Differential Directional Acoustic Sensor Using Opposite Polarity MEMS Transducers
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Solution Overview
Problem
Traditional omnidirectional MEMS microphones using a dual-backplate structure struggle to generate a differential signal in directional microphone designs, which are based on cantilever structures rather than fixed backplates.
Innovation Solution
The proposed acoustic sensor device employs two MEMS transducers with opposite polarity outputs and opposite directional movements when exposed to sound waves, allowing for the generation of a composite differential output through subtraction of these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dual-backplate structure is used in omnidirectional MEMS microphones, then a differential signal can be generated with doubled amplitude, but this structure cannot be applied to directional microphone designs based on cantilever structures
Solution Approach 1:
The patent divides the single transducer system into two separate cantilever transducers (first and second transducers). Each transducer independently generates an output signal, enabling differential signal processing without requiring a dual-backplate structure. This segmentation allows directional microphones to achieve differential signal generation capability.
Solution Approach 2:
The patent introduces asymmetry in the initial deflection configuration of the two cantilevers. The first cantilever has an initial deflection in one direction while the second cantilever has an initial deflection in the opposite direction. This asymmetric configuration ensures that when exposed to sound waves, the transducers move in opposite directions, generating opposite polarity signals suitable for differential processing.
2Power
If two transducers with opposite polarity outputs are used, then the composite output signal amplitude is doubled, but the device requires more complex transducer configuration and signal processing
Solution Approach 1:
The patent combines the outputs of two cantilever transducers through differential signal processing. By subtracting the output signals of the first and second transducers, the system merges their individual outputs into a single composite signal with doubled amplitude. This merging approach efficiently utilizes the opposite polarity outputs to achieve signal amplification.
Solution Approach 2:
The patent changes the polarity parameter of the second transducer's output relative to the first transducer. By configuring the second cantilever with opposite initial deflection, its output signal has opposite polarity to the first transducer. This parameter change enables constructive interference when signals are differentially processed, doubling the composite output amplitude.
3Measurement precision
If cantilever-based transducers are used in directional microphones, then directional sensitivity is achieved, but the traditional dual-backplate sensing architecture cannot generate differential signals
Solution Approach 1:
The patent inverts the traditional dual-backplate approach by using two separate cantilever transducers instead of a single membrane between backplates. Each cantilever is configured with opposite initial deflections, causing them to move in opposite directions in response to sound waves. This inversion maintains directional sensitivity while enabling differential signal generation.
Solution Approach 2:
The patent makes the cantilever transducer configuration universal by demonstrating that cantilevers can perform both directional sensing and differential signal generation functions. By properly configuring the initial deflections and connecting the transducers to differential circuitry, the same transducer type serves multiple purposes previously requiring different structures.
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 configuration effectively doubles the amplitude of the composite output signal while canceling out signal components of equal amplitude, phase, and polarity, thereby reducing noise and distortion.
Implementation Method 1
a first microelectromechanical system (MEMS) transducer supported by the substrate, the first MEMS transducer configured to generate a first output signal when exposed to a sound wave
Data Source
AI summary
An acoustic sensor device includes a substrate and a first transducer supported by the substrate, the first transducer configured to generate a first output signal when exposed to a sound wave. The acoustic sensor device also include a second transducer supported by the substrate, the second transducer configured to generate a second output signal when exposed to a sound wave. The first transducer and the second transducer are configured such that the first output signal generated by the first transducer and the second output signal generated by the second transducer are opposite in polarity.