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Advanced Communication Lab (06ECL-67) Dept. of ECE 1 BGSIT, BG Nagar VISVESVARAYA TECHNOLOGICAL UNIVERSITY JNANA SANGAMA, BELGAUM-590018 Advanced Communication Lab Manual [SUB CODE: 06ECL67] For VI th Semester Bachelor Degree [Electronics and Communication] Prepared By: Mr. Punith Kumar M.B. Lecturer, Dept of ECE, BGSIT, Mandya. DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING, B.G.S. INSTITUTE OF TECHNOLOGY, BG NAGAR. MANDYA-571448

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Page 1: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 1 BGSIT, BG Nagar

VISVESVARAYA TECHNOLOGICAL UNIVERSITY

JNANA SANGAMA, BELGAUM-590018

Advanced Communication Lab Manual

[SUB CODE: 06ECL67]

For

VIth

Semester Bachelor Degree [Electronics and Communication]

Prepared By:

Mr. Punith Kumar M.B.

Lecturer, Dept of ECE,

BGSIT, Mandya.

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING,

B.G.S. INSTITUTE OF TECHNOLOGY, BG NAGAR.

MANDYA-571448

Page 2: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 2 BGSIT, BG Nagar

1. ASK GENERATION AND DETECTION (BINARY).

AIM: Design & Demonstrate an ASK system to transmit the digital data of _____ bits/sec, using a

suitable carrier signal. Determine the minimum frequency of carrier for a proper detection.

APPARATUS REQUIRED:

Function Generator

15V DC Regulated Power supply

Spring Board

CRO

COMPONENTS REQUIRED:

Transistor SL100

Op-amp μA 741

Diode OA 79

Resistors 680Ω, 560Ω, 10KΩ, 4.7KΩ, 10KΩpot

Capacitors 0.22 F

CIRCUIT DIAGRAM:

DEMODULATION:

Page 3: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 3 BGSIT, BG Nagar

DESIGN:

(a.) MODULATION:

ICsat = 2mA; hfe = 30% = 0.3; VBEsat = 0.7V; VCEsat = 0.2v

We know that IB =IC/ hfe

= 3.0

2mA

IB = 6.667mA

Also RE = VE/IE == (Vc-VCE)/IE (IE=IB+IC)

= (5-0.2)/8.667mA

= 553.82Ω=560 Ω

Also RB= (Vm-VBE-VE)/IB

=(10-0.7-0-4.8)/ IB

RB=675 Ω =680 Ω

(b.) DEMODULATION:

We know that 1/fc < R x C < 1/fm

Take fcmax = 10 kHz

Then, 1/10 kHz < R x C <1/1 kHz

Implies, 0.1ms< R x C < 1ms.

Take RC = 2.2ms, and let C = 0.22 F

Then R = 1KΩ

PROCEDURE:

1. Circuit is rigged up as shown in the circuit diagram. 2. Carrier wave and message is given at the input of switching circuit. 3. ASK signal can be obtained from emitter terminal. 4. Demodulation of ASK is done by envelope detector followed by filter and comparator.

Page 4: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 4 BGSIT, BG Nagar

MODEL WAVEFORMS:

MODULATION WAVEFORMS:

DEMODULATION WAVEFORMS:

Page 5: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 5 BGSIT, BG Nagar

2. FSK GENERATION AND DETECTION (BINARY)

AIM: Design & Demonstrate the working of FSK with a suitable circuit for carrier signals of ____Hz &

____Hz, determine the frequency deviation & modulation index. Demodulate the above signal with the

help of suitable circuit.

APPARATUS REQUIRED:

Function Generator

15V DC Regulated Power supply

Spring Board

CRO

COMPNENTS REQUIRED:

Transistor SL100, SK100

Op-amp μA 741 2nos

Diode OA 79

Resistors 680Ω2nos, 560Ω2nos, 10KΩ3nos, 20KΩ, 5.6KΩ, 10KΩpot

Capacitors 0.1 F 3nos, 0.22 F CIRCUIT DIAGRAM:

Page 6: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 6 BGSIT, BG Nagar

DEMODULATION:

DESIGN:

(a.) MODULATION:

ICsat = 2mA; hfe = 30% = 0.3; VBEsat = 0.7V; VCEsat = 0.2v

We know that IB =IC/ hfe

= 2mA/0.3

IB = 6.667mA

Also RE = VE/IE == (Vc-VCE)IE

= (5-0.2)/8.667mA

= 553.82Ω=560 Ω

Also RB=(Vm-VBE-VE)/IB

=(10-0.7-0-4.8)/ IB

RB=675 Ω =680 Ω

(b.) DEMODULATION:

Design for Ist part

Yfc1<RC<Yfc2

Y5k<RC<Y1k

0.2m<RC<1m

Say RC=0.56m

Let C=0.1 F & R-=5.6kΩ

Page 7: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 7 BGSIT, BG Nagar

Design for IInd part

Y1k<RxCxY100

0.1m<RC<10m

Let RC=2.2m sec

If C=0.22 F & R=10kΩ

PROCEDURE:

1. Rig up the circuit as shown in the circuit diagram. 2. Give two different frequencies for carrier and message to the base of NPN and PNP

transistor. 3. FSK signals are obtained at the inverting amplifier terminal. 4. For demodulation, convert FSK to ASK then demodulate by envelope detector and filter.

MODEL WAVEFORMS:

MODULATION WAVEFORMS:

Page 8: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 8 BGSIT, BG Nagar

DEMODULATION WAVEFORMS:

Page 9: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 9 BGSIT, BG Nagar

3. PSK GENERATION AND DETECTION (BINARY)

AIM: Design & Demonstrate the working of BPSK modulated signals for a given carrier signal of

frequency ____Hz to transmit a given digital data of frequency____ Hz. Demodulate the BPSK Signal to

recover the digital data.

APPARATUS REQUIRED:

Function Generator

15V DC Regulated Power supply

Spring Board

CRO COMPONENTS REQUIRED:

Transistor SL100, SK100

Op-amp μA 741 3nos

Diode OA 79

Resistors 560Ω 2nos, 680Ω 2nos, 10KΩ 6nos,

Capacitors 0.1 F 2nos, 0.22 F

Potentiometer 10KΩ 2nos. CIRCUIT DIAGRAM:

Page 10: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 10 BGSIT, BG Nagar

DEMODULATION:

DESIGN:

ICsat = 2mA; hfemin = 30% = 0.3; VBE = 0.7V; VCEsat = 0.2v

We know that IB = hfe x IC

= 0.3 x 2mA

IB = 0.6mA

Also, RB = (Vm-VBEsat-VE)/IB

= (10V-0.7V-0.2V)/600μA

= 15.166kΩ

Approximating we get, RB = 22kΩ

Also RE = VE/ICsat

= (Vc-VCEsat) /ICsat

= (10V-0.2V)/2mA

RE = 3.4kΩ

(b.) DEMODULATION:

We know that 1/fc < R x C < 1/fm

Take fcmax = 10 kHz

Then 1kHz < RC<100

Implies, 0.1ms< RC< 10ms.

Take R x C = 2.2ms, and let C = 0.22 F

Then R = 10KΩ (pot)

Page 11: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 11 BGSIT, BG Nagar

PROCEDURE:

1. Rig up the circuit as shown in the circuit diagram. 2. Carrier wave and message is given at the input of switching circuit. 3. Observe the PSK output on the CRO. 4. PSK out put is fed as input to the demodulation circuit. 5. Observe the demodulated output on the CRO.

MODEL WAVEFORMS:

Page 12: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 12 BGSIT, BG Nagar

4. DPSK ENCODER AND DECODER

AIM: With the help of suitable circuit demonstrate the working of DSPK encoder & decoder.

EQUIPMENTS:

Experimenter Kit ADCL-01.

0Connecting Cords.

Power supply.

20 MHz Dual Trace Oscilloscope.

BLOCK DIAGRAM:

NOTE: KEEP THE SWITCH FAULTS IN OFF POSITION.

PROCEDURE:

1. Refer to the block diagram and carry out the following connections and switch settings. 2. Connect power supply in proper polarity to the kits ADCL-01 and switch it on. 3. Select Data pattern of simulated data using switch SW1. 4. Connect SDATA generated to DATA IN of the NRZ-L CODER. 5. Connect the NRZ-L DATA out to the DATA IN of the DIFFERENTIAL CNCODER. 6. Connect the clock generated SCLOCK to CLK IN of the DIFFERENTIAL CNCODER. 7. Connect the differentially encoded data to control input C1 of CARRIER MODULATOR. 8. Connect carrier component SIN 1 to IN1 and SIN 2 to IN2 of the Carrier modulator Logic. 9. Connect DPSK modulated signal MOD OUT to MOD IN of the BPSK DEMODULATOR. 10. Connect output of BPSK demodulator b(t) OUT to input of DELAY SECTION b(t) IN and one

output b(t) IN of decision device. 11. Connect the output of delay section b (t-Tb) OUT to the input b (t-Tb) IN of Decision device 12. Compare the DPSK decoded data at DATA OUT with respect to input SDATA. 13. Observe various waveforms as mentioned below fig., if recovered data mismatches with respect

to the transmitter data, then use RESET switch for clear observation of data output.

Page 13: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 13 BGSIT, BG Nagar

MODEL WAVEFORMS:

Page 14: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 14 BGSIT, BG Nagar

Page 15: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 15 BGSIT, BG Nagar

5. QPSK MODULATOR & DEMODULATOR

AIM: With the help of suitable circuit (or modules) demonstrate the working of QPSK modulator &

demodulator.

EQUIPMENTS:

Experimenter kits ADCL-02 & ADCL-03

Connecting Chords

Power supply

20 MHz Dual Trace Oscilloscope

BLOCK DIGRAM:

NOTE: Keep the switch faults in off position.

PROCEDURE:

1. Refer to the block diagram and carry out the following connections and switch settings. 2. Connect power supply in proper polarity to the kits ADCL-02 & ADCL-03 and switch it on. 3. Select Data pattern of simulated data using switch SW1. 4. Connect SDATA generated to DATA IN of the NRZ-L CODER. 5. Connect NRZ-L to DATA IN of the DIBIT CONVERSION. 6. Connect SCLOCK to CLK IN of the DIBIT CONVERSION. 7. Connect the dibit data 1 & Q bit to control input C1 and C2 of CARRIER MODULATIOR

respectively. NOTE: Adjust 1 & Q bit as shown in fig by operating RST Switch on ADCL-2 before connecting it to C1 & C2.

8. Connect carrier component to input of CARRIER MODULATOR as follows: a. SIN 1 to IN1

Page 16: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 16 BGSIT, BG Nagar

b. SIN 2 to IN2

c. SIN 3 to IN3

d. SIN 4 to IN4

9. Connect QPSK modulated signal MOD OUT on ADCL-02 to the MOD IN of the QPSK DEMODULATOR on ADCL-03. NOTE: Adjust recovered 1 & Q bit an ADCL-03 as per ADCL-02 by RST switch on ADCL-03.

10. Connect 1BIT, Q BIT & CLK OUT outputs of QPSK Demodulator to 1 BIT IN, Q BIT & CLK IN posts of Data Decoder respectively.

11. Observe various waveforms as mentioned below fig.

NOTE: If there is mismatch in input & recovered data, than adjust that data by RST switch on ADCL-03.

MODEL WAVEFORMS:

Page 17: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 17 BGSIT, BG Nagar

6. SETTING UP A FIBER OPTIC ANALOG & DIGITAL LINK

(a.) SETTING UP A FIBER OPTIC ANALOG LINK

AIM: To study a 600nm & 950nm fiber analog link and to study the frequency response of the

phototransistor detector

THEORY:

Fiber optic links can be used for transmission of digital as well as analog signals. Basically a fiber

optic link contains three main elements, a transmitter, an optic fiber and a receiver. The transmitter

module takes the input signal in electrical form and then transforms it into optical (light) energy

containing the same information. The optic fiber is the medium which carries this energy. At the

receiver, light is converted back into electrical form with the same pattern as originally fed to the

transmitter.

TRANSMITTER:

Fiber optic transmitters are typically composed of a buffer, driver and an optical source. The

buffer electronics provides both an electrical connection and isolation between the transmitter and the

electrical system supplying the data. The driver electronics provides electrical power to the optical

source in a fashion that duplicates the pattern of data being fed to the transmitter. Finally the optical

source (LED) converts the electrical current to light energy with the same pattern. The LED SFH450V

(950nm) is outside the visible light spectrum. Its optical spectrum is centered at near infrared

wavelength of 950nm.The LED SFH756 (660nm) operates in the visible light spectrum. Its optical light is

centered at wavelength of 660nm.

RECIEVER:

The function of the receiver is to convert the optical energy into electrical form; whish is then

conditioned to reproduce the transmitted electrical signal in its original form. The detector SFH350V

(photo transmitter detector) used in the kit has a transistor type output. The parameters usually

considered in the case of the detector are its responsitivity at peak wavelength and response time.

When optical signal falls on the base of the transmitter detector, proportional current flows through its

emitter, generating the voltage across the resistance between the emitter and ground. This voltage is

the duplicate of the transmitted electrical signal, which can be amplified.

EQUIPMENTS:-

Link-B Kit with power supply

Patch chords

20MHz Dual Channel Oscilloscope

1 MHz Function Generator

1 & 3-Meter Fiber Cable

Page 18: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 18 BGSIT, BG Nagar

BLOCK DIAGRAM:

NOTE: - Keep all switch faults in off position.

PROCEDURE:-

1. Make connection as shown in fig; connect the power supply cables with proper Polarity to Link-B kit. While connecting this, ensure that the power supply is OFF.

2. Keep switch SW8 towards TX position.

3. Keep switch SW9 towards TX1 position.

4. Keep jumper JP5 towards +12V position.

5. Keep jumpers JP6, JP9, JP10 shorted.

6. Keep jumper JP8 towards sine position.

7. Keep intensity control pot P2 towards minimum position.

8. Switch on the power supply.

9. Connect the output post OUT of analog buffer to the post TX IN of transmitter.

10. Slightly unscrew the cap of SFH756V (660nm). Do not remove the cap from the connector. Once the cap is loosened, insert the one meter fiber into the cap. Now tighten the cap by screwing it back.

Page 19: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 19 BGSIT, BG Nagar

12. Connect the other end of the fiber to detector SFH350V (phototransistor detector) very carefully as per the instruction in the above step.

13. Observe the detected signal at post ANALOG OUT on oscilloscope. Adjust intensity control pot P2 optical power control potentiometer so that a signal of 2Vpp amplitude is received.

14. To measure the analog bandwidth of the phototransistor, vary the input signal frequency and observe the detected output signal at various frequencies.

15. Plot the detected signal applied signal frequency and from this plot determine the 3dB down frequency.

16. Repeat the same procedure as above for the second transmitter SFH450V by making the following changes. Analog bandwidth of SFH350 for TX1 SFH756 is about 300 kHz while for TX2 SFH450 its below 300kHz.

17. Keep switch SW9 towards TX2 position.

18. Keep jumper JP7 towards +12V.

MODEL WAVEFORM:

Page 20: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 20 BGSIT, BG Nagar

(b.) SETTING UP A FIBER OPTIC DIGTAL LINK

AIM: To study 600nm & 950nm fiber digital link. Study the transmission of digital signal over fiber optic

cable and the reproduction of the same at the output end.

THEORY: The basic elements of the analog link remain same even for the digital application.

TRANSMITTER: - LED, digital dc coupled transmitters are one of the most popular varieties due to their

ease of fabrication. A standard TTL gate is used to drive a NPN transistor, which modulates the LED

SFH450V or SFH756V source.

RECIEVER: - SFH551V is a digital optodetector. It delivers a digital output, which can be processed

directly with little additional external circuitry. The integrated circuit inside the SFH551V optodetector

comprises the photodiode device, a trans-impedance amplifier, a comparator and a level shifter.

The photodiode converts the detected light into a photocurrent. With an aid of an integrated

lens the light emanating from the plastic fiber is almost entirely focused on the surface of the diode. At

the next stage the trans-impedance amplifier converts the photocurrent into a voltage.

In the comparator, the voltage is compared to a reference voltage. In order to ensure good

synchronism between the reference and the trans-impedance output voltage, the former is derived

from the second circuit of similar kind, which incorporates a ‘blind’ photodiode. The comparator derives

a level shifter with an open collector output stages. Here a catch diode (similar to Schottky-TTL)

prevents the saturation of the output transistor, thus limiting the output voltage to the supply voltage.

EQUIPMENTS:-

Link-B Kit with power supply

Patch chords

20MHz Dual Channel Oscilloscope

1 MHz Function Generator

1 Meter Fiber Cable

Page 21: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 21 BGSIT, BG Nagar

BLOCK DIAGRAM:

NOTE: - Keep all switch faults in off position.

PROCEDURE:-

1. Make connection as shown in fig, connect the power supply cables with proper polarity to Link-B kit. While connecting this, ensure that the power supply is OFF.

2. Switch on the power supply.

3. Feed TTL square wave signal of 1 kHz from the function generator to the IN post of Digital Buffer.

4. Connect the output post OUT of Digital Buffer to the post TX IN of transmitter.

5. Slightly unscrew the cap of SFH756V (660nm). Do not remove the cap from the connector. Once the cap is loosened, insert the 1m fiber into the cap. Now tighten the cap by screwing it back.

6. Connect the other end of the fiber to detector SFH551V very carefully as per the instruction in above step.

7. Observe the detected signal at the post TTL OUT on oscilloscope as shown in fig.

8. To measure the digital bandwidth of the phototransistor vary the input signal frequency and

Page 22: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 22 BGSIT, BG Nagar

observe the detected signal at various frequencies.

9. Determine the frequency at which the detector stops recovering the signal. This determines the maximum bit rate on the digital link.

10. Keep switch SW9 towards TX2 position.

11. Keep jumper JP7 towards +5V position.

12. Repeat the same procedure above for second transmitter SFH4850V by making the following changes.

MODEL WAVEFORM:

Page 23: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 23 BGSIT, BG Nagar

STUDY OF LOSSES IN OPTICAL FIBER

AIM: Conduct a suitable experiment using Fiber Optic trainer kit to determine

(A) Bending loss.

(B) Attenuation loss (propagation loss).

(C) Numerical aperture.

EQUIPMENTS:-

Fiber optic trainer Kit

Optical Fiber Cables(1m & 3m)

Numerical aperture measurement jig

20MHz Dual Channel Oscilloscope

1 MHz Function Generator

Patch chords

THEORY:

Optical Fibers are available in different variety of materials. These materials are usually selected

by taking into account their absorption characteristics for different wavelengths of light. In case of

Optical Fiber, since the signal is transmitted in the form of light, which is completely different in nature

to study the losses in fiber.

Losses are introduced in fiber due to various reasons. As light propagates from one end of Fiber to

another end, part of it is absorbed in the material exhibiting absorption loss. Also part of the light is

reflected back or in some other directions from the impurity particles present in the material

contributing to the loss of the signal at the other end of the Fiber. In general terms it is know as

propagation loss. Plastic Fibers have higher loss of the order of 180dB/Km.

Whenever the condition for angle of incidence of the incident lights is violated the losses are

introduced due to refraction of light. This occurs when fiber is subjected to bending. Lower the radius of

curvature more is the loss. Other losses are due to the coupling of Fiber at LED & photo detector ends.

BLOCK DIAGRAM:

Page 24: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 24 BGSIT, BG Nagar

NOTE: - Keep all switch faults in off position.

PROCEDURE:-

1. Connect the power supply cables with proper polarity to trainer kit. While connecting this, ensure that the power supply is OFF.

2. Keep SW9 towards TX1 position for SFH756 (660nm).

3. Keep jumpers & SW8 position as shown in fig.

4. Keep intensity control pot P2 towards minimum position.

5. Switch ON the power supply.

6. Feed about 2Vpp sinusoidal signal of 1 KHz from the function generator to the Analog Buffer.

7. Connect the output post out of Analog Buffer to the transmitter.

8. Slightly unscrew the cap of SFH756V (660nm). Do not remove the cap from the connector. Once the cap is loosened, insert the 1 Meter Fiber into the cap. Now tighten the cap by screwing it back.

9. Connect the other end of the Fiber to detector SFH 350V (Photo Transistor Detector) very carefully as per the instruction in above step.

10. Observe the detected signal at post Analog out on oscilloscope. Adjust intensity control pot P2 Optical Power control potentiometer so that you receive signal of 2Vpp amplitude.

Measurement of Propagation loss

11. Measure the peak value of the received signal at Analog out terminal. Let this value be V1. 12. Now replace 1 meter Fiber by 3 Meter Fiber between same LED and Detector. Do not disturb and

settings. Again take the peak voltage reading and let it be V2.

Page 25: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 25 BGSIT, BG Nagar

13. If α is the attenuation per km of the Fiber, then we have

αdB= (10/L 1-L2) log 10 (V2/V1)

where

α= dB/Km; L1=Fiber Length for V1; L2=Fiber Length for V2

This α is for peak wavelength of 660nm

14. Now switch off the power supply. 15. Keep SW9 towards TX1 position for SFH756. 16. Set the jumpers to form simple analog link using LED SFH450V at 950nm and phototransistor

SFH350V (Photo Transistor Detector) with 1meter Fiber Cable. 17. Switch on the power supply.

18. Repeat the same procedure as above again for this link to get α at 950nm.

19. Compare the two α values.

MEASUREMENT OF BENDING LOSSES:-

1. Set up the 660nm analog link using 1-meter fiber as per procedure above. 2. Bend the Fiber in a loop. (As shown in fig) measure the amplitude of the received signal. 3. Keep reducing the diameter of bend to about 2 cm & take corresponding out voltage readings.

(Do not reduce loop diameter less than 1 cm). 4. Poly a graph of the received signal amplitude versus the loop diameter. 5. Repeat the procedure again for second transmitter.

MEASUREMENT OF Numerical aperture

1. Set up the 660nm analog link using 1-meter fiber as per procedure above. 2. Insert the other end of the Fiber into the numerical aperture measurement jig. Adjust the fiber

such that its cut face is perpendicular to the axis of the fiber. 3. Keep the distance of about 5mm between the fiber tip and the screen. Gently tighten the screw

and thus fix the fiber in the place. 4. Increase the intensity pot P2 to get bright red light circular patch. 5. Now observe the illuminated circular patch of light on the screen. 6. Measure exactly the distance d and also the vertical and horizontal diameters MR and PN as

indicated in the fig. 7. Mean radius is calculated using the following formula

r = (MR + PN) / 4.

8. Find the numerical aperture of the Fiber using the formula

NA =sinθmax = r/√(d2 + r2)

Where θmax is the maximum angle at which the light incident is properly transmitted through

the given fiber.

Page 26: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 26 BGSIT, BG Nagar

STUDY OF NUMERICAL APERTURE OF OPTICAL FIBER AIM: To measure the numerical aperture of the plastic Fiber provided with the kit using 660nm

wavelength LED.

THEORY: Numerical aperture refers to the maximum angle at the light incident on the fiber end is

totally internally reflected and is transmitted properly along the Fiber. The cone formed by the

rotations of this angle along the axis of the Fiber is the cone of acceptance of the Fiber. The light ray

should strike the fiber end within its cone of acceptance; else it is refracted out of the fiber core.

CONSIDERATION IN A MEASUREMENT:-

1. It is very important that the source should be properly aligned with the cable & the distance from the launched point & the cable be properly selected to ensure that the maximum amount of Optical power is transferred to the cable.

2. This experiment is best performed in a less illuminated room.

EQUIPMENTS:-

Link-B kit with power supply.

Patch chords.

1 Meter Fiber Cable.

Numerical aperture measurement jig.

Steel Ruler.

BLOCK DIAGRAM:

Page 27: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 27 BGSIT, BG Nagar

NOTE: - Keep all switch faults in off position.

PROCEDURE:-

1. Make connections as shown in fig. connect the power supply cables with proper polarity to Link-B kit. While connecting this, ensure that the power supply is off.

2. Keep Intensity control pot P2 towards minimum position. 3. Keep Bias control pot P1 fully clockwise position. 4. Switch on the power supply. 5. Slightly unscrew the cap of SFH756V (660nm). Do not remove the cap from he connector.

Once the cap is loosened, insert the 1 Meter Fiber into the cap. Now tighten the cap by screwing it back.

6. Insert the other end of the Fiber into the numerical aperture measurement jig. Adjust the fiber such that its cut face is perpendicular to the axis of the fiber.

7. Keep the distance of about 5mm between the fiber tip and the screen. Gently tighten the screw and thus fix the fiber in the place.

8. Increase the intensity pot P2 to get bright red light circular patch. 9. Now observe the illuminated circular patch of light on the screen. 10. Measure exactly the distance d and also the vertical and horizontal diameters MR and PN as

indicated in the fig. 11. Mean radius is calculated using the following formula

r= (MR+PN)/ 4.

12. Find the numerical aperture of the Fiber using the formula

NA =sinθmax = r/√d2 + r2

Where θmax is the maximum angle at which the light incident is properly

Transmitted through the giver.

Page 28: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 28 BGSIT, BG Nagar

7. MEASUEMENT OF FREQUENCY, GUIDE WAVELENGTH, POWER, VSWR & ATTENUATION IN A MICROWAVE TEST BENCH

AIM: Measurement of frequency, Guide wavelength, Power, VSWR & Attenuation in a Microwave

test bench

COMPONENTS:

Klystron power supply Klystron tube & mount SMA transmission line Micro-strip 3dB Power Divider Frequency meter VSWR Isolator Variable attenuator Detector CRO

MEASUREMENT OF FREQUENCY GUIDE & WAVE LENGTH

PROCEDURE:-

1. Set up the components and equipments as shown in fig

2. set up variable attenuator at minimum attenuation position

3. keep the control knobs of VSWR Meter as below:

Range - 50 db

Input switch - Crystal low impedance

Meter switch - Normal position

Gain (Coarse & Fine) - Mid position

4. Keep the Control Knobs of Klystron power supply as below

Page 29: Advanced Communication Lab-punithpes@Gmail

Advanced Communication Lab (06ECL-67)

Dept. of ECE 29 BGSIT, BG Nagar

Beam Voltage - OFF

Mod-switch - AM

Beam voltage Knob - Fully anticlockwise

Reflector Voltage - Fully clockwise

AM-Amplitude Knob - Around fully clockwise

AM-Frequency Knob - Around mid position.

5. Switch ‘ON’ the Klystron power supply, VSWR Meter.

6. Switch ‘ON’ the beam voltage switch and set beam voltage at 250v with help of beam voltage knob.

7. Adjust the reflector voltage to get some deflection in VSWR Meter.

8. Maximize the deflection with AM amplitude and frequency control knob of power supply.

9. Tune the plunger of Klystron Mount for maximum deflection.

10. Tune the reflector voltage knob for minimum deflection.

11. Tune the probe for maximum deflection in VSWR Meter.

12. Tune the frequency meter knob to get a ‘dip’ on the VSWR Scale and note down the frequency directly from frequency meter.

13. Replace the rumination with movable short, and detune the frequency meter.

14. Move the probe along the slotted line. The deflection in VSWR meter will vary. Move the probe to be a minimum deflection position, to get accurate reading. If necessary increase the VSWR meter range db switch to higher position. Note and record the probe position.

15. Move the probe to next minimum position and record the probe position again.

16. Calculate the guide wavelength as twice the distance between two successive minimum position obtained as above.

17. Measure the waveguide inner broad dimension ‘a’ which will be around 22.86 mm for X-band.

18. Calculate the frequency by following equation.

ii) Measurement of wavelength, frequency & VSWR:

Slotted –line carriage position

(M)

Distance between successive

minima

Distance between successive

maxima

M1=

m2=

D1=M1-M3=

d1=m2-m4=

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M3=

m4=

M5=

m6=

M7=

m8=

M9=

D2=M3-M5=

D3=M5-M7

D4=M7-M9

d2=m4-m6=

d3=m6-m8=

*m –maxima position M—minima postion

OBSERVATIONS & CALCULATIONS:

Operating frequency f (using frequency meter) =

Dav = (D1 + D2 + D3 + --------+ Dn) / n = ________

dav = (d1 + d2 + d3 + --------+ dn) / n = __________

Guide wavelength (λg) =2[(Dav + dav) / 2]

Cut-off wavelength (λC) = (2 a) / m = ____________

Where a = broader dimension of waveguide and m = 1 for TE10 mode

1/(λO)2 = 1/(λC)2 + 1/(λg)

2

λO = free-space wavelength = ______________

Operating frequency f = C/ λO = __________________

VSWR = Vmax /Vmin

MEASUREMENT OF VSWR AND POWER:-

The Input to the VSWR meter is the detected signal output of the microwave detector of the output of the amplifier is measured with a square – law calibrated voltmeter which directly gives the VSWR reading Vmax/Vmin for an input of Vmin, after the meter is adjusted to unity VSWR for an Input corresponding to Vmax.

1. Move the probe along the slotted line to get maximum deflection in VSWR Meter.

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2. Adjust VSWR meter gain control knob or variable attenuator until the meter indicates 1.0 on normal VSWR Scale.

3. Keep the entire control knob as it is, move the probe to next minimum position. Read the VSWR on scale and power in dB.

4. Repeat the above step for change of S.S.tuner Probe depth and record the corresponding SWR.

5. If the VSWR is between 3.2 and 10, change the range dB switch to next higher position and read the VSWR on second VSWR scale of 3 to 10.

MEASUREMENT OF ATTENUATION:

1. Move the probe along the slotted line to get maximum deflection in VSWR Meter.

2. Adjust VSWR meter gain control knob or variable attenuator until the meter indicates 1.0 on normal VSWR Scale.

3. Vary the attenuator Knob till we get the deflection in VSWR Meter and note down the value in dB. This gives the attenuation.

VSWR (Voltage standing wave Ratio) Meter:-

A VSWR meter is a sensitive high gain, high Q, low noise voltage amplifier tuned normally at a fixed frequency of 1 KHz at which the microwave signal is modulated.

The Input to the VSWR meter is the detected signal output of the microwave detector of the output of the amplifier is measured with a square – law calibrated voltmeter which directly gives the VSWR reading Vmax/Vmin for an input of Vmin, after the meter is adjusted to unity VSWR for an Input corresponding to Vmax.

A gain control can be used to adjust the reading to the desired value. The over all gain is nearly 125db which can be altered in step of 10db.

There are three scales on the VSWR meter,

When the VSWR is between 1 & 4, reading can be taken from the top SWR Normal scale.

For VSWR between 3.2 & 10, bottom of SWR NORMAL scale is used.

When the VSWR is less than 1.3, a more accurate reading can be taken by selecting the expanded scale, graduated from 1 to 1.2.

The third scale at the bottom is graduated in dB.

Slotted line carriage

Slotted line carriage cantinas a co-axial E-field probe which penetrates inside a rectangular wave guide slotted section or a co-axial slotted line section from the outer wall & is able to traverse a longitudinal narrow slot.

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The longitudinal slot is cut along the centre of the waveguides broad wall or alone the outer conductor of the co-axial line over a length of 2-3 wave lengths were the electric current on the wall does not have any transverse component.

The slot should be narrow enough to avoid any distortion in the original field inside the waveguide.

The two ends of the slot is tapered to zero width for reducing the effect of discontinuity. The probe is made at move longitudinally at a constant small depth to achieve a uniform coupling Co-efficient between the electric field inside the line of the probe current at all positions. The probe samples the electric field which is proportional to the probe voltage. This unit is primarily used for the determination of locations of the voltage sending wave maximum & minimum along the line.

The probe carriage contains a stub tunable Co-axial probe detector to obtain a low frequency modulating signal output to a slope or VSWR meter.

The probe should be very thin compared to the wave length & the depth also should be small enough to avoid any field distortion.

The slotted line with tunable probe detector is used to measure.

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8. TDM AND RECOVERY OF TWO BAND LIMITED SIGNALS OF PAM SIGNALS

AIM: To design and demonstrate the working of TDM and recovery of two band-limited Signal of

PAM signals.

COMPNENTS REQUIRED:

Transistor SL100, SK100

Op-amp μA 741

Resistors 1KΩ, 1.5KΩ.

CIRCUIT DIAGRAM:

DEMODULATION:

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THEORY:-

TDM is a technique used for transmitting several message signals over a communication channel by dividing the time frame into slots, one slot for each message signal. This is a digital technique in which the circuit is highly modular in nature and provides reliable and efficient operation. There is no cross talk in TDM due to circuit non-linearities since the pulses are completely isolated. But ot also has its disadvantages, which include timing jitter and synchronization is required.

In pulse- amplitude modulation, the amplitude of a periodic train of pulses is varied in proportion to a message signal. TDM provides and effective method for sharing a communication channel.

PROCEDURE:-

1. Rig up the circuit as shown in the circuit diagram for multiplexer.

2. Feed the input message signals m1 and m2 of 2V (P-P) at 200Hz.

3. Feed the high frequency carrier signal of 2V (P-P) at 2kHz.

4. Observe the multiplexed output.

5. Rig up the Demodulator circuit as shown in the circuit diagram for Demultiplexer.

6. Observe the Demultiplexer output in the CRO.

RESULT:-

TDM circuit using PAM signals (both multiplexer and Demultiplexer) has been designed and demonstrated.

WAVEFORM:

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MODULATION WAVEFORM

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DEMODULATION WAVEFORM

WAVEFORMS:

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9. PCM GENERATION & DETECTION USING CODEC CHIP

AIM: Demonstration of PCM Generation & Detection using CODEC Chip

COMPNENTS REQUIRED:

IC 7493 2nos, IC 44233 1no.

Resistors 1KΩ 1no, 560Ω 1no.

CIRCUIT DIAGRAM:

PROCEDURE:

1. Connections are made as per circuit diagram. 2. D.C. Power supplies are switched on and applied the specified voltages. 3. A TLL, clock of 2MHz is applied to the counter IC 7493 at pin number 14 and observe the

output using on oscilloscope at pin number 11 the should be 125kHz (divided by 16 of 2MHz).

4. Check the output at pin number 11 of the 2nd IC7493, which will be approximately 8 kHz (divided by 16 of 2MHz).

5. Apply a sinusoidal message frequency of 1 kHz 1v at pin no 1 of IC44233. 6. Observe the PCM output at pin number 8 of IC44233. You may have to change the time

range of oscilloscope to convenient range to observe the frame time (50 μs range) and the 8-bit word length (0.5 μs range).

7. Observe the demodulated output at pin number 5 of IC44233 and compare it with original analog message.

8. Observe the changes at the PCM output and demodulated output by changing the frequency and amplitude of the message sign

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WAVEFORMS:

RESULT:

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10. MEASUREMENT OF POWER DIVISION AND ISOLATION CHARACTERISTICS OF

MICROSTRIP 3dB POWER DIVIDER

AIM:- To measure the power divider and isolation characteristics of Micro-strip 3dB power divider.

COMPONENTS:

Klystron power supply Klystron tube & mount SMA transmission line Micro-strip 3dB Power Divider Frequency meter VSWR Isolator Variable attenuator Detector CRO

CIRCUIT DIAGRAM:

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PROCEDURE:-

1. Set up the system as shown in figure with transmission line in place of power divider coupler.

2. Switch ‘ON’ the Klystron power supply with ideal initial conditions.

3. Keep the VSWR in 30dB range and the current supply for the Klystron around 0.013A and adjust AM knobs to get a 0dB on the VSWR meter in the power scale.

4. Connect the power divider block between the transmission and detection block of the test bench.

5. Measure the outputs at different output port with other output port with 50Ω matched terminator.

6. Measure the isolation by terminating the input port and giving input to the one of output port and measure the power at other port.

7. Note down all the observed values.

RESULT: with VSWR meter

Isolation (dB) =P3-P2

Power division arm 3(dB)= P1-P3

Power division arm 2(dB)= P1-P2

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11. DETERMINATION OF COUPLING AND ISOLATION CHARACTERISTICS OF

MICROSTRIP DIRECTIONAL COUPLER

AIM: To determine of coupling and isolation characteristics of Micro-strip directional coupler.

COMPONENTS:

Klystron power supply Klystron tube & mount SMA transmission line Micro-strip Directional Coupler Frequency meter VSWR Isolator Variable attenuator Detector CRO

CIRCUIT DIAGRAM:

PROCEDURE:-

1. Set up the system as shown in figure with transmission line in place of coupler.

2. Switch ‘ON’ the Klystron power supply with ideal initial conditions.

3. Keep the VSWR in 30dB range and the current supply for the Klystron around 0.013A and adjust AM knobs to get a 0dB on the VSWR meter in the power scale1.

4. Replace the 50Ω transmission line with branch line coupler (port 1 input side).

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5. Check outputs at port 2 (through output), port 3 (isolated output), port 4(Coupled output).

6. Calculate the insertion loss, coupling formulae given below.

7. Observe the output on CRO and calculate the factors with given formulae.

RESULT:-

Operating frequency =

Transmission loss =

Isolation factor =

Coupling factor =

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12. MEASUREMENT OF RESONANCE CHARACTERISTRICS OF A MICROSTRIP RING

RESONATOR

AIM:- To measure the resonance characteristics of a Micro-strip ring resonator & output.

COMPONENTS:

Klystron power supply Klystron tube & mount SMA transmission line Micro-strip Ring Resonator Frequency meter VSWR Isolator Variable attenuator Detector CRO

CIRCUIT DIAGRAM:

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TABULAR COLUMN:

VOLTAGE (V) FREQUENCY (GHz)

PROCEDURE:-

1. Set up the system as shown in figure with transmission line in place of resonator.

2. Switch ‘ON’ the Klystron power supply with ideal initial conditions.

3. Keep the VSWR in 30dB range and the current supply for the Klystron around 0.013A and adjust

AM knobs to get a 0dB on the VSWR meter in the power scale1

4. Replace the connector(transmission line) with a Ring resonator.

5. Vary the frequency knob of the Klystron source and note down the VSWR meter reading.

6. Plot the graph of the power (voltage)various the frequency.

RESULT: A plot the frequency various power is drawn and the resonant frequency is found out.

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13. MEASURMENT OF THE DIRECTIVITY AND GAIN OF DIFFERENT ANTENNAS

AIM: To measure the Directivity and gain of antenna standard dipole, Micro-strip patch antenna & Yagi antenna.

COMPONENTS:

Klystron power supply Klystron tube & mount SMA transmission line Micro-strip Ring Resonator Frequency meter VSWR Isolator Variable attenuator Detector CRO

CIRCUIT DIAGRAM:

PROCEDURE:-

1. Set up the system as shown in figure with transmission line in place of antannas.

2. Keep the Klystron at ideal initial conditions and switch it ON.

3. Keep the VSWR in 30dB range and the current supply for the Klystron around 0.013A and adjust

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AM knobs to get a 0dB on the VSWR meter in the power scale1

4. Connect the antenna setup between the transmission and detector..

5. calculate resonant frequency and distance using S=2L2/λ and keep the transmitter and receiving antennas at this distance. L- broader dimension of antenna.

6. Keeping the line of sight properly (00 at turn table), tabulate the output. 7. Rotate the turn table in clock wise and anti clock wise for different angle of deflection and

tabulate the output for every angle (EØ). 8. Plot a graph Angle v/s output.

9. Find the half power beam width (HPBW) from the points where the power becomes half (3dB points or 0.707V points).

10. Directivity is calculated as:

2)(

41253

HPBWD in degress.

11. Gain in calculated using:

Et

ErS

Pt

SG

4Pr4

Gain in dB = 10 log G

RESULT:

HPBW=

BWFN=

Gain=

Directivity=