Complex signal demodulation and angular demodulation for non-contact vital sign detection

• US 8,814,805 B2
• Filed: 12/08/2008
• Issued: 08/26/2014
• Est. Priority Date: 12/07/2007
• Status: Active Grant

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Lin, Jenshan, Li, Changzhi
• Primary Examiner(s): D'Angelo, Michael
• Assistant Examiner(s): WESTON, TIFFANY C
• Application Number:
  US12/743,103
• Publication Number:
  US 20100241010A1
• Time in Patent Office: 2,087 Days
• Field of Search: 600529-543, 702/56
• US Class Current: 600/534
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/1114 Tracking parts of the body
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G01S 7/2886 using I/Q processing

Abstract

Methods for recovering a detected signal in non-contact vital sign detection are provided. According to one embodiment, a detected reflected signal from a non-contact vital sign detection system can be received and provided along I channel and Q channel signal lines. A complex signal S(t) can then be reconstructed from the I channel and Q channel signal lines through complex signal demodulation. A Fourier transform can be used to obtain the detected signal'"'"'s spectrum for spectrum analysis. Angular demodulation can be used to recover the information corresponding to original body movement. The complex signal demodulation and angular demodulation techniques used to provide information to determine original body movement are capable of avoiding the null detection point without limitations on frequency tuning or channel selection.

Claims

1. A method for recovering a detected signal in non-contact vibration detection, comprising:

reconstructing a complex signal from an I channel and a Q channel for a received reflected signal to create a reconstructed complex signal;

applying a Fourier transform to the reconstructed complex signal to obtain a detected spectrum;

extracting phase angle information of the reconstructed complex signal from the detected spectrum; and

obtaining original vibration information by analyzing the phase angle information,

wherein reconstructing the complex signal from the I channel and the Q channel is performed using the following relation;

2. The method according to claim 1, wherein obtaining original vibration information comprises obtaining original target movement information.

3. The method according to claim 2, further comprising obtaining vital sign information from the original target movement information.

4. The method according to claim 1,

wherein extracting phase angle information of the reconstructed complex signal from the detected spectrum comprises calibrating out a DC offset of the detected spectrum.

5. The method according to claim 1,

wherein the original vibration information comprises a first vibration frequency of the first periodic vibration and a second vibration frequency of the second periodic vibration.

7. The method according to claim 1, wherein applying a Fourier transform to the reconstructed complex signal to obtain a detected spectrum;

extracting phase angle information of the reconstructed complex signal; and

obtaining original vibration information by analyzing the phase angle information reconstructing the complex signal from the I channel and the Q channel comprises applying a Fourier transform to the reconstructed complex signal to obtain a detected spectrum;

extracting phase angle information of the reconstructed complex signal; and

obtaining original vibration information by analyzing the phase angle information

via the non-transitory media storage device, wherein the non-transitory media storage device has machine-readable instructions stored thereon for;

applying a Fourier transform to the reconstructed complex signal to obtain the detected spectrum;

extracting phase angle information of the reconstructed complex signal; and

obtaining original vibration information by analyzing the phase angle information.

8. The method according to claim 5, wherein the first periodic vibration is due to heartbeat and the second periodic vibration is due to respiration.

9. The method according to claim 4, wherein calibrating out the DC offset of the detected spectrum comprises subtracting a complex average from every time domain sliding window.

10. The method according to claim 1, wherein extracting the phase angle information of the reconstructed complex signal from the detected spectrum comprises applying the following relation:

11. The method according to claim 1, further comprising:

transmitting a transmit signal at a target such that the transmit signal is reflected by the target to create a reflected signal; and

receiving the reflected signal from the target to create the received reflected signal.

12. The method according to claim 11, wherein the transmit signal has a frequency in a range of 9 kHz-1 terahertz.

13. The method according to claim 11, wherein the transmit signal has a frequency in a range of 1 GHz-30 GHz.

14. The method according to claim 11, wherein the I channel is a real component I of the received reflected signal, wherein the I channel is in-phase with the transmit signal, wherein the Q channel is an imaginary quadrature component Q of the received reflected signal, wherein the Q channel is 90 degrees out of phase with the transmit signal.

15. The method according to claim 1, wherein analyzing the phase angle information comprises determining how fast a phase angle of the reconstructed complex signal changes.

16. The method according to claim 15, wherein a vibration rate of the target is how fast the phase angle of the reconstructed complex signal changes.

6. A method for recovering a detected signal in non-contact vibration detection, comprising:

reconstructing a complex signal from an I channel and a Q channel for a received reflected signal to create a reconstructed complex signal;

applying a Fourier transform to the reconstructed complex signal to obtain a detected spectrum;

extracting phase angle information of the reconstructed complex signal; and

obtaining original vibration information by analyzing the phase angle information,

wherein reconstructing the complex signal from the I channel and the Q channel is performed using the following relation;

17. A method for cancelling random target movement effects in non-contact vibration detection, comprising:

transmitting a first transmit signal from a first position at a target such that the first transmit signal is reflected by the target to create a first reflected signal, wherein the first transmit signal has a first polarization;

transmitting a second transmit signal from a second position at the target such that the second transmit signal is reflected by the target to create a second reflected signal, wherein the second transmit signal has a second polarization, wherein the second position is different than the first position, wherein the second polarization is different than the first polarization;

receiving the first reflected signal to create a first received reflected signal;

receiving the second reflected signal to create a second received reflected signal;

reconstructing a first complex signal from a first I channel and a first Q channel for the first received reflected signal to create a first reconstructed complex signal, and reconstructing a second complex signal from a second I channel and a second Q channel for the second received reflected signal to create a second reconstructed complex signal; and

combining the first reconstructed complex signal and the second reconstructed complex signal to produce a combined signal,

wherein reconstructing a first complex signal from a first I channel and a first Q channel for a first received reflected signal to create the first reconstructed complex signal and reconstructing a second complex signal from a second I channel and a second Q channel for a second received reflected signal to create the second reconstructed complex signal are performed via a non-transitory media storage device having machine-readable instructions stored thereon for performing reconstructing a first complex signal from a first I channel and a first Q channel for the first received reflected signal to create the first reconstructed complex signal and reconstructing a second complex signal from a second I channel and a second Q channel for a second received reflected signal to create the second reconstructed complex signal.

18. The method according to claim 17, wherein reconstructing the first complex signal from the I channel and the first Q channel for a first received reflected signal to create the first reconstructed complex signal and reconstructing a second complex signal from a second I channel and a second Q channel for a second received reflected signal to create the second reconstructed complex signal are performed using the following relations:

20. The method according to claim 17, wherein combining the first reconstructed complex signal and the second reconstructed complex signal to produce a combined signal are performed via a non-transitory media storage device having machine-readable instructions stored thereon for performing combining the first reconstructed complex signal and the second reconstructed complex signal to produce a combined signal.

21. The method according to claim 18, wherein) λ

₁ and λ

₂ are within 0.0001% of each other.

22. The method according to claim 18, wherein the first periodic vibration is due to a heart beating and the second periodic vibration is due to respiration.

23. The method according to claim 17, wherein combining the first reconstructed complex signal and the second reconstructed complex signal to produce the combined signal comprises performing a convolution and frequency shift in the frequency domain.

24. The method according to claim 23, wherein combining the first reconstructed complex signal and the second reconstructed complex signal to produce the combined signal comprises applying the following relation:

25. The method according to claim 24, wherein the first periodic vibration is due to a heart beating and the second periodic vibration is due to respiration.

26. The method according to claim 24, wherein the combined signal is approximated to:

27. The method according to claim 17, further comprising:

applying a Fourier transform to the combined signal to obtain a detected spectrum;

extracting phase angle information of the combined signal; and

obtaining original target movement information by analyzing the phase angle information.

28. The method according to claim 27, further comprising:

calibrating out a DC offset of the detected spectrum.

29. The method according to claim 18, wherein λ

₁ and λ

₂ are within 0.0001% of each other.

30. The method according to claim 17, wherein the second polarization is orthogonal to the first polarization.

31. The method according to claim 17,

wherein the first position is in front of the target and the second position is in back of the target.

19. A method for cancelling random body movement effects in non-contact vibration detection, comprising:

transmitting a first transmit signal from a first position at a target such that the first transmit signal is reflected by the target to create a first reflected signal, wherein the first transmit signal has a first polarization;

transmitting a second transmit signal from a second position at the target such that the second transmit signal is reflected by the target to create a second reflected signal, wherein the second transmit signal has a second polarization, wherein the second position is different than the first position, wherein the second polarization is different than the first polarization;

receiving the first reflected signal to create a first received reflected signal;

receiving the second reflected signal to create a second received reflected signal;

reconstructing a first complex signal from a first I channel and a first Q channel for the first reflected signal and reconstructing a second reconstructed complex signal from a second I channel and a second Q channel for the second received reflected signal; and

combining the first reconstructed complex signal and the second reconstructed complex signal to produce a combined signal,

wherein reconstructing a first complex signal from a first I channel and a first Q channel for the first reflected signal and reconstructing a second reconstructed complex signal from a second I channel and a second Q channel for the second received reflected signal are performed via hardware.