Capacitance Sensor With Segmented Electrodes for Wide Dynamic Range
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Solution Overview
Problem
Conventional microphones face challenges in achieving a wide dynamic range due to trade-offs between detection sensitivity and total harmonic distortion, leading to limitations in detecting sound pressures across a broad range without compromising sound quality.
Innovation Solution
A capacitance sensor and acoustic sensor design where multiple sensing units with different sensitivities are integrated on a single substrate, with varying electrode plate areas and back plate configurations to reduce mismatching and enhance impact resistance, allowing for the combination of signals to widen the detection range without sacrificing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-sensitive acoustic sensor is used to detect low sound pressure, then detection sensitivity is improved, but total harmonic distortion increases when detecting high sound pressure
Solution Approach 1:
The acoustic sensor is divided into multiple sensing units with different sensitivity levels. Each sensing unit has a diaphragm with a specific area (first diaphragm with larger area for low sensitivity, second diaphragm with smaller area for high sensitivity). This segmentation allows the system to handle both low and high sound pressure levels simultaneously without excessive harmonic distortion.
Solution Approach 2:
Different regions of the back plate are designed with different rigidity characteristics. The back plate includes a first region with lower rigidity (larger aperture ratio) for the first sensing unit and a second region with higher rigidity (smaller aperture ratio) for the second sensing unit. This local quality differentiation optimizes the performance of each sensing unit for its specific detection range.
2Adaptability or versatility
If multiple independent acoustic sensors are arranged to widen detection range, then dynamic range is improved, but fluctuations in detection sensitivity and acoustic characteristics mismatch occur
Solution Approach 1:
Multiple sensing units are integrated on a single substrate rather than using separate independent sensors. The first and second sensing units share the same substrate and back plate structure, which ensures consistent acoustic characteristics and reduces sensitivity fluctuations. This merging approach maintains uniformity in detection performance across different sensing units.
3Measurement precision
If the diaphragm area is reduced to increase sensitivity, then detection sensitivity is improved, but impact resistance is reduced
Solution Approach 1:
The back plate is designed with spatially varying rigidity characteristics. The region corresponding to the smaller second diaphragm has higher rigidity (smaller aperture ratio) to provide better impact resistance, while the region corresponding to the larger first diaphragm has lower rigidity (larger aperture ratio) for optimal acoustic sensitivity. This local quality differentiation allows each sensing unit to have optimized performance for its specific requirements.
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 integrated design reduces fluctuations in detection sensitivity and acoustic characteristics mismatch, enabling a microphone with a wide dynamic range from low to high sound pressures while improving impact resistance and durability.
Implementation Method 1
the acoustic sensor is a capacitance acoustic sensor manufactured by using the MEMS technique
Data Source
AI summary
A capacitance sensor has a substrate, a vibration electrode plate formed over an upper side of the substrate, a back plate formed over the upper side of the substrate to cover the vibration electrode plate, and a fixed electrode plate arranged on the back plate facing the vibration electrode plate. At least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions. A sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions. The plurality of sensing units output a plurality of signals having different sensitivities. At least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units.