Digital Microphone Bias Control for Clipping-Free Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS microphones face signal distortion and reduced dynamic range due to absolute displacement limitations when encountering large acoustic signals, leading to undesirable clipping and decreased performance.
Innovation Solution
A digital microphone system comprising an acoustic sensor, bias generator, attenuators, amplifier, analog-to-digital converter, and controller that dynamically adjusts bias voltage and attenuation values to manage signal levels, preventing clipping and enhancing dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm displacement is increased to handle large acoustic signals, then the acoustic overload point is improved, but the diaphragm reaches its absolute displacement limitation causing signal clipping and distortion
Solution Approach 1:
The patent implements dynamic adjustment of the bias voltage applied to the diaphragm based on the detected signal level. When large acoustic signals are detected, the bias voltage is reduced to prevent the diaphragm from reaching its displacement limit, thereby avoiding clipping and distortion while maintaining high acoustic overload point capability
Solution Approach 2:
The patent changes the electrical parameter (bias voltage) to control the mechanical parameter (diaphragm displacement). By adjusting the bias voltage dynamically, the system optimizes the diaphragm's operating range to handle large acoustic signals without exceeding displacement limits, resolving the contradiction between handling large signals and avoiding distortion
2Measurement precision
If the sensitivity of the acoustic sensor is increased to improve signal detection, then the dynamic range is improved, but the microphone becomes more susceptible to clipping when handling large acoustic signals
Solution Approach 1:
The system dynamically adjusts the bias voltage to modulate the sensor's sensitivity in real-time. For large acoustic signals, the bias voltage is reduced to lower sensitivity and prevent clipping, while for small signals, the bias voltage is increased to maximize sensitivity and dynamic range, thus resolving the contradiction between sensitivity and dynamic range
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 effectively handles high acoustic overload points by adjusting sensitivity and attenuation, preventing signal distortion and increasing the dynamic range of the microphone, enabling it to process signals beyond conventional limits without clipping.
Implementation Method 1
The diaphragm vibrates in response to acoustic signals, which causes the capacitance between the diaphragm and the back plate to vary. Typically, the charge on the capacitor remains essentially constant during the vibration, and, thus, the voltage across the capacitor varies as the capacitance varies by incident acoustic signals.
Data Source
AI summary
A digital microphone is provided. The digital microphone includes an acoustic sensor, a bias generator, first and second attenuators, a buffer, an amplifier, an ADC, and a controller. The acoustic sensor transfers an acoustic signal to a voltage signal. The bias generator provides a bias voltage to the acoustic sensor. The first attenuator attenuates the voltage signal by a first attenuation value. The buffer buffers the voltage signal to generate a buffered voltage signal. The amplifier amplifies the buffered voltage signal to generate an amplified signal. The ADC converts the amplified signal to a data signal with a digital format. The second attenuator attenuates the data signal by a second attenuation value. The controller determines whether the amplified signal is larger than a reference value and adjusts the bias voltage and the first and second attenuation values of the first and second attenuators according to the result determined by the controller.