(a christian minority institution)ec 6512 communication system lab manual v semester ece (odd sem...
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PANIMALAR ENGINEERING COLLEGE (A CHRISTIAN MINORITY INSTITUTION)
JAISAKTHI EDUCATIONAL TRUST
ACCREDITED BY NATIONAL BOARD OF ACCREDITATION (NBA)
Bangalore Trunk Road, Varadharajapuram, Nasarathpettai,
Poonamallee, Chennai – 600 123.
DEPARTMENT OF ELECTRONICS &
COMMUNICATION ENGINEERING
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING
EC 6512 COMMUNICATION SYSTEM LAB MANUAL
V SEMESTER ECE
(ODD SEM YEAR 2017-2018)
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DEPARTMENT OF ECE
VISION
To emerge as a centre of excellence in providing quality education and produce
technically competent Electronics and Communication Engineers to meet the needs of
industry and Society.
MISSION
M1: To provide best facilities, infrastructure and environment to its students, researchers and
faculty members to meet the Challenges of Electronics and Communication Engineering
field.
M2: To provide quality education through effective teaching – learning process for their
future career, viz placement and higher education.
M3: To expose strong insight in the core domains with industry interaction.
M4: Prepare graduates adaptable to the changing requirements of the society through life
long learning.
PROGRAMME EDUCATIONAL OBJECTIVES
1. To prepare graduates to analyze, design and implement electronic circuits and systems
using the knowledge acquired from basic science and mathematics.
2. To train students with good scientific and engineering breadth so as to comprehend,
analyze, design and create novel products and solutions for real life problems.
3. To introduce the research world to the graduates so that they feel motivated for higher
studies and innovation not only in their own domain but multidisciplinary domain.
4. Prepare graduates to exhibit professionalism, ethical attitude, communication skills,
teamwork and leadership qualities in their profession and adapt to current trends by
engaging in lifelong learning.
5. To practice professionally in a collaborative, team oriented manner that embraces the
multicultural environment of today’s business world.
PROGRAMME OUTCOMES
1. Engineering Knowledge: Able to apply the knowledge of Mathematics, Science,
Engineering fundamentals and an Engineering specialization to the solution of complex
Engineering problems.
2. Problem Analysis: Able to identify, formulate, review research literature, and analyze
complex Engineering problems reaching substantiated conclusions using first principles of
Mathematics, Natural sciences, and Engineering sciences.
3. Design / Development of solutions: Able to design solution for complex Engineering
problems and design system components or processes that meet the specified needs with
appropriate considerations for the public health and safety and the cultural, societal, and
environmental considerations.
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4. Conduct investigations of complex problems: Able to 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.
5. Modern tool usage: Able to create, select and apply appropriate techniques, resources,
and modern Engineering IT tools including prediction and modeling to complex
Engineering activities with an understanding of the limitations.
6. The Engineer and society: Able to apply reasoning informed by the contextual knowledge
to access societal, health, safety, legal and cultural issues and the consequent
responsibilities relevant to the professional Engineering practice.
7. Environment and sustainability: Able to understand the impact of the professional
Engineering solutions in societal and environmental context, and demonstrate the
knowledge of, and need for sustainable development.
8. Ethics: Able to apply ethical principles and commit to professional ethics and
responsibilities and norms of the Engineering practice.
9. Individual and Team work: Able to function effectively as an individual, and as a
member or leader in diverse teams, and in multidisciplinary settings.
10. Communication: Able to 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.
11. Project Management and Finance: Able to 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.
12. Life – long learning: Able to recognize the needs for, and have the preparation and
ability to engage in independent and life-long learning in the broadest contest of
technological change.
PROGRAMME SPECIFIC OUTCOMES
1. Graduates should demonstrate an understanding of the basic concepts in the primary area
of Electronics and Communication Engineering, including: analysis of circuits containing
both active and passive components, electronic systems, control systems, electromagnetic
systems, digital systems, computer applications and communications.
2. Graduates should demonstrate the ability to utilize the mathematics and the fundamental
knowledge of Electronics and Communication Engineering to design complex systems
which may contain both software and hardware components to meet the desired needs.
3. The graduates should be capable of excelling in Electronics and Communication
Engineering industry/Academic/Software companies through professional careers.
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EC6512 COMMUNICATION SYSTEMS LABORATORY L T P C 0 0 3 2
OBJECTIVES:
The student should be made to:
To visualize the effects of sampling and TDM
To Implement AM & FM modulation and demodulation
To implement PCM & DM
To implement FSK, PSK and DPSK schemes
To implement Equalization algorithms
To implement Error control coding schemes
LIST OF EXPERIMENTS:
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes - Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization – Zero Forcing & LMS algorithms(simulation)
TOTAL: 45 PERIODS
OUTCOMES:
At the end of the course, the student should be able to: CO1:Simulate end-to-end Communication Link
CO2:Demonstrate their knowledge in base band signaling schemes through implementation
FSK, PSK and DPSK
CO3:Apply various channel coding schemes & demonstrate their capabilities towards the
improvement of the noise performance of communication system
CO4:Simulate & validate the various functional modules of a communication system
BRIDGING THE CURRICULUM GAP
Course outcomes CO1-CO4 is satisfied by Anna university syllabus. To bridge the gap
between Anna University and IIT , experiments like ASK, PWM and PAM are implemented
using hardware and Linear delta modulation and OFDM spectrum simulated using Matlab
and Experiments like FM radio receiver, ASK, FSK and BPSK using Software defined Radio
are included from NIT.
- Course Instructors
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INDEX
S.NO
LIST OF EXPERIMENTS
PAGE
NO.
1. AM Modulation and Demodulation 2
2. FM Modulation and Demodulation 8
3. Sampling and Reconstruction 14
4. Time Division Multiplexing 20
5. Simulation of Digital Modulation Techniques-
ASK,FSK,PSK,QPSK,DPSK 24
6. Signal Constellation of BPSK, QPSK & QAM 34
7. Communication Link Simulation using SDR 46
8. Digital Modulation – PSK 48
9. Digital Modulation – QPSK 52
10. Pulse Code Modulation 58
11. Delta and Adaptive Delta Modulation 62
12. Line Coding and Decoding 68
13. Error Control Coding using MATLAB 74
14. Simulation of Equalization Techniques 76
15. Content Beyond Syllabus 82
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LIST OF EXPERIMENTS:
CYCLE I
1. AM Modulation and Demodulation
2. FM Modulation and Demodulation
3. Sampling and Reconstruction
4. Time Division Multiplexing
5. Simulation of Digital Modulation Techniques-
ASK,FSK,PSK,QPSK,DPSK
6. Signal Constellation of BPSK, QPSK & QAM
7. Communication Link Simulation
CYCLE II
8. Digital Modulation – PSK
9. Digital Modulation – QPSK
10. Pulse Code Modulation,
11. Delta and Adaptive Delta Modulation
12. Line Coding and Decoding
13. Error Control Coding using MATLAB
14. Simulation of Equalization Techniques
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CIRCUIT DIAGRAM
AMPLITUDE MODULATION
DEMODULATION
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EXPT.NO.1 AM MODULATION AND DEMODULATION
AIM:
To construct amplitude modulator and demodulator circuit and plot the waveforms.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 Transistor BC 107 1
2 Diode 1N4001 1
3 Capacitors 0.1µF, 0.01µF 2,1
4 Resistors 100K,22K,500Ω,20
0K,10Ω 2, 1each
5 Decade Inductance Box 10 mH 1
6 Function Generators 1 MHz 2
7 CRO 20MHz 1
8 Bread board - 1
9 Regulated Power supply 0-30V 1
THEORY :
Modulation can be defined as the process by which the characteristics of carrier wave
are varied in accordance with the modulating wave (signal). Modulation is performed in a
transmitter by a circuit called a modulator.
Need for modulation is as follows:
Avoid mixing of signals
Reduction in antenna height
long distance communication
Multiplexing
Improve the quality of reception
Ease of radiation.
Amplitude Modulation is the process of changing the amplitude of a relatively high
frequency carrier signal in proportion with the instantaneous value of the modulating signal.
The output waveform contains all the frequencies that make up the AM signal and is used to
transport the information through the system. Therefore the shape of the modulated wave is
called the AM envelope. With no modulating signal the output waveform is simply the carrier
signal. Coefficient of modulation is a term used to describe the amount of amplitude change
present in an AM waveform. There are three degrees of modulation available based on value
of modulation index.
1) Under modulation : m<1, Em < Ec
2) Critical modulation: m-1, Em = Ec
3) Over modulation: m>1, Em > Ec
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MODEL GRAPH:
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Demodulation is the reverse process of modulation and converts the modulated carrier
back to the original information. Demodulation is performed in a carrier by a circuit called a
demodulator.
ADVANTAGES:
1) Relatively inexpensive
2) Low quality form of modulation
DISADVANTAGES:
1) Low efficiency
2) Small operating range
APPLICATION:
1) Commercial broadcasting of both audio and video signals
2) Two way mobile radio communication such as citizen band (CB) radio.
PROCEDURE:
1. Rig up the circuit as per the circuit diagram.
2. Set the carrier signal using function generator and measure the amplitude and time
period.
3. Set the modulating signal and measure the amplitude and time period.
4. Vary the amplitude around the carrier voltage.
5. Note down the maximum (Emax) and minimum (Emin) voltages from the CRO.
6. Calculate the modulation index using the formula.
7. Apply the AM signal to the detector circuit.
8. Observe the amplitude demodulated output on the CRO.
9. Compare the demodulated signal with the original modulating signal (Both must
be same in all parameters). Plot the observed waveforms.
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TABULATION:
INPUT SIGNAL:
Signals Amplitude (V) Time period
(ms) Frequency (KHz)
Modulating signal
Carrier signal
MODULATED SIGNAL:
Emax
(V)
Emin
(V) m = (Emax – Emin)/ (Emax + Emin) %
Type of
modulation
DETECTED SIGNAL:
Amplitude (V) Time period (ms) Frequency (KHz)
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RESULT:
Thus the characteristics of AM Transmitter and Receiver are studied and the
waveforms are observed and plotted.
Questions
1. Define Amplitude Modulation.
A. AM is a process in which the amplitude of the carrier wave is varied in accordance with
some characteristics of the modulating signal.
2. What is the need for Modulation?
A. a) Difficult in transmitting signals at low frequencies.
b) To minimize signal loss.
c) To reduce antenna length.
3. What are the applications of AM?
A. Amplitude modulation is utilized in many services such as television, standard
broadcasting, aids to navigation, telemeter, radar, facsimile etc.
4. What are the different types of AM?
A. Single Side Band, Double Side Band and Vestigial Side Band Modulation are the
different
types of AM.
5. What are the disadvantages of AM?
A. Low efficiency, small operating range, noisy reception.
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BLOCK DIAGRAM
FM MODULATOR AND DEMODULATOR
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EXPT.NO:2 FM MODULATION AND DEMODULATION
AIM:
To plot the modulation characteristics of FM modulator and demodulator and also to
observe and measure frequency deviation and modulation index of FM.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 FM Transmitter and receiver kit 1
2 CRO 20 MHz 1
THEORY:
Frequency modulation is a type of modulation in which the frequency of the high
frequency (carrier) is varied in accordance with the instantaneous value of the modulating
signal.
FREQUENCY DEVIATION f and MODULATION INDEX fm :
The frequency deviation f represents the maximum shift between the modulated
signal frequency, over and under the frequency of the carrier.
2
minmax fff
We define modulation index m f the ratio between f and the modulating frequency f.
f
fm f
FREQUENCY MODULATION GENERATION:
The circuits used to generate a frequency modulation must vary the frequency of a
high frequency signal (carrier) as function of the amplitude of a low frequency signal
(modulating signal). In practice there are two main methods used to generate FM.
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MODEL GRAPH:
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DIRECT METHOD
An oscilloscope is used in which the reactance of one of the elements of the resonant
circuit depends on the modulating voltage. The most common device with variable reactance
is the Varactor or Varicap, which is a particular diode which capacity varies as function of
the reverse bias voltage. The frequency of the carrier is established with AFC circuits
(Automated frequency control) or PLL (Phase locked loop).
INDIRECT METHOD:
The FM is obtained in this case by a phase modulation, after the modulating signal
has been integrated. In this phase modulator the carrier can be generated by a quartz
oscillator, and so its frequency stabilization is easier. In the circuit used for the exercise, the
frequency modulation is generated by a Hartley oscillator, which frequency is determined by
a fixed inductance and by capacity (variable) supplied by varicap diodes.
ADVANTAGES:
1. Noise reduction
2. Improved system fidelity
3. Efficient use of power
DISADVANTAGE:
1. Requires a wider bandwidth
2. Utilizing more complex circuit in both transmitters and receivers.
APPLICATION:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System
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TABULATION:
Signals Amplitude (V)
Time period (ms)
Frequency(KHz)
Modulating signal
Carrier signal
Modulated signal
Tmin= fmax=
Tmax= fmin=
Demodulated signal
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PROCEDURE:
i) Connect the power supply with proper polarity to the kit. While connecting this
ensures that the Power supply is OFF.
ii) Switch on the power supply and carry out the following presetting as shown in
circuit Diagram.
iii) In the FM modulator set the level about 2Vpp and frequency knob to the
minimum and switch on 1500 KHz.
iv) Observe the Fm modulated waveform from the RF/FM output of the FM
modulator measure frequency deviation and modulation index of FM.
v) For demodulation switch on the demodulator and carry out the following
demodulation connection as shown in circuit diagram.
vi) Observe the demodulated waveform and plot the graph.
RESULT:
Thus the modulation characteristics of FM modulator and demodulator are observed
and plotted.
Questions:
1. What is Frequency Modulation?
Frequency modulation (FM) is a technique in which the frequency of the carrier wave is
varied in accordance with the amplitude of the message signal.
3. What is the frequency band for FM radio?
The frequency band for FM radio is about 88 to 108 MHz.
4. What is the bandwidth of FM signal?
Bandwidth of a FM signal may be predicted using:
BW = 2 ( + 1 ) fm; where is the modulation index and fm is the maximum modulating
frequency used.
5.What are the disadvantages of FM?
Compared to AM, the FM signal has a larger bandwidth
6. What are the disadvantages of FM?
High efficiency and better immunity to noise.
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BLOCK DIAGRAM:
CIRCUIT DIAGRAM: (USING MOSFET)
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EXPT.NO. 3 SAMPLING AND RECONSTRUCTION
AIM:
To sample a signal with different sampling frequencies and to reconstruct the same.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT
/ COMPONENT RANGE QUANTITY
1 Sampling trainer kit - 1
2 CRO 20MHz 1
THEORY:
The analog signal can be converted to a discrete time signal by a process called
sampling. The sampling theorem for a band limited signal of finite energy can be stated
as,
” A band limited signal of finite energy, which has no frequency component higher than
W Hz is completely described by specifying the values of the signal at instants of time
separated by 1/2W seconds.‟‟ It can be recovered from knowledge of samples taken at the
rate of 2W per second.
Sampling is the process of splitting the given analog signal into different samples of
equal amplitudes with respect to time. There are two types of sampling namely natural
sampling, flat top sampling. Sampling should follow strictly the Nyquist Criterion i.e. the
sampling frequency should be twice higher than that of the highest frequency signal.
ms ff 2
Where,
sf Minimum Nyquist Sampling rate (Hz)
mf Maximum analog input frequency (Hz).
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TABULATION:
MODULATING SIGNAL:
Amplitude (V) Time period (ms) Frequency (KHz)
SAMPLED SIGNAL:
Amplitude
(V)
Sampling
frequency
(KHZ)
Duty
Cycle (%)
No. of
Samples
Time period (ms)
(for each sample)
Total
Time
period
(ms)
Frequency
(KHz) Ton Toff
RECONSTRUCTED SIGNAL
Amplitude (V) Time period (ms) Frequency (KHz)
Duty cycle calculation:
D = Ton / (Ton + Toff) = ---------- %
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ADVANTAGES:
It can store retrieve and transmit signals without any loss
With higher sampling rate they can relax low pass filter design requirements for
ADC and DAC
PROCEDURE:
1. Give the connections as per the block diagram.
2. Apply the modulating signal and measure its amplitude and time period.
3. Set the sampling frequency to 80 KHz and note down the amplitude and time
period of the sampled signal.
4. Give the sampled signal to the reconstruction circuit and observe the reconstructed
signal.
5. Note down the amplitude and time period of the reconstructed signal.
6. Repeat the same procedure for different sampling frequencies.
7. Plot the above waveforms in the graph.
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MODEL GRAPH:
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RESULT:
Thus the given signal is sampled with different sampling frequencies and the
waveforms are plotted.
Questions:
1. What is aliasing effect?
A. The original analog waveform can be recovered from the PAM type samples simply by
low pass filtering them If fs <fnyquist (2fm) then overlapping of adjacent spectrum
replicates occurs. This is known as aliasing .Due to under- sampling (for f s<2fm) exact
analog waveform cannot be recovered,
2. What is the function of Op-amps in this circuit and what is the effect of frequency of
sampling signal?
A. Op-amps acts as voltage followers, if the f s<2fm , then distorted waveform is
Observed, so to recover the exact signal the sampling signal frequency should be
maintained greater than or equal to the 2fm.
3. What are the different types of sampling?
A. Instantaneous sampling, Natural sampling and Flat top sampling.
4. State Sampling Theorem.
A. The sampling theorem for a band limited signal of finite energy can be stated as,” A
Band limited signal of finite energy, which has no frequency component higher than W
Hz is completely described by specifying the values of the signal at instants of time
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BLOCK DIAGRAM:
Patch cord
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EXPT.NO.4 TIME DIVISION MULTIPLEXING
AIM:
To perform four channel Time Division multiplexing and De multiplexing.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT
/ COMPONENT RANGE QUANTITY
1 Time Division Multiplexing kit - 1
2 CRO 20MHz 1
THEORY:
In PAM, PPM the pulse is present for a short duration and for most of the time
between the two pulses no signal is present. This free space between the pulses can be
occupied by pulses from other channels. This is known as Time Division Multiplexing. Thus,
time division multiplexing makes maximum utilization of the transmission channel. Each
channel to be transmitted is passed through the low pass filter. The outputs of the low pass
filters are connected to the rotating sampling switch (or) commutator.
It takes the sample from each channel per revolution and rotates at the rate of f s. Thus
the sampling frequency becomes fs the single signal composed due to multiplexing of input
channels. These channels signals are then passed through low pass reconstruction filters. If
the highest signal frequency present in all the channels is fm, then by sampling theorem, the
sampling frequency fs must be such that fs≥2fm. Therefore, the time space between successive
samples from any one input will be Ts=1/fs, and Ts1/2fm.
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TABULATION
1. TRANSMITTED SIGNALS: 3. RECEIVED SIGNALS:
2. SAMPLED SIGNAL
MODEL GRAPH:
Channel Amplitude
(V)
Time
period
(ms)
Frequency
(KHz)
Channel Amplitude
(V)
Time
period
(ms)
Frequency
(KHz)
Channel Amplitude
(V)
No.of
Samples
Time period (ms)
(for each sample) Total Time
period(ms)
Frequency
(KHz) Ton Toff
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PROCEDURE:
1. Give the connections as per the block diagram.
2. Apply the four input sinusoidal signals of different frequency to four channels and
measure the amplitude and time period of each signal.
3. Observe and measure the amplitude and frequency of the sampled signal for each
channel individually.
4. Then observe the multiplexed waveform in the CRO.
5. Apply the multiplexed signal to the demultiplexer circuit and observe the original
signals transmitted.
6. Measure the amplitude and time period of demultiplexed signal for each channel
individually.
7. Plot all the waveforms in the graph.
RESULT:
Thus the Time division multiplexing and demultiplexing waveforms are obtained.
Questions
1. What is multiplexing?
A. It is a process in which a single transmission channel is shared by a no. of base band
signals.
2. What is TDM?
A. In TDM, different time intervals rather than frequencies are allotted to different
signals. During these intervals these signals are sampled and transmitted. Thus, this
system transmits information intermittently rather than continuously.
3. What are the advantages of TDM?
A. a)Low cost equipment b) Ease of installation and maintenance c) Low and constant
delay d) unsurpassed voice quality and e) standards based.
4. What are the applications of TDM?
A. In telecommunications and signal processing applications.
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SIMULATED WAVEFORM
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EXPT.NO.5 SIMULATION OF DIGITAL MODULATION TECHNIQUES
1. Simulation of ASK
AIM:
To implement ASK using MATLAB.
SOFTWARE REQUIRED:
MATLAB
PROGRAM:
clc;
t=0:0.0001:0.15;
m = square(2*pi*10*t);
c = sin(2*pi*60*t);
y1=(m.*c);
for i = 1:1500
if(m(i)==1)
y1(i) = c(i);
else
y1(i) = 0;
end
end
figure(1)
subplot(311);
plot(m);
subplot(312);
plot(c);
subplot (313);
plot (y1);
RESULT:
Thus ASK was implemented using MATLAB.
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SIMULATED WAVEFORM
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2. Simulation of FSK
AIM:
To implement FSK using MATLAB.
SOFTWARE REQUIRED:
MATLAB
PROGRAM:
clc;
t = 0:0.0001: 0.15;
m = square (2*pi*10*t);
c1 = sin (2*pi*60*t);
c2 = sin (2*pi*120*t);
s1 = (m.*c1);
for i = 1 : 1500
if(m(i)==1)
s1(i)=c2(i);
else
s1(i)=c1(i);
end
end
figure(2);
subplot(411);
plot(m);
subplot(412);
plot(c1);
subplot(413);
plot(c2);
subplot(414);
plot(s1);
RESULT:
Thus FSK was implemented using MATLAB.
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SIMULATED WAVEFORM
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3. Simulation of PSK
AIM:
To implement PSK using MATLAB.
SOFTWARE REQUIRED:
MATLAB
PROGRAM:
clc;
c11 = sin(2*pi*60*t);
t = 0:0.0001:0.15;
m = square (2*pi*10*t);
c22 = sin((2*pi*60*t)+ pi);
s2 = (m.*c11);
for i = 1:1500
if(m(i)==1)
s2(i)=c11(i);
else
s2(i)=c22(i);
end
end
figure(3);
subplot(411);
plot(m);
subplot (412);
plot(c11);
subplot (413);
plot (c22);
subplot(414);
plot(s2);
RESULT:
Thus PSK was implemented using MATLAB.
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SIMULATED WAVEFORM
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4. Simulation of QPSK
AIM:
To implement QPSK using MATLAB.
SOFTWARE REQUIRED: MATLAB
PROGRAM:
clc; clear all; close all;
Tb=1; t=0:(Tb/100):Tb; fc=1;
c1=sqrt(2/Tb)*cos(2*pi*fc*t);
c2=sqrt(2/Tb)*cos(2*pi*fc*t);
N=8; m=rand(1,N);
t1=0; t2=Tb;
for i=1:2:(N-1)
t=[t1:(Tb/100):t2];
if m(i)>0.5
m(i)=1;
m_s= ones (1,length(t));
else
m(i)=0;
m_s= -1*ones (1,length(t));
end
odd_sig(i,:)=c1.*m_s;
if m(i+1)>0.5
m(i+1)=1;
m_s=ones(1,length(t));
else
m(i+1)=0;
m_s=-1*ones(1,length(t));
end
even_sig(i,:)=c2.*m_s; qpsk=odd_sig+even_sig;
subplot(3,2,4);plot(t,qpsk(i,:));
title('qpsk signal');xlabel('t--->');ylabel('s(t)');
grid on; hold on;
t1=t1+(Tb+.01); t2=t2+(Tb+.01);
end
hold off ;subplot(3,2,1);stem(m);
title('binary data bits'); xlabel('n--->');ylabel('b(n)');
grid on; subplot(3,2,2);plot(t,c1);
title('carrier signal-1'); xlabel('t--->');ylabel('c1');
grid on; subplot(3,2,3);plot(t,c2);
title('carrier signal-2'); xlabel('t--->');ylabel('c2');
grid on;
RESULT:
Thus QPSK was implemented using MATLAB.
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SIMULATED OUTPUT:
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5. Simulation of DPSK
AIM:
To implement DPSK using MATLAB.
SOFTWARE REQUIRED:
MATLAB
PROGRAM:
clc; clear all; close all;
N=10^4
rand('state',100); rand('state',200);
ip=rand(1,N)>0.5,ipD=mod(filter(1,[1 -1],ip),2);
s=2*ipD-1;
n=1/sqrt(2)*[randn(1,N)+j*randn(1,N)]; Eb_N0_db=[-3:10];
for ii=1:length(Eb_N0_db)
y=s+10^(-Eb_N0_db(ii)/20)*n;
ipDHat_coh=real(y)>0;
ipHat_coh=mod(filter([1 -1],1,ipDHat_coh),2);
nErr_dbpsk_coh(ii)=size(find([ip-ipHat_coh]),2);
end
simBer_dbpsk_coh=nErr_dbpsk_coh/N;
theoryBer_dbpsk_coh=erfc(sqrt(10.^(Eb_N0_db/10))).*(1-5*erfc(sqrt(10.^(Eb_N0_db/10))));
close all;
figure
semilogy(Eb_N0_db,theoryBer_dbpsk_coh,'b.-');
hold on;
semilogy(Eb_N0_db,simBer_dbpsk_coh,'mx-');
aixs([-2 10 10^-6 0.5]);
grid on;
legend('theory','simulation');
xlabel('Eb/N0,db');ylabel('bit error rate');
title('bit error probability curve for coherent demodulation of dbpsk');
RESULT:
Thus DPSK was implemented using MATLAB.
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OUTPUT:
BPSK
-5 0 5-5
-4
-3
-2
-1
0
1
2
3
4
5Q
uadra
ture
In-Phase
constellation diagram BPSK
Received signal
signal constellation
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EXPT.NO. 6 SIGNAL CONSTELLATION OF BPSK, QPSK & QAM
AIM:
To plot the constellation diagram of digital modulation system BPSK, QPSK & QAM
using MATLAB.
SOFTWARE USED:
MATLAB
THEORY:
A constellation diagram is a representation of a signal modulated by an arbitrary digital
modulation scheme. It displays the signal as a two dimensional scatter diagram in the complex
plane at symbol sampling instants. It can also be viewed as the possible symbols that may be
selected by a given modulation scheme as points in the complex plane.
PROGRAM: BPSK
clc;
clear all;
close all;
M=2;
k=log2(M);
n=3*1e5;
nsamp=8;
X=randint(n,1);
xsym = bi2de(reshape(X,k,length(X)/k).','left-msb');
Y_psk= modulate(modem.pskmod(M),xsym);
Ytx_psk = Y_psk;
EbNo=30;
SNR=EbNo+10*log10(k)-10*log10(nsamp);
Ynoisy_psk = awgn(Ytx_psk,SNR,'measured');
Yrx_psk = Ynoisy_psk;
h1=scatterplot(Yrx_psk(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_psk(1:5e3),1,0,'k*',h1);
title('constellation diagram BPSK');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;
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QPSK
-5 0 5-5
-4
-3
-2
-1
0
1
2
3
4
5
Quadra
ture
In-Phase
constellation diagram 16 PSK
Received signal
signal constellation
QAM
-5 0 5-5
-4
-3
-2
-1
0
1
2
3
4
5
Quadra
ture
In-Phase
constellation diagram 16 QAM
Received signal
signal constellation
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Program for QPSK & QAM:
clc;
clear all;
close all;
M=16;
k=log2(M);
n=3*1e5;
nsamp=8;
X=randint(n,1);
xsym = bi2de(reshape(X,k,length(X)/k).','left-msb');
Y_qam= modulate(modem.qammod(M),xsym);
Y_qpsk= modulate(modem.pskmod(M),xsym);
Ytx_qam = Y_qam;
Ytx_qpsk = Y_qpsk;
EbNo=30;
SNR=EbNo+10*log10(k)-10*log10(nsamp);
Ynoisy_qam = awgn(Ytx_qam,SNR,'measured');
Ynoisy_qpsk = awgn(Ytx_qpsk,SNR,'measured');
Yrx_qam = Ynoisy_qam;
Yrx_qpsk = Ynoisy_qpsk;
h1=scatterplot(Yrx_qam(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_qam(1:5e3),1,0,'k*',h1);
title('constellation diagram 16 QAM');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;
h2=scatterplot(Yrx_qpsk(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_qpsk(1:5e3),1,0,'k*',h2);
title('constellation diagram 16 PSK');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;
RESULT:
Thus the constellation diagrams of digital modulation system BPSK, QPSK & QAM are
simulated & plotted in MATLAB.
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INTRODUCTION TO SDR KIT
What is Software defined radio (SDR)?
Software defined radio is defined as an environment where Hardware and Software are
different parts allows user to implement the operating functions of hardware through a
modifiable software. Complete design produces a radio which can receive and transmit widely
different radio protocols (sometimes referred to as waveforms) based solely on the software
used.
Where SDR can be used?
Due to its wide RF range it covers a wide range of applications including high frequency
communications, FM and TV broadcast, cellular, Wi-Fi, ISM, and lot more.
Starting from simple experiments, it makes you grow in experience and complexity up to being
able to deal with competence and master the fundamental elements which makes the Software
Based Radio.
FEATURES
• RFCoverage from70MHz – 6 GHz RF
• GNU Radio and open BTS support through the open source USRP Hardware Driver
• USB 3.0 High speed interface (Compatible with USB 2.0)
• Flexible rate 12 bit ADC/DAC
• 1TX, 1 RX, Half or Full Duplex
• Xilinx Spartan 6 XC6SLX75 FPGA
• Up to 56 MHz of real-time bandwidth
Power
• DC Input: 6V
SOFTWARE DESCRIPTION
What is GNU Radio?
GNU Radio is a software library, which can be used to develop complete applications for radio
engineering and signal processing.
Introduction
GNU Radio is a free and open-source software development toolkit that provides signal
processing blocks to implement software radios. It can be used with readily-available low-cost
external RF hardware to create software-defined radios, or without hardware in a simulation-like
environment.
GNU Radio is licensed under the GNU General Public License (GPL) version 3. All of the code
is copyright of the Free Software Foundation. While all the applications are implemented using
python language while critical signal processing path is done using C++ language.
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PROCEDURE TO WORK ON GNU Radio Companion: GNU Radio Companion (GRC) is a graphical user interface that allows you to build GNU Radio
flow graphs. It is an excellent way to learn the basics of GNU Radio. This is the first in a series
of tutorials that will introduce you to the use of GRC.
Procedure for Amplitude modulation:
STEP 1:Click on GRC.
STEP 2: Click on options and name the title and change generate options as WX GUI.
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STEP3: Click variable and change ID and value.
STEP 4: Press control+F and search for signal source.
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STEP 5: Place the signal source for message signal as amplitude modulation.
STEP 6: Change the properties in signal source as (i) Output Type: Float
(ii)Waveform: Cosine
(iii)Frequency: 100
(iv)Amplitude: 2 and
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STEP 7: Place another signal source for carrier signal in amplitude modulation.
STEP 8: Change properties in signal source as (i) Output type: float
(ii) Waveform: Sine
(iii) Frequency: 100K
(iv) Amplitude: 2
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STEP 9: Press control + F and search Multiply block.
STEP 10: Place Multiply for multiply the message signal and carrier signal.
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STEP 11: Change properties in multiply as (i) ID Type: Float
(ii)Num Inputs: 2
STEP 12: Press Control + F and search for scope sink and Place WX GUI Scope sink.
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STEP 13: Change the properties in Wx GUI scope sink as (i) Type: Float
(ii)Num input: 2
STEP 14: Connect wires of signal source to multiply and connect to WX GUI scope sink.
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STEP 15: Click Run and stop.
OUTPUT WAVEFORM:
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EXPT.NO.7 COMMUNICATION LINK SIMULATION USING SDR
AIM:
To construct an Amplitude modulator and demodulator and using SDR
TRAINER KIT.
EQUIPMENTS REQUIRED:
SDR Trainer Kit -1
SMA Connector-1
USB device -1
THEORY:
AMPLITUDE MODULATION
Amplitude modulation is the process of changing the amplitude of a relatively high
frequency carrier signal in proportion with the instantaneous value of the modulating signal.
BLOCK DIAGRAM:
RESULT:
Thus the Amplitude modulation was studied using SDR kit.
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BLOCK DIAGRAM:
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EXPT.NO.8 DIGITAL MODULATION – PSK
AIM:
To generate Phase Shift Keying signal and plot the graph.
EQUIPMENTS/COMPONENTS REQUIRED:
S.NO
COMPONENTS / EQUIPMENTS
QUANTITY
1. Phase shift keying transmitter kit 1
2. CRO 1
3. Function generator 1
4. Patch chords Few
THEORY:
To facilitate the transmission of a signal over a communication bandwidth, a simple
modulation of digital technique called phase shift keying is adopted, in which the binary signals
symbol „0‟ and symbol „1‟ are transmitted with a phase shift with respect to each other.
At the transmitter side, the message signal which is in analog form is converted to digital
type and is modulated through a sinusoidal carrier frequency. The transmitter output will be a
signal in which logic „1‟ and logic „0‟ are represented by an 1800
phase.
There are different form of PSK such as BPSK, QPSK etc., At the receiver side using
threshold device, the received signal is converted into either logic „1‟ or logic „0‟.
APPLICATION:
Wireless LAN
RFID
Bluetooth communication
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MODEL GRAPH
TABULATION
SIGNAL AMPLITUDE
(V)
TIMEPERIOD
(µs)
FREQUENCY
(KHz)
Clock
Sin 2
Sin 3
Control Input
PSK Modulated output
PSK Demodulated output
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PROCEDURE:
1. The connections are made as per the block diagram.
2. The message signal is applied to the input and also the carrier from function generator.
3. The PSK waveform is obtained.
4. Tabulate the Amplitude and time period.
5. Plot the Graph.
RESULT:
Thus the Phase Shift Keying waveform is obtained and plotted.
QUESTIONS:
1.What are the advantages of BPSK?
BPSK has a bandwidth which is lower than of BFSK is the best of all
systems in the presence of noise. It gives the minimum possibility of error
and it has very good noise immunity.
2.What are the advantages of differential phase shift keying?
i.No need to generate the carrier at the receiver end. This means that
complicated circuitry for generation of local carrier is avoided.
ii.The bandwidth required for DPSK is less compared to binary PSK.
3. What are the disadvantages of differential phase shift keying?
The probability of error is high compared to binary PSK.
4.Why is PSK always preferable over ASK in coherent detection?
ASK has amplitude variations, hence noise interference is more,PSK method
has less noise interference. It is always preferable.
5. What is signal constellation diagram?
Signal constellation refers to a set of possible message points.
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BLOCK DIAGRAM
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EXPT.NO.9 DIGITAL MODULATION – QPSK
AIM:
To generate Quadrature Phase Shift Keying signal and plot the graph.
EQUIPMENTS/COMPONENTS REQUIRED:
S.NO
COMPONENTS / EQUIPMENTS
QUANTITY
1. QPSK transmitter kit 1
2. CRO 1
3. Function generator 1
4. Patch chords Few
THEORY:
In pass band digital communication techniques, there are three basic techniques of
modulation. They are PSK, ASK, FSK. The basic form of phase shift keying is binary phase shift
keying abbreviated as BPSK. The major disadvantages of BPSK are that, it occupies a much
large bandwidth and each and every bit is modulated by phase shifts.
In order to obtain an efficient usage of channel bandwidth Quadrature phase shift keying
techniques is introduced in which there is a phase shift which occurs for a set of bits which is
also called as Dibits. Thus, the phase shift occurs for two bits in sequence and the phase shift
generally follows the Gray code sequence.
The QPSK of two bits is obtained by adding the odd position bits and BPSK of even
position bits and producing QPSK. The Dibits are 00,10,11,01. They have a phase shift of π/4 ,
3π/4, 5π/4, 7π/4 respectively. Thus, the QPSK signal is obtained. The main advantage is that it
utilizes efficiently the bandwidth of transmission channel.
APPLICATION:
It is widely used in satellite broadcasting
It is used in streaming SD channels and some HD CHANNELS
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MODEL GRAPH
QPSK-MODULATION
QPSK-DEMODULATION
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PROCEDURE:
1. The connections are made as per the block diagram.
2. The modulating inputs and the in phase and Quadrature component carriers are given as
input.
3. QPSK wave is obtained.
4. Tabulate the amplitude and time period of QPSK.
5. Plot the graph.
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TABULATION:
SIGNAL
AMPLITUDE
(V)
TIMEPERIOD
(ms)
FREQUENCY
(KHz)
TON
ms
TOFF
ms
Data in
Q bit
I bit
Sin 1
Sin 2
Sin 3
Sin 4
Modulated
output
Clock
Demodulated
output
PHASOR DIAGRAM
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RESULT:
Thus the QPSK wave is obtained and the waveform is plotted.
QUESTIONS:
1.What are the advantages of QPSK as compared to BPSK?
For the same bit error, the bandwidth required by QPSK is reduced to half
as compared to BPSK.
2.List the advantages of Passband transmission.
a. Long distance.
b. Analog channels can be used for transmission.
c. Multiplexing techniques can be used for bandwidth conservation.
d. Transmission can be done by using wireless channel also.
3.List the requirements of Passband transmission.
i.Maximum data transmission rate.
ii.Minimum probability of symbol error.
iii.Minimum transmitted power.
4. Highlight the major difference between a QPSK signal and a MSK signal.
i. QPSK is a phase modulation
ii. MSK is frequency modulation
iii. Band width of QPSK is Fb where as MSK is 1.5 Fb
5.Define QPSK
In QPSK (Quadriphase – Shift Keying), the phase of the carrier takes on one
of the four equally spaced values such as 4
7and
4
5,
4
3,
4
as given by
.Tt04
)1i2(tf2cos(T
E2)t(S ci
0 elsewhere.
1
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BLOCK DIAGRAM:
Analog Input
QUANTIZED PAM DIGITALLY ENCODED
SIGNAL
Demodulated
output
MODEL GRAPH:
SAMPLER
ANALOG TO DIGITAL CONVERTER
QUANTIZER ENCODER
DE -QUANTIZER
DECODER
FILTER
PCM
OUTPUT
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EXPT.NO.10 PULSE CODE MODULATION
AIM:
To obtain Pulse Code Modulated and demodulated signals using PCM trainer kit.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 PCM trainer kit - 1
2 CRO 10 MHz 1
THEORY:
Pulse code modulation is known as digital pulse modulation technique. It is the process
in which the message signal is sampled and the amplitude of each sample is rounded off to the
nearest one of the finite set of allowable values. It consists of three main parts transmitter,
transmitter path and receiver. The essential operation in the transmitter of a PCM system are
sampling, Quantizing and encoding. The band pass filter limits the frequency of the analog input
signal. The sample and hold circuit periodically samples the analog input signal and converts
those to a multi level PAM signal. The ADC converts PAM samples to parallel PCM codes
which are converted to serial binary data in parallel to serial converter and then outputted on the
transmission line as serial digital pulse. The transmission line repeaters are placed at prescribed
distance to regenerate the digital pulse.
In the receiver serial to parallel converter converts serial pulse received from the
transmission line to parallel PCM codes. The DAC converts the parallel PCM codes to multi
level PAM signals. The hold circuit is basically a Low Pass Filter that converts the PAM signal
back to its original analog form.
ADVANTAGES:
1. Secrecy
2. Noise resistant and hence free from channel interference
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TABULATION:
TRANSMITTED SIGNAL:
Amplitude (V) Time period (ms) Frequency (KHz)
SAMPLED SIGNAL:
Channel Amplitude(V)
No. of
samples
Time period (ms)
(for each sample)
Total Time
Period
(ms)
Frequency
(KHz)
Ton Toff
RECEIVED SIGNAL:
Amplitude (V) Time period (ms) Frequency (KHz)
PCM OUTPUT:
DC Voltage
(V)
Encoded values
D6 D5 D4 D3 D2 D1 D0
-5
-4
-3
-2
-1
0
1
2
3
4
5
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DISADVANTAGES:
1. Requires more bandwidth
APPLICATION:
1. Compact DISC for storage
2. Military Applications.
PROCEDURE:
1. Give the connections as per the block diagram.
2. Measure the amplitude and time period of the input signal.
3. Measure the amplitude and time period of the sampled signal.
4. Apply the input signal to the PCM kit and observe and measure the PCM output.
5. Plot the waveforms in the graph.
RESULT:
Thus the Pulse Code Modulated signals are obtained and the waveforms are plotted.
Questions:
1. What is the need of parallel to serial converter?
A. To transmit all the bits in one channel.
2. What is the use of Companding?
A. Companding is used to overcome quantizing noise in PCM.
3. What are the applications of PCM?
A. Because of high immune to noise it can be used for storage systems in CD recording.
4. What should be the minimum B.W. required to transmit a PCM channel?
A. BT = vW where v = no. of bits used to represent one pulse, W = Maximum signal
frequency.
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BLOCK DIAGRAM
BLOCK DIAGRAM FOR DELTA MODULATION AND DEMODULATION
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EXPT. NO. 11 DELTA AND ADAPTIVE DELTA MODULATION
AIM:
To obtain Delta Modulated and Adaptive Delta modulated waveforms.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 Delta Modulation & Adaptive
Delta modulationTrainer kit - 1
2 CRO 10 MHz 1
3 Patch cords - 10
4 Power Supply (0-30) V 1
THEORY:
Delta modulation uses a single bit PCM code to achieve digital transmission of analog
signal. With conventional PCM, each code is a binary representative of both the sign and
magnitude of a particular sample. The algorithm of delta modulation is simple if the current
sample is smaller than the previous sample a logic0 is transmitted. If the current sample is larger
than the previous sample a logic 1 is transmitted.
ADVANTAGES:
Simple system/circuitry
Cheap
Single bit encoding allows us to increase the sampling rate or to transmit more
information at some sampling rate for the given system BW.
DISADVANTAGE :
Noise and distortion.
Major drawback is that it is unable to pass DC information.
APPLICATION:
Digital voice storage
Voice transmission
Radio communication devices such TV remotes.
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MODEL GRAPH:
TABULATION:
DELTA MODULATION
AMPLITUDE (V)
TIME PERIOD (ms)
FREQUENCY
(HZ)
Input Signal
Integrator 1 output
Sampler output
Integrator 3 output
Filter output
Demodulated output
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THEORY:
Adaptive delta modulation is delta modulation system where the step size of DAC is
automatically varied , depending on the amplitude characteristics of the analog input signal. A
common algorithm for an adaptive delta modulator is when three consecutive 1s or 0s occur, the
step size of the DAC is increased or decreased by a factor of 1.5
APPLICATION:
Audio communication system
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MODEL GRAPH:
TABULATION:
ADAPTIVE DELTA MODULATION
TYPE OF SIGNAL
AMPLITUDE (V)
TIME PERIOD (ms)
FREQUENCY
(HZ)
Input Signal
Integrator 2 output
Sampler output
Integrator 3 output
Filter output
Demodulated output
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PROCEDURE:
1. Connections are to be given as per the block diagram.
2. Observe the modulated waveforms.
3. Measure the amplitude and time period of both the waveforms.
4. Plot the graph.
5. Repeat the above procedure for adaptive delta modulation also.
RESULT:
Thus Delta Modulated and Adaptive Delta Modulated waveforms are obtained.
Questions
1. What is Delta Modulation?
A. Delta modulation is a system of digital modulation developed after pulse
modulation. In this system, at each sampling time, say the Kth
sampling time, the
difference between the sample value at sampling time K and the sample value at the
previous sampling time (K-1) is encoded into just a single bit.
2. What are the drawbacks of Delta Modulation?
A. Slope overload distortion and Granular noise effect are the drawbacks of Delta
Modulation.
3. What are the advantages of Delta Modulation?
A. The advantages of Delta Modulation are simple system/circuitry; cheap, single bit
encoding allows us to increase the sampling rate or to transmit more information at
some sampling rate for the given system BW.
4. Can DC information be passed using Delta Modulation?
A. No, DC information cannot be passed using Delta Modulation.
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BLOCK DIAGRAM
Panim
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EXPT. NO. 12 LINE CODING AND DECODING
AIM:
To analyze line coding and decoding techniques.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT
/ COMPONENT RANGE QUANTITY
1 Line coding & decoding kit - 1
2 Connecting plugs - 1
3 CRO 10 MHz 1
THEORY:
NON-RETURN TO ZERO signal are the easiest formats that can be generated. These
signals do not return to zero with the clock. The frequency component associated with these
signals are half that of the clock frequency. The following data formats come under this
category. Non-return to zero encoding is commonly used in slow speed communications
interfaces for both synchronous and asynchronous transmission. Using NRZ, logic 1 bit is sent as
a high value and a logic 0 bit is sent as a low value.
a) NON-RETURN TO ZERO-LEVEL (NRZ-L)
This is the most extensively used waveform in digital logics. All „ones‟ are represented by
„high‟ and all „zeros‟ by „low‟. The data format is directly available at the output of all digital
data generation logics and hence very easy to generate. Here all the transitions take place at the
rising edge of the clock.
b) NON-RETURN TO ZERO-MARK (NRZ-M)
These waveforms are extensively used in tape recording. All „ones‟ are marked by change in
levels and all‟zeros‟ by no transitions, and the transitions take place at the rising edge of the
clock.
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LINE CODING WAVE FORM:
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c) NON-RETURN TO ZERO-SPACE (NRZ-S)
This type of waveform is marked by change in levels for „zeros‟ and no transition for „ones‟
and the transitions take place at the rising edge of the clock. This format is also used in magnetic
tape recording.
d) UNIPOLAR AND BIPOLAR
Unipolar signals are those signals, which have transition between 0 to +VCC. Bipolar
signals are those signals, which have transition between +VCC to –VCC.
e) BIPHASE – LINE CODING(BIPHASE -L):
With the Biphase – L one is represented by a half bit wide pulse positioned during the
first half of the bit interval and a zero is represented by a half bit wide pulse positioned
during the second half of the bit interval.
f) BIPHASE MARK CODING(BIPHASE-M):
With the Biphase-M, a transition occurs at the beginning of every bit interval. A „one‟ is
represented by a second transition, half bit later, whereas a zero has no second transition.
g) BIPHASE SPACE CODING(BIPHASE-S):
With a Biphase-S, a transition occurs at the beginning of every bit interval. A „zero‟ is
marked by a second transition, one half bit later; „one‟ has no second transition.
h) RETURN TO ZERO SIGNALS:
These signals are called “Return to Zero signals” since they return to „zero‟ with the
clock. In this category, only one data format, i.e, the unipolar return to zero(URZ); With the
URZ a „one‟ is represented by a half bit wide pulse and a „zero‟ is represented by the absence
of pulse.
i) MULTILEVEL SIGNALS:
Multilevel signals use three or more levels of voltages to represent the binary digits, „one‟
and „zero‟ – instead of normal „highs‟ and „lows‟ Return to zero – alternative mark inversion
(RZ - AMI) is the most commonly used multilevel signal. This coding scheme is most often
used in telemetry systems. In this scheme, „one‟ are represented by equal amplitude of
alternative pulses, which alternate between a +5 and -5. These alternating pulses return to 0
volt, after every half bit interval. The „Zeros‟ are marked by absence of pulses.
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TABULATION:
ONE
ZERO
TON(ms) TOFF(ms) TON(ms) TOFF(ms)
Clock
Data Input
NRZ-L
NRZ-M
NRZ-S
BIO-L
BIO-M
BIO-S
URZ
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PROCEDURE:
1. Connect power supply in proper polarity to the kits DCL-05 and DCL-06 and switch it on.
2. Connect CLOCK and DATA generated on DCL-05 to CODING CLOCK IN and DATA
INPUT respectively by means of the patch-chords provided.
3. Connect the coded data NRZ-L on DCL-05 to the corresponding DATA INPUT NRZ-L, of
the decoding logic on DCL-06.
4. Keep the switch SW2 for NRZ-L to ON position for decoding logic as shown in the block
diagram.
5. Observe the coded and decoded signal on the oscilloscope.
6. Connect the coded data NRZ-M on DCL-05 to the corresponding DATA INPUT NRZ-M,
of the decoding logic on DCL-06.
7. Keep the switch SW2 for NRZ –M to ON position for decoding logic as shown in the block
diagram.
8. Observe the coded and decoded signal on the oscilloscope.
9. Connect the code data NRZ-S on DCL-05 to the corresponding DATA INPUT NRZ-S, of
the decoding logic on DCL-06.
10. Keep the switch SW2 for NRZ-S to ON position for decoding logic as shown in the block
diagram.
11. Observe the coded and decoded signal on the oscilloscope.
12. Use RESET switch for clear data observation if necessary.
13. Unipolar to Bipolar/Bipolar to Unipolar:
a. connect NRZ-L signal from DCL-05 to the input post IN Unipolar to Bipolar and
Observe the Bipolar output at the post OUT.
b. Then connect bipolar output signal to the input post IN of Bipolar to Unipolar and
observe Unipolar out at post OUT.
RESULT:
Thus the line coding and decoding techniques were analyzed and observed and the graph
is plotted.
Questions 1. What is a digital signal?
A. A digital signal is a discontinuous signal that changes from one state to another in
discrete steps. A popular form of digital modulation is binary, or two levels, digital
modulation.
2. What is Line Coding?
A. Line coding is the process of arranging symbols that represent binary data in a
particular pattern for transmission.
3. What are the common types of line coding used in communication?
A. The most common types of line coding used in fiber optic communications include non-
return-to-zero (NRZ), return-to-zero (RZ), and biphase, or Manchester.
4. In NRZ code, does the presence of a high-light level in the bit duration represent a binary
1 or a binary 0?
A. The presence of a high-light level in the bit duration represents a binary 1, while a low-
light level represents a binary 0.
5. How can the loss of timing occur in NRZ line coding?
A. loss of timing may result if long strings of 1s and 0s are present causing a lack of level
Transitions.
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OUTPUT:
COMPUTATION OF CODE VECTORS FOR A CYCLIC CODE
Msg=
1 0 0 1
1 0 1 0
1 0 1 1
Code =
1 1 0 1 0 0 1
0 1 1 1 0 1 0
0 0 0 1 0 1 1
SYNDROME DECODING
Recd=
1 0 1 1 1 1 0
Syndrome=7(decimal), 1 1 1(binary)
Parmat=
1 0 0 1 0 1 1
0 1 0 1 1 1 0
0 0 1 0 1 1 1
Corrvect=
0 0 0 0 0 1 0
Correctedcode=
1 0 1 1 1 0 0
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EXPT.NO. 13 ERROR CONTROL CODING USING MATLAB
AIM:
a. To generate parity check matrix & generator matrix for a (7,4) Hamming code.
b. To generate parity check matrix given generator polynomial g(x) = 1+x+x3.
c. To determine the code vectors.
d. To perform syndrome decoding
PROGRAM:
Generation of parity check matrix and generator matrix for a (7,4) Hamming code.
[h,g,n,k] = hammgen(3);
Generation of parity check matrix for the generator polynomial g(x) = 1+x+x3.
h1 = hammgen(3,[1011]);
Computation of code vectors for a cyclic code
clc;
close all;
n=7;
k=4;
msg=[1 0 0 1; 1 0 1 0; 1 0 1 1];
code = encode(msg,n,k,'cyclic');
msg
code
Syndrome decoding
clc;
close all;
q=3;
n=2^q-1;
k=n-q;
parmat = hammgen(q); % produce parity-check matrix
trt = syndtable(parmat); % produce decoding table
recd = [1 0 1 1 1 1 0 ] %received vector
syndrome = rem(recd * parmat',2);
syndrome_de = bi2de(syndrome, 'left-msb'); %convert to decimal
disp(['Syndrome = ',num2str(syndrome_de),.....
' (decimal), ',num2str(syndrome),' (binary) ']);
corrvect = trt(1+syndrome_de, :);%correction vector
correctedcode= rem(corrvect+recd,2);
parmat
corrvect
correctedcode
RESULT:
Thus encoding and decoding of block codes are performed using MATLAB.
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SIMULATED OUTPUT:
Symbol error rate with equalizer: 0
Symbol error rate without equalizer: 0.3310
-2 -1 0 1 2-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
Quadra
ture
In-Phase
Scatter plot
fitered signal
equalized signal
ideal signal constellation
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EXPT.NO. 14 SIMULATION OF EQUALIZATION TECHNIQUES
1. Simulation of Zero Forcing Equalizer.
AIM:
To simulate the Zero Forcing Equalizer using MATLAB.
SOFTWARE USED: MATLAB
THEORY:
Equalizer can be employed to mitigate the ISI for a smooth recovery of transmitted
symbols and to improve the receiver performance
Zero forcing (or) linear equalizer which processes the incoming signal with a linear filter. It is
classified into two
(a) Symbol spaced equalizer
(b) Fractionally spaced equalizer
Symbol spaced equalizer:
A symbol spaced linear equalizer consist of a tapped delay line that stores samples from the input
signal. Here the sample rates of both input & output signals are equal to 1/T.
Fractionally spaced equalizer:
A Fractionally spaced linear equalizer is similar to a symbol spaced equalizer,but the former
receives K input samples before it produces one output sample & updates the weights, where K
is an integer. Here the output sample rates is 1/T,while that of input sample is K/T.
PROGRAM
clc;clear all;close all;
M=4;
msg=randint(1500,1,M);
modmsg=pskmod(msg,M);
sigconst=pskmod([0:M-1],M);
trainlen=500;
chan=[.986;.845;.237;.123+.31i];
filtmsg=filter(chan,1,modmsg);
eqobj =lineareq(8,lms(0.01),sigconst,1);
[symbolest,yd]=equalize(eqobj,filtmsg,modmsg(1:trainlen));
h=scatterplot(filtmsg,1,trainlen,'bx');hold on;
scatterplot(symbolest,1,trainlen,'r.',h);
scatterplot(sigconst,1,0,'k*',h);
legend('fitered signal','equalized signal','ideal signal constellation');
hold off;
demodmsg_noeq=pskdemod(filtmsg,M);
demodmsg =pskdemod(yd,M);
[nnoeq,rnoeq]=symerr(demodmsg_noeq(trainlen+1:end),msg(trainlen+1:end));
[neq,req] = symerr(demodmsg(trainlen+1:end),msg(trainlen+1:end));
disp('symbol error rate with equalizer:');
disp(req);
disp('symbol error rate without equalizer:');
disp(rnoeq)
RESULT:
Thus the Zero Forcing Equalizer is simulated in MATLAB.
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SIMULATED OUTPUT:
Enter the system order,N=5
Enter the number of iterations,M=200
0 20 40 60 80 100 120 140 160 180 200-0.2
0
0.2
0.4
0.6
0.8
1
1.2system output
number of iterations
true a
nd e
stim
ate
d o
utp
ut
desired
output
error
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2. Equalization using LMS Algorithm
AIM:
To simulate Least Mean Square (LMS) algorithm to adaptively adjust the coefficients of
an FIR filter.
SOFTWARE USED:
MATLAB
THEORY:
The LMS recursive algorithm used for adjusting the filter coefficients adaptively so as to
minimize the sum of squared error is described below.
Let x[n] be the input sequence and y[n] be the output sequence of an FIR filter. Then,the
output is given by the expression
Y[n]=∑ h[k]x[n-k], n=0,1,……M
Where h[n] is the adjustable coefficients of FIR filter.
Let the desired sequence be d[n].Then, the error sequence e[n] is given by
e[n] = d[n] – y[n] , n=0,1,……M
The LMS algorithm starts with any arbitrary choice of h[k],say h0[k].For example, we
may begin with h0[k]=0,0 ≤ k ≤ N-1.After that each new sample x[n] enters the adaptive filter
,we compute the corresponding output, say y[n], form the error signal e[n]=d[n]-y[n],and update
the filter coefficients according to the equation
hn[k] = hn-1[k] +µ.e[n].x[n-k], 0 ≤ k ≤ N-1,n=0,1…..where µ is called step size parameter, x[n-k]
is the sample of input signal located at the kth tap of the filter at time n and e[n]x[n-k] is an
approximation(estimate) of the negative of the gradient for the kth filter coefficients.
The step size parameter µ controls the rate of convergence. Large value of µ leads to
rapid convergence and smaller value leads to slower convergence. If µ is made too large,the
algorithm becomes unstable.
In order to ensure convergence and good tracking capabilities in slowly varying channels,
the step size parameters is given by µ=1/5NPx where N is the length of the adaptive FIR filter
and Px is the average power in the input signal which is approximated by
M
n
x nxM
P0
2 )(1
1.
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SIMULATED OUTPUT:
1 1.5 2 2.5 3 3.5 4 4.5 50
0.1
0.2
0.3
0.4
0.5
0.6
0.7comparison of actual weights and estimated weights
actual weights
estimated weights
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PROGRAM:
clc;clear all;close all;
N=input('enter the system order,N=');
M=input('enter the number of iterations,M=');
if((N>=2)&&(M>=2))
x=rand(M,1);
b=fir1(N-1,0.5);
n=0.1*randn(M,1);
d=filter(b,1,x)+n;
h=zeros(N,1);
Px=(1/length(x))*sum(x.^2);
mu=1/(5*N*Px);
for n=N:M
u=x(n:-1:n-N+1);
y(n)=h'*u;
e(n)=d(n)-y(n);
h=h+mu*u*e(n);
end
hold on;plot(d,'g');
plot(y(),'r');
semilogy((abs(e())),'m');
title('system output');
xlabel('number of iterations');
ylabel('true and estimated output');
legend('desired','output','error');
hold off;
figure,plot(b','k+');
hold on,plot(h,'r*');
legend('actual weights','estimated weights');
hold off;
title('comparison of actual weights and estimated weights');
else('system order and number of iterations should be greater than 1');
end
RESULT:
Thus the Least Mean Square (LMS) algorithm is simulated in MATLAB.
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CIRCUIT DIAGRAM:
DEMODULATOR
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CONTENT BEYOND SYLLABUS
EXPT.NO.1 AM MODULATION AND DEMODULATION USING IC2206
AIM:
To construct amplitude modulator and demodulator circuit and plot the waveforms.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1
IC2206 1
2 Resistors 47K,1K,10K,
220Ω 3,1,1,1
3. Capacitors 0.01µF,0.1µF 1,2
THEORY:
MODULATOR:
An amplitude modulated signal is composed of both low frequency and high frequency
components. The amplitude of the high frequency (Carrier) of the signal is controlled by the low
frequency (modulating) signal. The envelope of the signal is created by the low frequency signal.
If the modulating signal is sinusoidal, then the envelope of the modulated radio frequency (RF)
signal will also be sinusoidal. The circuit for generating an AM modulated waveform must
produce the product the of the carrier and the modulating signal.
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TABULATION:
MODULATING SIGNAL
Signals Amplitude (V) Time period
(ms) Frequency (KHz)
Modulating signal
Carrier signal
MODULATED SIGNAL
Emax (V) Emin (V) m = (Emax – Emin) / (Emax + Emin) %
DETECTED SIGNAL
Amplitude
(V) Frequency (KHz) Time period (ms)
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DEMODULATOR:
A single diode can be used to detect the AM signal and is called PN diode detector or
envelope detector. The diode acts as a rectifier in removing half the envelope resulting in the
base band signal with a Dc offset. The offset is removed with a series capacitor, producing the
output.
Envelope detectors are not perfect. All diodes are nonlinear, and will distort the envelope
when it is near the zero voltage level. This effect can be minimized by using a diode with a low
forward voltage drop and a strong signal(several 100mV) at the detector.
PROCEDURE:
1. Rig up the circuit as per the circuit diagram.
2. Set the carrier signal to 8V, 10 KHz using function generator and measure the
amplitude and time period.
3. Set the modulating signal 4V,1 KHz and measure the amplitude and time period.
4. Vary the amplitude around the carrier voltage.
5. Note down the maximum (Emax) and minimum (Emin) voltages from the CRO.
6. Calculate the modulation index using the formula.
7. Apply the AM signal to the detector circuit.
8. Observe the amplitude demodulated output on the CRO.
9. Compare the demodulated signal with the original modulating signal (Both must be
same in all parameters). Plot the observed waveforms.
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MODEL GRAPH:
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RESULT:
Thus the characteristics of AM Transmitter and Receiver are studied and the waveforms
are observed and plotted.
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CIRCUIT DIAGRAM:
FREQUENCY MODULATION:
FREQUENCY DEMODULATOR:
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EX.NO. 2 FM MODULATOR AND DEMODULATOR USING IC 2206
AIM:
To perform frequency modulation and demodulation .
COMPONENTS REQUIRED:
S.NO.
NAME OF THE
EQUIPMENT /
COMPONENT
RANGE QUANTITY
1 IC2206 1
2 Resistors
10K,3.3K,150Ω,
47K,10K(POT),
560Ω, 4.7K
1,1,1,1,1,
2,2
3 Capacitors 10µF,1µF,0.01µF,470pF 2,1,3,1
4 Function Generators 1 MHz 2
5 CRO 20MHz 1
6 Bread board - 1
7 Regulated Power supply 0-30V 2
THEORY : Frequency modulation(FM) conveys information over a carrier wave by varying its
instantaneous frequency (contrast this with amplitude modulation ,in which the amplitude of the
carrier is varied while its frequency remains constant).Frequency modulation is defined as the
process in which the instantaneous frequency of the carrier varies in accordance with the
instantaneous values of the modulating signal. Frequency modulation can be regarded as phase
modulation where the carrier phase modulation is the time integral of the FM modulating signal
Frequency demodulation is the process of retrieving the original modulating signal from the
modulating signal. A common method for recovering the information signal is through a Foster-
seeley discriminator. The various application of FM modulator and demodulator are
Broadcasting, magnetic tape storage, sound, radio.
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TABULATION:
Signals Amplitude (V)
Time period
(ms)
Frequency(KHz)
Modulating
signal
Carrier signal
Modulated
signal
Tmin= fmax=
Tmax= fmin=
Demodulated
signal
MODEL GRAPH
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PROCEDURE:
1.The circuit connection are made according to the circuit diagram.
2.The power supply and ground connections are made.
3.The modulating input signal and carrier signal is given using function generator.
4.The frequency modulated wave is seen on the CRO
5.The modulated signal is sent as input to a demodulator circuit and demodulated
signal is observed on the CRO.
RESULT: The modulating signal was frequency modulated and demodulated.
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CIRCUIT DIAGRAM:
MODEL GRAPH
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EXPT.NO.3 DIGITAL MODULATION – ASK
1. Using hardware
AIM:
To generate Amplitude Shift Keying signal using operation amplifier 741.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 IC 741 - 1
2 Resistors 1K 3
3 Capacitors 0.01µF 2
4 Decade Resistance Box 2 to 3K 1
5 Function Generator 1 MHz 1
6 CRO 10 MHz 1
7 Bread board - 1
8 Dual Power supply 0-15V 1
THEORY:
In digital modulation technique, binary „1‟ or „0‟ is transmitted by changing the
amplitude of the carrier signal and is called Amplitude Shift Keying. A sinusoidal signal
is used as the carrier signal. The carrier signal is allowed to pass through to transmit
binary „1‟ and is switched off to transmit binary „0‟. The carrier signal is generated using
OP-amp. A square wave is used as the binary signal to be transmitted.
DESIGN:
Assume f0 = 16KHz
Let C= 0.01 μF
f0 = RC2
1 ;R=
cf02
1
=
63 10*01.0*10*16*2
1
1KΩ
Let R1= 1KΩ
A = 1+
1R
R f ; A = 3 ; Rf = 2KΩ
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PIN CONFIGURATION:
TABULATION:
MODULATING SIGNAL:
Vm (V) Ton (ms) Toff(ms) Frequency(KHz)
CARRIER SIGNAL:
Vc(V) Time period (µs) Frequency(KHz)
ASK OUTPUT:
No. of
cycles
Time period of
each cycle (µs)
Total Time period(ms) Amplitude
(V)
Frequency
(KHz) Ton(ms) Toff(ms)
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PROCEDURE:
1. Connections are given as per the circuit diagram.
2. Measure the amplitude and time period of the square wave input signal.
3. Remove the square wave input and ground that terminal. Now the circuit is a wein
bridge oscillator.
4. Verify whether the sinusoidal carrier signal is generated or not. Note down the
amplitude and time period of the carrier signal.
5. Apply the square wave input signal and note down the amplitude and time period of
the ASK output signal.
RESULT:
Thus the Amplitude Shift Keying signal is generated and the waveforms are
observed
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CIRCUIT DIAGRAM:
MODEL GRAPH:
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EXPT.NO. 4 PULSE AMPLITUDE MODULATION
AIM:
To construct Pulse Amplitude Modulator and Demodulator circuits and observe
the waveforms.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 OP-AMP µA 741 1
2 Transistor BC 108 1
3 Capacitors 0.1µF 2
4 Resistors 1K,10K,22K,1.5K 2,1,1,3
5 Function Generators 1 MHz 2
6 CRO 10MHz 1
7 Bread board - 1
8 Regulated Power supply 0-15V 1
9 Dual Power supply 0-15V 1
DESIGN:
Low pass filter design:
Let .1KHzf ; Let FC 1.0 ; R = Cf2
1.
Substituting we get,
R = 1.5 K
THEORY:
In Pulse Amplitude Modulation the carrier is a periodic train of pulses. It is
discontinuous, discrete process i.e. the pulses are present only at certain distinct intervals
of time hence it is most suited for messages that are discrete in nature. However with the
help of sampling techniques continuously varying signals can be transmitted on pulsed
carriers. Generally pulse modulation and coding go hand in hand as in telegraphy and
teletype. The pulse modulated signal, despite the term modulation is base band signals.
The base band coding schemes are the actual coding schemes for base band transmission.
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PIN DIAGRAM
TABULATION:
MODULATING SIGNAL:
Vm (V) Time period
(ms)
Frequency
fm (KHz)
CARRIER SIGNAL:
Vc (V) Ton
(µs)
Toff
(µs)
Total Time
period (µs)
Frequency
fc (KHz)
PAM OUTPUT:
Vmax
(V)
Vmin
(V)
No.of
cycles
Time period Frequency
(KHz)
Ton (ms) Toff (ms)
Vout
(V) Time period (ms) Frequency(KHz)
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PROCEDURE:
1. Rig up the circuit as shown in the figure.
2. Using a function generator generate the carrier signal which is of pulse type with
amplitude Vc and frequency fc.
3. Using another function generator generate the modulating signal which is analog with
amplitude Vm and frequency fm.
4. Select the frequency of the carrier signal in such a way that it satisfies sampling
theorem.
5. Set the above arrangement and switch on the power supply.
6. Observe the corresponding waveforms with the help of CRO and plot them on the
graph.
7. Apply the Pulse Amplitude Modulated signal to the input of the demodulator circuit
and note down the demodulated signal and plot in on the graph.
RESULT:
Thus the Pulse Amplitude Modulator and demodulator circuits are constructed
and the waveforms are observed and plotted.
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CIRCUIT DIAGRAM:
TRIGGER CIRCUIT
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EXPT.NO.5 PULSE WIDTH MODULATION
AIM:
To generate the Pulse Width Modulated signal using 555 timer.
COMPONENTS REQUIRED:
S.NO. NAME OF THE EQUIPMENT /
COMPONENT RANGE QUANTITY
1 IC 555 - 1
2 Diode 1N4148 1
3 Capacitors 0.1µF, 0.01µF 3,2
4 Resistors 6.8K,10K,1.8K 2,1,1
5 Function Generator 1 MHz 1
6 CRO 20 MHz 1
7 Bread board - 1
8 Regulated Power supply 0-15V 1
DESIGN:
Assume carrier frequency 0f = 750 Hz.
The operating frequency of IC 555 timer is given by 0fCRR BA )2(
45.1
Let C = 0.1 f ,Let R BA R ,Substituting we get,R kA 4.6 ;R kA 8.6
THEORY:
Pulse Time Modulation is also known as Pulse Width Modulation or Pulse Length
Modulation. In PWM, the samples of the message signal are used to vary the duration of
the individual pulses. Width may be varied by varying the time of occurrence of leading
edge, the trailing edge or both edges of the pulse in accordance with modulating wave. It
is also called Pulse Duration Modulation. Pulse width modulation is a one in which each
pulse has fixed amplitude but width of the pulses is made proportional to amplitude of the
modulating signal at that instant.
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MODEL GRAPH:
TABULATION:
MODULATING SIGNAL:
Vm (V) Time period (ms) Frequency(Hz)
PWM OUTPUT:
Amplitude
(V)
Time period of each pulse (ms)
Ton Toff Ton Toff Ton Toff Ton
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Pulse width increase when signal amplitude increases in positive direction and decreases
when signal amplitude increases in negative direction. Pulses of PWM is of varying pulse width
and hence of varying power component. So transmitter should be powerful enough to handle the
power of maximum pulse width. But average power transmitted is only half is peak powerThe
main advantage of PWM is system will work even if the synchronization between the transmitter
and receiver fails. The emitter coupled monostable multivibrator is an excellent voltage to time
converter. Since its capacitor charges if the voltage is varied in accordance with the signal
voltage, a series of rectangular pulses will be obtained with varying width as required.
PROCEDURE:
1. Rig up the circuit as shown in the circuit diagram.
2. Note down the amplitude (Vm) and time period of the modulating signal.
3. Observe the output at „A‟ (carrier signal) and measure the amplitude (Vc) and
time period.
4. Observe the spike output at „B‟ and measure the amplitude and time period.
5. Apply the modulating signal input and trigger input and observe the PWM output.
6. Note down the amplitude and time period of all the signals and plot them on the
graph.
RESULT:
Thus the Pulse Width Modulated signal is generated using IC 555 timer and its
Waveforms are plotted.
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SIMULATION OUTPUT:
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EXPT.NO.6 SIMULATION OF LINEAR DELTA MODULATION
AIM:
To simulate the linear delta modulation using MATLAB.
SOFTWARE USED:
MATLAB
PROGRAM:
clc;
clear all
close all
fs=100;
t=0:1/fs:2;
m=sin(2*pi*t);
plot(m);
hold all;
AM=1;
FM=1;
d=2*pi*FM*AM/fs;
for n=1:length(m);
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);
eq(n)=d*sign(e(n));
mq(n)=mq(n-1)+eq(n);
end
end
stairs(mq)
RESULT:
Thus the MATLAB code for linear delta modulation was written & output is verified.
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SIMULATED OUTPUT:
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EX.NO.7 OFDM SPECTRUM
AIM:
To write and simulate the MATLAB codes for OFDM spectrum (Guard interval insertion).
THEORY:
Orthogonal frequency-division multiplexing (OFDM), essentially identical to coded OFDM
(COFDM) and discrete multi-tone modulation (DMT), is a frequency-division multiplexing
(FDM) scheme used as a digital multi-carrier modulation method. A large number of closely-
spaced orthogonal sub-carriers are used to carry data. The data is divided into several parallel
data streams or channels, one for each sub-carrier. Each sub-carrier is modulated with a
conventional modulation scheme (such as quadrature amplitude modulation or phase-shift
keying) at a low symbol rate, maintaining total data rates similar to conventional single-carrier
modulation schemes in the same bandwidth.
OFDM has developed into a popular scheme for wideband digital communication, whether
wireless or over copper wires, used in applications such as digital television and audio
broadcasting, wireless networking and broadband internet access.
The primary advantage of OFDM over single-carrier schemes is its ability to cope with
severe channel conditions, without complex equalization filters. Channel equalization is
simplified because OFDM may be viewed as using many slowly-modulated narrowband signals
rather than one rapidly-modulated wideband signal.
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SIMULATED OUTPUT:
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PROGRAM:
clear all;
Fd=1; % symbol rate (1Hz)
Fs=1*Fd; % number of sample per symbol
M=4; % kind(range) of symbol (0,1,2,3)
Ndata=1024; % all transmitted data symbol
Sdata=64; % 64 data symbol per frame to ifft
Slen=128; % 128 length symbol for IFFT
Nsym=Ndata/Sdata; % number of frame -> Nsym frame
GIlen=144; % symbol with GI insertion
GI=16; % guard interval length
vector initialization X=zeros(Ndata,1); Y1=zeros(Ndata,1); Y2=zeros(Ndata,1);
Y3=zeros(Slen,1); z0=zeros(Slen,1);z1=zeros(Ndata/Sdata*Slen,1);
g=zeros(GIlen,1);
z2=zeros(GIlen*Nsym,1);z3=zeros(GIlen*Nsym,1);
random integer generation by M kinds X = randint(Ndata, 1, M);
digital symbol mapped as analog symbol Y1 = modmap(X, Fd, Fs, 'qask', M);
covert to complex number Y2=amodce(Y1,1,'qam');
for j=1:Nsym;
for i=1:Sdata;
Y3(i+Slen/2-Sdata/2,1)=Y2(i+(j-1)*Sdata,1);
end
z0=ifft(Y3);
for i=1:Slen;
z1(((j-1)*Slen)+i)=z0(i,1);
end
for i=1:Slen;
g(i+16)=z0(i,1);
end
for i=1:GI;
g(i)=z0(i+Slen-GI,1);
end
for i=1:GIlen;
z2(((j-1)*GIlen)+i)=g(i,1);
end
end
graph on time domain figure(1);
f = linspace(-Sdata,Sdata,length(z1)); plot(f,abs(z1));
Y4 = fft(z1);
if Y4 is under 0.01 Y4=0.001 for j=1:Ndata/Sdata*Slen;
if abs(Y4(j)) < 0.01 Y4(j)=0.01;
end
end
Y4 = 10*log10(abs(Y4));graph on frequency domain figure(2);
f = linspace(-Sdata,Sdata,length(Y4)); plot(f,Y4);axis([-Slen/2 Slen/2 -20 20]);
RESULT: Thus the MATLAB code for OFDM Spectrum was written & output is verified.
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OUTPUT WAVEFORM:
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EX.NO: 8 PULSE POSITION MODULATION
AIM: To write and simulate in the MATLAB codes for Pulse position modulation.
THEORY:
PROGRAM:
clc;
clear all;
close all;
fc=1000;
fs=10000;
fm=200;
t=0:1/fs:(2/fm-1/fs);
mt=0.4*sin(2*pi*fm*t)+0.5;
st=modulate(mt,fc,fs,'PPM');
dt=demod(st,fc,fs,'PPM');
figure
subplot(3,1,1);
plot(mt);
title('message signal');
xlabel('time period');
ylabel('amplitude');
axis([0 50 0 1])
subplot(3,1,2);
plot(st);
title('modulated signal');
xlabel('time period');
ylabel('amplitude');
axis([0 500 -0.2 1.2])
subplot(3,1,3);
plot(dt);
title('demodulated signal');
xlabel('time period');
ylabel('amplitude');
axis([0 50 0 1])
RESULT:
Thus the MATLAB code for PPM was written & output is verified.
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EXPT.NO. 9 COMMUNICATION LINK SIMULATION USING SDR
AIM:
To study all digital modulation techniques using SDR TRAINER KIT .
EQUIPMENTS REQUIRED:
SDR Trainer Kit -1
SMA Connector-1
USB device -1
THEORY:
FREQUENCY MODULATION
It is a type of modulation in which the frequency of the high frequency (Carrier) is varied
in accordance with the instantaneous value of the modulating signal. The FM modulator is used
to combine the carrier wave and the information signal in much the same way as in the AM
transmitter. The only difference in this case is that the generation of the carrier wave and the
modulation process is carried out in the same block.
BLOCK DIAGRAM:
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OUTPUT WAVEFORM:
AMPLITUDE PHASE SHIFT KEYING
ASK is the simplest modulation technique, where a binary information signal directly
modulates the amplitude of an analog carrier. ASK is similar to standard amplitude modulation
except there are 2 output amplitudes possible. It is also referred as on-off keying.
BLOCK DIAGRAM:
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OUTPUT WAVEFORM:
FREQUENCY SHIFT KEYING
In FSK, modulating signal is a binary signal that varies between two discrete voltage levels
rather than a continuously changing analog waveform.
BLOCK DIAGRAM:
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OUTPUT WAVEFORM:
BINARY PHASE SHIFT KEYING
The simplest form of PSK is binary phase shift keying( N=1 and M=2). 2 phases are
possible for the carrier. One phase represents logic 1 & other phase represents logic 0. As the
input signal changes state, the phase of the output carrier shifts between two angles that are
separated by 180°
BPSK is a form of square wave modulation of a continuous wave (CW)
signal.
BLOCK DIAGRAM
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OUTPUT WAVEFORM:
Result: Thus all digital modulation techniques was designed and performed using SDR
TRAINER KIT.