ec2307-new digital communication lab manual odd 2011

JEPPIAAR ENGINEERING COLLEGE(A CHRISTIAN MINORITY INSTITUTION)

JEPPIAAR EDUCATIONAL TRUSTJeppiaar Nagar, Rajiv Gandhi salai, Chennai-600119.

EC 2307 - COMMUNICATION SYSTEMS LABORATORY

III year -V SEM– ECE

OBSERVATION NOTE-BOOK

NAME : ______________________________________ROLL NO. : ______________________________________REG NO. : _______________________________________YEAR : _______________________________________SECTION : _______________________________________

0

INDEX

S.No Date Name of the ExperimentDate of

SubmissionMarks Signature

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

1

INSTRUCTIONS

The students are requested to

Use this lab manual as observation notebook.

Bring the lab manual compulsorily for all lab classes.

Get the verified signature from the lab instructors, once the

experiment is completed and output seal should be endorsed and

get the staff signature on that lab class itself.

Get the record correction for the experiment, before entering the

next lab class otherwise entry will be denied.

“Get completed signature in the index page of the record from the

staff-in charge” after the completion of all experiments

Before entering the university practical examinations, the students

must get the confide signature in the observation and record

notebook.

2

JEPPIAAR ENGINEERING COLLEGEDEPARTMENT OF ECEIII YEAR VSemester

EC2307 COMMUNICATION SYSTEMS LABORATORY

1. Amplitude modulation and Demodulation.

2. Frequency Modulation and Demodulation

3. Pulse Modulation – PAM / PWM / PPM

4. Pulse Code Modulation

5. Delta Modulation, Adaptive Delta Modulation.

6. Digital Modulation & Demodulation – ASK, PSK, QPSK, FSK (Hardware &

MATLAB)

7. Designing, Assembling and Testing of Pre-Emphasis / De-emphasis Circuits.

8. PLL and Frequency Synthesizer

9. Line Coding

10. Error Control Coding using MATLAB.

11. Sampling & Time Division Multiplexing.

12. Frequency Division Multiplexing,

3

Ex.No: 1

Date: Generation and Detection of amplitude modulation

Aim:To construct an amplitude modulation & demodulation circuit and to calculate modulation index of AM.

Apparatus Required:s.no components Range qty1 Transistor Bc 107 12 Resistor 1k,100k,2.2k 13 Capacitor 0.1 mf 34 diode OA 79 25 Function generator 0-100 k HZ 16 C.R.O 0-60 MHZ 17 Regulated power supply 0-30 V 1

Theory:AM is defined as the amplitude of a carrier signal is varied according to

variation in the amplitude of the modulating signal.When the signal is to be transmitted over a long distance, it is placed on

some high frequency carrier. This high frequency carrier travel over long distances without any much attenuation. The carrier is normally a sinusoidal.The amplitude modulated wave is givenEam=e am sinǿ=e am sinwct= (Ec+Em sinwmt)sinwctWhere Ec=carrier amplitude in voltsEm=message amplitude in voltsWm=message angular freq in hertzWC=carrier angular freq in hertzModulation can be done using two types of modulator circuits, as given below

Low level AM modulator {emitter modulator} Medium power AM modulator (or) high level AM modulator (or) collector modulator

Modulation IndexThe ratio of maximum of modulating signal to maximum amplitude of carrier signal is called modulation index M=Em/Ec .If modulation index expressed in percentage it is also called as percentage modulationAdvantageModulator operates at low voltage levelPower efficiency is practically higher than 80%All the preceding linear amplifier operates at low power level.DisadvantagesRequires high amplitude of modulating signal Amplitude in Modulator is non linearApplicationWhere we want to modulate the ratio signal.

4

DEMODULATIONIt is the process of separating message signal from the modulated wave

carrier signal. The most commonly used AM detector is simple diode detector . the AM signal at fixed if is applied to the transformer primary. The signal at secondary is half wave rectified by diode d . so that only it is called detector negative peak clipping is done using the detector circuit. This is the distortion occurs in the output of diode detector because of unequal ac and dc load impedences of the diode .The modulation index is defined as Em/Ec. Therefore it can also be defined as Im/Ic with

Im=Em/Rm ; Ic=Ec/RcWhere, Zm= is audio diode loadimpendence and Rc is the dc diode

resistance. The audio load resistance of the diode is smaller than thedc resistance.

AdvantageThe modulation index value is nearly 100%Load impendence is lowDisadvantageDistortion will be added during the diagonal clipping

PROCEDURE1. connection is given as per the circuit diagram.2. Modulating frequency is kept at 1 KHZ.3. Carrier frequency is kept at 10KHZ 4. The output waveform is observed in CRO and measure Vmax

&Vmin are calculated, modulation index calculated.5. Using CRO demodulated wave is noted down.6. Output and input characteristics are plotted in graph.

Tabulation:

Signal Amplitude(v) Time period(msec)

Frequency(HZ)

Input signalCARRIER SIGNAL

AM signal V max=V min=

Demodulated signal

5

CIRCUIT DIAGRAM

MODEL GRAPH:

Demodulated signal

RESULTThe amplitude modulation & demodulation circuits has been constructed and its characteristics are obtained.

6

Ex. No: 2Date :

Generation of Frequency modulation and its Detection.

Aim: To construct an Frequency modulation & demodulation circuit and to calculate modulation index of FM.

Apparatus Required:

s.no components Range Qty1 XR 2206 IC2 Resistor3 Capacitor4 Connecting wires 5 Function generator 0-100 k HZ6 C.R.O 0-60 MHZ7 Regulated power supply 0-30 V

Theory:When frequency of the carrier varies as per amplitude variations of modulating signal then its called frequency modulation Amplitude of the modulated carrier remains constant the frequency modulated wave is given by e(t)= Ec sin(wct+ K1 Em/wm sin (wmt))Advantages

Bandwidth is large, fidelity is better. All transmitted power is useful Noise interference operates in VHF and UHF range Infinite numbers of sideband are present The radius of propagation is limited to line of sight.

Disadvantages The bandwidth requirement of FM is much higher than that of AM The FM transmitting and receiving equipment is more complex and

costly Since FM uses UHF & VHF range frequencies its area of reception is

limited only to line of sight. This is much lower than area covered by AM.

Circuit dagram:

7

MODEL GRAPH:

PROCEDUREConnection are given as per circuit diagram For FM carrier is generated without giving input with RT & ctNote amplitude and frequency of carrier waveBy giving input through function generator set a particular frequencyThe output modulated wave is traced and its amplitude and frequency are computed The demodulation is done by given modulated output wave as input toi demodulator o/p is obtained.

RESULT

The frequency modulation & demodulation circuit has been constructed and its characteristics are obtained.

8

EX: NO:3 a)DATE:

Generation and Detection of Pulse amplitude modulation

Aim:

To construct a pulse amplitude modulation& demodulation circuit using discrete components and to study the output.( Reconstruct the original modulating signal.)Apparatus Required:

S.No Components Range Quantity1 Diode – IN 32 - 12 Resistors 33 K 23 Capacitors 0.1 F 14 Function Generator 1 Hz – 2 MHz 25 CRO 0-30 MHZ 16 Regulated Power Supply 0 – 30 V 1 THEORY:

1. PAM system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at that instant of sampling.

2. The PAM pulses are transmitted either by wire or cable is used to modulate the carrier.

3. In a double polarity PAM a fixed Dc level is added to the signal to ensure that the pulses are always positive.

4. The pulses are usually of short duration and hence PAM has LOW duty cycle.

5. The low duty cycle operation coupled with the facility of utilization of the time interval between the two consecutive periods.

6. hence multiplexing techniques can be used.Circuit Diagram:

D 1 I n 3 2

D 2 I N 3 2

c 1

0 . 1 n f

C 40 . 1 M ic ro F

R 3

2 2 K

R 23 3 K

R 1 3 3 k O H M

V C C _ B A R

modulating wave 1 KHZ& 2V

carrier wave 10 KHZ

CRO

9

Demodulation cktModulation ckt

another ckt

Q 1

2

1

R 12 2 K

2

1

R 24 . 7 K

21R 3

4 7 K

V C C _ (6 V )

messagesignal Vst

VPAMt (output)

bc107

Vct Carrier signalPr

ocedure:

1. The connections are given as per the circuit diagram.2. The modulating input fed to the PAM generator circuit is modulated using the

trigger pulse and PAM output is displayed in CRO.3. The PAM signal is fed to the baseband signal recovery circuit, which is a filter

using op-amp output, is displayed in CRO.4. Graphs related to the experiment are plotted.

Tabular Column:

SIGNAL AMPLITUDE (V)

TIME PERIOD (s)

Frequency(HZ)

Carrier

Modulating

Modulated V max=V min=

ModelGraph:

10

Result:

The PAM circuit is constructed using sampling gates and the output waveforms are plotted.

EX:NO:3 b)DATE:

PULSE WIDTH MODULATIONAim:

To construct and study the characteristics of a Pulse width modulation circuit.Apparatus Required:S.No Components Range Quantity

1 IC 555 - 12 Resistors 1 K 13 Capacitors 0.1 F

2.2 F2

4 Function Generator 1 Hz – 2 MHz 25 C.R.O 60 MHZ 16 Regulated Power Supply (0 – 30 V) 1

THEORY:

11

1. Pulse width modulation is a one in which each pulse has a fixed amplitude but width of the pulses is made proportional to amplitude of the modulating signal at that instant.

2. pulse width increase when signal amplitude increases in positive direction and decreases when signal amplitude increases in negative direction.

3. 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 power.

4. the main advantage of PWM is system will work even if the synchronization between the transmitter and receiver fails.

Circuit Diagram: + VCC = + 9 V 1 K Output

0.1 F 0.1 F 0.1 F 2.2 F Sine Square Wave I/p Wave I/p

12

4 83 7 IC 555 1 6 5 2

Pin Diagram: [[ GND 1 8 + VCC TRIGGER 2 7 DISCHARGE [[[[ IC 555 OUTPUT 3 6 THRESHOLD [

RESET 4 5 CONTROL VOLTAGE

Procedure:

1. The connections are given as per the circuit diagram.2. The modulating input and clock pulse signals are given.3. the corresponding output is noted in CRO.4. Now modulating signal can be varied in amplitude and resulted output

can be traced.Tabular Column:


TIME PERIOD (s)

FREQ(HZ)

Carrier

Modulating

Modulated

Ton=Toff=

1) Ton=Toff=

2) Ton=Toff=

3) Ton=Toff=

Model Graph

Result:

Thus, the Pulse width modulation circuit is constructed and its output waveforms are plotted.

Max time period= Min time period=

13

EX:NO:3 c)DATE:

PULSE POSITION MODULATIONAim:

To construct a Pulse Position Modulation circuit using PWM circuit.Apparatus required:

S.No. Components Range Quantity1 IC 555 - 12 Resistors 3.9 K, 3 K 13 Capacitors 0.01 F 14 Function Generator 1 KHz 15 C.R.O - 16 Regulated Power Supply 0 – 30 V 1

Theory:

1. Pulse modulation is the process by which the position of pulse is varied in accordance with information contained in sample waveform.

2. Because the pulse width is remains unchanged, the bandwidth required for transmission of pulse information remains stationary.

3. PPM can be obtained from PDM / PWM with trailing edge modulation by inverting and differentiating so that the modulated edges are changed into pulse position modulated spikes.

Circuit Diagram: +Vcc +10V

Ra=3.9 K

CRO O/P

I/P modulating signalTriangular Wave 1KHz

C = 0.01 F

Tabular Column:

14

8 4 3 7

IC 5555 2

6

Rb = 3.3 K


TIME PERIOD (s)

Freq(HZ)

Carrier(without msg signal)at pin no:3

Modulating

Modulated

Ton=Toff=

Ton=Toff=

Ton=Toff=

Ton=Toff=

PROCEDURE

1. The connections are given as per the circuit diagram.2. The modulating input and clock pulse signals are given.3. The corresponding output is noted in CRO.4. Now modulating signal can be varied in amplitude and resulted

output can be traced.

Model Graph:

Result: Thus, the Pulse position modulation circuit is constructed and its output waveforms are traced.

15

EX:NO:4DATE:

PULSE CODE MODULATIONAim:

To construct and study a PCM transmitter and receiver kitApparatus Required:1. PCM Transmitter and Receiver Kit 2. Connecting Plugs3. CROTHEORY:

1. The block diagram shows the method of PCM generation system.2. In this transmitter circuit, two message inputs are sampled and multiplexed

and then it is pass over to the A/D converter to circuit to get digital messages as encoder.

3. The PCM system has an error check code generator to make a distortion less transmission.

4. Then to a shift register to get the regenerated signals without any error.5. The timing circuit / logic provides a periodic pulse train, derived from

receiver sampling the equalized pulses at the instants of time where the signal to noise ration is minimum.

6. If the measured value is larger than threshold or reference value, a ‘1’ was transmitted.

7. If the comparison value is below the threshold value a zero was transmitted.

8. The reverse steps are used in the receiver process.

PCM TRANSMITTER& RECEIVER

INPUT SIGNAL

OUTPUT SIGNAL

16

AF Generator

Sample and hold

A/D converter

Shift register

Voltage amplifier

Low pass filter D/A Converter Shift register

CH-0 SAMPLE CH-1 SAMPLE

PCM PCM

O/P

PCM RECEIVER

17

FUNCTION GENERATOR

TRANSMITTER TIMING LOCIC

PSEUDO-RANDOM SYNCHRONOUS

CODE GENERATOR

CH-0

CH-1

SHIFT REGISTER

ERROR CHECKCODE GENERATOR

A/D CONVERTER

OUTPUTLOGIC

PCM O/P

CLOCKREGENERATION

CIRCUIT

PSEUDO-RANDOMSYNC CODEDETECTOR

RECEIVER TIMING LOGIC

CH-0 SAMPLE CH-1 SAMPLE

CH-0

CH-1

LATCH

SHIFT REGISTER

D/A CONVERTER

ERROR DETECTION/CORRECTIONLOGIC

TIMING LOGIC

Tabular Column:


TIME PERIOD (s)

Carrier

Modulating

ModulatedPCM CODE

Procedure:

1. The connections are given as per the circuit diagram.2. The input waveforms are traced using CRO.3. The put waveforms are traced using CRO.

Model Graph :

Result:

The PCM output waveforms are studied and obtained.

EX:NO:5

18

DATE: DELTA MODULATION AND DEMODULATION

Aim: To construct and study the characteristics of DELTA modulation and

demodulation kit.

Apparatus Required:

1. DELTA Modulation and demodulation kit2. Connecting Plugs3. CRO

THEORYDelta modulation is a form of pulse modulation width a sample value is represented as a signal bit. This is almost similar to differential PCM,as the transmittedBit is only, one per sample first to indicate whether the present sample is larger or smaller than previous oneThe encoding decoding, and quantizing process become extremely simple bit this system cannot handle rapidly varying samples. This increases the quantizing noise. The trainer is a self sustained and well organized kit.PROCEDUREThe connections are given as per the block diagram.The input waveform are noted using CROThe modulated demodulated waveforms are also traced using CRO.

BLOCK DIAGRAM

CLK

TABULATION

19

Sine wave generation Amplitude

FREQ

OFFSET

CLOCK generator

+

--

LPF One bit quantizer

Bipolar NRZ encoder

INTEGRATOR

Decoder Integrator LPF

GND

CLK

i/p

WAVE AMPLITUDE TIME PERIOD FREQUENCYINPUT

LPF OUTPUT

COMPARATOR O/P

ONE BIT QUANTISERO/P

BIPOLAR NRZ ENCODER O/PDEMODULATED

MODELGRAPH

RESULTThe delta modulation demodulation circuit is constructed and its output waveform is plotted.

20

EX:NO:6 a)DATE: ASK MODULATION AND DEMODULATION

Aim: To construct and study the characteristics of ASK modulation and

demodulation kit.

Apparatus Required:

4. ASK Modulation and demodulation kit5. Connecting Plugs6. CRO

Theory:Ask modulation means the amplitude of carrier waveform is swiched b/w two amplitude either high or low corresponding to binary information to be transmittedThe binary ask means the amplitude of transmitted signal switched b/w two values

ASK MODULATION

ASK DEMODULATION

ASKDEMODULATED O/P

21

DATAFORMAT

TING

NRZ(L)CODE

FORMATTING

CARRIER GENERATI

ON CIRCUIT

CARRIER MODULAT

ION CIRCUIT

ASKMODULATED O/P to CRO

ASK DEMODULATOR

(DETECTOR)LOW PASS

FILTER

DATA SQUARING CIRCUIT

NRZ CODE FORMAT

Tabular Column:

SIGNAL AMPLITUDE (V) FREQ(HZ) TIME PERIOD (s)

Carrier

Modulating

Modulated

Demodulated

Vmax=Vmin=

Procedure:


MODEL GRAPH: (ASK MODULATION)

Result:

The ASK modulation and demodulation circuit is constructed and its output waveforms are plotted.

22

EX:NO:6 b)DATE: FSK MODULATION AND DEMODULATION

Aim: To construct and study the characteristics of FSK modulation and

demodulation kit.

Apparatus Required:

7. FSK Modulation and demodulation kit8. Connecting Plugs9. CRO

Theory:

1. The FSK modulation means, the frequency of the carrier waveform is switched between two frequencies corresponding to the binary information to be transmitted.

2. The binary FSK, means the frequency of the transmitted signal switched between two values.

3. The FSK signal can be characterized as one of two difference types depending on the method used to generate the FSK signal.

4. There are two types of FSK as 1. Discontinuous FSK.2. Continuous FSK.

5. The discontinuous FSK is generated by switching the transmitter output between two different oscillators.

6. The continuous FSK signal is generated by feeding the data signal into frequency modulator.

23

FSK MODULATION

TX

CLK I/P

TX

DATA I/P

FSK DEMODULATION

CARRIER I/P

FSKDEMODULATED O/PNRZ CODE FORMAT

Tabular Column:SIGNAL AMPLITUDE

(V)FREQ(HZ) TIME

PERIOD (s)Carrier

Modulating

Modulated

Demodulated

Fmax=Fmin=

Tmin=Tmax=

Procedure:


24


DATAFORMAT

TING

NRZ(L)CODE

FORMATTING

CARRIER GENERATI

ON CIRCUIT

Data inverter

CARRIER MODULATI

ON CIRCUIT

FSK DEMODULATOR

( DETECTOR)LOW PASS

FILTER

FSK O/P

MODEL GRAPH: (FSK MODULATION)

Result:

The FSK modulation and demodulation circuit is constructed and its output waveforms are plotted.

25

EX:NO:DATE: BFSK MODULATION AND DEMODULATION

Aim: To construct and study the characteristics of BFSK modulation and

demodulation kit.

Apparatus Required:

10. FSK Modulation and demodulation kit11. Connecting Plugs12. CRO

Theory:

7. The FSK modulation means, the frequency of the carrier waveform is switched between two frequencies corresponding to the binary information to be transmitted.

8. The binary FSK, means the frequency of the transmitted signal switched between two values.

9. The FSK signal can be characterized as one of two difference types depending on the method used to generate the FSK signal.

10. There are two types of FSK as 1. Discontinuous FSK.2. Continuous FSK.

11. The discontinuous FSK is generated by switching the transmitter output between two different oscillators.

12. The continuous FSK signal is generated by feeding the data signal into frequency modulator.

DRAW THE BLOCK DIGRAM OF FSK

26

SQUREWAVE GENERATOR

SERIAL PORT

DEBOUNCE LOGIC

FSK MODULATOR

FSK DEMODULATOR E.ampl

ifier

VCO

FSK MODULATED WAVE (TO CRO)

DEMODULATED WAVE (TO CRO)

Tabular Column:

SIGNALAMPLITUDE

(V)TIME PERIOD

(s)FREQUENCE

Carrier1

Modulating

Modulated

Demodulated

T ON=TOFF=

Max=Min=

Max=Min=

Procedure:


MODEL GRAPH: (FSK MODULATIONAND DEMODULATION)

Result:

The BFSK modulation and demodulation circuit is constructed and its output waveforms are plotted.

27

EX:NO:6 c)DATE:

PSK MODULATION AND DEMODULATIONAim:

To construct and study the characteristics of PSK modulation and demodulation kit.Apparatus Required:1. PSK Modulation and demodulation kit.2. Connecting Plugs.3. CRO.Theory:1. The PSK modulation means, the frequency of the carrier waveform is

switched between two frequencies corresponding to the binary information to be transmitted.

2. The two vaules according to the two possible messages m1 and m2.3. The two phases are usually separated by Ǿ radians.4. The bandwidth of PSK scheme is the same as that of the ASK signal.5. The difference between ASK and PSK is that the ASK is a linear

modulation and PSKPSK MODULATION

PSK DEMODULATION

I/P

PSK DEMODULATED O/P

I/P

28

DATAFORMAT

TING

NRZ(L)CODE

FORMATTING

CARRIER GENERATI

ON CIRCUIT

UNIPOLAR/BIPOLAR

CONVERTERS

CARRIER MODULAT

ION CIRCUIT

PSKMODULATED

O/P

QPSK DEMODULATOR(PLL DETECTOR)

BIPHASE CLOCK

RECOVERY CIRCUITS


PSK MODULATOR

DIFFERENTIAL ENCODERS

Tabular Column:


Carrier

Modulating

Modulated

Demodulated

Vmax=Vmin=

PROCEDURE:1. The connection are given as per the block diagram 2. The input waveforms are noted using CRO3. The modulated &demodulated waveforms are also traced using CRO.

MODEL GRAPH: (PSK MODULATION)

Result:

The PSK modulation and demodulation circuit is constructed and its output waveforms are plotted.

29

EX:NO: 6 d)DATE: QPSK MODULATION AND DEMODULATION

Aim: The objective of this experiment is to study the QPSK modulator using Clock as binary dataApparatus Required:

1. QPSK Modulation and demodulation kit2. Connecting Plugs3. CRO 60 MHZ

Theory:

Tabular Column:


Carrier

ModulatingI channelQ channel

Modulated

Demodulated

Procedure:

Connect the binary input point p5 to the I-channel input point of P9.Connect the binary input point p6 to the Q-channel input point of p10.Connect the sine wave input (p3 point) to the p11 of balanced modulator as a carrier signal (I channel) and to sine wave input (p4 point) to the p13 point of balanced modulator as a carrier signal (q channel)Connect the test point p15 to p17 and p16 to p18 with the help of patch cards.Switch on the power supply CRO (p12 points)and adjust potentiometers pot1 to convert the unipolar data into bipolar.Display the test point p15 and p16 on channel1 and channel2 on CRO.Respectively Now adjust the gain control potentiometers to set equal amplitude in I channel and Q-channelFinally view the QPSK output waveform at test point ,P19.I=-1/2+1/2 Cos 2wct+1/2 sine2 wct+1/2 sine 0

30

I-1/2 v(logical)Again receive QPSK signal is one of the inputs to the Q product detector, the other input is the recovered carrier shifted 90degree in phase. The output of the Q product detector is Q=(-sinwct)+coswct(coswct)Q=-1/2+1/2 coswct-1/2 sine2wct-1/2sin0=-1/2 v (logical 1)The demodulated I Q corresponds to the construction diagram and truth table for the QPSK modulator shown above figure.

Phasor diagram

Binary INPUT QPSK output

0 0 -135-4513545

0 11 01 1

MODEL GRAPH: (QPSK MODULATION)

ResultThe QPSK modulation and demodulation circuits are constructed and its

output waveforms are plotted.

31

Exp No.6 b1)Date:

GENERATION OF FSK modulation & demodulation using MATLAB

AIM: To perform frequency shift keying modulation and demodulation using MATLAB program.

ALGORITHM:

STEP 1: Start the program.STEP 2: GET the two signals STEP 3: Plot the time along x-axis and amplitude along y-axis.STEP 4: Stop the program.

PROGRAM:

clc;clear all;close all;No.of_bits=16;root_freq=200;keying_freq=1000;stime=0.0005;mid=0.0001;t=0:0001:stime-mid;input_seq=randint(1,No.of_bits);subplot(3,1,1);stem(input_seq);Modulated_0=[];for i=1:length(input_seq) Modulated_0=[Modulated_0 sin(2*pi*(root_freq+input_seq(i)*keying_freq)*t)];endsubplot(3,1,2);plot(Modulated_0);demod=[];a=sin(2*pi*root_freq*t);for i=1:length(input_seq) y=(i-1)*50; d=asin(Modulated_0(y+1:y+50)); d1=d(2)/a(2);

32

if d1<2 demod=[demod 0]; else demod=[demod 1]; end subplot(3,1,3); stem(demod); xlabel('data samples'); ylabel('amplitude');figure(2);INPUT:

OUTPUT:

RESULT:

33

Exp No.6 c1)Date:

GENERATION OF PSK MODULATION & DEMODULATION using MATLAB

AIM: To perform phase shift keying modulation and demodulation using MATLAB program.

ALGORITHM:

STEP 1: Start the program.STEP 2: GET the two signals STEP 3: Plot the time along x-axis and amplitude along y-axis.STEP 4: Stop the program.

PROGRAM:clc;clear all;close all;t=[0:1/1000:1];no=1000;numbits=5;fc=1;tb=1;snr=[];ber=[];carrier=cos(2*pi*fc*t);basis=sqrt(2/tb)*carrier;for eb=1:numbits; mod=[]; recode=[]; demod=[]; data=randint(1,numbits); data(find(data==0))=-1; for j=1:numbits mod=[mod sqrt (eb)*data(j)*basis]; end noise=sqrt(no)*randn(1,length(mod)); recdcode=mod+noise; for i=1:numbits demod=[demod sqrt(eb)*recdcode(:,(i*length(t)+1:i*length(t)).*basis];

rxcode=[rxcode sum(demode(:,(i-1)*length(t)+1:i*length(t)))];

34

endrxcode(find(rxcode>=0))=1;rxcode(find(rxcode>=0))=-1;t1=[0:1/1000:numbits];figure(1);subplot(3,1,1);stem(data(1:numbits));carr=cos(2*pi*fc*t1);subplot(3,1,2);plot(t1,carr);axis([0 numbits-1 -1 1]);subplot(3,1,3);plot(t1(1:numbits*1000),mod(1:numbits*1000));axis([0 numbits-1 -5 5]);title('output sequence');xlabel('y(n)-->');INPUT:

OUTPUT:

RESULT:

35

Designing, Assembling and Testing of Pre-Emphasis / De-

emphasis Circuits.

Exp. No : 7

Date :

AIM:

To design and construct a pre emphasis & de emphasis circuits and to study its frequency response

Apparatus Required:

S.No Components Range Quantity

1 DIB - 12 Resistors 4.7 K

10 K 33 K2.2 K

1

3 Capacitors 0.1 F, 1 each4 Function Generator (1Hz – 1MHz.) 1

5 C.R.O 0-60MHZ 16 Dual Power Supply 0- 30 V 1

7 Transistor BC107 1

TheoryNoise has a higher effect on higher modulating frequency than the lower modulating frequency. Hence during transmission higher frequencies may be lost as noise.To avoid this boost the higher frequencies at the transmission line to called pre -emphasis at the detector output in receiver we perform the reverse operation by de-emphasis in the high frequency components. So to restore the original message.The due to these to pre emphasis & de-emphasis circuit, the output signal to noise ratio are effectively increased. They are mainly used in FM transmission and reception.

36

Procedure:

The connection are given as per the circuit diagram Adjust VCC to 12 vSet the input signal frequency is raised and corresponding voltage is notedFrom the calculation the gain is calculated from graph b/w frequency & voltage gain in db for the both pre emphasis , de-emphasis

Circuit Diagram:

Q 1

Q 2 N 2 2 2 2

L 1

5 m H

1

2

R 2

1 0 k o h m

R 11 0 k o h m

R 3

3 3 k o h m

C 2

0.1

u f

R 3

1 k o h m

R 4

2 . 2 k o h m

C 1

0 . 1 m ic ro f

V C C _ B A R

L 1

5 m H

12

0

C 2

0 . 1 m ic ro f

TABULAR COLOUMN:

37

CRO

PRE EMPHASIS Vin= S.NO FREQUENCY in

HZV out(V) GAIN=20 LOG

VO/VIN5.

6.7.8.9.10.11.12.13.14.

DE EMPHASIS V in= S.NO FREQUENCY in

HZV out(V) GAIN=20 LOG

VO/VIN1.

2.3.4.5.6.7.8.9.10.

Model Graph

Result :

The pre emphasis and de emphasis were designed and constructed and their frequency response are studied

Pre emphasis cut off frequency=De emphasis cut off frequency=

38

CHARACTERISTICS OF PLL.

Exp. No : 8 a)

Date :

AIM:

To construct and study the operation of PLL IC 565 and determine

its Characteristics.

Apparatus Required:

S.No Components Range Quantity

1 IC 565 - 12 Resistors 6.8 K 13 Capacitors 0.001 F

0.1 F, 1 F1 each

4 Function Generator (1Hz – 1MHz.) 1

5 C.R.O - 16 Dual Power Supply 0- 30 V 1

Circuit Diagram:

+ 6 V

R1 6.8 K C = 1 F

C1 = 0.01 FDemodulated O/pReference O/p VCO O/p (fO)

FunctionGenerator(Square Wave)Vi Input CT = 0.001 F

- 6 V

39

10 8 72 63 IC 565 4 9 1 5

Pin Diagram (IC 565 - PLL)

- VCC 1 14 NC

Input 2 13 NC

Output 3 12 NC IC 565

VCO I/P 4 11 NC

VCO O/P 5 10 + VCC

Output 6 9 VCO CT

Demodulated 7 8 VCO RT Output

Procedure:

The connections are given as per the circuit diagram.Measure the free running frequency of VCO at pin 4, with the input signal Vi

set equal to zero. Compare it with the calculated value = 0.25 / (RT CT). Now apply the input signal of 1 VPP square wave at a 1 KHz to pin 2.

Connect one channel of the scope to pin 2 and display this signal on the scope.

Gradually increase the input frequency till the PLL is locked to the input frequency. This frequency f1 gives the lower end of the capture range. Go on increasing the input frequency, till PLL tracks the input signal, say, to a frequency f2.This frequency f2 gives the upper end of the lock range. If input frequency is increased further, the loop will get unlocked.

Now gradually decrease the input frequency till the PLL is again locked. This is the frequency f3, the upper end of the capture range. Keep on decreasing the input frequency until the loop is unlocked. This frequency f4 gives the lower end of the lock range.

The lock range fL = (f2 – f4).Compare it with the calculated value

of 7.8 fo / 12 .Also the capture range is fc = (f3 – f1).Compare it with the calculated value of capture range.

fc = (fL / (2)(3.6)(103) C)1/2

40

TABULAR COLOUMN:

INPUT WAVEFORM OUTPUT WAVEFORM

Square wave Signal

Model Graph

Vc Slope =1/Kv

fo- fL fo- fc

fo fo+ fc fo+fL IB

2fc = Capture range

2fL = Lock- in range

Result :

Thus the PLL circuit is constructed and its Characteristics are determined.

41

FREQUENCY MULTIPLIER USING PLL.

Exp. No : 8 b)

Date :

AIM:

To construct and study the operation of frequency multiplier using IC 565.

Apparatus Required:

S.No Components Range Quantity1 IC 565,IC 7490,2N2222 - 12 Resistors 20 K, 2k,

4.7k,10k1

3 Capacitors 0.001 F 10 F

1 each

4 FunctionGenerator (Digital) 1 Hz – 2 MHz 15 C.R.O - 16 Dual Power Supply 0- 30 V 17.

Circuit Diagram:

1

23

1 9

5

4

7810

2

3

2kohm

20kohm

+6v

10Mf

+6v

2

2 3 6 7 101

5

2N222210kohm

4.7kohm

-6v

0.01Mf

vin

VCO Output

Fo=5fin

565

7490(%5)

RT

RT

RT

C1

0.001Mf

C

42

TABULAR COLOUMN:

INPUT WAVEFORM OUTPUT WAVEFORM

Square wave SignalSquare wave Signal (Multiples of input

freq)

Amplitude (V) Amplitude (V)

Time Period (ms) Time Period (ms)

Procedure:

1. The connections are given as per the circuit diagram.2. The circuit uses a 4- bit binary counter 7490 used as a divide-by-5 circuit.3. Measure the free running frequency of VCO at pin 4, with the input

signal Vi set equal to zero. Compare it with the calculated value = 0.25 / (RT CT).

4. Now apply the input signal of 1 VPP square wave at 500 Hz to pin 2. 5. Vary the VCO frequency by adjusting the 20k potentiometer till the

PLL is locked. Measure the output frequency. It should be 5 times the input frequency.

6. Repeat steps 4, 5 for input frequency of 1 kHz and 1.5 kHz.

Result :

Thus the frequency multiplier circuit using PLL is constructed and studied.

43

EX: NO: 9DATE: LINE CODING AND DECODINGAim:

To construct and study the line coding sequence kit.Apparatus Required:1. Line Coding and Decoding Kit 2. Connecting Plugs3. CRO

BLOCK DIAGRAM TRANSMITTER

RECEIVER

44

VOICE DECODER

MARKER GENERATOR

MULTIPLEXER

AMI/MANCHESTERCODE

8 – BIT DATATRANSMIT

TIMING CONTROL

8- BITDATA RECEIVE

VOICE DECODER

DEMULTIPLEXER

TIMING AND CONTROL

MARKERREFERNCE

MARKER DETECTION

DECODER AND CLOCK RECOVERY

Tabular Column:


TIME PERIOD (s)

Carrier

Modulating

Modulated

Model graph

Result: The Line coding and decoding circuit is constructed and its output Waveforms are plotted.

45

Error Control Coding using MATLAB.

EXNO: 10DATE:

AIM: To perform error control coding(linear block code)using MATLAB program.

ALGORITHM:

STEP 1: Start the program.STEP 2: GET the two signals STEP 3: perform the operation by generate matrixfinding hamming code STEP 4:display the o/p sequenceSTEP 5:display the possible codeSTEP 6: Stop the program.

PROGRAM:

INPUT:

OUTPUT:

RESULT:

46

EXNO: 11 a)DATE:

SAMPLINGAim:

To construct and study the sampling conceptApparatus Required:1. Sampling Kit 2. Connecting Plugs3. CROSAMPING & RECONSTRUCTION BLOCK DIAGRAM

Theory:1. Sampling is the process by which an analog signal is converted into a

corresponding sequence of samples that spaced uniformly in time (i.e. Equally spaced in time).

2. It is necessary to choose the sampling rate property, so that the sequence of samples uniquely defines or recovers the original analog signal.

3. A band limited signal, which has no spectral components above the frequency fm hz, is uniquely determined by its values at uniform intervals less than 1/2fm seconds apart.

4. The reciprocal of sampling period is called the sampling frequency or sampling rate (i.e) fs 1/Ts. This ideal from of sampling is called “Instantaneous Sampling”.

47

SAMPLIG FREQUENCYSELECTION CIRCUIT

BINARY COUNTER

MUX

1 KHz I/P

SAMPLING CIRCUIT

SAMPLE AMP SAMPLE O/P

I/P SIGNAL

SAMPLE AMPSAMPLE HOLD

O/P

DUTY CYCLE CONTROLLER CIRCUIT

BCDCOUNTER

4- BITCOMPARATOR

DUTY CYCLE SELEC

TOR

LATCH

2ND ORDER LPFDEMOD O/P

4TH ORDER LPFDEMOD O/P

LOW PASS FILTER

LOW PASS FILTER

1

2

OSC

Carrier signal

5. If the signal is sampled at an equal or uniform intervals it is known as “uniform sampling”

Tabular Column:


TIME PERIOD (s) Freq(HZ)

Carrier

Modulating

Modulateda)Sampled o/pb)Sample&holdc)Flattopsample

Procedure:


MODEL GRAPH

Result:

The Sampling circuit is constructed and its output waveforms are plotted.

48

EX:NO: 11 b)DATE:

TIME DIVISION MULTIPLEXINGAim:

To construct and study the TDM Circuit and draw its waveforms. Apparatus Required:

1. TDM Trainer Kit 2. Connecting Plugs3. CRO

Block Diagram:

I/P

O/P

Tabular Column:


TIME PERIOD (s)

Frequency(HZ)

Carrier(clk)

Modulating1Modulating2Modulating3 Modulating4

Modulated

Demodulated

Ton=Toff=

49

Channel 1 0

Channel 2 0

Channel 3 0

Channel 0 0 MUX

Tx clk

TXD Ch0

6.4 MHzCrystal Osc.

DecadeCounter

De - MUX

Rx clk

RXD Ch0

LPF

LPF

LPF

LPF

Channel 1 0

Channel 2 0

Channel 3 0

Channel 0 0

DecadeCounter

6.4 MHzCrystal Osc.

PROCEDURE:

Give the connection as per the circuit diagram The input waveform is noted on the CRO The modulated signal and the output waveform is noted on the CRO

Result:

The TDM circuit is constructed and its output waveforms are plotted.

50

ec2307-new digital communication lab manual odd 2011

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