Silicon Microphone Digital Linearization for SNR-Distortion Tradeoff
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Solution Overview
Problem
Digital microphones face a trade-off between improving signal-to-noise ratio (SNR) and reducing distortion, where enhancing SNR typically increases distortion and vice versa, limiting the ability to independently improve both specifications.
Innovation Solution
A digital nonlinear compensation system that includes a nonlinear compensation component with a polynomial transfer function to linearize the digital signal, using open loop or closed loop feedback to adjust coefficients based on measured distortion, allowing for independent improvement of SNR and distortion without impacting each other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SNR is improved in traditional microphone design, then signal-to-noise ratio increases, but distortion levels increase
Solution Approach 1:
The patent replaces traditional analog signal processing with digital signal processing. An analog-to-digital converter (ADC) converts the analog microphone signal to digital, allowing digital filtering and processing to improve SNR without the analog noise and distortion limitations. The digital domain enables precise control of signal characteristics without the physical constraints of analog circuitry.
Solution Approach 2:
The patent applies inverse filtering and equalization techniques that dynamically adjust digital signal parameters to compensate for distortion. By analyzing the frequency response and applying corrective filters, the system reduces distortion across different operating conditions while maintaining improved SNR through digital processing advantages.
2Object-generated harmful factors
If linearity is improved in traditional microphone design, then distortion decreases, but signal-to-noise ratio decreases
Solution Approach 1:
The patent uses digital signal processing to achieve linearity improvement without the SNR penalty of traditional analog approaches. The ADC and digital filtering enable precise linearization through software-based equalization while maintaining high SNR through digital noise rejection capabilities.
Solution Approach 2:
The system performs preliminary characterization of the microphone's frequency response and distortion characteristics during calibration. This pre-measured data is stored and used to apply pre-computed correction filters during operation, enabling real-time distortion reduction without requiring complex real-time analysis that would compromise SNR.
3Object-generated harmful factors
If digital nonlinear compensation is applied, then distortion is reduced, but system complexity increases
Solution Approach 1:
The patent performs distortion characterization and filter design during an initial calibration phase, storing the results for use during normal operation. This pre-computation approach reduces real-time processing complexity while maintaining effective distortion compensation, as the system only needs to apply pre-determined correction filters rather than performing complex real-time analysis.
Solution Approach 2:
The system creates a digital model or copy of the microphone's distortion characteristics through calibration measurements. This model is then used to generate correction filters that compensate for distortion without requiring the physical microphone structure to be changed, separating the compensation function from the core sensing element.
Data Source
AI summary
A linearized system includes a nonlinear system configured for receiving an input signal; a digital nonlinear compensation component having an input coupled to an output of the nonlinear system, and having an output for generating an output signal; a low pass filter having an input coupled to the output of the digital nonlinear compensation component; a first summer having a first input configured for receiving a digital reference value and a second input coupled to an output of the low pass filter; and an error minimization component having an input coupled to an output of the first summer, and an output coupled to the digital nonlinear compensation component.