3.1 Types of Signals

A fundamental element of any communication system is an electronic signal which is used to represent and exchange information between source and destination.

Signals can have different types:

		Analog, digital
		Periodic and aperiodic

3.1 Types of Signals

Analog VS Digital Signals

Signals can be of two types:

Analog signal: in which information is represented as a continuous signal with its intensity continuously changing over time without any breaks (see Figure 3.1).

		An analog signal represents an infinite number of values.
		An example of an analog signal is sound or human speech. Human sound causes a continuous vibration in air with a vibration intensity proportional to the sound volume (signal amplitude).

Digital signal: Information is represented in binary form (0s and 1s) with signal intensity varying discretely between different values (see Figure 3.2).

		A digital signal can only represent a limited number of values.
		An example of a digital signal could be a computer signal which varies in voltage to represent two discrete states 0 and 1.

3.1 Types of Signals

3.1 Types of Signals

3.1 Types of Signals

Periodic VS Aperiodic Signals

Another classification of signal types is based on whether the signal is periodic or aperiodic.

A signal is periodic if it repeats every fixed time period.

In aperiodic signals, there is no repeated pattern over time.

The signal shown in Figure 3.1 is an example of aperiodic signal.

A sine wave, as shown in Figure 3.3, is a simple periodic analog signal. Note the repeated pattern in the signal every time period T.

Another example of a periodic digital signal is shown in Figure 3.4 which illustrates a square wave with repeats every T seconds.

3.1 Types of Signals

3.1 Types of Signals