Chapter 2. Signal Processing and Modulation 2.1. The Nature of Electronic Signals

Static signals are by definition unchanging over a long period of time. Such signals are essentially DC levels, while quasi-static signals are those that change very slowly such as the drift on a sensor. 2.1.2. Periodic and Repetitive Signals Periodic signals are those that repeat themselves on a regular basis. These include sine, square and sawtooth waves. Their nature is such that each waveform is identical. Repetitive signals are periodic in nature, but the exact shape may change slightly with time. ECG signals are an example of this type. 2.1.3. Transient and Quasi Transient Signals Transient signals are either one time only signals while quasi-transient signals are those which are periodic but with a duration which is very short compared to the period of the waveform. Pulsed radar signals are good examples of these. 2.2. Sinusoidal Signals Most acoustic and electromagnetic sensors exploit the properties of sinusoidal signals In the time domain, such signals are constructed of sinusoidally varying voltages or currents constrained within wires, tfAtAtv ccccc πω 2coscos) ( = = , (2.1) where vc(t) – Signal