AMERICAN INTERNATIONAL UNIVERSITY BANGLADESH
Faculty of Engineering
Laboratory Report Cover Sheet
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Laboratory Title: Study of Amplitude Modulator and Demodulator using Simulink.
Experiment Number: 06 Submission Date: 05/08/2024 Semester: Summer 2023 – 2024
Subject Code: COE 3103 Subject Name: Data Communication Section: B
Course Instructor: MD. SHAORAN SAYEM Degree Program: BSc CSE
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Group Number (if applicable): 06 Individual Submission Group Submission
No. Student Name Student ID
1 AKASH ROY 22-48054-2
2 DIP SARKER 22-49304-3
3 MD. DIDARUL ALAM TOWHID 22-48064-2
4 NASMIN SURAYA 22-48022-2
5 JANNATUL FERDOUSI NISA 22-48041-2
6 LAMIA TAHSIN 22-46345-1
For faculty use only: Total Marks: Marks Obtained:
Faculty comments
Title: Study of Amplitude Modulator and Demodulator using Simulink.
Abstract:
The project focuses on utilizing Simulink to examine amplitude modulators and demodulators.
MATLAB software is required for this simulation experiment to comprehend the traditional
Amplitude Modulation and Demodulation technique. Learning more about modulated, massage,
and carrier signals is the significance of this experiment.
Introduction:
A modulation technique called amplitude modulation, or AM is used in electronic
communications, primarily for radio wave-based message transmission. A wave's amplitude
changes in proportion to the amplitude of a message signal, such as an audio signal, when
amplitude modulation is used. The opposite of this method is angular modulation, which
modifies the carrier frequency as in frequency modulation, or phase modulation, which modifies
the carrier phase. The earliest modulation technique for broadcast audio transmission was AM.
This original form of AM is sometimes called (DSBAM) because the standard method produces
sidebands on either side of the carrier frequency. SSB modulation uses a bandpass filter to
remove one sideband and possibly the carrier signal, increasing the ratio of message power to
total transmit power, reducing the power handling requirements of line amplifiers, and allowing
better utilization of the bandwidth of the transmission medium.
Carrier signal (Sc) = Acsin(2πfct)
Message signal (Sm) = Amsin(2πfmt) # fm must be smaller than fc
When carrier amplitude is altered concerning the message signal,
Modulated Signal = (Ac+ Amsin (2 πfmt)) *sin (2 πfct)
In terms of modulation index (m=Am/Ac) the equation becomes
Modulated signal= (1+ msin (2 πfmt)) *Acsin(2 πfct)
Were,
Ac= Carrier signal amplitude
Am = Message signal amplitude
fc= Carrier frequency
fm =Message frequency
When discussing the complete demodulation process, the phrases detection and demodulation are
sometimes used interchangeably. These phrases refer to the same circuit and procedure. The
process of demodulation, as its name implies, is the reverse of modulation, which involves
applying a signal, like an audio signal, to a carrier. The audio or other signal carried by the
amplitude change on the carrier is separated from the overall signal during the demodulation
process and appears at the output. The most typical output is audio since amplitude modulation is
most frequently employed in audio applications. This can be utilized for broadcast reception in
entertainment applications, and it is frequently employed in walkie-talkies for two-way radio
communication in aviation-related terrestrial communications.
Performance Task:
BLOCK DIAGRAM OF AM MODULATION:
Figure: AM Generation using Simulink – Message Signal
Performance Task:
BLOCK DIAGRAM OF AMPLITUDE DEMODULATION:
Figure: AMPLITUDE DEMODULATION Generation using Simulink
Figure: AMPLITUDE DEMODULATION OUTPUT WAVEFORMS
Discussion: The carrier may occur at a certain frequency in the modulator while the
demodulator may anticipate the same at a different frequency. This is so since the demodulator
employs the carrier frequency to effectively separate the modulated message signal from the
carrier wave. Hence, on the practical level, the work of both the modulator and the demodulator
implies their correct tuning at the same carrier frequency for efficient signal recovery and
optimal operation of the system.
Conclusion:
This experiment aims to learn more about amplitude modulation and demodulation in
communications theory. Examine the underlying mathematical principles of amplitude
modulation and see how it affects frequency and time domains with the Analog Discovery
Studio. Devices that convert data to electrical signals, such as microphones that convert audio to
electrical signals, are utilized in amplitude modulation (AM) communication systems. The
amplitude of another signal, known as the carrier signal, is changed (modulated) using this
signal, which is known as the message or baseband signal. The modulation coefficient's
impact on the quality of the demodulated signal and the effects of other parameters can be
investigated and seen using an AM demodulator.
References:
[1] MATLAB user guide.
[2] Prof. Dr.-Ing. Andreas Czylwik, “MATLAB for Communications”
