the frequency reference for the radar
system centre frequency.
[0113] This DRO reference oscillator is configured to maintain the
working centre frequency of the sensor within a regulatory
specification over the operating temperature and humidity range of
the product. This reference oscillator circuit may be enclosed
inside a metal cavity to ensure good screening and high quality
factor. Also, fine tuning of the centre frequency may optionally be
provided by a mechanical tuning screw in a top of a screen above
the resonator.
[0114] The output signal from the DRO reference oscillator 604 may
be fed into the switched wideband oscillator 606 via an attenuator
and/or matching network 609 having a feed line to the switched
oscillator 606. The attenuator and matching network properties may
be configured to ensure that the second oscillator will only
oscillate at a frequency determined by the reference oscillator
over the working temperature and humidity range of the product. The
configuration of the attenuator may set the injection level to the
modulated oscillator 606 and hence the capture frequency range. The
matching network may be configured to convert the low impedance
output of the reference oscillator 604 to higher impedance suitable
for injection into the modulated oscillator 606. The matching
network may be a
shunt-open-circuited-stub:transmission-line:shunt-open-circuited-stub
directly coupled network. The feedline from the network 609 may be
coupled to the gate (base) of the transistor 606-T. In some
embodiments, this microstrip feedline to the transistor may be
low-pass, such as when it is formed in a direct feed 608-DFL
configuration. However, in some embodiments, the feed line may be
high-pass, such as when it is formed in an indirect feed
configuration 608-IFL.
[0115] Thus, the switched oscillator 606 may include a transistor
606-T, such as an FET. This transistor may be configured with a
tuned microstrip feedback network, which, in addition to any
desired gain characteristics, will include any desired oscillation
characteristics suitable for the lock in range. Some or all of the
feedback may be provided by the internal parasitics of the
transistor 606-T. This tuned microstrip feedback network may be
configured to ensure fast rise and fall time of the output signal
required for range gating of the pulse radar system. For example,
such range gating of the pulse radar system may be implemented in
accordance with the methodologies disclosed in U.S. Patent
Application Publ. No. 2015-0216424, the entire disclosure of which
is incorporated herein by reference.
[0116] The bias circuit of the switched oscillator 606 is also
supplied by a pulse from the pulse generator 608 so that
oscillations can only occur during the application of the switch
pulse. As illustrated in FIG. 6, this output of the pulse generator
is also input to the gate or base of the transistor 606-T of the
switched oscillator 606. The pulse generator may be controlled with
timing signals from the microcontroller 616. As such, the
microcontroller 616 may be able to store timing information on the
transmitted and received signals.
[0117] The switched oscillator then produces an RF pulse at the
stable reference frequency when a positive pulse is applied to the
base circuit by the pulse timing circuit or pulse generator that is
responsive to the microcontroller. In some versions, the pulse
generator may include a fast logic gate (e.g., a NAND gate or AND
gate circuit) to generate the timing pulse. Optionally, the output
of the logic gate may be applied to a circuit network configured to
maintain a wideband characteristic to ensure fast and effective
switching of the switched oscillator.
[0118] The pulsed RF frequency output from the switched oscillator
606 is then input to the peak/magnitude detectors 612 and filter(s)
613. Optionally, this pulsed RF frequency output may be input to
these components via a series resistor or via an attenuator
network. The series resistor can be implemented to optimise the
drive level to the magnitude detectors, isolate the switched
oscillator from signal reflections and improve system impedance
match.
[0119] The filter 613 may be implemented with a microstrip bandpass
filter and connected to the antenna feed 610. The microstrip
bandpass filter may be implemented to ensure high rejection of out
of band interfering signals and low harmonic emissions from the
sensor. This filter may provide high rejection at radio/TV
broadcast, Wi-Fi, DECT, ISM and mobile phone frequencies commonly
encountered in domestic and clinical environments. The filter may
also provide sufficiently high rejection at the second harmonic
frequency (e.g., 21.05 GHz in the case of a 10.525 GHz oscillator)
to ensure regulatory product compliance in all world markets. The
filter may be a high performance sub-miniature energy-trapping low
insertion loss coupled H resonator bandpass filter in some
embodiments.
[0120] The magnitude detectors 612 can be implemented to provide
two phase separated receive I & Q channel IF signals that are
proportional to the magnitude sum of the forward propagating and
reverse propagating radar signals. In this regard, the inputs to
each magnitude detector may be separated along a microstrip feed
line by a distance of .lamda./8 as previously discussed. However,
in any of the embodiments described herein, the separation distance
may be different. For example, the I & Q magnitude detector
separation distance may be generalized to +/-(2n-1).lamda./8. Thus,
the separation distance may optionally be chosen according to any
of the following distances: .lamda./8, 3.lamda./8, 5.lamda./8,
7.lamda./8, . . . , etc.
[0121] Alternative embodiments of the present technology in which
the switched oscillation circuit is provided in an amplification
configuration may be considered in view of the illustrations of
FIG. 7. This embodiment is similar to that of the embodiment of
FIG. 6. However, in this embodiment, rather than having a switched
oscillator 606, the circuit employs a switched wideband amplifier
706. In the examples, the amplifier is implemented in a common
source configuration. However, alternative configurations may be
implemented in some embodiments (e.g., common drain or common
gate.)
[0122] In this circuit variant, the high stability dielectric
resonator oscillator 704 and the pulse generator 708 may employ the
configuration discussed with regard to the embodiment of FIG. 6.
The output signal from the DRO reference oscillator 704 is input to
attenuator 709. The attenuator ensures frequency stable operation
of the reference oscillator under all conditions and is configured
to apply an optimum drive level to the switched amplifier 706. Like
the embodiment of FIG. 6, the pulse generator 708 may be controlled
by timing pulses from the microcontroller 716.
[0123] The outputs of the attenuator 709 and the pulse generator
708 are coupled to the switched RF power amplifier 706. In this
regard, the switched power amplifier may include a transistor
706-T, such as an FET. The pulse switching signal from the pulse
generator is applied to the drain (collector) of the transistor
706-T. The attenuated signal from the DRO oscillator 704 is applied
to the gate (base) of the transistor 706-T. The source (emitter) of
the transistor 706-T may be coupled to a ground, such as a ground
plane of a printed circuit board (PCB) on which the circuit 15
formed.
[0124] The switched power amplifier thereby produces an amplified
radar pulse at the stable reference frequency (e.g., 10.525 GHz)
when a positive pulse is applied to the drain (collector) by the
timing of the pulse generator circuit as controlled by the
microcontroller, which may include circuit components, such as
series resistor, series inductor and capacitors, configured to
ensure fast switching and minimal overshoot of the modulation pulse
applied to the modulated amplifier 706.
[0125] The pulsed radio frequency output from the modulated power
amplifier 706 is fed via an optional second attenuator 709-2,
through the magnitude detectors 712, through filter 713 (e.g.,
bandpass filter as previously described in reference to FIG. 6) to
the sensor antenna (such as a horn probe antenna) or antenna feed
710. The second attenuator 709-2 may be configured to optimise the
drive level to the magnitude detectors and improve system impedance
match. This second attenuator can be omitted in some
embodiments.
[0126] Some potential advantages of the circuit configuration of
FIG. 7 may include the elimination of the lock in range
requirements. Additionally, the circuit complexity associated with
implementation of a wideband oscillator is removed. Moreover, the
turn on time of the wideband RF amplifier can be faster than the
wideband RF oscillator. With the use of the microcontroller,
filtering requirements may be handled digitally, reducing the power
consumption and size of the sensor.
2. Microcontroller
[0127] The microcontroller 508, in addition to implementing the
digital baseband filtering functions and RF transmission timing
functions as discussed herein, may also be programmed to run an
integrated engine. The integrated engine may enable the
microcontroller to manage operations of the digital sensor. In this
regard, the microcontroller may be used to trigger sensor operation
by, for example, starting, stopping, and/or pausing sensing
operations of the sensor. Further, the microcontroller may also be
programmed to control the power state of the sensor, such powering
on/off the sensor and placing the sensor into standby. As
previously discussed, the microprocessor may also be programmed to
vary the range of the sensor.
[0128] The microcontroller 508 may also be programmed to manage the
user's physiological data which is received. In this regard the
received signal data may be time and/or date stamped using
information from an external source, such as a smart phone.
Alternatively, the sensor may include an internal clock. The
received signal data may be stamped by the microcontroller or upon
output from the microcontroller to an external device, such as a
smart phone. The stamped data may then be displayed, stored and/or
output from the digital sensor.
[0129] The signal data may be organized into thirty second epochs,
or more or less, which include various physiological measurements
of the user such as motion, sleep, respiration and/or heartbeat
data. In this regard, the microcontroller, upon processing the
received signal as discussed herein, may process the data into
small subsets representative of user physiology. For example, such
movement detection algorithms may be implemented in accordance with
the methodologies disclosed in any of U.S. Patent Application Publ.
No. 2009/0203972, mentioned previously, International Patent
Application No., PCT/US14/045814, the entire disclosures of which
are each incorporated herein by reference.
[0130] The received signal data may be stored within memory in the
digital sensor, such as the memory accessed by the microcontroller.
As illustrated in FIG. 12, the microcontroller 508 may be connected
to memory 524. As previously explained, the memory 524 may include
SD cards, microSD cards, flash, etc. While the memory is
illustrated as being separate from the microcontroller in FIG. 12,
the memory 524 may be integrated into the microcontroller. The data
may be logged into the memory at a speed of 64 bps, or more or
less, depending on the type of memory. The amount of data stored
may be dependent upon the size of the memory used in the digital
sensor. For example, the memory 524 may save 12 hours or 24 hours
of user data.
[0131] Optionally, the microcontroller 508 may also be programmed
to detect physiological data based on processing of the motion
signals (e.g., respiration and/or cardiac signals). For example, it
may be programmed to generate data such as time t0 sleep, sleep
duration, time of sleep states, absent sections, unknown section,
efficiency scores and/or other detected information, such as
detected sleep disordered breathing event scores (e.g., an
Apnea/hypopnea count (AHI)). Such data generation may be
implemented in accordance with the methodologies disclosed in U.S.
Patent Application Publ. No. 2016/0151603, the entire disclosure of
which is incorporated herein by reference.
[0132] The microcontroller 508 may also control the output of data.
As illustrated in FIG. 12, the microcontroller may be connected to
an NFC transceiver device, such as an NFC card emulator 522 which
can be read by an external device such as a smartphone at 212 kbps,
or more or less. While an NFC device is discussed, other
technologies may also be implemented such as LTE, Wi-Fi and
Bluetooth. The NFC card emulator 522 may also contain data which,
when being read by a device, causes the device to launch an
application(s) which reads the data from the memory 524 of the
sensor. In this regard, the external device may `tap` the sensor to
read the NFC card emulator 522, thereby causing the application to
launch on the external device.
[0133] Upon launching the application, the external device may
retrieve a user's physiological data, from a certain period of
time, such as 24 hours, or other amounts of time stored in the
memory. In this regard, the NFC card emulator 522 may retrieve data
from the memory 524, assisted by instructions from the
microcontroller 508. In some embodiments, the retrieved data may be
automatically backed up into the application and/or onto a separate
cloud server.
[0134] As illustrated in FIG. 13, the retrieved data may then be
displayed on a display of the external device. The display may
summarize the data which is received by the external device, such
as data obtained while a user slept. In the example illustrated in
FIG. 13, data such as time t0 sleep, sleep duration, time of sleep
states, absent sections, unknown section, etc., may be displayed in
graph and/or chart form. Additionally, the external device may
determine and/or display sleep, or other condition related data
such as sleep stages related data, sleep efficiency scores and/or
other detected information, such as detected sleep disordered
breathing event scores, e.g., (AHI) received from the
microcontroller. However, in some cases, the smart phone may itself
obtain such information simply by receiving and processing the raw
motion signal (e.g., I/Q signals) from the sensor.
[0135] The sensor may also include other digital outputs. In this
regard, the sensor may include outputs such as RS232, serial, USB,
etc. Output via the digital outputs may occur at 64 bps and include
a 50 .mu.V signal resolution. External devices connected to these
digital outputs may receive data and otherwise function as outlined
above in regard to the NFC connection. In addition the digital
outputs may provide raw I/Q data for external processing or
storage.
[0136] The digital sensor may also include analogue outputs. For
example, the microcontroller may be configured to generate analogue
I/Q sensor signals by converting the digital I/Q signals into
respective analogue signals using a digital to analogue converter
(DAC). The DAC may be a 10 bit DAC, or more or less. The analogue
IQ signal may then be passed via the analogue outputs. The analogue
outputs may pass the analogue signals at a set bit rate a set bit
width modulation, such as 64 bps utilising 10 bit pulse width
modulation (PWM). Thus, the sensor may then output the re-generated
analog I/Q signals, each representing a raw motion signal from the
sensor.
[0137] In this specification, the word "comprising" is to be
understood in its "open" sense, that is, in the sense of
"including", and thus not limited to its "closed" sense, that is
the sense of "consisting only of". A corresponding meaning is to be
attributed to the corresponding words "comprise", "comprised" and
"comprises" where they appear.
[0138] While particular embodiments of this technology have been
described, it will be evident to those skilled in the art that the
present technology may be embodied in other specific forms without
departing from the essential characteristics thereof. The present
embodiments and examples are therefore to be considered in all
respects as illustrative and not restrictive. It will further be
understood that any reference herein to subject matter known in the
field does not, unless the contrary indication appears, constitute
an admission that such subject matter is commonly known by those
skilled in the art to which the present technology relates.
* * * * *