A LOW COST RADAR SYSTEM FOR HEARTBEAT DETECTION
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A LOW COST RADAR SYSTEM FOR HEARTBEAT DETECTION Dr. Eric K. Walton The Ohio State University ElectroScience Laboratory 1330 Kinnear Road, Columbus, OH 43212 Mr. Benjamin K. Ozcomert Upper Arlington High School, Upper Arlington OH. THIS PROJECT SPONSORED BY ESL - CERF.

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This project sponsored by esl cerf

A LOW COST RADAR SYSTEM FOR HEARTBEAT DETECTIONDr. Eric K. WaltonThe Ohio State University ElectroScience Laboratory1330 Kinnear Road, Columbus, OH 43212Mr. Benjamin K. OzcomertUpper Arlington High School, Upper Arlington OH


This project sponsored by esl cerf

THIS PROJECT SPONSORED BYESL - CERF

The Ohio State University ElectroScience Laboratory Consortium on Electromagnetics and Radio Frequencies (ESL-CERF)


Cerf low cost radar

CERF; LOW COST RADAR

  • Frequency Synthesizer

  • Windfreak SynthNV module

  • based on the Analog Devices wideband fractional-N synthesizer chip (with integrated VCO)

  • Analog Devices ADF-4350

  • This mixed-signal chip can output signals in the 137-4,400 MHz range.

  • This chip has enabled a number of very low cost modules to be developed.

  • Our cost was $574.

  • This module is very simple to set up and use.

  • The USB port controls the device as well as providing power.

  • signal output port

  • RF reference signal input port available as option.

  • power sense port

  • The optional reference signal input port can be used for setting up several units coherently.

  • The power sense port can be used to measure a received signal level, a

  • nd thus this small unit can independently be used as a scalar network analyzer.

  • The internal microprocessor can be programmed to operate independently by setting it to a particular frequency and power level.

  • It can even be programmed to perform a step frequency scan automously.

Photo of Windfreak SynthNV module


Based on analog devices adf 4350 wideband synthesizer with integrated vco

BASED ON ANALOG DEVICES ADF 4350Wideband synthesizer with integrated VCO


Spectrum analyzer testing

Spectrum Analyzer Testing

FROM SPECTRUM ANALYZER TESTING;

NOTE THE SIDELOBE STRUCTURE

1.5 GHZ

3.0 GHZ

3.8 GHZ


Cerf low cost radar1

CERF; LOW COST RADAR

  • I/Q Mixer (DEMODULATOR)

  • There are a large number of UWB mixers available,

  • Most require associated components (amps for LO and LP filters and amps for the IF output.

  • We wanted to operated down to DC.

  • We selected the Polyphase Microwave quadrature demodulator as a compromise between cost and performance.

  • Bandwidth from 0.5 to 4.0 GHz with built in LO amplifier and I/Q low pass filters.

  • Characteristics;

    • LO/RF freq.500-4,000 MHz

    • I/Q bandwidthDC-275 MHz (50Ω)

    • Input IP3+30 dBm

    • Input P1+12 dBm

    • Amp. Imbal.+/- 0.05 dB

    • Phase Error+/- 0.5 Deg.

    • LO Power+0 dbm

    • DC supply+/- 5 VDC

  • This unit was purchased and tested using bench top laboratory equipment and was found to meet specifications.

  • The unit was offered to The OSU ESL at an educational discount price of only $918.75. A photo of the unit is given in figure 7.

$918.75.

Polyphase Microwave Inc.; 1111 W 17TH ST, STE 200

Bloomington, IN 47404


Cerf low cost radar2

CERF; LOW COST RADAR


Cerf low cost radar a d converter

CERF; LOW COST RADARA/D CONVERTER

  • MEASUREMENT COMPUTING USB-7202

  • ONE A/D PER CHANNEL

  • UP TO 8 SIMULTANEOUS

  • INDEPENDENT RANGE SETTINGS

  • 16-BITS

  • USB POWERED

  • 100 KS/S CUMULATIVE RATE

  • (IE; 50 KS/S EACH CHAN. FOR TWO ETC.)

  • SIMULTANEOUS SAMPLING

  • DOUBLE SPEED IN BURST MODE (32 K INTERNAL FIFO)

$399


Cerf low cost radar3

CERF; LOW COST RADAR

TESTING RESULTS

0.5-4.4 GHz

1-12 GHz ridge-waveguide

UWB horns

3 DB SPLITTER

SYNTH

USB

I

I/Q

MIXER

A/D

3.25 AND 5.88 INCH

DIAMETER SPHERES

Q

USB

COMPUTER


Cerf low cost radar4

CERF; LOW COST RADAR

IN PHASE AND QUADRATURE

COMPONENTS VS. FREQUENCY

EXAMPLE RESULTS FOR 5.88 IN. DIA. SPHERE


Cerf low cost radar5

CERF; LOW COST RADAR


This project sponsored by esl cerf

EXAMPLE STABILITY TEST

IT IS CRITICAL THAT THE RADAR SYSTEM BE STABILE AND REPEATABLE FROM SCAN TO SCAN SO THAT SCANS CAN BE DIRECTLY COMPARED AND SO THAT THE BACKGROUND CAN BE SUBTRACTED FROM THE DATA OF INTEREST AS WELL AS SO THAT THE “THRU” DATA CAN BE USED FOR NORMALIZATION.

As a stability test, the empty target support at the beginning of the series can be compared to the one at the end; (time elapsed = 20 minutes) Note the difference is less than -25 dB.


This project sponsored by esl cerf

STABILITY TEST; TIME DOMAIN

  • IF WE LOOK AT THE EMPTY VS. EMPTY DATA IN THE TIME DOMAIN, WE NOTE THAT THE MOST STABILE REGION IS NEAR THE ANTENNA COUPLING REGION. (difference below -35 dB)

  • IT IS LESS STABILE AT TIMES GREATER THAN 20 ns. This may be simply due to people moving around near the measurement system.


Cerf low cost radar6

CERF; LOW COST RADAR

Green = no-target data

Blue = raw sphere data

Red = sphere data divided by thru data

DB

FREQUENCY (MHZ)


Cerf low cost radar7

CERF; LOW COST RADAR

FULL TIME SCALE

Coupling in pow. Divider

(thus negative time)

DB

TIME DOMAIN (ns)


Cerf low cost radar8

CERF; LOW COST RADAR

DB

TIME (ns)

NOTE;

background subtraction suppresses the room clutter (background) by more than 30 dB.

Normalization to the “thru” connection removes the effects of system and cables. (IE: moves the response from 11.2 ns to 4.2 ns. {antennas and propagation distance remain})


Cerf low cost radar9

CERF; LOW COST RADAR

We can also do this for the 3.25 in diam sphere


Example full calibration test of radar

EXAMPLE FULL CALIBRATIONTEST OF RADAR


Full calibration example

FULL CALIBRATION EXAMPLE

LET US DO A FULL CALIBRATION TO REFERENCE SPHERES

USING EXACT SPHERE RCS FOR REFERENCE.

H. L. Thal Jr., “Exact Circuit Analysis of Spherical Waves,” IEEE Transactions on Antennas and Propagation, vol. AP-26, No. 2, March 1978.

SET OF TEST TARGETS AND REFERENCE SPHERES

APPROX 20 INCHES

RADAR

1-12 GHZ

RIDGED WAVEGUIDE HORNS

STYROFOAM

COLUMN


Full calibration example1

FULL CALIBRATION EXAMPLE

MEASURE TARGETS OF INTEREST (S21 VS. FREQ.)

SUBTRACT BACKGROUND (EMPTY TARGET SUPPORT)

TRANSFORM TO TIME DOMAIN

ZERO OUT ALL EXCEPT TARGET ZONE

TRANSFORM BACK TO FREQUENCY DOMAIN

NORMALIZE TO REFERENCE SPHERE

MULTIPLY BY EXACT RCS OF REFERENCE SPHERE

Note units of complex voltage and complex meters.


Full calibration example2

FULL CALIBRATION EXAMPLE

FOR THE FOLLOWING EXAMPLE, WE WILL USE

A 3.5 INCH DIAM. SPHERE AS THE REFERENCE,

AND

A 2.5 INCH DIAM. SPHERE AS THE TARGET OF INTEREST.

THAT WAY, WE CAN DOUBLE CHECK OUR ACCURACY BY

COMPARING THE CALIBRATED 2.5 INCH MEASURED RCS VALUES WITH THE

EXACT SOLUTION FOR THE 2.5 INCH SPHERE TARGET.

The set of measurements on the different targets took place over a period of approximately 1 hour.


Full calibration example3

FULL CALIBRATION EXAMPLE

NOTE THE I/Q BALANCE

NOTE THE GAIN DROP-OFF OF THE RADAR

NOTE THE RESULT OF SUBTRACTING THE EMPTY SUPPORT DATA.


Full calibration example4

FULL CALIBRATION EXAMPLE

INCREASING NOISE

NOTE THE RESULT OF SUBTRACTING THE BACKGROUND AND THEN

NORMALIZING TO (DIVIDING BY)THE REFERENCE SPHERE DATA.


Full calibration example5

FULL CALIBRATION EXAMPLE

ESPECIALLY REMOVE THE

DIRECT HORN TO HORN

COUPLING TERM

SET ALL OUTSIDE THIS TARGET ZONE TO ZERO

NEXT WE TRANSFORM THE SUBTRACTED & NORMALIZED DATA TO THE TIME DOMAIN.


Full calibration example6

FULL CALIBRATION EXAMPLE

PLOT OF THE EXACT RCS (DBSM) OF THE 3.5 INCH SPHERE .


Full calibration example final calibration result

FULL CALIBRATION EXAMPLE(FINAL CALIBRATION RESULT)

NOTE THE AGREEMENT BETWEEN THE CALIBRATED TARGET AND THE EXACT CALCULATION.


Full calibration example7

FULL CALIBRATION EXAMPLE

WE CAN ALSO DO THIS FOR A 0.75 INCH DIAM SPHERE AS A TARGET.

NOTE AGREEMENT


Full calibration example8

FULL CALIBRATION EXAMPLE

IN THIS CASE, THE TARGET OF INTEREST IS A 50 CALIBER BULLET (NOSE ON)

0.75 “ D SPHERE EXACT

BULLET

WE INCLUDE THE EXACT RCS OF THE 0.75 INCH DIAM. SPHERE AS A REFERENCE.


Full calibration example9

FULL CALIBRATION EXAMPLE

WE ALSO DID A MOM CALCULATION FOR THAT 50 CAL BULLET (Thanks; THE HONG LEE)


This project sponsored by esl cerf

FULL CALIBRATION EXAMPLE

Overlay theoretical with experimental RCS (DBSM).

BROADSIDE

RCS (DBSM)

NEAR NOSE ON

BULLET RADAR DATA

FREQ

NOT “TOO” BAD. 


Full calibration example10

FULL CALIBRATION EXAMPLE

  • CONCLUSIONS;

  • WE CAN BUILD A STEP FREQUENCY SYNTHESIZED RADAR USING MODERN MIXED SIGNAL MICROCHIPS FOR LESS THAN $2000.

  • IT IS FULLY SOFTWARE CONTROLLED.

    • USB INTERFACE TO LAPTOP

    • FULLY PROGRAM CONTROLLED IN MATLAB (IN OUR CASE)

  • WE CAN MEASURE RADAR TARGETS VERSUS FREQUENCY AND TRANSFORM THE RESULTS TO THE TIME DOMAIN.

  • WE CAN PERFORM FULL CALIBRATIONS ON THE DATA TO YIELD RADAR SCATTERING IN DBSM.

    • WITH GOOD DYNAMIC RANGE

    • AND GOOD TIME STABILITY.

  • WE CAN ALSO USE THIS RADAR IN THE SINGLE FREQUENCY MODE TO MEASURE DOPPLER.


This project sponsored by esl cerf

HUMAN HEARTBEAT

One of our goals is to extract I/Q Doppler waveform signatures from the human heartbeat.

This is an I/Q Doppler measurement done with an ESL network analyzer on a volunteer.

MEASURED USING NETWORK ANALYZER IN CW VS. TIME MODE.

Q

1.5 GHZ

Note the repeating I/Q pattern synchronized with the heartbeat. We hope to collect more of this type of data using our new portable radar and to compare the I/Q signature with MRI or EKG data.

I/Q PATTERN

10 HEARTBEATS

I


This project sponsored by esl cerf

HUMAN HEARTBEAT

[HOW CAN WE ASCRIBE MEANING TO THESE TRAJECTORIES?]

1.5 GHz Trajectory (EKW volunteer)

1.5 GHz Trajectory (EKW volunteer)

2.0 GHz Trajectory (EKW volunteer)

2.0 GHz Trajectory (EKW volunteer)

MEDICAL INTERPRETATIONS?


Full calibration example11

FULL CALIBRATION EXAMPLE

QUESTIONS?

DR. ERIC K. WALTON

THE OHIO STATE UNIVERSITY

ELECTROSCIENCE LABORATORY

1330 KINNEAR ROAD

COLUMBUS, OHIO 43212

[email protected]

Office 614/292-5051; cell 614/537-5609

6. Acknowledgements

The authors wish to thank The Ohio State University ElectroScience Laboratory Consortium on Electromagnetics and Radio Frequencies (ESL-CERF) (sponsors of this project)

as well as Polyphase Corporation for their assistance.


This project sponsored by esl cerf

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