Post on 11-Jul-2020
DIGITAL COMMUNICATION SYSTEMS LAB
III/IV B. TECH., I SEMESTER
STUDENT OBSERVATION MANUAL
DEPARTMENT
OF
ELECTRONICS & COMMUNICATION ENGINEERING
VEMU INSTITUTE OF TECHNOLOGY Tirupati - Chittoor Highway Road, P. Kothakota, Chittoor- 517 112.
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY ANANTAPUR
VEMU INSTITUTE OF TECHNOLOGY
DEPT. OF ELECTRONICS AND COMMUNICATION ENGINEERING
Vision of the institute
To be a premier institute for professional education producing dynamic and vibrant force of
technocrat with competent skills, innovative ideas and leadership qualities to serve the society
with ethical and benevolent approach.
Mission of the institute
Mission_1: To create a learning environment with state-of-the art infrastructure, well equipped
laboratories, research facilities and qualified senior faculty to impart high quality technical
education.
Mission_2: To facilitate the learners to foster innovative ideas, inculcate competent research and
consultancy skills through Industry-Institute Interaction.
Mission_3: To develop hard work, honesty, leadership qualities and sense of direction in rural
youth by providing value based education.
Vision of the Department
To become a centre of excellence in the field of Electronics and Communication Engineering
and produce graduates with Technical Skills, Research & Consultancy Competencies, Life-long
Learning and Professional Ethics to meet the challenges of the Industry and Society.
Mission of the Department
Mission_1: To enrich Technical Skills of students through Effective Teaching and Learning
practices for exchange of ideas and dissemination of knowledge.
Mission_2: To enable the students with research and consultancy skill sets through state-of-the
art laboratories, industry interaction and training on core & multidisciplinary technologies.
Mission_3: To develop and instill creative thinking, Life-long learning, leadership qualities,
Professional Ethics and social responsibilities among students by providing value based
education.
Programme Educational Objectives ( PEOs)
PEO_1: To prepare the graduates to be able to plan, analyze and provide innovative ideas to
investigate complex engineering problems of industry in the field of Electronics and
Communication Engineering using contemporary design and simulation tools.
PEO_2: To provide students with solid fundamentals in core and multidisciplinary domain for
successful implementation of engineering products and also to pursue higher studies.
PEO_3: To inculcate learners with professional and ethical attitude, effective communication
skills, teamwork skills, and an ability to relate engineering issues to broader social context at
work place.
Programme Outcome (POs)
PO_1: Engineering knowledge: Apply the knowledge of mathematics, science, engineering
fundamentals, and an engineering specialization to the solution of complex engineering
problems.
PO_2: Problem analysis: Identify, formulate, review research literature, and analyze complex
engineering problems reaching substantiated conclusions using first principles of mathematics,
natural sciences, and engineering sciences.
PO_3: Design/development of solutions: Design solutions for complex engineering problems
and design system components or processes that meet the specified needs with appropriate
consideration for the public health and safety, and the cultural, societal, and environmental
considerations.
PO_4: Conduct investigations of complex problems: Use research-based knowledge and
research methods including design of experiments, analysis and interpretation of data, and
synthesis of the information to provide valid conclusions.
PO_5: Modern tool usage: Create, select, and apply appropriate techniques, resources, and
modern engineering and IT tools including prediction and modeling to complex engineering
activities with an understanding of the limitations.
PO_6: The engineer and society: Apply reasoning informed by the contextual knowledge to
assess societal, health, safety, legal and cultural issues and the consequent responsibilities
relevant to the professional engineering practice.
PO_7: Environment and sustainability: Understand the impact of the professional engineering
solutions in societal and environmental contexts, and demonstrate the knowledge of, and need
for sustainable development.
PO_8: Ethics: Apply ethical principles and commit to professional ethics and responsibilities
and norms of the engineering practice.
PO_9: Individual and team work: Function effectively as an individual, and as a member or
leader in diverse teams, and in multidisciplinary settings.
PO_10: Communication: Communicate effectively on complex engineering activities with the
engineering community and with society at large, such as, being able to comprehend and write
effective reports and design documentation, make effective presentations, and give and receive
clear instructions.
PO_11: Project management and finance: Demonstrate knowledge and understanding of the
engineering and management principles and apply these to one’s own work, as a member and
leader in a team, to manage projects and in multidisciplinary environments.
PO_12: Life-long learning: Recognize the need for, and have the preparation and ability to
engage in independent and life-long learning in the broadest context of technological change.
Programme Specific Outcome (PSOs)
PSO_1: Higher Education: Qualify in competitive examinations for pursuing higher education
by applying the fundamental concepts of Electronics and Communication Engineering domains
such as Analog & Digital Electronics, Signal Processing, Communication & Networking,
Embedded Systems, VLSI Design and Control Systems etc..
PSO_2: Employment: Get employed in allied industries through their proficiency in program
specific domain knowledge, specialized software packages and Computer programming or
become an entrepreneur.
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY ANANTAPUR
III B.Tech. I-Sem (ECE)
(15A04508) DIGITAL COMMUNICATION SYSTEMS LABORATORY
Minimum of Ten Experiments to be conducted (Five from each Part-A & B)
Course Outcomes:
C318.1: Analyze the PCM, DPCM,DM,ADCM using hardware &software
C318.2: Analyze the different shift keying techniques using hardware &software
C318.3: Explain the time division multiplexing technique
C318.4: Analyze the QAM using signal space analysis
HARDWARE EPERIMENTS (PART-A)
1. Time division multiplexing.
2. Pulse code modulation.
3. Differential pulse code modulation.
4. Delta Modulation.
5. Frequency shift keying.
6. Differential Phase shift Keying.
7. QPSK Modulation and Demodulation.
SOFTWARE EXPERIMENTS (PART-B)
Modeling of Digital communications using MATLAB
1. Sampling Theorem-Verification.
2. Pulse code modulation.
3. Differential pulse code modulation.
4. Frequency shift keying.
5. Phase shift keying.
6. Differential Phase shift Keying.
7. QPSK Modulation and Demodulation.
CONTENTS
S. NO. NAME OF THE EXPERIMENT PAGE NO
HARDWARE EXPERIMENTS
1 Time Division Multiplexing 1-4
2 Pulse Code Modulation 5-8
3 Delta Modulation 9-11
4 Frequency Shift Keying 12-13
5 Differential Phase Shift Keying 14-16
SOFTWARE EXPERIMENTS
6 Sampling Theorem Verification 17-20
7 Pulse Code Modulation 21-22
8 Frequency Shift Keying 23-24
9 Phase Shift Keying 25-26
10 QPSK Modulation And Demodulation 27-29
ADDITIONAL EXPERIMENTS
11 Line Codes 30-31
12 Delta Modulation Using MATLAB 32-33
DOS & DONTS IN LABORATORY
1. While entering the Laboratory, the students should follow the dress code
(Wear shoes, White Apron & Female students should tie their hair back).
2. The students should bring their observation note book, practical manual,
record note book, calculator, necessary stationary items and graph sheets if
any for the lab classes without which the students will not be allowed for
doing the practical.
3. All the equipments and components should be handled with utmost care.
Any breakage/damage will be charged.
4. If any damage/breakage is noticed, it should be reported to the instructor
immediately.
5. If a student notices any short circuits, improper wiring and unusual smells
immediately the same thing is to be brought to the notice of technician/lab in
charge.
6. At the end of practical class the apparatus should be returned to the lab
technician and take back the indent slip.
7. Each experiment after completion should be written in the observation note
book and should be corrected by the lab in charge on the same day of the
practical class.
8. Each experiment should be written in the record note book only after getting
signature from the lab in charge in the observation note book.
9. Record should be submitted in the successive lab session after completion of
the experiment.
10. 100% attendance should be maintained for the practical classes.
SCHEME OF EVALUVATION
S
NO NAME OF EXPERIMENT DATE
MARKS AWARDED TOTA
L
(30M)
Record
(10M)
Observat
ion
(10M)
Viva
voce
(10M)
Attenda
nce
(10M)
HARDWARE EXPERIMENTS
1 Time Division Multiplexing
2 Pulse Code Modulation
3 Delta Modulation
4 Frequency Shift Keying
5 Differential Phase Shift
Keying
SOFTWARE EXPERIMENTS
1 Sampling Theorem
Verification
2 Pulse Code Modulation
3 Frequency Shift Keying
4 Phase Shift Keying
5 QPSK Modulation And
Demodulation
Signature of Lab In-charge
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 1
Exp .No: 1 Date:
TIME DIVISION MULTIPLEXING
Aim:
To demonstrate Time Division Multiplexing and Demultiplexing process using Pulse
Amplitude Modulation signals.
Equipment Required:
1. Experimenter kit DCL-02.
2. Connecting chords.
3. Power supply.
4. 20 MHz dual trace oscilloscope.
Block Diagram:
Procedure:
1. Refer the block diagram and carry out the following connections and switch settings.
2. Connect power supply in proper polarity to the kit DCL-02 & switch it in.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 2
3. Connect 250 Hz, 500 Hz, 1 KHz, and 2 KHz sine wave signal from the function
generator to the multiplexer input channel CH0, CH1, CH2, CH3 by means of the
connecting chords provided.
4. Connect the multiplexer output TXD of the transmitter section to the demultiplexer
input RXD to the receiver section.
5. Connect the output of the receiver section CH0, CH1, CH2, CH3 to the IN0, IN1,
IN2, IN 3 of the filter section.
6. Connect the sampling clock TX CLK and channel identification Clock TXSYNC of
the transmitter section to the corresponding RX CLK and RXSYNC of the receiver
section respectively.
7. Set the amplitude of the input sine wave as desired.
8. Take the observation as mentioned below.
Observations:
Signals Amplitude(V) Time Period(s)
250Hz
500HZ
1 KHz
2 KHz
TX CLK
RX CLK
TXD
RXD
CH0
CH1
CH2
CH3
OUT0
OUT1
OUT2
OUT3
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 3
Model Graphs:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 4
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 5
Exp .No: 2 Date:
PULSE CODE MODULATION
Aim:
To study and analyze the performance of Pulse Code Modulation and Demodulation
Process.
Equipment Required:
1. PCM Modulator and Demodulator trainer kit
2. CRO
3. Connecting chords.
4. Power supply.
Block Diagram:
Fig: Block diagram of PCM modulation & Demodulation
Procedure:
1. Refer the block diagram and carry out the following connections.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 6
2. Connect power supply in proper polarity to the kit DCL-03 and DCL-04 & switch it
in.
3. Connect 500 Hz and 1 KHz sine wave signal from the function generator to the input
channel CH0 and CH1of the sample and hold logic.
4. Connect OUT 0 to CH0 IN and OUT 1 to CH1 IN.
5. Set the speed selection switch SW1 to FAST mode.
6. Connect TXDATA, TXCLK and TXSYNC of the transmitter section DCL-03 to the
corresponding RXDATA, RXCLK, and RXSYNC of the receiver section DCL-04.
7. Connect posts DAC OUT to IN post of demultiplexer section on DCL-04.
8. Take the observations as mentioned below.
Observations:
Signals Amplitude(V) Time Period(s)
500 Hz
1 HZ
OUT 0
OUT 1
CLK 1
CLK 2
MUX OUT
DAC OUT
CLK 1
CLK 2
CH 0
CH 1
OUT0
OUT1
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 7
Model Graphs:
Fig: Waveforms for PCM modulation
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 8
Fig: waveforms for PCM demodulation
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 9
Exp .No: 3 Date:
DELTA MODULATION
Aim:
To study and analyze the performance of delta Modulation and Demodulation Process.
Equipment Required:
1. DCL-07 Kit.
2. Connecting Chords.
3. Power Supply.
4. CRO.
Block Diagram:
Fig: Block diagram for delta modulation
Procedure:
1. Refer to the block diagram and carry out the following connections and switch
techniques.
2. Connect power supply in proper polarity to the kit DCL-07 and switch it ON.
3. Select sine wave input 250Hz of 0V through pot P1 and connects post 250Hz to post
IN of input buffer.
4. Connect output of buffer post OUT to digital sampler input post IN1.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 10
5. Then select clock rate of 8KHz by pressing switch S1 selected clock is indicated by
LED glow.
6. Keep switch S2 in delta position.
7. Connect output of Digital sampler post OUT to input post IN of integrator 1.
8. Connect output of integrator 1 post OUT to input post IN2 of digital sampler.
9. Then observe the delta modulated output at output of digital sampler post OUT and
compare it with the clock rate selected. It is half the frequency of clock rate selected.
10. Observe the integrator output test point. It can be observe that as the clock rate is
increased amplitude of triangular waveform decreases. This is called minimum step
size. These waveforms are as shown below. Then increase the amplitude of 250Hz
sine wave upto 0.5v. signal approximating 250Hz is available at the integrator output.
This signal is obtained by integrating the digital output resulting from delta
modulation.
11. Then go on increasing the amplitude of selected signal through the respective pot
from 0 to 2V. it can be observed that the digital high makes the integrator output to go
upward and digital low makes the integrator output to go downwards. Observe that
the integrator output follow the input signal. The waveforms are as shown in fig.
observe the waveforms at various test-points in the delta modulator section.
12. Increase the amplitude of 250Hz sine wave through pot P1 further high and observe
that the integrator output cannot follow the input signal. state the reason.
13. Repeat the above mention procedures with different signal sources and selecting the
different clock rates and observe the response of delta modulator.
14. Connect delta modulated output post OUT of digital sampler to the input of delta
demodulator section post IN of demodulator.
15. Connect output of Demodulator post OUT to the input of integrator 3 post IN.
16. Connect output of integrator 3 post OUT to the input of output buffer post IN.
17. Connect output of output buffer post OUT to the input of 2nd order filter post IN.
18. Connect output of 2nd order filter post OUT to the input of 4th order filter post IN.
19. Keep switch S4 in HIGH position.
20. Then observed various tests points in delta demodulator section and observe the
reconstructed signal through 2nd order filter and 4th order filter. Observe the
waveforms as shown in fig.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 11
Observations:
Signals Amplitude(v) Time period(s)
250 Hz
Digital Sampler Output
Integrator 3 Output
Filter Output
Model Graphs:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 12
Exp .No: 4 Date:
FREQUENCY SHIFT KEYING
Aim:
To study and analyze the performance of Frequency Shift Keying Modulation and
Demodulation Process.
Equipment Required:
1. PHYSITECH’S FSK modulation and Demodulation trainer kit.
2. Function Generator
3. CRO
4. Connecting wires and Probes
Circuit Diagram:
Fig: Block diagram for FSK modulation
Procedure:
1. Connect the output of the carrier output provided on kit to the input of the carrier
input 1 terminal.
2. Also connect one of the Data output to the Data input terminal provided on kit.
3. Connect sine wave of certain frequency to the carrier input2 terminal.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 13
4. Switch ON function generator and FSK modulation and demodulation kit.
5. Observe the FSK output by connecting it to CRO. Thus FSK modulation can be
achieved.
6. For FSK demodulation, connect FSK output terminal to the FSK input terminal of
demodulator.
7. Observe the demodulated wave at demodulated output terminal by connecting it to
CRO.
Observations:
Signals Amplitude(v) Time period(s)
Data input
Carrier signal 1
Carrier signal 2
FSK output
Demodulated output
Model Graphs:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 14
Exp .No: 5 Date:
DIFFERENTIAL PHASE SHIFT KEYING
Aim:
To study and analyze the performance of Differential Phase Shift Keying Modulation and
Demodulation Process.
Equipment Required:
1. Experimental kit ADCL-01.
2. Connecting wires.
3. Power supply.
4. 20MHz dual trace oscilloscope
Block Diagram:
Procedure:
1. Refer to the block diagram and carry out the following connections and switch
techniques.
2. Connect power supply in proper polarity to the kit ADCL-01 and switch it on.
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 15
3. Select data pattern of simulated data using switch SW1.
4. Connect SDATA generated to DATA IN of NRZ-L CODER.
5. Connect the NRZ-L DATA output to the DATA IN of the DIFFERENTIAL
ENCODER.
6. Connect the clock generated SCLOCK to CLK IN of the DIFFERENTIAL
ENCODER.
7. Connect differentially encoded data to control input C1 of CARRIER
MODULATOR.
8. Connect carrier component SIN1 to IN 1 and SIN 2 to IN 2 of the carrier modulator
logic.
9. Connect DPSK modulated signal MOD OUT to MOD IN of the BPSK
DEMODULATOR.
10. Connect output of BPSK demodulator b(t) OUT to input of DELAY SECTION b(t)
IN and one input b(t) IN of decision device.
11. Connect the output of delay section b(t-Tb) OUT to the input b(t-Tb) IN of decision
device.
12. Compare the DPSK decoded data at DATA OUT with respect to input SDATA.
13. Observe various waveforms as mentioned below, if recovered data mismatches with
respect to the transmitter data, then use RESET switch for clear observation of data
output.
Observations:
Signal Amplitude(v) Time period(s)
SDATA
SCLOCK
NRZ-L DATA
Differentially encoded data
SIN 1
SIN 2
DPSK MOD OUT
Recovered differentially encoded
data
Delayed data
Recovered data (NRZ-L DATA)
DPSK Demodulation
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 16
Model Graph:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 17
Exp .No: 5 Date:
SAMPLING THEOREM VERIFICATION
Aim: To generate a MATLAB Program to verify sampling theorem.
Software Required:
➢ PC and MATLAB software
Procedure:
• Open MATLAB Software
• Open new M-file
• Type the program
• Save in current directory
• Run the program
• For the output see command window\ Figure window.
Program:
clc;
close all;
clear all;
f1=3;
f2=23;
t=-0.4:0.0001:0.4;
x=cos(2*pi*f1*t)+cos(2*pi*f2*t);
figure(1);
plot(t,x,'-.r');
xlabel('time-----');
ylabel('amp---');
title('The original signal');
%case 1: (fs<2fm)
fs1=1.4*f2;
ts1=1/fs1;
n1=-0.4:ts1:0.4;
xs1=cos(2*pi*f1*n1)+cos(2*pi*f2*n1);
figure(2);
stem(n1,xs1);
hold on;
plot(t,x,'-.r');
hold off;
legend('fs<2fm');
%case 2: (fs=2fm)
fs2=2*f2;
ts2=1/fs2;
n2=-0.4:ts2:0.4;
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 18
xs2=cos(2*pi*f1*n2)+cos(2*pi*f2*n2);
figure(3);
stem(n2,xs2);
hold on;
plot(t,x,'-.r');
hold off;
legend('fs=2fm');
%case 3: (fs>2fm)
fs3=7*f2;
ts3=1/fs3;
n3=-0.4:ts3:0.4;
xs3=cos(2*pi*f1*n3)+cos(2*pi*f2*n3);
figure(4);
stem(n3,xs3);
hold on;
plot(t,x,'-.r');
hold off;
legend('fs>2fm');
Output:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 19
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
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Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 21
Exp .No: 7 Date:
PULSE CODE MODULATION
Aim:
To write a MATLAB program for Pulse Code Modulation and to observe the output wave
forms.
Requirements:
➢ PC and MATLAB software
Procedure:
1. Open MATLAB Software
2. Open new M-file
3. Type the program
4. Save in current directory
5. Run the program
6. For the output see command window\ Figure window
MATLAB Program:
clc;
clear all;
close all;
t=0:.01:3;
a=sin(2*pi*t);
p=square(2*pi*10*t);
p(p<0)=0;
s=a.*p;
figure(1);
subplot(3,1,1);
plot(a);
xlabel('time');
ylabel('amplitude');
title('analog signal');
subplot(3,1,2);
plot(p);
xlabel('time');
ylabel('amplitude');
title('square signal');
subplot(3,1,3);
plot(s);
xlabel('time');
ylabel('amplitude');
title('sampled signal');
n=3;
y=uencode(s,n,1);
r=udecode(y,n,1);
figure(2);
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 22
subplot(2,1,1);
plot(y);
xlabel('time');
ylabel('amplitude');
title('encoded signal');
subplot(2,1,2)
plot(r);
xlabel('time');
ylabel('amplitude');
title('decoded signal');
MODEL GRAPHS:
Result:
0 50 100 150 200 250 300 350-1
-0.5
0
0.5
1
time
am
plitu
de
analog signal
0 50 100 150 200 250 300 3500
0.5
1
time
am
plitu
de
square signal
0 50 100 150 200 250 300 350-1
-0.5
0
0.5
1
time
am
plitu
de
sampled signal
0 50 100 150 200 250 300 3500
1
2
3
4
5
6
7
time
ampl
itude
encoded signal
0 50 100 150 200 250 300 350-1
-0.5
0
0.5
1
time
ampl
itude
decoded signal
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 23
Exp .No: 8 Date:
FREQUENCY SHIFT KEYING
Aim:
To write a MATLAB program for Frequency Shift Keying and to observe the output
waveforms.
Requirements:
PC and MATLAB software
Procedure:
1. Open MATLAB Software
2. Open new M-file
3. Type the program
4. Save in current directory
5. Run the program
6. For the output see command window\ Figure window
MATLAB Program:
clc;
close all;
clear all;
fc1=input('Enter the freq of 1st Sine Wave carrier:');
fc2=input('Enter the freq of 2nd Sine Wave carrier:');
fp=input('Enter the freq of Periodic Binary pulse (Message):');
amp=input('Enter the amplitude (For Both Carrier & Binary Pulse Message):');
amp=amp/2;
t=0:0.001:1;
c1=amp.*sin(2*pi*fc1*t);% For Generating 1st Carrier Sine wave
c2=amp.*sin(2*pi*fc2*t);% For Generating 2nd Carrier Sine wave
subplot(4,1,1); %For Plotting The Carrier wave
plot(t,c1);
xlabel('Time');
ylabel('Amplitude');
title('Carrier 1 Wave');
subplot(4,1,2) ;%For Plotting The Carrier wave
plot(t,c2);
xlabel('Time');
ylabel('Amplitude');
title('Carrier 2 Wave');
m=amp.*square(2*pi*fp*t)+amp;%For Generating Square wave message
subplot(4,1,3); %For Plotting The Square Binary Pulse (Message)
plot(t,m);
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-2
02
Time
Am
plit
ude Carrier 1 Wave
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-2
02
Time
Am
plit
ude Carrier 2 Wave
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
24
Time
Am
plit
ude Binary Message Pulses
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-2
02
Time
Am
plit
ude Modulated Wave
xlabel('Time');
ylabel('Amplitude');
title('Binary Message Pulses');
for i=0:1000 %here we are generating the modulated wave
if m(i+1)==0
mm(i+1)=c2(i+1);
else
mm(i+1)=c1(i+1);
end
end
subplot(4,1,4) ;%For Plotting The Modulated wave
plot(t,mm);
xlabel('Time');
ylabel('Amplitude');
title('Modulated Wave');
The Following Inputs Given To Generate FSK Modulated Wave:
Enter the freq of 1st Sine Wave carrier: 10
Enter the freq of 2nd Sine Wave carrier: 30
Enter the freq of Periodic Binary pulse (Message):5
Enter the amplitude (For Both Carrier & Binary Pulse Message):4
Wave Forms:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 25
Exp .No: 9 Date:
PHASE SHIFT KEYING
Aim: To write a MATLAB program for phase Shift Keying and to observe the output
waveforms
Experimental requirements:
➢ PC loaded with MATLAB software
Procedure:
1. Open MATLAB Software
2. Open new M-file
3. Type the program
4. Save in current directory
5. Run the program
6. For the output see command window\ Figure window
MATLAB Program:
clc;
clear all;
close all;
b = input('Enter the Bit stream \n '); %b = [0 1 0 1 1 1 0];
n = length(b);
t = 0:0.01:n;
x = 1:1:(n+1)*100;
for i = 1:n
if (b(i) == 0)
b_p(i) = -1;
else
b_p(i) = 1;
end
for j = i:.1:i+1
bw(x(i*100:(i+1)*100)) = b_p(i);
end
end
bw = bw(100:end);
sint = sin(2*pi*t);
st = bw.*sint;
subplot(3,1,1)
plot(t,bw)
gridon ;
axis([0 n -2 +2]) ;
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 26
subplot(3,1,2) ;
plot(t,sint) ;
grid on ;
axis([0 n -2 +2]) ;
subplot(3,1,3) ;
plot(t,st);
gridon ;
axis([0 n -2 +2]) ;
Wave forms:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 27
Exp .No: 10 Date:
QPSK MODULATION AND DEMODULATION
Aim:
To write a MATLAB program for QPSK Modulation and Demodulation and to observe the
output wave forms.
Experimental Requirements:
➢ PC and MATLAB software
Procedure:
1. Open MATLAB Software
2. Open new M-file
3. Type the program
4. Save in current directory
5. Run the program
6. For the output see command window\ Figure window
MATLAB Program:
clear;
clc;
b = input('Enter the bit stream = ');
n = length(b);
t = 0:0.01:n;
x = 1:1:(n+2)*100;
for i = 1:n
if (b(i) == 0)
u(i) = -1;
else
u(i) = 1;
end
for j = i:0.1:i+1
bw(x(i*100:(i+1)*100)) = u(i);
if (mod(i,2) == 0)
bw_e(x(i*100:(i+1)*100)) = u(i);
bw_e(x((i+1)*100:(i+2)*100)) = u(i);
else
bw_o(x(i*100:(i+1)*100)) = u(i);
bw_o(x((i+1)*100:(i+2)*100)) = u(i);
end
if (mod(n,2)~= 0)
bw_e(x(n*100:(n+1)*100)) = -1;
bw_e(x((n+1)*100:(n+2)*100)) = -1;
end
end
end
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 28
bw = bw(100:end);
bw_o = bw_o(100:(n+1)*100);
bw_e = bw_e(200:(n+2)*100);
cost = cos(2*pi*t);
sint = sin(2*pi*t);
x = bw_o.*cost;
y = bw_e.*sint;
z = x+y;
subplot(3,2,1);
plot(t,bw);
xlabel('n ---->');
ylabel('Amplitude ---->');
title('Input Bit Stream');
grid on ;
axis([0 n -2 +2]);
subplot(3,2,5);
plot(t,bw_o);
xlabel('n ---->');
ylabel('Amplitude ---->');
title('Odd Sequence');
grid on ;
axis([0 n -2 +2]);
subplot(3,2,3);
plot(t,bw_e);
xlabel('n ---->');
ylabel('Amplitude ---->');
title('Even Sequence');
grid on ;
axis([0 n -2 +2]);
subplot(3,2,4);
plot(t,x);
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('Odd Sequence BPSK Modulated Wave');
grid on ;
axis([0 n -2 +2]);
subplot(3,2,2);
plot(t,y);
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('Even Sequence BPSK Modulated Wave');
grid on ;
axis([0 n -2 +2]);
subplot(3,2,6);
plot(t,z);
xlabel('Time ---->');
ylabel('Amplitude ---->');
title('QPSK Modulated Wave');
grid on ;
axis([0 n -2 +2]);
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 29
Output:
Enter the bit stream = [0 1 1 0 1 0 0 0]
Model wave forms:
Result:
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 30
Exp .No: 11 Date:
LINE CODES
Aim:
To study the time and frequency domain characteristics of various line coding
signal formats.
Equipment:
1. TIMS system with modules
2 Channel 100MHz DSO
Background:
The TIMS line coder will accept a baseband TTL pulse stream and perform the
appropriate level and timing conversions to produce a number of unit-polar and bi-polar
analog level line codes. In this lab we will look at the characteristics of the following codes:
NRZ-L, NRZ-M, and RZ-AMI. and Biphase-L. The bit pattern for the experiment will be
generated by the TIMS sequence generator. In order to make time domain comparisons of the
line coder input and the decoder output, you’ll have to use the single acquisition mode of the
scope to capture frames of waveform data.
Procedure:
TIMS setup:
Refer to Figure 2 in the attached Lab Sheet. Configure the modules as shown, note
that the Buffer Amplifier is not inserted in the data path at the beginning of the lab. Note
that the Beginning of Sequence output of the Sequence Generator is used to trigger the
scope.
Measurements:
Time domain:
1) Connect channel 1 of the oscilloscope to the data input of the Line Encoder module.
Capture a screen of data, adjusting the time base of the scope so that you can easily
identify one bit time in the data input.
2) Observe the NRZ-L output with the second oscilloscope channel. Sketch a representative
portion of the input bit pattern and the NRZ-L output, a number of 0-1-0 transitions are
required. Verify that the coding is correct. From your observations, estimate the
fundamental frequency of the spectrum that the NRZ-L waveform would produce. (Hint:
Think square waves..)
3) Set the scope to free run, you won’t be able to see a synchronized output but you won’t
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 31
need to. While observing the NRZ-L output, switch the scope input coupling between DC
and AC. Is there a vertical shift in the waveform display? If so, record the change in
voltage.
4) Repeat steps 2 and 3 for the NRZ-M, RZ-AMI, and Biphase-L outputs.
Frequency Domain:
1. Use the FFT function of the scope to observe the signal spectrum of the NRZ-L output.
The spectrum will conform to your knowledge of the sinx/x function. Using the FFT
analyzer, determine:
a) The center frequencies of the sinx/x lobes (maximums)
b) The frequencies of the sinx/x nulls (minimums)
c) If possible, the frequencies of the components within each lobe envelope
2. Repeat step 5 for the NRZ-M, RZ-AMI, and Biphase-L outputs.
Polarity Reversal:
1. Connect the NRZ-L output of the Line Encoder to one input of the Buffer Amplifier.
Adjust the Buffer
2. Connect the NRZ-L output of the Line Encoder to the NRZ-input of the Line
Decoder. Observe the data input of the Line Encoder and the data output of Line
Decoder using the scope. The signals should be the same.
3. Insert the Buffer Amplifier into the circuit between the Line Encoder output and the
Line Decoder input and observe the data input and output again. Has the inversion
on the communication channel produced an inversion in the received data?
4. Repeat steps 8 and 9 for the NRZ-M, RZ-AMI, and Biphase-L outputs.
RESULT:
Code Offset (V) Maximums Nulls Components Polarity Sensitive?
(Hz) (Hz) (Hz) (Yes/No)
NRZ-L
NRZ-M
RZ-AMI
Bi∅-L
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 32
Exp .No: 12 Date:
DELTA MODULATION
Aim: To perform delta modulation in MATLAB
Experimental Requirements:
➢ PC loaded with MATLAB
Procedure:
1. 1. Open MATLAB Software
2. Open new M-file
3. Type the program
4. Save in current directory
5. Run the program
6. For the output see command window\ Figure window
MATLAB Program:
clc;
clear all;
close all;
t=[0:0.01:1];
m=sin(2*pi*t);
hold on;
plot(m,'black');
title('sinc pulse');
xlabel('time');
ylabel('amplitude');
d=2*pi/100;
for n=1:1:100
if n==1
e(n)=m(n);
eq(n)=d*sign(e(n));
mq(n)=eq(n);
else
e(n)=m(n)-mq(n-1);
DIGITAL COMMUNICATION SYSTEMS LABORATORY III B.Tech I Sem
VEMU INSTITUTE OF TECHNOLOGY, DEPT OF E.C.E Page 33
eq(n)=d*sign(e(n));
mq(n)=mq(n-1)+eq(n);
end
end
stairs(mq,'black');
hleg=legend('original signal','stair case approximated signal');
Wave forms:
Result:
0 20 40 60 80 100 120-1.5
-1
-0.5
0
0.5
1
1.5sinc pulse
time
am
plitu
de
original signal
stair case approximated signal