An algorithm for the design of multiplierless approximately linear-phase lattice-wave digital filters

This paper describes an efficient algorithm for the design of multiplierless approximately linear-phase lattice wave digital (LWD) filters (parallel connections of two all-pass filters). The coefficient optimization is performed in two basic steps. First, a nonlinear optimization algorithm is used for determining a parameter space of the infinite-precision coefficients including the feasible space where the filter meets the given amplitude and phase specifications. The second step involves finding the filter parameters in this space such that the resulting filter meets the given criteria with the simplest coefficient representation forms. The proposed algorithm guarantees that the optimum multiplierless finite-wordlength solution can be found. This is illustrated by means of an example.