Dual-Membrane MEMS Microphone for Sensitivity and Contaminant Shielding
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Solution Overview
Problem
Existing piezoelectric microelectromechanical system (PMM) microphones face challenges in sensitivity and reliability due to the addition of a passive membrane, which can reduce resonance frequency and sensitivity, and are susceptible to environmental contaminants.
Innovation Solution
Incorporating a passive membrane mechanically coupled to the piezoelectric element with a column having a smaller cross-sectional area than the passive membrane and piezoelectric element, supported by compliant structures, to enhance force application and reduce mass loading, while maintaining a safe distance to avoid collisions and protect against environmental contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive membrane is added to the piezoelectric element, then sensitivity is enhanced by up to 12 dB, but the resonance frequency is reduced and device complexity increases
Solution Approach 1:
The passive membrane is nested within the microphone cavity, positioned between the acoustic port and the piezoelectric element. This nested configuration allows the passive membrane to enhance sensitivity by concentrating acoustic pressure on the piezoelectric element without requiring a complete redesign of the microphone structure, thereby improving measurement precision while limiting the increase in device complexity.
Solution Approach 2:
The passive membrane acts as an intermediary component that mediates between the incoming acoustic waves and the piezoelectric element. It concentrates and directs acoustic pressure onto the piezoelectric element, enhancing the coupling between acoustic input and electrical output, which improves sensitivity without directly modifying the piezoelectric element itself.
2Measurement precision
If the passive membrane is positioned close to the piezoelectric element to enhance force application, then sensitivity improves, but the risk of mechanical collision increases
Solution Approach 1:
The passive membrane is positioned to continuously interact with incoming acoustic waves and continuously transfer pressure to the piezoelectric element during operation. This continuous useful action maintains high sensitivity across the operating range while the spacing ensures that even during maximum displacement, mechanical collision is avoided, preserving reliability.
Solution Approach 2:
The design preemptively accounts for maximum displacement by positioning the passive membrane at a distance that prevents collision even under maximum sound pressure conditions. This preliminary anti-action approach ensures that sensitivity is maximized through close proximity while reliability is protected by pre-establishing sufficient clearance.
3Measurement precision
If the passive membrane is made larger to increase acoustic pressure on the piezoelectric element, then sensitivity improves, but mass loading increases and high-frequency performance deteriorates
Solution Approach 1:
The passive membrane is designed with specific local properties including optimal size, material composition, and positioning that concentrate acoustic pressure effectively on the piezoelectric element without excessive mass. This local optimization allows sensitivity enhancement while maintaining high-frequency response by avoiding unnecessary mass loading.
Solution Approach 2:
The design optimizes parameters such as the passive membrane's surface area, thickness, material density, and distance from the piezoelectric element to achieve the desired balance between sensitivity and high-frequency performance. By carefully adjusting these parameters, the system achieves up to 12 dB sensitivity improvement while minimizing mass loading effects that would degrade high-frequency response.
4Speed
If the piezoelectric element is exposed directly to the acoustic port, then high-frequency performance is maintained, but susceptibility to environmental contaminants increases
Solution Approach 1:
The passive membrane serves as a protective intermediary that is positioned between the acoustic port and the piezoelectric element. It allows acoustic waves to pass through and be concentrated onto the piezoelectric element while blocking environmental contaminants such as dust, moisture, and debris from directly contacting the sensitive piezoelectric element, thereby protecting against harmful factors while maintaining high-frequency performance.
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 passive membrane significantly enhances sensitivity by up to 12 dB and improves reliability by shielding the piezoelectric membrane from contaminants, maintaining high-frequency performance and reducing the risk of mechanical interference.
Implementation Method 1
a piezoelectric element configured to deform and generate an electrical potential responsive to impingement of sound waves on the piezoelectric microelectromechanical system microphone
Implementation Method 2
a passive membrane mechanically coupled to the surface of the piezoelectric element to increase sensitivity of the piezoelectric microelectromechanical system microphone
Data Source
AI summary
A piezoelectric microelectromechanical system microphone comprises a piezoelectric element configured to deform and generate an electrical potential responsive to impingement of sound waves on the piezoelectric microelectromechanical system microphone, a sensing electrode disposed on the piezoelectric element and configured to sense the electrical potential, and a passive membrane mechanically coupled to the surface of the piezoelectric element to increase sensitivity of the piezoelectric microelectromechanical system microphone.