Heart rate monitor with time varying linear filtering

Patent metadata

Field	Value
Publication number	US-2017105682-A1
Application number	US-201615296956-A
Country	US
Kind code	A1
Filing date	Oct 18, 2016
Priority date	Oct 19, 2015
Publication date	Apr 20, 2017
Grant date	—

Abstract

A system, method, and device for monitoring a cardiac signal of a user includes an emitter (LED) for transmitting light toward skin of the user, a receiver (photodiode) for receiving a reflection of the transmitted light and generating a light intensity signal, and a processor configured to generate a photoplethysmogram (PPG) signal based on the light intensity signal. The PPG signal includes a cardiac component, a motion component and a respiratory component. An inertial sensor provides a motion signal to the processor based on sensed movement of the device and one or more time-variant filters are configured by the processor to filter the PPG signal to isolate the cardiac component of the PPG signal based on determined filter coefficients.

First claim

What is claimed is:

1 . A fitness monitor for monitoring a cardiac signal of a user, the device comprising:
an emitter configured to transmit light toward skin of the user; a receiver configured to receive a reflection of the transmitted light and provide a photoplethysmogram (PPG) signal based on the received reflection of the transmitted light, the PPG signal including a cardiac component and a motion component; an inertial sensor configured to provide a motion signal based on sensed movement of the fitness monitor; a time-variant filter receiving the PPG signal, and a processor coupled to the emitter, the receiver, the inertial sensor and the time-variant filter, the processor configured to:
determine one or more frequencies associated with the motion signal;
transform the PPG signal to the frequency domain;
identify, in the frequency domain, the cardiac component in the PPG signal based on the determined one or more frequencies of the motion signal and the transformed PPG signal;
determine filter coefficients based on the identified cardiac component in the PPG signal;
configure the time-variant filter with the determined filter coefficients; and
filter, in the time domain via the time-variant filter, the identified motion component from the PPG signal to isolate the cardiac component.

2 . The fitness monitor of claim 1 , wherein the time-variant filter is integrated within the processor.

3 . The fitness monitor of claim 1 , wherein the filter coefficients are determined upon each occurrence of the cardiac component being identified based on the determined one or more frequencies of the motion signal and the transformed PPG signal.

4 . The fitness monitor of claim 3 , wherein the processor configures the time-variant filter with the determined filter coefficients upon each occurrence of the cardiac component being identified.

5 . The fitness monitor of claim 1 , wherein the processor is further configured to periodically reconfigure the time-variant filter based on the cardiac component identified in the frequency domain.

6 . The fitness monitor of claim 1 , wherein the processor is further configured to pre-condition the PPG signal by attenuating frequency components of the PPG signal below the frequency band that includes the cardiac component and/or attenuates frequency components above the frequency band that includes the cardiac component.

7 . The fitness monitor of claim 1 , wherein the cardiac component is associated with heart rate.

8 . The fitness monitor of claim 1 , wherein the processor is further configured to analyze the cardiac component of the PPG signal to determine heart-rate variability, stress, recovery time, VO2 max, and/or sleep quality of the user.

9 . The fitness monitor of claim 1 , further comprising a user interface coupled to the processor to display information based on the isolated cardiac component.

10 . The fitness monitor of claim 1 , further comprising a housing to enclose the processor, the housing including a means for attaching the fitness monitor to the user.

11 . A fitness monitor for monitoring a cardiac signal of a user, the device comprising:
an emitter configured to transmit light toward skin of the user; a receiver configured to receive a reflection of the transmitted light and provide a photoplethysmogram (PPG) signal based on the received reflection of the transmitted light, the PPG signal including a cardiac component and a motion component; an inertial sensor configured to provide a motion signal based on sensed movement of the fitness monitor; a time-variant filter receiving the PPG signal, and a processor coupled to the emitter, the receiver, the inertial sensor and the time-variant filter, the processor configured to:
determine one or more frequencies associated with the motion signal and the PPG signal provided during a first period,
identify the motion component in the PPG signal for the first time period based on the determined one or more frequencies of the motion signal and the PPG signal, and
filter, via the time-variant filter, the identified motion component from the PPG signal provided during a second time period to isolate the cardiac component of the PPG signal for the second time period.

12 . The fitness monitor of claim 11 , wherein the first and second time periods correspond to the same period of time.

13 . The fitness monitor of claim 11 , wherein the time-variant filter is integrated within the processor.

14 . The fitness monitor of claim 11 , wherein the processor is further configured to determine filter coefficients based on the identified motion component in the PPG signal for the first time period and configure the time-variant filter with the determined filter coefficients.

15 . The fitness monitor of claim 11 , wherein the cardiac component of the PPG signal for the second time period is isolated upon each occurrence of the motion component being identified based on the determined one or more frequencies of the motion signal and the motion component.

16 . The fitness monitor of claim 11 , wherein the processor is further configured to pre-condition the PPG signal by attenuating frequency components of the PPG signal below the frequency band that includes the cardiac component and/or attenuates frequency components above the frequency band that includes the cardiac component.

17 . The fitness monitor of claim 11 , wherein the cardiac component is associated with heart rate.

18 . A fitness monitor for monitoring a cardiac signal of a user, the device comprising:
an emitter configured to transmit light toward skin of the user; a receiver configured to receive a reflection of the transmitted light and provide a photoplethysmogram (PPG) signal based on the received reflection of the transmitted light, the PPG signal including a cardiac component and a motion component; an inertial sensor configured to provide a motion signal based on sensed movement of the fitness monitor; a time-variant filter receiving the PPG signal, and a processor coupled to the emitter, the receiver, the inertial sensor and the time-variant filter, the processor configured to:
determine one or more frequencies associated with the motion signal and the PPG signal provided during a first time period,
identify the cardiac component in the PPG signal for the first time period based on the determined one or more frequencies of the motion signal and the PPG signal, and
filter, via the time-variant filter, the PPG signal provided for a second time to isolate the cardiac component of the PPG signal for the second time period based on the identified cardiac component.

19 . The fitness monitor of claim 18 , wherein the time-variant filter is integrated within the processor.

20 . The fitness monitor of claim 18 , wherein the processor is further configured to determine filter coefficients based on the identified cardiac component in the PPG signal for the first time period and configure the time-variant filter with the determined filter coefficients.

Assignees

• Garmin Switzerland Gmbh

Inventors

• Macdonald Paul R
• Kulach Christopher J

Classifications

• A61B5/7278

  Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals · CPC title

• A61B5/02416 Primary

  using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence) · CPC title

• A61B5/165

  Evaluating the state of mind, e.g. depression, anxiety · CPC title

• A61B5/681

  Wristwatch-type devices · CPC title

• A61B2562/0219

  Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches · CPC title