System and method for biological signal processing with highly auto-correlated carrier sequences

• US 10,537,288 B2
• Filed: 06/08/2017
• Issued: 01/21/2020
• Est. Priority Date: 04/06/2013
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Fung, Kin C., Dick, Timothy J., Hall, Jr., Charles William
• Primary Examiner(s): Negin, Russell S
• Application Number:
  US15/617,732
• Publication Number:
  US 20170265816A1
• Time in Patent Office: 957 Days
• Field of Search: None
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
• 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: B60R 25/25 using biometry
• CPC Class Codes: G06F 2218/10 by analysing the shape of a waveform, e.g. extracting parameters relating to peaks
• CPC Class Codes: G06F 2218/12 Classification; Matching
• CPC Class Codes: G06V 40/15 Biometric patterns based on physiological signals, e.g. heartbeat, blood flow
• CPC Class Codes: G08C 17/00 Arrangements for transmitting signals characterised by the use of a wireless electrical link
• CPC Class Codes: G08C 17/02 using a radio link
• CPC Class Codes: G16H 10/60 for patient-specific data, e.g. for electronic patient records
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference

Abstract

A computer-implemented method including, transmitting a high-spectrum energy wave towards a subject from a first sensor and transmitting a low-spectrum energy wave towards the subject from a second sensor. In response, modulation with a carrier sequence code results in a modulated evoked biological signal. The carrier sequence code has an autocorrelation function. The method includes demodulating the modulated evoked biological signal by calculating a convolution of the modulated evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum. The evoked biological signal spectrum has a peak to sideband ratio as a function of the carrier sequence code. The method includes calculating deviations between each element of the sampled evoked biological signal and the peak to sideband ratio and filtering noise artifacts from the sampled evoked biological signal based on the deviations.

Claims

1. A computer-implemented method, comprising:

transmitting a high-spectrum energy wave towards a subject from a first sensor according to a first control signal;

transmitting a low-spectrum energy wave towards the subject from a second sensor according to a second control signal;

in response to transmitting the high-spectrum energy wave and transmitting the low-spectrum energy wave, receiving at a first receiver of the first sensor, an evoked biological signal from the subject and receiving at a second receiver of the second sensor, an evoked noise signal from the subject;

cancelling noise from the evoked biological signal based on the evoked noise signal;

calculating a sampled evoked biological signal by sampling the evoked biological signal at a predetermined sampling rate;

modulating the sampled evoked biological signal with a carrier sequence code resulting in a modulated evoked biological signal, the carrier sequence code having an autocorrelation function;

demodulating the modulated evoked biological signal by calculating a convolution of the modulated evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum, the evoked biological signal spectrum having a peak to sideband ratio as a function of the carrier sequence code;

calculating deviations between each element of the sampled evoked biological signal and the peak to sideband ratio;

filtering noise artifacts from the sampled evoked biological signal based on the deviations; and

outputting a true evoked biological signal based on the filtering.

2. The computer-implemented method of claim 1, wherein modulating the sampled evoked biological signal further includes converting the carrier sequence code to binary format and modulating the sampled evoked biological signal with the carrier sequence code in binary format.

3. The computer-implemented method of claim 2, wherein demodulating the modulated evoked biological signal further includes demodulating the modulated evoked biological signal by calculating the convolution of the modulated evoked biological signal with the carrier sequence code in binary format using a logical AND gate.

4. The computer-implemented method of claim 1, wherein transmitting the high-spectrum energy wave towards the subject from the first sensor according to the first control signal includes, transmitting the high-spectrum energy wave towards the subject from the first sensor as a pulsed energy wave according to the first control signal.

5. The computer-implemented method of claim 1, wherein transmitting the low-spectrum energy wave towards the subject from the second sensor according to the second control signal includes, transmitting the low-spectrum energy wave towards the subject from the second sensor as a continuous energy wave according to the second control signal.

6. The computer-implemented method of claim 1, wherein filtering noise artifacts from the sampled evoked biological signal based on the deviations further includes, comparing the deviation of each element of the sampled evoked biological to a predetermined threshold and filtering respective elements of the sampled evoked biological signal based on the comparison.

7. The computer-implemented method of claim 1, wherein cancelling noise from the evoked biological signal based on the evoked noise signal includes, filtering the evoked biological signal with the evoked noise signal using signal cancellation.

8. The computer-implemented method of claim 1, wherein the evoked biological signal spectrum represents the evoked biological signal with amplitude increased by a factor proportional to the peak to sideband ratio.

9. A computer-implemented method, comprising:

transmitting a high-spectrum energy wave towards a subject from a first sensor according to a first control signal, wherein the first control signal represents a carrier sequence code;

transmitting a low-spectrum energy wave towards the subject from a second sensor according to a second control signal;

receiving at a first receiver of the first sensor an evoked biological signal in response to energy reflection returned from the subject, wherein the evoked biological signal is an analog signal and modulated according to the carrier sequence code;

receiving at a second receiver of the second sensor an evoked noise signal in response to energy reflection returned from the subject;

cancelling noise from the evoked biological signal based on the evoked noise signal;

demodulating the evoked biological signal by calculating a convolution of the evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum, the evoked biological signal spectrum having signal-to-noise ratio proportional to a peak to sideband ratio, wherein the peak to sideband ratio is a function of the carrier sequence code; and

generating a true evoked biological signal by extracting the true evoked biological signal from the evoked biological signal based on the peak to sideband ratio.

10. The computer-implemented method of claim 9, wherein transmitting the low-spectrum energy wave towards the subject from the second sensor according to the second control signal includes, transmitting the low-spectrum energy wave towards the subject from the second sensor as a continuous energy wave according to the second control signal.

11. The computer-implemented method of claim 9, wherein the carrier sequence code has an auto correlation function.

12. The computer-implemented method of claim 9, wherein the carrier sequence code is a concatenation of two carrier sequences codes each having a different length.

13. A system, comprising:

a first sensor including a first transmitter to transmit first control signals to a first transmission source, wherein the first transmission source transmits a high-spectrum energy wave towards a subject according to the first control signals, the first sensor further including a first receiver to receive an evoked biological signal in response to energy reflection returned from the subject, wherein the evoked biological signal is an analog signal;

a second sensor, communicatively coupled to the first sensor, the second sensor including a second transmitter to transmit second control signals to a second transmission source, wherein the second transmission source transmits a low-spectrum energy wave towards the subject according to the second control signals, the second sensor further including a second receiver to receive an evoked noise signal in response to energy reflection returned from the subject;

a filter, communicatively coupled to the first sensor and the second sensor, wherein the filter cancels noise from the evoked biological signal based on the evoked noise signal;

a system clock, communicatively coupled to the first sensor, the second sensor, and the filter, to generate a sampled evoked biological signal at a predetermined sampling rate;

a modulator, communicatively coupled to the first sensor, the second sensor, and the filter, to receive the sampled evoked biological signal and modulate the sampled evoked biological signal with a carrier sequence code having an autocorrelation function; and

a demodulator, communicatively coupled to the first sensor, the second sensor, and the filter, to receive the modulated evoked biological signal and demodulate the modulated evoked biological signal by calculating a convolution of the modulated evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum, the evoked biological signal spectrum having a peak to sideband ratio as a function of the carrier sequence code;

wherein the filter calculates deviations between the sampled evoked biological signal and the peak to sideband ratio, filters noise artifacts from the sampled evoked biological signal based on the deviations, and outputs a true evoked biological signal based on the filtering.

14. The system of claim 13, wherein the high-spectrum energy wave is within a red color spectrum and the low-spectrum energy wave is within a blue color spectrum.

15. The system of claim 13, wherein the filter removes elements of the sampled evoked biological signal if the respective deviation meets a predetermined threshold outside of the peak to sideband ratio.

16. A system, comprising:

a first sensor including a first transmitter to transmit first control signals according to a carrier sequence code to a first transmission source, wherein the first transmission source transmits high-spectrum energy towards a subject according to the carrier sequence code, the carrier sequence code having an autocorrelation function,

wherein the first sensor further includes a first receiver to receive an evoked biological signal in response to energy reflection returned from the subject, wherein the evoked biological signal is an analog signal and modulated according to the carrier sequence code;

a second sensor including a second transmitter to transmit second control signals to a second transmission source, wherein the second transmission source transmits low-spectrum energy towards the subject,

wherein the second sensor further includes a second receiver to receive an evoked noise signal in response to energy reflection returned from the subject;

a filter including an amplifier for cancelling noise from the evoked biological signal based on the evoked noise signal;

a demodulator to demodulate the evoked biological signal by calculating a convolution of the evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum, the evoked biological signal spectrum having signal-to-noise ratio proportional to a peak to sideband ratio, wherein the peak to sideband ratio is a function of the carrier sequence code,

wherein the demodulator generates a true evoked biological signal by extracting the true evoked biological signal from the evoked biological signal based on the peak to sideband ratio.

17. The system of claim 16, wherein the carrier sequence code is a concatenation of two carrier sequences codes each having a different length.

18. The system of claim 16, wherein the demodulator further demodulates the evoked biological signal by calculating the convolution of the evoked biological signal with a two'"'"'s complement of the carrier sequence code in binary format using a logical XOR gate.

19. The system of claim 16, wherein the second transmission source transmits low-spectrum energy towards the subject as a continuous energy wave.

20. The system of claim 19, wherein the low-spectrum energy has a wavelength corresponding to visible blue light.