Top

Modulation

Communication is the basic asset of mankind through which he can exchange the information. It gives the idea of what is going around us. We communicate with many people in our daily life. We also need the entertainment medias in our day to day life like TV, radio, browsing, News paper etc which also acts as a source of Communication.
Electronic communication includes TV, radio, Internet etc. Here we need to transmit the information bearing signal from one place to another. To do this we need to strengthen the signal. So that the signal travels for long distances. This is what is called Modulation. Let us study more about the Modulation in this section.

Communication Systems

Communication is the basic process of exchanging information. The basic components of electronic communication system are:
1. Transmitter
2. Communication channel
A Transmitter is a collection of electronic circuits designed to convert the information into a signal suitable for transmission over a given communication medium.

A Receiver is a collection of electronic circuits designed to convert the signal back to the original information.

The Communication channel is the medium by which the electronic signal is transmitted from one place to another.

What is Modulation?

Modulation Definition :
Modulation is the process of superimposing the information contents of a modulating signal on a carrier signal (which is of high frequency) by varying the characteristic of carrier signal according  to the modulating signal.

Modulation is a process in which the base band signal modifies another high-frequency signal called the carrier.

Types of Modulation

We can modulate the information bearing signal into two types namely. These are called Modulation Techniques.
1. Analog Modulation
2. Digital Modulation
Analog modulation is the process of converting an analog input signal into a signal that is suitable for RF transmission.

Digital modulation is the process of converting a digital bistream into an analog signal suitable for RF transmission.

Modulation Index

Modulation Index indicates the depth of modulation. As the amplitude of the modulating signal increases, modulation index increases. For amplitude modulation, the modulation index is given as

m =$\frac{E_{m}}{E_{c}}$

m = $\frac{Amplitude\ of\ modulating\ signal}{Amplitude\ of\ the\ carrier}$.

For frequency modulation,

m = $\frac{\delta}{f_{m}}$
m = $\frac{Maximum\ frequency\ deviation}{Modulating\ frequency}$.

Analog Modulation

The Analog carrier signal is modulated by analog information signal so that information bearing analog signal can travel larger distance without the fear of loss due to absorption.

The Analog modulation is of two types:
1. Amplitude Modulation
2. Angle Modulation
The Angle modulation is further classified as Frequency modulation and Phase Modulation.

Amplitude Modulation: In this type of modulation the strength of the carrier signal is varied with the modulating signal.

Frequency Modulation: In this type of modulation the frequency of the carrier signal is varied with the modulating signal.

Phase Modulation: In this type of modulation the phase of the carrier signal is varied with the modulating signal. It is the variant of the frequency modulation.

The analog carrier signal is modulated by digital information signal. It is also considered as digital to analog conversion.

Digital Modulation

Digital modulation means an analog signal of carrier is converted by a digital data bit stream.
There are two types of bits in binary:

1. Logic 0 (low)
2. Logic 1 (High).

This method is use to convert digital signal to analog and the responding demodulating is applied to convert analog signal to digital signal. Here the analog signal bearing information is transmitted by the digital method.

There are four types of Digital modulation which are as below:

1. Pulse code Modulation
2. Differential Pulse code Modulation
3. Delta Modulation

Pulse Modulation

Pulse Modulation :
The Pulse wave modulation is a process of sampling of the continuous wave at periodic intervals and transmitting a very short pulse of radio frequency carrier for each sample, with the pulse characteristics being varied in some manner proportional to the signal amplitude at the sampling instant.

The Pulse wave modulation are of four types namely:
1. Pulse amplitude Modulation
2. Pulse position Modulation
3. Pulse width Modulation
4. Pulse code Modulation.