An ADPCM realization of nonrecursive digital filters

A realization of nonrecursive digital filters using adaptive differential pulse-code modulation (ADPCM) as the analog-to-digital conversion scheme is presented. Output samples are computed by a sequence of read-only memory (ROM) lookups, shifts, and additions, thereby eliminating multipliers from the filter structure. Such ADPCM filters can typically operate three times faster than comparable PCM filters realized using high-speed hardware multipliers, with power consumption reduced by 25 percent. Equations are derived for computation time per output sample, signal-to-noise ratio, and coefficient accuracy necessary to achieve the optimum predicted performance. Computer simulation results agree well with theoretical predictions.