Gate level optimisation of primitive operator digital filters using a carry save decomposition

This paper introduces a method for optimising digital filter realisations at the gate level. The method is based on a derivative of the primitive operator approach of Bull and Horrocks which is extended using a carry-save decomposition of the primitive operator graph. This facilitates the generation of a set of Boolean expressions for the multiply-accumulate section of the filter which can be minimised using standard sum of products or Reed Muller techniques. The technique is fully described and results are presented for a representative range of FIR filters. Savings of up to 83% are obtained for sum-of-products minimisation when compared to a CSD coded hard-wired multiplier solution. Initial results suggest further improvements in excess of 20% for the Reed Muller case