Same-Side Radar Vital Sign Monitoring with Asymmetric Antenna Gains
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Solution Overview
Problem
Conventional non-contact vital sign monitoring systems face challenges in canceling out random body movement effects, particularly when the subject is positioned against a wall or on a bed, due to the configuration requirements of radar devices at opposite sides of the subject.
Innovation Solution
Configuring two radar devices on the same side of a biological subject with different gain antennas to transmit and receive signals, allowing for self- and mutual-injection locking states that cancel out Doppler shift components from body movement while preserving vital sign signals by maintaining different frequency modulation magnitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two radar devices are configured at opposite sides of the subject to cancel body movement effects, then the body movement cancellation capability is improved, but the system cannot detect vital signs when the subject stands against a wall or lays on a bed
Solution Approach 1:
The patent employs asymmetric configuration of two radar devices on the same side of the subject, with different antenna gains (first antenna has higher gain than second antenna). This asymmetric setup creates unequal Doppler shift magnitudes from body movement for the two radar devices, allowing them to be in self- and mutual-injection locking states while maintaining the ability to cancel body movement effects and detect vital signs in restricted positions.
2Adaptability or versatility
If two radar devices with different gain antennas are configured on the same side to enable self- and mutual-injection locking, then the adaptability for restricted positions is improved, but the body movement cancellation capability must be maintained
Solution Approach 1:
The patent changes the parameter of antenna gain to create asymmetric radar device configuration. The first antenna has a higher gain value than the second antenna, which creates different Doppler shift magnitudes from body movement for each radar device. This parameter change enables the system to achieve both adaptability for restricted positions and body movement cancellation through self- and mutual-injection locking states.
3Object-affected harmful factors
If the Doppler shift components from body movement are made equal in magnitude and out of phase for cancellation, then the body movement effect is reduced, but the vital sign signals must remain significantly different in magnitude to be detected
Solution Approach 1:
The patent applies local quality by making each radar device have different antenna gains, causing them to receive different magnitudes of Doppler shift from body movement. The first radar device receives a larger Doppler shift component than the second radar device. This local differentiation allows the system to cancel body movement effects through out-of-phase equal-magnitude components while preserving vital sign signals with significantly different magnitudes for detection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of vital signs, such as respiration and heartbeat, even when the subject is moving or in restricted positions, by effectively canceling out body movement-induced Doppler shifts while maintaining distinct vital sign signals.
Implementation Method 1
the subject's vital signs can be detected according to the Doppler shift of the reflected signals
Implementation Method 2
the first radar device and the second radar device are operated in a self- and mutual-injection locking state
Implementation Method 3
the two SIL radar apparatuses can be mutual-injection locked to each other to real-time cancel the random body movement effect
Data Source
AI summary
A non-contact vital sign monitoring system transmits wireless signals to the same side of a biological subject via two antennas with different gains, and the two antennas receive two reflected signals from the biological subject with random body movement. Under a proper setup of the two antennas, the two reflected signals can be adjusted by an amplitude and phase adjusting unit to have the Doppler shift components caused by body movement with equal magnitude and out of phase and the Doppler shift components caused by vital signs with different magnitude. Therefore, the random body movement effect can be cancelled based on the relation between the two reflected signals in using the system to monitor the vital signs of the subject.