Modulation

Modulation is one of the important terms in basic communication systems.
Modulation is defined as "Changing the characteristics of a signal",called carrier which is varied in accordance with the instantaneous value of another signal called Modulating signal.
The signal resulting from the process of modulation is called modulated signal.The modulation is the process of placing the message signal over the carrier signal,which is useful for suitable transmission.

Types of Modulation

Modulation can be divided into two basic categories :

i) Pulse Modulation
ii)Continuous wave modulation

i)Pulse Modulation
Modulation is the process of changing the characteristics of the signal according to the modulating signal.When the carrier wave is a pulse type wave form,the modulation is known as pulse modulation.

Examples of pulse modulation are pulse amplitude modulation,pulse width modulation and pulse position modulation.

ii)Continuous Wave Modulation
When the carrier signal is in the form of continuous wave,this type of modulation is known as continuous wave modulation.

Examples are amplitude modulation, angle modulation and frequency modulation.