Biosensor S/N Ratio Improvement via Adaptive Baseline Noise Subtraction
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Solution Overview
Problem
Existing biosensors face challenges in maintaining a high signal-to-noise ratio (S/N ratio) when noise components such as extraneous light vary, particularly due to movement or changes in stray light, which reduces the accuracy of photoplethysmographic signals.
Innovation Solution
A biosensor design that includes a driving signal generation unit, a light-emitting element, a light-receiving element, a baseline signal acquisition unit, and a difference acquisition unit, which removes the pulse wave component from the detection signal to obtain a baseline signal that varies with noise components, allowing for the subtraction of noise and enhancement of the S/N ratio through difference acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference voltage subtraction method is used to improve S/N ratio, then the S/N ratio is improved under stable noise conditions, but the method fails when noise components vary due to movement or extraneous light changes
Solution Approach 1:
The patent applies dynamics by making the reference signal adaptive rather than fixed. The reference signal is continuously updated to track varying noise components, allowing the system to maintain high S/N ratio under changing conditions. This is achieved through dynamic adjustment of the reference voltage based on real-time noise characterization.
Solution Approach 2:
The patent implements feedback mechanisms where the detected signal is used to continuously refine the reference signal. By monitoring the actual noise characteristics and feeding this information back into the reference signal generation, the system automatically adapts to varying noise conditions, resolving the contradiction between maintaining precision and handling variability.
2Device complexity
If simple reference voltage subtraction is implemented, then device complexity is reduced, but the system cannot respond to rapid noise variations
Solution Approach 1:
The patent applies preliminary action by pre-characterizing noise components and establishing reference signals before actual measurement. This allows the system to have reference data ready in advance, enabling rapid response to noise variations without requiring complex real-time processing during the critical measurement phase.
Solution Approach 2:
The patent uses copying by creating reference signals that replicate the noise characteristics. Instead of directly processing and removing noise in real-time, the system creates copies of the noise profile from reference measurements, which are then subtracted from the detection signal. This approach simplifies the processing while maintaining fast response capability.
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
This approach effectively improves the S/N ratio of photoplethysmographic signals even when noise components change, enhancing the accuracy of detected signals by isolating and removing noise variations.
Implementation Method 1
light emitted from a light-emitting diode (light-emitting element)
Implementation Method 2
photodiode (light-receiving element)... light-receiving output (current signal)
Implementation Method 3
characteristics where hemoglobin in the blood absorbs light in a range from visible light to infrared light
Data Source
AI summary
There is provided a biosensor capable of improving the S/N ratio of a final photoplethysmographic signal regardless of the change in a noise component such as extraneous light.A biosensor includes a driving signal generation unit for generating a pulsed driving signal, a light-emitting element for emitting light in response to a generated driving signal, a light-receiving section including a light-receiving element for outputting a detection signal in accordance with the intensity of light received and an amplification unit for amplifying a detection signal output from the light-receiving element, a filter unit for removing a pulse wave component from a detection signal output from the light-receiving section to obtain a baseline signal, and a differential amplification unit for taking a difference between a detection signal output from the light-receiving section and a baseline signal obtained by the filter unit.