Silicon Microphone Nonlinearity Compensation for Low-Distortion Output
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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 that enhance SNR typically increase distortion and vice versa, limiting overall system performance.
Innovation Solution
Incorporating a nonlinear compensation component in the digital signal processing path, which can be configured in open loop or closed loop configurations, to correct non-linearities generated by the MEMS device and ADC, using polynomial functions or error feedback structures to linearize the digital output signal without impacting SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If solutions are implemented to improve signal-to-noise ratio (SNR), then SNR is improved, but distortion levels increase
Solution Approach 1:
The patent segments the distortion compensation function into separate digital filter components (first digital filter for even-order nonlinearities, second digital filter for odd-order nonlinearities) that process the signal independently after ADC conversion. This allows distortion correction without affecting the analog SNR improvement mechanisms
Solution Approach 2:
The patent introduces digital filter components as intermediary elements between the ADC and output stages. These filters act as mediators that selectively remove distortion components (even-order and odd-order nonlinearities) from the digital signal without impacting the analog SNR improvement achieved through earlier design choices
2Object-generated harmful factors
If solutions are implemented to improve linearity and reduce distortion, then distortion is reduced, but signal-to-noise ratio (SNR) decreases
Solution Approach 1:
The patent replaces traditional analog linearization mechanisms with digital signal processing approaches. By using digital filter components to compensate for nonlinearities in the digital domain after ADC conversion, the system achieves distortion reduction without the SNR penalties associated with analog linearization techniques
Solution Approach 2:
The patent changes the operating domain from analog to digital for the distortion compensation function. By implementing even-order and odd-order nonlinearities compensation through digital filters rather than analog circuitry, the system achieves improved linearity while maintaining the SNR benefits of digital processing
3Reliability
If traditional microphone system designs are used, then either SNR or distortion can be improved, but both specifications cannot be improved simultaneously
Solution Approach 1:
The patent merges the distortion compensation function with the existing digital signal processing chain by integrating even-order and odd-order nonlinearities compensation into the digital filter stages. This combination allows simultaneous improvement of both SNR and distortion specifications without requiring entirely separate processing paths
Solution Approach 2:
The patent makes the digital filter components multi-functional by designing them to simultaneously perform noise filtering and distortion compensation. The first and second digital filter components serve dual purposes of signal conditioning and non-linearity correction, improving overall system performance without proportionally increasing complexity
Data Source
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 blocker component; and a nonlinear compensation component coupled to the digital low pass filter for providing a digital output signal.