Multi-Stage Audio Decimator With Compact FIR Coefficient Tables
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Solution Overview
Problem
Mobile devices face challenges in reducing power consumption of signal processing circuitry, such as decimators, which are essential for processing audio signals, leading to increased energy usage.
Innovation Solution
Implementing a multi-stage decimator with finite impulse response (FIR) filters that utilize coefficient tables with non-redundant values and sign inversion or zeroing to reduce power consumption, allowing for efficient decimation of audio samples while minimizing the size of coefficient tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a decimator utilizes a finite impulse response (FIR) filter to filter the input samples, then the decimation process can be performed effectively, but the power consumption increases
Solution Approach 1:
The decimation process is divided into multiple stages, where each stage performs partial decimation. The first stage decimates by a factor of M1 and the second stage decimates by a factor of M2, where the total decimation factor is M1×M2. This segmentation allows each stage to use a shorter FIR filter with fewer coefficients, reducing the computational complexity and power consumption compared to a single-stage decimator with a long filter.
Solution Approach 2:
The patent employs dynamic coefficient tables that are selectively accessed based on the current input sample values. Instead of always computing all filter coefficients, the system uses pre-computed coefficient tables that are indexed by the current sample values, allowing rapid retrieval of the appropriate coefficients. This dynamic approach reduces the real-time computational burden and power consumption while maintaining filter quality.
2Speed
If coefficient tables store all possible coefficient combinations, then lookup operations can be performed quickly, but the table size increases
Solution Approach 1:
The patent extracts only the essential and non-redundant coefficient values from the full set of possible coefficient combinations. By analyzing the symmetry and redundancy in FIR filter coefficients, the system stores only the unique coefficient values in the coefficient tables, significantly reducing table size while maintaining the ability to perform rapid lookups for all required coefficient combinations.
Solution Approach 2:
The system changes the representation parameters of the coefficient tables by organizing them according to the specific decimation factors and filter lengths used in each stage. This parameter optimization allows the tables to be compact yet fully functional for the intended application, balancing table size with lookup efficiency.
Data Source
AI summary
Systems, apparatuses, and methods for implementing a low power decimator. A decimator may receive a plurality of input samples from a digital microphone. The decimator may include one or more coefficient tables for storing values combining two or more filter coefficients for filtering the received samples. The decimator may utilize a concatenation of multiple samples to perform a lookup of a corresponding coefficient table. The coefficient tables may store only the necessary non-redundant values for all coefficient combinations which can be applied to the multiple samples. The result of the lookup of the coefficient table may have its sign inverted or be zeroed based on the values of the multiple samples.