Configurable Attenuator for MEMS Transducer Acoustic Overload
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Solution Overview
Problem
MEMS transducers, particularly piezoelectric MEMS microphones, face challenges in meeting the stringent requirement for the acoustic overload point (AOP), leading to performance issues such as distortion and reduced dynamic range in noisy and high-pressure environments, like smart speakers and hearable devices.
Innovation Solution
A MEMS transducer system with a configurable attenuator and integrated circuit that selectively attenuates signals, allowing for dynamic adjustment of the acoustic overload point by using a gain controller or pick-off pads to manage high-pressure events and reduce sensitivity, thereby increasing the AOP and maintaining acoustic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transducer sensitivity is increased to improve signal output, then the acoustic overload point decreases causing distortion in high-pressure environments
Solution Approach 1:
The patent implements a configurable attenuator with multiple attenuation levels (e.g., 0 dB, -6 dB, -12 dB, -18 dB) that can be dynamically selected based on operating conditions. This allows the system to adapt the sensitivity of the transducer system in real-time, switching between high sensitivity (0 dB) for normal conditions and reduced sensitivity (higher attenuation) for high-pressure environments, thereby resolving the contradiction between signal output sensitivity and acoustic overload point
Solution Approach 2:
The patent changes the attenuation parameter of the signal path by selecting different attenuation levels through the configurable attenuator. By adjusting the attenuation parameter (e.g., switching between 0 dB and -18 dB), the system modifies the effective sensitivity of the transducer, allowing it to operate optimally across different pressure conditions without physical hardware changes
2Device complexity
If a fixed sensitivity transducer is used to simplify design, then the dynamic range is reduced in varying acoustic environments
Solution Approach 1:
The patent makes the transducer system multi-functional by incorporating a configurable attenuator that provides multiple attenuation levels (0 dB, -6 dB, -12 dB, -18 dB). This single system can now serve multiple acoustic environments - from quiet rooms to windy outdoor conditions - by selecting the appropriate attenuation level, thereby achieving universal adaptability without requiring multiple different transducer designs
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 solution effectively increases the acoustic overload point, reducing distortion and maintaining the user experience in voice user interface applications and handling wind noise, by dynamically controlling sensitivity and managing high-pressure inputs.
Implementation Method 1
piezoelectric MEMS microphones
Implementation Method 2
capacitive microphones
Implementation Method 3
The attenuator may include a dividing element... Each such attenuation branch preferably has a switch and a capacitance
Data Source
AI summary
A MEMS transducer system has a transducer configured to convert a received signal into an output signal for forwarding by a transducer output port, and an integrated circuit having an IC input in communication with the transducer output port. The IC input is configured to receive an IC input signal produced as a function of the output signal. The system also has a dividing element coupled between the IC input and the transducer output port. The dividing element is configured to selectively attenuate one or more signals into the IC input to at least in part produce the IC input signal. Other implementations may couple a feedback loop to the ground of the transducer (similar to bootstrapping), or pick off voltages at specific portions of the transducer.