COMPENSATION AND CALIBRATION FOR A LOW POWER BIO-IMPEDANCE MEASUREMENT DEVICE

• US 20180172793A1
• Filed: 12/15/2016
• Published: 06/21/2018
• Est. Priority Date: 12/15/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: PASSONI, Marco, CAGIDIACO, Alessia, ROSSI, Stefano
• Granted Patent: US 10,401,465 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/6804 Garments; Clothes
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• 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 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence
• 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: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A method and apparatus for compensating and calibrating a bio-impedance measurement device are provided. In the method and apparatus, a memory stores a plurality of compensation parameters and a first detection channel receives a first detection signal, compensates the first detection signal using a first compensation parameter of the plurality of compensation parameters. In the method and apparatus, a second detection channel receives a second detection signal and a third detection signal and compensates the second and third detection signals using second and third compensation parameters of the plurality of compensation parameters and the compensated first detection signal. The impedance measurement device generates a first output signal representative of a first impedance measurement and a second output signal representative of a second impedance measurement based on the compensated first, second and third detection signals.

Claims

1. An impedance measurement device, comprising:

memory configured to store a plurality of compensation parameters;

a first detection channel configured to;

receive a first detection signal; and

compensate the first detection signal using a first compensation parameter of the plurality of compensation parameters; and

a second detection channel configured to;

receive a second detection signal and a third detection signal; and

compensate the second and third detection signals using second and third compensation parameters of the plurality of compensation parameters and the compensated first detection signal;

wherein the impedance measurement device generates a first output signal representative of a first impedance measurement and a second output signal representative of a second impedance measurement based on the compensated first, second and third detection signals.

2. The impedance measurement device of claim 1, wherein the first and second detection channels are configured to compensate for a relative time quantization error introduced in a trigger signal used for sampling the first detection signal and the second and third detection signals.

3. The impedance measurement device of claim 1, wherein compensating the first detection signal using the first compensation parameter includes scaling an amplitude and adjusting a phase of the first detection signal by the first compensation parameter, wherein the first compensation parameter is a complex value.

4. The impedance measurement device of claim 1, wherein generating the first output signal includes:

demodulating the compensated first detection signal to produce a first demodulated signal;

filtering the first demodulated signal; and

compensating the filtered first demodulated signal to produce the first output signal.

5. The impedance measurement device of claim 1, wherein compensating the second and the third detection signals using the second and the third compensation parameters includes:

determining a difference between the second and the third detection signals;

compensating the difference between the second and the third detection signals by the second compensation parameter;

determining a common mode voltage based on the compensated difference between the second and the third detection signals and the compensated first detection signal;

compensating the common mode voltage by the third compensation parameter; and

reducing the scaled difference between the second and the third detection signals by the scaled common mode voltage.

6. The impedance measurement device of claim 5, wherein generating the second output signal includes:

demodulating the second and third detection signals;

amplifying the difference between the second and the third detection signals to produce an amplified signal;

filtering the amplified signal; and

compensating the filtered amplified signal to produce the second output signal.

7. The impedance measurement device of claim 1, wherein the first detection channel includes a first demodulator and the first compensation parameter compensates for a gain of the first demodulator and an absolute time quantization error of the first demodulator.

8. The impedance measurement device of claim 1, wherein the second detection channel includes a second demodulator, a third demodulator and an amplifier and the second compensation parameter compensates for a gain of the second demodulator or the third demodulator and an absolute time quantization error of the second demodulator or the third demodulator and a gain of the amplifier.

9. The impedance measurement device of claim 8, wherein the second detection channel is configured to use the third compensation parameter to compensate for a common mode rejection ratio of the second demodulator and the third demodulator.

10-13. -13. (canceled)

14. A method of measuring impedance, the method comprising:

using a first detection channel, receiving a first detection signal;

using the first detection channel, compensating the first detection signal using a first compensation parameter of the plurality of compensation parameters;

using a second detection channel, receiving a second detection signal and a third detection signal; and

using the second detection channel, compensating the second and third detection signals using second and third compensation parameters of the plurality of compensation parameters and the compensated first detection signal; and

generating a first output signal representative of a first impedance measurement and a second output signal representative of a second impedance measurement based on the compensated first, second and third detection signals.

15. The method of claim 14, comprising:

compensating the first, second and third detection signals for a relative time quantization error introduced in a trigger signal used for sampling the first detection signal and the second and third detection signals.

16. The method of claim 14, wherein compensating the first detection signal using the first compensation parameter includes scaling an amplitude and adjusting a phase of the first detection signal by the first compensation parameter, wherein the first compensation parameter is a complex value.

17. The method of claim 14, wherein generating the first output signal includes:

demodulating the first detection signal to produce a first demodulated signal;

filtering the first demodulated signal; and

compensating the filtered first demodulated signal to produce the first output signal.

18. The method of claim 14, wherein compensating the second and the third detection signals using the second and the third compensation parameters includes:

determining a difference between the second and the third detection signals;

compensating the difference between the second and the third detection signals by the second compensation parameter;

determining a common mode voltage based on the compensated difference between the second and the third detection signals and the compensated first detection signal;

compensating the common mode voltage by the third compensation parameter; and

reducing the scaled difference between the second and the third detection signals by the scaled common mode voltage.

19. The method of claim 18, wherein generating the second output signal includes:

demodulating the second and third detection signals;

amplifying the difference between the second and the third detection signals to produce an amplified signal;

filtering the amplified signal; and

compensating the filtered amplified signal to produce the second output signal.

20. The method of claim 14, wherein the first detection channel includes a first demodulator and the first compensation parameter compensates for a gain of the first demodulator and an absolute time quantization error of the first demodulator.

21. An impedance measurement device, comprising:

a plurality of electrodes;

a current generator configured to supply current to the plurality of electrodes;

memory configured to store a plurality of compensation parameters; and

a voltage detector, the voltage detector including a first detection channel and a second detection channel, wherein the first detection channel is configured to receive a first detection signal and compensate the first detection signal using a first compensation parameter of the plurality of compensation parameters, wherein the second detection channel configured to receive second and third detection signals and compensate the second and third detection signals using second and third compensation parameters of the plurality of compensation parameters and the compensated first detection signal,

wherein the impedance measurement device generates a first output signal representative of a first impedance measurement and a second output signal representative of a second impedance measurement based on the compensated first, second and third detection signals.

22. The impedance measurement device of claim 21, wherein the impedance measurement device is part of a watch, activity tracker, chest band or patch.

23. The impedance measurement device of claim 21, wherein the first and second detection channels are configured to compensate for a relative time quantization error introduced in a trigger signal used for sampling the first detection signal and the second and third detection signals.

24. The impedance measurement device of claim 21, wherein compensating the first detection signal using the first compensation parameter includes scaling an amplitude and adjusting a phase of the first detection signal by the first compensation parameter, wherein the first compensation parameter is a complex value.