AIET_AC_Lab

ALVA’S INSTITUTE OF

ENGINEERING & TECHNOLOGY

Department of Electronics & Communication

Engineering ADVANCED COMMUNICATION LAB MANUAL

Subject Code: 06ECL – 67

Prepared by: Mahesh Prasanna K.

Approved by: Head of the Department

Name: ………………….………………………………….………..

USN: …………………………….. Batch: ...…………..…..

DEPARTMENT OF ELECTRONICS AND COMMUNICATIONS ENGINEERING

ADVANCED COMMUNICATION LAB MANUAL

Alva’s Institute of Engineering & Technology, Moodbidri.

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INDEX

Page No.

1. ASK GENERATION AND DETECTION 04

2. FSK GENERATION AND DETECTION 07

3. BPSK GENERATION AND DETECTION 11

4. TDM OF TWO BAND LIMITED SIGNALS 14

5. DIFFERENTIAL PHASE SHIFT KEYING (DPSK) 17

6. QUADRATURE PHASE SHIFT KEYING 19

7. PCM GENERATION AND DETECTION 21

8. MICROWAVE TEST BENCH 23

9. TIME DIVISION MULTIPLEXING USING OPTIC FIBRE 25

10. OPTICAL FIBRE 28

11. MICRO STRIP RING RESONATOR 33

12. COUPLIG AND ISOLATION CHARACTERISTICS 36

13. POWER DIVISION AND ISOLATION 38

14. DIRECTIVITY AND GAIN OF ANTENNA 40

15. VIVA-VOCE 42

16. QUESTION BANK 47

*********




4

EXPERIMENT N0-1: ASK GENERATION & DETECTION

AIM: Design & Demonstrate an ASK system to transmit digital data using a suitable carrier.

Demodulate the signal with suitable circuit.

CIRCUIT DIAGRAM: ASK GENERATION

DESIGN:

Assume Icsat = 5mA , hfe(min) = 30 , VCEsat = 0.2V , VBE = 0.7V

IB = IC / hfe =____mA

RE = VE / IE = (VC - VCEsat) / Ic =____ Ω

RB= (Vm - VBE - VE) / IB =____Ω




5

CIRCUIT DIAGRAM: DETECTION

Envelope Detector

DESIGN:

1/fc < RC < 1/fm

Let C = 0.47μf

=____Ω

PROCEDURE:

1. Connections are made as shown in circuit diagram

2. Provide message signal m(t) and carrier signal c(t) using signal generator

3. Observe the ASK signal at the Emitter and note down the readings (Voltage and time

period)

4. Connect the detection circuit as shown and supply the ASK signal

5. Vary Vref carefully and observe the detected signal, note down its voltage level and time

period.




6




7

EXPERIMENT N0-2: FSK GENERATION AND DETECTION

AIM: Design & Demonstrate an FSK system to transmit digital data using a suitable carrier.

Demodulate the signal with suitable circuit.

CIRCUIT DIAGRAM: GENERATION

DESIGN: Detection

I. Inverting Amp: c1'(t) = - ( ) c1(t) let |gain|=1 so Rf=R1(say 1kΩ)

II. Adder: v(t) = - ( )[fsk + c1'(t)] let |gain| =1 so Rf=R1(say 1kΩ)

III. Envelope detector : 1/fc < RC < 1/fm

Let C = 0.47μf then =____Ω use 10k pot.




8

Inverter Adder Envelope detector

PROCEDURE:


2. Provide message signal m(t) and carrier signals C1(t) and c2(t)using signal generator

3. Observe the FSK signal at the pin 3 of IC CD4051 and note down the readings

(voltage and time period)

4. Connect the detection circuit as shown and supply the FSK signal and C1(t)

5. Vary Vref carefully, observe the intermediate ASK signal and finally observe

detected signal, note down its voltage level and time period.

CALCULATIONS:

Frequency Deviation, δf = f2 – f1

Modulation Index, β = δf/fm




9




10




11

EXPERIMENT N0-3: BPSK GENERATION AND DETECTION

AIM: Design & Demonstrate a BPSK system to transmit digital data using a suitable carrier.

Demodulate the above signal with suitable circuit.

CIRCUIT DIAGRAM: GENERATION

DESIGN:

Inverting Amp: c'(t) = - ( ) c (t) let |gain|=1 so RF=R1 (say 1kΩ)

DESIGN: DETECTION

I. Adder: v(t) = - ( )[fsk + c1'(t)] let |gain| =1 so Rf=R1(say 1kΩ)

II. Envelope detector : 1/fc < RC < 1/fm

Let C = 0.47μf =____Ω use 10k pot.




12

DETECTION:

Adder Envelope detector

PROCEDURE:


2. Provide message signal m(t) and carrier signal c(t) using signal generator

3. Observe the BPSK signal at the pin 3 of IC CD4051 and note down the readings

(voltage and time period)

4. Connect the detection circuit as shown and supply the BPSK signal and c(t)

5. Vary Vref carefully, observe the intermediate ASK signal and finally observe

detected signal, note down its voltage level and time period.




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14

EXPERIMENT N0-4: TDM OF 2 BAND LIMITED SIGNALS

AIM: To study the TDM of 2 band limited PAM signals.

CIRCUIT DIAGRAM: GENERATION OF PAM SIGNALS

DESIGN:

Assume Icsat = 10mA, hfe(min) = 20 , VBE = 0.7V

Let VRE = 1V

IBmin > ICsat / hfe(min) = 0.01/20 = 0.5mA

RB = (Vin - VBE - VRE) / IB min= (5 - 0.7 - 1) /0.5 m = 6.6kΩ (use 10kΩ)

RE = VRE / IE = (VRE / IC) = 1/10m = 100Ω (use 1kΩ)




15

GENERATION OF TDM SIGNALS:

PROCEDURE:


2. Provide message signals m1(t) and m2(t) and carrier signal c(t) using signal generator

(keep f c > 2fm )

3. Observe the PAM signals at transistor emitter terminals as shown in circuit diagram

4. Now apply these PAM signals as input to multiplexer CD4051

5. Observe the TDM signal at pin 3 of IC and note down the readings




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17

EXPERIMENT N0-5: DIFFERENTIAL PHASE SHIFT KEYING (DPSK)

AIM: To design and demonstrate the working of DPSK to transmit a given digital data and to

demodulate the DPSK signal to recover the digital data.

COMPONENTS REQUIRED: DPSK kit, patch cords, CRO.

DPSK TRANSMITTER:

DPSK RECEIVER:

CALCULATIONS: dk = bk + dk-1




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PROCEDURE:

1. Select either 300 bps or 600 bps clock.

2. Connect the power supply to the kit.

3. Switch off the power. Connect the probe to the CRO.

4. Connect measuring probe of the CRO to SEL CLK.

5. Using patch cords given connect the clock and data.

6. Connect the CRO probe to SEL CLK.

7. Adjust the DIP switch to any digital pattern of 8 bits.

8. Observe the DPSK waveform on the CRO.

9. Plot the graph for given Input sequence

10. At the receiver section, observe the reconstructed data.

Input Seq, bk 1 1 0 1 0 0 0 1 Input Seq, bk 1 1 0 1 0 0 0 1

dk-1 (Assume, 0) 1 0 0 1 1 1 1 0 dk-1 ( Assume, 1 ) 0 1 1 0 0 0 0 1

DPSKencoded

data, dk

1 0 0 1 1 1 1 0 DPSK

encoded

data, dk

0 1 1 0 0 0 0 1

Transmitted

phase

0 π

π 0 0 0 0 π Transmitted

phase

π 0 0 π π π π 0




19

EXPERIMENT N0-6: QUADRATURE PHASE SHIFT KEYING (QPSK)

AIM: To design and demonstrate the working of QPSK to transmit a given digital data and

demodulate to recover the digital data.

COMPONENTS REQUIRED: QPSK kit, patch cords, CRO

QPSK TRANSMITTER:

Product

modulator

90o phase shifter

Inverter

Carrier

Product modulator

Inverter

Filter

QPSK

wave

Binary

Input data

Q channel

Sin wct

-Cos wct

-Sin wct

Cos wct

Q I

I channel




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QPSK RECEIVER:

PROCEDURE:

1. Connect the dotted lines by patch cords.

2. Connect the power cord to power supply.

3. Adjust the DIP switch to any digital pattern of 8 bits.

4. Observe the QPSK modulated signal for specified data.

5. Observe the demodulated output by suitably adjusting the potentiometer.

6. Plot the QPSK waveforms

Product modulator

90o phase shifter

Carrier

Product modulator

BPF

LPF

LPF

Comparator

Comparator

Bit combiner Binary

data

Modula

ted

output




21

EXPERIMENT N0-7: PCM GENERATION AND DETECTION

AIM: To study the performance of a given codec chip in implementing the generation and

detection of PCM wave.

CIRCUIT DIAGRAM:

5

7 11

4

14 9 1

3 12

2 3 10

1

2 3

10

14 7 16

11

12 4 15

1 4

2 8

2 3

3 3

4 5

13

9 10

5

14 7

4 11

9

1 3

12

2 3 10

1

2 3

10

5v -5v

÷16

÷

256

m (t),1Khz/2v

5

6

0

Ώ

1

K

Ώ

m’ (t)

TTL clock

2Mhz/5v

PCM

O/P




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COMPONENTS REQUIRED: IC44233, IC7493, Resistor, Function generator 2MHz TTL

Clock, Power supply, CRO

PROCEDURE:

1. Connect the circuit as per the circuit diagram.

2. Apply TTL clock of 2MHz from function generator to pin 14 of IC 7493 and

sine wave of 1 KHz / 2v from function generator to pin1 of IC 44233.

3. Check the output at pin 11 of first IC7493. That should be 125 KHz i.e.2MHz / 16.

4. Check the output at pin 11 of second IC7493. That should be approximately

8 KHz i.e.2MHz / 256.

5. Observe the PCM output at pin 8 of IC44233.

6. Observe the demodulated output at pin 5 of IC44233 and compare with original

analog message.




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EXPERIMENT N0-8: MICROWAVE TEST BENCH

AIM: Conduct an experiment to find frequency, guide wavelength, power, VSWR and

attenuation in a microwave test bench.

BLOCK DIAGRAM: MICROWAVE TEST BENCH

PROCEDURE:

1. Initial set up has to be made before switching ON the power supply

2. The conditions are :

a. Repeller – maximum position

b. Beam – minimum position

c. Select switch – voltage

d. Modulation – AM

3. Power supply – OFF

4. Switch on the supply and make sure that fan is towards the source

5. Switch on the klystron source and put the switch to Current position and wait till the

current stabilize to 0.008.

6. Increase the beam voltage knob to 0.018

7. Again the select switch is put to Repeller (-272)

8. Reduce the repeller(-200) until maximum output is obtained on CRO

Klystron

power supply Source Isolator

Variable

Attenuator

Cavity meter or

Frequency meter

Isolator section Detector CRO

Load or short




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9. Note down the maximum and minimum values of the output wave produced for

any one cycle.

10. Take d1min for first cycle and d2min for next consecutive cycle. Calculate λg and λ0.

11. Vary the carriage from load to source and find dmin for two cycles.

12. Measure the cross-section of waveguide i.e. ‘a’ to find λ0.

13. For detection part, remove the load and connect the waveguide and measure the output

voltage v2.

14. Vary the frequency meter till a dip is obtained in the output voltage. Measure the

frequency and calculate attenuation and power.

FORMULAE USED:

1. VSWR=Vmax/Vmin

2. d1min=MSD+(CVSD*LC) Where LC is the least count =0.01

3. d2min=MSD+(CVSD*LC)

4. λg=2(d1min~d2min)

5. λc=2xa where ‘a’ is the cross-section of the waveguide

6. λ0=(λgλc)/(√(λg2+λc

2))

7. f0=C/λ0

8. Attenuation=20log((v2-v1)/2)

9. Power=20log(v2/2)

Vmin

Vmax

Demodulated output @ dip




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EXPERIMENT No-9: TIME DIVISION MULTIPLEXING USING OPTIC FIBRE

AIM: To study the simultaneous transmission of several signals using time division

multiplexing.

COMPONENTS REQUIRED: Optic Fibre kit, CRO

PROCEDURE:

1. Set the marker1 and marker2 each for the bit pattern shown. Observe the time division

multiplexed data at tp10 on CRO

2. Observe and measure the frame period. Change marker setting and observe

the Multiplexed data.

3. Observe both the markers are alternately transmitted in each frame.

4. Observe the data transmission by pressing keys (k1-k8).

WAVEFORMS:

125μS

Ch

1

Ch2 ch3 ch4 ch5 ch6 ch7 ch8 ch9

Ch10 Ch11

Audio1:ch12

Ch13

Audio2:ch14

Ch15 ch16

Marker




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sw1

sw2

Marker

M

U

X

Timing and

sync

Line

coding

Audio1

Audio2

Expansion

channels

K1 -o o-

K2 -o o-

K3 -o o-

K4 -o o-

K5 -o o-

K6 -o o-

K7 -o o-

K8 -o o-

D

E

M

U

X

Audio1

Audio2

Expansion

channels

D1

D2

D3

D4

D5

D6

D7

D8

Timing

and sync

Line

decoding

Marker

D

R

I

V

E

R

MS1

MS2

MS1

MS2

Fibre optic

transmitter

Fibre optic

receiver

Optic Fibre

OPTICAL FIBRE KIT




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FORMULAE:

1. 1 slot time=1 frame/16 channels

2. 1 bit interval=1 slot time/8

3. bit rate=1/bit interval

CALCULATIONS:

frame period=

tp1=Tx clk=

tp2=slot clk=

tp3=frame clk=




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EXPERIMENT No-10: OPTICAL FIBRE

AIM: To conduct an experiment to find:

i) propagation loss

ii) bending loss

iii) numerical aperture of a given optical fibre

EQUIPMENTS REQUIRED: Experiment kit, 20 Mhz dual channel oscilloscope, Function

generator, 1 and 3 meter fibre cable.

PROCEDURE:

To find Propagation loss:

1. Take 1 meter fibre and set up an analog link using LED SPH756v (660 nm) and

detector SFH350v (detector).

2. Apply about 2v (p-p), 1 KHz sinusoidal signal to EXT-ANALOG terminal with

the help of connecting wires provided with the kit.

3. Observe the received signal at ANALOG OUT terminal.Adjust the received

signal properly by adjusting pot pr10 to get 2v (p-p amplitude.

4. Measure the peak value of the received signal at ANALOG OUT terminal this

value be v1.

5. Now replace 1m fibre by 3m fibre between same LED and detector. Do not

disturb pr10 settings.

TABULARCOLUMN:

Calculate propagation loss: P1/P2=V1/V2=exp (-α (L1+L2))

Where α= propagation loss in nepers/m

L1 V1 L2 V2

1m 3m




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Measurement of bending loss:

1. Set up 660nm analog link using 1m fibre.

2. Apply about 2v (p-p) sinusoidal signal of 2 KHz at the EXT-ANALOG terminal.

3. Observe the received signal at ANALOG OUT terminal. Adjust the input amplitude

so that the received signal is not saturated.

4. Bend the fibre in a loop. Measure the amplitude of the received signal.

5. Keep measuring the diameter from 4 to 2 cm and take corresponding output

voltage readings.

6. Plot a graph of the received signal amplitude versus the loop diameter.

Measurement of bending loss:

SL

No

Loop diameter (Cm) Voltage (V)




30

D

R

I

V

E

R

D

R

I

V

E

R

D

E

T

E

C

T

O

R

OPTIC FIBRE KIT

JP17

JP16 JP15

Intensity

JP13

JP12

External analog

Preamplifier

2

KHz

2V

Analog

Out Fibre cable

Fibre Optic

Transmitter1

Fibre Optic

Transmitter2

Fibre Optic Receiver




31

m

p o

n

r

Optical fibre cable

Screw

Screen

Illuminated circular

patch

Emitter of Q32N2907

Cathode of SFH756v

Collector of Q1 2H3904

Cathode of SFH450v

+5V

SFH756v

ANODE

+9V

NUMERICAL APERTURE MEASUREMENT SET UP




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EQUIPMENTS for measuring numerical aperture: Equipment kit, 1m fibre cable, numerical

aperture measurement jig, riler.

PROCEDURE:

1. Set up the 660nm analog link using 1m fibre.

2. Apply TTL high input to the LED from EXT-TTL terminal.

3. Insert the other end of the fibre into the numerical aperture measurement jig.

4. Hold the white sheet facing the fibre. Adjust the fibre such that it’s cut

face is perpendicular to the axis of the fibre.

5. Keep a distance of about 5mm between the fibre tip and the screen. Gently tighten

the screw and thus fix the fibre in the place.

6 Now observe the illuminated circular patch of light on the screen.

7. Measure exactly the distance d and also the vertical and horizontal diameters MR

and PN as indicated in the figure.

8. Mean radius is calculated using the following formula, r = (MR+PN)/4

9. Find the numerical aperture of the fibre using the formula

NA= (sinθmax ) = r/ (√d2+r2)

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

through the fibre.

RESULT:

1. the propagation loss α=

2. numerical aperture =

3. Launching angle θmax = Sin-1

(NA)




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EXPERIMENT No-11: MICRO STRIP RING RESONATOR

AIM: Measurement of resonance characteristics and dielectric constant of a substrate using a

micro strip ring resonator.

PROCEDURE: a.) Resonant Frequency

1) Connect output of receiver (down converter) to RF input through the cable.

2) Connect input of source (up converter) to RF output through the cable.

3) Connect input of receiver (down converter) to output of source (up converter) through

20dB+20dB attenuators.

4) Note down the power in dB at 1500MHz frequency from the receiver (it should be –0.37dBm

at 1500MHz).

5) Connections are shown in figure1.

b.) Ring Resonator



8) Connect input of receiver (down converter) to output port of ring resonator through the cable.

9) Connect output of source (up converter) to input port of ring resonator through 20dB+20dB

attenuators.

10) Note down the readings of frequency Vs power in dBm in steps of 5MHz, 10MHz

& 100MHz.

11) Connections are shown in figure2.

Resonant Frequency: The Frequency corresponding to maximum power is called Resonant

Frequency Fr = 1400MHz at –59.9dBm




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35

Tabular column

CALCULATION of Dielectric constant:

Dielectric constant, εr = [(free space wavelength)/ (circumference of ring resonator)] ^2

The free space wavelength is 214mm at 1400Hz

Free space wavelength λ = (v/f) =3x10^8m/s/1400x10^6 = 214mm.

Circumference of ring resonator: C = π X D = π x 36.5 = 114.6mm

Where D= (inner diameter + outer diameter)/2

D = (33+40)/2 = 36.5mm

SL

No

Ferquency

MHz

Power

dBm




36

EXPERIMENT 12: COUPLING AND ISOLATION CHARACTERISTICS OF

DIRECTIONAL COUPLER

AIM: Determination of coupling and isolation characteristics of a strip line (or micro strip line)

directional coupler.

PROCEDURE:

1. Connect input of receiver (down converter) to coupled 3 port of directional coupler

through 20 dB attenuation.

2. Connect O/P of source (up converter) to IN1 port of directional coupler through

20dB attenuator.

3. Terminate with 50ohm load to out 2 port and isolator ports of directional coupler.

4. Note down the power reading in receiver at 1500MHz it should be equal to -55dBm.

Coupling factor= -55dBm-(-37dBm) = -17dBm

Actual value= 15dB

PROCEDURE: Isolation Measurement:

1. Connect input of receiver (down converter) to isolated port of directional coupler

through 20dB attenuation.

2. Connect output of source (up converter) to IN1 port of directional coupler.

3. Terminate with 50ohm load to out2 and coupled ports of directional coupler.

4. Note down the power reading in receiver at 1500MHz it should be –62.8dB.

-62.8-(-37) = -24.2dBm

Actual value = -20dB




37

RESULT:

a) The coupling factor is –17dB.

b) Isolation is found out to be –24.2dB.




38

EXPERIMENT No-13: POWER DIVISION AND ISOLATION CHARACTERISTICS

AIM: Measurement of power division and isolation characteristics of a micro strip 3dB power

divider.

POCEDURE: Power Division

1. Connect input of receiver (down converter) to a out 3 port of power divider through

20dB attenuator.

2. Connect output of source (up converter) to IN1 port of power divider through

20dB attenuator.

3. Terminator with 50ohm load to out 2 port of power divider.

4. The receiver reading will be equal to –41.4dBm i.e -41.4-(-37) = -4.4dBm

5. Actual value= -3dB

6. Connect input of receiver (down converter) to out 2 port of power divider through

20dB attenuator.

7. Connect output of source (up converter) to IN1 port of divider through 20dB attenuator.

8. Terminator with 50ohm load to out 3 port of power divider.

9. The receiver reading will be –41.5dBm at 1500MHz frequency i.e -41.5-(-37) = - 4.5dBm

Actual value = -3dBm




39

PROCEDURE: Isolation

1. Connect input of receiver (down converter) to out 3 port of power divider through

20dB attenuator.

2. Connect output of source (up converter) to out2 port of power divider through

20dB attenuator.

3. Terminate with 50ohm load to INT port of power divider.

4. The receiver reading will be –56.6 dBm at 1500 MHz frequency

i.e -56.6-(-37) = -19.6dBm

Actual value> 10dB




40

EXPERIMENT No-14: DIRECTIVITY AND GAIN OF AN ANTENNA

AIM: Measurement of directivity and gain of an antenna: Standard dipole

(or Printed dipole), Microstrip patch antenna and Yagi antenna (Printed).

PROCEDURE:



3) Connect input of source (up converter) to transmitter of antenna through 20dB attenuator.

4) Connect the input of receiver (down convrter) to the receiver antenna through 20dB attenuator

5) Keep the transmitter n receiver of antenna at a distance of 1 to 1.5 meters apart and make sure

its inline.

6) Vary the angle of the transmitter starting from 0 degrees in steps of 10degrees up to 180.

7) Note down the value of gain in dBm for every 10 degrees.

8) Calculate the directivity with the gain values noted.

9) Follow the same procedure for both antennas.

CALCULATIONS:

Directivity, D = 41000

0 / ӨH X ӨE

dBi = 10 log D

Gain= KdBi where K=0.8 for Dipole, K=0.73 for Yagi and K=0.6 for Patch antenna.

Actual value: D=2dB & Gain=1.5dB




41

Tabular Column

SL

No

Angle

degrees

Power

dBm




42

ADVANCED COMMUNICATION LAB (06ECL 67) – VIVA-VOCE

1. What are the types of digital modulation techniques?

3 types – ASK, FSK, & PSK.

2. What is ASK?

Switching amplitude of carrier in accordance with the message bit.

3. Write applications of ASK?

In optical communication.

4. Define FSK.

This modulation process involves switching the frequency of carrier in accordance with incoming data, by

keeping the amplitude and phase constant.

5. What are applications of FSK?

Microwave links & telephone links.

6. Define PSK.

Switching phase of carrier in accordance with the incoming data.

7. What are the applications of PSK?

Microwave links & telephone lines.

8. What is QPSK?

QPSK is a combination of 2 PSK signals.

9. What are the applications of QPSK?

Used in 3G mobile technologies.

10. Differentiate between ASK & FSK.

ASK FSK

1. Amplitude is changing w.r.t. incoming data. 1. Frequency is changing w.r.t. incoming data.

2. Phase is constant. 2. Phase is constant.

3. Frequency is constant. 3. Amplitude is constant.

4. Single generator is needed in the circuit. 4. Two generators are needed in the circuit.

11. Sate sampling theorem.

If the highest frequency spectral component of a magnitude time function m(t) is fm then the instantaneous

sample taken at a rate of fs > 2fm contain all the information of the original message.

12. What is coherent and non coherent type of detection?

Coherent – The received signal is multiplied with a carrier of same frequency as that at the transmitter.

Non coherent – The received signal is just passed through a BPF.




43

13. What is an optical fibre?

It is a dielectric waveguide that transmits optical messages.

14. What are the advantages of optical fibre communication?

Immunity to interference, No cross talk, Isolation from electric shock, No electromagnetic interference.

15. What are the types of optical fibres?

Step & graded index.

16. What is step index fibre?

Refractive index of core is constant throughout but there is abrupt change at core cladding boundary.

17. What is a graded index fibre?

Refractive index of core varies radially.

18. What is numerical aperture of step index? NA = √n12 – n2

2

19. What is numerical aperture of graded index? NA = √nr – n22

20. What is V number?

Its an important parameter and determines the number of nodes form an optical fibre.

21. What are the material used in manufacturing of optical fibre?

Glass & Plastic.

22. Mention methods to manufacture of optical fibres?

Direct melt, OVPO (outside vapor phase oxidation), MCVD (modified chemical vapor deposition).

23. What is attenuation?

Loss of signal power.

24. How many types of losses are there in optical communication?

5 types – Absorption loss, Scattering loss, Bending loss, Core-cladding loss, & Dispersion.

25. What is absorption loss?

Occurs due to defects in the structure of material. Light is absorbed instead of being reflected.

26. What is scattering loss?

Change in RI along the line of propagation causes scattering.

27. What is bending loss?

When there is a bend in the optical fibre, there will be certain losses associated to it.

28. What is a repeater?

A repeater is a device consisting of a receiver and a transmitter connected back to back.

29. What is an optical amplifier?

It is a device that directly amplifies the light directly usinga pump source.

30. Mention two optical transmitters.

LED and LAER.




44

31. Compare LED and LASER.

LED LASER

1. Emits light in all directions. 1. Emits light only in one direction.

2. Comes in 2 configurations – edge emitting LED

& surface emitting LED.

2. Comes in 2 forms – fabry perot resonator &

distributive feed back.

32. What are the types of optical receivers?

PIN diode & avalanche photodiode.

33. What is meant by splicing?

Joining two optical fibres into a single fibre.

34. What is WDM?

Wavelength division multiplexing – sending of 2 different signals of different wavelength on the same

optical fibre at once.

35. What are the types of misalignment?

Axial, angular, and lateral.

36. Categorize transmission lines.

3 types – Open wire, Coaxial, and Waveguide.

37. How many fields are required to analyze a waveguide?

Two fields are required to analyze a waveguide – Electric & Magnetic.

38. How types of wave propagation are there in waveguide?

3 types – TE, TM, and TEM.

39. What is TE mode?

Only a perpendicular electric field.

40. What is TM mode?

Only a perpendicular magnetic field.

41. What is TEM mode?

Mutually perpendicular electric and magnetic fields and perpendicular to direction of propagation.

42. What is cut-off wavelength?

A waveguide act as a high-pass filter and has a wavelength corresponding to cut-off frequency. λ = 2a.

43. What is attenuator?

Attenuator is a microwave component used to attenuate microwave power.

44. Name a power absorbing material.

Dielectric slab coated with aquadag.

45. What are the applications of waveguide twist?

Waveguide twists are used to obtain the desired plane of polarization.




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46. What is isolator?

Isolator is a microwave component which offers low insertion loss in forward direction of propagation and

offers high insertion loss in reverse direction of propagation of wave.

47. What is frequency meter?

It is similar to high frequency tank circuit. It is used to measure the frequency at source directly.

48. What are the applications of frequency meter?

Frequency meter will absorb a little power, so we notice a dip in the output power levels when the right

frequency matches. The readings are in GHz.

49. What is wave guide detector mount?

Detector mount consists of crystal diode detector. BNC female connector is provided for connecting the

measuring instrument through BNC-BNC male cable.

50. What is the application of detector mount?

It si used to measure input and output power.

51. What is GUNN Oscillator?

They are solid state microwave power generators.

52. What is PIN modulator?

PIN modulators are design to modulate CWO/P of GUNN Oscillator with square wave modulating signal.

It is operated by square wave pulses derived from Gunn power supply.

53. What is directional coupler?

A directional coupler is a four-port passive device commonly used coupling a known fraction of the

microwave power to a port the auxiliary line while flowing from input port to output port in the main line.

54. What are the applications of directional coupler?

Measurement of microwave power, impedance, frequency, etc.

55. What is coupling factor?

Ratio of incident power to forward power expressed in decibels.

56. What is the directivity of directional coupler?

Ration of forward power to back power expressed in decibels.

57. What are the losses in directional coupler?

Transmission loss & Return loss.

58. What is transmission loss?

Ratio of incident power to transmitted power in decibels.

59. Define return loss.

Ratio of incident power to reflected power expressed in decibels.

60. What are applications of waveguide Tees in microwave transmission?

Tees are used to connect a branch of section of waveguide in series or parallel with the main waveguide

transmission line for either splitting or combining power in a waveguide system.




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61. What is magic Tee?

Combination of E-plane Tee and H-plane Tee is known as magic Tee.

62. What are the applications of magic Tee?

E-H tuner for impedance matching, Balanced mixer in superheterodyne receiver, Power combiner,

Duplexer in radar systems.

63. Why microwave signals are used in waveguides?

The waveguides will be too bulky for low frequency signals.

64. What is used as a microwave switch? PIN diode.

65. What is Duplexer?

A device issued for transmission and reception without mutual interference.

66. What are the types of microwave antennas? Horn & Parabolic.

67. What is beam width of an antenna?

Angular width of a beam measured between the lines of half power intensity.

68. What is radiation intensity?

Power radiated from an antenna per unit solid angle.

69. What is directivity?

Ratio of radiation intensity in that direction to the radiation intensity of a reference antenna.

70. Define Electronic Tuning Range (ETR). Difference between two frequencies f2 and f1.

71. How ETR is determined? ETR is determined by using mode curves.

72. Define Electronic Tuning Sensitivity (ETS).

Ratio of difference between frequencies (or ETR) to the difference between two voltages V2 and V1.

73. What is VSWR? Ratio of maximum voltage to minimum voltage.

74. Explain slotted lines.

Lower part has four legs with adjusting screws on which the wave guide is mounted, The waveguide as a

longitudinal narrow slot on the surface of board wall as at this point, The upper most part is carriage that

can accommodate a tunable detector probe, A vernier scale is fixed on this, Carriage moves over the main

scale fitted on legs, The detector probe extends inside the waveguide through slot without touching the

waveguide wall, The vernier and the main scale arrangement facilitates in measurement of probe position.

75. What are applications of slotted line?

Used in finding out – VSWR, Load impedance, Waveguide, Wavelength,etc.

By: MAHESH PRASANNA K.,

DEPT. OF E & C, AIET.

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ADVANCED COMMUNICATION LAB (06ECL 67) – QUESTION BANK

IA MARKS: 25 EXAM MARKS: 50

1. Design and Demonstrate the working of TDM of two band limited PAM signals m1 and m2 of frequencies

500Hz and 2 KHz respectively.

2. Design and develop an ASK system to transmit 1Kbps of binary data. Use a suitable carrier and then

demodulate the same to recover the digital data.

3. Design and Implement an FSK system for transmission of binary data of rate 500bps to 2Kbps. demodulate

the same and display the binary bit steam.

4. Design and Implement BPSK modulation system with a suitable circuit and demodulate the same.

5. Demonstrate the working of a DPSK encoder and decoder. Sketch the waveform at each stage.

6. Demonstrate the working of a QPSK modulator and demodulator and record the waveforms at each stage.

7. Conduct an experiment for Measurement of Propagation loss, Bending loss and Numerical Aperture in a

given optical fiber. Plot the graph for variation in bending loss.

8. Conduct an experiment for Measurement of Frequency, Guide Wave Length, Power, VSWR and

Attenuation in a Microwave Test Bench (using Reflex Klystron).

9. Conduct an experiment to transmit and receive an analog signal using multi channel PCM CODEC Chip.

10. Multiplex an analog voice and digital data through Fiber optic link and measure bit rate, slot time and

frame time.

11. Evaluate the following parameters with respect to Micro strip devices.

(a) Ring resonator- Measurement of resonant frequency and Dielectric constant of the substrate.

(b) Directional coupler- Measurement of coupling factor and Isolation.

12. Evaluate the following parameters with respect to Micro strip devices.

(a) Ring resonator- Measurement of resonant frequency and Dielectric

constant of the substrate.

(b) 3dB power divider- Measurement of Power division and Isolation.

13. Conduct an experiment to measure the directivity and gain of the Yagi antenna.

14. Measure the 3dB Bandwidth from radiation pattern of Yagi antenna in H-plane.

15. Conduct an experiment to measure the directivity and gain of the Patch antenna.

16. Measure the 3dB Bandwidth from radiation pattern of Patch antenna in H-plane.

By: MAHESH PRASANNA K.,

DEPT. OF E & C, AIET.

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Documents

AIET_AC_Lab