# US 11,026,633 B2 · Method for detecting motion artifact using wavelet transform

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- Number: US 11,026,633 B2
- Document ID: US11026633B2
- Status: Granted
- Kind: B2
- Application number: 15/741,493
- Filed: 2015-12-30
- Published: 2018-09-20
- Granted: 2021-06-08
- Earliest claimed: 2015-07-03
- Assignees: University of Ulsan Foundation for Industry Cooperation
- Applicants: University of Ulsan Foundation for Industry Cooperation
- Inventors: Sungoh Kwon; Da Hee Ban
- Web page: https://patentgrep.com/patent/US11026633B2

## CPC

- A61B 5/726: {using Wavelet transforms}
- A61B 5/02416: {using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence)}
- A61B 5/7207: {of noise induced by motion artifacts}
- A61B 5/7246: {using correlation, e.g. template matching or determination of similarity}
- A61B 5/725: {using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316)}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A motion artifact detecting method using wavelet transform which is capable of removing the problem caused by a radio noise and a motion artifact generated during the measurement of a PPG signal which is one of bio-signals, the method including: measuring a PPG signal; generating a signal obtained by removing a radio noise from the measured PPG signal; setting a reference signal from the signal from which the radio noise is removed; selecting a base signal based on the set reference signal; performing wavelet transform using the base signal; and detecting and removing a motion artifact using the wavelet-transformed value.

## Claims

### Claim 1

A motion artifact detecting method using wavelet transform, comprising:
measuring a Photoplethysmography (PPG) signal through a multichannel;
generating a signal obtained by removing a radio noise from the measured PPG signal;
setting a reference signal from the signal from which the radio noise is removed, the reference signal being set at a first period after a predetermined time elapses;
selecting a base signal based on the set reference signal and a plurality of base functions which can be wavelet-transformed;
performing wavelet transform using the base signal; and
detecting and removing a motion artifact using the wavelet-transformed value,
the detecting a motion artifact further comprising,
detecting a signal period when a heartbeat is activated;
determining whether the signal period is shorter than a criterion period preset based on a change of peak to peak interval (PPI);
if the signal period is shorter than the criterion period, determining that the motion artifact is included; and
if the signal period is not shorter than the criterion period, determining that the motion artifact is included when a value obtained by adding powers for respective periods of a predetermined frequency band is a predetermined multiple or higher of a power of the reference signal.

### Claim 2 (depends on 1)

The motion artifact detecting method of claim 1, wherein in the generating of a signal from which the radio noise is removed, a low pass filter is used.

### Claim 3 (depends on 1)

The motion artifact detecting method of claim 1, wherein during the selecting of a base signal, maximum values of a cross-correlation technique are compared by applying the cross-correlation technique to the plurality of base functions and the reference signal to select the largest value as a base signal.

### Claim 4 (depends on 1)

The motion artifact detecting method of claim 1, wherein during the performing of wavelet transform using a base signal, the wavelet transform is repeated such that the frequency of a low frequency band has a frequency band of 0 to 4 Hz.

### Claim 5 (depends on 1)

The motion artifact detecting method of claim 1, further comprising:
after the setting of a reference signal, correcting a difference between multiplexed signals by applying the cross-correlation technique to remove the motion artifact from the multichannel PPG signal based on the reference signal.

### Claim 6 (depends on 5)

The motion artifact detecting method of claim 5, wherein during the correcting the difference between signals, at least one of a time difference and a magnitude of the PPG signal measured through the multichannel is corrected.