Piezoelectric MEMS Microphone Feedback Loop for Lower Noise
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Solution Overview
Problem
Existing piezoelectric MEMS microphones suffer from noise interference and require improvements in noise floors and sensitivity, particularly in feedback transduction systems.
Innovation Solution
A feedback transduction loop is integrated with a piezoelectric MEMS transducer system, utilizing an operational amplifier and attenuator to reduce input referred noise, which is independent of the closed-loop system gain, and includes a differential design with opposite polarity signals from different MEMS beams to enhance noise and power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If piezoelectric MEMS transducers are used to eliminate backplate and squeeze film damping, then structural complexity is reduced and manufacturing is simplified, but noise floor and sensitivity performance deteriorate
Solution Approach 1:
The patent implements a feedback transduction system where the piezoelectric MEMS transducer is connected in a closed-loop configuration with an operational amplifier. The feedback path includes a first piezoelectric transducer generating a feedback signal that is combined with the input signal, and a second piezoelectric transducer that receives the combined signal. This feedback mechanism reduces input-referred noise by canceling out noise components through the feedback loop, thereby improving noise floor and sensitivity while maintaining the backplate-less structure.
Solution Approach 2:
The patent employs dynamic signal processing through the feedback transduction system. The operational amplifier dynamically adjusts the feedback signal based on the input signal characteristics, allowing the system to adaptively optimize noise performance across different operating conditions. This dynamic approach enables the system to maintain low noise floors and high sensitivity without requiring a rigid backplate structure.
2Measurement precision
If feedback transduction loop is integrated to reduce input referred noise, then noise performance is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the feedback transduction system. The operational amplifier simultaneously performs signal amplification, feedback signal generation, and noise cancellation. The two piezoelectric transducers are integrated into a single feedback loop architecture, combining sensing and feedback functions in one cohesive structure. This merging approach reduces the need for separate noise cancellation circuits, thereby limiting the increase in device complexity while achieving improved noise performance.
3Measurement precision
If attenuator is added to control feedback signal level, then signal integrity is maintained, but device complexity increases
Solution Approach 1:
The operational amplifier in the feedback transduction system performs multiple functions including signal amplification, feedback generation, and implicit signal level control. The feedback path itself acts as a natural attenuator by providing a controlled feedback signal level through the amplifier's gain characteristics. This multi-functionality approach eliminates the need for separate dedicated attenuator components, maintaining signal integrity while minimizing the increase in device complexity.
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 system achieves reduced noise and lower power consumption while maintaining signal integrity, particularly at low gain settings, improving the overall performance of piezoelectric MEMS microphones.
Implementation Method 1
a piezoelectric MEMS transducer configured to generate an electrical signal in response to a signal incident upon the piezoelectric MEMS transducer
Data Source
AI summary
Aspects of transducers with feedback transduction are described. One aspect is a transducer system comprising an operational amplifier having an inverting input, a non-inverting input, and an output. The transducer system also includes a piezoelectric microelectromechanical system (MEMS) transducer having a first node and a second node, wherein the first node is coupled to the inverting input of the operational amplifier, and wherein the piezoelectric MEMS transducer is configured to generate an electrical signal across the first node and the second node in response to a signal incident upon the piezoelectric MEMS transducer. The transducer system also includes an attenuator having an input and an output, wherein the input of the attenuator is coupled to the output of the operational amplifier, and wherein the output of the attenuator is coupled to the second node of the piezoelectric MEMS transducer.