Biological Sensor Offset Voltage Signal-to-Noise Ratio
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Solution Overview
Problem
Conventional biological sensors face challenges in maintaining a high signal-to-noise ratio due to external light interference, leading to reduced accuracy in detecting biological information such as oxygen saturation, which increases costs and power consumption.
Innovation Solution
A biological sensor design that includes a driving signal generating means for pulse-form driving signals, an amplifying means with offset voltage to cut noise components, and a computing means to process the detection signal, allowing for improved signal-to-noise ratio by offsetting the reference potential of the amplifier and varying amplification rates based on signal amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplification rate of the amplifier is increased to enhance the pulsation component signal, then the signal amplitude improves, but the amplifier output saturates due to external light noise
Solution Approach 1:
The patent segments the amplification process into multiple stages: a first amplifier with low gain processes the raw detection signal to avoid saturation, while a second amplifier with high gain amplifies the already-filtered signal. This segmentation allows each amplifier to operate within its optimal gain range, preventing saturation while achieving the desired signal amplitude for accurate measurement.
Solution Approach 2:
The patent applies preliminary noise filtering and DC component removal before the final amplification stage. By removing the DC component and filtering noise early in the signal processing chain, the subsequent high-gain amplification only amplifies the relevant AC pulsation signal, preventing saturation caused by large DC offsets and noise.
2Reliability
If the amplification rate is reduced to prevent output saturation, then the amplifier remains stable, but the amplitude of the pulsation component drops, reducing detection accuracy
Solution Approach 1:
The patent divides the amplification function across two amplifiers: the first amplifier provides stable, low-gain amplification that prevents saturation, while the second amplifier provides high-gain amplification of the cleaned signal. This segmentation allows the system to achieve both stability and sufficient signal amplitude for accurate measurement.
Solution Approach 2:
The patent introduces intermediate signal processing steps (DC component removal and noise filtering) between the light detection and final amplification. These intermediate processing stages act as mediators that prepare the signal for high-gain amplification by removing components that would cause saturation, enabling both stability and high amplitude output.
3Measurement precision
If high-resolution A/D converter is used to resolve the pulsation component in the presence of external noise, then the detection resolution improves, but the system costs increase
Solution Approach 1:
The patent performs preliminary noise filtering and DC component removal in the analog domain before the A/D conversion stage. By removing the DC offset and filtering noise before digitization, the system reduces the dynamic range requirements for the A/D converter, allowing the use of lower-resolution (and lower-cost) converters while still achieving sufficient measurement precision.
Solution Approach 2:
The patent introduces analog signal processing circuits (filters and DC removal circuits) as intermediaries between the photodetector and the A/D converter. These intermediary circuits condition the signal to remove problematic components, enabling the use of simpler, lower-cost A/D converters that would not be sufficient if they had to handle the full dynamic range including large DC offsets and noise.
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 solution effectively improves the signal-to-noise ratio, reducing noise interference and enhancing the accuracy of biological information detection while minimizing power consumption and costs.
Implementation Method 1
a light-emitting element that emits light in response to the driving signal generated by the driving signal generating means
Implementation Method 2
a light-receiving element that outputs a detection signal based on an intensity of received light
Implementation Method 3
an amplifying means including an amplifier that amplifies the detection signal outputted from the light-receiving element
Data Source
AI summary
A biological sensor capable of improving the signal-to-noise ratio of a detection signal obtained by a light-receiving element and amplified by an amplifier is provided.The biological sensor includes a driving signal generating unit that generates a pulse-form driving signal, a light-emitting element that emits light in response to the generated driving signal, a light-receiving element that outputs a detection signal based on an intensity of received light, an amplifying unit including first and second operational amplifiers that amplify the outputted detection signal, an offset signal generating unit and a voltage dividing resistor group that generate a pulse-form offset voltage for offsetting a reference potential of the first operational amplifier when amplifying the detection signal and apply the offset voltage to the first operational amplifier, and a computation unit that obtains biological information by processing the detection signal amplified by the amplifying unit.