1.2 DETERMINISTIC SIGNALS AND SYSTEMS
In engineering programs, students usually learn about signals and systems first in the time domain and then in the frequency domain. The focus is on deterministic signals such as those illustrated in Figure 1.19.
Figure 1.19 Examples of deterministic signals: sinusoid 
, exponential 
, and step 
where u(t) is the unit-step function.
1.2.1 Continuous Time
Nonrandom signal x(t) is a function of continuous time 
. Consider the sinusoidal signal
(1.15) 
shown in Figure 1.19 for 
where u(t) is the unit-step (Heaviside) function (see Appendix B). Radian frequency ω (radians/second) is related to ordinary frequency f in hertz (Hz) according to 
. For a particular ...
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