Accurate heart rate measurement by radar using adaptive harmonics filter

1. A method for heart rate measurement, comprising:

determining, with a computing device, a respiratory rate (RR) and respiration displacement from radar-measured cardiorespiratory motion data, wherein the radar-measured cardiorespiratory motion data is obtained using a 60 GHz radar;

adjusting, with the computing device, notch depths of a harmonics comb notch digital filter (HCNDF) based upon the respiration displacement;

generating, with the computing device, filtered cardiorespiratory data by filtering the radar-measured cardiorespiratory motion data with the HCNDF; and

identifying a heart rate (HR) from the filtered cardiorespiratory data.

2. The method of claim 1 , wherein the respiration displacement is determined from a respiration fundamental frequency and respiration demodulation-generated (DG) harmonics identified from the radar-measured cardiorespiratory motion data.

3. The method of claim 2 , wherein the notch depths are based upon amplitudes of the respiration fundamental frequency and the respiration DG harmonics or are based upon one or more ratios of the respiration fundamental frequency and the respiration DG harmonics.

4. The method of claim 1 , comprising adjusting notch frequencies of the HCNDF based upon the RR.

5. The method of claim 4 , wherein the notch frequencies of the HCNDF correspond to a fundamental frequency of the RR and harmonics of the fundamental frequency.

6. The method of claim 5 , wherein the HCNDF comprises notches corresponding to the fundamental frequency of the RR, a second harmonic frequency, and a third harmonic frequency.

7. The method of claim 6 , wherein the HCNDF further comprises notches corresponding to a fourth harmonic frequency and a fifth harmonic frequency.

8. The method of claim 1 , wherein notch widths of the HCNDF are based upon a length of a time window over which the radar-measured cardiorespiratory motion data was obtained.

9. The method of claim 8 , comprising adjusting the notch widths of the HCNDF in response to a change in the length of the time window.

10. The method of claim 9 , wherein the notch widths are reduced in response to an increase in the length of the time window.

11. A system, comprising:

radar circuitry configured to transmit a single-tone carrier signal and receive a cardiorespiratory motion signal reflected from a monitored subject, the radar circuitry comprising a Doppler radar transceiver coupled to transmit and receive antennas, wherein a radar transceiver chip comprises the radar circuitry and patch antennas as the transmit and receive antennas, where the radar transceiver chip and the patch antennas are disposed on a common substrate; and

signal processing circuitry configured to:

determine a respiration displacement from cardiorespiratory motion data based upon the cardiorespiratory motion signal;

adjust notch depths of a harmonics comb notch digital filter (HCNDF) based upon the respiration displacement;

generate filtered cardiorespiratory data by filtering the cardiorespiratory motion data with the HCNDF; and

identify a heart rate (HR) from the filtered cardiorespiratory data.

12. The system of claim 11 , wherein the notch depths are based upon amplitudes of a respiration fundamental frequency and respiration demodulation-generated (DG) harmonics identified from the cardiorespiratory motion data.

13. The system of claim 11 , wherein the signal processing circuitry is further configured to adjust notch frequencies of the HCNDF based upon a respiratory rate (RR) determined from the cardiorespiratory motion data.

14. The system of claim 11 , wherein notch widths of the HCNDF are based upon a length of a time window over which the cardiorespiratory motion data was determined.

15. A system, comprising: radar circuitry configured to transmit a single-tone carrier signal and receive a cardiorespiratory motion signal reflected from a monitored subject, the radar circuitry comprising a Doppler radar transceiver coupled to transmit and receive antennas, wherein the Doppler radar transceiver operates at 60 GHz; and

signal processing circuitry configured to:

determine a respiration displacement from cardiorespiratory motion data based upon the cardiorespiratory motion signal;

adjust notch depths of a harmonics comb notch digital filter (HCNDF) based upon the respiration displacement;

generate filtered cardiorespiratory data by filtering the cardiorespiratory motion data with the HCNDF; and

identify a heart rate (HR) from the filtered cardiorespiratory data.

16. The system of claim 15 , wherein the signal processing circuitry comprises data acquisition circuitry configured to sample quadrature signals of the cardiorespiratory motion signal and a processor configured to determine the respiration displacement and identify the HR based upon the sampled quadrature signals.

17. The system of claim 15 , wherein the respiration displacement is determined from a respiration fundamental frequency and respiration demodulation-generated (DG) harmonics identified from the cardiorespiratory motion data.

18. The system of claim 17 , wherein the notch depths are based upon amplitudes of the respiration fundamental frequency and the respiration DG harmonics.

19. The system of claim 15 , wherein the signal processing circuitry is further configured to adjust notch frequencies of the HCNDF based upon a respiratory rate (RR) determined from the cardiorespiratory motion data.

20. The system of claim 15 , wherein notch widths of the HCNDF are based upon a length of a time window over which the cardiorespiratory motion data was determined.