Multi-Carrier Noncontact Signal Detection with Noise Suppression Based on a Phase-Locked Loop

Abstract

A non-contact signal detection system for detecting movement associated with a subject. A carrier source is configured to generate a first carrier signal in phase coherence with a second carrier signal. A phase-locked loop includes noise pre-cancellation system for suppressing the noise associated with a beat signal and a controlled oscillation system. The noise pre-cancellation system can be configured to phase-lock the beat signal to a first reference signal in order to stabilize the phase of the beat signal and pre-cancel the noise associated with the beat signal. The controlled oscillation system can include a propagation pathway on which a transmission signal is phase-modulated with a vibratory signal of the subject. Once acquired, the vibratory signal can have suppressed noise.

What is claimed is: 
     
         1 . A method for non-contact signal detection comprising:
 generating a noise pre-cancelled signal;   frequency-modulating a first carrier signal and a second carrier signal with the noise pre-cancelled signal to generate frequency-modulated first and second carrier signals;   transmitting, to a subject through a propagation pathway, a transmission signal comprising the frequency-modulated first and second carrier signals; and   receiving, from the propagation pathway, the transmission signal, wherein the transmission signal is phase-modulated with a vibratory signal associated with the subject.   
     
     
         2 . The method of  claim 1  further comprising generating the first carrier signal and the second carrier signal;
 wherein the first carrier signal and the second carrier signal are phased-locked with a second reference signal. 
 
     
     
         3 . The method of  claim 1  further comprising:
 receiving, by a noise precancellation system, a beat signal extracted from the phase-modulated transmission signal; and 
 suppressing a phase noise and a path noise of the beat signal by phase-locking the beat signal to a first reference signal to generate the noise pre-cancelled signal. 
 
     
     
         4 . The method of  claim 1  further comprising extracting, from the phase-modulated transmission signal, information associated with the vibratory signal of the subject, and a beat signal. 
     
     
         5 . A method for detecting movement associated with a subject, the method comprising:
 generating, by a carrier source, a first carrier signal in phase coherence with a second carrier signal;   using a noise pre-cancellation system, i) suppressing a phase noise and a path noise of a beat signal by phase-locking the beat signal to a first reference signal to stabilize the phase of the beat signal, and ii) transmitting the noise pre-cancelled signal;   using a modulator in communication with the noise pre-cancellation system and the carrier source, i) frequency-modulating the first carrier signal and the second carrier signal with the noise pre-cancelled signal and ii) transmitting a transmission signal;   transmitting, to the subject through a propagation pathway, the transmission signal;   receiving, through the propagation pathway and from the subject, a reflected signal including the transmission signal phase-modulated with a vibratory signal associated with movement of the subject; and   using a demodulator in communication with the carrier source and the noise pre-cancellation system, i) receiving the reflected signal and the second carrier signal, and ii) transmitting the beat signal to the noise pre-cancellation system.   
     
     
         6 . The method of  claim 5 , wherein the generating, by the carrier source, the first carrier signal in phase coherence with the second carrier signal comprises phase-locking the first carrier signal and the second carrier signal with a second reference signal. 
     
     
         7 . The method of  claim 5 , wherein the first reference signal is generated by a low noise reference oscillator. 
     
     
         8 . The method of  claim 5 , wherein the suppressing the phase noise and the path noise of the beat signal by phase-locking the beat signal to a first reference signal comprises:
 using a phase frequency detector, i) receiving the beat signal and the first reference signal; and ii) transmitting a phase control signal; and   using a voltage controlled oscillator, i) receiving the phase control signal; and ii) pre-cancelling the noise associated with the beat signal.   
     
     
         9 . The method of  claim 5 , wherein when the transmission signal is transmitted over the propagation pathway, the first carrier signal and the second carrier signal are phase-modulated with the vibratory signal associated with movement of the subject. 
     
     
         10 . The method of  claim 5  further comprising providing auxiliary feedback to the demodulator by transmitting the transmission signal to a third branch, the third branch in communication with and between the modulator and the demodulator. 
     
     
         11 . The method of  claim 5  further comprising extracting, from the reflected signal, i) information associated with the vibratory signal of the subject, and ii) the beat signal. 
     
     
         12 . The method of  claim 5 , wherein the vibratory signal is associated with a vital sign of the subject. 
     
     
         13 . The method of  claim 5 , wherein the first reference signal is generated by a low noise reference oscillator. 
     
     
         14 . The method of  claim 6 , wherein the second reference signal is generated by a reference oscillator. 
     
     
         15 . The method of  claim 8  further comprising a low-pass filter. 
     
     
         16 . The method of  claim 11 , wherein the extracting, from the reflected signal, is performed by the demodulator. 
     
     
         17 . A non-contact signal detection system comprising:
 an oscillation system configured to receive a first carrier signal and a second carrier signal and wirelessly transmit the first and second carrier signals to a subject generating a vibratory signal; and   a receiver configured to receive modified first and second carrier signals from the oscillation system;   wherein the modified first carrier signal comprises the first carrier signal phase-modulated with the vibratory signal of the subject.   
     
     
         18 . The non-contact signal detection system of  claim 17  further comprising a carrier source configured to generate the first and second carrier signals;
 wherein the carrier source is phase-locked to a first reference signal to establish phase coherence between the first carrier signal and the second carrier signal.