Biosensor Antenna Impedance Matching for Heartbeat Detection
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Solution Overview
Problem
Existing biosensor devices using radio waves face challenges in accurately measuring heartbeat and respiration waveforms due to environmental reflections and noise, and require complex configurations and high costs when using multiple frequencies to adapt to changes in ambient conditions.
Innovation Solution
A biosensor device with a signal generator, antenna, variable matching circuit, and control circuitry that adjusts impedance based on detection signals to maintain accurate waveform measurement, using a continuous wave signal and quadrature detection circuitry to minimize intermodulation components and simplify configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small-sized antenna smaller than a wavelength is used for miniaturization, then the device size is reduced, but the resonance frequency changes due to human body influence and sensor sensitivity deteriorates
Solution Approach 1:
The patent implements a variable matching circuit that dynamically adjusts impedance parameters in real-time based on detected ambient conditions. This dynamic adaptation compensates for resonance frequency shifts caused by human body proximity, maintaining optimal sensor sensitivity despite using a miniaturized antenna smaller than the wavelength.
2Adaptability or versatility
If input signals with a plurality of frequencies are used to reduce sensitivity change, then adaptability to ambient environment improves, but a large number of inter modulation components are generated and device complexity increases
Solution Approach 1:
Instead of using multiple frequencies, the patent changes the impedance parameters of the matching circuit dynamically. This single-frequency approach with variable impedance parameters achieves adaptability to ambient conditions without generating intermodulation components, thereby simplifying the transmission circuit configuration and reducing device complexity.
3Speed
If a high frequency wave is used for Doppler sensing, then the detection range is extended, but the influence of reflection from ambient environment and external noise increases
Solution Approach 1:
The patent employs a feedback mechanism where the detection circuit continuously monitors the reflected signal characteristics, and the control circuit adjusts the matching circuit parameters accordingly. This feedback loop enables real-time compensation for environmental reflections and external noise, maintaining high-frequency Doppler sensing performance while mitigating harmful environmental influences.
4Measurement precision
If impedance matching is performed for stable sensitivity, then measurement accuracy improves, but the configuration becomes complex and cost increases
Solution Approach 1:
The patent implements a self-adjusting impedance matching system where the control circuit automatically detects ambient conditions and adjusts the matching circuit parameters without external intervention. This self-service mechanism maintains optimal measurement accuracy while avoiding the complexity of manual matching configurations and reducing overall device cost.
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
The device achieves high detection accuracy and a simple configuration by adaptively controlling the biosensor antenna's impedance, effectively reducing noise interference and maintaining sensitivity across changing ambient conditions.
Implementation Method 1
an antenna 1 to emit the continuous wave signal as a radio wave
Implementation Method 2
a variable matching circuit 21 to perform impedance matching between the signal generating unit 11 and the antenna 1
Implementation Method 3
a first mixer 331 to multiply the continuous wave signal by the reflected signal
Data Source
AI summary
Provided is a biosensor device including: a signal generating unit for generating a continuous wave signal; an antenna for emitting the continuous wave signal as a radio wave; a variable matching circuit for performing impedance matching between the signal generating unit and the antenna; a detection circuit for outputting a detection signal on the basis of the continuous wave signal generated by the signal generating unit and a reflected signal of a radio wave incident on the antenna; and a control unit for controlling an element value of the variable matching circuit from the detection signal in a predetermined period corresponding to one cycle or more time in which heartbeat and respiration waveforms can be measured on the basis of the detection signal.