Synthesis and performance of a new class of implementation for high-order recursive digital filters

The authors investigate a new class of approaches to the synthesis of high-order recursive digital filters. These are all characterised by partitioning the overall filter into a set of parallel subfilters, each of which is of moderate order. The subfilters may be any of the classical implementations: direct form, parallel, cascade or lattice. The authors investigate cascade and lattice implementation of the subfilters. The investigation includes selection of the number of subfilters to use, how to derive their coefficients and theoretical noise calculations. This is supported by simulation testing of a variety of real and synthetic filters using maximal length binary sequences (MLS) as input as this provides information on both the linear and nonlinear errors involved. It is found that particularly when filter order is 50 or more, the new structures have reduced quantisation noise and improved tolerance to quantisation than their classical counterparts