Band-pass Acoustic Filter for MEMS Microphone SNR
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Solution Overview
Problem
MEMS microphones have a narrow bandwidth resonance frequency and manufacturing tolerance uncertainties, making them unsuitable for direct detection of specific frequencies, and existing solutions degrade signal-to-noise ratio (SNR) with additional electronic components.
Innovation Solution
A band-pass acoustic filter comprising at least two MEMS microphone chips and an ASIC chip, where the output signals are processed and coupled in series, with adjustable resonance frequency settings for improved SNR and frequency response, including a metal case forming a back cavity for acoustic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a filter is provided in the ASIC to filter the sound electric signal, then the frequency response is improved, but the signal-to-noise ratio (SNR) is degraded due to extra electronic components
Solution Approach 1:
The patent replaces electronic filtering components with an acoustic filter structure that uses physical acoustic pathways and chambers to achieve frequency filtering. The acoustic filter includes a front chamber, back chamber, and acoustic ports that create resonant frequencies to pass specific bands while blocking others, eliminating the need for electronic filters that would add noise and complexity.
Solution Approach 2:
The patent extracts and removes the electronic filter components from the system by implementing filtering functionality through the acoustic structure itself. The acoustic filter is integrated into the microphone housing and chamber structure, taking out the need for separate electronic filtering components that would otherwise be required in the ASIC.
2Adaptability or versatility
If a filter is provided in the ASIC to filter the sound electric signal, then the frequency response is improved, but the device complexity increases due to extra electronic components
Solution Approach 1:
The patent merges the filtering function with the existing acoustic structure of the microphone. The acoustic filter is integrated into the housing and chamber design, combining the housing structure, acoustic pathways, and filtering function into a single unified design, thereby eliminating separate electronic filter components and reducing overall device complexity.
Solution Approach 2:
The patent replaces electronic filtering components with an acoustic filter structure that uses physical acoustic pathways and chambers to achieve frequency filtering. This substitution eliminates the need for electronic filters, capacitors, and resistors that would add complexity to the ASIC and overall device.
3Measurement precision
If the resonance frequency is adjusted for specific frequency detection, then the frequency response is improved, but the bandwidth becomes too narrow due to manufacturing tolerance
Solution Approach 1:
The patent employs a composite acoustic filter structure with multiple chambers (front chamber and back chamber) and multiple acoustic ports working together. This composite structure creates a band-pass filter with a broader effective bandwidth while maintaining precise frequency selection. The interaction between multiple acoustic elements provides both frequency precision and bandwidth.
Solution Approach 2:
The patent segments the acoustic filter into multiple functional components including a front chamber with first acoustic ports, a back chamber with second acoustic ports, and intermediate acoustic pathways. This segmentation allows each component to contribute to different aspects of frequency filtering, achieving both precise frequency detection and adequate bandwidth through the combined effect of multiple segmented elements.
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
Enhances signal-to-noise ratio and frequency response by broadening the resonance bandwidth and improving high-frequency sound characteristics, enabling effective detection of sound waves, including ultrasonic waves, with reduced electronic complexity.
Implementation Method 1
a MEMS microphone includes a MEMS microphone chip and an integrated circuit (ASIC), for converting received sound wave into sound electrical signal
Implementation Method 2
the MEMS microphone chips are acoustically coupled through the back cavity
Implementation Method 3
The resonance frequency can depend on the Helmholtz resonator formed by the front chamber (or back chamber/cavity)
Data Source
AI summary
The present invention discloses a band-pass acoustic filter and an acoustic sensing apparatus. The band-pass acoustic filter including at least two MEMS microphone chips and an ASIC chip, wherein the output signals of the MEMS microphone chips are processed in the ASIC chip after being coupled.