Polyphase FIR Lattice for Lower-Complexity Rate Conversion
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Solution Overview
Problem
Current multirate digital filter systems face inefficiencies in sampling rate conversion due to high computational complexity, particularly in polyphase architectures, where subfilters with antisymmetric coefficients require redundant calculations.
Innovation Solution
The proposed solution involves reconfiguring pairs of subfilters with antisymmetric coefficients into a lattice structure with adders and feedlines, allowing for shared calculations and reduced complexity by transforming antisymmetric pairs into symmetric coefficients, thereby simplifying the polyphase architecture for both interpolators and decimators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polyphase architecture with antisymmetric coefficients is used, then sampling rate conversion can be performed, but computational complexity is high due to redundant calculations
Solution Approach 1:
The patent combines pairs of antisymmetric subfilters into a single lattice structure with symmetric coefficients. By merging two subfilters (h_m and h_{R-m}) into one lattice unit, the number of separate filter computations is reduced, eliminating redundant calculations while maintaining the same filtering functionality.
Solution Approach 2:
The patent transforms antisymmetric coefficients into symmetric coefficients through the lattice structure. The lattice uses symmetric coefficient pairs (a_k, b_k) that are derived from the original antisymmetric coefficients, allowing the system to exploit symmetry properties for computational efficiency while handling antisymmetric signal characteristics.
2Adaptability or versatility
If multiple subfilters with antisymmetric coefficients are used in polyphase architecture, then interpolation and decimation functions are achieved, but the number of multiplications and additions increases
Solution Approach 1:
The lattice structure serves multiple functions simultaneously: it performs both interpolation and decimation operations, handles both symmetric and antisymmetric coefficient cases, and can be applied to any polyphase component. This multi-functionality reduces the need for separate dedicated structures for different operations.
Solution Approach 2:
The patent merges the functionality of multiple antisymmetric subfilters into a single lattice structure. The lattice combines the operations of subfilter h_m and subfilter h_{R-m} into one unified computational unit, reducing the total number of multiplications and additions required while maintaining both interpolation and decimation capabilities.
Data Source
AI summary
Apparatuses (and methods of manufacturing same), systems, and methods concerning polyphase digital filters are described. In one aspect, an apparatus is provided, including at least one pair of subfilters, each having symmetric coefficients, and a lattice comprising two adders and feedlines corresponding to each of the at least one pair of subfilters, each having symmetric coefficients. In one aspect, the apparatus is a polyphase finite impulse response (FIR) digital filter, including an interpolator and a decimator, where each of the interpolator and the decimator have at least one pair of subfilters, each having symmetric coefficients, and a lattice comprising two adders and feedlines corresponding to each of the at least one pair of subfilters, each having symmetric coefficients.