METHOD AND APPARATUS FOR DOPPLER RADAR SIGNAL RECOVERY OF TARGET DISPLACEMENT

• US 20150241555A1
• Filed: 02/25/2015
• Published: 08/27/2015
• Est. Priority Date: 02/25/2014
• 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, Kao, Te-Yu
• Granted Patent: US 10,401,477 B2
• Time in Patent Office: 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01S 13/50 Systems of measurement based on relative movement of target
• CPC Class Codes: G01S 7/41 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

Method and apparatus for detecting a movement, such as two or more periodic vibrations, of a target, by sending a radar signal, e.g., near 60 GHz, at the target and processing the signal reflected by the target. One or more components of the movement can have a predominant frequency, such as a frequency of vibration, and two or more components can have different frequencies and, optionally, different magnitudes. A quadrature receiver processes the received signal to produce a base band output signal having in-phase (I) and quadrature-phase (Q) outputs. The in-phase (I) and quadrature-phase (Q) outputs are cross-referenced and real target movement frequency recovered directly in the time domain. System nonlinearity, which does not occur simultaneously on the I and Q channels, is identified and removed. Radar signals having wavelengths near one or more of the target movement magnitudes can be used.

Claims

1. A method of determining a vibration rate of a target, comprising:

transmitting a transmit signal from a transmitting antenna at a target such that the transmit signal is reflected by the target to create a reflected signal,

wherein the transmit signal and the reflected signal are electromagnetic signals having a wavelength, λ

,

where the transmit signal is represented as T(t)=cos(2π

ft+φ

_vco),

wherein the target is vibrating at a first vibration having a first frequency, f_r, and a first amplitude, m_r, wherein the target is vibrating with a second vibration having a second frequency, f_h, and a second amplitude, m_h;

receiving the reflected signal via a receiving antenna to create a receive signal;

demodulating the receive signal to produce a baseband output B(t), where

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

applying a Fourier transform to the recovered B_I(t) or the recovered B_Q(t) to produce a frequency spectrum of the recovered B_I(t) or a frequency spectrum of the recovered B_Q(t), respectively; and

determining f_h from the frequency spectrum of the recovered B_I(t) or the frequency spectrum of the recovered B_Q(t).

3. The method according to claim 1, wherein identifying distorted portions of B_I(t) or distorted portions of B_Q(t) comprises:

identifying peaks in B_I(t) or peaks in B_Q(t), where a peak is a location in B_I(t) or a location in B_Q(t) where a slope of B_I(t) or a slope of B_Q(t) changes sign from positive to negative or from negative to positive, respectively; and

identifying whether each peak of the peaks in B_I(t) or the peaks in B_Q(t) is a type I peak, where a type I peak is a peak in B_I(t) that occurs when the sign of the slope of B_Q(t) remains unchanged or a peak in B_Q(t) that occurs when the sing of the slope of B_I(t) remains unchanged,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) starts when B_I(t) or B_Q(t) is not in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) ends when B_I(t) or B_Q(t) is in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively.

4. The method according to claim 3, wherein producing recovered portions of B_I(t) or recovered portions of B_Q(t) comprises:

flipping a direction of a magnitude change of a value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) as compared with a preceding value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) such that a value of the recovered portions of B_I(t) or the recovered portions of B_Q(t) is a preceding value of the recovered portions of B_I(t) or the recovered portions of B_Q(t) added together with a change in magnitude equal to the magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t) and having an opposite direction of magnitude change as the direction of magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t), respectively.

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

applying a Fourier transform to a portion of B_I(t) or a portion of B_Q(t) that is not within a distorted portion of B_I(t) or a distorted portion of B_Q(t), respectively to produce a second frequency spectrum of B_I(t) or a second frequency spectrum of B_Q(t); and

determining f_n from the second frequency spectrum of B_I(t) or the second frequency spectrum of B_Q(t), respectively.

6. The method according to claim 2, wherein the target is an animal and x(t) is a chest-wall movement of the animal.

7. The method according to claim 6, wherein the animal is a human.

8. The method according to claim 7, wherein f_r is a respiration rate of the human.

9. The method according to claim 6, wherein m_r and f_r are a magnitude of respiration and a frequency of respiration, respectively, and m_h and f_h are a magnitude of heartbeat and frequency of heartbeat, respectively.

10. The method according to claim 1, wherein m_r is at least (0.9)λ

.

11. The method according to claim 1, wherein m_r is at least λ

.

12. The method according to claim 1, wherein m_r is greater than λ

.

13. The method according to claim 1,

wherein a frequency of the transmit signal is at least 55 GHz.

14. The method according to claim 7,

wherein m_h<

(0.1) m_r.

15. An apparatus, comprising:

a transmitter, wherein the transmitter is configured to transmit a signal from a transmitting antenna at a target such that the transmit signal is reflected by the target to create a reflected signal,

wherein the transmit signal and the reflected signal are electromagnetic signals having a wavelength, λ

,

where the transmit signal is represented as T(t)=cos(2π

ft+φ

_vco),

wherein the target is vibrating at a first vibration having a first frequency, f_r, and a first amplitude, m_r, wherein the target is vibrating with a second vibration having a second frequency, f_h, and a second amplitude, m_h;

a receiver, wherein the receiver is configured to receive the reflected signal via a receiving antenna to create a receive signal;

a processor, wherein the processor is configured to;

demodulate the receive signal to produce a baseband output B(t), where

16. The apparatus according to claim 15, wherein the processor is further configured to:

apply a Fourier transform to the recovered B_I(t) or the recovered B_Q(t) to produce a frequency spectrum of the recovered B_I(t) or a frequency spectrum of the recovered B_Q(t), respectively; and

determine f_h from the frequency spectrum of the recovered B_I(t) or the frequency spectrum of the recovered B_Q(t),

wherein the processor is configured to identify distorted portions of B_I(t) or distorted portions of B_Q(t) via the processor;

identifying peaks in B_I(t) or peaks in B_Q(t) where a peak is a location on B_I(t) or B_Q(t) where a slope of B_I(t) or a slope of B_Q(t) changes sign from positive to negative or from negative to positive; and

identifying whether each peak of the peaks in B_I(t) or the peaks in B_Q(t) is a type I peak, where a type I peak is a peak in B_I(t) that occurs when the sign of the slope of B_Q(t) remains unchanged or a peak in B_Q(t) that occurs when the sing of the slope of B_I(t) remains unchanged,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) starts when B_I(t) or B_Q(t) is not in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) ends when B_I(t) or B_Q(t) is in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively,

wherein the processor is configured to produce recovered portions of B_I(t) or recovered portions of B_Q(t) via the processor flipping a direction of a magnitude change of a value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) as compared with a preceding value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) such that a value of the recovered portions of B_I(t) or the recovered portions of B_Q(t) is a preceding value the recovered portions of B_I(t) or the recovered portions of B_Q(t) added together with a change in magnitude equal to the magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t) having an opposite direction of change in value as the direction of the magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t), respectively.

17. The apparatus according to claim 15, wherein the processor is further configured to:

apply a Fourier transform to a portion of B_I(t) or a portion of B_Q(t) that is not within a distorted portion of B_I(t) or a distorted portion of B_Q(t) to produce a second frequency spectrum of B_I(t) or a second frequency spectrum of B_Q(t); and

determine f_n from the second frequency spectrum of B_I(t) or the second frequency spectrum of B_Q(t), respectively.

18. A non-transitory computer readable medium containing a set of instructions that when executed cause a computer to perform a method, wherein the method comprises:

transmitting a transmit signal from a transmitting antenna at a target such that the transmit signal is reflected by the target to create a reflected signal,

wherein the transmit signal and the reflected signal are electromagnetic signals having a wavelength, λ

,

where the transmit signal is represented as T(t)=cos(2π

ft+φ

_vco),

wherein the target is vibrating at a first vibration having a first frequency, f_r, and a first amplitude, m_r, wherein the target is vibrating with a second vibration having a second frequency, f_h, and a second amplitude, m_h;

receiving the reflected signal via a receiving antenna to create a receive signal;

demodulating the receive signal to produce a baseband output B(t), where

19. The medium according to claim 18, wherein the medium further comprises:

applying a Fourier transform to the recovered B_I(t) or the recovered B_Q(t) to produce a frequency spectrum of the recovered B_I(t) or a frequency spectrum of the recovered B_Q(t), respectively; and

determining f_h from the frequency spectrum of the recovered B_I(t) or the frequency spectrum of the recovered B_Q(t),

wherein identifying distorted portions of B_I(t) or distorted portions of B_Q(t) comprises;

identifying peaks in B_I(t) or peaks in B_Q(t) where a peak is a location on B_I(t) or B_Q(t) where a slope of B_I(t) or a slope of B_Q(t) changes sign from positive to negative or from negative to positive; and

identifying whether each peak of the peaks in B_I(t) or the peaks in B_Q(t) is a type I peak, where a type I peak is a peak in B_I(t) that occurs when the sign of the slope of B_Q(t) remains unchanged or a peak in B_Q(t) that occurs when the sing of the slope of B_I(t) remains unchanged,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) starts when B_I(t) or B_Q(t) is not in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively,

wherein a distorted portion of B_I(t) or a distorted portion of B_Q(t) ends when B_I(t) or B_Q(t) is in a distorted portion of B_I(t) or a distorted portion of B_Q(t) and a type I peak is identified in B_I(t) or B_Q(t), respectively,

wherein producing recovered portions of B_I(t) or recovered portions of B_Q(t) comprises flipping a direction of a magnitude change of a value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) as compared with a preceding value of the distorted portions of B_I(t) or the distorted portions of B_Q(t) such that a value of the recovered portions of B_I(t) or the recovered portions of B_Q(t) is a preceding value the recovered portions of B_I(t) or the recovered portions of B_Q(t) added together with a change in magnitude equal to the magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t) having an opposite direction of change in value as the direction of the magnitude change in the distorted portions of B_I(t) or the distorted portions of B_Q(t), respectively.

20. The medium according to claim 18, wherein the method further comprises:

applying a Fourier transform to a portion of B_I(t) or a portion of B_Q(t) that is not within a distorted portion of B_I(t) or a distorted portion of B_Q(t) to produce a second frequency spectrum of B_I(t) or a second frequency spectrum of B_Q(t); and

determining f_n from the second frequency spectrum of B_I(t) or the second frequency spectrum of B_Q(t), respectively.