Digital Signal Processing

EE January 1987 DIGITAL SIGNAL PROCESSING Compact disc players have been with us for some time. Digital television receivers are becoming commonplace. These, and other apparatus, have an important aspect in common: digital signal processing. But what is really involved in this? Digital circuits only respond to discrete values of input voltage and produce discrete values of output voltage. Usually, these circuits operate between two discrete voltage levels, i.e., high and low (logic) levels. It is therefore clear that before such a circuit can operate the analogue signals have to be converted into digital (= binary) signals. Some fundamentals Fig. 1 shows the basic set-up of a digital processing circuit. The incoming analogue signals at X are digitized, in an analogue-to- digital (A-D) converter, pro- cessed in a (digital) signal pro- cessor, and then reconverted into analogue signals in a D-A circuit. The A-D converter produces a stream of binary values by quantization. In this me...