Linear Systems and the 1-D Fourier Transform

In this chapter we consider systems that receive a single input and produce a single output in response to the input. If the input and output are only able to assume fixed values that do not vary, then we consider that the system is static. In general, however, the input and output signals will vary with time t, in which case we must consider the system to be dynamic. We may thus represent such a system as a “black box.” We can probe this system only by examining the relationships between its inputs x(t) and its corresponding outputs y (t) (Fig. 2.1).