**What is Modulation?**

**Modulation Definition**: Translation of Low Frequency signal to high frequency signal is generally referred as modulation. By doing so, we transfer the low frequency message signal to longer distances. This can be illustrated with paper and stone example as discussed below.

**Basic need for Modulation**:

Take
a paper of some size and try to through it to 5-10 meter distance. It is impossible
to through a plain paper to such longer distance, because the weight of that
paper is very less. Now take a stone of some size and place the stone in the
paper and enclose the stone. Now through the paper enclosed stone and then
observe the distance travel by it. Obviously, the paper enclosed stone travels
long distance than a plain paper because, the weight of the plain paper
translated to higher weight of stone.

Modulation technique using paper and stone analogy |

The
same analogy can be applied to our communication systems, where message signal
of lower frequency can be sent to longer distance by translating the message
signal frequency to higher frequencies. This technique is called “frequency
translation or modulation”.

If
f

Mathematically modulation is given by,

_{1}(t) is the message signal (paper) contains information to be transmitted and f_{2}(t) as carrier signal (stone), then the modulated signal will be given as f_{1}(t) X f_{2}(t). The carrier signal is enclosed by the message signal.Mathematically modulation is given by,

A simple proof for this modulation technique is shown by using a simple project DESIGN OF INFRARED IR TRANSMITTER AND RECEIVER CIRCUIT USING 555 TIMER AND TSOP1738.

In this project, we have been using 38khz as a carrier signal to transmit the IR signal over a long distance and at the same time it should detectable by the TSOP1738 infrared receiver.

There three types of modulations

1. Amplitude modulation

2. Frequency modulation

3. phase modulation

There three types of modulations

1. Amplitude modulation

2. Frequency modulation

3. phase modulation

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