Question

How is modulation done in a full carrier AM (time domain) circuit? Do we just add the carrier signal to the modulating signals?

Answer 1

Modulation:

Modulation is a process through which the information is added to an electrical signal to be transmitted over a telecommunication or a electronic medium.

It is a process of changing the characteristics of the carrier wave with respect to the message signal.

Amplitude modulation:

Amplitude moulation is a process of changing the amplitude of carrier signal with respect to the amplitude of the message signal.

By the above statement we can say that we are having 2 inputs like:

• Message signal:

The message signal is the information.

• Carrier signal:

The carrier signal is used to carry the information given in the message signal.

The message signal and the carrier signal are sent to the modulator and then we get the modulated signal.

• The message signal have very low frequency and is easily effected by noise and it cannot travel more distance so we add carrier signal to the message signal which is having high frequency when compared to message signal.

consider,

Message signal=x(t)

Carrier signal=c(t)

Modulated signal  

Message signal is also called as base band signal.

Where 'm' is a modulation index

substitute in s(t)

In the output of the amplitude modulation the frequency and phase of the carrier wave is constant.

Based on the 'm' value we have 3 types of modulated outputs.

• Under modulation(m<1)

• Critical modulation(m=1)

• Over modulation(m>1)

Thus, is the AM in time domain.This not only depends on the carrier signal but also many factors.