Variable fractional delay filter with sub-expression coefficients

Abstract

Variable fractional delay (VFD) filters are useful for various signal processing and communication applications with frequency characteristics such as fractional delays to be varied online. In this paper, we investigate the design of VFD filters with discrete coefficients as a means of achieving low complexity and efficient hardware implementation. The optimization problem with minimax criterion is formulated as a mixed integer programming problem with a non-linear cost function and continuous constraints. An efficient optimization procedure is proposed to tackle the design problem that includes a combination of the branch and bound method and an adaptive scheme for discretization. Design examples are given to demonstrate the effectiveness of the proposed algorithm.