In the spectral parameter approximation (SPA) technique, the frequency response of a variable filter is approximated by the frequency response of the Farrow structure which is used to implement the SPA-based filter. In this paper, we propose a new approach in the time domain for the design of variable cutoff frequency finite impulse response filter using the SPA technique. We first design the practical filters which satisfy the given transition bandwidth, passband ripple, and stopband attenuation specifications and then approximate the coefficients of these filters by the impulse response of the Farrow structure. Approximation problem is solved using the least-squares technique. Various design examples are presented to illustrate the feasibility and the effectiveness of the proposed time-domain approach when the desired specifications are stringent. Interesting observations regarding the desired cutoff frequency range, the order, and the number of the sub-filters in the Farrow structure are also presented.
['Sumedh Dhabu', 'A. P. Vinod']
A New Time-Domain Approach for the Design of Variable FIR Filters Using the Spectral Parameter Approximation Technique