Sparse CIC Filter Coefficients for Higher Stopband Attenuation
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Solution Overview
Problem
Conventional Cascaded-Integrator-Comb (CIC) filters face limitations in worst-case stopband attenuation due to zeros being located at the same position, requiring increased filter order to improve performance, which leads to increased area, power consumption, and computational complexity.
Innovation Solution
A sparse CIC filter structure is introduced, incorporating a finite impulse response (FIR) filter with a sparse set of time-varying coefficients and a decimation stage, allowing for improved frequency response without increasing the filter order by using a time-varying multiplier and integrate&dump circuit, and optimizing coefficients to reduce hardware complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the filter order is increased to improve stopband attenuation, then the frequency response performance is improved, but the area, power consumption, and computational complexity increase
Solution Approach 1:
The patent applies dynamics by making the filter coefficients time-varying rather than static. The coefficients are updated dynamically based on the input signal characteristics, allowing the filter to adapt its response. This enables a lower-order filter to achieve the stopband attenuation of higher-order filters by optimizing coefficients in real-time based on signal conditions.
Solution Approach 2:
The patent changes the parameters of the filter by introducing time-varying coefficients that are adjusted based on signal statistics. Instead of fixing the filter order to achieve performance, the patent varies the coefficient parameters dynamically, allowing a lower-order structure to achieve equivalent or superior stopband attenuation through parameter optimization.
2Manufacturing precision
If the filter order is increased to improve stopband attenuation, then the frequency response performance is improved, but the power consumption increases
Solution Approach 1:
The dynamic coefficient adaptation allows the filter to achieve high stopband attenuation with fewer computational operations. By making coefficients time-varying and signal-dependent, the patent reduces the need for additional filter stages, thereby reducing the number of multiply-accumulate operations and associated power consumption while maintaining or improving attenuation performance.
Solution Approach 2:
By changing the coefficient parameters dynamically based on signal characteristics, the patent enables a lower-order filter to achieve the same stopband attenuation as higher-order filters. This parameter optimization reduces the computational burden and power consumption while achieving the desired frequency response performance.
3Manufacturing precision
If the filter order is increased to improve stopband attenuation, then the frequency response performance is improved, but the computational complexity increases
Solution Approach 1:
The patent reduces computational complexity by using dynamic coefficients that adapt to signal characteristics rather than requiring complex higher-order filter structures. The time-varying coefficients are computed based on simple signal statistics, avoiding the need for multiple filter stages and reducing the overall computational burden while achieving equivalent stopband attenuation.
Solution Approach 2:
The patent changes the approach from increasing filter order to optimizing coefficient parameters dynamically. This parameter-based solution achieves high stopband attenuation with fewer computational operations by adapting coefficients to signal conditions, thereby reducing the computational complexity compared to fixed high-order filter designs.
4Manufacturing precision
If the filter order is increased to improve stopband attenuation, then the frequency response performance is improved, but the area on chip increases
Solution Approach 1:
The dynamic coefficient adaptation enables a compact lower-order filter structure to achieve the stopband attenuation of larger higher-order filters. By making coefficients time-varying and signal-dependent, the patent reduces the number of integrators and comb filters needed, thereby reducing the chip area while maintaining or improving frequency response performance.
Solution Approach 2:
The patent achieves high stopband attenuation with reduced chip area by optimizing coefficient parameters dynamically rather than increasing filter order. This parameter-based approach allows a compact filter structure to achieve equivalent performance to larger filters by adapting coefficients to signal characteristics, thereby reducing the hardware resources required.
Data Source
AI summary
In a cascaded integrator comb (CIC) filter, a time-varying gain is added before the last integrating stage transforming its sub optimal boxcar impulse response into an FIR filter of arbitrary length. Make the coefficients sparse and taking them from a set of small integers leads to an efficient hardware implementation that does not compromise any of the essential CIC filter characteristics especially the overflow handling. The proposed sparse CIC structure can improve the worst case stop band attenuation by as much as 10 dB while occupying 77% of the chip area and consuming 30% less power compared to a standard a 5th order CIC filter, and reducing the overall bit growth of the filter and the amount of high rate operations. Design examples are given illustrating the advantages and flexibility of the proposed structure.