Modulation And Demodulation:Variants & Advantages

Definition of Modulation:

“Modulation is the process of requiring information contained a lower frequency electronic signal onto a higher frequency signal.”

The higher freq signal is named carrier signal and the lower freq signal is termed as the modulating signal.

The upside of sending the higher freq signal is multiple: Firstly if all radio broadcasts broadcast at sound frequencies, they couldn’t be recognized from each other, and just a mix or jumbled signal will be there. Second, it is discovered that specific antenna with a range of 5 miles to 5000 miles is essential for the audio transmissions.

The expression of the modulated carrier wave is,

                                            A sin 2πfct

If, for straightforwardness a particular audio signal is taken as the modulating signal, it can be characterized as,

                                      B sin 2πfat

The modulated signal may be represented by,

                                 (A + Bsin2πfat)(sin 2πfct)

                           V = Vc (1 + B/A sin2πfat) (sin2πfct)

Modulation Factor:

         m = The ratio of “peak value of the modulating signal” with ‘the peak value of the un-modulated signal”

Percent Modulation:

         M = B/A x 100

The modulation percentage may differ somewhere in the range of zero to 100 without distortion. When the per cent modulation is crossing 100 per cent,  noisy frequencies are mixed, and hence distortion is the result.

Types of Modulation:

There are mainly 2 modulation types,

  1. Analog modulation –  It’s a technique of transferring analog baseband signal like audio or TV signal over a higher frequency signal.
  2. Digital modulationthis is a digital technique of encoding digital info.

Again, Analog Modulation has different types; such as

Amplitude Modulation:

“A modulation process in that amplitude of carrier is differed in agreement by means of the instantaneous value of modulating signal is termed as Amplitude Modulation”.

Regarding correspondences, an essential thing for modulation is to encourage the transmission of the data-bearing sign over a radio channel with a recommended passband. In continuous-wave modulation, this is made operational by amplitude or changing the angle of the sinusoidal carrier.

Definitions related to Modulation and Demodulation

Modulation Index of Amplitude Modulation:

Modulation index demonstrates what amount modulated variable of the carrier signal converted around its unmodulated level. In AM , this amount otherwise called modulation depth indicate how much the modulated parameter variable differs around its unique level.Mathematically modulation index is, ma, well-defined by,

                                                      where, K = proportionality constant;

              Vm = amplitude of modulating signal;

              Vc = amplitude of carrier signal;

Angle Modulation

“Angle modulation is a non-linear process and transmission bandwidth is typically much more than the message band width.

Angle modulation is of two types. They are – Frequency Modulation and Phase Modulation.

A valuable component of angle modulation is that it can give better output in noisy and interference presence than AM technique. This improvement in execution is accomplished to the detriment of expanded transmission data transfer bandwidth; that is good methods for channel bandwidth with improved noise performance. 

Also, in angle modulation, the improvement in execution is possible at the expense of system circuit complexity in both the transmitter and collector. This is not possible in case of amplitude modulation technique.

Angle Modulation can further be divided into:

  1. Frequency Modulation:
  2. Phase Modulation:

Frequency Modulation

Frequency modulation is the form of angle modulation in which instantaneous frequency of the carrier is varied linearly with the instantaneous amplitude change of the modulating signal”.(link wiki)

Michel Bakni creator QS:P170,Q81411358, FM Modulation – enCC BY-SA 4.0

Frequency Modulation has two important sections:


Narrow band Frequency modulation has modulation-index around one. The greatest deviation is δ<<fm. The equation of bandwidth is given by the following equation. a

 B = 2fm.


Typically the Wider Band Frequency modulation has modulation index greater than the one. The equation of bandwidth is represented in the following equation.

                                           B = 2(δ+fm)

For wideband FM δ<<fm and hence B =

Phase Modulation:

“Phase Modulation technique is an example for conditioning or tuning the correspondence communication signal for transmission.”

The period of a carrier signal is modulate to follow the changing sign degree of the message signal.

PM is the part of angle modulation where the θi (t) directly proportional to message signal m(t) as appeared by,

                                 θi(t) = 2πfct + kp m(t)

Digital Modulation can further be divided into:

  1. ASK (Amplitude Shift keying)
  2. FSK (Frequency Shift Keying)
  3. PSK (Phase Shift Keying)

What is Demodulation?

Definition of Demodulation:

Demodulation is basically extracting the original information carrying signal from a carrier wave.

Where as a demodulator is an circuitry that is utilized to recover original information or data from the modulated signal.

Some important demodulators (detectors) used for demodulating are:

  • Square law demodulator
  • Envelope detector

There are different demodulation techniques available dependent on the base-band signal parameters, for example,  amplitude, freq or phase angle are transmitted in the carrier signal.  A synchronous detector could be utilized when a signal is modulated with a linear modulation technique. In contrast, a Frequency modulation demodulator or a Phase modulation demodulator can be utilized for a signal attuned with a unintended one.

Comparison between Modulation and Demodulation:

                           MODULATION                      DEMODULATION
This is the process of influencing data information on the carrier. This is the restoration of original information as collected from the carrier. 
In modulation, unique message signal is at all times mixed with carrier signal whose parameters are required modifications In the demodulation technique, the mixture of carrier and message signal is detached from each other, to produce actual signal.
Modulation prerequisites a modulator for the mixing of the two signals. Demodulation prerequisites demodulator to recuperate the original signal. 
Modulation is for transmit data to extensive distance. Demodulation is utilized to regain the original message signal.
Modulation is comparatively simple in between Modulation and Demodulation technique.. Demodulation is comparatively complex in between Modulation and Demodulation technique.
This image has an empty alt attribute; its file name is modulation-and-demodulations.jpg
Modulation And Demodulation
Image Credit : Calzavara S.p.a., Optical modulationCC BY-SA 3.0

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Soumali Bhattacharya

I am currently invested in the field of Electronics and communication. My articles are focused towards the major areas of core electronics in a very simple yet informative approach. I am a vivid learner and try to keep myself updated with all latest technologies in the field of Electronics domains. Let's connect through LinkedIn -

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