COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMIT

DEPARTMENT OF ELECTRONICS AND DEPARTMENT OF ELECTRONICS AND DEPARTMENT OF ELECTRONICS AND DEPARTMENT OF ELECTRONICS AND

TELECOMMUNICATION ENGINEERINGTELECOMMUNICATION ENGINEERINGTELECOMMUNICATION ENGINEERINGTELECOMMUNICATION ENGINEERING

SVMIT, BHARUCHSVMIT, BHARUCHSVMIT, BHARUCHSVMIT, BHARUCH

Communication EngineeringCommunication EngineeringCommunication EngineeringCommunication Engineering

Institute ElectiveInstitute ElectiveInstitute ElectiveInstitute Elective

Subject Code:

B.E. II (4th



SVMIT, BHARUCHSVMIT, BHARUCHSVMIT, BHARUCHSVMIT, BHARUCH


Institute ElectiveInstitute ElectiveInstitute ElectiveInstitute Elective----I I I I

Subject Code: 141102

th Sem.) (………………………




(………………………)

CERTIFICATECERTIFICATECERTIFICATECERTIFICATE This is to certify that Mr./Ms………………….

………………………………………………….Of B.E.…

Semester……Enrollment No …………….……………. Branch

……………………….has been found satisfactory in the continuous

internal evaluation of the laboratory, practical and term work in the subject

…………………… for the academic year 20… – 20…

Date: Sign. of teacher:

INDEX Sr. No. Title Date Sign Marks/

Grade

EXPERIMENT 1 Date ___________

DSB-AM TRANSMITTER AND MEASUREMENT OF MODULATION

INDEX USING TRAPEZOIDAL METHOD

AIM : To study the working of Double Side Band Amplitude Modulation

(DSB-AM) Transmitter.

APPARATUS : (1) DSB AM Trainer Kit

Model No. ST 2201, Transmitter

(2) Connecting probes.

(3) Power cord.

(4) C.R.O.

(5) C.R.O. Probes.

PROCEDURE : (1) Connect the probes at the indicated points from figure in the

given trainer kit.

(2) Adjust frequencies and gain at different points and observe

the transmitted signal.

(3) Observe the waveforms at different points using C.R.O.

(4) Draw the observed waveforms.

(5) Observe the effect of change in amplitude of information

signal on modulated signal.

(6) Use trapezoidal method to measure the modulation index

(7) Connect X channel of CRO to output of audio amplifier and

Y channel of CRO to output of output amplifier.

(8) Place CRO in X-Y mode.

(9) Using Lissajous pattern find Emax and Emin.

(10) Find modulation index % ma = [(Emax-Emin)/(Emax+Emin)] x

100%.

GRAPHS : (1) Audio Signal (2) Carrier Signal

(3) BM – BPF Output (4) Output Amplifier

(5) Lissajous patterns for modulation index measurement

CONCLUSION :

CIRCUIT BLOCK DIAGRAM :

Marks/Grade Teacher’s Signature

(1)

(2)

(3) (4)

Antenna

Audio Oscillator

Freq Amp

Balanced

Modulator with

carrier

reinsertion and

BPF

Output Amplifier

Gain

Audio Amplifier

Gain

1 MHz crystal

oscillator (carrier)

Speaker


DSB-AM RECEIVER

AIM : To study the working of Double Side Band Amplitude Modulation

(DSB-AM) Receiver.


Model No. ST2201 for transmitter, ST 2202 for Receiver


(3) Power Cord.

(4) C.R.O.

(5) C.R.O. Probes.

PROCEDURE : (1) Connect the transmitter output to receiver input.



(3) At the receiver side observe the waveforms at different points

using C.R.O.

(4) Adjust gain & freq. properly at different points and try to get

the recovered audio signal same as input.

GRAPH : (1) RF Amplifier Output (2) Local Oscillator Output

(3) Mixer Output (4) IF Amplifier-2 Output

(5) Diode Detected Output (6) Audio Amplifier Output.

CONCLUSION :



Antenna

Rf

Amplifier

Gain

Mixer

If

Amplifier-

1

Tuning

Local

Oscillator

Speaker

If

Amplifier -

2

Diode

Detector

Audio

Amplifier

Gain (variable)

(3) (4) (5)

(2)

(1)

(6)


DSB – AM WITH AGC CIRCUITS

AIM : To study working of Double Side Band Amplitude Modulation

(DSB-AM) with AGC (Automatic Gain Control) Circuits


(2) Model No. ST2201 for transmitter, ST 2202 for Receiver


(4) Power Cord.

(5) C.R.O.

(6) C.R.O. Probes.

(7) Digital Multimeter

PROCEDURE : (1) Connect the transmitter output to receiver input.




using C.R.O.

(4) Adjust gain & freq. properly at different points and try to get

the recovered audio signal same as input.

(5) Connect the DMM at the input of AGC circuits and note the

AGC voltage

OBSERVATION TABLE :

Output Amplifier P- P Voltage

Sine Wave (V)

AGC Voltage (V)

CONCLUSION :

CIRCUIT BLOCK DIAGRAM

RECEIVER


Tuning Speaker

Antenna

RF Amplifier

Gain Mixer

IF

Amplifier-1

IF

Amplifier-2

Diode

Detector

Audio

Amplifier

Local

Oscillator

AGC

Circuit


SSB-AM TRANSMITTER

AIM : To study the working of Single Side Band Amplitude Modulation

(SSB-AM) Transmitter.

APPARATUS : (1) SSB AM Trainer Kit

Model No. ST 2201, for transmitter.


(3) Power Cords

(4) C.R.O.

(5) C.R.O. Probes

PROCEDURE : (1) Connect the probes at the indicated point from figure in the

given trainer kit.



(3) Observe the waveforms at different points using C.R.O.

(4) Draw the observed waveforms.


(3) BM – BPF Output (4) Output Amplifier.

CONCLUSION :

CIRCUIT DIAGRAM :

(1) (2)

(3) (4)


Audio

Oscillator

Amplifier Frequency

Audio

Amplifier Balance

Modulator Ceramic BPF

BM BPF

Balance

1 MHz

Crystal

Oscillator

455 KHz

Oscillator

Antenna

Output

Amplifier

Gain

Speaker


SSB - AM RECEIVER

AIM : To study the working of Single Side Band Amplitude Modulation

(SSB-AM) Receiver.

APPARATUS : (1) SSB AM Trainer Kit

(2) Model No. ST2201 for transmitter, ST 2202 for

Receiver


(4) Power Cord.

(5) C.R.O.

(6) C.R.O. Probes.

PROCEDURE : (1) Connect the probes at the indicated point from figure in the

given trainer kit.




on C.R.O.

(4) Adjust gain and frequecy properly at different points. And try

to get the recovered audio signal same as input.



(5) Product Detector Output (6) Audio Amplifier Output.

CONCLUSION :

CIRCUIT DIAGRAM :


RF Amp

Gain IF Ampr-1 Mixer

Tuning Local Osc Beat Freqn

Osc

Audio Amp

Gain

Product

Detector IF Ampr-2

Speaker

Antenna


FM TRANSMITTER

AIM : To study Frequency Modulation (FM) Transmitter.

APPARATUS : (1) Trainer kit: Model ST 2203.

(2) Connecting Probes

(3) CRO

(4) CRO Probes.

(5) Power Cord.

PROCEDURE : (1) Connect the links in the circuit as shown in the circuit

diagram.

(2) Switch ‘ON’ the supply.

(3) Now observe the FM transmitted wave on CRO.

(4) Draw the waveforms.

CONCLUSION :


(3) FM Modulated Output (4) Output Amplifier.



Audio

Oscillator

FM Modulator

Varactor/

Reactance

Output

Amplifier

Carrier

Generator

Information Signal

FM output


.

FM RECEIVER

AIM : To study Frequency Modulation (FM) Receiver.

APPARATUS : (1) Trainer kit: Model ST 2203.

(2) Connecting Probes

(3) CRO

(4) CRO Probes.

(5) Power Cords.

PROCEDURE : (1) Connect the transmitter output to receiver input


(3) Now observe the FM transmitted wave on CRO.

(4) Now observe the received waveform on CRO.



(5) Demodulated Output (6) Audio Amplifier Output.

CONCLUSION :



Amplitude

Limiter

FM Detector

Foster Seeley/

Ratio/

PLL/

Detuned Resonant Circuit

LPF +

Amplifier

FM input

Audio

output


SAMPLING & RECONSTRUCTION CIRCUIT

AIM : To study the sampling and reconstruction circuits.

APPARATUS : (1) Trainer Kit (Model ST 2101)


(3) Power Cords.

(4) CRO

(5) CRO Probes.

PROCEDURE : (1) Connect the probes at the indicated points from figure in the

given trainer kit.


the sampled signal.


on CRO and note working of the circuits.

(4) Watch the reconstruction of the signal at the output and

observe the signal on CRO.

GRAPH : (1) Analog Signal (2) Sampling Pulses

(3) Sample Output (4) Sample and Hold Output

(5) Second order LPF Output (6) Forth Order LPF Output.

For Different Sampling Frequencies.

CONCLUSION :



Sampling

Frequency

Selection

Circuit

(2K,4K,8K,

16K, 32K) Hz

Second Order

LPF

Analog

Signal

Buffer

4th

Order LPF

Signal

Generator 1KHz

Duty Cycle

Control Circuit

Buffer

Buffer

Sample

Output

Sampling Circuit

Sample and

Hold Output

(2) +1 (5)

(3)

(4)

(1)

(6) output


TDM-PCM TRANSMITTER AND RECEIVER

AIM : To study the working of TDM-PCM (Time Division Multiplexing-

Pulse Code Modulation) Transmitter and Receiver

APPARATUS : (1) TDM-PCM Trainer Kit. ST-2103 and 2104

(2) Connecting Probe

(3) Power Cords

(4) C.R.O.

(5) CRO Probes.

PROCEDURE : (1) Connect the probes properly in the circuits according to the

diagram of TDM-PCM as shown.


(3) From function generator, apply DC as well as different

frequency AC signals one by one,

(4) Select a data to be transmitted.

(5) Observe the received data at the receiver side and observe the

waveforms on the CRO also.

(6) Now select parity odd and observe the error detection at

receiver side.

(7) Now select parity even and observe error detection at

receiver side.

GRAPH : (1) Transmitted Data (2) Received Data without Parity

(3) Received Data With Even Parity (4) Received Data With

Odd Parity

CONCLUSION :

CIRCUIT DIAGRAM:



SETTING UP FIBER OPTIC ANALOG AND DIGITAL LINK

AIM : To study a 650 mm fiber optic analog and digital link- the

relationship between the input signal and received signal.

APPARATUS : (1) Trainer Kit. ST-2501

(2) Connecting Probe

(3) Power Cords

(4) C. R. O.

(5) Optical Fiber.

PROCEDURE

(1) Connect the power supply to the board.

(2) Ensure that all switched faults are off.

(3) Make the following connections. (As shown in diagram 1).

(a) Connect the function generator 1 KHz sine wave

output to emitters’ input.

(b) Connect the fiber optic cable between emitter output

and detectors’ input.

(c) Detector output to AC Amplifier input.

(4) On the board, switch emitter driver to Analog mode.

(5) Switch ON the power.

(6) Observe the input to emitter (t.p. 5) with the output from AC

Amplifier (t.p. 19) and note that the two signals are same.

(7) Connect the function generator 1 KHz square wave output to

emitters’ input.

(8) Repeat the procedure by switching emitter driver to Digital

mode and follow the diagram 2 for connections.

GRAPH : (1) Transmitted Signal (2) Received Signal for both cases

CONCLUSION :

CIRCUIT DIAGRAM:

Fig. 1

Fig. 2



TELEVISION SIGNAL PATTERN GENERATOR AIM : To study television signal pattern generator and to obtain different

patterns on color TV receiver.

APPARATUS : (1) Color TV receiver

(2) Pattern generator

(3) Connecting cables

(4) C. R. O.

THEORY :

Front panel of pattern generator:-

Control sockets and their functions of pattern generator.

1. Pattern Selector:-

This is a 12 way switch used for selecting the requisite patterns. (The indicated

patterns will be available from the RF and Video outputs only when the push button switch

4 is in the out position.)

2. CH 4 / IF-RF:-

This push button is used in conjunction with switch 2a below and is used to select

the IF or CH4 output, available at connector 8.

2a. CH selector:-

This comprises of a two way rotary switch and a multiturn potentiometer. When

switch is set to CH5-CH12 the potentiometer can be adjusted to any desired channels

between CH5 and CH12. For making this adjustment connects a TV to a known

transmission channel or CATV channel. Then connect the RF output and fine tune the

potentiometer for a stable pattern display. This adjustment may have to be verified from

time to time.

3. 5.5 MHz ON/OFF sound:-

The 5.5 MHz sound carrier which is FM modulated by 1 KHz sine wave can be put

ON/OFF by this switch.

4. 1 KHz / EXT (DECODER) sound:-

This has dual function one in sound and other in chroma. If external sound

modulation is required then set the Pattern selector switch to any position of the three black

and white (B/W) patterns and press button 4. By releasing the button, internal 1 KHz

will modulate the RF signal. If the Pattern selector is set to any of the colour pattern and

the above procedure is followed, then the colour will disappear.

5. ON / OFF Burst:-

This push button will enable/disable the burst in the video signal. This feature is used

in troubleshooting the colour killer circuitry of the TV receiver.

6. ON / OFF Rhombus:-

This pattern is very useful for adjustment of the aspect ratio of the picture and also the

linearity. This pattern can be superimposed on any of the patterns selected by the Pattern

Selector. The linearity is best adjusted when this pattern is superimposed on the crosshatch

pattern.

7. ON / OFF Mains:-

This switch connects/disconnects power to the generator. An LED indicates when

power is on.

8. Output RF:-

This is a co-axial output for the RF signal. This output should be connected to the TV

by 75Ω cable.

9. Attenuator RF:-

This is a switched attenuator with a total attenuation of 75 dB approx. in steps of -

10 dB, -5 dB and 3× -20 dB. These switches can be used in any combination to provide the

most suitable signal output required. It is possible to compare the sensitivity of various TV

sets from point of view of gain, colour loss threshold, sync loss threshold, presence or

absence of oscillations etc. by judicious use of the attenuator. The attenuator is optimized

for IF and CH4 with inaccuracy being about 3 dB in 75 dB attenuation. The attenuator is

also very useful in isolating faults specially related to gain in the IF section of the TV

receiver.

10. Earth:-

The instrument earth connection is used along with sockets 11, 12, 13 as the earth

return path for the signal.

11. EXT Audio IN:-

2mm socket for connecting the external audio input, the switch 4 should be set to

EXT (refer 4 above). The usable range is 200 Hz to 7 KHz approximately. This feature is

very useful for checking out the loud speaker rattling and also for loose hardware or

component inside the cabinet.

12. Line Trig / Frame Trig :-

Line and frame sync signals are available separately at these sockets. These outputs

can be used to externally synchronies the oscilloscope which will ease triggering;

especially when the sweep rates are varied.

13. Video Output:-

Fixed video output of 1 V (p-p) is available at this socket when the output is

terminated in 75 Ω. Care should be taken to ensure that no voltage is fed into this socket as

this may damage the equipment.

14. Sound Output:-

5.5 MHz carrier along with the 1 KHz modulation is available at this co-axial socket.

The effect of all combinations of the various switches affecting the sound will be reflected

on this output. This output can be used for adjusting the 5.5 MHz coils/traps in the TV

receiver.

Applications of various test patterns.

1. Dot pattern:-

It is used mainly for checking static convergence in a CTV. The dots should be pure

whit on black background. Presence of more than one colour implies that one or more

electron beam is passing the wrong hole in the shadow mask.

2. Cross Hatch Pattern:-

This is mainly used for checking and aligning the dynamic and corner convergence of

the picture tube. i.e. Pincushion Correction

3. Checkerboard Pattern:-

It is a visual quick check for centering, focus and vertical & horizontal linearity. The

transition from black to white and white to black gives an indication of the bandwidth.

These transitions should be sharp. Vertical lines at the transitions are an indication of

ringing, gray zone is an indication of poor bandwidth. Hum interference on

synchronization is also visible on this pattern as waviness at the transitions.

4. Colour Bar Pattern:-

It is a standard colour bar. The vertical bars are white, yellow, cyan, magenta, red,

blue & black. This pattern provides sufficient check for a good overall check on a CTV

performance; such as burst keying, subscriber regeneration, RGB amplifiers, delay versus

B/W signal and saturation check.

5. White Pattern:-

It can be used for white setting and check of colour purity. This pattern can also be

used for making the maximum beam current adjustment.

6. Purity Patterns:-

These patterns can be used for checking colour purity as well as to ensure that there is

no interference between sound and chroma carrier. The red pattern is generally used for

colour purity checks. In a properly adjusted TV sets the electron beam will strike only one

set of colour dots or stripes on the TV screen. With red pattern only red colour should be

visible, if any other colour is present than colour purity needs adjustment.

7. Black Pattern:-

Black pattern indicates no video information. No video information can be used to

check the front and back porches the sync pulses.

8. Linearity pattern:-

It is generally used to adjust height and width so that the TV delivers a picture with

the correct aspect ratio of 4:3. It can be superimposed on any pattern. The pattern consists

of a rhombus with two diagonal lines. For correct adjustment the corners of the rhombus

should just touch the sides and the diagonal lines should pass through the corners of the

picture tube.

Normally the linearity pattern is superimposed on the crosshatch pattern for the

adjustment.

With the linearity pattern on keep changing the patterns from colour bar red, blue…

so on. The size of the rhombus may change slightly with different colours. If the change is

pronounced it implies that the EHT regulation is poor thereby the picture quality will be

affected depending on the colour content.

PROCEDURE:

1. Connect the output of the pattern generator using RF cable to the TV set.

2. Observe the different video pattern generated by pattern generator on the TV set.

3. Connect the Video output of the pattern generator using probe to the CRO input.

4. Observe the different waveforms of the video signal on the CRO.

5. Draw the different waveforms of composite video signal.

GRAPH : Composite video Signal for monochrome and color signal pattern

CONCLUSION :


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COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMIT