Modulation

Modulation may be defined as a process by which some characteristic of a signal known as carrier is varied according to the instantaneous value of another signal known as modulating signal. The signals containing the intelligence or information to be transmitted are called modulating signals or baseband signals. The carrier frequency is greater than the modulating frequencies and the signal result from the process of modulation is known as modulated signals.

Modulation may be of two types; 1) Continuous wave modulation (CW) and 2) Pulse modulation. If the carrier waveform is continuous in nature then the modulation process is called CW modulation and if the carrier is a pulse type waveform, then the modulation is called Pulse modulation.

Examples of CW modulation – amplitude modulation and angle modulation

Examples of pulse modulation – Pulse amplitude modulation (PAM), Pulse width modulation (PWM), and Pulse code modulation (PCM)