MN Lab Manual
MN Lab Manual
MN Lab Manual
FOR
10ECL67
VI Semester
B.N.M.Institute of Technology
Banashankari II Stage,
Bangalore 560 070
Feb May 2016
B.N.M.I.T
Dept. of ECE
IA Marks : 25
Total Hour : 42
Exam Marks: 50
LIST OF EXPERIMENTS
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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.
The Government presently sets the maximum exposure to microwave radiation at 10 mW/cm . If
2
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.
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CONTENTS
TOPIC
EXP.
NO
1.
2.
3.
4.
5.
6&7.
PAGE
N0
3
6
8
10
12
15
24
8.
26
9.
29
10.
31
11.
46
12.
48
13.
Pin Details
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Experiment No. 1
TIME DIVISION MULTIPLEXING
AIM: To design and demonstrate the working of TDM for band limited signals with
and
TDM signal.
Hz message signals with the help of suitable circuit. Demultiplex the above
Pin Diagram
INH
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
X
0
0
1
1
0
0
1
1
X
0
1
0
1
0
1
0
1
X
ON
Channel
0
1
2
3
4
5
6
7
NONE
PIN
NO
13
14
15
12
1
5
2
4
3
Channel
Mode MUX/DEMUX
Number
0
IN/OUT
1
IN/OUT
2
IN/OUT
3
IN/OUT
4
IN/OUT
5
IN/OUT
6
IN/OUT
7
IN/OUT
OUT/IN
6(INH) is kept Gnd
9,10 & 11 are select lines
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Features of CD4051
CD4051 is a 8-1 analog multiplexer & demultiplexer.
It has low ON resistance i.e. around 125.
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 m 1 (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)).
1
5. Design LPFs to get back m1(t) & m2(t). [Ex: cutoff frequency- fc = 2 RC , for fc=8KHz select
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.
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TDM waveforms:
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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
Modulator
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 4051
3. 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.
2.
3.
4.
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Design:
1. Fix the threshold at comparator input as 0.45V ( )
R2 V
2. Then R + R =0 . 45
1
2
3. With V=5v and R1=10K, select R2.
4. To design R and C values of envelope detector:
1
1
>> RC >>
fm
fc
or select 10RC= f
m
Observation:
1.
2.
3.
4.
Message signal
(Control signal m1 (t))
Carrier signal
(Sinusoidal c(t))
Modulated signal
Demodulated signal
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:
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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
Procedure
1. 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 C 1(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
(Control signal m1 (t))
Carrier signal
(Sinusoidal c(t))
Modulated signal
Demodulated signal
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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.
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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
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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:
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Experiment No 5
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 bench
2. 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
20mA
4. 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 maximum
2. Make Beam voltage minimum
3. Turn off HT
4. Turn off Mains
Block Diagram for frequency and attenuation (Probe connected to crystal detector of matched load)
Crystal
detector
Klystron
power
supply
CRO
Matched
Load
Reflex
klystron
oscillator
Isolator
Attenuator
Frequency
meter
Slotted
section with
carriage
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Tabular column
Repeller Voltage (Vr) in
volts
(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 (g)
(Probe to be connected to crystal detector of slotted carriage)
Klystron
power
supply
Reflex
klystron
oscillator
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Crystal
detector
Attenuator
Isolator
Frequency
meter
CRO /
VSWR
meter
Slotted
section with
carriage
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Experiment No. 6
End coupled
Edge coupled
Equipment description:
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Microwave source
Microwave 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 receiver
Receiver 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:
Source
Attenuator
(40 dB)
Device under
Test
Receiver
(Ring Resonator)
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/D, where C =velocity of light D= Mean diameter
of the ring resonator.
Tabular Column
Frequency
Direct Reading
(A)
Output power
(B-A)
1.0 GHz
1.1 GHz
1.2 GHz
1.3 GHz
1.9GHz
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Power in
DBm
fres
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
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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, equalphase 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:
Source
Attenuator
(40 dB)
Device under
Test
Receiver
(Power divider)
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3. 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 3 to the receiver and terminate port 2 with matched
load. Note down the power level (B) at Port 3.
4. Repeat the above steps for different frequencies and tabulate the readings.
Tabular column for power division:
Frequenc
y
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.
2. Insert the device under test (Power divider) between source and receiver along with attenuator such
that the port 2 is connected to the source, port 3 to the receiver and terminate port 1 with matched
load. Note down the power level (B) at Port 3.
3. Insert the device under test (Power divider) between source and receiver along with attenuator such
that the port 2 is connected to the source, port 1 to the receiver and terminate port 3 with matched
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:
Input given at Port 2
Frequency
Direct
power
reading (A)
Power
reading (B)
at Port 3,
port 1
Matched
Load
(Isolation)
Power reading
(C) at Port 1,
Port 3
Matched Load
(Power
division)
1500MHz
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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 couplers
Waveguide 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.
Definitions
Insertion 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 + Directivity
For Forward Direction:
For Reverse Direction:
Port 1
Input
Port 2
Direct
Port 1
Direct
Port 2
Input
Port 3
Coupled
Port 4
Isolated
Port 3
Isolated
Port 4
Coupled
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Block diagram:
Microwave
Source
Attenuator
(40 dB)
Microwave
Receiver
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
P1
Forward Direction
P2
P3
P4
Isolated
P2
Reverse Direction
P1
P4
P3
Isolated
1400 MHz
1500 MHz
Result:
Insertion loss
= P1 - P2 =dB
Coupling Factor
= P2- P3 =. dB
Isolation (I)
= P1 - P4 =..dB
Directivity (D)
= P3 - P4=dB
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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
Analog Switch
Digital Information
Di-Bit Generator
QPSK-Demodulator
Modulated Signal
DeModulated Signal
Analog switch
Waveshaping Ckt
Di-bit serializer
MSB
Phase(in degrees)
45
315
225
135
Dibit
Phase Change
00
01
11
10
0
90
180
270
LSB
Procedure:
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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
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QPSK waveform
Dibits
Phases
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11
11
01
180
00
0
180
00
0
900
01
00
11
11
00
900
180
180
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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
observed 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.
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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.
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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
For a step index fiber, as in the present case, the numerical aperture is given by
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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)
1.
10mm
2.
25 mm
B.N.M.I.T
NA
(degrees)
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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.
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SL
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.)
Measured Output Power
for 6m Cable Pout1
Connector Loss =
Pout2 - Pout1
1.
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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
cable.
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 cable
Pout2 - Pout1
Propagatio
n Loss on
additional
4m of
cable
Pout3 - Pout1
1.
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
Bending Loss
Output Power
with 1 Bend
for 1m Cable
Pout2 - Pout1
with 5 Bends of
10cm diameter.
Pout3
Bending Loss
with 5 Bend
Pout3 - Pout1
1.
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Direct
Reading
P1(dBm)
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Power Reading
With air gap of
0.7mm
P2(dBm)
Power Reading
With air gap of
1.4mm
P3(dBm)
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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
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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
SCLCK
DIFFERENTIAL
ENCODER
CARRIER
MODULATOR
MODOUT
NRZ-L DATA
DATA
MOD IN
BPSK
DEMODULATOR
DELAY
DECISION
DEVICE /
COMPARATOR
B(t-Tb)
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DELAY
Tb
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PROCEDURE:
1.
2.
3.
4.
5.
6.
7.
8.
9.
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EXPERIMENT NO. 11
Microstrip Antennas
OBJECTIVE: 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.
Dipole Antenna
Patch Antenna
Yagi Antenna
43
Block diagram:
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Dept. of ECE
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
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1. Dipole antenna
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2. Patch antenna
3. Yagi antenna
Receiver
H plane Angle
Reading(dBm)
(deg)
0
10
20
------340
350
0
10
20
------340
350
Receiver Reading(dBm)
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1. Mark the -3dB points on the plot and find the angle between the -3dB points to get the Azimuth
beam width HP from Horizontal Plane and Elevation beam width HP 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) / HP *HP.)
Directivity of the antenna (D dB) = 10logD dBi where dBi = decibels over isotropic.
Annexure I
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Datasheets of ICs
UA741
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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.
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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 of
100 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 setup
for 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.
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PMMA(Polymethyl methacylate)
Flourinated polymer
Step index type
960 micron/1000 microns
1.492
1.405 to 1.417
0.5 (typical)
55 to 60 degrees
Typically 0.3 dB per meter
Polythene (black) , 2.2 mm OD
GaAlAs
Wavelength : 660 nm
45 nm
1.7 Volts at 10 mA
5 Volts
100 PF (approx.) at Vr = 0V
30 ma (average)
typically into a 1 mm fiber
Better than 300ns
SMA (905), gold plated
No sleeve is Cathode, Red sleeve is Anode
FO- Phototransistor:
Peak Responsivity
Spectral Range
Dark current
Spectral Response
Collector Emitter
Emitter-collector
Vce (sat)
Rise / Fall Time
Connector
Electrical leads
850 nm
400 to 1100 nm
100 na (max)
: 50 ua/uw at 660 nm when coupled to a 1mm fiber
30 V (min)
5 V (min)
0.2 V (typical)
5 us (typical)
SMA (905) gold plated
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 5V
Digital signals: 64 KHz, 32 KHz, 16 KHz & 8 KHz signals
DC: Adjustable over 0 to 5 Volts.
Power supply: AC 230 V to DC 12 V, 5 V
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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.
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Question Bank
1
Design and demonstrate an ASK system to transmit digital data using a
suitable carrier. Demodulate the above signal with the help of suitable
circuit.
Design and demonstrate the working of FSK with a suitable circuit for
2
Design and demonstrate the working of TDM for PAM signals with _____
Hz and _____ Hz message signals. Also demultiplex the above message
signals.
b) VSWR
Conduct a suitable experiment using fiber optic trainer kit to determine the
numerical aperture of the optical fiber.
Conduct a suitable experiment using fiber optic trainer kit to determine:
7
a) Attenuation loss b) Bending loss
With the help of suitable circuit demonstrate the working of DPSK
8
encoder and Decoder. The input stream and carrier frequency should be
specified by the examiner
10
Conduct an experiment using fiber optic trainer kit to establish analog link
with TDM.
Conduct an experiment using fiber optic trainer kit to establish digital link
11
with TDM.
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13
14
15
16
b) Coupling Loss
17
a) Isolation Loss
a) Isolation Loss
b) Coupling Loss
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