This lab experiment involves using Matlab to represent and manipulate basic signals. The document describes coding exponential signals, pulse amplitude modulation (PAM) spectrum, and analog to digital conversion. The student is asked to write code to generate signals, plot the results, and observe the effects of changing parameters. Errors are encountered and solved. Subplots are used to display multiple graphs, and matrices are converted to a more convenient form.

1. Sargunan Ainal (JKE,PUO)
POLYTECHNIC UNGKU OMAR
ELECTRICAL ENGINEERING DEPARTMENT
Course : E5124 DATA COMMUNICATION (Lab work)
Experiment : Matlab 3 - Signals in Matlab
Introduction
This lab will describe how to use Matlab for some basic signal representation and manipulation:
• Creating and importing signals
• Sampling
• Signal visualization
• Modulation
Student must prepare before entering lab session and in your report below items must be included :
i. Title
ii. Objective
iii. Understanding of experiment
iv. Observation
v. Question & Answer
vi. Reflection
Activities
Students need to performe below programing in sequence to obtain result.
1. Exponential Signal
Write below source code for below equaltion;
Limit for given x is and step limit is 0.1
Hints : source code for exponential is exp( )
1.1. Write the source code and the output graph line must be in red color.
Observation
x = -2*pi:0.1:2*pi;
y = exp(x);
plot(x,y,'r')
1.2. Sketch the result and label the y-axis, x-axis and provide title as given “Exponential 1”.
Observation
1

2. Sargunan Ainal (JKE,PUO)
1.3. Now, writesource code to produce resultfor below equation.
Limit for given x is and step limit is 0.1
Observation
x = 0:0.1:10;
y = exp(x);
plot(x,y,'r')
1.4. Now plot both result in single Figure outcome (use subplot).
Hints : use suubplot and label with title your output
Observation
1.5. Write the source code used and state your comparison.
Observation
2

3. Sargunan Ainal (JKE,PUO)
2. Pulse Amplitude Modulation (PAM)
Procedure:
a. Launch the Matlab program (click Matlab icon)
b. Click tab, FILE NEW M-FILE . New window screen will pop out and it looks like notepad. Use it to write below
source code.
% Name : fill in your name
% Reg No. : fill in your reg. no
% Class : fill in class
% Sampling frequency 24000 Hz
% Symbol time interval [s].
T = 1/8000;
Fs = 24000;
% Time vector (sampling intervals) , -5T<1/Fs>5T
t = -5T:1/Fs:5T;
% Otherwise, the denominator would be zero at t=0 (or manually set “p(t=0)=1”)
t = t+1e-10;
% Roll-off factor
alfa = 0.5;
p = (sin(pi*t/T)./(pi*t/T)).*(cos(alfa*pi*t/T)./(1-(2*alfa*t/T).^2));
% Raised-Cosine FIR filter
clf;
plot(ts,p)
hold on;
stem(ts,p)
hold off;
c. Save the written source code using “PAM.m” name.
d. At the same window, click tab DEBUG RUN.
Now the source code will execute and produce result. Check the Matlab main window at Command Window
prompt, there will be error occurance.
e. What are the errors and how you solve it?
Observation
t = -5T:1/Fs:5T; t = -5*T:1/Fs:5*T;
plot(ts,p) plot(t,p);
stem(ts,p) stem(t,p);
f. Label x-axis with Time, y-axis with Amplitude and title as PAM Spectrum and state observation
Observation
g. Now, change the below parameter
i. T = 1/8000 with T=1/2000, record your observation
3

4. Sargunan Ainal (JKE,PUO)
Observation
ii. Reset the T value to original and change the sampling frequency to 240kHz, record your observation
h. Why there is clf command in the program and explain it.
clf deletes from the current figure all graphics objects whose handles are not hidden
i. Set back samapling frequency 240kHz to 24kHz. What will happen if the hold on is removed?
Observation
4

5. Sargunan Ainal (JKE,PUO)
3. Analogue to Digital
3.1. Wite this source code in M-File.
n=[0:1/44100:1];
sine1=sin(2*pi*10.*n)
sine2=0.5*sin(2*pi*30.*n)
sine3=0.25*sin(2*pi*50.*n)
sine4=0.125*sin(2*pi*70.*n)
sine5=0.0625*sin(2*pi*90.*n)
figure(1)
subplot(5,1,1);
plot(n,sine1);
subplot(5,1,1);
plot(n,sine1+sine2);
plot(n,sine1+sine2+sine3)
subplot(5,1,4);
plot(n,sine1+sine2+sine3+sine4);
subplot(5,1,4)
plot(n,sine1+sine2+sine3+sine4+sine5)
3.2. Save the written source code using “ADC” name.
3.3. Execute RUN command.
3.4. Now the source code will execute and produce result. Check the Matlab main window at Command Window
prompt.
3.5. What are the errors and state your solutions.
Observation
3.6. Label x-axis with Number of sample, y-axis with Amplitude and title as Analogue to Digital for each graphical output.
Observation
3.7. Now, change the below parameter
a) sine5=0.0625*sin(2*pi*90.*n) to sine5=0.0625*sin(2*pi*190.*n), record your observation
Observation
b) Reset the sine5 value to original and add another one more graph output in your display. Record your
observation and there will be minor changes between graph sine5 and the new graph.
Observation
5

6. Sargunan Ainal (JKE,PUO)
3.8. Remain the 3.7. result.
3.9. What is the meaning of subplot (5,1,4)?
____________________________________________________________________________________
____________________________________________________________________________________
3.10. Convert your 6x1 matrices to other form of matrices which more convinent to application.
Observation
6