58808269 Microwave Manual
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Transcript of 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
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
3Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Klystron Power Supply
Reflex Klystron
IsolatorFrequency
MeterDetector Mount C.R.O
V.S.W.R. Meter
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
5Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
Prepared by M.Sathish and M.Revathi
Gunn Power Supply
Gunn Oscillator
PIN modulator
IsolatorVariable
attenuatorDetector Mount
V.S.W.RMeter
Slotted section
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
7Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
9Prepared by M.Sathish and M.Revathi
Klystron Mount + Klystron
2k25/723A/B
IsolatorVariable Attenuator
Frequency Meter
Detector Mount
V.S.W.R. Meter
Slotted Line
Klystron Power Supply
Tunable Probe
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.,
Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
11Prepared by M.Sathish and M.Revathi
Mode
Frequency meter ‘DIP’
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
RESULT: Thus the frequency characteristics of klystron have been determined.
EXPERIMENTAL SETUP:
Fig.5 Set up for Measuring Low, Medium & High VSWR
13Prepared by M.Sathish and M.Revathi
Klystron Mount + Klystron
2k25/723A/B
IsolatorVariable Attenuator
Frequency Meter
Matched Termination
Prob
eSlotted Line
Klystron Power Supply
V.S.W.RMeter
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
15Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
17Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Klystron Power Supply
Reflex Klystron
IsolatorFrequency
MeterAttenuator Directional
Coupler
V.S.W.R Meter
Matched load
Crystal Detector
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
19Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Klystron Power Supply
Klystron Mount
IsolatorAttenuator Isolator
CirculatorDetector Mount
V.S.W.R Meter
Matched Termination
Port 3 (Isolated)
Port 1(Input)
Port 2(coupled)
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
21Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Klystron Mount + Klystron
2k25/723A/B
IsolatorVariable Attenuator
Frequency Meter
Detector Mount
V.S.W.R. Meter
Slotted Line
Klystron Power Supply
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
23Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
EXPERIMENTAL SETUP:
Fig.9a. For Input Power measurement
Fig.9b. For coupled/isolated Power measurement
Prepared by M.Sathish and M.Revathi
Klystron Power Supply
Klystron Mount
IsolatorVariable
Attenuator Tunable crystal Detector mount
V.S.W.R Meter
Klystron Power Supply
Klystron Mount
IsolatorVariable
AttenuatorTunable crystal Detector mount
V.S.W.R Meter
Magic Tee
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
25Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Klystron Power Supply
Reflex Klystron Tube Mount
IsolatorAttenuator Frequency
Meter
V.S.W.R MeterCrystal
DetectorTransmitting Horn Receiving Horn
700 7060 6050 5040 4030 3020 2010 10
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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:
27Prepared by M.Sathish and M.Revathi
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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
Prepared by M.Sathish and M.Revathi
Transmitting Horn Antenna
Receiving Horn Antenna
Klystron Power Supply
Klystron Mount IsolatorAttenuator
V.S.W.R Meter
Tunable Crystal Oscillator
RAJALAKSHMI ENGINEERING COLLEGE EC2405-OPTICAL & MW LAB-ECE A
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.
29Prepared by M.Sathish and M.Revathi