Advanced commu nication lab manual

7/30/2019 Advanced commu nication lab manual

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DEPT. OF

E&C

ENGINEERING

ADVANCED COMMUNICATION LAB MANUAL

FOR THE ACADEMIC YEAR:2011-2012

Canara Engineering College

Ben ana adavu, Man alore-574219

Ajay BolarDigitally signed by Ajay BolarDN:cn=Ajay Bolar,o=Canara EngineeringCollege,ou=Dept.ofElectronics and CommunicationEngineering,[email protected],c=INDate:2011.12.1400:14:36+05'30'


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Advanced Communication Lab Manual-2012

Dept. of E&C, Canara Engineering College, Mangalore.

CONTENTS

Sl.

No.

Experiments Page

1

2

3

4

5

6

7

8

9

10

11

12

Time Division Multiplexing and Demultiplexing

Amplitude Shift Keying Modulation and Demodulation

Frequency shift keying Modulation and Demodulation

Phase Shift Keying Modulation and Demodulation

Differential Phase Shift Keying Modulation and Demodulation

Quadrature Phase Shift Keying Modulation and Demodulation

Reflex klystron mode study

Study of Propagation loss, Bending loss and Measurement of NumericalAperture in OFC

Microstrip Directional Couplers

Microstrp ring resonator and power Devider

Study Of Dipole Antenna Radiation Pattern(Simple,Folded Dipole

antenna)

To find the Gain and Directivity of Yagi-Uda Antenna

1

3

8

12

15

18

23

27

32

34

37

40


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Advanced Communication Lab Manual -2012

Dept. of E&C, Canara Engineering College, Mangalore. Page 1

Expt No-1. TIME DMSION MULTIPLEXING (TDM)

To design and demonstrate the working of TDM and recovery of two band limited

signals of PAM signals.

AIM:

Transistors-SL-lOO, SK-lOO, Resistors- 1 k, 1.5 k, OpAmp A 741.

Components Required:

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 it also has its disadvantages, which

include timing jitter and synchronization is required.

THEORY:

In pulse-amplitude modulation, the amplitude of a periodic train of pulses is varied in pro-

portion to a message signal. TDM provides an effective method for sharing a communication

channel.

CIRCUIT DIAGRAM:


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Expected Waveforms:

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

2. Feed the input message signals ml and m2 of 2 volts P-P at 200 Hz.3. Feed the high frequency carrier signal of 2V (P-P) at 2 kHz.4. Observe the multiplexed output.5. Rig up the circuit for demultiplexer.6. Observe the demultiplexed output in the CRO.

RESULTS:

CONCLUSION:


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Expt No-2. AMPLITUDE SHIFT KEY MODULATION AND

DEMODULATION

To design and verify the operation of ASK generator and demodulator.

AIM:

Transistor SLlOO,Resistors-4.7 k, 20 k (pot), 10 k (pot), OpAmp ].1A741, Diode-

By127.

Components Required

THEORY:

CIRCUIT DIAGRAM:


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EXPERIMENTAL PROCEDURE:

1. Rig-up the modulator circuit as show in the figure.

Procedure

2. Set the message signal of amplitude 10 V(P-P) and frequency 500 Hz.

3. Set the carrier signal of amplitude 2 V(P-P) and frequency 2 kHz.

4. Observe the ASK waveform at the collector of transistor.

5. Now connect the demodulation circuit.

6. Observe the demodulated output on the CRO.

Procedure for ASK Kit

A 4052 multiplexer is used as an ASK modulator. This is 2 to 1 multiplexer. For one input

carrier is applied directly and for the second input the carrier is given by resistive attenuator

of 2:1 ratio Data signal is given to select line of 2:1 mux.

ASK MODULATOR:

A detector and a low pass filter with a cutoff frequency of 3.4 kHz is used to demodulate the

ASK signal. The output of lowpass filter is given to a opamp comparator. The output of

comparator is original data transmitted.

ASK DEMODULATOR:

Built in 12V & 5V at 350mA.Fixed DC power supplies are provided.

POWER SUPPLIES:

A 8038 IC Based sine wave generator is provided as a carrier generator of frequency 7kHz to

100kHz variable.

CARRIER SIGNAL GENERATOR:


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The Bit clock generator is designed using timer 555 which is operated in astable mode. The

frequency of clock is chosen from 150Hz to 13kHz.

BIT CLOCK GENERATOR:

The 8 bit parallel to serial shift IC 74165 is used to generate the required word pattern. A set

of DIP switches are used to set 1 and 0 pattern. The last stage output Q& is coupled to the

first stage input Do in the shift register. The 8 bit data set by the switches and loaded with

the register parallel is now shifted

8 BIT WORD GENERATOR:

1. Connect the AC Adaptor to the mains and the other side to the experimental trainer.EXPERIMENTAL PROCEDURE:

2. Observe the Bit Clock frequency on the Oscilloscope. Adjust the frequency to 10 KHzand connect it to Pin No. 2 of 74165 IC.

3. Set the SPDP switches pattern to the desired code (say 0000 1111).4. Parallel load by changing the switch to opposite side to shift side for a short duration

and get back to shift position.

5. Observe the 8 Bit word pattern at the output of the 8 Bit word generator. This is theactual modulating signal.

6. Adjust the carrier frequency of 100 KHz and 5 Volt p-p, give this input to the ASKmodulator inputs using a patch chord.

7. Connect the 8 Bit word generators output to the data input terminal of the ASKModulator.

8. Observe the data input on one channel on a CRO and ASK output on the secondchannel.

9. To get demodulated signal, connect the ASK modulator output to demodulator input.10. Adjust the two knobs simultaneously to get the original digital message at the

demodulator output on a CRO.


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CIRCUIT DIAGRAM:

TABULAR COLUMN:

amplitude &

frequency ofdata sent

Modulating

signalamplitude &

frequency

Modulated

signalamplitude &

frequency

Demodulated

signal amplitude &frequency

1.

2.

3


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EXPECTED WAVEFORMS:

RESULTS:

CONCLUSION:


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Expt No-3. FREQUENCY SHIFT KEYING MODULATION &

DEMODULATION

AIM:

To design and verify the operation of FSK generator and detector.

Components Required:

Transistor-SLlOO, SKIOO, Resistors, Capacitors.

THEORY:

FSK is one of the digital modulation technique. Here frequency of the carrier is switched

between two values. A sinusoidal of amplitude' A' and frequencyfc1is used to represent a

binary '1' and frequencyfc2is used to represent binary '0'. FSK modulated waveform can be

represented as,


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CIRCUIT DIAGRAM:


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

2. Apply carrier of amplitude 2 V(P- P) and frequency 1 kHz.

3. Apply carrier of amplitude 2 V(P- P) and frequency 2 kHz.

4. Apply message signal of amplitude 10 V(P - P) and frequency of 250 Hz. .

5. Observe ASK outputs at each collector of transistor, and also observe FSK output

at pin 6 of op-amp.

6. Connect demodulator circuit.

7. Observe the demodulated output on CRO.


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PROCEDURE for FSK kit:

1. Connect the AC Adaptor to the mains and the other side to the Experimental Trainer.2. Apply any one Data output of the Decade Counter (7490 IC) to the Data input point of

the FSK Modulator and observe the Same Signal in one Channel of a Dual TraceOscilloscope.

3. Observe the output of the FSK Modulator on the second channel of the CRO.4. During the Demodulation, Connect the FSK output to the input of the Demodulator.5. Adjust the Potentiometers P1 and P2 until we get the Demodulated output equivalent

to the Modulating Data Signal.

CIRCUIT DIAGRAM:


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TABULAR COLUMN:

amplitude &

frequency of

data sent

Modulating

signal

amplitude &

frequency

Modulated

signal

amplitude &

frequency

Demodulated signal

amplitude & frequency

1.

2.

3

EXPECTED WAVEFORMS:

RESULTS

CONCLUSION


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Advanced Communication Lab Manual


Expt No-4. PHASE SHIFT KEYING MODULATION & DEMODULATION

AIM:

To Study the operation of PHASE SHIFT KEY modulation and demodulation with help of Demonstration

board

THEORY:

Fig shows the circuit diagram of the Phase Shift Key modulation and demodulation. In this carrier

Generator is generated by a weinbridge oscillator around 28KHz. At 5Vp-p sine wave using 741 IC. The

sine wave is converted into square wave using TL084 in comparator mode. The transistor BC 107 converts

the square wave signal to TTL level. This is used as a basic bit clock or 180 for a mark and 0 for space.

This square wave is used as a clock input to a decade counter (IC7490) which generates the modulatingdata outputs. IC CD4051 is an Analog multiplexer to which carrier is applied with and without 180 phase

shift to the two multiplex inputs of the IC. Modulating data input is applied to its control input. Depending

upon the level of the control signal, carrier signal applied with or without phase shift is steered to the

output. The 180 phase shift to the carrier signal created by an operational amplifier using 741 IC during the

demodulation, the PSK signal is converted into a +5 volts square wave signal using a transistor and is

applied to one input of an EX-OR gate. To the second input of the gate, carrier signal is applied after

conversion into a +5 volts signal. So the EX-OR gate output is equivalent to the modulating data signal.


1. Switch ON the experimental board.2. Apply the carrier signal to the input of the modulator3. Apply the modulating data signal to the modulator input and observe this signal on channel 1 of the CRO4. Observe the output of the PSK modulator on the channel 2 of the CRO5. Apply this PSK output to the demodulator input and also apply the carrier input.6. Observe the Demodulator output and compare it with the modulating data signal applied to the

modulator input which is identical.


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CIRCUIT DIAGRAM:

TABULAR COLUMN:

amplitude &

frequency of

data sent

Modulating

signal

amplitude &

frequency

Modulated

signal

amplitude &

frequency

Demodulated signal


1.

2.

3


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EXPECTED WAVEFORMS:

RESULTS

CONCLUSION:


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EXPT NO-5. DIFFERENTIAL PHASE SHIFT KEYING

AIM:

To Study the various steps involved in generating the Differential binary Signal and Differential Phase Shift

Keyed Signal at the modulator end and recovering the binary signal from the received DPSK Signal.

THEORY:

The carrier wave signal is generated by a weinbridge oscillator around ***KHZ at 5V P-P sine wave

using 741 the sine wave is convert into square wave using TL084 in comparator mode. The Transistor BC

107 converts the square signal to TTL levels. This is used as a basic bit clock or 180 for a mark and 0 for

space. This Square wave is used as a clock input to a decade counter(IC 7490) which generates the

modulating data outputs.

The modulation is performed as follows:

The Differential signal to the modulating is generated using an Exclusive-OR gate(7486) and a 1-bit delay

circuit using D flipFlop 7474 CD 4051 is an analog multiplexer to which carrier is applied with and

without 180degrees Phase shift(created by using an operational amplifier connected in inverting amplifier

mode) to the input of the TL084.Differential signal generated by Ex-OR gate (IC 7486) is given to the

multiplexers control signal input. Depending upon the level of the control signal, carrier signal applied

with or without phase shift is steered to the output. 1-bit delay generation of differential signal to the input

is created by using a D-flip-flop(IC 7474).

The demodulation is performed as follows:

During the demodulation, the data and carrier are recovered through a TL084 op amp in comparator mode.

This level is brought to TTL level using a transistor and is applied to one input of an EX-OR gate. To the

second input of the gate, carrier signal is applied after conversion into a +5V signal. So the EX-OR gate

output is equivalent to the differential signal of the modulating data. This differential data is applied to one

input of an Exclusive-OR gate and to the second input, after 1-bit delay the same signal is given. So the

output of this EX-OR gate is the recovered modulating signal.


1. Switch ON the experimental board.2. Check the carrier Signal and the data generator signals initially.3. Apply the carrier signal to the carrier input of the DPSK modulator and give the data generated tothe data input of DPSK modulator and Bit clock output to Bit clock input of modulator. Observe the DPSK

modulating output with respect to the input data generator signal of dual trace Oscilloscope (Observe the


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DPSK modulating signal on channel 1 and the data generator signal on channel 2), and observe the DPSK

signal with respective to Differential data also.

4. Give the output of the DPSK modulator signal to the input of demodulator, give the Bit clock outputto the Bit clock input to the demodulator and also give the carrier output to the carrier input of demodulator.

5. Observe the demodulator output with respect to data generator signal ( Modulating Signal)CIRCUIT DIAGRAM:

TABULAR COLUMN:


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amplitude &

frequency of

data sent

Modulating

signal

amplitude &

frequency

Modulated

signal

amplitude &

frequency

Demodulated signal


1.

2.

3

EXPECTED WAVEFORMS:

RESULTS:

CONCLUSION:


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EXPT NO-6. Quadrature Phase Shift Keying (QPSK)

AIM:

To Study the Quadrature Phase Shift Keying.

Equipments:

Kit CT-13, Patch cards, Power supply and two-channel oscilloscope.

THEORY:

Digital Phase Modulation (or Phase Shift Keying - PSK) is very similar to Frequency Modulation. It

involves changing the phase of the transmitted waveform instead of the frequency, these finite phase

changes representing digital data. In its simplest form, a phase-modulated waveform can be generated by

using the digital data to switch between two signals of equal frequency but opposing phase.

Taking the above concept of PSK one stage further, it can be supposed that the number of phase shifts is not

limited to only two states. The transmitted "carrier" can undergo any number of phase changes and by

multiplying the received signal by a sine wave of equal frequency will demodulate the phase shifts into

frequency independent voltage levels. This is, indeed the case in QPSK (Quadrature Phase Shift Keying,

Sometimes this is known as quaternary PSK, quadriphase PSK, 4-PSK). With QPSK, the carrier undergoes

four changes in 4 phases and can thus represent two bits of binary data. While this may seem insignificant

at first glance, a modulation scheme has now been supposed that enables a carrier to transmit two bits of

information instead of one, thus effectively doubling the bandwidth of carrier. QPSK has four phases and fora given bit-rate, the QPSK requires half the bandwidth of PSK and is widely used for this reason.

BLOCK DIAGRAM:


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CIRCUIT DIAGRAM:


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Use CT-13 board.1. Connect the power supply cable at the POWER IN connector and switch ON the power.2. Connect the QPSK-TX to QPSK-RX.3. Give the input through Dip switch S1 and observe the phase shift at QPSK-TX, compare the

waveform with fig.

4. EX: Through the Dip switch select the bits as 11100100 (The switch is upper side=O, the switch islower side= 1)

5. Change the bit pattern by using the Dipswitch and observe the corresponding changes atSLDATA-TX.

6. Demodulated output can be observed at SLDATA-RX at this point you will get the same pattern asthat at SLDATA-TX and you can see the same at the 8-LEDs.

7. Ex: If your selected bit pattern is 11100100 then at the demodulation side LED D3, D4, D5 &D8Should be ON and D6, 07, 09 & 010 should be OFF,

8. Note the delay between, SLDATA-TX and SLDATA-RX, There is 0.2 In sec delay. This is due tothe delay between LT6/5-6(ISIG-QSIG)and U6/ I(SH/LD). Here first data is shifting and after 0.2 m sec

the data is loading. Refer the following Fig:

9. If the LED's are not stable at the demodulator side then adjust the POT-P I(IPCK).10.After power on if you are getting the wrong display (LED) at demodulator side then press SWI once

you will get the same pattern as you set at the modulator side.


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EXPECTED WAVEFORMS:


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RESULTS:

CONCLUSION:


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EXPT NO-7. KLYSTRON MODE STUDY

AIM:

1. Plot 2 or 3 modes of the given Klystron tube2. Obtain its Electronic Tuning Range (ETR)3. Obtain its Electronic Tuning Sensitivity (ETS)4. Demonstrate the mode on a CRO

Experimental Setup:

Block Diagram:

THEORY:

The reflex klystron makes use of velocity modulation to transform a continues electron beam into

microwave power. Electrons emitted from the cathode are accelerated and passed through the positive

resonator towards negative reflector, which retards and finally, reflects the electrons and the electrons turn

back through the resonator, suppose an rf field exist between the resonators the electrons traveling forward

will be accelerated electrons leave the resonator at an the voltage at the Resonator changes in amplitude.

The accelerated electrons leave the resonator at an increased velocity and the retarded electrons leave at the

reduced velocity. The electrons leaving the resonator will need different time to return, due to change in

velocities. As a result, returning electrons group together in bunches. As the bunches pass through

resonator, they interact with voltage at resonator grids. If the bunches pass the grid at such a time that the

K P S

Klystron

Mount

2K25

Isolator Variable

Attenuator

Frequency

Meter

Detector

Mount

CRO


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electrons are slowed down by the voltage then energy will be delivered to the resonator and Klystron will

oscillate.

The dimensions of resonant cavity primarily determine the frequency. Hence, by changing the volume of

resonator, mechanical tuning of Klystron is possible. Also a small frequency change can be obtained by

adjusting the reflector voltage. This is called Electronic Tuning.

For further details refer Microwave Devices and Circuits by Samuel Y. Liao

Important: Firing the Reflex Klystron


1. Set the cooling fan to be blow air across the tube. Set Beam voltage control knob fullyanticlockwise (Off), Repeller voltage to

3/4 clockwise. Set modulation selector switch to AM-

MOD position. Keep AM-MOD amplitude knob and AM-FREQUENCY knob at mid-position.

Volt/Current switch of the display to current position. Set display to read Beam voltage.

2. Wait for some 10 seconds; let the tube warm up and power supply get properly stabilized.3. Slowly vary the beam voltage knob clockwise and set beam current to 19 or 20mA. The

corresponding beam voltage would be around +290v.

4. Observe the demodulated square wave available at the detector o/p using a CRO. By adjusting theAM-MOD amplitude knob and the Reflector (repeller) voltage knob at a maximum o/p level on

the CRO.

During switch off power failure, bring down the beam current to 0 and follow steps 1&2 in the

reverse order.

Demonstrate the mode on a CRO:

K P S Klystron power supply.

1. Set up the equipment as shown in the fig. Keep the position of the variable attenuator at theminimum attenuation position.

2. Set the mode selector to FM-MOD position. Keep the beam voltage knob fully anticlockwise & thereflector voltage knob fully clockwise.

3. Keep the time/division scale of the oscilloscope around 100Hz. Switch on the klystron powersupply.

4. Adjust the beam voltage position around 290Volts.5. By changing the reflector voltage & amplitude of the FM modulation any mode of the klystron can

be seen on the oscilloscope.

Plot o/p signal voltage v/s repeller voltage. The same can be obtained by plotting the o/p power v/s repellervoltage.


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I Mode:

Repeller Voltage (V) Output Signal amplitude p-p Frequency in GHz

60

476.7

II Mode:

Repeller Voltage (V) Output Signal amplitude p-p Frequency in GHz

95

89

99

Modes of klystron


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Calculations:

1. Mode Number: Knowing mode top voltage of two adjacent modes, mode number of the modesmay be computed as given below.

( )

4

3

4

31

2

1

1

2

+

++

== n

n

VV

NN

2. ETR(Electronic Tuning Range): Electronic Tuning Range for a particular mode is the totalchange in frequency from one end of the mode to the other.

( )minmaxff =

3. ETS(Electronic Tuning Sensitivity):

ETS= 12

12

oo vv

ff

Where f1 & f2 are half power (3db) frequencies and Vo2 and Vo1 are repeller voltages corresponding to 3db

points.

RESULTS:

CONCLUSION:


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Expt no-8a. STUDY OF PROPOGATION LOSS, IN OPTIACAL FIBER

OBJECTIVE:

The objective of this experiment is to measure propagation or attenuation loss in optical fiber.

Block Diagram:

THEORY: Attenuation is loss of power. During transit light pulse lose of their photons, thus reducing their

amplitude. Attenuation for a fiber is usually specified in decibels per kilometer. For commercially available

fibers attenuation ranges from 1dB/km for premium small-core glass fibers to over 2000dB/km for a large

core plastic fiber. Loss is by definition negative decibels. In common usage, discussions of loss omit the

negative sign. The basic measurement for loss in a fiber is made by taking the logarithmic ratio of the input

power (Pi) to the output power (Po)

o

i

P

PdB 10log10)( =

Where is Loss in dB/Meter


1. Connect power supply to board2. Make the following connections (as shown in Diagram 7)a) Function Generators 1Khz sinewave output to input 1 socket of emitter 1 circuit via 4mm lead.

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

c) Connect Detector 1 output to amplifier 1 input Socket via 4mm lead.

3. Switch ON the power supply.4. Set the Oscilloscope channel 1 to 0.5V/Div and adjust 4-6 div amplitude by using X1 probe withthe help of variable pot in function generator block at input 1 of Emitter 1.

5. Observe the output signal from detector t p 28 on CRO.6. Adjust the amplitude of the received signal as that of transmitted one with the help of gain adjustpot in AC Amplifier block. Note this amplitude and name it V1.

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


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8. Measure the amplitude at the receiver side again at output of amplifier 1 socket t p 28. Note thisvalue end name it V2.

Calculate the propagation (Attenuation) loss with the help of following formula.

)21( LL +

V1/V2 = e

Where is loss in nepers/meter

1 neper = 8.686 dB ,L1 = Length of shorter cable (0.5m), L2 = Length of longer cable (1m)


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8b. STUDY OF BENDING LOSS

OBJECTIVE:

The Objective of this experiment in to study of bending loss.

THEORY:

Whenever the condition for angle of incidence of the incident light 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.


1.

Repeat all the steps from 1 to 6 of the previous experiment No 7 using 1m cable.2. Wind the FO cable on the mandrel and observe the corresponding AC amplifier output onCRO it will be gradually reducing showing loss due to bends.

TABULAR COLUMN:

No of bends Output signal voltage in

volts

Without bending

1st

bend

2nd

bend

3rd

bend


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8c. MEASUREMENT OF NUMERICAL APERTURE

OBJECTIVE:

The Objective of this experiment is to measure to the Numerical Aperture (NA) of the Fiber.

THEORY:

Numerical aperture refers to the maximum angle at which the light incident on the fiber end is totally

internally reflected and is transmitted properly along the fiber. The cone formed by the rotation 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.

Consideration in NA measurement:It is very important that the optical source should be properly aligned with the cable and the distance from

the launched point & cable be properly selected to ensure that the maximum amount of optical power is

transferred to the cable.

Equipments:

1. Numerical Aperture measurement Jig.


1. Connect power supply to the board.2. Connect the frequency generators 1 KHz sine wave output to input of emitter 1 circuit. Adjustits amplitude at 5V p-p.

3. Connect one end of fiber cable to the output socket of emitter 1 circuit and the other end to theNumerical aperture measurement jig. Hold the white screen facing the fiber such that its cut face is

perpendicular to the axis of the fiber.

4. Hold the white screen with 4 concentric circles (10, 15, 20 & 25mm diameter) vertically at asuitable distance to make the red spot from the fiber coincide with 10mm circle.


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5. Record the distance of screen from the fiber end L and note the diameter W of the spot.6. Compute the numerical aperture from the formula given below,

224

..WL

WAN+

=

maxsin=

7. Vary the distance between in screen and fiber optic cable and make it coincide with one of theconcentric circles. Note its distance.

8. Tabulate the various distances and diameter of the circles made on the white screen and computethe numerical aperture from the formula given above.

TABULAR COLUMN:

Distance of the

screen L in meters

Diameter W of the

spot in meters

Numerical Aperture

(NA)

RESULTS:

CONCLUSION:


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Expt No-9. MICROSTRIP DIRECTIONAL COUPLER

AIM:

To determine coupling and isolating characteristic of Microstrip Directional Coupler.

COMPONENTS USED:

10dB directional coupler

Branch line directional coupler (3dB)

Parallel line directional coupler (15dB)

VSWR meter

Microwave source.

THEORY:

Directional coupler is four port waveguide junction consisting of 2 primary waveguide1-2 and secondary

waveguide 3-4. When all ports are terminated in either characteristic impedance, there is free transmission

of power without reflection between port1 and port2 and there is no transmission of power between port1

and port3 or between 2 & 4. Because no coupling exists between these two pairs of ports. These are 3

directional coupler 3dB directional coupler, 10dB and 15dB branch line directional coupler.


1. Experiment set up as shown in fig 1.2. Keep microwave source in internal AM mode.3. Tabulate the direct power at frequencies 2.2GHz to 3GHz in steps of 0.1 GHz and note down

output power from VSWR meter.

4. Now experiment is setup as shown in figure 2.5. Keep microwave source in Internal AM mode.6. Apply RF signal to input port and vary the frequencies from 2.2GHz to 3GHz in steps of 0.1GHz

and note down coupling power in VSWR meter.

7. Terminate isolation port & direct port by 50 standard frequencies.8. Repeat these steps to find the output power at direct port and isolating port.9. Terminate unused ports by 50 .10.Experiment is conducted for -3dB,-10dB,-15dB directional coupler.


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Block Diagram:

RF-OUT

Fig.1

RF-OUT

Fig. 2

Direct Power & Coupling proof Power for -3dB Directional Coupler

RF Signal Direct Frequency Coupling Power Direct Power Isolator proof

Power

2.2GHz

3GHz

RESULTS:

CONCLUSION:

MicrowaveSource

Diode Detector VSWR Meter

Microwave

Source

Directional

Coupler

Diode Detector VSWR Meter


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EXPT N0-10. MICROSTRIP RING RESONATOR AND POWER DEVIDER

AIM:

1. To measure resonance characteristics of Microstrip Ring Resonator and determine dielectricconstant of the substrate.

2. To measure power division and isolation characteristics of microstrip 3dB power divider.

THEORY:

The open-end effect encountered in a rectangular resonator of the feed long gaps can be minimized by

forming the resonator as a closed off. Such resonator is called as Ring resonator.

The Ring resonator find applications in the design of filters, oscillator and mixers.Resonance is established when the mean circumference of the ring is equal to integral multiplies of guide

wave length.

eff

o

fo

nvnro

==2

Where ro = radius of the ring, n = mode number, eff= effective dielectric constant of the substrate.

Power Divider:

The function of a power division network is to divide the input power into two or more outputs. As an equal

split power divider, the power incident at port1 gets divided equally between the two output

ports 2 & 3.

Power at 2 & 3 is half power. i.e.-3dB down power.

EXPERIMENTAL SET UP/BLOCKDIAGRAM:

RF OUT

Fig.1

Microwave

Source

Ring

Resonator

Diode

Detector

VSWR

Meter

CRO


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1. Experiment set up as shown in fig.12. Keep microwave generator in Internal AM mode.3. Vary the RF out frequencies at 2.2GHz to 3GHz insteps of 0.1GHz and note down output detector

power in VSWR meter.

4. Note down/ tabulate these results & note down the resonant frequency at which the output powermaximum.

5. Plot the graph output power Vs frequency.6. Determine dielectric constant of the substrate of Ring Resonator.

Power divider Characteristics:

1. Experiment set up as shown in fig.22. Apply RF power to input port and observe the half power at 2 output port.E.g. If input power is -20dB, Output power is -23dB at each output port.

Calculations:

Dielectric constant of substrate

A

Aeffr

11

112

+

=

WhereW

hA

101+= area of

W= Stripline conductor width = 1.847mm

h = Height of substrate = 0.762mm

2

2

=

oo

o

efffr

nv

= Effective Dielectric constant

n = 1, smvo /1038

= , mmro 446.12= radius of the ring

=of Resonance frequency


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EXPECTED GRAPH:

Table

Rf signal f (Ghz) Output power(Db)

2.1Ghz

3Ghz

RESULTS

CONCLUSION


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EXPT N0-11. Study Of Antenna Radiation Patterns(Simple, Folded Dipole)

AIM:

To determine Antenna Radiation pattern, Beam width and Front To back Ratio of Simple dipole and Folded

dipole antennas.

EXPERIMENTAL SET UP

THEORY:

Antennas can be broadly classified by the directions in which they radiate or receive electromagnetic

radiation. They can be isotropic,omnidirectional or directional. An Isotropic antenna is a hypothetical

antenna that radiates uniformly in all directions so that the electric field at any point on a sphere has the

same magnitude. Such radiation cannot be realized in practice since in order to radiate uniformly in all

directions an isotropic antenna would have to be a point source.

A directional antenna radiates most of its power in one particular direction examples of directional antennas

are Yagi UDA, log-Periodic and helical.

EXPERIMENTAL PROCEDURE

Experiment A

1) Arrange the setup as shown in figure.2) Mount simple dipole (/2) on the transmission mask.3) Bring the detector assembling near to main unit and adjust height of both transmitting and receiving

antenna same.

4) Keep detector away from main unit approximately 1.5 meter and align both of them.5) Keep the RF level and FS adjust to minimum level and directional coupler switch to FWD.6) Keep detector level control in the center approximately.7) Increase the RF level gradually and see there is a deflection the detector meter.


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8) Adjust RF level and detector level so that deflection in detector meter is approximately 30-35A.9) Align arrow mark on the disk with zero of the gonio meter scale.10) Start taking the reading at the interval of 5 or 10degre.11)Convert micro ampere reading into dB, with the help of conversion chart.12)Plot the polar graph in degrees of rotation of antenna against level in the detector in dBs.13)From the graph calculate: a) beam width

b) front/back ratio

c) gain of antenna

14) to calculate these from the graph proceed as follows.

Beam width:

1. Look for main lobe2. Draw bore sight maxima line AA3. Mark -3dB from maximum on the bore sight line point B4. Draw an arc of radius AB5. This arc will intersect main lobe at CD6. Measure angle CAD. This angle is -3Db beam width.

Front to Back Ratio

1. Look for main lobe2. Draw bore sight maxima line AA3. Look for back lobe if any (at 180deg)4. If no back lobe then front to back ratio =AA/1 dB5. If there is back lobe then measure AE, where E is the maxima of back lobe then6. front to back ratio = AA/AE dB

GAIN OF ANTENNA = Maximum radiation intensity

= AA/1 dB

Experiment B

Replace /2 antenna with /4 antenna and follow the steps given in Experiment A.

TABLE

ANGLE IN DEGREES GAIN IN dB

0

20

40

.

.

.

360.


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Simple dipole radiation Pattern

Folded Dipole radiation Pattern

RESULTS

CONCLUSION


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EXPT N0-12. Measurement of directivity and gain of antennas: Standard dipole (orprinted dipole), microstrip patch antenna and Yagi antenna (printed).

Aim:

To find the directivity and gain of Antennas.

Apparatus required :

1. Microwave Generator2. SWR Meter3. Detector4. RF Amplifier5. Transmitter and receiving mast6. Mains cord7. Antennas

o Yagi Antenna (Dielectric Constant : 4.7) - 2 no.o Dipole Antenna (Dielectric Constant : 4.7) - 1 no.o Patch Antenna (Dielectric Constant : 3.02) - 1 no.

Theory :

If a transmission line propagating energy is left open at one end, there will be radiation from this end. The

Radiation pattern of an antenna is a diagram of field strength or more often the power intensity as a function

of the aspect angle at a constant distance from the radiating antenna. An antenna pattern is of course three

dimensional but for practical reasons it is normally presented as a two dimensional pattern in one or several

planes. An antenna pattern consists of several lobes, the main lobe, side lobes and the back lobe. The major

power is concentrated in the main lobe and it is required to keep the power in the side lobes arid back lobe as

low as possible. The power intensity at the maximum of the main lobe compared to the power intensity

achieved from an imaginary omni-directional antenna (radiating equally in all directions) with the same

power fed to the antenna is defined as gain of the antenna.

As we know that the 3dB beamwidth is the angle between the two points on a main lobe where the power

intensity is half the maximum power intensity.

When measuring an antenna pattern, it is normally most interesting to plot the pattern far from the antenna.

It is also very important to avoid disturbing reflection. Antenna measurements are normally made at

anechoic chambers made of absorbing materials.

Antenna measurements are mostly made with unknown antenna as receiver. There are several methods tomeasure the gain of antenna. One method is to compare the unknown antenna with a standard gain antenna


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with known gain. Another method is to use two identical antennas, as transmitter and other as receiver. From

following formula the gain can be calculated.

Where, Pt is transmitted power

Pr is received Power,

G1, G2 is gain of transmitting and receiving antenna

S is the radial distance between two antennas

o is free space wave length.

If both, transmitting and receiving antenna are identical having gain G then above equation becomes.

In the above equation Pt, Pr and S and o can be measured and gain can be computed. As is evident from the

above equation, it is not necessary to know the absolute value of Pt and Pr only ratio is required which can be

measured by SWR meter.

Setup for Directivity measurement


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Procedure :

Directivity Measurement:

1. Connect a mains cord to the Microwave Generator and SWR Meter.2. Now connect a Yagi antenna in horizontal plane to the transmitter mast and connect it to the RF

Output of microwave generator using a cable (SMA to SMA).

3. Set both the potentiometer (Mod Freq & RF Level) at fully clockwise position.4. Now take another Yagi antenna and RF Amplifier from the given suitcase.5. Connect the input terminal of the Amplifier to the antenna in horizontal plane using an SMA (male)

to SMA (female) L Connector.

6. Now connect the output of the Amplifier to the input of Detector and mount the detector at theReceiving mast.

7. Connect one end of the cable (BNC to BNC) to the bottom side of receiving mast, and another end tothe input of SWR meter.

8. Now set the distance between Transmitter (feed point) and the receiver (receiving point) at halfmeter.

Yagi Antenna

Antenna Under Test

RF Amplifier

Detector

Transmitter

Receiver

SWR Meter

Microwave Generator


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9. Now set the receiving antenna at zero degree (in line of Transmitter) and Switch on the power supplyfor Microwave Generator, SWR Meter. Also connect DC Adapter of RF Amplifier to the mains.

10.Select the transmitter for internal AM mode and press the switch RF On.

11.Select the range switch at SWR meter at 40dB position with normal mode.12.Set both the gain potentiometers (Coarse & Fine) at fully clockwise position and input select switch

should be at 200 Ohm position. In case if reading is not available at 40dB range then press 200

kOhm (Input Select) to get high gains reading.

13.Now set any value of received gain at 40dB position with the help of -o Frequency of the Microwave Generator.o

Modulation frequency adjustment .o Adjusting the distance between Transmitter and Receiver.

14.With these adjustments you can increase or decrease the gain.15.Mark the obtained reading on the radiation pattern plot at zero degree position.16.Now slowly move the receiver antenna in the steps of 10 degree and plot the corresponding readings.17.This will give the radiation pattern of the antenna under test.18.Directivity of the antenna is the measures of power density an actual antenna radiates in the direction

of its strongest emission, so if the maximum power of antenna (in dB) is received at degree thendirectivity will be ....................dB at ........................Degree.

19.In the same way you can measure the directivity of the Dipole antenna.20.For directivity measurement of the transformer fed Patch antenna connect transmitter Yagi antenna

in the vertical plane (Patch Antenna is vertically polarized). Since it is comparatively low gain

antenna distance can be reduced between transmitter and receiver.

Gain Measurement :

1. Connect a power cable to the Microwave Generator and SWR Meter.2. Now connect a Yagi antenna in horizontal plane to the transmitter mast and connect it to the RF

Output of microwave generator using a cable (SMA to SMA).

3. Set both the potentiometer (Mod Freq & RF Level) at fully clockwise position.4. Now take another Yagi antenna from the given suitcase.5. Connect this antenna to the detector with the help of SMA (male) to SMA (female) L Connector.6. Connect detector to the receiving mast.7. Connect one end of the cable (BNC to BNC) to the bottom side of receiving mast, and another end to

the input of SWR meter.


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8. Now set the distance between Transmitter (feed point) and the receiver (receiving point) at halfmeter.

9. Now set the receiving antenna at zero degree (in line of Transmitter) and Switch on the power fromboth Generator & SWR Meter.

10.Select the transmitter for internal AM mode and press the switch RF On.11.Select the range switch at SWR meter at 40dB position with normal mode.12.Set both the gain potentiometers (Coarse & Fine) at fully clockwise position and input select switch

should be at 200 Ohm position. In case if reading is not available at 40dB range then press 200

kOhm (Input Select) to get high gain reading.

13.Now set the maximum gain in the meter with the help of following -o Frequency of the Microwave Generator.o Modulation frequency adjustment .o Adjusting the distance between Transmitter and Receiver.

14.Measure and record the received power in dB.Pr = ..................dB

15.Now remove the detector from the receiving end and also remove the transmitting Yagi antenna fromRF output.

16.Now connect the RF output directly to detector without disturbing any setting of the transmitter(SMA-F to SMA-F connector can be used for this).

17.Observe the output of detector on SWR meter that will be the transmitting power Pt.

Pt = ..................dB

18.Calculate the difference in dB between the power measured in step 14 and 17 which will be thepower ratio Pt/Pr .

Pt/Pr = ........................

Pr/Pt = ........................

19.Now we know that the formula for Gain of the antenna is:


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Where :

Pt is transmitted power

Pr is received Power,

Gis gain of transmitting/receiving antenna (since we have used two identical antennas)

S is the radial distance between two antennas

o is free space wave length (approximately 12.5cm).

20.Now put the measured values in the above formula and measure the gain of the antenna which willbe same for both the antennas. Now after this step you can connect one known gain antenna at

transmitter end and the antenna under test at receiver end, to measure the gain of the antennas.

21.Gain can be measured with the help of absolute power meter also (Recommended Model NV105).for this detector will not be used and directly the power sensor can be connected to both the ends as

described earlier.

Radiation Patterns of Different Antennas:

00

10

20

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-44-48-52-56-6000

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Yagi Antenna Patch Antenna

Dipole Antenna


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TABLE

ANGLE IN DEGREES GAIN IN dB

0

20

40

.

.

.

360

RESULTS

CONCLUSION

Advanced commu nication lab manual

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Transcript of Advanced commu nication lab manual