Delta modulation utilizing selectable piecewise linear waveform

Abstract

An analog-to-digital and digital-to-analog conversion system utilizes a modified delta modulation technique, together with generation of a number of linear waveforms forming a piecewise linear approximation of an analog signal to be encoded and decoded, to digitize the analog signal as a pulse train and subsequently retrieve an approximation of the original analog signal from the pulse train. The system comprises encoder and decoder sections of near identical structure. The encoder section includes compare circuits that compare the signal to be encoded to a reference signal and generate therefrom a binary indication of such comparisons. Successive ones of the binary indications form the digital pulse train containing information later used to approximate the analog signal being digitized. A predetermined number of such binary indications immediately preceding the present comparison are temporarily stored and used to generate one of a plurality of linear waveforms, successive ones of which form the reference signal. The decoder section is identical to the encoder section-except that it lacks the compare circuitry. The digital pulse train generated by the encoder is applied to the decoder and used to successively generate selected ones of the plurality of linear waveforms which are used to form the linear piecewise approximation of the original analog signal.