Baseline drift canceling method and device

• US 8,568,329 B2
• Filed: 06/12/2009
• Issued: 10/29/2013
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Lee, Shiow-Harn, Chou, Wen-Yang
• Primary Examiner(s): PATTON, AMANDA K
• Application Number:
  US12/484,092
• Publication Number:
  US 20100168595A1
• Time in Patent Office: 1,600 Days
• Field of Search: 600508-509
• US Class Current: 600/508
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• 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

Abstract

An embodiment of a baseline drift canceling method is provided. The method removes a baseline drift signal from a bioelectric signal, and includes the steps as follows: delaying the bioelectric signal by an analog time delay circuit to generate a first bioelectric signal; according to the bioelectric signal to generate a baseline drift signal; and acquiring a second bioelectric signal according to the first bioelectric signal and the baseline drift signal.

Claims

1. A baseline drift canceling method to remove a baseline drift signal in a bioelectric signal, comprising:

delaying the bioelectric signal by an analog time delay circuit to generate a first bioelectric signal;

generating a baseline drift signal according to the bioelectric signal, wherein the baseline drift signal is generated by a low pass filter; and

acquiring a second bioelectric signal according to the first bioelectric signal and the baseline drift signal.

2. The method as claimed in claim 1, wherein the second bioelectric signal is acquired by subtracting the baseline drift signal from the first bioelectric signal.

3. The method as claimed in claim 1, wherein a delay time of the analog time delay circuit is determined according to a processing time of the low pass filter.

4. The method as claimed in claim 1, further comprising:

generating a heartbeat pulse signal according to the second bioelectric signal.

5. The method as claimed in claim 1, further comprising:

receiving a sensing signal by an analog amplifier;

amplifying the sensing signal by the analog amplifier to generate the bioelectric signal; and

transmitting the amplified bioelectric signal directly to the low pass filter.

6. A baseline drift canceling device to remove a baseline drift signal in a bioelectric signal, comprising:

a first amplifier to receive and amplify a sensing signal to generate the bioelectric signal;

a baseline drift canceling unit, comprising;

a low pass filter receiving the bioelectric signal directly from the first amplifier to generate the baseline drift signal;

an analog time delay circuit to delay the bioelectric signal to generate a first bioelectric signal; and

an adder receiving the baseline drift signal and the first bioelectric signal to generate a second bioelectric signal; and

a digital amplifier receiving and amplifying the second bioelectric signal to generate a digital bioelectric signal.

7. The device as claimed in claim 6, wherein the 3 dB frequency of the low pass filter is between 0.5 Hz and 1 Hz.

8. The device as claimed in claim 6, wherein a time constant corresponding to the 3 dB frequency of the low pass filter is between 2 seconds and 1 second.

9. The device as claimed in claim 6, wherein a time constant of the analog time delay circuit corresponding to the 3 dB frequency of the low pass filter is between 90 milliseconds and 50 milliseconds.

10. The device as claimed in claim 6, wherein a compensation gain of the low pass filter and the adder corresponding to the 3 dB frequency of the low pass filter is between 1.25 and 1.05.

11. The device as claimed in claim 6, wherein the digital amplifier comprises:

a second amplifier amplifying the second bioelectric signal; and

an analog to digital converter converting the second bioelectric signal into the digital bioelectric signal.

12. A bioelectric signal sensing apparatus, comprising:

a first sensor outputting a first sensing signal;

a second sensor outputting a second sensing signal;

a first amplifier receiving the first sensing signal and the second sensing signal to generate a bioelectric signal; and

at least one baseline drift canceling unit, comprising;

a low pass filter receiving the bioelectric signal directly from the first amplifier to generate a baseline drift signal;

an analog time delay circuit to delay the bioelectric signal to generate a first bioelectric signal; and

an adder receiving the baseline drift signal and the first bioelectric signal to generate a second bioelectric signal.

13. The apparatus as claimed in claim 12, further comprising a notch filter to filter the second bioelectric signal to eliminate an alternating current frequency interference in the second bioelectric signal.

14. The apparatus as claimed in claim 12, wherein the digital amplifier comprises:

a second amplifier amplifying the second bioelectric signal; and

an analog to digital converter converting the second bioelectric signal into the digital bioelectric signal.

15. The apparatus as claimed in claim 12, further comprising an inverting amplifier to reduce a common mode voltage.

16. The apparatus as claimed in claim 12, further comprising an R wave detector receiving the second bioelectric signal to generate a heartbeat pulse signal.

17. The apparatus as claimed in claim 12, wherein the bioelectric signal is an electrocardiography signal, an electroencephalogram signal, an electromyogram signal or an electric ocular graph signal.

18. The device as claimed in claim 12, wherein the 3 dB frequency of the low pass filter is between 0.5 Hz and 1 Hz.

19. The apparatus as claimed in claim 12, wherein a time constant corresponding to the 3 dB frequency of the low pass filter is between 2 seconds and 1 second.

20. The apparatus as claimed in claim 12, wherein a time constant of the analog time delay circuit corresponding to the 3 dB frequency of the low pass filter is between 90 milliseconds and 50 millisecond.

21. The apparatus as claimed in claim 12, wherein a compensation gain of the low pass filter and the adder corresponding to the 3 dB frequency of the low pass filter is between 1.25 and 1.05.