Random body movement cancellation for non-contact vital sign detection

• US 9,477,812 B2
• Filed: 05/13/2014
• Issued: 10/25/2016
• 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:
  US14/276,300
• Publication Number:
  US 20140330540A1
• Time in Patent Office: 896 Days
• US Class Current: 1/1
• 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, comprising:

sending a first electromagnetic signal with a first frequency to a first side of a body from a first electromagnetic wave transceiver and a second electromagnetic signal with a second frequency to a second side of the body from a second electromagnetic wave transceiver, where the first frequency of wavelength λ

₁ and the second frequency of wavelength λ

₂ are close to each other so that (λ

₁≈

λ

₂≈

λ

);

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

generating a baseband output by combining a first baseband complex signal extracted from the first reflected electromagnetic signal with a second baseband complex signal extracted from the second reflected electromagnetic signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, where the first baseband complex signal and the second baseband complex signal are combined by complex signal demodulation as expressed by;

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 the respiration rate and the heart rate extracted from the periodic Doppler phase effect to a display.

4. The method of claim 1, wherein a DC offset in at least one of the first baseband complex signal and the second baseband complex signal is not calibrated out.

5. The method of claim 1, wherein the first electromagnetic wave transceiver and the second electromagnetic wave transceiver are anyone of:

5.8 GHz quadrature radar transceivers; and

24 GHz quadrature radar transceivers.

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

sending a first electromagnetic signal with a first frequency to a first side of a body from a first electromagnetic wave transceiver and a second electromagnetic signal with a second frequency to a second side of the body from a second electromagnetic wave transceiver, where the first frequency of wavelength λ

₁ and the second frequency of wavelength λ

₂ are close to each other so that (λ

₁≈

λ

₂≈

λ

);

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

generating a baseband output by combining a first baseband complex signal extracted from the first reflected electromagnetic signal with a second baseband complex signal extracted from the second reflected electromagnetic signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, where the first baseband complex signal and the second baseband complex signal are combined by arctangent demodulation as expressed by;

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

8. The method of claim 6, wherein the first electromagnetic wave transceiver and the second electromagnetic wave transceiver are anyone of:

5.8 GHz quadrature radar transceivers; and

24 GHz quadrature radar transceivers.

9. The method of claim 6, further comprising:

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

10. The method of claim 9, further comprising:

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

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

a first electromagnetic wave transceiver configured to send a first electromagnetic signal with a first frequency to a first side of a body and receive a first reflected electromagnetic signal reflected back in response to the first electromagnetic signal;

a second electromagnetic wave transceiver configured to send a second electromagnetic signal with a second frequency to a second side of the body, where the first frequency and the second frequency are different frequencies, and receive a second reflected electromagnetic signal reflected back in response to the second electromagnetic signal, where the first frequency of wavelength λ

₁, and the second frequency of wavelength λ

₂ are close to each other so that (λ

₁≈

λ

₂≈

λ

);

a processing system configured to generate a baseband output by combining a first baseband complex signal extracted from the first reflected electromagnetic signal with a second baseband complex signal extracted from the second reflected electromagnetic signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, where the first baseband complex signal and the second baseband complex signal are combined by complex signal demodulation as expressed by;

12. The system of claim 11, wherein the processing system is further configured to extract at least one of respiration rate and heart rate from the periodic Doppler phase effect.

13. The system of claim 12, further comprising:

a display that displays the at least one of the respiration rate and the heart rate extracted from the periodic Doppler phase effect.

14. The system of claim 11, wherein a DC offset in at least one of the first baseband complex signal and the second baseband complex signal is not calibrated out.

15. The system of claim 11, wherein the first electromagnetic wave transceiver and the second electromagnetic wave transceiver are anyone of:

5.8 GHz quadrature radar transceivers; and

24 GHz quadrature radar transceivers.

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

a first electromagnetic wave transceiver configured to send a first electromagnetic signal with a first frequency to a first side of a body and receive a first reflected electromagnetic signal reflected back in response to the first electromagnetic wave signal;

a second electromagnetic wave transceiver configured to send a second electromagnetic signal with a second frequency to a second side of the body, where the first frequency and the second frequency are different frequencies, and receive a second reflected electromagnetic signal reflected back in response to the second electromagnetic signal, where the first frequency of wavelength λ

₁, and the second frequency of wavelength λ

₂ are close to each other so that (λ

₁≈

λ

₂≈

λ

);

a processing system configured to generate a baseband output by combining a first baseband complex signal extracted from the first reflected electromagnetic signal with a second baseband complex signal extracted from the second reflected electromagnetic signal to cancel out a Doppler frequency drift therebetween to yield a periodic Doppler phase effect, where the first baseband complex signal and the second baseband complex signal are combined by arctangent demodulation as expressed by;

17. The system of claim 16, wherein a DC offset in the first baseband complex signal and the second baseband complex signal is calibrated out.

18. The system of claim 16, wherein the first electromagnetic wave transceiver and the second electromagnetic wave transceiver are anyone of:

5.8 GHz quadrature radar transceivers; and

24 GHz quadrature radar transceivers.

19. The system of claim 16, wherein the processing system is further configured to extract at least one of respiration rate and heart rate from the periodic Doppler phase effect.

20. The system of claim 19, further comprising:

a display that displays the at least one of the respiration rate and the heart rate extracted from the periodic Doppler phase effect.