Digital Microphone Decimation Filter With Parallel FIR-Allpass Paths
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Solution Overview
Problem
Existing digital microphone decimation filters are inefficient due to their reliance on brute force methods and complex filter structures, which result in increased computational complexity and resource requirements.
Innovation Solution
A digital microphone decimation filter architecture utilizing two parallel filter paths, each comprising a shorter FIR filter followed by allpass stages implemented with IIR filters, operating at the output sample rate, which effectively cancels out-of-band noise without the need for multipliers and intermediate sample rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single FIR filter is used for decimation filtering, then filtering accuracy is improved, but computational complexity and resource requirements increase significantly
Solution Approach 1:
The patent divides the decimation filtering process into two separate parallel paths, each handling a portion of the frequency spectrum. Path 0 processes frequencies from 0 to Nyquist/2, while Path 1 processes frequencies from Nyquist/2 to Nyquist. This segmentation allows each path to use a shorter, less complex filter while achieving the same overall filtering accuracy as a single long filter would provide.
Solution Approach 2:
The patent transitions from a single-dimensional filtering approach (one long FIR filter) to a two-dimensional parallel processing architecture. By introducing a second processing path and utilizing the frequency domain dimension, the system achieves equivalent filtering performance with reduced computational complexity in each individual path.
2Measurement precision
If a single FIR filter is used for decimation filtering, then filtering accuracy is improved, but resource usage increases
Solution Approach 1:
The patent segments the filtering task into two parallel paths, each with its own shorter FIR filter and IIR filter. This segmentation reduces the number of coefficients and computational resources required in each path compared to a single long FIR filter, while maintaining overall filtering accuracy through the combined output of both paths.
Solution Approach 2:
The patent combines the outputs of two parallel filtering paths to achieve the final decimated signal. By merging the results from Path 0 and Path 1, the system achieves equivalent filtering accuracy to a single long filter while using fewer resources overall, as each individual path requires less computational resources.
3Reliability
If traditional decimation filtering is used, then filtering performance is achieved, but the system requires multipliers and intermediate sample rates
Solution Approach 1:
The patent replaces the traditional mechanical multiplication operation with an addition-based FIR filter implementation. By using only addition operations in the FIR filter stage and eliminating the need for multipliers, the system achieves the same filtering performance with simpler, more efficient hardware that requires no intermediate sample rates.
Data Source
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AI summary
A new and more efficient filtering system (e.g., digital microphone decimation filter architecture system) is described. A key to this architecture is the use of two parallel filter paths. Each path operates at the output sample rate, and comprises a shorter FIR filter followed by a series of allpass stages (e.g., implementing IIR filters). The FIR filter is designed to remove all but the last octave of out-of-band noise. The allpass stages are designed such that when the two paths are summed together, the out-of-band noise for the final octave cancels out, leaving only the desired sign