Showing posts with label Need of modulation. Show all posts
Showing posts with label Need of modulation. Show all posts

## 16 Oct 2017

### What is Modulation and why Modulation is Required | Need and Benefits of Modulation

Before understanding the need and benefits of modulation, it is important to know, what is modulation?

# What is Modulation

Modulation is a process by which some characteristic (amplitude/frequency/phase) of a high frequency carrier wave is varied, in accordance with the instantaneous value of the message signal (modulating signal/ baseband signal).

COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

Now let's write down the benefits of modulation. We will discuss each point in detail one by one-

# Need and Benefits of Modulation

1.To remove interference problem
2.Practical height of the antenna
3.Possibility of multiplexing
4.Long distance communication
5.Improved signal quality at the receiver

## 1.To Remove Interference Problem

Modulation helps in removing the interference problem by allocating a separate frequency band to different signal transmissions.
Because of this it becomes possible for many stations to transmit their message signals simultaneously without any interference.
Ex. The transmission range for audio signals is 20Hz-20kHz.

The height of antenna used for transmission and reception of the signal also depends on the process of modulation. The transmitting and receiving Antennas must have lengths, comparable to a quarter wavelength (位/4) of the frequency used for transmission.

#Digital Modulation Techniques (ASK, FSK, PSK, BPSK)/ Amplitude, Frequency and Phase Shift Keying

To understand how the frequency used for transmission of the signal affects the height of the antenna.
As mentioned earlier, height of the antenna should be comparable to 位/4 of the frequency used for transmission.
height of the antenna= 位/4
Since we know that-
c=位.f
here c is speed of light in vacuum= 3×10^8 m/s
f is frequency
Therefore 位= c/f
So height of the antenna would be-
(c/f).(1/4)
here c and 1/4 are constants
Therefore antenna height is inversely proportional to frequency used for transmission.
It means as the frequency of modulation increases, height of the antenna used for transmission decreases.
We Will understand it will the help of an example-
Here we will see, how the height of the antenna reduced when we increased the frequency used for transmission from 4kHz to 5MHz after modulation.
Height= 位/4
=(c/f).(1/4)
= (3×10^8 m/s)/(4×10^3Hz)× (1/4)
=0.187×10^5 meters
= 18.7 kilometers !!!
This height of antenna is not practical.
After modulation-
Frequency used is 5MHz
H=(c/f).(1/4)
=(3×10^8 m/s)/(5×10^6Hz)× (1/4)
=0.15×10^2 meters
15meters
It is practical height of the antenna.