IMPEDANCE SENSING

• US 20170007186A1
• Filed: 07/09/2015
• Published: 01/12/2017
• Est. Priority Date: 07/09/2015
• Status: Active Grant

• Current Assignee: Philips Healthcare Informatics Incorporated (Koninklijke Philips N.V.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Lemersal, Donald Bernard, Baek, David Boettcher, Lading, Lars
• Granted Patent: US 11,471,109 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0214 of power generation or supply
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/6825 Hand
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence

Abstract

This disclosure provides systems, methods and apparatus for performing signal processing in impedance sensing applications, and more specifically, for recovering data from an amplitude-modulated signal. In one aspect, a device includes a sensing circuit operable to sense an amplitude-modulated signal having a carrier frequency. The device also includes a mixer operable to mix the amplitude-modulated signal with a mixing signal having a mixing frequency to provide a frequency-downshifted signal having an intermediate frequency less than the carrier frequency. The device also includes a filter operable to filter the frequency-downshifted signal to provide a filtered signal. The device further includes a sampler operable to undersample the filtered signal at an undersampling frequency to provide a digital signal, the digital signal being representative of a modulating signal.

Claims

1. A device capable of recovering data from an amplitude-modulated signal comprising:

a sensing circuit operable to sense an amplitude-modulated signal having a carrier frequency;

a mixer operable to mix the amplitude-modulated signal with a mixing signal having a mixing frequency to provide a frequency-downshifted signal having an intermediate frequency less than the carrier frequency;

a filter operable to filter the frequency-downshifted signal to provide a filtered signal; and

a sampler operable to undersample the filtered signal at an undersampling frequency to provide a digital signal, the digital signal being representative of a modulating signal.

2. The device of claim 1, wherein the amplitude-modulated signal is phase-modulated relative to the modulating signal.

3. The device of claim 1, further including at least one first electrode operable to receive the amplitude-modulated signal and to pass the amplitude-modulated signal to the sensing circuit, the at least one first electrode being adapted to couple with a biological object.

4. The device of claim 3, further including:

at least one second electrode adapted to couple with the biological object; and

an excitation signal generator operable to generate an excitation signal at the carrier frequency, the at least one second electrode being adapted to provide the excitation signal to the biological object, the amplitude-modulated signal being representative of a response of the biological object to the excitation signal.

5. The device of claim 4, wherein the modulating signal is representative of an impedance of the biological object.

6. The device of claim 5, wherein the carrier frequency is greater than or equal to approximately 1 MHz.

7. The device of claim 5, wherein:

the excitation signal includes an electrical current signal; and

the amplitude-modulated signal includes an electrical voltage signal representative of a voltage response of the biological object to the excitation signal based on the impedance.

8. The device of claim 5, wherein:

the excitation signal includes an electrical voltage signal; and

the amplitude-modulated signal includes an electrical current signal representative of a current response of the biological object to the excitation signal based on the impedance.

9. The device of claim 1, further including:

a power source;

a wearable housing that at least partially encompasses the sensing circuit, the mixer, the filter, the sampler, and the power source; and

a coupling mechanism adapted to couple the wearable housing to a user.

10. The device of claim 1, wherein the undersampling frequency is greater than twice a bandwidth of the filtered signal.

11. The device of claim 1, further including a controller and wherein:

the filter includes a bandpass filter having a fixed passband; and

the controller sets the mixing frequency of the mixing signal to provide the frequency-downshifted signal with the intermediate frequency substantially equal to a center frequency of the fixed passband of the bandpass filter.

12. The device of claim 11, wherein the filter includes a passive filter.

13. The device of claim 11, wherein the controller is operable to set the carrier frequency.

14. The device of claim 1, wherein the intermediate frequency is greater than a frequency of the modulating signal.

15. The device of claim 1, wherein the mixer includes a switching device, and wherein the switching device includes a single pole, single throw (SPST) switch or a single pole, double throw (SPDT) switch.

16. The device of claim 1, wherein the mixing signal is a square wave signal.

17. A device capable of recovering data from an amplitude-modulated signal comprising:

means for sensing an amplitude-modulated signal having a carrier frequency;

means for mixing the amplitude-modulated signal with a mixing signal having a mixing frequency to provide a frequency-downshifted signal having an intermediate frequency less than the carrier frequency;

means for filtering the frequency-downshifted signal to provide a filtered signal; and

means for undersampling the filtered signal at an undersampling frequency to provide a digital signal, the digital signal being representative of a modulating signal.

18. The device of claim 17, further including at least one first electrode operable to receive the amplitude-modulated signal and to pass the amplitude-modulated signal to the means for sensing, the at least one first electrode being adapted to couple with a biological object.

19. The device of claim 18, further including:

at least one second electrode adapted to couple with the biological object; and

means for generating an excitation signal at the carrier frequency, the at least one second electrode being adapted to provide the excitation signal to the biological object, the amplitude-modulated signal being representative of a response of the biological object to the excitation signal.

20. The device of claim 19, wherein the modulating signal is representative of an impedance of the biological object.

21. The device of claim 20, wherein the carrier frequency is greater than or equal to approximately 1 MHz.

22. The device of claim 20, wherein:

the excitation signal includes an electrical current signal; and

the amplitude-modulated signal includes an electrical voltage signal representative of a voltage response of the biological object to the excitation signal based on the impedance.

23. A method for recovering data from an amplitude-modulated signal comprising:

sensing an amplitude-modulated signal having a carrier frequency;

mixing the amplitude-modulated signal with a mixing signal having a mixing frequency to provide a frequency-downshifted signal having an intermediate frequency less than the carrier frequency;

filtering the frequency-downshifted signal to provide a filtered signal; and

undersampling the filtered signal at an undersampling frequency to provide a digital signal, the digital signal being representative of a modulating signal.

24. The method of claim 23, further including:

generating an excitation signal at the carrier frequency; and

providing the excitation signal to a biological object, the amplitude-modulated signal being representative of a response of the biological object to the excitation signal.

25. The method of claim 24, wherein the modulating signal is representative of an impedance of the biological object.

26. The method of claim 25, wherein the carrier frequency is greater than or equal to approximately 1 MHz.

27. The method of claim 25, wherein:

the excitation signal includes an electrical current signal; and

the amplitude-modulated signal includes an electrical voltage signal representative of a voltage response of the biological object to the excitation signal based on the impedance.