An Efficient Structure for the Design of Variable Fractional Delay Filters Based on the Windowing Method

A variable fractional delay (VFD) filter is presented that constitutes an efficient alternative to the usual Farrow structure. The filter is constructed by multiplying the signal to interpolate by a window with proper truncation properties, and then applying the sampling theorem. The resulting interpolator involves less arithmetic operations than the existing variants of the Farrow structure. Besides, if its coefficients are numerically optimized, its performance is close to that of the FIR equi-ripple filter. The final part of the correspondence includes a description of the VFD filter implementation corresponding to this interpolator.