System and method to compensate for transit-induced vibration when detecting heart rate using radar sensors
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Publication Number
US-11826173-B2
Publication Date
2023-11-28
Expiration Date
Abstract
A system and method to compensate for transit-induced vibration when detecting heart rate using radar sensors is provided. Embodiments provide a radio frequency RF sensor for heart rate detection when a subject is in transit (e.g., in a vehicle and/or subject to human-induced motion), where the RF sensor is designed to cancel vibration noise while preserving a cardiac signal in a radar response so that a heart rate, respiratory rate, and related physiological parameters of a subject under test can be extracted. In some examples, a heart rate variability (HRV) and/or state of the subject under test can be derived from these physiological parameters as well. The RF sensor with vibration cancellation can be installed in multiple locations in a vehicle, including a car seat, a steering wheel, a roof of the vehicle, a visor, or a rearview mirror; alternatively, the components may be held or worn by a subject, or arranged proximate to a subject.
Core Innovation
The disclosed invention relates to detecting heart rate of a subject under test while the subject is exposed to transit-induced vibration, where an RF transmitter transmits a radio frequency (RF) signal toward the subject and an RF receiver receives an RF response signal comprising a reflection of the RF signal. The RF response signal is affected by motion artifacts that can swamp weak cardiac phase modulation in the RF response.
A gyroscope signal path provides a motion signal, and the gyroscope signal path is equalized to the RF receive signal path utilizing an adaptive equalizer. The method cancels a vibration component of the RF response signal using the motion signal to produce a corrected response signal, from which a cardiac signal of the subject under test is extracted.
The invention further defines adaptive equalization by calibrating the adaptive equalizer with the vehicle operating and with no human subject present, or by digitally filtering the motion signal using the adaptive equalizer with a set of tap weights trained with a learning algorithm. In a related RF sensor and system implementation, the adaptive equalizer applies a distortion to the motion signal matched to a receive path between an antenna coupled to the RF transceiver and the processing device, enabling corrected response signal extraction for heart rate sensing.
Claims Coverage
The independent claims are directed to a method for detecting heart rate under transit-induced vibration using RF reflection plus gyroscope-referenced adaptive equalization and vibration-component cancellation, and to an RF sensor and a heart rate detection system implementing the same concepts in a vehicle seat context. Across the independent claims, the inventive features center on adaptive equalization of a gyroscope motion signal to match an RF receive signal path, cancellation of a vibration component in the RF response to obtain a corrected response signal, and extracting a cardiac signal; the vehicle-related calibration/training refinements and receive-path matched distortion further define how the equalizer is configured.
Rf transmission, rf reflection reception, and corrected-response cardiac extraction
transmitting a radio frequency (RF) signal toward the subject under test; receiving a RF response signal comprising a reflection of the RF signal; cancelling a vibration component of the RF response signal using the motion signal to produce a corrected response signal; and extracting a cardiac signal of the subject under test from the corrected response signal
Gyroscope-referenced adaptive equalization of the motion signal path
receiving a motion signal from a gyroscope signal path; equalizing the gyroscope signal path to the RF receive signal path utilizing an adaptive equalizer
Vehicle operating calibration with no human subject present for equalizer further equalization
the subject under test is in a vehicle, the transmitting of the RF signal is performed with a vehicle-mounted RF transmitter, the receiving of the RF response signal is performed with a vehicle-mounted RF receiver, the receiving of the motion signal from the gyroscope signal path is performed with a vehicle-mounted gyroscope element, and the method comprises calibrating the adaptive equalizer with the vehicle operating and with no human subject present to further equalize the gyroscope signal path to the RF receive signal path
Digitally filtering gyroscope motion signal using adaptive equalizer tap weights trained with a learning algorithm
the method further comprises digitally filtering, by the adaptive equalizer, the motion signal from the gyroscope signal path using a set of tap weights trained with a learning algorithm
Adaptive equalizer applying receive-path matched distortion to the motion signal
wherein the adaptive equalizer is configured to apply a distortion to the motion signal matched to a receive path between an antenna coupled to the RF transceiver and the processing device
RF sensor architecture with RF transceiver, gyroscope, adaptive equalizer, and processing device for vibration cancellation and cardiac extraction
an RF transceiver mounted to the substrate; a gyroscope mounted to the substrate; an adaptive equalizer coupled to the gyroscope; and a processing device coupled to the RF transceiver and the gyroscope, the processing device configured to cause the RF transceiver to transmit an RF signal toward a subject under test; receive a RF response signal comprising a reflection of the RF signal from the RF transceiver; monitor a motion signal from the gyroscope; cancel a vibration component of the RF response signal using the motion signal from the gyroscope to produce a corrected response signal; and extract a cardiac signal of the subject under test from the corrected response signal
Vehicle seat heart rate detection system with RF sensor and gyroscope-based vibration cancellation
a vehicle comprising a seat; a radio frequency (RF) sensor coupled to the seat, the RF sensor comprising: an RF transceiver mounted to the substrate; a gyroscope mounted to the substrate; an adaptive equalizer coupled to the gyroscope; and a processing device coupled to the RF transceiver and the gyroscope, the processing device configured to cause the RF transceiver to transmit an RF signal toward a subject under test; receive a RF response signal comprising a reflection of the RF signal from the RF transceiver; monitor a motion signal from the gyroscope; cancel a vibration component of the RF response signal using the motion signal from the gyroscope to produce a corrected response signal; and extract a cardiac signal of the subject under test from the corrected response signal
Network interface device for coupling the system to vehicle components
a heart rate detection system further comprising a network interface device configured to connect to a vehicle computer, a relay, or a sensor
Adaptive equalizer implemented as a multi-tap digital filter trained after installation in the vehicle
the heart rate detection system of claim 15 includes an adaptive equalizer implemented as a multi-tap digital filter that is trained after the RF sensor is installed in the vehicle
Vehicle-status-driven adjustment of the distortion applied to the motion signal
a heart rate detection system further adjusts the distortion applied to a motion signal based on a vehicle status signal received from the vehicle computer, a relay, or a sensor
Across the independent claims, the claim coverage focuses on combining RF reflection-based cardiac sensing with gyroscope-referenced adaptive equalization to equalize the gyroscope signal path to the RF receive signal path, cancel a vibration component of the RF response signal to obtain a corrected response signal, and extract a cardiac signal. The independent claims also define how the adaptive equalizer is configured for vehicle contexts by applying receive-path matched distortion and, in method-dependent alternatives, calibrating with vehicle operation and no human subject present or digitally filtering with tap weights trained using a learning algorithm.
Stated Advantages
cancelling a vibration component of the RF response signal using the motion signal to produce a corrected response signal for extracting a cardiac signal
Documented Applications
heart rate detection of a subject under test exposed to transit-induced vibration
heart rate detection in a vehicle, including a vehicle comprising a seat with an RF sensor coupled to the seat
RF sensor operation with vehicle-mounted RF transmitter, vehicle-mounted RF receiver, and a vehicle-mounted gyroscope element
non-vehicle use where RF and gyroscope elements are held by or worn by or placed proximate to the subject
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