System and Methods for Remote Sensing Using Double-Sideband Signals

• US 20080238757A1
• Filed: 03/31/2006
• Published: 10/02/2008
• Est. Priority Date: 04/22/2005
• 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: Xiao, Yanming, Lin, Jenshan
• Granted Patent: US 7,903,020 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• 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 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: G01S 13/38 wherein more than one modulation frequency is used
• CPC Class Codes: G01S 13/40 wherein the frequency of transmitted signal is adjusted to give a predetermined phase relationship
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/352 Receivers

Abstract

A sensing system (100) is provided that includes a transceiver (102). The transceiver includes a transmitter chain that transmits a double-sideband electromagnetic wave having first and second frequency components, and a receiving chain that receives the double-sideband electromagnetic wave after it is reflected by a target. The system (100) further includes a baseband circuit (104) for extracting information content from the double sideband electromagnetic wave. A separation between the first and second frequency components causes a spike in a signal response generated by one sideband of the double-sideband electromagnetic wave to substantially overlap a null point of a signal response generated by the other sideband of the double-sideband electromagnetic wave.

Claims

1. A method of remote sensing, the method comprising:

transmitting a double-sided electromagnetic wave comprising a first frequency component and a second frequency component; and

receiving the electromagnetic wave after it is reflected by a subject;

wherein a separation between the first and second frequency components causes a spike in a signal response corresponding to one side band of the double-sided electromagnetic wave to substantially overlap a null point of a signal response corresponding to the other side band of the double-sided electromagnetic wave.

2. The method of claim 1, wherein the spike comprises an optimal point.

3. The method of claim 1, further comprising determining a separation between the first and second frequency components that causes the spike to substantially overlap the null point.

4. The method of claim 1, further comprising adjusting at least one of the first and second frequency components to thereby effect a separation that causes the spike to substantially overlap the null point.

5. The method of claim 4, wherein the step of determining the separation comprises sampling a plurality of detection sensitivity measurements, each measurement corresponding to a different separation, and selecting from among the different separations a separation that yields the greatest detection sensitivity.

6. The method of claim 1, further comprising generating the double-sided electromagnetic wave by multiplying a first signal having a frequency equal to the first frequency component and a second signal having a different frequency equal to the second frequency component.

7. The method of claim 1, wherein the first and second frequency components have frequencies within a Ka-band of an electromagnetic spectrum.

8. A sensing system, comprising:

a transceiver including

a transmitter chain that transmits a double-sided electromagnetic wave having first and second frequency components, and

a receiving chain that receives the double-sided electromagnetic wave after it is reflected by a target; and

a baseband circuit for extracting information content from the double-sided electromagnetic wave;

wherein a separation between the first and second frequency components causes a spike in a signal response generated by one sideband of the double-sided electromagnetic wave to substantially overlap a null point of a signal response generated by the other sideband of the double-sided electromagnetic wave.

9. The system as in claim 8, wherein the spike is an optimum point.

10. The system as in claim 8, wherein the receiving chain is configured according to a two-step indirect conversion receiver architecture.

11. The system as in claim 8, wherein the target is a monitored patient.

12. The system as in claim 8, further comprising a frequency determining unit.

13. The system of claim 12, wherein the frequency determining unit comprises at least one of a frequency determining module, an accuracy assessment module, and a frequency control module.

14. The system of claim 8, wherein the system comprises a baby monitor.

15. The system of claim 8, wherein the system comprises an exercise monitor for monitoring an individual engaged in an exercise regime.

16. A machine-readable storage medium, the storage medium comprising machine-directing instructions for:

transmitting a double-sided electromagnetic wave comprising a first frequency component and a second frequency component; and

receiving the electromagnetic wave after it is reflected by a subject;

wherein a separation between the first and second frequency components causes a spike in a signal response corresponding to one side band of the double-sided electromagnetic wave to substantially overlap a null point of a signal response corresponding to the other side band of the double-sided electromagnetic wave.

17. The storage medium of claim 16, wherein the spike is an optimum point.

18. The storage medium of claim 16, further comprising a machine-directing instruction for adjusting at least one of the first and second frequency components to thereby effect the separation that causes the spike to substantially overlap the null point.

19. The storage medium of claim 16, further comprising a machine-directing instruction for determining the separation between the first and second frequency components that causes the spike to substantially overlap the null point.

20. The storage medium of claim 19, wherein the machine-directing instruction for determining the separation comprises an instruction for sampling a plurality detection sensitivity measurements, each measurement corresponding to a different separation, and selecting from among the different separations a separation that yields the greatest detection sensitivity.

21. The storage medium of claim 16, further comprising a machine-directing instruction for generating the double-sided electromagnetic wave by multiplying a first signal having a frequency equal to the first frequency component and a second signal having a different frequency equal to the second frequency component.

26. The system of claim 21, wherein the Ka-band transceiver comprises:

a transmitter chain;

a receiver chain; and

first and second power splitters, each power splitter being electrically connected between different points in the transmitter chain and receiver chain for splitting a power of a carrier signal between the transmitter chain and the receiver chain.

27. The system of claim 26, further comprising a voltage controlled oscillator connected to the second power splitter, and wherein the transmitter chain comprises:

a transmitting antenna through which the sensing signal is transmitted;

first and second up-converters for mixing the carrier signal with the sensing signal;

wherein the first up-converter is connected to the first power splitter, and the second up-converter is connected to the second power splitter.

28. The system of claim 26, further comprising a voltage controlled oscillator connected to the second power splitter, and wherein the receiver chain comprises:

a receiving antenna through which the modulated signal is received; and

first and second down-converters for mixing the carrier signal with the modulated signal;

wherein the first down-converter is connected to the second power splitter, and the second down-converter is connected to the first power splitter.

29. The system of claim 27, further comprising a low-noise amplifier connected between the receiving antenna and the first down-converter and an intermediate frequency amplifier connected between the first down-converter and the second down-converter.

22. A system for sensing cardiopulmonary activity, the system comprising:

Ka-band transceiver for transmitting a sensing signal to a monitored subject and receiving a modulated signal from the monitored subject, the sensing signal having a frequency within a Ka-band range of frequencies and the modulated signal being modulated based upon cardiopulmonary activity in the monitored subject; and

a baseband circuit connected to the Ka-band transceiver for generating a baseband signal output based upon the modulated signal and indicative of the cardiopulmonary activity in the monitored subject.

23. The system of claim 22, further comprising a signal processor connected to the baseband circuit for processing the baseband signal output.

24. The system of claim 23, further comprising a signal digitizer connected between the baseband circuit and the signal processor for digitizing the baseband signal output.

25. The system of claim 22, wherein the Ka-band transceiver comprises an indirect-conversion transceiver for effecting a two-step conversion of the modulated signal after it is received by the Ka-band transceiver to thereby mitigate a potential DC offset problem.

30. The system of claim 22, wherein the baseband circuit comprises a preamplifier, a bandpass filter connected to the preamplifier, and a low-frequency amplifier connected to the bandpass filter.