Fractional Order Beamformer for Flexible Microphone Arrays
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Solution Overview
Problem
Conventional microphone arrays face challenges in maintaining desirable directivity factor (DF) while minimizing white noise gain (WNG), especially at low frequencies, due to the inverse frequency response of beamformers, which affects noise reduction and speech enhancement in voice communications and human-machine interfaces.
Innovation Solution
The implementation of a flexible differential microphone array (FDMA) with a fractional order beamformer that generates a continuous compromise between integer and omnidirectional order beampatterns, using Jacobi-Anger expansion and minimum-norm methods to determine the fractional order based on target DF or WNG values, allowing for robustness and performance optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional beamformers are used to achieve directional signal transmission, then directivity factor is improved, but white noise gain increases causing excessive noise sensitivity
Solution Approach 1:
The patent applies parameter changes by introducing a fractional order parameter α that continuously adjusts the beamformer characteristics between omnidirectional (α=0) and directional (α>0) modes. This allows dynamic optimization of the trade-off between directivity factor and white noise gain by tuning the fractional order parameter based on operating conditions, thereby resolving the contradiction between achieving high directivity and minimizing noise sensitivity.
Solution Approach 2:
The patent implements dynamics by making the beamformer order dynamic rather than fixed. The fractional order beamformer adapts its characteristics in real-time based on the fractional order parameter, enabling the system to dynamically balance between directivity enhancement and noise suppression according to environmental conditions and signal requirements.
2Measurement precision
If higher order beamformers are used to enhance directivity, then directional response is improved, but robustness decreases due to increased noise amplification
Solution Approach 1:
The patent uses parameter changes by introducing the fractional order parameter to continuously adjust the beamformer order. This allows the system to select an optimal operating point that achieves sufficient directional response while maintaining robustness against noise amplification, avoiding the extreme of high-order integer beamformers that sacrifice robustness for directivity.
3Ease of manufacture
If integer order beamformers are used, then design simplicity is maintained, but performance flexibility is limited
Solution Approach 1:
The patent extends the discrete integer order parameter to a continuous fractional order parameter, maintaining the simplicity of parameter-based design while dramatically increasing performance flexibility. The fractional order parameter can be continuously adjusted to achieve optimal performance for different applications, bridging the gap between simple integer designs and complex adaptive systems.
Data Source
AI summary
A beamformer, for a differential microphone array (DMA) including a number M of microphones, is constructed based on a specified target directivity factor (DF) value for the DMA. An N order beampattern is generated for the DMA, wherein N is an integer and a first DF value corresponding to the N order beampattern is greater than the target DF value. An N−1 order beampattern is generated for the DMA, wherein a second DF value corresponding to the N−1 order beampattern is greater than the target DF value. A fractional order beampattern is generated for the DMA, wherein a third DF value corresponding to the fractional order beampattern matches the target DF value and the fractional order beampattern comprises a first fractional contribution from the N order beampattern and a second fractional contribution from the N−1 order beampattern.