Farrow structured variable fractional delay lagrange filters with improved midpoint response

This paper describes improvements in the Farrow structured variable fractional delay (FD) Lagrange interpolation. The main idea is to replace the first sub-filter of the Farrow structure by a sinc-interpolation filter of half a sample period to achieve a superior FD approximation in the vicinity of half a sample period. Its primary advantages over classical Farrow structured FD Lagrange interpolators are the lower level of mean-square-error (MSE) over the whole FD range and the reduced implementation cost. Design examples are included, illustrating an MSE reduction of 50% compared to a classical Farrow structured interpolator while the implementation cost is halved.