Silicon Microphone Nonlinear Compensation for SNR and Distortion

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Solution Overview

Problem

Digital microphones face a trade-off between improving signal-to-noise ratio (SNR) and reducing distortion, as solutions to enhance one typically degrade the other, leading to suboptimal performance in both specifications.

Innovation Solution

Incorporating a nonlinear compensation component in the digital signal processing path, utilizing either open loop or closed loop feedback structures, to correct non-linearities generated by the MEMS device and ADC, allowing for independent improvement of SNR and distortion without compromising either.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional microphone design solutions are applied to improve signal-to-noise ratio, then SNR is improved, but distortion levels increase

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddistortion levels

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the digital output signal is fed back through a nonlinear compensation component that applies the inverse of the measured nonlinear transfer function. This closed-loop feedback continuously corrects distortion artifacts generated by the ADC and MEMS device, allowing SNR improvement without the traditional trade-off of increased distortion

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the parameter of the transfer function by applying a nonlinear compensation function that is the inverse of the measured nonlinear transfer function. This parameter transformation linearizes the overall system response, enabling simultaneous improvement of both SNR and distortion performance by transforming the nonlinear relationship into a linear one

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If traditional microphone design solutions are applied to improve linearity, then distortion is reduced, but signal-to-noise ratio decreases

Engineering Contradiction:

ImprovedistortionVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

The feedback loop with nonlinear compensation allows the system to maintain linearity while preserving signal integrity. By continuously correcting distortion through feedback rather than pre-distortion or linearization techniques, the system achieves low distortion without the SNR penalty associated with traditional linearization methods

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces traditional mechanical or analog linearization techniques with a digital nonlinear compensation approach. By using digital signal processing to apply the inverse nonlinear transfer function, the system achieves linearity improvement without the SNR degradation that would result from analog processing or mechanical adjustments

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12170874B2Digital non-linearity compensation in a silicon microphone

Publication Date: 2024.12.17 INFINEON TECHNOLOGIES AG

AI summary

According to an embodiment, a digital microphone includes an analog-to-digital converter (ADC) for receiving an analog input signal; a DC blocker component coupled to the ADC; a digital low pass filter coupled to the DC block component; and a nonlinear compensation component coupled to the digital low pass filter for providing a digital output signal.