58808269 microwave-manual

RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A

RAJALAKSHMI ENGINEERING COLLEGEThandalam, Chennai – 602 105.

Department of Electronics and Communication Engineering

EC 2405 OPTICAL AND MICROWAVELAB MANUAL

(VII SEM ECE)

1Prepared 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.

Prepared by M.Sathish and M.Revathi


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. A2. Keep the control knob of klystron power supply as below:

Mode switch : CWBeam voltage knob : Fully anti-clockwiseRepeller voltage knob : Fully clockwiseMeter 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.



EXPERIMENTAL SETUP:

Fig.(A) Microwave bench setup for study of klystron modesOBSERVATIONS:

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+∆fRelativeFrequency f0

f0+∆f Reflector Voltage

Mode Characteristics of Reflex KlystronCALCULATIONS:

1. Knowing the maximum voltage of two adjacent modes, mode number can be computed using the relation


Klystron Power Supply

Reflex Klystron

IsolatorFrequency

MeterDetector 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 voltages2. Knowing mode number, transit time of each mode may be calculated from

T = (n+3/4)/f0 :::> t1 = N1/f01, t2 = N2/f023. 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:



Fig. (A) Microwave bench setup for study of Gunn Oscillator Characteristics.

MODEL GRAPH

Current Threshold Voltage

I

V0 VoltageCurrent Voltage Characteristics of Gunn Oscillator

Expt: No: 2 GUNN DIODE - CHARACTERISTICS

AIM:


Gunn Power Supply

Gunn Oscillator

PIN modulator

IsolatorVariable

attenuatorDetector Mount

V.S.W.RMeter

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 – clockwisePin bias knob/ Mod Amplitude : mid positionPin mod frequency : mid position

4. Keep the control knob of VSWR meter as below:Meter switch : normalInput switch : crystal low impedance/200kRange db switch : 50dbGain 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:



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:


Klystron Mount + Klystron

2k25/723A/B

IsolatorVariable Attenuator

Frequency Meter

Detector Mount

V.S.W.R. Meter

Slotted Line


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 lengthλg is guide wave lengthλc is cut off wave length

For TE10 mode λc = 2a where ‘a’ is broad dimension of wave guideNote: 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.3Set up variable attenuator at minimum attenuation position.Keep control knobs of vswr meter as given below:

Range : 50 dbInput switch : Crystal low impedanceMeter switch : Normal positionGain (Coarse & fine) : Mid position

Keep control knobs of klystron power supply as given below:Beam Voltage : OffMod-switch : AMBeam voltage switch : Full anticlockwiseReflector voltage : Full clockwiseAm amplitude knob : Full clockwiseAm 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 knobSet the reflector voltage to get some deflection in vswr meter.Maximize the deflection with AM amplitude and frequency control knob of supplyTune the plunger of mount for maximum deflectionTune the reflector voltage knob for maximum deflectionTune the probe for maximum deflection in vswr meterTune 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 meterMove 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


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 meterWhere, C = 3 x 108 meter per second

= 3 x 1010 cms per secondNote: 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



2k25/723A/B


Frequency Meter

Matched Termination

Prob

eSlotted Line


V.S.W.RMeter


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-efficientReflection co-efficient ( R) the size of reflectionR = Er/Ei = Zl – Z0 / Zl + Z0 -------- (2)Where Zl is load impedance, Z0 is characteristic impedanceThe above equation following equationsR = (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 dbInput switch : Low impedanceMeter switch : Normal positionGain : Mid position

Keep control knobs of klystron power supply as given below:Beam Voltage : OffMod-switch : AMBeam voltage knob : Full anticlockwiseReflector voltage knob : Full clockwiseAm amplitude knob : Full clockwiseAm 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 VSWRMove 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



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 positionInput switch - Crystal low impedance / 200kMeter switch - Normal positionGain (coarse & fine) - Mid position

4. Keep the control knobs of klystron power supply as below:Mod-switch - AMBeam voltage knob - Fully anti-clockwiseReflector voltage - Fully clockwiseAM-Amplitude knob - around fully clockwiseAM-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:



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 / P1Isolation (dB) = -10 log P4 / P1Directivity (dB) = -10 log P4 / P3Insertion loss (dB) = -10 log P2 / P1Thus 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 – A3dBDirectivity (dB) A3 – A4dBIsolation (dB) A1 – A4dBInsertion loss (dB) A1 – A2dB



Reflex Klystron

IsolatorFrequency

MeterAttenuator 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 : AMBeam Voltage Knob : Fully Anti ClockwiseRepeller Voltage Knob : Fully ClockwiseMeter Switch : Cathode Voltage Position

4. Keep the control knobs of VSWR meter as below:Range db : 50 db positionInput switch : Crystal low impedanceMeter switch : Normal positionGain (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).

Isolator1. 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.



RESULT: Thus the operation of ferrite circulator, isolator are studied and measured their insertion loss and isolation.

EXPERIMENTAL SETUP:

Three port circulator

OBSERVATIONS:

CIRCULATORA1 dB A2 dB A3 dB

ISOLATORA1 dB A12 dB A21 dB

CALCULATIONSCirculatorInsertion loss dB = A1 – A2 dBIsolation dB = A1 – A4 dBIsolatorInsertion loss dB = A1 – A12 dBIsolation dB = A1 – A21 dB



Klystron Mount

IsolatorAttenuator Isolator

CirculatorDetector Mount

V.S.W.R Meter

Matched Termination

Port 3 (Isolated)

Port 1(Input)

Port 2(coupled)


Expt: No: 6 a. ATTENUATOR CHARACTERISTICSAIM:

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 - offMod-switch - AMBeam voltage knob - Full anti clockwiseReflector voltage knob - Full clockwiseAm-amplitude knob - Full clockwiseAm frequency & amplitude knob - Mid positionSwitch 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 : normalii. Input switch : Low impedanceiii. Range db switch : 40 dbiv. 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.



RESULT: Thus the attenuation characteristics of a variable attenuator are studied.

EXPERIMENTAL SETUP:

Setup for Attenuator Characteristics

TABULAR COLUMNMicrometer Reading : 11.79mmFrequency 9.97 GHz : 9.97GHz

OBSERVATIONS:

S.No. Screw Gauge Reading

(mm)

Attenuation in Decibels



2k25/723A/B


Frequency Meter

Detector Mount

V.S.W.R. Meter

Slotted Line



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 9a2. Keep the control knobs of klystron power supply as below.

Mode switch : AMBeam Voltage Knob : Fully AnticlockwiseRepeller Voltage Knob : Fully ClockwiseMeter 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.9biv. 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.



EXPERIMENTAL SETUP:

Fig.9a. For Input Power measurement

Fig.9b. For coupled/isolated Power measurement



Klystron Mount

IsolatorVariable

Attenuator Tunable crystal Detector mount

V.S.W.R Meter


Klystron Mount

IsolatorVariable

AttenuatorTunable crystal Detector mount

V.S.W.R Meter

Magic Tee


Isolation between E and H armsIf 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 divisionThe 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

Attenuator setting when measuring power to H-arm A2 dB

Measurement of power divisionAttenuator setting when measuring

input to E/H arm A1 dBAttenuator setting when measuring power at collinear to arms A2 dB

Calculations:Isolation between E and H arm (dB) = (A1 – A2) dBCoupling between collinear arms and E/H arms (dB) = (A1 – A2) dB

EXPERIMENTAL SETUP FOR HORN ANTENNA:



TABULAR COLUMN0 in degrees Power received in decibels

clockwisePower received anticlockwise

0102030405060708090

H PLANE

0102030405060708090

E PLANE

MODEL GRAPH:

Expt: No: 8 HORN ANTENNA CHARACTERISTICS



Reflex Klystron Tube Mount

IsolatorAttenuator Frequency

Meter

V.S.W.R MeterCrystal

DetectorTransmitting 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:



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 Mount IsolatorAttenuator

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 equationPR / PT = (λo/4πs)2

G1G2Where 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/ λoWe 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.
