5.1 Introduction

Although the world that we live in is analogue in nature, in electronic circuits and systems digital circuits are widely used and can be designed to perform many actions that were originally undertaken in analogue circuitry, as well as providing potential benefits over analogue circuit operation. The electronic system shown in Figure 5.1 will perform its operations on signals that are either analogue or digital in nature, using either analogue or digital electronic circuits [1]. Hence, a signal may be one of two types: analogue or digital.

Figure 5.1: Electronic system block diagram

An analogue signal is a continuous or discrete-time signal with an amplitude that is continuous in value between a lower and upper limit, but may be either a continuous-time or discrete-time signal.

A digital signal is a continuous or discrete-time signal with discrete values between a lower and upper limit. These discrete values are represented by numerical values and are suitable for digital signal processing. If the discrete-time signal has been derived from a continuous-time signal by sampling, then the sampled signal is converted into a digital signal by quantization: quantization produces a finite number of values from a continuous amplitude signal. It is common to use the binary number (i.e., two values, 0 or 1) system to represent a number digitally.

In the digital domain, the choice of implementation technology is essentially whether to use dedicated- (and fixed-) functionality digital logic, to use a software-programmed processor based system (microprocessor, ?P;