Microphone Filter Circuit for Low Group Delay Noise Suppression
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Solution Overview
Problem
Conventional microphone arrangements face challenges in achieving optimal group delay, which affects noise suppression and signal-to-noise ratio, especially in applications requiring significant ambient noise attenuation.
Innovation Solution
A circuit arrangement with a first filter that reduces group delay in the frequency range of 20 Hz to 10 kHz and allows minimal amplification above 20 kHz, and a second filter that selectively reduces high-frequency signals above 20 kHz to prevent modulator overload, while maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a low-pass filter is used to stabilize the arrangement and attenuate excessive increase in MEMS frequency response, then stability and frequency response control are improved, but group delay increases
Solution Approach 1:
The patent changes the filter design parameters by using a first filter with a cutoff frequency above 20 kHz that allows signal passage without amplification in the audio range (20 Hz to 10 kHz) while providing gain above 20 kHz. This parameter optimization reduces group delay compared to conventional low-pass filters while maintaining stability and frequency response control.
2Object-affected harmful factors
If ambient noise is significantly attenuated using a loudspeaker driven in anti-phase, then noise suppression is improved, but the group delay of the microphone arrangement becomes critical and affects performance
Solution Approach 1:
The patent optimizes the filter parameters to minimize group delay in the audio frequency range, enabling effective active noise cancellation. By adjusting the cutoff frequency and gain characteristics of the first filter, the system achieves low group delay that is critical for real-time noise suppression applications.
3Measurement precision
If high-frequency signals above 20 kHz are allowed to pass through the filter, then signal fidelity is improved, but modulator overload may occur
Solution Approach 1:
The patent applies local quality by designing the first filter to have different characteristics in different frequency ranges: in the audio range (20 Hz to 10 kHz), the filter allows signals to pass without amplification to maintain fidelity, while above 20 kHz, the filter provides gain greater than 0 dB to enhance high-frequency content. This localized frequency-dependent behavior optimizes both signal fidelity and prevents modulator overload by controlling amplitude in specific frequency bands.
Data Source
AI summary
In various embodiments, a circuit arrangement is provided. The circuit arrangement includes a sensor set up to provide an analogue signal, an analogue/digital converter set up to receive the analogue signal and to provide a first signal, and a first filter set up to receive a signal based on the first signal and to provide a second signal. The first filter is set up in such a manner that the second signal is allowed through without amplification or substantially without amplification in a frequency range of approximately 20 Hz to approximately 10 kHz, and the second signal has a gain of greater than 0 dB at least above a predefined frequency which is greater than approximately 20 kHz.