Quantizing Noise of DELTA M/PCM Encoders
01 February 1973
A new approach to digital encoding of continuous waveforms employs digital hardware to unite the economy of single-integration delta modulation (AM) with the efficiency of pulse code modulation (PCM). A finite impulse response digital filter suppresses the granular noise component of the AM representation of a continuous signal, and a word generator truncates the binary coded filter output to produce P C M code words of desired length. This encoding method controls the precision of the digital code by means of the AM speed and the filter order rather than with the resolution of the multibit quantizer that appears in conventional P C M encoders. This is a desirable substitution in view of current technology in which the cost of high-speed digital circuitry is rapidly declining. This method of A M / P C M encoding, which was originally proposed by Goodman, 1 has been applied to speech encoding by Freeny, et al.,2-3 183 184 T H E B E L L S Y S T E M TECHNICAL J O U R N A L , F E B R U A R Y 197.3