Digital Filter Chain Gain Merging for Higher Signal-to-Noise Ratio
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Solution Overview
Problem
Existing digital filter chains, particularly those including IIR filter elements, face challenges in achieving optimal signal-to-noise ratio (SNR) and efficient bandwidth utilization due to quantization errors and unnecessary bitshift operations.
Innovation Solution
The implementation of a common gain element in filter chains, which combines adjacent opposite bitshifts to minimize quantization error and increase precision, along with the use of a programmable bitwidth extension value to optimize bitwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate gain elements are used for each filter stage, then individual gain control is achieved, but quantization error increases and SNR deteriorates
Solution Approach 1:
The patent combines multiple separate gain elements into a single common gain element that applies the same gain factor to multiple filter stages simultaneously. This merging approach reduces the total number of gain elements, minimizes quantization error from multiple gain operations, and improves SNR while maintaining individual stage control through the unified gain parameter.
Solution Approach 2:
The common gain element serves multiple filter stages universally, performing the gain function for each stage without requiring separate dedicated gain elements. This multi-functional approach allows a single gain element to control the gain for multiple IIR and FIR filter stages, reducing complexity and quantization error while maintaining flexibility.
2Measurement precision
If bitwidth extension is applied, then precision increases, but computational overhead increases
Solution Approach 1:
The patent applies bitwidth extension selectively and partially, extending the bitwidth only when necessary to maintain precision during critical operations in the filter chain. Rather than consistently using maximum bitwidth, the extension is applied judiciously to balance precision requirements with computational efficiency, avoiding excessive processing overhead while preventing precision loss.
Data Source
AI summary
Methods and apparatus are provided for adapting gain elements in digital filter chains. In one example, a digital filter chain includes a first digital filter and a second digital filter having an input coupled to an output of the first digital filter. A common gain is applied to signal samples passing between the first digital filter and the second digital filter, the common gain corresponding to a product of an output gain associated with the first digital filter and an input gain associated with the second digital filter. In another example, a digital filter includes an adjustable input gain element and an adjustable output gain element. The adjustable input gain element is configured to apply a gain value to an input signal sample, the gain value comprising a resultant difference of a bitshift configured for the digital filter and a bitwidth extension value. The adjustable output gain element is configured to apply an opposite of the gain value to an output signal sample.