This paper presents the preliminary results of a novel approach for multi-target vital-signs monitoring using an electromagnetic-based Doppler radar. The fundamentals of the proposed approach are based on multi-beam antennas, phased arrays systems, and beam-forming networks. For the purpose of demonstration, we have designed and implemented a prototype dual-beam phased-array continuous-wave Doppler radar operating at 2.4 GHz. Measurement results confirmed the feasibility of the proposed method. Experimental measurements showed that for the first time, the breathing rates of two individuals can be monitored at the same time and using the same frequency. The proposed dual-beam system prevents the phase collision of the signatures of the targets and hence provides multi-person detection capability for the system. Multibeam Phased Array CW Radar, Non-contact vital signs monitoring, Concurrent radiation Hybrid beamforming

1. 1FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Multi-Target Vital-Signs Monitoring Using a
Dual-Beam Hybrid Doppler Radar
Mehrdad Nosrati1, Shahram Shahsavari2, and Negar Tavassolian1
1 Stevens Institute of Technology, Hoboken, NJ, 07030, USA
2 Tandon School of Engineering, New York University, Brooklyn, NY, 11201, USA

2. 2FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Outline
• Introduction
• Research Objective and Motivation
• System Design and Analysis
• Results
• Conclusion

3. 3FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Introduction
What will happen if we get a heart attack while sleeping?
Critical need:
 Early detection to earn more response time
Every 40s
800,000 deaths annually
$250 B

4. 4FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Introduction
• Doppler radars provide useful information of the target(s) such as range, velocity, and
direction.
Doppler Radars Applications:
• Autonomous vehicles
• Weather forecast
• Target identification (airplanes, missiles)
• Vibration monitoring (bridges, buildings)
• Medical applications

5. 5FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Research Motivation and Objective
• Problems with the current Doppler radar-based sensors:
• Limited to single-person monitoring at each time
• Phase Collision at the receiver ruins the signals of multiple subjects
• Extremely vulnerable to the presence of other moving targets
• Our Approach:
• Using MIMO beam-forming techniques
• Design of a multi-beam continuous wave Doppler radar

6. 6FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
System Design and Implementation
Digital beam-forming
One RF chain
per antenna
element
Multiple
beams on a
shared
antenna array
Best
performance,
Most complex
Hybrid beam-forming
RF chains are
less than
antenna
elements
#of beams=
#of RF chains
Less complex
lower
performance

7. 7FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
System Design and Implementation
Dual-Beam Active Phased-Array (DAPA) Doppler Radar:
• Based on hybrid beam-forming technique
• Generates simultaneous and independent beams

8. 8FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Radiation Pattern Measurements
The prototype system has been tested and characterized.
• Phased Shifter Calibration
• Chamber Measurements
• Outdoor Measurements

9. 9FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Radiation Pattern Measurements
-100 -75 -50 -25 0 25 50 75 100
Angle, (degree)
-30
-20
-10
0
NormalizedAmplitude(dB)
Dual-Beam Radiation Pattern at =0 Vs
Simulation
Meas. Chamber
Meas. Rooftop
-100 -75 -50 -25 0 25 50 75 100
Angle, (degree)
-30
-20
-10
0
NormalizedAmplitude(dB)
Dual-Beam Radiation Pattern at =0 Vs
Simulation
Meas. Chamber
Meas. Rooftop
-100 -75 -50 -25 0 25 50 75 100
Angle, (degree)
-30
-20
-10
0
NormalizedAmplitude(dB)
Single Beam Radiation Pattern Directed at =0 Vs
Simulation
Meas. Chamber
Meas. Rooftop
-100 -75 -50 -25 0 25 50 75 100
Angle, (degree)
-30
-20
-10
0
NormalizedAmplitude(dB)
Single Beam Radiation Pattern Directed at =0 Vs
Simulation
Meas. Chamber
Meas. Rooftop

10. 10FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Human Tests and Results
• 4 healthy volunteers participated
• 6 different groups: 4
2
= 6
Two tests for each group:
1. Single beam mode
2. Dual beam mode
Group Single Beam Dual Beam
1 Fail Pass
2 Fail Pass
3 Fail Pass
4 Fail Pass
5 Fail Pass
6 Fail Pass

11. 11FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Human Tests and Results
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Frequency (Hz)
-30
-20
-10
0
NormalizedMagnitude(dB)
Output of Beam#1
Output of Beam#2
15 dB 11 dB
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Frequency (Hz)
-30
-20
-10
0
NormalizedMagnitude(dB)
Output of Beam#1.
Frequency spectrum of the
recorded signal while two
subjects were monitored
at the same time using the
radar in dual-beam mode.
0.29 Hz
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Frequency (Hz)
-30
-20
-10
0
NormalizedMagnitude(dB)
Output of Beam#2.
Frequency spectrum of the
recorded signal while two
subjects were monitored
at the same time using the
radar in dual-beam mode.
0.39 Hz
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Frequency (Hz)
-30
-20
-10
0
NormalizedMagnitude(dB)
Frequency spectrum of the recorded signal
while two subjects were monitored at the same
time using the radar in single-beam mode.
0.22 Hz

12. 12FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Summary

13. 13FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
• MIMO techniques can significantly improve biomedical
radars performance
• For the first time, we are able to monitor two subject’s vital
signs simultaneously using a CW Doppler radar
• The Beam-Forming approach does not increase the
resolution
• The Beam-Forming approach increases the system capacity
Conclusion

14. 14FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Thank You!

15. 15FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
There are two solutions:
1- Range Diversity: the time of arrival of different objects is not equal
 Complex and costly
 Range ambiguity
 Objects at the same distance can not be differentiated
2- Space Diversity:
• Beam-Switched Systems
 Easier to implement
 Only gives fixed beams
• Concurrent Multi-Beam Systems (our approach)
 Difficult to implement
 Ultimate performance
Differentiating more than one object?
t2
t4
t3
t1

16. 16FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Problem Statement: Example
 Problem:
When there are more than one person in the scene
• Signals will collide and mix together
 Our solution:
Generate multiple concurrent independent beams
• Different signals can be detected

17. 17FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Schematic of the system Beam-forming Network
System Architecture

18. 18FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Transmitter Specifications
RF Frequency 2.0 – 2.8 GHz
Antenna Ports 4
Power/Antenna Port -11.0 dBm
EIRP 0 dBm
Radar Mode CW
Phase Shifter Yes
VGA No
Phase Step 1.4°
Receiver Specifications
RF Frequency 2.0 – 2.8 GHz
Antenna Ports 4
Concurrent Beams 2
Sensitivity -80 dBm
Phase Shifter Yes
VGA Yes
Phase Step 1.4°
VGA Gain Control 30 dB
System Level Specifications

19. 19FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
System Implementation

20. 20FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
System Implementation
Transceiver Beam-forming network

21. 21FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Phased Shifter Calibration
0 45 90 135 180 225 270 315 360
Phase set-point (Degree)
-10
-5
0
5
10
Phaseerror(Degree)
Measured Without Calibration
Measured With Calibration Table
Block diagram of the
calibration flow
A photo of the
calibration set-up
The measured phase change of the
DPS before and after calibration
• The performance of any phased-array system depends on the phase shifter’s
accuracy and precision
• The digital phase shifters must be calibrated to compensate for the various errors.

22. 22FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Chamber Measurements

23. 23FR3A-2 Philadelphia, PA
Student Paper Competition Finalist
Sponsored by IEEE MTT-S Graduate Fellowship for Medical Applications
Outdoor Measurements