MEMS Microphone Sensing Circuit With Dual Feedback for Low Distortion
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Solution Overview
Problem
Conventional microphone technologies suffer from distortion due to capacitive loads and circuit parasitics, and their sensitivity to acoustic pressure variations is affected by assembly variations, temperature changes, and environmental conditions, leading to instability and reduced performance.
Innovation Solution
Applying positive and negative feedback voltages via a voltage-to-voltage converter to an electromechanical sensor, utilizing capacitive couplings and feedback loops to reduce distortion and enhance sensitivity, stability, and prevent overload, by modifying the circuit gain and capacitance characteristics of the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional microphone technologies are used, then the device structure is simple, but signal distortion occurs due to capacitive loads and circuit parasitics
Solution Approach 1:
The patent applies positive feedback voltage to the electromechanical sensor to counteract the effects of capacitive loads and circuit parasitics. The feedback mechanism monitors the sensor output and adjusts the input voltage accordingly, creating a closed-loop system that compensates for distortion and maintains signal integrity despite the presence of parasitic elements.
Solution Approach 2:
The patent dynamically adjusts electrical parameters (voltage, current, or impedance) of the electromechanical sensor through the positive feedback mechanism. By changing these parameters in real-time, the system compensates for the distorting effects of capacitive loads and parasitics, improving signal quality without requiring a complete redesign of the circuit architecture.
2Ease of manufacture
If conventional electromechanical sensors are used, then the device is easy to manufacture, but sensitivity to acoustic pressure varies due to die stress and environmental conditions
Solution Approach 1:
The positive feedback voltage applied to the electromechanical sensor compensates for sensitivity variations caused by die stress and environmental conditions. The feedback loop continuously monitors the sensor response and adjusts the excitation voltage to maintain consistent acoustic pressure sensitivity, thereby improving measurement precision without complicating the manufacturing process.
Solution Approach 2:
The patent introduces dynamic adjustment capabilities to the electromechanical sensor through the positive feedback mechanism. This allows the sensor to adapt its electrical characteristics in real-time to compensate for environmental variations and die stress, maintaining optimal sensitivity across different operating conditions while preserving the simplicity of the original device structure.
3Reliability
If positive feedback voltage is applied to reduce distortion, then signal quality improves, but device complexity increases due to additional circuit components
Solution Approach 1:
The positive feedback circuit is designed to perform multiple functions simultaneously: it compensates for capacitive load effects, counteracts parasitic impedance, and maintains signal integrity. By integrating these functions into a single feedback loop, the patent reduces the need for separate compensation circuits, thereby limiting the increase in device complexity while achieving improved signal quality.
Solution Approach 2:
The positive feedback mechanism acts as an intermediary between the signal source and the electromechanical sensor, mediating the effects of capacitive loads and parasitics. This intermediary feedback loop isolates the sensor from the harmful effects of the circuit environment, improving signal quality without requiring complex modifications to either the source or sensor components themselves.
4Stability of the object's composition
If feedback loops are implemented to stabilize sensitivity, then measurement consistency improves, but circuit parasitics increase
Solution Approach 1:
The positive feedback circuit dynamically adjusts electrical parameters to compensate for the added parasitics from feedback components. By changing the feedback voltage magnitude and phase characteristics, the system maintains sensitivity consistency while minimizing the negative impact of additional circuit parasitics introduced by the feedback loop itself.
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 reduces signal distortion, improves sensitivity, and stabilizes the microphone's performance across varying acoustic pressures and environmental conditions, ensuring accurate and reliable acoustic sensing.
Implementation Method 1
Applying positive and negative feedback voltages via a voltage-to-voltage converter to an electromechanical sensor
Implementation Method 2
utilizing capacitive couplings and feedback loops
Data Source
AI summary
Applying positive and negative feedback voltages to an electromechanical sensor of a microphone utilizing a voltage-to-voltage converter to facilitate an improvement in sensitivity and reduction in distortion of the microphone is presented herein. A microphone comprises an electromechanical sensor comprising a capacitive sense element comprising a first sense node and a second sense node; and a voltage-to-voltage converter comprising an input, a first output, and a second output. The voltage-to-voltage converter forms, via a first capacitive coupling to the second sense node, a negative feedback loop between the first output of the voltage-to-voltage converter and the input of the voltage-to-voltage converter. The first sense node is electrically coupled to the input of the voltage-to-voltage converter, and the voltage-to-voltage converter forms, via a second capacitive coupling to the first sense node, a positive feedback loop between the second output of the voltage-to-voltage converter and the input of the voltage-to-voltage converter.