Engineering Tutorials

The basic idea here is to superimpose the message signal in analog form on a carrier which is a sinusoid of the form

A cos (ω_ct + )

There are three quantities that can be varied in proportion to the modulating signal: the amplitude, the phase, and frequency. The first scheme is called Amplitude Modulation and the second two are called Angle Modulation schemes.

Fig.1.2 Types of Analog Modulation

There are two types of analog modulation.

1. Amplitude Modulation

2. Angle Modulation.

Angle modulation are also have two different types.

1. Frequency Modulation(FM)

2. Phase Modulation(PM)

In amplitude modulation, the message signal will be present in the amplitude of the transmitted signal.

Analog modulation is non linear modulation and requires high bandwidth and also have good performance in the presence of noise .

In frequency modulation, the message signal will be present in the instantaneous frequency.

In phase modulation, the message signal will be present in the phase.

In quadrature amplitude modulation, the message will be present in both the amplitude and the phase .