Prepared ByPrepared ByEngr. Tafseer AhmedEngr. Tafseer Ahmed

AMPLITUDE AMPLITUDE MODULATIONMODULATION

AND AND DEMODULATIONDEMODULATION

MODULATION:MODULATION: Modulation is the process of varying one Modulation is the process of varying one

or more properties of a high-frequency or more properties of a high-frequency periodic waveform, called the carrier periodic waveform, called the carrier signal, with a modulating (message) signal signal, with a modulating (message) signal which typically contains information to be which typically contains information to be transmitted.transmitted.

TYPES OF MODULATIONTYPES OF MODULATION Amplitude Modulation.Amplitude Modulation. Frequency Modulation.Frequency Modulation. Phase Modulation. Phase Modulation.

OUR OBJECTIVEOUR OBJECTIVE Our objective is to implement amplitude Our objective is to implement amplitude

modulation using Matlab. modulation using Matlab.

AMPLITUDE MODULATIONAMPLITUDE MODULATION A type of modulation in which the A type of modulation in which the

amplitude of the carrier wave (signal) amplitude of the carrier wave (signal) changes according to the amplitude of changes according to the amplitude of message (modulating) signal.message (modulating) signal.

In this modulation the frequency of the In this modulation the frequency of the carrier signal remains same.carrier signal remains same.

PROCEDURE WHICH WE PROCEDURE WHICH WE HAVE FOLLOWED IN HAVE FOLLOWED IN

MATLABMATLAB

SPECIFICATION AND SPECIFICATION AND IMPORTANT TERMENOLOGIESIMPORTANT TERMENOLOGIES

SAMPLING FREQUENCY (fs)SAMPLING FREQUENCY (fs) The The sampling ratesampling rate , , sample ratesample rate , ,

or or sampling frequencysampling frequency  (fs) defines the  (fs) defines the number of number of samplessamples per unit  per unit of time (usually seconds) taken from of time (usually seconds) taken from a continuous signal to make a discrete a continuous signal to make a discrete signal. signal.

Here in our code we use fs =1000Here in our code we use fs =1000

SAMPLING TIME (ts)SAMPLING TIME (ts) The time interval after which we take the The time interval after which we take the

sample of our message signal.sample of our message signal. It is the reciprocal of sampling frequency It is the reciprocal of sampling frequency

(fs).(fs). Here in our code we use ts =1/1000Here in our code we use ts =1/1000

Nyquist–Shannon sampling Nyquist–Shannon sampling theorem theorem

states that perfect reconstruction of a states that perfect reconstruction of a signal is possible when the sampling signal is possible when the sampling frequency is greater than twice the frequency is greater than twice the maximum frequency of the signal being maximum frequency of the signal being sampled.sampled.

fs ≥ 2fmfs ≥ 2fm

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-4

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4The Modulating Signal

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The Modulating Signal in Frequency Domain

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5The Carrier Signal

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The Carrier Signal in Frequency Domain

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The Modulated Signal

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The Modulated Signal in Frequency Domain

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4The Modulating Signal

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0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-5

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5The Carrier Signal

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The Modulated Signal

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

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9Xint

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Xint (After DC Offset Elimination) in Frequency Domain

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Xint (After DC Offset Elimination) in Time Domain

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The Recovered Signal

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