(a christian minority institution)2).pdf(a christian minority institution) ... ec 6512 communication...

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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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EC 6512-Communication System Lab Department of ECE

1

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.




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.


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:


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


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.




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:


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


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


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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');


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');


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.




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:


SAMPLED SIGNAL:

Channel Amplitude(V)

No. of

samples

Time period (ms)

(for each sample)

Total Time

Period

(ms)

Frequency

(KHz)

Ton Toff

RECEIVED SIGNAL:


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:


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.




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

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EXPT. NO. 12 LINE CODING AND DECODING

AIM:

To analyze line coding and decoding techniques.




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.


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.


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.




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 .


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


5 CRO 20MHz 1

6 Bread board - 1


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.




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.




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


6 CRO 10MHz 1

7 Bread board - 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.




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


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');



axis([0 500 -0.2 1.2])

subplot(3,1,3);

plot(dt);

title('demodulated signal');



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.

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