adv.commn lab manual

LABORATORY MANUAL

FOR

ADVANCED COMMUNICATION LAB

10ECL67

VI Semester

Department of Electronics & Communication Engineering

B.N.M.Institute of TechnologyBanashankari II Stage,

Bangalore 560 070

Feb – May 2016

B.N.M.I.T Dept. of ECE Advanced Communication Lab – 10ECL67

ADVANCED COMMUNICATION LABSYLLABUS

Sub Code : 10ECL67 IA Marks : 25 Hours /Week :3 Total Hour : 42 Exam Hours: 3 Exam Marks: 50

LIST OF EXPERIMENTS

1. TDM of two band limited signals.

2. ASK and FSK generation and detection

3. PSK generation and detection

4. DPSK generation and detection

5. QPSK generation and detection

6. PCM generation and detection using a CODEC Chip

7. Measurement of losses in a given optical fiber (propagation loss, bending loss) and

numerical aperture

8. Analog and Digital (with TDM) communication link using optical fiber.

9. Measurement of frequency, guide wavelength, power, VSWR and attenuation in a

microwave test bench

10. Measurement of directivity and gain of antennas: Standard dipole (or printed

Dipole), microstrip patch antenna and Yagi antenna (printed).

11. Determination of coupling and isolation characteristics of a strip line (or

microstrip) Directional coupler

12. (a) Measurement of resonance characteristics of a microstrip ring resonator and

determination of dielectric constant of the substrate.

(b) Measurement of power division and isolation characteristics of a microstrip

3 dB power divider.

BNMIT/T Feb – June 2016 2


GENERAL INSTRUCTIONS:

1) Test the components/devices before starting experiment

2) After rigging up the circuits do not switch on the power supply, show the circuit to lab in charge and

then start the experiment.

3) Conduct the experiment as per procedure.

4) Record the readings as per instructions.

5) Confirm successful completion of experiments by plotting the relevant graphs and calculations.

6) After completion of experiment replace the components in their respective positions.

7) Negligence of one candidate will result in penalty for the whole group/batch.

8) Keep components and test Devices in good condition. Replace probes, wires and components at the

first sign of deterioration.

9) Do not work on equipments before you know proper procedures.

10) Keep the lab Clean.

Note: Instructions to use Microwave LAB

The Government presently sets the maximum exposure to microwave radiation at 10 mW/cm 2. If

the microwave components we will be using are not completely closed, leakage radiation can

exceed this maximum at certain frequencies. Therefore, before turning on the signal generator, the

waveguide sections must be tightly secured with a minimum of two screws placed diagonally on

the waveguide flanges. Never operate the generator until the waveguide sections are completely

secured. If you wish to observe the interior structures of the various microwave components, do

this while the circuit is apart and hold up the component to the light. Never stare into an open

waveguide while the generator is operating and connected. The eye is particularly susceptible to

microwave radiation damage. If the above instructions are followed, the operation of these

experiments will be completely safe.



CONTENTS

EXP. NO

TOPIC PAGE N0

1. TDM of two band limited signals. 32. ASK generation and detection. 63. FSK generation and detection. 84. PSK generation and detection. 105. Measurement of frequency, guide wavelength, power, VSWR and

attenuation in a microwave test bench12

6&7.

(6.1) Measurement of resonance characteristics of a microstrip ring resonator and determination of dielectric constant of the substrate.(6.2) Measurement of power division and isolation characteristics of a microstrip 3 dB power divider.

(7) Determination of coupling and isolation characteristics of a stripline (or microstrip) directional coupler.

15

24

8. QPSK generation and detection. 26

9. Measurement of losses in a given optical fiber (propagation loss, bending

loss) and numerical aperture.

29

10. Analog and Digital (with TDM) communication link using optical fiber 31

11. DPSK generation and detection. 46

12. Measurement of directivity and gain of antennas: Standard dipole (or printed dipole), microstrip patch antenna and Yagi antenna (printed).

48

13. Pin Details

Experiment No. 1BNMIT/T Feb – June 2016 4


TIME DIVISION MULTIPLEXING

AIM: To design and demonstrate the working of TDM for band limited signals with and Hz message signals with the help of suitable circuit. Demultiplex the above TDM signal.

m1(t) : message signal (1) : triangular signal, 3Vpp, 500Hzm2(t) : message signal (2) : sinusoidal signal, 2Vpp, 1kHzControl input signal at pin 11 of IC CD 4051: pulse of 5V, 8 KHzSupply: VDD = 5v, VSS = 0 and VE E = -5v

Pin Diagram

INH C B A ONChannel

0 0 0 0 00 0 0 1 10 0 1 0 20 0 1 1 30 1 0 0 40 1 0 1 50 1 1 0 60 1 1 1 71 X X X NONE

CD4051 is a CMOS 8:1 and 1:8 analog MUX/DEMUX

Features of CD4051 CD4051 is a 8-1 analog multiplexer & demultiplexer.


PINNO

ChannelNumber Mode MUX/DEMUX

13 0 IN/OUT14 1 IN/OUT15 2 IN/OUT12 3 IN/OUT1 4 IN/OUT5 5 IN/OUT2 6 IN/OUT4 7 IN/OUT3 - OUT/IN

6(INH) is kept Gnd9,10 & 11 are select lines


It has low ON resistance i.e. around 125Ω. It has very high OFF resistance; a very low leakage current of around ±100pA. Input voltage range ±(5 - 15V). (VDD - 0.5V, VEE + 0.5V) Power supply range: ± 5 - 15V. Binary address decoding

Procedure: Multiplexing:1. Rig up the circuit as shown in the circuit diagram.2. Feed the input message signal m1 (t) & m2 (t) to channel 0 (pin 13) and channel 1 (pin14) of

CD4051.3. The control signal is fed to pin 11 (A) with the pin 9(C) and 10(B) grounded.4. The multiplexed output is observed at Pin 3 on a CRO

Procedure: Demultiplexing:1. Rig up the de-multiplexing part of the circuit as shown in the circuit diagram.2. The multiplexed signal is fed as input to the demux (CD4051) at pin 3 that acts as input in

demux mode.3. The control signal is fed at pin 11 (A) keeping pin 9(C) and 10(B) at ground potential.4. The demultiplexed output at channel-0 (pin13) m1(t) and channel-1 (pin14) m2(t) is observed

on CRO.(Samples of m1(t) & m2(t)).

5. Design LPFs to get back m1(t) & m2(t). [Ex: cutoff frequency- fc = , for fc=8KHz select

c=0.01μF and calculate the value of R].6. To observe smooth demultiplexed o/p waveforms set fc=1MHz.

Observation:1. Amplitude of message signal 1 (sinusoidal)=____ VPP, Frequency = ______Hz.2. Amplitude of message signal 2 (triangular) = ____VPP, Frequency =_______Hz.3. Amplitude of pulse control signal = 0 – 5V, Frequency = ______kHz. (Use TTL output)4. Amplitude & frequency of demultiplexed message signal

m1(t) = ____V ; _____Hz; m2(t) = ____V; ______Hz.

Viva Questions:

1. What is TDM?

2. What is FDM?

3. Compare TDM and FDM?

4. What are the applications of TDM?

TDM waveforms:



Experiment No 2

AMPLITUDE SHIFT KEYING

AIM: Design and demonstrate an ASK system to transmit bits/sec digital data using suitable carrier. Demodulate the above signal with the help of suitable circuit.

CIRCUIT DIAGRAM

Note: Use 5V Pulse at Control (Pin 11) irrespective of signal amplitude at Pin 13 & 14.PROCEDURE:

Modulation:1. Rig up the circuit as shown above.2. The message signal (0 – 5V pulse or TTL output) is fed to the control input as message signal

i.e. Pin 11 of IC CD 40513. The carrier signal (sinusoidal wave of 5Vpp, 10 KHz) is fed to Pin 14 of the IC CD 4051.4. The output ASK signal is observed on a CRO.

Demodulation:1. Rig up the circuit as shown above.2. The ASK generated is fed at the input of the detector circuit (Envelop detector).3. The output of the envelop detector is passed through the comparator with reference voltage.4. The output of the comparator is the recovered message signal that is compared with the input

message signal.


Modulator


Design: 1. Fix the threshold at comparator input as 0.45V ( )

2. Then

3. With V=5v and R1=10KΩ, select R2.

4. To design R and C values of envelope detector:

or select 10RC= With C=0.1µF, select R

Observation:1. Message signal Amplitude Am=_____ Vpp

(Control signal m1 (t)) Frequency fm=_____ Hz 2. Carrier signal Amplitude Ac= _____ Vpp

(Sinusoidal c(t)) Frequency fc = _______Hz 3. Modulated signal Amplitude A = ______Vpp

4. Demodulated signal Amplitude Ad = _____ Vpp

VIVA Questions:

1. State the difference between Analog systems and digital systems.

2. Explain why digital systems are considered superior than Analog systems.

3. Mention the disadvantages of Analog communication.

4. Explain the basic steps involved in digitizing a signal.

5. Explain ASK operation.

Waveforms:



Experiment No 3

FREQUENCY SHIFT KEYING

AIM: To design and demonstrate the working of FSK with suitable circuit for Hz and Hz carrier signal. Demodulate the above signal with the help of suitable circuit.

Circuit Diagram

Procedure1. Generation:

Modulating signal (frequency 100 Hz) 0 – 5V pulse is applied to Pin no. 11, two carrier signals of frequencies 1 KHz and 10 KHz of 5 Vpp each are applied to pin no 13 and pin no 14. FSK output is obtained at pin no. 3.

2. Detection:FSK signal is applied to the demodulator circuit along with C1(t) or C2(t) as shown in figure to get ASK output.

The original modulating signal is obtained at the output of the ASK demodulator circuit.

Observation: Message signal Amplitude Am =______ Vp-p (Control signal m1 (t)) Frequency fm =________Hz Carrier signal Amplitude Ac = __ ____Vp-p (Sinusoidal c(t)) Frequency fc = ______Hz Modulated signal Amplitude A = _______Vpp

Demodulated signal Amplitude Ad = _______Vpp



Waveforms:

Viva Questions:

1. State the difference between discrete and digital signals.

2. Define Quantizing.

3. Define Encoding.

4. Explain PCM encoding.

5. State the difference between pulse modulation and digital modulation.

6. Explain FSK circuit operation.



Experiment No 4

BINARY PHASE SHIFT KEYING

AIM: To design and demonstrate the working of BPSK modulated signal. Demodulate the BPSK signal to recover the digital data.

CIRCUIT DIAGRAM:

BPSK MODULATOR

DEMODULATOR



Procedure:Generation:Rig up the circuit as shown in circuit diagram.A carrier of 3KHz, 5Vpp and a modulating signal of 100 Hz ,5Vpeak is applied.BPSK output is observed on CRO.Detection:BPSK signal is applied to one of the demodulator terminal and to the other terminal carrier signal is applied.Output of the op-amp is ASK which is then applied to the ASK demodulator by adjusting amplitude and frequency of ASK.

Observation: Message signal : Amplitude Am =_______ Frequency fm=_____Hz.(Control signal m (t)) Carrier signal : Amplitude Ac = __ Vpp Frequency fc = ____Hz (Sinusoidal c(t)) Modulated signal Amplitude A = ________Vpp . Demodulated signal Amplitude Ad = _________Vpeak

Waveforms:

Experiment No 5BNMIT/T Feb – June 2016 13


Measurement of frequency, guide wavelength, power, VSWR and attenuation of Microwave signal with Microwave test bench.

AIM: To Measure frequency, guide wavelength, Power, VSWR and attenuation of microwave signal

with Microwave test bench.

Initial Setup for Klystron Power:1. Assemble the equipment as shown in the block diagram in microwave test bench2. Keep the repeller voltage at the maximum & beam voltage minimum position before

switching on klystron Power Supply 3. Switch on the klystron Power supply and increase the beam voltage gradually so that 18mA to

20mA4. Slowly reduce the repeller voltage and adjust the modulating signal amplitude & frequency to

get a clear waveform on the CRO screen.Note: Repeller voltage should not be kept below 90 volts

Procedure to turn-off Klystron Power supply:1. Make Repeller voltage maximum2. Make Beam voltage minimum3. Turn off HT4. Turn off Mains

Block Diagram for frequency and attenuation (Probe connected to crystal detector of matched load)

Procedure to measure Frequency of microwave:

1. Make the initial set-up, so that square wave appears on CRO.

2. Slowly rotate the frequency meter until a dip is seen in the output waveform

3. Note down the frequency in G z

4. Note down the frequency of microwave at different repeller voltage


Klystron power supply

Reflex klystron oscillator

Isolator

Attenuator

Frequency meter

Crystal detector

Slotted section with carriage

CRO

Matched Load


Tabular column

(Note: The frequency is measured using the cavity wave meter which is an absorption type

wave meter which gives the dip at tuned frequency; frequency meter is detuned after the

frequency measurement.)

Procedure to measure attenuation

a) Make the initial set-up, so that square wave appears on CRO.

b) Note down the initial square wave voltage level Vin(without attenuation)

c) Rotate the attenuator knob, so that the microwave traveling through wave guide gets

attenuated

d) Now completely rotate the attenuator knob and note down the voltage level of attenuated

square wave(Vo)

e) Calculate attenuation offered by the attenuator which is given by :

Attenuation = (Vin/Vo) Attenuation in dB = 20 log (Vin/Vo)

Block Diagram for VSWR and Guide wavelength (λg)

(Probe to be connected to crystal detector of slotted carriage)


Klystron power supply

Reflex klystron oscillator

Isolator

Frequency meter

Crystal detector

Slotted section with carriage

CRO / VSWR meter

Attenuator

Repeller Voltage (Vr) in volts

Frequency meter readings in GHz


Procedure for Measurement of VSWR


b) To find VSWR move the slotted section carriage, to get the maximum o/p

voltage and note down voltage level(Vmax)

c) Move the slotted section carriage, to get the minimum o/p voltage and note

down voltage level(Vmin)

VSWR=Vmax/Vmin

Procedure for the measurement of Guide wavelength λg


b) To find guide wavelength move the slotted section carriage, to get the maximum

o/p voltage and note the readings on the scale on slotted section(ie distance) say

d1 cm

c) Move the slotted section carriage, to get the maximum o/p voltage and note the

readings on the scale on slotted section(ie distance) say d2 cm

d) The distance between the two maxima output position

A = (d1-d2) =--------- cms

Guide wavelength λg =2xa=-------- cms



Experiment No. 6Experiments on Micro strip devices

6.1: To determine the resonating frequency of the given Ring resonator and also to measure the dielectric constant of substrate material using Ring Resonator.

EQUIPMENT: RF source, Receiver, Ring Resonator, connecting cables.

Ring Resonator

A micro strip ring resonator is a micro strip line bent in a circular shape to close upon itself. The main advantage in contrast to linear resonators is that no “end effects” need to be considered. The resonant frequency could be calculated assuming mean length of the resonators is multiple of the guide wavelength of the micro strip. There are two ways to loosely couple to a ring resonator, one is end coupling, the other is edge coupling. The end coupled structure (shown below) provides a pass band whenever the ring is a multiple of wavelengths. The edge coupled technique a "suck-out" is seen in the reflection coefficient (S11) whenever the ring is an integer number of wavelengths behaving like a band reject filter. This is the preferred method because the dips in S11 are very narrowband and therefore the resonant frequency is more accurately known. It has been pointed out that ring resonator technique is less suitable for accurate measurement of micro strip losses because of the increased surface wave radiation loss.

The effective dielectric constant= [n (Free space wavelength/Circumference)] 2

Types of coupling:

Equipment description:


Edge coupledEnd coupled


Microwave sourceMicrowave source consists of the frequency synthesizer which generates signals in the

frequency range 87 to 898MHz. Lower and higher frequencies are generated using down and up converters to cover a overall frequency range of 5MHz to 2000MHz.The power output is fairly constant at 3dBm.The frequency of the source can be varied by menu driven push button switches over the range of 5MHz to 2GHz in suitable steps of 50KHz ,100KHz, 250 KHz, 500KHz,1MHz,10MHz and 100MHz.

Microwave receiverReceiver measures the power received in dBm .To get the correct power the receiver has to be

tuned to the same frequency as that of the source by using menu driven switches. The receiver also uses up-down converters similar to the source.

Block diagram:

PROCEDURE:

a) Connect two 20dB attenuators in series at the output terminal of the source. Select the frequency of the Source as 1.0 GHz (1000MHz) and connect the output of attenuator to the receiver input and note down the direct power level (A) at the receiver by tuning the receiver to the frequency of the source.

b) Insert the device under test (Ring resonator) between source and receiver along with attenuator and note down the power level (B).

c) Vary frequency of source in steps of 100 MHz up to 1.9GHz and note down the readings (A) and (B) for each frequency (Reduce the step size to 10 MHz near resonating frequency)

d) Calculate the output power. Output power = (B-A)e) Plot the graph of frequency verses output power on ordinary graph.f) Calculate the resonating frequency of ring resonator.

Note: Theoretical value of resonating frequency=C/πD, where C =velocity of light D= Mean diameter of the ring resonator.

Tabular Column

Frequency Direct Reading (A)

Reading after inserting the Ring Resonator (B)

Output power (B-A)

1.0 GHz1.1 GHz1.2 GHz1.3 GHz

1.9GHz


Source Attenuator (40 dB)

Device under Test(Ring Resonator)

Receiver


To determine the Effective Di-electric constant of the given Ring resonator.

a) Measure the Outer diameter and inner diameter of the ring. Calculate the Mean diameter D = (outer dia + inner dia)/2 and Circumference=( π x D)b) Calculate the free space wavelength for the resonating frequency

λo = c/f where c= 3x108 m/s and f= resonating frequency. c) Effective di-electric constant = [n(free space wave length/ circumference)]2

Note: i) n=1 for half wave length ring resonator. ii) εr should be around 4.5.

RESULT: 1) Resonant frequency = ………….MHZ 2) εr=……………….Graph:

POWER DIVIDERS

6.2: To measure power division at output ports of Wilkinson Power divider (chip resistor type).

EQUIPMENTS: RF source, Receiver, Wilkinson Power divider, connecting cables and matched load.

Wilkinson power splitter


fres

f

Power in DBm


Power divider splits an input signal into two equal phase output signals, or combines two equal-phase signals into one in the opposite direction at the designed centre frequency. Wilkinson relied on quarter wave transformers to match the split ports to the common port. The resistor allows all three ports to be matched and it fully isolates port 2 from port 3 at the center frequency. The resistor adds no resistive loss to the power split, so an ideal Wilkinson splitter is 100% efficient.

A three port, an equal-amplitude, two-way split, single-stage Wilkinson is shown in the figure above. The arms are quarter-wave transformers of impedance 1.414Z0. Here is how the Wilkinson splitter works as a power divider: when a signal enters port 1, it splits into equal-amplitude, equal-phase output signals at ports 2 and 3. Since each end of the isolation resistor between ports 2 and 3 is at the same potential, no current flows through it and therefore the resistor is decoupled from the input. The two output port terminations will add in parallel at the input, so they must be transformed to 2xZ0 each at the input port to combine to Z0. The quarter wave transformers in each leg accomplish this; without the quarter-wave transformers, the combined impedance of the two outputs at port 1 would be Z0/2.

The characteristic impedance of the quarter-wave lines must be equal to 1.414xZ0 so that the input is matched when ports 2 and 3 are terminated in Z0.Consider a signal input at port 2. In this case, it splits equally between port 1 and the resistor R with none appearing at port 3. The resistor thus serves the important function of decoupling ports 2 and 3. Note that for a signal input at either port 2 or 3, half the power is dissipated in the resistor and half is delivered to port1. The isolation between port 2 and port 3 and vice-versa can be understood by the following: Consider that the signal splits when it enters port 2. Part of it goes clockwise through the resistor and part goes counterclockwise through the upper arm, then splits at the input port and continues counterclockwise through the lower arm toward port 3. The recombining signals at port 3 end up equal in amplitude (half power or the CW signal is lost in resistor R1, while half of the CCW signal appears at port 1. And they are 180 degrees out of phase due to the half-wavelength that the CCW signal travels and the CW signal doesn't. The two signal voltages subtract to zero at port 3 and the signal disappears, at under ideal circumstances. In real couplers, there is a finite phase through the resistor that will limit the isolation of the output ports.

Block diagram:

Procedure to verify POWER DIVISION in a micro strip 3dB power divider:

1. Connect two 20dB attenuators in series at the output terminal of the source. Select the frequency of

the Source as 1.5 GHz (1500MHz) and connect the output of attenuator to the receiver input and note

down the direct power level (A) at the receiver by tuning the receiver to the frequency of the source.

2. Insert the device under test (Power divider) between source and receiver along with attenuator such

that the port 1 is connected to the source, port 2 to the receiver and terminate port 3 with matched

load. Note down the power level (B) at Port 2.


Source Attenuator (40 dB)

Device under Test(Power divider)

Receiver





4. Repeat the above steps for different frequencies and tabulate the readings.

Tabular column for power division:

Frequency

Direct power reading (A) Power reading (B) at Port 2, port 3 –Matched Load

Power reading (B) at Port 3, Port 2 – Matched Load

1400MHz

1500MHz

1600MHz

Procedure to verify the ISOLATION CHARACTERISTICS of micro strip 3dB power divider:

1. Connect two 20dB attenuators in series at the output terminal of the source. Select the Frequency

of the Source as 1.5 GHz (1500MHz) Connect the output of attenuator to the receiver input. Note

down the direct power level (A) at the receiver by tuning the receiver to the frequency of the source.






load. Note down the power level (C) at Port 1.

4. Feed the input at port 3 and measure power division and isolation at port 1 and port 2 respectively.

Tabular column for ISOLATION CHARACTERISTICS:

FrequencyDirect power

reading (A)

Input given at Port 2 Input given at Port 3

Power reading (B) at Port 3, port 1 –Matched Load(Isolation)

Power reading (C) at Port 1, Port 3 – Matched Load(Power division)

Power reading (B) at Port 2, port 1 –Matched Load(Isolation)

Power reading (C) at Port 1, Port 2 – Matched Load(Power division)

1500MHz



Experiment no.7

DIRECTIONAL COUPLER

OBJECTIVE: To measure coupling factor, Isolation Characteristics and Directivity of Directional Coupler.

EQUIPMENT: RF source, Receiver, attenuators, connecting cables, Matched Load.

THEORY:Directional couplers are passive reciprocal networks having four ports. All four ports are

(ideally) matched, and the circuit is (ideally) lossless. Directional couplers can be realized in micro strip, stripling, coaxial and waveguide. They are used for sampling a signal, sometimes both the incident and reflected waves (this application is called a reflectometer, which is an important part of a network analyzer). Directional couplers generally use distributed properties of microwave circuits, the coupling feature is generally a quarter (or multiple) quarter wavelengths. Lumped element couplers can be constructed as well. The four ports are input port, through port (Direct) (where most of the incident signal exits), coupled (where a fixed fraction of the input signal appears, usually expressed in dB) and isolated port, which is usually terminated (where no signal exists ideally).The directional couplers are of two types. Namely Forward wave couplers and backward wave couplers.

Forward wave versus backward wave couplersWaveguide couplers couple in the forward direction (forward-wave couplers); Microstrip or

stripline coupler are "backward wave" couplers. The coupled port on a microstrip or stripline directional coupler is closest to the input port because it is a backward wave coupler. On a waveguide broad wall directional coupler, the coupled port is closest to the output port because it is a forward wave coupler.

DefinitionsInsertion Loss (IL) = 10 * log (Input port power/through port power)Coupling Factor (C) = 10*log (input port power/ coupled port power)Directivity (D)= 10 * log(power at coupled port/ power at isolated port)Isolation= coupling factor + DirectivityFor Forward Direction: For Reverse Direction:

Port 1 Port 2 Port 1 Port 2Input Direct Direct Input

Port 3 Port 4 Port 3 Port 4Coupled Isolated Isolated Coupled



Block diagram:

Procedure:

1. Connect two 20dB attenuators in series at the output terminal of the source. Select the frequency of

the Source as 1.5 GHz (1500MHz) and connect the output of attenuator to the receiver input and note

down the direct power level (Input power) at the receiver by tuning the receiver to the frequency of

the source.

2. Insert the device under test (Directional Coupler) between source and receiver along with

attenuator as per the diagram for forward direction, such that the port 1 is connected to the source,

port 2 to the receiver and terminate port 3 & Port 4 with matched load. Note down the power at Port 2

(through port power). Measure power at port 3 (Coupled port power) by terminating port 2 and port 4.

Also measure power at port 4 (isolated port power) by terminating port 2 and port 3 and Tabulate the

readings.

3. Connect the direction coupler as shown in figure for reverse direction and measure power at

different ports and tabulate the readings.

4. Calculate insertion loss, coupling factor, isolation and directivity.

Tabular column

Frequency

Forward Direction Reverse Direction

P1

Input

P2

Through

P3

Coupled

P4

Isolated

P2

Input

P1

Through

P4

Coupled

P3

Isolated

1400 MHz

1500 MHz

Result:

Insertion loss = P1 - P2 =……………dB

Coupling Factor = P2- P3 =……………. dB

Isolation (I) = P1 - P4 =……………..dBBNMIT/T Feb – June 2016 23

Insertion Loss (IL) = 10*log(P1/P2)

Coupling Factor (CF) =

10*log(P1/P3)

Isolation (I) = 10*log(P1/P4)

Directivity (D) = 10*log(P3/P4)

Microwave Source

Attenuator (40 dB)

Device under Test(Directional coupler)

MicrowaveReceiver


Directivity (D) = P3 - P4=………………dB

Experiment No 8

QPSK MODULATION AND DEMODULATION

AIM: Conduct a suitable experiment to modulate a digital signal using Quadrature phase shift keying technique and to demodulate the same

EQUIPMENTS:

Experimental Kit DCLT-012A, Connecting Chords, Power supply for the kit, 20MHZ Dual Trace Oscilloscope with logic scope facility

Functional Block: QPSK-Modulator

QPSK-Demodulator

I&Q Phase windows

Representation of dibits with phases Dibit (symbol) Phase(in degrees)

00 45°01 315°11 225°10 135°

Dibit MSB LSB

Phase Change

0 0 0°01 90°11 180°10 270°


Carrier Signal generator Analog SwitchPhase Switching Network

Di-Bit GeneratorDigital Information

Analog switch Di-bit serializerWaveshaping Ckt

Modulated Signal

DeModulated Signal


Procedure:

1. Connect power supply in proper polarity to the kit DCLT-012A and switch it on.

2. Connect DATA(S1) to DATA-IN(TP32).

3. Connect carrier generator block to the respective Sine wave degrees.

Sin 0° (TP26) ---> Sin 0° (TP21)

Sin 90° (TP27) ---> Sin 90° (TP22)

Sin 180° (TP28) ---> Sin 180° (TP23)

Sin270 ° (TP29) ---> Sin 270° (TP24)

4. Check for QPSK Modulated output (TP7) for given Data.

5. Connect Modulated output QPSK (Tx/TP7) to the receiver block of QPSK receiver.

6. Compare the LED output with input DATA (S1).

7. Observe various waveforms on CRO with Logic Scope facility.

NOTE: Use RESET switch if there is delay occurs at data out post and

WAVEFORMS

Clock

dk 1 1 0 0 0 1 1 1



QPSK waveform

Dibits 11 11 01 00 00 01 11 11

Phases 1800 1800 900 00 00 900 1800 1800


B.N.M.I.T Dept. of ECE Advanced Communication Lab - 10ECL67

EXPERIMENT 9 : OPTICAL FIBER Communication

AIM: a) To study the principles of Analog signal transmission and reception.b) To study Analog Signal TDM transmission and reception. c) To study the principles of Digital signal transmission and reception.d) To determine the Numerical Aperture of optical fiber.e) To determine the Losses (Connector, Propagation, Bending, Air-gap) f) To study the voice interface in two optical fiber patch cards

EQUIPMENTS: Digital Communication Lab Trainer – DCLT – 010 Fiber-optics Hybrid Module, PHM20B, CRO

THEORY:

Fiber Optic Links is used for transmission of digital as well as analog signals. Basically, a fiber optic link contains three main elements, a transmitter, an optical fiber & a receiver. The transmitter module takes the input signal in electrical form & then transforms it into optical (light) energy containing the same information. The optical fiber is the medium, which carries this energy to the receiver. At the receiver, light is converted back into electrical form with the same pattern as originally fed to the transmitter.

Fig 9.1: Fiber Optic Communication System

Every optic fiber consists of three strands, each inside the other. The center one, ‘Core’ is a special low loss grade of material that has a constant refractive index, i.e., its ability to bounce light along its length. The next one, the ‘Cladding’ and the outer one, ‘Sheath/Coating’ each have progressively lower refractive index, which stop the light straying from center. As transmissions are unaffected by the electrical interference and do not weaken quickly, fiber optics are popular for long distances, especially as transmission speeds are those of light itself. These are systems capable of carrying over

B.N.M.I.T Feb – June 2015 27


4000 voice circuits per fiber and transmitting at rates in excess of 4 MBPS over stage length of at least 100 Km without repeaters or regenerators.

Fig 9.2: Fiber Optic Cable Cross Section.

Advantages of Optical communication:

1. Very small cross talk : Very little light escapes from the fiber is absorbed through the cladding,

which provides good cross talk features.

2. Large bandwidth: A single mode fiber provides several ten-fold GHz x Kms of a graded index

fiber. This quantity is measured as the product of the bandwidth and unrepeated distance.

3. Low Loss: The loss of an optical fiber is less than 0.5 dB/Km, thus allowing unrepeated links

of about 60 Kms. By comparison loss of coaxial cable is around 20 dB/Km.

4. Bandwidth upgradability: The transmission rate can be upgraded up to one order of magnitude,

while utilizing the existing optical fiber.

5. Availability of material : Copper is limited, whereas silica is available in abundance.

6. Small size: Outer diameter of strand is approximately 0.1 mm, which means fewer cables are

necessary leading to reduced duct volume.

7. Lightweight and physical flexibility: The weight of the finished cable fiber is 10 to 30 % less

than that of a copper cable. Owing to its physical flexibility, the cable can be easily bent and be

installed along with existing conduit.

8. Electro magnetically Robust and Oxidation free : Optical fiber is free from the electromagnetic

induction and does not rust as in case of metals. As a consequence optical fibers can endure ad-

verse environments such as at the bottom of an ocean, can also be used in flammable or explo-

sive environments.



Digital Communication Lab Trainer – DCLT – 010

Fig 9.3: DCLT 010 Fiber optic Communication trainer

a) To study the principles of Analog signal transmission and reception

Theory:

For Analog signal transmission the drive circuit must cause the light output from an LED source to

follow accurately a time –varying input voltage waveform in both amplitude and phase. Therefore, as

indicated previously, it is important that the LED output power responds linearly to the input voltage

or current. Unfortunately, this is not always the case because of inherent non-linearities within LEDs

which create-distortion products on the signal. Thus the LED itself tends to limit the performance of

analog transmission systems unless suitable compensation is incorporated into the drive circuit.

However, unless extremely low distortion levels are required, simple transistor drive circuits may be

utilized.



Fig 9.4: Analog Link using OFCAnalog Link Procedure:

Connect (A5) to FO-LED (A) Reduce the amplitudes of all the analog signals except 250 Hz to zero (With the help of the potentiometers provided) Connect Photo transistor output ( C ) to I-V Amplifier (D2) Terminate the fiber optic cable both at source and detector. Adjust FO-LED current to maximum and the Level shift to minimum. The analog signal can be observed at the output of the level shifter.

Observations:

Observe the input of analog waveform and output analog wave form using CRO. It can be observed only the peak point of input was transmitted. Observe the input and output waveforms by gradually shifting the input by VR2 (It can be ob-

served there is a complete waveform transmission once the shifting DC bias is sufficient.) FO-LED being uni-directional components, the input bipolar signal sources have to be converted

to uni-direction signal above the FO-LED diode drop. This function is performed through the level shifter.

Repeat the above procedure for other analog signal sources 500 Hz and 1 KHz.

b) To study Analog signal TDM transmission and receptionB.N.M.I.T Feb – June 2015 30


Theory:

Fiber optic communication system supports Time division Multiplexed signals where the TDM o/p of different frequency analog signals. Since the signals are Bipolar and the optical source can respond to only bipolar signals, they are first level shifted in a DC level shifter where the bipolar signals are converted to unipolar. The TDM signal is then intensity modulated and then conveyed on the optical fiber. At the receiver end, a photo detector detects the signal from the light falling on it in the form of current. A Current-Voltage (I-V) Amplifier converts the current signals to voltage and amplifies them. This is then fed to a Demultiplexer where the individual signals are obtained.

TDM Procedure:

Connect TDM (A5) to FO-LED (A) Connect Photo Transistor output ( C ) to the input of the I-V Amplifier (D2) Terminate the fiber optic cable both at the source and the detector Adjust the amplitudes of all sources DC, 250 Hz, 500 Hz and 1 KHz to minimum

Observations:

Observe the waveforms at TDM out (A5) and I-V Amplifier input (D2) It can be observed that (D2) duplicating (A5), except FO reduced amplitude and rounding off rise

times. Observe the demultiplexed waveform at the output of Demultiplexer. The Demultiplexer output will be Sample and Hold version of input source. Observe the reconstructed signal at the output of Low Pass Filters at CH0, CH1, CH2 and CH3.

Fig 9.5: Waveforms for Analog Link and TDM

c) To study the principles of Digital signal transmission and reception

Theory: B.N.M.I.T Feb – June 2015 31


The modulator employs intensity modulation for conversion of electrical signals to optical signals. The operation of the LED for binary digital transmission requires the switching ON and OFF of a current in the range of several tens to several hundreds of mill amperes. This must be performed at high speed in response to logic voltage levels at the driving input.

The Optical Detector performs the linear conversion of the received optical signal into an electrical current. A photo transistor occupies this position where it detects the light signals falling upon it from the output of the fiber optic cable and generates the current signals proportional to it. Initial amplification is performed in the preamplifier circuit where it is essential that additional noise is kept to a minimum in order to avoid corruption of the received signal. The received optical signal may be distorted due to the dispersive mechanisms, within the optical fiber. Hence to compensate for this distortion and to provide a suitable signal shape, a pulse shaper will be included in the receiver block.

Fig 9.6: Digital Signal Link using OFCDigital Link procedure:

Connect 4 Khz digital source (A4) FO-LED (A) Connect photo transistor output (C) to digital receiver (D1) Terminate the fiber optic cable both at source and the detector Adjust FO-LED current to maximum (extreme anti clockwise).

Observations:



Observe an oscilloscope signal source at A4 and digital receiver output. Digital receiver output will be the inverse of signal source. Observe for distortion on the rising edge of received pulse.

Observe pulse shaper output (E) and source (A4). It can be observed both the signals are identical except for switching characteristics of photo transistor.

Repeat the experiment for other signal sources 8 KHz, 32 KHz and 64 KHz. It can be observed that the source frequency in increased, the photo transmitter switching times are

pronounced. Observe the change in phototransistors switching times as FO-LED current is reduced

Fig 9.6: Digital Signal Waveforms

d) To determine the Numerical Aperture of Optical Fibers

Theory:

Numerical aperture of any optical system is a measure of how much light can be collected by the

optical system. It is the product of the refractive index of the incident medium and the sine of the

maximum ray angle.

ni for air is 1, hence

For a step – index fiber, as in the present case, the numerical aperture is given by

For very small differences in refractive indices the equation reduces to

where Δ is the fractional difference in refractive indices.



Fig 9.7: NA measurement scheme NA Measurement Procedure:

Connect one end of the cable1 (1metre FO Cable) to FO LED of TNS20A and the other end to the NA Jig, as shown.

Plug the AC mains. Light should appear at the end of the fibre on the NA jig. Turn the Set Pout knob clockwise to set to maximum Po. The light intensity should increase.

Hold the white screen with the concentric circles (10,and 25 mm diameter) vertically at a suitable distance to make the red spot from the emitting fibre coincide with the 10 mm circle. Note that the circumference of the spot (outermost) must coincide with the circle. A dark room will facilitate good contrast.

Record L, the distance of the screen from the fibre end and note the diameter (W) of the spot. Compute NA from the formula:

Tabulate the reading and repeat the experiment for 25mm diameter too.

Table of Readings:SI No L (mm) W(mm) NA θ(degrees)

1. 10mm

2. 25 mm



e) To determine the Losses in Optical Fibers

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 as that of electrons, one has to consider the interaction of matter with the radiation 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 direction 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 known as propagation loss. Plastic fibers have higher loss of the order of 180 dB/Km. whenever the condition for angle of incidence of the incident light is violated the losses are introduced due to refraction of light. This occurs where fiber is subjected to bending. Lower the radius of curvature more is the loss.

When light travels down optical fibers, some of the light is absorbed by the glass or plastic. This means the light coming out of the end of the fiber is not as strong as the light going in to the fiber. When designing a fiber communications system, you need to know the size of this loss to calculate the maximum distance the signal will travel. In this experiment you will try one way of measuring the loss in the fiber. Other losses are due to the coupling of fiber at LED & photo detector ends.

The optical power at a distance, L, in an optical fiber is given by PL =PO 10 (-L/10) where PO is the launched power and is the attenuation coefficient in decibels per unit length. The typical attenuation coefficient value for the fiber under consideration here is 0.3 dB per meter at wavelength of 660mm. Loss in fibres expressed in decibels is given by –10 log(PO/PF) where, PO is the launched power and PF is power at the far end of the fiber.

Losses in fibres occur at fibre-fibre joints or splices due to axial displacement, angular displacement, separation (airgap), mismatch of cores diameters, mismatch of numerical apertures, improper cleaving and polishing at the ends. The loss equation for a simple fiber optic link is given as: Pin(dBm)-Pout(dB)=LJ1+LFIB1+LJ2+LFIB2+LJ3 (db):

where, LJ1 (db) is the loss at the LED-connector junction,

LFIB1 (dB) is the loss in cable1,

LJ2 (dB) is the insertion loss at a splice or in-line adaptor,

LFIB2 (dB) is the loss in cable2 and LJ3(dB) is the loss at the connector-detector junction.



Fig 9.8: Connector Loss measurement

Fig 9.9: Fiber Optic Cables and In-Line Adaptor

Connector Loss Measurement Procedure:

Connect one end of FO Cable1 (1-meter) to the FO LED of the TNS20A and the other end to the FO PIN.

Turn the DMM on and ensure the power meter is ready for use. Plug the AC mains. Connect the optical patch cord securely, as shown, after relieving all twists and

strains on the fiber. Note the output power reading with a single 6m optical fiber cable (Pout1) Next introduce a (1m + Connector + 5m) cable and note the output power reading. (Pout2) Connector Loss is given by the difference of the two measured power reading. (Po1-Po2 dB.)

SL Measured Output Power for 6m Cable Pout1

Measured Output Power for (1m + Connector + 5m) Cable Pout2

Connector Loss = Pout2 - Pout1

1.



Propagation Loss Measurement Procedure: Establish an analog link using a 1m cable. Note the output power reading Pout1

Next establish an analog link using a 3m cable and note down the power reading as Pout2

Next establish an analog link using a 5m cable and note down the power reading as Pout2

Determine the reduction in received power on introduction of additional 2m and 4m length of ca-ble.

SL Measured Output Power for 1m Cable Pout1

Measured Output Power for 3m Cable Pout2

Measured Output Power for 5m Cable Pout3

Propagation Loss on additional 2m of cablePout2 - Pout1

Propagation Loss on additional 4m of cablePout3 - Pout1

1.

Bending Loss Measurement Procedure: Establish an analog link using a 1m cable. Relieve the cable of all twists and strains, Note the reading Po1 for Cable 1 (1metre cable). Wind one turn of the fiber on the mandrel, (Bend diameter of approximately 10 cm) and note the

new reading of the power meter Po2. Now the loss due to bending and strain on the plastic fiber is Po2-Po1 dB.

Wind five turns of the fiber on the mandrel, (Bend diameter of approximately 10 cm) and note the new reading of the power meter Po3. Now the loss due to bending and strain on the plastic fiber is Po3-Po1 dB.

SL Measured Output Power for 1m Cable with No Bend. (Direct Reading)Pout1

Measured Output Power for 1m Cable with a single Bend of 10cm diameter.Pout2

Measured Output Power for 1m Cable with 5 Bends of 10cm diameter.Pout3

Bending Loss with 1 BendPout2 - Pout1

Bending Loss with 5 BendPout3 - Pout1

1.



Loss due to air gaps in fibers with in-line adaptorsTheory:

In-line adaptors are mechanical components, with which two optical fiber cables may be connected in series. These find application in all fiber optic systems. In-line adaptors without air-gap facilitate low loss connectivity. The loss arising out of such a connector may be limited to 0.5 to 1.0 dB. For reliable permanent connections between one fiber and another, fusion splices are ideal solution. Many fiber optic communication systems require attenuators in the optical path to ensure proper matching of signals between the source and the detector. In case of too large a signal from the transmitter, the receiver may get saturated. To facilitate adjustments of optical signal levels in optical fiber networks, attenuators are used. Attenuators are based on a variety of methods. Variable attenuators are also essential fiber optic accessories. One simple and popular way to attenuate optical power at fiber junctions is to create a known (fixed or variable) air-gap at the junction. All the light exiting from the transmitting side is not coupled to the receiving fiber, resulting in attenuation.

Air Gap Loss Measurement Procedure: Mark one face of the hexagonal lock nut with a pen. Connect one end of the 1-meter FO cable

(designated as Cable1) to FO LED of TNS20A, keeping the connector with the marking on the hexagonal lock nut free.

Connect one end of the 5 meter FO cable (designated as Cable2) to FO PIN of TNS20A. Next connect the free end of Cable1 (with the making) to the in-line adaptor by rotating it. Connect the free end of Cable2 to the other side of the in-line adaptor tightly, but without force.

Note down the power reading P1. Next loosen the lock-nut with the marking by one turn. Pull the cables gently apart so as to create

an air gap in the ILA that corresponds to one thread of the connector (=0.7mm). Note the meter reading as P2.

Unwind another full thread of Cable1 and pull the cables apart gently to create an air gap of 1.4mm. Note the meter reading as P3.

Do not disturb cable2 position in the in-line adaptor. The losses due to the air-gaps are given by the P2-P1 and P3-P1 (in db). Repeat the experiment for other settings of optical power

Length of Fiber Optic Cable Used: __________SINO

Direct ReadingP1(dBm)

Power Reading With air gap of 0.7mm P2(dBm)

Power Reading With air gap of 1.4mm P3(dBm)

Loss for .7mmair-gap (dB)P2-P1

Loss for 1.4mmair-gap (dB)P3-P1



f) To study the voice interface in two optical fiber patch cards

Fig 9.10: Fiber Optic Cables : Voice Interface



Voice Interface Experimental Setup and Procedure:

The DCLT-010 main card and the Voice interface cards are used for this expt. Connect the microphone to Audio IN connector on the voice interface card. Connect the speaker to the audio OUT connector on the voice interface card. The analog signal output from Audio gain amplifier (Point “S1”) is connected to the Input of the

FO led source (POINT “A”) Connect the FO LED source output to the FO-PHOTO TRANSISTOR Connect the signal output from the Photo Transistor (POINT “C”) to the low pass filter circuit of

the I-V amplifier (POINT “D2”) Connect the low pass filter output CH1 from DCLT010 main board to the to the Audio output

(POINT “S2”) of Voice interface card The voice signal input from the microphone is converted into analog and then transmitted through

the Fiber Optic cable and reconstructed back with and connected to Speaker.

Observations:

Observe the Voice performance at the speaker out put in voice interface card Vary the pot “VR1” in voice interface card to control the volume It can be observed that by varying the pot “VR6” the intensity of the voice passing through fiber

optic cables can be observed. Repeat the experiments for the 5mts and also 6mts cable and observe the

Experiment No 10



DPSK MODULATION AND DEMODULATION

AIM : Conduct a suitable Experiment to modulate a digital signal using differential phase shift keying technique and to Demodulate the same.

EQUIPMENTS: Experimental kit DCLT-005A; Connecting Chords, Power supply for the kit; 20MHz Dual Trace Oscilloscope.

Block Diagram

Differential encoding logic:


DIFFERENTIALENCODER

CARRIER MODULATOR

SCLCK

NRZ-L DATA

MODOUT

FIGURE: DPSK MODULATOR

BPSKDEMODULATOR DELAY

DECISION DEVICE / COMPARATOR

MOD INDATA

FIGURE: DPSK DEMODULATOR

DELAY Tb

D(t) B(t)

B(t-Tb)


PROCEDURE:

1. Connect S-DATA(S1) to S-DATA IN (S18).2. Connect DATA-NRZ-M (S20) to DATA CONTROL INPUT (S28).3. Connect CARRIER-0° (S24) to CARRIER-0° (S25).4. Connect CARRIER-180° (S23) to CARRIER-180° (S26).5. Check the modulated output at (S27). 6. Connect Modulated output (S27) to Demodulated input (S17).7. Check Demodulated output at (S21).8. Compare the demodulated output with S-DATA(S1) .9. Observe various waveforms, use RESET switch for clear observation of data output, if

recovered data mismatches with respect to the transmitter data. Note: After powering the board do press RESET BUTTON so that initial bit will be '0' Waveforms for input data 01011101

EXPERIMENT NO. 11



Microstrip AntennasOBJECTIVE: To measure antenna parameters of microwave standard printed Dipole antenna,

patch antenna and yagi antenna.

A. To plot the radiation pattern of antenna in Azimuth & Elevation planes on polar plots.

B. To measure the directivity and beam width.

EQUIPMENT: RF source, Receiver, connecting cables, Antenna Mounts with connecting cables,

Polarization connector, Dipole Antenna, patch antenna and yagi antenna.

Dipole Antenna Patch Antenna Yagi Antenna

Block diagram:



PROCEDURE:

To plot the radiation pattern of Micro strip Dipole antenna in Azimuth & Elevation planes:

1. Connect the Dipole Antenna to the transmitter antenna mount and set the source frequency to 1500

MHz.

2. Now connect the antenna under test (dipole/patch/yagi) to the Receiver antenna mount and set the

receiver to 1500 MHz. Set the distance between the antennas to be around 1.5 meter (approx. 5 ft.).

3. Adjust the receiving antenna tripod stand such that the power reading of receiver is maximum (Rx

antenna should be in line and is at 0 degree/direction of main lobe/boresight direction) and note down

the power reading.

4. Now rotate the Receiving antenna around its axis in steps of 10 degrees using graduated pointer on

Receiver Antenna mount (Goniometer) and note down the power reading and tabulate.

5. Plot the readings on a polar graph sheet (polar plot) and also linear plot on linear graph sheet.

6. The plot in horizontal plane is an Azimuth plot.

7. Now without disturbing the setup – rotate the Receiving antenna at receiver from horizontal to

vertical plane by using a polarization connector.

8. Similarly turn the transmitter Dipole to the other plane. Now rotate the Dipole antenna around its

axis in steps of 10 degrees and note down the power and tabulate the readings.

9. Plot the readings on a polar graph sheet (polar plot) and also on linear graph sheet (linear plot).

10. The plot in vertical plane is the Elevation plot of the antenna under test.

Ideal plots 1. Dipole antenna



2. Patch antenna 3. Yagi antenna

E-plane (blue) and H-plane (red) far-field patterns.

Observation:

Antenna under test:

Frequency of Operation: 1500 MHz (1.5GHz)

E plane Angle ( deg) Receiver

Reading(dBm)

H plane Angle

(deg)

Receiver Reading(dBm)

0 0

10 10

20 20

--- ---

--- ---

--- ---

340 340

350 350



To find the half power beam width(θHP,Φ HP ):

1. Mark the -3dB points on the plot and find the angle between the -3dB points to get the Azimuth

beam width θHP from Horizontal Plane and Elevation beam width ΦHP from vertical Plane of the

antenna.

2. The directivity can be found by measuring Azimuth and Elevation beam widths and using the

relation:

Directivity of the antenna (D) = (41,000(deg^2) / θHP *ΦHP.)

Directivity of the antenna (D dB) = 10logD dBi where dBi = decibels over isotropic.



Annexure – IDatasheets of ICs

GENERAL PURPOSE SINGLE OPERATIONAL AMPLIFIERUA741

ABSOLUTE MAXIMUM RATINGSSymbol Parameter UA741M UA741I UA741C UnitVcc Supply Voltage 22 VVid Differential Input Voltage 30 VVi Input Voltage 15 VPtot Power Dissipation 500 mWOutput Short-circuit Duration InfiniteToper Operating Free Air Temperature Range -55 to +125 -40 to +105 0 to +70 oCTstg Storage Temperature Range -65 to +150 -65 to +150 -65 to +150 oC

This datasheet has been download from:www.datasheetcatalog.com



IC LM 324- Quad Op-amp



IC CD 4051 Analog Mux/Demux



MICROSTRIP Equipment Details.

Equipment description

CONTROLS & THEIR DESCRIPTION:LCD: This 16X2 Liquid Crystal Display is used to display the frequency of signal being generated along with memory locations etc. The range is from 5.0 MHz to 2000.0 MHz. various step sizes for scrolling frequency upward or downward are available from 50 KHz, 100KHz, 250KHz, 500KHz, 1MHz and 10MHz. The frequency displayed on Power ON is the frequency stored in the memory before power was switched off.UP: This push button is used to increase the generated frequency by selected step size. Pressing it longer will star t the scroll mode and frequency w ill star t to roll slowly and then faster. Further this button could be used to scroll up the menu options, memory locations etc. The frequency shall increase in 3 bands and shall be available at 3 separate output BNC’s. LED’s corresponding to particular bands shall light up indicating that user has to change connections.DOWN: This push button is used to decrease the generated frequency by selected step size. Pressing it longer will star t the scroll mode and frequency will start to roll slowly and then faster. Further this button could be used to scroll down the menu options, memory locations etc.MENU: This push button is used to select the operation modes like frequency step size from 50KHz to 10MHz, also to change from Manual to auto modes. In auto mode the transmitter frequency shall advance in selected step sizes automatically at intervals of around 1 second. Upon reaching the displayed frequency the unit will send out a trigger pulse signaling the receiver that it has changed itsfrequency and receiver should follow.ENTER: This push button is used to store a particular frequency in the current location of memory and also to select and store a particular step size and initiate serial dump. Frequency and level both are stored at any desired memory location on pressing this button. This display w ill blink to indicate that frequency has been stored.ESCAPE: This push button is used to cancel any command and revert to default position.FM/CW: This toggle switch is used to select the modulation. CW is used for taking antenna measurements, as the level remains stable in this mode. FM is used to frequency modulate voice or tone etc for communication. The FM deviation has been limited to around 100 KHz.MIC/1KHz: This toggle switch selects the modulating signal from either microphone or internally generated 1 KHz sine wave signal.DEPTH: This potentiometer is used to vary the frequency deviation of the FM signal. Rotating clock wise w ill increase the deviation and vice versa.B.N.M.I.T Feb – June 2015 51


MIC: This earphone input socket is used to connect the condenser microphone provided. This will frequency modulate voice signal on the carrier frequency as displayed.EXT: This BNC input is used to connect any external audio signal for frequency modulating the generated carrier.TRIGGER OUT: This BNC is used to send the pulses to the receiver when Tx is operating in auto mode.RF OUT 87-898MHz: This is w here the transmitted signal is present with frequency of 87-898MHz. Its output impedance is 50 ohms. The transmitting antenna can be connected to it using the BNC lead provided. Output level is around 100-110dBuV. An external attenuator of 40dB can be connected here to reduce the output level by 100 times.DOWN CONVERT ER OUTPUT 5-86 MHz: This is w here the transmitted signal is present with frequency of 5-86MHz. Its output impedance is 50 ohms. The transmitting antenna can be connected to it using the BNC lead provided. To generate these frequencies one needs to connect the output of RF OUT BNC to INPUT BNC of this down converter using the shorter BNC leads provided. This down converter requires a variable frequency of 105.0 to 186.0 MHz to be down converted with its modulation content to the desired low frequencies. The RF OUT signal is mixed here with a fixed signal of 100MHz to achieve this. An external attenuator of 40dB can be connected here to reduce the output level by 100 times.DOWN CONVERTER INPUT: This BNC is used to connect to the RF output for down-conversion.UP CONVERTER OUTPUT 899-2000MHz: This is w here the transmitted signal is present with frequency of 900-2000MHz. Its output impedance is 50 ohms. The transmitting antenna can be connected to it using the BNC lead provided. To generate these frequencies one needs to connect the output of RF OUT BNC to INPUT BNC of this up converter using shorter BNC leads provided. This up converter requires a fixed frequency of 479.5 MHz to be up converted with its modulation content to the desired high frequencies. An external attenuator of 40dB can be connected to reduce the output level by 100 times.UPCONVERTER INPUT: This BNC is used to connect to the RF output for up conversion.

CONTROLS & THEIR DESCRIPTION:

LCD: This 16X2 Liquid Crystal Display is used to display the frequency of signal being received along with memory locations etc. The range is from 5.0 MHz to 2000.0 MHz. Various step sizes are available from 50KHz, 100KHz, 250KHz, 500KHz, 1MHz and 10MHz for scrolling the frequency upward or downward. The frequency displayed on Power ON is the frequency stored in the memory before power w as switched off.UP: This push button is used to increase the received frequency by selected steps. Pressing it longer will start the scroll mode and frequency w ill star t to roll slowly and then faster. Further this button could be used to scroll up the menu options, memory locations etc.B.N.M.I.T Feb – June 2015 52


DOWN: This push button is used to decrease the received frequency by selected steps. Pressing it longer will start the scroll mode and frequency will star t to roll slowly and then faster. Further this button could be used to scroll down the menu options, memory locations etc.MENU: This push button is used to select the operation modes like frequency step size from 50 KHz to 10MHz.and also to change from Manual to auto modes and call serial mode.ENTER: This push button is used to store a particular frequency in the current location of memory and also to select and store a particular step size and initiate serial dump. Frequency and level both are stored at any desired memory location on pressing this button.ESCAPE: This push button is used to cancel any command and revert to default position. RF IN 48-860 MHz: This is w here the received signal is present with frequency of 48-860 MHz. Its input impedance is 50 ohms. The receiving antenna can be connected to it using the BNC lead provided. An external 40dB attenuator provided can be used to reduce the incoming signal level by 100 times to avoid receiver overload.UP CONVERT ER INPUT 5-47 MHz: This is where the received signal of 5-47 MHz frequency has to be connected. Its input impedance is 50 ohms. The receiving antenna can be connected to it using the BNC lead provided. To receive these frequencies one needs to connect the input of RF IN BNC to OUTPUT BNC of this up converter . This up converter mixes the incoming signal with frequency of100 MHz with 0B gain so that it can be received in desired frequency range. An external 40dB attenuator provided can be used to reduce the incoming signal level by 100 times to avoid receiver over load.UPCONVERTER OUTPUT: This BNC is used to connect to the input of RF IN 48-860 MHz BNC.DOWN CONVERTER INPUT 861-2000M Hz: This is where the received signal has to be connected with frequency of 861-2000MHz. Its input impedance is 50 ohms. The receiving antenna can be connected to it using the BNC lead provided. To receive these frequencies one needs to connect the input of RF IN BNC to OUTPUT BNC of this down converter. This down converter mixes the incoming frequency w ith a PLL synthesized oscillator to output a fixed frequency of 479.5 MHz. An external 40dB attenuator provided can be used to reduce the incoming signal level by 100 times to avoid receiver overload.DOWN CONVERTER OUTPUT: This BNC is used to connect to the input of RF IN 48-860 MHz BNC.TRIGGER Transmitter: When the receiver is setup to listen in auto mode, this BNC input receives the trigger pulse from transmitter. Upon receipt of trigger pulse the receiver records the displayed RF level reading in dBuV into its memory and advances its frequency by the step selected. The idea is to operate the receiver and transmitter synchronously. For this the initially both Rx and Tx have to setupfor same frequency and the frequency step should also be same. This mode helps to plot the antenna frequency response, bandwidth, resonance, return loss plots etc. This is an open loop control unintelligent but reliable.TRIGGER Stepper : When the receiver is setup to listen in auto mode, this BNC input receives the trigger pulse from stepper controller. Upon receipt of trigger pulse the receiver records the displayed RF level reading in dBuV into its memory. Upon receipt of another pulse another current reading of RF level is recorded at another memory location. When the stepper motor rotates the antenna in angular step of say 5 degrees, it sends out 72 tr igger pulses on reaching each location. The receiver records 72 RF level readings corresponding to these 72 angular locations into its memory. An antenna polar plot is thus plotted. This is an open loop control unintelligent but reliable.RS232: This connector connects to PC via a null modem cable provided. This dumps the data stored in receiver memory to PC software. The memory consists of a matrix array of 3 X 1000 locations. The three columns are for memory location number , RF level in dBuV and Frequency respectively repeated in 1000 rows.VOLUME: This sets the volume level of the internal speaker.B.N.M.I.T Feb – June 2015 53


FIBER OPTIC COMMUNICATION KIT

TECHINCAL SPECIFICATIONSSimplex Fiber Optic cable:

Core Material PMMA(Polymethyl methacylate)Cladding Material Flourinated polymerFiber Structure Step index typeCore/Cladding Diameter 960 micron/1000 micronsCore Refractive Index 1.492Cladding Refractive index 1.405 to 1.417Numerical Aperture 0.5 (typical)Acceptance Angle 55 to 60 degreesAttenuation at 660 nm Typically 0.3 dB per meterJacket Material Polythene (black) , 2.2 mm OD

Fiber optic LEDMaterial GaAlAsWavelength Wavelength : 660 nmSpectral Line width 45 nmForward Voltage (Vf) 1.7 Volts at 10 mAReverse Voltage (Vr) 5 VoltsCapacitance 100 PF (approx.) at Vr = 0VForward Current(Max) 30 ma (average)Optical power typically into a 1 mm fiberTurn –on/ Turn off Time Better than 300nsTermination SMA (905), gold platedElectrical leads No sleeve is Cathode, Red sleeve is Anode

FO- Phototransistor:Peak Responsivity 850 nmSpectral Range 400 to 1100 nmDark current 100 na (max)Spectral Response : 50 ua/uw at 660 nm when coupled to a 1mm fiberCollector – Emitter 30 V (min)Emitter-collector 5 V (min)Vce (sat) 0.2 V (typical)Rise / Fall Time 5 us (typical)Connector SMA (905) gold platedElectrical leads Electrical leads : Black sleeve is Emitter

No sleeve is collector

Analog signals: 250 Hz, 500 Hz, 1 KHz sinusoidal signals. All amplitude variables from 0 to 5VDigital signals: 64 KHz, 32 KHz, 16 KHz & 8 KHz signalsDC: Adjustable over 0 to 5 Volts.Power supply: AC 230 V to DC 12 V, 5 V



Specifications of Optical fiber cables used in UE products.

Simplex cable with PMMA Fiber and SMA connections:The simplex cable with PMMA fiber finds application for short distance analogue and digital signal transmission. The step index fiber has a large area of cross section and a high numerical aperture, facilitating easy coupling with transmitting and receiving devices. The light is guided along a fiber of one millimeter approximately to distance of a few tens of meters. The other main applications of PMMA fibers are in sensors, light guides and displays.

Specification of simplex cable:1. Core Material: PMMA (Polymethyl methacylate)2. Cladding Material: Fluorinated polymer3. Fibre Structure: Step index type4. Core/Cladding Diameter: 960 micron/1000 microns5. Core Refractive Index: 1.4926. Cladding Refractive Index: 1.405 to 1.4177. Numerical Aperture: 0.5 (typical)8. Acceptance Angle: 55 to 60 degrees9. Attenuation (660nm): 0.3 dB/mtr10. Jacket Material: Polythene (black): 2.2 mm OD

Simplex Cable with GI Multimode Glass Fiber: The simplex style cable is of the tight buffer construction with a variety of glass fibers. It is reinforced with Kevlar and protective PVC jacket for robust lightweight applications.



Fibreoptics Hybrid Modules for Optical Power Measurement

The fibreoptics Hybrid Module, PHM20B comprises an encapsulated panel mountable device that receives optical power through a multimode step index plastic fibre at 660nm (or other multimode GI glass fibres such as 50/125, 62.5/125, 100/140, 200/230 etc) and converts it into an electrical voltage that is equivalent to the optical power measured in dBm. The FO module employs SMD technology to achieve a high degree of reliability and compactness. Teflon leads (5 in all) provide for easy integration with other circuitry. The device requires only a few external components to realize desired functions. The Industry standard fibreoptic SMA connector (optical terminal) provides for rugged and consistently repeatable operation. The power meter operates a single 6Vdc sources. The lead details and a typical application of PHM20B are given below.



Question Bank

1Design and demonstrate an ASK system to transmit digital data using a suitable carrier. Demodulate the above signal with the help of suitable circuit.

2Design and demonstrate the working of FSK with a suitable circuit for

_____ Hz and __ Hz carrier signals. Demodulate the above signal with the help of suitable circuit.

3Design and demonstrate the working of BPSK modulated signal for a given carrier signal of ______ Hz. Demodulate the BPSK signal to recover the digital data.

4 Design and demonstrate the working of TDM for PAM signals with _____ Hz and _____ Hz message signals. Also demultiplex the above message signals.

5 Conduct a suitable experiment using slotted line carriage to obtain the following for the given load. a) g and o b) VSWR

6 Conduct a suitable experiment using fiber optic trainer kit to determine the numerical aperture of the optical fiber.

7 Conduct a suitable experiment using fiber optic trainer kit to determine:

a) Attenuation loss b) Bending loss

8With the help of suitable circuit demonstrate the working of DPSK encoder and Decoder. The input stream and carrier frequency should be specified by the examiner

9 With the help of suitable circuit demonstrate the working of OPSK modulator and demodulator.

10 Conduct an experiment using fiber optic trainer kit to establish analog link with TDM.

11Conduct an experiment using fiber optic trainer kit to establish digital link



with TDM.

12 Conduct an experiment to obtain radiation pattern of micro strip patch antenna. Also calculate the directivity and gain of the antenna.

13 Conduct an experiment to obtain radiation pattern of micro strip dipole antenna. Also calculate the directivity and gain of the antenna.

14 Conduct an experiment to obtain radiation pattern of micro strip yagi antenna. Also calculate the directivity and gain of the antenna

15 Conduct an experiment on a given micro stip directional coupler to determine the following: a) Isolation Loss b) Coupling Loss

16 Conduct an experiment on a given micro stip power divider to determine the following: a) Isolation Loss b) Coupling Loss

17 Conduct an experiment to find the characteristics of micro strip ring resonator. Also calculate the dielectric constant of the substrate.


adv.commn lab manual

Documents