The Application of Delta Modulation to Analog-to-PCM Encoding

This paper describes a pulse code modulation (PCM) encoder that employs a delta modulator as the analog-to-digital converter. A tapped binary shift register and an up-down counter cause delta modulation signals to be converted to a uniformly quantized PCM format. When tap weights are optimized with respect to a minimum mean square error criterion, the number of shift register stages necessary to obtain a fixed level of output quantizing noise varies inversely with delta modulation sampling rate. Because the tap weights may be rounded to a modest number of binary places, the arithmetic operations are simple to implement. A significant portion of the delta modulation-to-PCM converter may be time shared among several signals.