58808269 microwave-manual

RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
RAJALAKSHMI ENGINEERING COLLEGE
Thandalam, Chennai – 602 105.
Department of Electronics and Communication Engineering
EC 2405 OPTICAL AND MICROWAVE
LAB MANUAL
(VII SEM ECE)
1
Prepared by M.Sathish and M.Revathi

SYLLABUS
EC 2405 - OPTICAL & MICROWAVE LAB
MICROWAVE EXPERIMENTS:
1. Reflex klystron – Mode characteristics.
2. Gunn Diode – Characteristics.
3. VSWR, Frequency and Wave Length Measurement.
4. Directional Coupler – Directivity and coupling co – efficient – S – Parameter
Measurement.
5. Isolator and Circulator – S – Parameter Measurement.
6. Attenuation and Power Measurement.
7. S – Matrix Characterization of E – Plane T, H – Plane T and Magic tee.
8. Radiation Pattern of Antennas.
9. Antenna Gain Measurement.
OPTICAL EXPERIMENTS:
1. DC Characteristics of LED and PIN Photo Diode.
2. Mode Characteristics of Fibers.
3. Measurement of Connector and Bending Losses.
4. Fiber Optic Analog and Digital Link.
5. Numerical Aperture Determination for Fibers.
6. Attenuation Measurement in Fibers.

Expt: No: 1 REFLEX KLYSTRON CHARACTERISTICS
AIM:
To study mode characteristics of reflex klystron and hence to determine mode number,
transmit time, electronic tuning ranges (ETR) and electronic tuning sensitivity (ETS).
EQUIPMENT REQUIRED:
Klystron tube, klystron power supply, Isolator, Frequency meter, Variable attenuator,
Detector mount, V.S.W.R Meter, C.R.O.
PROCEDURE:
Mode studies:
1. Connect the components and equipments as shown in fig. A
2. Keep the control knob of klystron power supply as below:
Mode switch : CW
Beam voltage knob : Fully anti-clockwise
Repeller voltage knob : Fully clockwise
Meter switch : Cathode voltage position
3. Rotate the frequency meter at one side.
4. Switch on the klystron power supply, V.S.W.R meter and cooling fan for the klystron
tube. Wait for 1-2 minutes for the klystron to respond.
5. Cathode voltage knob at minimum position gives a beam voltage of 235V. Observe beam
current on the meter by changing meter switch to beam current position. “The beam
current should not be more than 30mA”.
6. Now change the meter switch to repeller voltage position.
7. Select proper range for the power meter so that power output of maximum mode will not
exceed the meter range.
8. Decreasing the reflector voltage, record output power and frequency.
9. To measure frequency, switch the Mode-switch of klystron to AM mode and observe
output on CRO display. By matching the detector with tuning posts adjust for maximum
output. Use AM amplitude, frequency controls and controls on Oscilloscope front panel
try to get clear display on C.R.O. By rotating the frequency meter, observe for dip in the
output and note the corresponding frequency.
10. Plot power/relative frequency versus repeller voltage to get mode curves.
11. Compute various parameters from the graph.
Mechanical and Electronic Tuning:
Mechanical tuning depends on changing the width of cavity i.e. the effective I
capacitance and thus the resonant frequency of the klystron changes. The power output remains
same with tuning.
Electronic tuning refers to change in repeller voltage causing a change in output
frequency. However, the power output also changes. A measure of electronic tuning is given by
‘Electronic Tuning Sensitivity (ETS)’. This can be determined by taking the slope of the
frequency characteristic of the modes.
3

EXPERIMENTAL SETUP:
Fig.(A) Microwave bench setup for study of klystron modes
OBSERVATIONS:
S.No. Repeller Voltage
(Volts)
Power Output
(mW)
Wave meter reading
Frequency (GHz)
23/4
13/4
33/4
Output Power 43/4
(mW) 3/4
Reflector Voltage
f0+∆f
Relative
Frequency
f0
f0+∆f
Reflector Voltage
Mode Characteristics of Reflex Klystron
CALCULATIONS:
1. Knowing the maximum voltage of two adjacent modes, mode number can be computed
using the relation
Klystron
Power
Supply
Reflex
Klystron
Isolator
Frequency
Meter
Detector
Mount C.R.O
V.S.W.R.
Meter

N2/N1 = V1/V2 = (n+1+3/4)/(n+3/4)
Where N1, N2 -------- mode numbers
V1, V2-------- repeller voltages
2. Knowing mode number, transit time of each mode may be calculated from
T = (n+3/4)/f0 :::> t1 = N1/f01, t2 = N2/f02
3. Calculate electronic tuning range, i.e., the frequency band from one end of the mode to
another.
4. ETS may be calculated using the relation
ETS = (f2 – f1) / (V2 – V1)
Where f1, f2 being half power frequencies in GHz, and V2 and V1 are
Corresponding repeller voltages for a particular mode.
RESULT:
Thus the mode characteristics of reflex klystron, mode number, transit time, electronic
tuning range (ETR) and electronic tuning sensitivity (ETS) have been determined.
EXPERIMENTAL SETUP:
5

Fig. (A) Microwave bench setup for study of Gunn Oscillator Characteristics.
MODEL GRAPH
Current Threshold Voltage
I
V0 Voltage
Current Voltage Characteristics of Gunn Oscillator
Expt: No: 2 GUNN DIODE - CHARACTERISTICS
AIM:
Gunn
Power
Supply
Gunn
Oscillator
PIN
modulator
Isolator
Variable
attenuator
Detector
Mount
V.S.W.R
Meter
Slotted
section

To study I-V Characteristics of Gunn diode and depth of modulation of PIN Diode.
EQUIPMENT REQUIRED:
Gunn power supply, Gunn oscillator, PIN modulator, Isolator, Frequency meter, Variable
attenuator, Detector mount, Slotted section, V.S.W.R Meter.
PROCEDURE:
1. Set the components and equipments as shown in figure above.
2. Initially set the variable attenuator for maximum attenuation.
3. Keep the control knob of Gunn power supply as below:
Meter switch : ‘OFF’
Gunn bias knob : Fully anti – clockwise
Pin bias knob/ Mod Amplitude : mid position
Pin mod frequency : mid position
4. Keep the control knob of VSWR meter as below:
Meter switch : normal
Input switch : crystal low impedance/200k
Range db switch : 50db
Gain control knob : Fully clockwise
5. Set the micrometer of Gunn oscillator between 5 – 7 mm for required frequency of
operation.
6. ‘ON’ the Gunn power supply, VSWR meter and cooling fan.
7. Keep the mode switch of Gunn power supply to square wave/Internal Modulation.
8. Turn the meter knob to voltage position; apply Gunn bias voltage around 5 volts. Now
change the meter switch to current position and note that, as Gunn bias voltage is varied
current starts decreasing. This indicates negative resistance characteristic of Gunn diode.
Apply the voltage such that the device is in the middle of the negative resistance region.
9. Connect detector output to SWR meter.
10. Adjust the square wave modulation frequency to approximately 1 KHz.
11. Change the meter range if no deflection is observed.
12. Keep the slotted line probe at position where maximum deflection in meter is observed.
13. Adjust the attenuator setting; gain control knob on VSWR meter and tune the detector
plunger for the pointer to indicate VSWR1.
14. Move detector probe along the slotted line and note position of probe where pointer
comes to extreme left position, which is first minimum. In order to know exact position
of minimum note the positions of equal response points on either side of the minimum
and then the midpoint of those positions will give position of minimum. The same way
note next minimum positions.
15. Repeat the above procedure for different settings of micrometer.
OBSERVATIONS:
7

S.No. Gunn Bias Voltage
(V)
Gunn Diode Current
(I)
Depth of Modulation of PIN Diode:
1. Apply Gunn Bias Voltage slowly so that panel meter of Gunn power supply reads 8V.
2. Tune the PIN modulator bias voltage and frequency knob for maximum output on the
oscilloscope.
3. Coincide the bottom of square wave oscilloscope to some reference level and note down
the micrometer reading of variable attenuator.
4. Now with help of variable attenuator coincide the top of square wave to same reference
level and note down the micrometer reading.
5. Connect VSWR to detector mount and note down the dB reading in VSWR Meter for
both the micrometer reading the variable attenuator.
6. The difference of both dB reading of VSWR meter gives the modulation depth of PIN
modulator.

Note: After tuning the Gunn source, the procedure for VSWR & Impedance measurement
depth of PIN modulator.
RESULT: Thus the I-V Characteristics of Gunn Diode and depth of modulation of PIN Diode
have been determined.
EXPERIMENTAL SETUP:
9
Klystron
Mount +
Klystron
2k25/723A/B
Isolator
Variable
Attenuator
Frequency
Meter
Detector
Mount
V.S.W.R.
Meter
Slotted
Line
Klystron
Power
Supply
Tunable
Probe

Fig.3 Set up for Frequency Measurement
For dominate mode TE10 mode rectangular wave guide the following relation is in use:
1 / λo2
= 1 / λg2
+ 1 / λc2
Where λo is free space wave length
λg is guide wave length
λc is cut off wave length
For TE10 mode λc = 2a where ‘a’ is broad dimension of wave guide
Note: From the free space wavelength calculate the frequency
Expt: No: 3 (a) FREQUENCY MEASUREMENT
AIM:
To examine the frequency characteristics of klystrons and also to become familiar with
typical microwave frequency measurements, in addition, to study 1000 cps amplitude
modulation of klystrons.
EQUIPMENT REQUIRED:
Klystron power supply, klystron Tube 2k25, klystron mount, Isolator, Frequency meter,
Variable attenuator, Detector mount, Wave guide stands, V.S.W.R Meter, BNC Cable etc.,

PROCEDURE:
Set up the components & equipments as shown in fig.3
Set up variable attenuator at minimum attenuation position.
Keep control knobs of vswr meter as given below:
Range : 50 db
Input switch : Crystal low impedance
Meter switch : Normal position
Gain (Coarse & fine) : Mid position
Keep control knobs of klystron power supply as given below:
Beam Voltage : Off
Mod-switch : AM
Beam voltage switch : Full anticlockwise
Reflector voltage : Full clockwise
Am amplitude knob : Full clockwise
Am frequency knob : Mid position
Switch on the klystron power supply, vswr meter and cooling fan switch.
Switch on the beam voltage switch and set beam voltage at 300V with beam voltage knob
Set the reflector voltage to get some deflection in vswr meter.
Maximize the deflection with AM amplitude and frequency control knob of supply
Tune the plunger of mount for maximum deflection
Tune the reflector voltage knob for maximum deflection
Tune the probe for maximum deflection in vswr meter
Tune the frequency meter to get a ‘dip’ on the vswr meter and note the frequency from frequency
meter.
Replace the termination & movable short and de tune the frequency meter
Move the probe along with the slotted section. The deflection in vswr meter will vary. Move the
probe to a minimum deflection position to get accurate reading if necessary the vswr range db to
higher position. Note the probe position. Move the probe to next minimum position and note
again.
Calculate the guide wave length as twice the distance between two minimum position.
Measure the wave guide inner broad dimension ‘a’ which will be around 22.85 to 22.86 mm for
X band
OBSERVATIONS:
S.No. Repeller Voltage
(Volts)
Frequency Meter
Reading(GHz)
Frequency
F = C√ 1 / λg2
+ 1 / λc2
11
Mode
Frequency meter ‘DIP’

Calculate the frequency, F = C/λ, where C = Velocity of light = √ 1 / λg2
+ 1 / λc2
Verify with frequency obtained by frequency meter
Where, C = 3 x 108
meter per second
= 3 x 1010
cms per second
Note: In microwave communication the medium of propagation is usually the free space
surrounding the earth. In singles frequency these variations are periodic and sinusoidal and
therefore can be considered in terms of frequency in cycle/second.

RESULT: Thus the frequency characteristics of klystron have been determined.
EXPERIMENTAL SETUP:
Fig.5 Set up for Measuring Low, Medium & High VSWR
13
Klystron
Mount +
Klystron
2k25/723A/B
Isolator
Variable
Attenuator
Frequency
Meter
Matched
Termination
Probe
Slotted
Line
Klystron
Power
Supply
V.S.W.R
Meter

CALCULATION:
LR = 20 log 10 Ei/Er = 20 log 10 1/(R)
= 20 log 10 vswr + 1/vswr-1.
VSWR = Emax / Emin
= Ei + Er / Ei – Er, -------- (1)
Where Ei = incident voltage and Er = reflected voltage
= 1 + reflection co-efficient / 1 – reflection co-efficient
Reflection co-efficient ( R) the size of reflection
R = Er/Ei = Zl – Z0 / Zl + Z0 -------- (2)
Where Zl is load impedance, Z0 is characteristic impedance
The above equation following equations
R = (vswr – 1) / (vswr + 1) -------- (3)
Note: the reflection co-efficient is expressed as a dimension less, the ratio of the voltage reflected
to the voltage incident. It must be noted that reflection co-efficient must lie between zero and
one. If reflection co-efficient is zero there is no reflection, if reflection co-efficient is one, there
is total reflection. The value of vswr is determined by the reflection co-efficient as indication in
equation – 1

Expt: No: 3 (b) MEASURING VSWR
AIM:
To become familiar with the basic technique for measuring voltage standing wave ratio.
EQUIPMENT REQUIRED:
Klystron power supply, klystron Tube, klystron mount, Isolator, Frequency meter,
Variable attenuator, Slotted section, Tunable probe, Wave guide stands, Movable short load,
BNC cable, V.S.W.R Meter.
PROCEDURE:
Set the equipments as figure – 5.
Keep variable attenuator in the minimum attenuation position.
Keep the control knob of vswr meter as below.
Range db : 40 db to 50 db
Input switch : Low impedance
Gain : Mid position
Keep control knobs of klystron power supply as given below:
Beam Voltage : Off
Mod-switch : AM
Beam voltage knob : Full anticlockwise
Reflector voltage knob : Full clockwise
Am amplitude knob : Full clockwise
Am frequency & amplitude knob : Mid position
Switch on the klystron power supply, vswr meter and cooling fan.
Switch on the beam voltage switch and set beam voltage at 300V
Rotate the reflector voltage knob to get deflection in vswr meter.
Tune the output by tuning the reflector voltage, amplitude and frequency of am modulation.
Tune plunger of klystron mount and probe for maximum deflection in vswr meter.
If required change the range db switch variable attenuator position and gain control knob to get
deflection in the scale of vswr meter.
As we move probe along the slotted line, the deflection will change.
(1) Measurement of low and medium VSWR
Move the probe along the slotted line to get maximum deflection in vswr meter.
Adjust the vswr meter gain control knob or variable attenuator until the meter indicates 1.0 on
normal vswr scale.
Keep all the control knobs as it is, move the probe to next minimum position. Read the vswr on
scale.
Repeat the above step for change of SS tuner probe depth and record the corresponding SWR.
If the vswr is between 3.2 and 10, change the range db to next higher position and read the vswr
on second vswr scale of 3 to 10.
(2) Measurement of high VSWR
15

Set the depth of SS tuner slightly more for maximum vswr.
Move the probe along with slotted line until a minimum is indicated.
Adjust the vswr gain control knob and variable attenuator to obtain a reading of 3 db in the
normal db scale ( 0 – 10db) of vswr meter.
Move the probe to the left on slotted line until full scale deflection is obtained on 0 -10 db scale.
Note and record the probe position on slotted line let it be d1.
Repeat the step 3 and then move the probe right along the slotted line until full scale deflection is
obtained on 0 – 10db normal db let it be d2.
Replace the SS tuner and termination by movable short.
Measure the distance between two successive minima positions of the probe > twice this distance
is guide wave length.
Compute vswr from the following equation.
VSWR λg / π (d1 – d2) = λg / π (Δx)
Where λg is the guide wavelength, d1 and d2 are locatimes of double minimum points.
Note: this method overcomes this effect of probe loading, since the probe is loading always
around a voltage minimum however it does not overcome the effect of detector characteristics.
For high values of VSWR, the twica – minimum method should be used. In this method the
probe is moved to a point where the power is twice the minimum. This position is denoted d – 1.
Probe is moved to the twice power point on the other side of the minimum. The position
designated as d – 2. The VSWR may be found by the relationship.
VSWR λg / π(d1 – d2)
The units of wavelength (λg) and distance are same.
RESULT:
Thus the VSWR have been measured.

Expt: No: 4 PROPERTIES OF DIRECTIONAL COUPLER
AIM:
To measure coupling factor, directivity and insertion loss of a directional coupler.
EQUIPMENT REQUIRED:
Reflex Klystron, klystron power supply, Isolator, Frequency meter, Variable attenuator
(or Gunn Power Supply, Gunn oscillator, Isolator, Pin Modulator), Termination, crystal detector,
V.S.W.R Meter, Directional coupler.
PROCEDURE:
1. Set up the equipment as shown in fig. without the directional coupler i.e. directly connect
crystal detector with VSWR meter in order to measure input after attenuator.
2. Set the variable attenuator at maximum position.
3. Keep the control knobs of VSWR meter as below
Range db - 50 db position
Input switch - Crystal low impedance / 200k
Meter switch - Normal position
Gain (coarse & fine) - Mid position
4. Keep the control knobs of klystron power supply as below:
Mod-switch - AM
Beam voltage knob - Fully anti-clockwise
Reflector voltage - Fully clockwise
AM-Amplitude knob - around fully clockwise
AM-Frequency knob - around mid position
5. ‘ON’ the klystron power supply, VSWR meter and cooling fan.
6. Turn the meter switch of power supply to beam voltage position and beam voltage at
300Volt with the help of beam voltage knob.
7. Adjust the reflector voltage to set klystron for maximum mode of operation. Get some
deflection in VSWR meter.
8. Maximize the deflection with AM amplitude and frequency control knob of power supply
and set some reference reading in VSWR meter. Note this attenuator setting as (AI) dB.
9. Now insert directional coupler as shown in fig.b. Feed the power through port 1 and
measure output at port 2 by terminating port 3 using matched termination.
10. Reduce the attenuation to get the reference reading obtained in step 8 on VSWR meter.
Note down the attenuator setting as (A2) dB.
11. Now terminate port 2 with matched load and measure output at port 3. Reduce the
attenuation to get reference reading obtained in step 8. Note the attenuator setting as (A3)
dB.
12. Reverse the directional coupler and feed the power through port 2 and measure the output
at port 3. Let the attenuator setting for this reading be (A4) dB.
13. Calculate directivity, coupling, isolation and insertion loss.
14. Repeat the experiment at other frequencies to obtain coupling characteristics over the
band of interest.
RESULT:
17

Thus the coupling factor, directivity and insertion loss of a directional coupler have been
measured.
EXPERIMENTAL SETUP:
Fig. (B)
To measure coupling and directivity one of the ports of the coupler is terminated with a matched
load.
Coupling (dB) = -10 log P3 / P1
Isolation (dB) = -10 log P4 / P1
Directivity (dB) = -10 log P4 / P3
Insertion loss (dB) = -10 log P2 / P1
Thus the coupling is a measure of how strongly the primary and secondary arms are coupled to
each other and the directivity is a measure of how good separation between the incident and
reflected waves is accomplished.
OBSERVATIONS
Freq (GHz) A1dB A2dB A3dB A4dB
CALCULATIONS:
Coupling (dB) A1 – A3dB
Directivity (dB) A3 – A4dB
Isolation (dB) A1 – A4dB
Insertion loss (dB) A1 – A2dB
Klystron
Power
Supply
Reflex
Klystron
Isolator
Frequency
Meter
Attenuator Directional
Coupler
V.S.W.R
Meter
Matched
load
Crystal
Detector

Expt: No: 5 ISOLATOR & CIRCULATOR CHARACTERISTICS
AIM:
To study operation of ferrite circulator, isolator and hence measure insertion loss and
isolation offered by these devices.
EQUIPMENT REQUIRED:
Klystron power supply, klystron mount, Variable attenuator, Matched termination,
crystal detector, V.S.W.R Meter, isolator, circulator.
PROCEDURE:
1. Setup the equipment as shown in figure without the ferrite device i.e., directly connect
detector with vswr meter in order to measure input.
2. Set the variable attenuator at maximum position.
3. Keep the control knob of klystron power supply as below:
Mode Switch : AM
Beam Voltage Knob : Fully Anti Clockwise
Repeller Voltage Knob : Fully Clockwise
Meter Switch : Cathode Voltage Position
4. Keep the control knobs of VSWR meter as below:
Range db : 50 db position
Input switch : Crystal low impedance
Gain (Coarse and fine) : Mid position
5. ‘ON’ the klystron power supply, VSWR Meter and cooling fan.
6. Set some reference reading in VSWR meter by adjusting the variable attenuator.
Note this attenuator setting as (A1) db.
Circulator
1. Carefully remove the detector setup and insert the circulator as in the set-up, with power
fed through port 1.
2. Measure output at port 2 with port 3 terminated in matched load.
3. Reduce the attenuation to get the reference reading obtained in step 6.
i. Note down the attenuator setting as (A2) db.
4. Determine insertion loss or forward loss in decibels by noting the change in attenuator
setting in order to get reference reading in VSWR meter.
5. Interchange the positions of detector set-up and matched load between ports 2 and 3.
Adjust the attenuator setting to get reference reading on SWR meter. Note the attenuator
setting as (A3) db. Determine the isolation (or attenuation) in db by noting the change in
attenuator setting (with reference reading in VSWR meter).
Isolator
1. Now insert isolator in place of circulator with input power fed to port 1.
2. Measure output at port 2, adjust the attenuator to get reference reading in indicating
meter. Note this attenuator setting as A12 db.
3. Inter change the ports of isolator and adjust the attenuator to get reference reading
indicating meter. Note the attenuator setting as A21 db.
19

RESULT: Thus the operation of ferrite circulator, isolator are studied and measured their
insertion loss and isolation.
EXPERIMENTAL SETUP:
Three port circulator
OBSERVATIONS:
CIRCULATOR
A1 dB A2 dB A3 dB
ISOLATOR
A1 dB A12 dB A21 dB
CALCULATIONS
Circulator
Insertion loss dB = A1 – A2 dB
Isolation dB = A1 – A4 dB
Isolator
Insertion loss dB = A1 – A12 dB
Isolation dB = A1 – A21 dB
Klystron
Power
Supply
Klystron
Mount
Isolator
Attenuator Isolator
Circulator
Detector
Mount
V.S.W.R
Meter
Matched
Termination
Port 3 (Isolated)
Port 1(Input)
Port 2(coupled)

Expt: No: 6 a. ATTENUATOR CHARACTERISTICS
AIM:
To study the attenuation characteristics of a variable attenuator.
EQUIPMENT REQUIRED:
Klystron power supply, klystron Tube 2k25, klystron mount, Isolator, Frequency meter,
Variable attenuator, Detector mount, Wave guide stands, V.S.W.R Meter, BNC Cable etc.,
PROCEDURE:
1. Set the components and equipments as shown in figure above.
2. Initially set the variable attenuator for maximum attenuation.
3. Terminate the receiving end with unknown load.
4. Keep the control knob of klystron power supply.
Beam voltage - off
Mod-switch - AM
Beam voltage knob - Full anti clockwise
Reflector voltage knob - Full clockwise
Am-amplitude knob - Full clockwise
Am frequency & amplitude knob - Mid position
Switch on the klystron power supply, vswr meter & cooling fan.
Switch on the beam voltage switch and set beam voltage at 300v.
Rotate the reflector voltage knob to get deflection in vswr meter.
Tune the output by tuning the reflector voltage, amplitude and frequency of am
modulation.
Tune plunger of klystron mount and probe for maximum deflection in vswr meter.
5. Keep the control knob of vswr meter as below:
i. Switch : normal
ii. Input switch : Low impedance
iii. Range db switch : 40 db
iv. Gain control knob : Fully clockwise
6. Connect detector output to SWR meter.
7. Adjust the square wave modulation frequency to approximately 1 KHz.
8. Tune the detector by adjusting short plunger for maximum meter deflection.
9. Move the probe along slotted line, adjust it at standing wave minimum. Record the probe
position as X1, (this is the position of reference minimum) and next minimum position as
X2.
10. Replace load by short circuit termination and move the probe carriage to new standing
wave minimum and record the probe position as Xs.(This is known as position of
reference plane.
11. Find the shift minima (Xs – X2 or Xs – X1). It will be positive if minimum is shifted
towards load (i.e., for inductive load) and negative if minimum is shifted towards
generator (for capacitive load). Shift in minimum for different loads can be easily known
from the standing wave patterns given below.
12. Convert the shift in wavelength units, i.e., (Xs – X1) / l. Wavelengths.
13. Position on minimum can be known more accurately if it is taken as midpoint of
positions of equal responses on either side of minimum.
21

RESULT: Thus the attenuation characteristics of a variable attenuator are studied.
EXPERIMENTAL SETUP:
Setup for Attenuator Characteristics
TABULAR COLUMN
Micrometer Reading : 11.79mm
Frequency 9.97 GHz : 9.97GHz
OBSERVATIONS:
S.No. Screw Gauge Reading
(mm)
Attenuation in Decibels
Klystron
Mount +
Klystron
2k25/723A/B
Isolator
Variable
Attenuator
Frequency
Meter
Detector
Mount
V.S.W.R.
Meter
Slotted
Line
Klystron
Power
Supply

Expt: No: 6B STUDY OF POWER DIVISION IN MAGIC TEE
AIM:
To measure isolation between E and H arms of the magic tee & Demonstrate 3dB power
division in the side arm of the magic tee.
EQUIPMENT REQUIRED:
Klystron power supply, klystron mount, Isolator, Attenuator, Frequency meter, V.S.W.R
Meter, magic tee and matched terminations.
PROCEDURE:
General:
1. Setup the equipment as shown in fig 9a
2. Keep the control knobs of klystron power supply as below.
Mode switch : AM
Beam Voltage Knob : Fully Anticlockwise
Repeller Voltage Knob : Fully Clockwise
Meter Switch : Cathode Voltage Position
3. Measurement or isolation between E and H arms.
i. Set the attenuator around 20dB. Let this setting be (A1) dB.
ii. Achieve a state reference reading on the SWR meter, preferably in 40dB
range of the SWR meter.
iii. Disconnect and setup as shown in fig.9b
iv. Reduce the attenuation till the SWR meter reads the value obtained in step ii.
Note the attenuation setting (A2) dB. The difference in the attenuator settings
(A1 – A2) dB gives the isolation in dB
4. Experimental setup for demonstrating the 3dB power division in the collinear arms.
i. Now the power input be either at E or H arms.
ii. Set the attenuator to get reference reading on the SWR meter without the
component under test. Note the attenuator setting (A1) dB.
iii. Connect the component under test (Magic tee)
iv. Reduce the attenuation to get the reference reading obtained in step ii.
v. Note down the attenuator setting (A2) dB.
The difference in the attenuator settings gives the ratio of the power coupled to the collinear to
that in the main arm, in dB. This value should be around 3 dB.
Result:
Thus the isolation between E and H arms of the magic tee is measured and power division in the
side arm of the magic tee is demonstrated.
23

EXPERIMENTAL SETUP:
Fig.9a. For Input Power measurement
Fig.9b. For coupled/isolated Power measurement
Klystron
Power
Supply
Klystron
Mount
Isolator
Variable
Attenuator Tunable crystal
Detector mount
V.S.W.R
Meter
Klystron
Power
Supply
Klystron
Mount
Isolator
Variable
Attenuator
Tunable crystal
Detector mount
V.S.W.R
Meter
Magic
Tee

Isolation between E and H arms
If the power flowing into E arm is taken as PE and power flowing out of H-arm as PH then
Isolation (dB) = -10 log10 PH/PE
This assumes that both the collinear arms are match terminated.
Power division
The power fed in either the E or H arm should divide itself equally in both the side arms, when
the opposite port is match terminated. If we designate the power entering the E arm as PE and
power in side arms as PC1 and PC2 then the ratio of the power coupled in side arms to that entering
in the E-arm is given by the relation.
Coupling (dB) = -10 log10 PC1/PH = -10 log10 PC2/PH
OBSERVATION:
ISOLATION MEASUREMENT
Attenuator setting when measuring
input to E-arm A1 dB
power to H-arm A2 dB
Measurement of power division
input to E/H arm A1 dB
power at collinear to arms A2 dB
Calculations:
Isolation between E and H arm (dB) = (A1 – A2) dB
Coupling between collinear arms and E/H arms (dB) = (A1 – A2) dB
EXPERIMENTAL SETUP FOR HORN ANTENNA:
25

TABULAR COLUMN
0 in degrees Power received in decibels
clockwise
Power received
anticlockwise
0
10
20
30
40
50
60
70
80
90
H PLANE
0
10
20
30
40
50
60
70
80
90
E PLANE
MODEL GRAPH:
Expt: No: 8 HORN ANTENNA CHARACTERISTICS
Klystron Power Supply
Reflex Klystron
Tube Mount
Isolator
Attenuator Frequency
Meter
V.S.W.R
MeterCrystal
Detector
Transmitting Horn Receiving Horn
700 7060 6050 5040 4030 3020 2010 10

AIM:
To obtain the radiation pattern of an Horn Antenna
EQUIPMENT REQUIRED:
Klystron power supply, klystron mount, Isolator, Variable Attenuator, Frequency meter,
V.S.W.R Meter, Coupling probes, Two Pyramidal Horn, Radiation Pattern Turn Table.
PROCEDURE:
1. Switch on the power supply keeping the switch the front panel in beam OFF position.
2. Wait for few minutes and then change the switch to Beam On position.
3. Set the Beam voltage to 300V by varying beam voltage control knob.
4. Check the beam current whether it is less than 30mA.
5. Set the variable attenuator to max attenuation level.
6. Change the modulating voltage control knob from min to max range and find the
modulating voltage for which maximum deflection in VSWR meter.
7. Adjust the modulating frequency control knob from 0 Hz to 1 KHz until to get more
deflection in on VSWR meter. If we are getting 2 or 3 maximum deflections choose the
least one.
8. Now change the repeller voltage and measure power in db from VSWR meter.
9. For measurement of power in VSWR meter we have to detune the frequency meter every
time.
10. Mount the Horn antenna one to microwave bench and other towards the VSWR end.
11. Adjusts the two horn antennas to be exactly in line with each other i.e. perfectly aligned
condition i.e. angular difference is 0.
12. Now note the deflection in the VSWR meter.
13. Now rotate the Horn antenna HZ through 100. The power output increases in the VSWR
meter. Note the reading.
14. Similar procedure is carried out to get readings in steps of 10 in anticlockwise and
clockwise directions.
15. The same process is carried out by keeping the Horn 2 in opposite position i.e. For E
plane and readings are taken.
RESULT: Thus the radiation pattern of horn antenna is obtained.
EXPERIMENTAL SETUP:
27

TABULAR COLUMN:
VSWR Reading when
tuner is connected to
meter directly
VSWR Reading
when horns are
connected
Distance between
Horns in cms. N = a˜b
FORMULA:
Gdb = 10 log 10 (4πs/ λo) + ½ 10 log 10 PR / PT
Gdb = 10 log 10 (4πs/ λo) + ½ (PRdb - PTdb)
Average gain in decibels is = 39.58
Expt: No: 9 GAIN OF HORN ANTENNA
Transmitting Horn
Antenna
Receiving Horn
Antenna
Klystron Power Supply
Klystron Mount Isolator
Attenuator
V.S.W.R
Meter
Tunable Crystal
Oscillator

AIM:
To measure the gain of Horn Antenna.
EQUIPMENT REQUIRED:
Klystron power supply, klystron mount, Isolator, Variable Attenuator, Slotted section,
Detector Mount, Standard Gain Horn, VSWR Meter, CRO.
PROCEDURE:
1. Connect the tuner and crystal detector assembly to the slotted line.
2. Switch on Fan and then power supply. Obtain oscillations of the klystron.
3. Set the variable attenuator to get convenient reading in the VSWR Meter.
4. Maximize the crystal detector power supply and match the detector with the help of the
tuner.
5. Set a convenient reading on the indicator.
6. Disconnect the tuner and detector assembly. Connect horn H1 to the slotted line and
another horn H2 to the tuner and the detector assembly. Put the second horn in front of
the first. The distance between horns should be about one.
7. Read the VSWR meter and note the difference in two readings and measure the
separation‘s’ between the 2 horns.
8. Repeat the same experiment for different values of separation between horns.
9. Measure the value Yg with the help of slotted line and calculate the value of yo with the
formula.
(1/λg)2
= (1/λo)2
– (1/2a)2
10. Convert the power ratio Pr / Pi obtained in dbs into pure number by use formula.
PR / PT = Antilog 10 (N/10)
Where N – Number of db measured.
11. Now calculation the gain using the equation
PR / PT = (λo/4πs)2
G1G2
Where S – Separation between aerials.
λo – free space wavelength.
If two identical horns were used then G1 = G2. Hence the formula becomes.
PR / PT = (λo/4πs)2
G2
G = √ PR / PT. 4πs/ λo
We can also find gain use the following method. Take log for 2
Gdb = 10 log 10 (4πs/ λo) + ½ 10 log 10 PR / PT
Gdb = 10 log 10 (4πs/ λo) + ½ (PRdb / PTdbs)
RESULT:
The Horn antenna gain in decibels is found out to be -39.58 db.
29

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