Remote Heart Rate, Breathing Rate Measurement

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Remote Heart Rate & Breathing Rate Detection
Using Far-field Diverse Wavelength, Ratiometric Differential Interferometry
In the form of Low-Power 10-GHz to 25-GHz Microwave "Doppler" [*] RADAR
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Examples of System Use ^-_-

	-<---->-
^-_-^-_-^-_-System used in battlefield environment for "Remote Triage."^-_-

The Ultimate Lie Detector

Initial detection for weapons and biometrics evaluation

	Individual interviews
Hand held unit, detects weapons and measures biometrics


Public Events	Truck Drivers

Hear Heart Sounds after Voltage to Frequency conversion

Another View of Heart Sounds after Voltage to Frequency Conversion

CW "Doppler" RADAR using GUNN Oscillator, Varactor & Diode Detector (mixer)

Refresher on Standing Wave Ratio (SWR)
Mouse-Over image to see animation

Mouse-Over image to see animation

Derived Amplitude Deltas
(Detected Heart Beat Waveforms)

Standing Waves

Amplitude deltas are derived as a function of Standing-Wave slope excursion caused by target motion, i.e., the greater the motion the larger the excursion.

Excessive motion causing excursions greater than 90° results in severe distortion.

Note the weak amplitudes at C and E; and the frequency doubling (folding) at D.
Optimum responses are shown by A and B.

. .

Far-field Diverse Wavelength, Ratiometric Differential Interferometry

Doppler has become the generic term used to describe these families of devices.

It is important to note that in this application, of the two properties at play--Constructive and Destructive Interference; and the Doppler Effect--Interference, not Doppler is the First Order Effect.

Dual Frequency Differential Approach
This Differential approach is an effort to overcome the variations in signal strength due to SWR nulls. These variations are caused by target position verses WL of the incident µwave energy--as represented in the above plots.

Dual Standing Waves due to frequency shifting of the Gunn oscillator, e.g., ~10 GHz and ~20 GHz

The Measurement is the Differential of the amplitude deltas of the two wavelengths, measured from standing-wave slope to standing-wave slope.

The system is pulse "Doppler" and received signals are sampeled. This is done to reduce RF exposure to the subject; resulting in nW/C² instead of mW/C².

Beat intervals related to WL ratios
note: 100% and 75% have the longest continuos interval between beat minima

Remote Heart Rate Measurement System Block Diagram

FSK Gunn Osc, Detector & pre-amp

Dual Sample & Hold
for channel separation

VGAs for gain balancing,

Differential Amplifier
for common artifact rejection

In order for this Differential system to work properly, It is important that both channel's gains be equal.

See Schematic Below----

Gain Tracking Fader Plot

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Remote Heart Rate & Breathing Rate Detection *_-*_-*_- Special Additions &

Modifications Page_-*_-*_-*

Suggested Apparatus Configuration for R & D Testing

Transmitter:

Emitter type: GUNN or IMPATT (lowest noise device required)

Modulation: CW & Pulsed (for signal processing NOT for Peak Power) note: IMPATT is typically pulsed; GUNN can be pulsed. (GUNN pulsed PO = CW PO)

Output: > 50mW

Delta Freq.: VCO (digital VCO ?)

Freq. Range(s): 10 GHz to 45 GHz; in several sub-bands (multiple oscillator sources will be necessary), e.g., 18-26 GHz, 26-35 GHz, 35-45 GHz

Receiver:

Shottkey microwave Mixer/Detector diodes BW >40 GHz, Waveguide mounted

Spatial Diversity Detector Array
Waveguide mounted diode array with spacing between diode mounts < 45 degrees of WL (for ease of construction, spacing can be delta + 1 WL, i.e., 0’ + 360’ = 0’, 40’ + 360 = 40’, 80’ + 360’ = 80’, etc.). see diagram

LO injection from Transmitter to receiver is by waveguide coupling with attenuator.

Antennas:

Separate Transmitter and Receiver Antennas

Small Pyramidal Horn antennas with beam forming dielectric "lens" (low sidelobes) at exit/entrance. Overall size of structure to be dictated by customer requirements. However, to aid in development, antenna should start off larger than finial version.

Potential problem areas and possible solutions

Problem	Solutions
1)_ Clutter due to motions of intervening foliage, e.g., grasses, etc.	a. "Pulse Doppler" modulation with Range Gating of Received signals.[2] b. Range Coding with secondary modulation.[3]
2)_ Variation in system sensitivity due to target/device distance verses WL nulls.	a. Dual Frequency Differential (present) b. Spatial Diversity Detector Array see diagram
3)_ Excessive close-in gain	a. Use of dual modulation for range discrimination. By selection of one modulation frequency, device is most sensitive in that range cell: sensitivity increases in a linear fashion, similar to pulsed radars.[3]

Ref.
[2]

[3]

Spatial Diversity Diode Detector Array,
using effective fractional WL spacing (S < 45°)

Waveguide mounted diode array with spacing between diode mounts < 45 degrees of WL (for ease of construction, spacing can be delta + 1 WL, i.e., 0’ + 360’ = 0’, 40’ + 360 = 40’, 80’ + 360’ = 80’, etc.). see diagram

Separate Transmitter & Receiver
with beam forming dielectric "lens" (low sidelobes)

Separate Transmitter & Receiver using LO Spill-over Injection

Transceiver

Gunn Transceiver prospective view

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One Embodiment, Schematic

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