Pipeline-Structured Matched Filter for Optical Spectroscopy Noise Reduction
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Solution Overview
Problem
Current optical spectroscopy systems face challenges in minimizing current leakage and nonlinear effects in switching circuits, distinguishing light sources, and reducing white Gaussian noise without additional circuitry, while also being able to modulate and demodulate light effectively for accurate hemodynamic measurements.
Innovation Solution
The system employs a pipeline-structured matched filter and dual slope analog-digital converter, utilizing Walsh codes for modulating and demodulating light, and time-divided spread spectrum codes to increase light intensity, and uses a reference clock for sampling to minimize noise, all integrated into a mobile and expandable firmware-based system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional matched filter structure is used, then light modulation and demodulation can be performed, but current leakage and nonlinear effects occur in the switching circuit
Solution Approach 1:
The matched filter is divided into multiple stages with separate switching circuits for each stage. Each stage processes a portion of the signal independently, which isolates the harmful effects (current leakage and nonlinearities) to specific stages rather than affecting the entire circuit. This segmentation allows for better control and compensation of switching circuit imperfections while maintaining overall measurement accuracy.
2Productivity
If multiple light sources are used for hemodynamic measurement, then comprehensive data can be collected, but it becomes difficult to distinguish which light source emitted which light
Solution Approach 1:
Each light source modulates its emitted light with a unique periodic Walsh code sequence. These codes are orthogonal to each other, meaning they can be independently identified even when multiple sources emit simultaneously. The matched filter uses corresponding Walsh codes to demodulate and identify which light source emitted the detected light, enabling comprehensive data collection from multiple sources while maintaining clear source identification.
3Reliability
If the duration of Walsh codes is increased to improve signal detection, then more light energy can be accumulated, but the light intensity per unit time decreases
Solution Approach 1:
The system dynamically adjusts the Walsh code duration and light intensity parameters based on measurement requirements. By optimizing the balance between code duration and intensity, the system achieves sufficient signal accumulation for accurate detection while maintaining adequate light intensity for penetrating tissue. The dynamic optimization allows the system to adapt to different measurement conditions and tissue depths.
4Reliability
If additional circuitry such as phase locked loop is added to minimize white Gaussian noise, then noise reduction is achieved, but device complexity increases
Solution Approach 1:
The system uses the reference clock that already exists for light source modulation as the sampling clock for the matched filter operation. This self-service approach eliminates the need for additional phase locked loop circuitry or separate clock generation systems. By reusing the existing reference clock, the system achieves synchronized sampling that minimizes white Gaussian noise while avoiding the complexity of additional noise reduction circuitry.
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 allows for efficient light modulation and demodulation, reduced noise, and increased light intensity with the same total energy, enabling accurate hemodynamic measurements and firmware updates, while minimizing hardware changes and additional circuitry.
Implementation Method 1
a pipeline-structured matched filter for sequentially connecting input voltage transmitted through an amplifier to a first capacitor and a second capacitor through a first switch stage
Implementation Method 2
a dual slope analog-digital converter for sequentially receiving electric charge stored in the first and second capacitors through a second switch stage and digitizing the input voltage
Data Source
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AI summary
Disclosed are an optical spectroscopy system using a pipeline-structured matched filter and a dual-slope analog digital converter, and a method for controlling the optical spectroscopy system. The optical spectroscopy system may comprise: a pipeline-structured matched filter sequentially connecting input voltage, transmitted by means of an amplifier, to a first capacitor and a second capacitor by means of a first switch terminal; and a dual-slope analog digital converter for sequentially receiving, by means of a second switch terminal, the electric charge stored in the first capacitor and second capacitor, and digitizing the input voltage.