Communication Lab_2013 (1)

SHANMUGHAARTS, SCIENCE, TECHNOLOGY AND RESEARCH ACADEMY

(SASTRA University)TIRUMALAISAMUDRAM

THANJAVUR – 613 401.

COURSE CODE : BECCEC506R01 / MCSCEC506R01COURSE NAME : COMMUNICATION LABORATORY

BRANCH: ELECTRONICS AND COMMUNICATION ENGINEERINGSEMESTER: V

2013

LIST OF EXPERIMENTS

1. Amplitude modulation and demodulation

2. Frequency modulation and demodulation

3. Signal Reconstruction from Samples

4. Pulse amplitude modulation, Pulse width modulation and Pulse position modulation and

demodulation

5. Amplitude shift keying (ASK) and Frequency shift keying (FSK)

6. Binary Phase shift keying (BPSK), Quadrature Phase shift keying (QPSK) and QAM

7. Time division multiplexing (TDM)

8. Manchester coding and decoding

9. Fiber optic communication-propagation loss and bending loss

10. Noise generator

11. Pulse Code Modulation and Demodulation

12. Differential Pulse Code Modulations and Demodulation

AMPLITUDE MODULATION AND DEMODULATION

EXP. No. : Date :

AIM:

1. To generate and study amplitude modulated waveform using emitter modulator circuit with the given carrier frequency f o =

2. To plot the graph between modulating signal amplitude and modulation index 3. To find the modulation index for various modulating signal amplitudes 4. To find the modulation index using trapezoidal method5. To detect the given AM signal by using envelope detector. 6. To plot the output waveforms

COMPONENTS REQUIRED:

Sl.No. Components Type/ Range / Value Quantity

1.BJT BF 195 1

2.Diode IN4001 1

3.Resistor 100Ω, 220Ω, 1KΩ, 5.6KΩ,10 KΩ 1 Each

4.Capacitor 10μF, 0.02μF, 0.01μF 2,1 ,1

5.Power supply (0 – 30)v 1

6.AFO 1

7.CRO 1

8.DIB 1

CIRCUIT DIAGRAM:

Modulator:

Demodulator:

DESIGN FOR MODERATOR

Given Carrier frequency fc = 16 KHz

Modulating frequency fs = 1 KHz

fc = 1/ 2π√LC

Let C = 0.02µf , Then L = 5mH

PROCEDURE FOR MODULATOR

1. Give the circuit connection as per the diagram

2. Measure the DC voltage at collector, base, and emitter with respect to reference ground

3. Apply the carrier to the base of the transistor and modulating signal to the emitter

4. Get the modulated waveform at the output using CRO and find modulation index using the formula:

m = Emax – Emin / Emax+ Emin

5. Vary the amplitude of the modulating signal and find the modulation index

6. Tabulate the readings

7. Plot the graphs of modulating signal, carrier signal and modulated signal

8. Also plot the graph between the modulated wave and modulation index

TRAPEZOIDAL METHOD

1. Apply the modulated wave to channel A of the CRO and the modulating signal to channel B and keep the CRO Time/division knob in XY position.

2. Get the trapezoidal display of modulation and find the modulation index using the formula m = (L1 – L2) / (L1 + L2)

3. For particular amplitude of the modulating signal find m and check whether it tallies with the graph.

PROCEDURE FOR DEMODULATOR

1. Rig up the circuit as shown in the figure.

2. Apply the AM signal from the modulator output.

3. Observe the demodulated output in the CRO.

TABULATION

MODULATOR:

DEMODULATOR:

MODEL GRAPH:

Demodulated result

RESULT:

FM MODULATION AND DEMODULATION

EXP. No. : Date :

AIM:

1. To generate frequency modulated waveform using XR2206.

2. To detect the given FM wave using Phase Locked Loop (PLL)



1.IC XR2206 - 1

2.Resistors 200Ω, 470 Ω ,100KΩ ,100Ω , 12KΩ, 10KΩ 1,2,1,1,1,1

3.Capacitors 100pF, 0.1μF , 0.01μF,

10μF,0.001μF1 Each,1

4.AFO, RPS, CRO - 1

5.IC 565

-1

6.DRB

-1

CIRCUIT DIAGRAM:

Modulator

Demodulator:

PROCEDURE FOR MODULATOR

1. Give the circuit connection as per the diagram

2. Apply the modulating signal

3. Observe the frequency modulated output

4. Vary the amplitude of the modulating signal and note the changes in the FM output.

PROCEDURE FOR DEMODULATOR

1. Make the connection of PLL as shown in the figure

2. Measure the free running frequency of VCO at pin 4, with the input signal V ¿equal to zero. Compare it with calculated value = 1. 2 / 4RTCT

3. Give the FM signal at pin.2

4. Compute the lock range and capture range frequencies using formula given in step 5 compare it with the practical values

5. The lock range f L and capture range f C of the PLL are

f L = ± 8 f out / (+V) – (-V)

f C = ± [f L /2π (3.6) (103) C¿1 /2

Where f out is the free running frequency of VCO

6. Take the demodulated output from pin.7

MODEL GRAPH

Demodulator Result

RESULT:

SIGNAL RECONSTRUCTION FROM SAMPLES

EXP. No. : Date :

AIM: To generate a sampled form of analog signalTo reconstruct original signal from sampled signal.


1. Sampling theorem verification circuit2. Function Generator (1MHz)3. Dual trace oscilloscope (20 MHz)

Circuit Diagram:

Fig: 1 Sampling Circuit

Fig: 2 Reconstructing Circuit

PROCEDURE:

1. The circuit is connected as per the circuit diagram shown in the fig 1.

2. Switch on the power supply. And set at +11V and -11V.

3. Apply the sinusoidal signal of approximately 4V (p-p) at 105Hz frequency and pulse signal of 11V (p-p) with frequency between 100Hz and 4 KHz.

4. Connect the sampling circuit output and AF signal to the two inputs of oscilloscope

5. Initially set the potentiometer to minimum level and sampling frequency to 200Hz and observethe output on the CRO. Now by adjusting the potentiometer, vary the amplitude of modulating signal and observe the output of sampling circuit. Note that the amplitude of the sampling pulses will be varying in accordance with the amplitude of the modulating signal.

6. Design the reconstructing circuit. Depending on sampling frequency, R & C values are calculatedusing the relations Fs = 1/Ts, Ts = RC. Choosing an appropriate value for C, R can be found using the relation R=Ts/C

7. Connect the sampling circuit output to the reconstructing circuit shown in Fig 2

8. Observe the output of the reconstructing circuit (AF signal) for different sampling frequencies. The original AF signal would appear only when the sampling frequency is 200Hz or more.

OBSERVATION:

RESULT:

PULSE AMPLITUDE MODULATION & DEMODULATION

EXP. No: Date :

AIM: To generate the Pulse Amplitude modulated and demodulated signals.



1.Resistors 1K, 10 KΩ, 100 KΩ , 5.8 KΩ, 2.2 KΩ Each one

2.Transistor BC 107 2

3.Capacitor 100 μF, 0.001 μF Each one

4.CRO 30MHz 1

5.Function generator 1MHz 1

6.Regulated Power Supply 0-30V,1A 1

7.CRO Probes - 1

CIRCUIT DIAGRAM:

PROCEDURE:

1. Connect the circuit as per the circuit diagram shown in the fig 3

2. Set the modulating frequency to 1 KHz and sampling frequency to 12 KHz

3. Observe the o/p on CRO i.e. PAM wave.

4. Measure the levels of Emax & Emin.

5. Feed the modulated wave to the low pass filter as in fig 4.

6. The output observed on CRO will be the demodulated wave.

7. Note down the amplitude (p-p) and time period of the demodulated wave. Vary the amplitude and frequency of modulating signal. Observe and note down the changes in output.

8. Plot the wave forms on graph sheet.

MODEL GRAPH:

Modulator output

Demodulator output:

RESULT:

PULSE WIDTH MODULATION AND DEMODULATION

EXP. No. : Date :

AIM: To Generate the Pulse Width Modulated and Demodulated Signals



1.Resistors 1.2 KΩ, 1.5 KΩ, 8.2 KΩ 1,1,2

2.Capacitors 0.01 μF, 1 μF 2,2

3.Diode 0A79 1

4.CRO 0-30, MHz 1

5.Function Generator 1MHz 1

6.RPS 0-30v,1A 1

7.IC 555 Operating tem :SE 555 -55degC to 125deg C

NE 555 0deg to 70deg C Supply voltage :+5V to +18V Timing :µSec to Hours Sink current :200mA temperature stability :50 PPM/deg C change in temp or 0-005% /deg C.

1

8.CRO Probes - ----- 1

Circuit diagram:

PROCEDURE:

1. Connect the circuit as per circuit diagram shown in fig 1.

2. Apply a trigger signal (Pulse wave) of frequency 2 KHz with amplitude of 5v (p-p).

3. Observe the sample signal at the pin3.

4. Apply the ac signal at the pin 5 and vary the amplitude

5. Note that as the control voltage is varied output pulse width is also varied.

6. Observe that the pulse width increases during positive slope condition & decreases under negative slope condition. Pulse width will be maximum at the +ve peak and minimum at the –ve peak of sinusoidal waveform. Record the observations.

7. Feed PWM waveform to the circuit of Fig.2 and observe the resulting demodulated waveform.

TABULATION

MODEL GRAPH:

Modulator:

Demodulator:

RESULT:

PULSE POSITION MODULATION & DEMODULATION

EXP. No. : Date :

AIM: To generate pulse position modulation and demodulation signals and to study the effect of amplitude of the modulating signal on output.


Sl.No.

Components Type/ Range / Value Quantity

1.Resistors 3.9k, 3k, 10k, 680k Each one

2.Capacitors 0.01µF, 60µF 2,1

3.Function Generator

1MHz 1

4.RPS 0-30v,1A 1

5.CRO 0-30MHz 1

6.IC 555 Operating tem :SE 555 -55degC to 125deg C

NE 555 0deg to 70degC Supply voltage :+5V to +18V Timing :µSec to Hours Sink current :200mA Temperature stability :50 PPM/deg C change in temp or 0-005% /deg C.

1

7.CRO Probes ----- 1

CIRCUIT DIAGRAM:

Fig: 1 Pulse Position Modulation Circuit

PROCEDURE:

1. Connect the circuit as per circuit diagram as shown in the fig 1.

2. Observe the sample output at pin 3 and observe the position of the pulses on CRO and adjust the amplitude by slightly increasing the power supply. Also observe the frequency of pulse output.

3. Apply the modulating signal, sinusoidal signal of 2V (p-p) (ac signal) 2v (p-p) to the control pin 5 using function generator.

4. Now by varying the amplitude of the modulating signal, note down the position of the pulses.

5. During the demodulation process, give the PPM signal as input to the demodulated circuit as shown in Fig.2.

6. Observe the o/p on CRO.

7. Plot the waveform.

MODEL GRAPH:

Modulator:

Demodulator:

RESULT:

AMPLITUDE SHIFT KEYING (ASK) AND FREQUENCY SHIFT KEYING (FSK)

EXP. No. :

Date :

AIM: To generate ASK for the given input signal using 555 timer.


PROCEDURE:

1. Rig up the circuit as shown in figure.

2. Connect carrier signal

3. Verify the output through CRO.

CIRCUIT DIAGRAM:

MODEL GRAPH:

TABULATION:

RESULT:

FREQUENCY SHIFT KEYING

Ex.No:

Date:

AIM: To generate FSK for the given input signal using 555 timer


PROCEDURE:

1. Rig up the circuit as shown in figure.

2. Connect carrier signal

3. Verify the output through CRO.

CIRCUIT DIAGRAM:

MODEL GRAPH:

RESULT:

TIME DIVISION MULTIPLEXING:

Ex.No:

Date:

AIM: To investigate 16 channel TDM using digital signals.

COMPONENTS REQUIRED: Trainer kits ST2503 and ST2501/2502, optic fiber, connecting cords, CRO.

PROCEDURE:

1. Make connections as below.

2. Turn on power to the ST2503.

3. Observe multiplexed data on oscilloscope.

4. Connect OUT terminal of multiplexer to IN terminal of demultiplexer.

5. Observe demultiplexed 16 channel output on oscilloscope. Take output signal as

external trigger signal to oscilloscope to trigger demultiplexed output.

6. Connect output of emitter circuit to detector circuit of ST2501 through fiber optic

cable as shown below

7. Connect OUT terminal of multiplexer to IN terminal of emitter circuit.

8. Connect OUT terminal of detector circuit to IN terminal of comparator circuit.

9. Adjust comparator bias to get suitable output.

10. Connect OUT terminal of comparator circuit to IN terminal of 16 channel demultiplexer of ST2503.

11. Repeat step 5.

RESULT:

MANCHESTER CODING AND DECODING

Ex.No: -

Date:

AIM: To investigate Manchester coded and decoded output of a given signal.

COMPONENTS REQUIRED: Trainer Kits ST2503 and ST2501/2502, fiber optic kit, Connecting cords, CRO.

PROCEDURE:

Encoding:

1. Make the connection as shown below.

2. Turn on power to the ST2503 board.

3. Connect CLK and DATA OUT terminal to CLK IN and DATA IN terminal of Manchester encoder

4. Observe encoded output on oscilloscope.

Decoding:

1. Connect output of Manchester encoder to input of Manchester decoder.

2. Observe Manchester decoder output on oscilloscope.

3. This experiment can be performed by passing encoded signal through optic fiber using ST2501/2502.

4. Make connections as shown below and observe the output on CRO.

RESULT:

FIBER OPTIC COMMUNICATION-PROPAGATION LOSS AND BENDING LOSS

Ex.No:

Date:

AIM: The aim of this experiment is to measure propagation and bending loss in optical

fiber.

COMPONENTS REQUIRED: Fiber optic kit, Connecting cords, two optical fibers (1m and 0.5m length), CRO, mandrel.

PROCEDURE:

1. Connect power supply to board.

2. Make the following connections (as shown in the figure).

a. Connect function generator 1Khz sine wave output to input 1 socket of emitter circuit.

b. Connect 0.5m optic fiber between emitter 1 output and detector 1 input.

c. Connect detector 1 output to amplifier 1 input.

d. Connect the output from amplifier to CRO.

3. Switch on the power supply.

4. Set the oscilloscope channel 1 to 0.5V/div and 4-6div amplitude by using X1 probe with the help of variable pot in function generator block at input.

5. Observe the output signal from detector tr10 on CRO.

6. Adjust the amplitude of the received signal same as that of transmitted one with the help of gain adjust pot. In AC amplifier block. Note this amplitude as V1.

7. Now replace the previous FO cable with 1m cable without disturbing any previous setting.

8. Measure the amplitude at the receiver side again at output of amplifier 1 socket

tp28.Note this as V2.

9. Calculate the propagation constant or attenuation constant “α” with the help of following

FORMULA:

V 1

V 2 = e^-α(L1-L2 )

Where “α” is loss in nepers/meter.

1 neper=8.686 dB.

L1=length of shorter cable (0.5m) L2=length of longer cable (1m)

TRAINER SETUP:

TABULATION:

BENDING LOSS:

1. Repeat all the steps from 1 to 6 of the previous experiment (propagation loss experiment) using 1m cable.

2. Wind the FO cable on the mandrel and observe the corresponding AC amplifier output on CRO. It will be gradually reducing showing loss due to bends.

3. Note the output voltage in CRO for 0, 1, 2, and 3 bends

TRAINER SETUP:

OBSERVATION:

RESULT:

NOISE GENERATOR

Ex.No:

Date:

AIM: To design a circuit that generate noise signal.


Noise generator circuitAmplifier circuitActive low pass filter circuitSpeaker

BLOCK DIAGRAM:

CIRCUIT DIAGRAM:

RESULT:

BINARY PHASE SHIFT KEYING (BPSK)

EXP. No: Date :

AIM: To generate BPSK signal To recover original I/P signal from BPSK signal


BPSK Transmitter, BPSK Receiver Connecting cords, CRO

KIT SETUP:

OBSERVATION:

RESULT:

QPSK MODULATION/DEMODULATION

EXP. No: Date :

AIM:

To generate QPSK signal To recover original I/P signal from QPSK signal

To measure the different signal in QPSK generation and detection


QPSK Transmitter, QPSK Receiver Connecting cords, CRO

KIT SETUP:

OBSERVATION:

RESULT:

PULSE CODE MODULATION AND DEMODULATION

EXP. No: Date :

AIM:

To generate PCM signal To reconstruct original I/P signal from PCM signal

To measure the different signal in QPSK generation and detection


Pulse Code Modulation kit, Pulse Code Demodulation kit, Connecting cords, CRO

KIT SETUP:

OBSERVATION:

RESULT:

SIMULINK EXPERIMENTS:

Aim:

The aims of the simulink experients is used to model, simulates and analyze the function of each block in the different modulator and demodulator

Software Requirement:

MATLAB

Block diagram:

DPCM:

QAM:

PCM:

Result:

Communication Lab_2013 (1)

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