Modulation & demodulation, Assignments of Data Communication Systems and Computer Networks

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Modulation

 ANALOG MODULATION

 DIGITAL MODULATION

Submitted to :

Mam Sumaira

Submitted by:

Abdullah Akram

Roll no:

Class:

BSCS(4th)

Topic :

Use Case

Analog modulation Analog modulation refers to the process of transferring analog low frequency baseband signal, like an audio or TV signal over a higher frequency carrier signal such as a radio frequency band. Baseband signal is always analog for this modulation.  (^) There are three properties of a carrier signal amplitude, frequency and phase thus there are three basic types of analog modulations.

1. Amplitude Modulation

2. Frequency Modulation

3. Phase Modulation

 Amplitude Modulation (AM) Amplitude modulation is a technique by which the amplitude of the carrier waves is changed according to the signal wave or modulating signal.

This amplitude modulating wave contain a time –varying amplitude that is termed as an envelops. This envelope has same shape as that of the message signal.

 Frequency modulation (FM)  (^) A category of angel modulation in which the frequency of the carrier wave is changed according to the amplitude of the message signal is known as frequency modulation.  (^) Its abbreviated as FM.

I. The first image in the above figure shows the modulating signal that has to be transmitted from an end to other. II. The second one is the carrier wave, whose frequency is to be varied according to the amplitude of the message signal. III. The third image shows that the frequency modulated signal that is transmitted after modulation is hone.

Phase modulation (pm)  (^) Phase modulation is another type of angle modulation in which the phase of the carrier wave is changed according to the amplitude (magnitude) of the message (modulating) signal.  (^) In phase modulation of an analog signal the phase change is a continuous back and fourth movement. While in case of digital signal there exist an abrupt change in the phase of carrier signal.  (^) The phase modulation of the digital signal is generally known as phase shift keying.

 Amplitude shift keying(ASK)  (^) ASK is a type of amplitude modulation which represents the binary data in the form of variation in the amplitude of a signal. Any modulated signal has a high frequency carrier. Modulated signal zero give for low and one for high.

 Frequency shift keying (FSK)  (^) FSK is digital modulation technique in which the frequency of the carrier signal varies according to the digital signal change. FSK is a schema of frequency modulation.