University of Dubai
College of Engineering and IT
Department of Electrical Engineering
ENCS 300 Communication Systems
Laboratory Experiment No.1
Experiment Title: Basic Operations in MATLAB, Simulink, and Multisim
Instructor: Dr. Diana & Haitham Abu Damis
Objectives: Become familiar with basic operations on waveforms in MATLAB,
Simulink, and Multisim
Risk Assessment: Low
Introduction
In this lab we will review the concepts of waveform addition and multiplication. Both operations are
pervasive in communication systems. We will review these operations in MATLAB, Simulink and
Multisim.
MATLAB and Simulink can only provide us with high level and theoretical modeling and analysis
capabilities. Typing code in MATLAB to model certain modulation schemes and mathematical operations
can only serve as a starting point for further study. Simulink allows us to connect and configure blocks to
gain a system-level view of such operations.
In actual communication systems, mathematical operations are implemented in hardware. In addition,
the hardware implementation utilizes components that you have already come across during your
studies. MOSFETs, BJTs, Diodes, Capacitors and other such components are the actual building blocks of
communication systems. Hence, we will also use Multisim to implement communication system blocks
such as adders and mixers.
Preliminary Task (20 points in total)
Review the following:

Trigonometric product identities:


Fourier series
Fourier transform
1- What is the product of multiplying a sine wave of frequency 5Hz and an amplitude of 1, with
another sine wave of frequency 10Hz and an amplitude of 2? Solve it numerically and show your
work. (10 points)
2- What are the frequency components of the result? (10 points)
Task 1. MATLAB (5 points each)
1- Generate a continuous sine wave with a frequency of 5Hz and Amplitude 1. Call the waveform
“x”.
2- Plot the continuous waveform. Use the subplot() and plot() functions to plot the waveform.
(Make sure to show more than one cycle by setting the time domain from zero to 1 seconds in
steps of 1 ms (hence, t = 0 : 0.001 : 1)
3- Generate a continuous sine wave with a frequency of 50Hz and Amplitude 1. Call the waveform
“y”. Plot the waveform using the subplot() and plot() functions as before. Again, use the same
time window as in part (b).
4- Add both waveforms and plot the result.
5- Multiply both waveforms and plot the result.
6- Change the frequency of “x” to 3Hz. Plot the sum and product of “x” and “y” and
comment on any differences you see compared with when “x” had a frequency of 5Hz.
Task 2: Simulink (40 points in total)
Now, we shall model our work in Task 1 in Simulink. So code will be represented in blocks.
This will give us a high level control in the design of communication systems. High-level control
abstracts the inner working of code and does not provide full insight into the internal mechanism
of the building blocks of a system. In any case, Simulink is a great tool in simulating and
emulating communication systems and other kinds of systems. Our purpose is to get more
familiar with such a tool.
In Simulink, click on the Library browser and select the following blocks:
1234-
Add
Product
Sine wave ( 2 blocks )
Scope.
Assign The sine waves the following parameters (10 points):
Figure 1. Sine wave block 1 (lower frequency).
Figure 2. Sine wave block 2. (higher frequency).
Hence, one sine wave will have an amplitude of 1 and a frequency of 5Hz. And the other
sine wave will have an amplitude of 1 and a frequency of 50Hz. Make sure to include the
(2*pi) expression as the units of frequency in Simulink are in rad/sec.

Provide screenshots for each of the following steps (10 points each):
1- Connect the blocks in the following manner:
2- Run the simulation and observe the scope display.
3- Change the amplitude of the 50Hz signal to 2. And observe the outcome
Task 3: Multisim (20 points in total)
For this task, we will implement the modeled mathematical operations using electrical components. This
should give you a hint to how real-life communication system blocks are designed with hardware.
We will build an adder circuit and a multiplier circuit (mixer). For reference, watch the accompanying
video tutorial posted on Moodle and uploaded to YouTube (https://youtu.be/eW48h_5Acj8).
1- Implement the adder circuit. What kind of electrical components where used? What kind of
impedance is found in the circuit? Is it linear or non-linear?
Its linear because it has resistor
2- Implement the mixer circuit. What kind of electrical components where used? What kind of
impedance is found in the circuit? Are there any non-linear components in the circuit?
Its non-linear because it has capacitor and inductor