Two-bit instantaneously adaptive delta modulation for p.c.m. encoding

A two-bit instantaneously adaptive delta modulator intended for application as the input stage of a code converter is presented. Its step adaptation algorithm is derived from that used in high information delta modulation (HIDM). The improvement in performance relative to the HIDM system is gained by its ability to reduce overshoots and respond faster to signal variations. A hardware model that allows the comparison between these delta modulators is described and results of measurements on narrow-band noise and sinewave input signals are presented. Two possible structures to generate p.c.m. signals by code conversion are described and computer simulation results presented for one of them.