ABSTRACT
In this chapter, the authors show how to describe and model discrete systems. The systems that they will study will be primarily derived from continuous systems appropriately digitized. They develop approaches such that the discrete systems approximate the continuous ones to a degree that is acceptable for practical applications. A discrete signal sequence may arise by pulse sampling a continuous-time excitation function, usually at uniform time intervals. A group of such connected discrete elements and adderswith appropriate pick-off points constitute a digital system. System consisting of discrete-time elements with a discrete-time input signal sequence is described by a difference equation. For linear time-invariant discrete systems, causality, linearity, and stability are defined in a manner analogous to their definition in continuous systems. As in continuous systems, the convolution of discrete sequences obeys the commutative and associative properties.
