Determining presence and/or physiological motion of one or more subjects with quadrature doppler radar receiver systems

• US 20080119716A1
• Filed: 05/14/2007
• Published: 05/22/2008
• Est. Priority Date: 05/17/2006
• Status: Abandoned Application

• Current Assignee: University of Hawai'i
• Original Assignee: University of Hawai'i
• Inventors: Lubecke, Victor, Boric-Lubecke, Olga, Host-Madsen, Anders
• Application Number:
  US11/803,654
• Publication Number:
  US 20080119716A1
• Time in Patent Office: Days
• US Class Current: 600/407
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• 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 13/888 through wall detection
• CPC Class Codes: G01S 7/2886 using I/Q processing
• CPC Class Codes: G01S 7/415 Identification of targets based on measurements of movement associated with the target

Abstract

Systems and methods for determining presence and/or physiological motion of at least one subject using a Doppler radar system having a quadrature receiver are provided. In one example, the apparatus includes a transmitter for transmitting a source signal, a quadrature receiver for receiving the source signal and a modulated source signal (e.g., as reflected from one or more subjects), and logic for mixing the source signal and the received modulated source signal to generate in-phase (I) and quadrature (Q) data, whereby nulls in the signal are avoided. In one example, the quadrature receiver further includes logic for center tracking quadrature demodulation. The apparatus may further include logic for determining physiological motion (e.g., heart rate and/or respiration rate of a person) of a subject based on the source signal and the modulated source signal.

Claims

1. Apparatus for Doppler sensing of physiological motion of at least one subject, the apparatus comprising:

a quadrature receiver for receiving a source signal and a modulated source signal, the modulated source signal associated with a transmitted signal reflected from at least one subject; and

logic for mixing the source signal and the modulated signal to generate I and Q data.

2. The apparatus of claim 1, further comprising for non-linear demodulation of the received modulated source signal.

3. The apparatus of claim 2, further comprising logic for arctangent demodulation of the I and Q data.

4. The apparatus of claim 1, further comprising logic for demodulating the I and Q channel data to remove a null.

5. The apparatus of claim 1, further comprising logic for removing DC offset from the I and Q data.

6. The apparatus of claim 1, further comprising logic for center tracking compensation.

7. The apparatus of claim 6, further comprising logic for extracting information associated with an arc from the received signal and estimating a center of the arc.

8. The apparatus of claim 7, wherein the information is rotated prior to estimating the center of the arc.

9. The apparatus of claim 7, where the center of the arc is determined for each pair of points, and the results combined to get an improved estimate of the center.

10. The apparatus of claim 9, wherein the logic is the median.

11. The apparatus of claim 1, further comprising logic for compensating for a phase and amplitude imbalance factor.

12. The apparatus of claim 1, further comprising a phase shifter for introducing a local oscillator signal, and determining phase and amplitude imbalance between the received signal and the local oscillator signal.

13. The apparatus of claim 1, further comprising a voltage controlled oscillator for providing both the transmitted source signal and a local oscillator signal, wherein the local oscillator signal is further divided to provide two orthonormal baseband signals.

14. The apparatus of claim 1, wherein the quadrature receiver is analog.

15. The apparatus of claim 1, wherein the quadrature receiver is digital.

16. The apparatus of claim 1, further comprising logic for linear demodulation of the received modulated source signal.

17. The apparatus of claim 16, wherein the linear demodulation is a singular value decomposition.

18. The apparatus of claim 1, further comprising logic for performing a blind source separation process to isolate one of multiple subjects.

19. A data acquisition system for Doppler radar sensing of physiological motion of at least one subject, the data acquisition apparatus comprising:

an analog to digital converter; and

an automatic gain control unit, wherein the analog to digital converter and the automatic gain control unit are configured to increase the dynamic range of the system, one or both of modifying the DC offset value and gain for the signal of interest.

20. The data acquisition system of claim 19, wherein modifying the DC offset value comprises removing the DC offset.

21. The data acquisition system of claim 19, wherein modifying the DC offset value comprises removing the DC offset, and adjusting and recording the gain.

22. The data acquisition system of claim 19, further comprising tracking and removing a DC offset value.

23. The data acquisition system of claim 19, wherein modifying the DC offset value comprises removing and recording the DC offset, and adjusting and recording the gain.

24. The data acquisition system of claim 19, further comprising adjusting and recording the gain.

25. The data acquisition system of claim 19, further comprising a first analog to digital converter and a DAC for acquiring a DC offset value and outputting a reference.

26. The data acquisition system of claim 25, further comprising a VGA and a second analog to digital converter for providing feedback for the automatic gain control unit.

27. The data acquisition system of claim 19, further comprising logic for performing arctangent demodulation of the received signals.

28. A method for detecting presence and/or sensing physiological motion of at least one subject with a quadrature Doppler receiver, the method comprising the acts of:

receiving a source signal and a modulated source signal, the modulated source signal associated with a transmitted signal reflected from none or at least one subject; and

mixing the source signal and the modulated signal to generate I and Q data.

29. The method of claim 28, further comprising non-linearly demodulating the received modulated source signal.

30. The method of claim 29, further comprising combining the I and Q data using arctangent demodulation.

31. The method of claim 28, further comprising combining the I and Q data using arctangent demodulation and DC offset compensation.

32. The method of claim 28, further comprising compensating for a phase and amplitude imbalance factor of the analog quadrature receiver.

33. The method of claim 28, further comprising introducing a local oscillator signal and determining phase and amplitude imbalance between two analog quadrature receiver chains.

34. The method of claim 28, further comprising providing the transmitted source signal and a local oscillator signal to the receiver, wherein the local oscillator signal is further divided to provide two orthonormal baseband signals.

35. The method of claim 28, further comprising linearly demodulating the received modulated source signal.

36. The method of claim 35, wherein the linear demodulation is a singular value decomposition.

37. The method of claim 28, further comprising performing a blind source separation process to isolate one of multiple subjects.

38. The method of claim 28, further comprising providing the transmitted source signal and a local oscillator signal to the receiver, wherein the quadrature mixing is performed in digital domain.

39. A computer program product comprising computer-readable program code for sensing physiological motion of a subject in a Doppler radar system, the product comprising program code for:

determining presence and/or physiological motion associated with at least one subject from I and Q data output from a quadrature receiver, the I and Q data based on a source signal and a modulated source signal having been modified by at least one subject.

40. The computer program product of claim 39, further comprising program code for combining the I and Q data using arctangent demodulation.

41. The computer program product of claim 39, further comprising program code for combining the I and Q data using arctangent demodulation and DC offset compensation.

42. The computer program product of claim 39, further comprising program code for compensating for a phase and amplitude imbalance factor of a receiver.

43. The computer program product of claim 39, further comprising program code for linearly demodulating the received modulated source signal.

44. The computer program product of claim 39, further comprising program code for non-linearly demodulating the received modulated source signal.

45. The computer program product of claim 38, wherein the linear demodulation is a singular value decomposition.

46. The computer program product of claim 39, further comprising program code for a blind source separation process to isolate one of multiple subjects.