Random body movement cancellation for non-contact vital sign detection

• US 8,721,554 B2
• Filed: 07/11/2008
• Issued: 05/13/2014
• Est. Priority Date: 07/12/2007
• 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, Liu, Ya-Chi
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): Agahi, Puya
• Application Number:
  US12/668,700
• Publication Number:
  US 20100198083A1
• Time in Patent Office: 2,132 Days
• Field of Search: 600/481, 600/483, 600/484, 600/529, 600/407, 600/534, 340/447, 340/539.1, 340/539.12, 340/539.15, 342/28, 342/114, 342/115
• US Class Current: 600/484
• 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 5/024 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 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• 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 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/536 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/40 Means for monitoring or calibrating
• CPC Class Codes: G06F 17/14 Fourier, Walsh or analogous domain transformations , e.g. Laplace, Hilbert, Karhunen-Loeve, transforms for correlation function computation G06F17/156; spectrum analysers G01R23/16
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 80/00 ICT specially adapted for facilitating communication between medical practitioners or patients, e.g. for collaborative diagnosis, therapy or health monitoring

Abstract

A method and system for cancelling body movement effect for non-contact vital sign detection is described. The method begins with sending on a first electromagnetic wave transceiver a first electromagnetic signal with a first frequency to a first side of a body, such as a person or animal. Simultaneously using a second electromagnetic wave transceiver a second electromagnetic signal is sent with a second frequency to a second side of a body, wherein the first frequency and the second frequency are different frequencies. A first reflected electromagnetic signal reflected back in response to the first electromagnetic wave on the first transceiver is received and a first baseband complex signal is extracted. Likewise a second reflected electromagnetic signal reflected back in response to the second electromagnetic wave on the second transceiver is received and a second baseband complex signal is extracted. The first baseband complex signal is mathematically combined with the second baseband complex signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect.

Claims

1. A method for cancelling body movement effect for non-contact vital sign detection, the method comprising:

providing a first transceiver and a second transceiver;

simultaneously sending a first electromagnetic signal with a first frequency to a first side of a body from the first transceiver and a second electromagnetic signal with a second frequency to a second side of a body from the second transceiver, wherein the second side of the body is an opposite side of the body from the first side of the body;

receiving at least a first reflected signal reflected back in response to the first electromagnetic signal via the first transceiver;

extracting out a first baseband complex signal from the first reflected signal;

receiving at least a second reflected signal reflected back in response to the second electromagnetic signal via the second transceiver;

extracting out a second baseband complex signal from the second reflected signal;

providing an apparatus for combining the first baseband complex signal with the second baseband complex signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, wherein the apparatus comprises a processor and/or hardware; and

combining the first baseband complex signal with the second baseband complex signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect via the apparatus.

2. The method of claim 1, further comprising:

extracting at least one of respiration rate and heart rate from the periodic Doppler phase effect.

3. The method of claim 2, further comprising:

sending the at least one of respiration rate and heart rate from the periodic Doppler phase effect to a display.

4. The method of claim 1, wherein the first frequency, corresponding to a first wavelength, λ

₁, and the second frequency, corresponding to a second wavelength, λ

₂, are close to each other such that (λ

₁≈

λ

₂≈

λ

) and the combining the first baseband complex signal with the second baseband complex signal comprises combining the first baseband complex signal with the second baseband complex signal via complex signal demodulation expressed by

5. The method of claim 4, wherein a DC offset in at least one of the first baseband complex signal and the second baseband complex signal is not accurately calibrated.

6. The method of claim 1, wherein the first frequency, corresponding to a first wavelength, λ

₁, and the second frequency, corresponding to a second wavelength, λ

₂, are close to each other such that (λ

₁≈

λ

₂≈

λ

) and the combining the first baseband complex signal with the second baseband complex signal comprises combining the first baseband complex signal with the second baseband complex signal via arctangent demodulation expressed by

7. The method of claim 6, wherein a DC offset in the first baseband and the second baseband is accurately calibrated.

8. The method of claim 1, wherein the first transceiver and the second transceiver are selected from the group consisting of:

a 5.8 GHz quadrature radar transceiver; and

a 24 GHz quadrature radar transceiver.

9. A system for cancelling body movement effect for non-contact vital sign detection, the system comprising:

at least a first transceiver and at least a second transceiver, wherein the system is configured such that the first transceiver sends a first electromagnetic signal with a first frequency to a first side of a body and the second transceiver simultaneously sends a second electromagnetic signal with a second frequency to a second side of a body, wherein the first frequency and the second frequency are different frequencies, wherein the second side of the body is an opposite side of the body from the first side of the body,

wherein the first transceiver receives a first reflected electromagnetic signal reflected back in response to the first electromagnetic signal, and extracts out a first baseband complex signal from the first reflected signal;

wherein the second transceiver receives a second reflected electromagnetic signal reflected back in response to the second electromagnetic signal, and extracts out a second baseband complex signal from the second reflected signal;

an apparatus configured to combine the first baseband complex signal with the second baseband complex signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, wherein the apparatus comprises a processor and/or hardware.

10. The system of claim 9, further comprising:

a processor configured to extract at least one of respiration rate and heart rate from the periodic Doppler phase effect.

11. The system of claim 10, further comprising:

a display for displaying the at least one of respiration rate and heart rate from the periodic Doppler phase effect.

12. The system of claim 9, wherein the first frequency, corresponding to a first wavelength, λ

₁, and the second frequency, corresponding to a second wavelength, λ

₂, are close to each other such that (λ

₁≈

λ

₂≈

λ

) and combining the first baseband complex signal with the second baseband complex signal comprises combining the first baseband complex signal with the second baseband complex signal via complex signal demodulation expressed by

13. The system of claim 12, wherein a DC offset in at least one of the first baseband and the second baseband is accurately calibrated.

14. The system of claim 9, wherein the first frequency corresponding to a first wavelength, λ

₁, and the second frequency, corresponding to a second wavelength, λ

₂, are close to each other such that (λ

₁≈

λ

₂≈

λ

) and the combining the first baseband complex signal with the second baseband complex signal comprises combining the first baseband complex signal with the second baseband complex signal via arctangent demodulation expressed by

15. The system of claim 14, wherein a DC offset in the first baseband and the second baseband is accurately calibrated.

16. The system of claim 9, wherein the first transceiver and the second transceiver are selected from the group consisting of:

a 5.8 GHz quadrature radar transceiver; and

a 24 GHz quadrature radar transceiver.