Electronics & Communication Engineering Branch: -8th Semester

G.H.RAISONI COLLEGE OF ENGINEERING, NAGPUR 

Department: -Electronics & Communication Engineering 

Branch: -8 th Semester [Electronics And Telecommunication] 

Subject: -UHF and Microwave 

List of Experiments 

1) To study various UHF components. 

2) To verify the relationship between power and repeller voltage in reflex 

klystron. 

3) To determine the frequency and tuning range of reflex klystron. 

4) To analyze the fixed and variable attenuator and plot the micrometer reading 

Vs attenuation. 

5) To determine the coupling factors and directivity of directional coupler. 

6) To measure the power distribution of various wave guide Tee i.e. E plane, H 

plane, Magic Tee. 

7) To plot standing wave pattern and find guide wave-guide of reflex Klystron. 

8) To find load impedances using smith chart. 

9) Calibration of indirect type frequency meter using direct frequency meter. 

10) To plot the V I characteristics of Gunn diode. 

11) Study of various antennas. 

12) To study relationship between beam voltage & Repeller voltage in 

Reflex klystron. 

13) To study and verify the operation of Circulator. 

14) To study and verify the operation of Isolator. 

15) To study and verify the operation of phase shifter. 

16) To study the VSWR measurement using Double minima method. 

17) To study the VSWR measurement using calibrator attenuator.

18) To studies variable attenuator & plot the micrometer reading vs. 

Attenuation. 

19) To measure the power distribution of Magic Tee

Experiment No 1 

Aim: - To study the various UHF components. 

List of Components:- 

1) Rectangular wave guide 

2) Circular wave guide 

3) Wave guide stand 

4) Flanges 

5) Fixed attenuator 

6) Micrometer type frequency meter 

7) Broad band tuned probe 

8) Wave guide matched detector mount 

9) Wave guide detector mount (tunable) 

10) Precision slide screw tuners 

11) Klystron mount 

12) Three port ferrite circulator 

13) E-H tuners 

14) H plane Tee 

15) E plane Tee 

16) Directional coupler 

17) Isolator 

18) Match termination 

19) Precision movable short 

20) Circular rectangular wave guide 

21) Load cell 

22) Horn antenna 

23) Sectoral horn antenna 

24) Pyramidal antenna 

25) Wave guide twist 

26) Liquid dielectric cell 

27) Solid dielectric cell 

28) Gunn oscillator 

29) PIN modulator 

30) Slotted section with probe carriage 

31) VSWR meter 

32) Klystron power supply 

33) Gunn power supply

Experiment no 2 

Aim: -To verify the relationship between power & repeller voltage in a reflex 

Klystron. 

Apparatus: - 

Reflex Klystron, Klystron power supply, Isolator, frequency meter, Variable attenuator, 

Detector mount, VSWR meter, BNC cable. 

Block Diagram:- 

Klystron 

power 

supply 

Klystron 

with 

Mount 

Theory: - 

Isolator 

Frequency 

meter 

Variable 

attenuator 

X band microwave bench set up 

Detector 

mount 

Multimeter 

V.S.W.R 

Meter 

Oscilloscope 

The reflex klystron makes use of velocity modulation to transform a continuous 

electron beam in to microwave power. Electron emitted from the cathode are 

accelerated and passed through the positive resonator toward negative reflector, which 

retard and finally reflects electron and electron return back through the resonator. 

Suppose hi field exist between the resonator. The electron traveling forward will be 

accelerated or retarded. As the voltage at the resonator change in amplitude, the 

accelerated electron leaves the resonator at the increased velocity and the retarded 

electron leave at the reduced velocity. The electrons leaving the resonator will need 

different time to return due to change in velocities. As a result returning electron group 

together in bunches. As the electron bunches pass through resonator they interact with 

voltage at resonator grids. If the bunches pass the grid at such time that the electrons are 

slowed down by the voltage energy will be delivered to the resonator and klystron will 

oscillate.

Modes- the transit time at reflex klystron is governed by repeller and anode voltages, so 

these should be carefully adjusted & regulated. First cavity is tuned to connect value of 

transit time from data supplied by manufacturer repeller voltages. 

Each area of graph represents voltage condition permitting oscillators for particular 

value of ‘n’. 

Uses: it is used as signal source in noise wave generator local oscillator in microwave 

receiver, stable oscillator in Radar receiver. 

Observation:- 

For mode I 

For mode II 

Procedure:- 

Beam voltage= 

Beam current= 

Repeller voltage = 

Sr.No. Repeller 

voltage (Volts) 

Sr.No. Repeller 


Power(dB) 

Power(dB) 

1) Connect the equipment & components as shown in the figure. 

2) Set the attenuator for max attenuation & set the arrange switch on the 

VSWR meter to 40-db positions. 

3) Set the mid selector switch of reflex klystron power supply to AM MOD 

position 

4) Beam voltage knob fully anticlockwise direction i.e. minimum position and also 

repeller voltage knob to minimum position. 

5) On the klystron power supply, set beam voltage to 250V. Limit the beam 

current to 20mA.. Now gradually rotate repeller voltage knob to obtaine 

deflection in VSWR meter. 

6) Find the frequency of oscillation by tuning frequency meter & observing dip in 

VSWR meter. 

7) Now change the repeller voltage & observe output power reading in db in 

VSWR meter. 

8) Plot graph between repeller voltage on x-axis &corresponding output on y-axis.

Result:- Plot power output for different modes as a function of repeller voltage. 

Questions:- 

1) What is reflex Klystron? 

2) What are disadvantages of reflex klystron?

Experiment No 3 

Aim: - To verify relationship between frequency of oscillation & repeller voltage of 


Apparatus:- 

Reflex Klystron, Klystron power supply, Isolator, frequency meter, 

Variable attenuator, Detector mount, VSWR meter, BNC cable. 


Theory:- 

Klystron 

power 

supply 

Klystron 

with 

Mount 

Isolator 

Frequency 

meter 

Variable 

attenuator 


Detector 

mount 

Multimeter 

V.S.W.R 

Meter 

The reflex klystron makes use of velocity modulation to transform a continuous 

electron beam in to microwave power. Electron emitted from the cathode are 

accelerated and passed through the positive resonator toward negative reflector, which 

retard and finally reflects electron and electron return back through the resonator. 

Suppose hi field exist between the resonator. The electron traveling forward will be 

accelerated or retarded as the voltage at the resonator change in amplitude. The 

accelerated electron leaves the resonator at the increased velocity and the retarded 

electron leave at the reduced velocity. The electrons leaving the resonator will need 

different time to return due to change in velocities. As a result returning electron group 

together in bunches. As the electron bunches pass through resonator they interact with 

voltage at resonator grids. If the bunches pass the grid at such time that the electrons are 

slowed down by the voltage energy will be delivered to the resonator and klystron will 

oscillate. 

Oscilloscope

The frequency is preliminary determined by the dimension of resonant cavity. Hence by 

changing the volume of resonator, mechanical tuning range of klystron is possible. Also 

a small frequency change can be obtained by adjusting the reflector voltage. This is 

called electronic tuning. 

Observation:- Beam voltage= 

Beam current= 

Repeller voltage= 

For Mode I 

Procedure:- 

For Mode II 

Repeller 


Repeller 


Frequency 

(GHz) 

Frequency 

(GHz) 

1) Connect the equipment &component s as shown in the figure 

2) Set the variable attenuator to around zero position & set the range switch of 


3) Anti-clockwise direction, repeller voltage knob to minimum position. 

4) On the klystron power supply, VSWR meter &cooling fan. Set the beam voltage 

to 250v 

5) Gradually increase repeller voltage &look for sudden deflection in VSWR 

meter. 

6) Note the corresponding frequency with the help of frequency meter. Also note 

the repeller voltage. 

7) Slightly vary the repeller voltage on either side of this reading. Note the 

corresponding variation of the frequency. 

8) Find the tuning range after plotting the 3db points on the repeller voltage vs. 

power o/p graph. 

Result:- Find tuning range for two widely different repeller voltages. 

Questions:- 

1) What do you mean by higher mode? 

2) What are applications of klystrons?

Experiment no: 4 

Aim: -To verifies the fixed attenuator & plot the micrometer reading vs. 

Attenuation. 

Apparatus:- 


Variable & variable attenuator, Detector mount, VSWR meter, BNC 

Cable Matched load 


Klystron 

power 

supply 

Klystron 

with 

Mount 

Klystron 

power 

supply 

Microwa 

ve 

source 

Isolator Frequency 

meter 

Variable 

attenuator 

Attenuation of fixed and variable attenuator 

Isolator Frequency 

meter 

Variable 

attenuator 

Insertion loss and attenuation measurement of attenuator 

Slotted line Attenuator 

Slotted line 

V.S.W.R 

meter 

V.S.W.R 

meter 

Matched 

load 

Attenuator 

Matched 

load 

Detector 

mount

Theory:- 

The attenuator is a two port bidirectional device ,which attenuates some power in 

desired direction . 

Attenuation (A) =10 log (p1/p2) 

Where 

P1=power absorbed without attenuator. 

P2=power absorbed with attenuator. 

It consists of rectangular waveguide, which gives out the wave with resistive 

opposition. It is made up of Teflon and Polystyrene material. It opposes the power in 

desired direction. 

Fixed attenuation is defined as the ratio of power absorbed by the load with attenuation 

in the line. Attenuator used as variable attenuator. It is considerably reduced maxi 

attenuation .It is so because the electric intensity there is much lower for dominant 

mode .So they are made perpendicular to electric field place apart. 

Following characteristics of attenuators can be studied 

1) Input VSWR 

2) Insertion loss 

3) Amount of attenuation offered in to the lines 

4) Frequency sensitivity 

Observation:- 

Fixed attenuation O/p power 

(forward 

direction) 

Beam voltage = 

Beam current = 


Output Power( without attenuator) = 

O/p power 

(reverse direction) 

Average

Procedure:- 

Procedure for fixed attenuator: - 

1) Make a set up on. 

2) Set the Beam voltage between 250 to 300v limiting the beam current below 20 

mA. 

3) Obtained a mode at some value of repeller voltage by observing a sudden 

deflection in the VSWR meter. 

4) Adjust the reading of VSWR meter to 1db (in the range of 40 db) without fixed 

attenuator in the set up. 

5) Insert the fixed attenuator & note the reading on VSWR meter. 

6) Difference between reading with &without attenuator, gives the value of 

attenuation for the fixed attenuator. 

Procedure for variable attenuator:- 

1) Insert the variable attenuator. 

2) Observe micrometer reading & VSWR meter reading for different Settings of 

variable attenuator. 

3) Plot graph between the micrometer reading & VSWR meter reading in db. 

Result:- Value of attenuation 

1) Attenuator (3 dB) = 



Question:- 

1) What are types of attenuator? 

2) Where are different applications of attenuators?

Experiment No: 5 

Aim: -To find coupling factor & directivity of directional coupler. 

Apparatus:- 


Variable & variable attenuator, Detector mount, VSWR meter, 

BNC cable Matched load. 


Theory:- 

Microwave 

source 

Slotted 

line 

Isolator Variable 

Attenuator 

Probe 

M.H.D 

coupler 

M.H.D 

coupler 

Measurement of VSWR of M.H.D.coupler 

Frequenc 

y meter 

VSWR 

meter 

Matched load 

Matched load 

Matched load 

Matched load 

Directional coupler is a four-port device. Here power can be divided into almost in any 

ratio i.e. it samples energy flow in particular direction. 

It has a property that wave incident at port 1 coupler the power in 2 & 3 but not 

at port 4. Power incident at port 4 coupled with 3& 2 only met with 1, it means port 4 & 

1 are decoupled i.e. isolated port (S14=0). Similarly port 2 & 3 are also decoupled. 

It consists of two wave guide with a suitable coupling aperture located on 

common wall of wave guide. The distance between two apertures must be odd multiple 

of λg/4 .The performance &characteristics of directional coupler is determine by 

following parameter.

1) Coupling(C) = 10 log (pi/pf) db 

2) Directivity (D) = 10 log (pf/pb) db 

3) Isolation (I) =10 log (pi/pb) db 

4) Insertion loss (L) =10 log (pi/pt) db 

Main line insertion loss is the attenuation introduced in transmission line by insertion of 

coupler. It is defined as insertion 

Loss = 10 log 10P1/P2 When power is entered at port 1. 

Observation:- 

Procedure: 


Beam current= 

Transmitted power= 

Forward power= 

Reverse power= 

Directivity= 

Coupling factor = 

Isolation loss = 

Insertion loss= 

1) Connect the set up as per the block dig .set mode selector switch to AM 

position. 

2) Adjust beam voltage between 250 to 300v. 

3) Set repeller voltage to any value between 50 to 100v 

4) Tune the set up to obtained max output on VSWR meter. 

5) Adjust the output to the reference level say 1 db. 

6) Insert the directional coupler just before the demodulator with Auxiliary arm 

(port 3) connected to detector. Port 2 should be terminated with matched load. 

Input to the coupler is at port 1. 

7) The demodulator output taken at port 3 of coupler is observed on VSWR meter. 

8) This power is called as forward power pf. 

9) Reverse the coupler & observe the output at port 3 while port 1 is terminated 

with matched load. This power is called as backward power Pb. 

10) The output of the set up without the coupler is called as pi.

Result:- 

Find coupling factor and directivity for two couplers 

Coupling factor = 

Directivity = 

Insertion loss = 

Question:- 

1) Define directional coupler. 

2) What are performance characteristics of directional coupler?


Aim: -To measure the power distribution of various magic Tee i.e. E plane, H plane. 

Apparatus:- 


Variable & variable attenuator, Detector mount, VSWR meter BNC 

Cable Matched load E plane, H plane & Magic Tee. 

Block Diagram: - 

Microwave 

source 

Theory:- 

Isolator Freque 

ncy 

meter 

Slotted 

line 

Detector 

mount 

Variable 

attenuator 

Study of Magic Tee 

VSWR 

meter 

Slotted 

line 

Wave-guide Tee’s are used for connecting a branch section of wave-guide in series or 

parallel with the main wave-guide. Tees are also be used as power divider field. 

1) Input VSWR- Value of SWR corresponding to each port as a load to the line while 

other ports are terminated in matched load. 

Tee 

Matched 

termination 

Matched 

termination 

Matched 

termination 

Tee 

2 

1 

Matched 

termination 

Matched 

termination 

Matched 

termination

2) Isolation- The isolation between E and H arm is defined as the ration of the power 

supplied by the generator connected to the E port 4 to the power detected at H arm port 

3 Isolation=10 log10P4/P3 

3) Coupling coefficient- It is defined as Cij=10 – /20 

Where is attenuation /isolation in dB when it is input arm and j is output arm 

Thus = 10 log Pi/Pj 

Where Pi is power delivered to arm i and Pj is power detected at j arm 

E plane Tee- Model 6031 E plane Tee is a type T junction & consist of 3 section wave 

guide joint together in order to divide & compare power levels .The signals entering 

first part of the Π junction will be equally divided at 2 nd 3 rd port of magnitude but 

opposite in direction. 

H plane Tee-Model 3065 H plane TEE are shunt type T-junction that is used in 

conjunction with VSWR meter, Frequency meter &other detector devices. 

Magic Tee – Model 3045 E-H consist of section of wave-guide with both series & 

shunt wave-guide are mounted at exact mid point of the main arm. This becomes four 

terminal devices where one terminal is isolated from the i/p. VSWR of 1.40 over +- 

15%freq range. This is achieved by inserting &connecting piece with stub. 

Procedure: - 

H-plane Tee: - 

a) Give i/p at port 1 

b) Observe o/p on VSWR meter at port 2&3. 

E plane Tee 

a) Give i/p at port 1. 

b) Observe output at port 

Magic Tee 


b) Observe the output at port 2,3&4 

c) Give i/p at port 4. 

d) Observe the o/p at port 1,2&3. 

Observation:- 

Beam voltage= 

Beam current= 

Repeller voltage=

a) H plane Tee 

1. Input at port 1= 

2. Output voltage 

At port 2= 

At port 3= 

b) E plane Tee 

1. Input at port 1= 

2. Output 

At port2= 

At port 3= 

Result: - Discuss the power distribution in each Tee. 

Question:- 

1) What are different types of Tee? 

3) What do you mean by ‘Magic’ Tee?


Aim: -To verify standing wave ratio using slotted line section. 

Apparatus:- 

Reflex Klystron ,Klystron power supply, Isolator, frequency meter, Variable & variable 

attenuator, Detector mount, VSWR meter, BNC cable Matched load E plane, H plane & 

Magic Tee. 


Klystron 

power 

supply 

Klystron 

mount 

Theory:- 

Isolator Frequency Variable 

meter attenuator 

VSWR 

meter 

Standing wave using slotted line section 

Slotted line 

section 

Slide screw 

tuner 

The electromagnetic field at any point of transmission line may be considered as the 

sum of two traveling waves. The ‘Incident wave’ propagates from generator and the 

reflected wave propagates toward the generator. The reflected wave is setup by 

reflection of incident wave from a discontinuity on the line or from the load impedance. 

The magnitude and phase of reflected wave depends upon amplitude and phase of the 

reflecting impedance. The presence of two traveling waves, gives rise to standing wave 

along with the line. The maximum field strength is found two waves are in phase and 

minimum where the two waves add in opposite phase. The distance between two 

successive minimums or maximum is half the guide wavelength on the line. The ratio 

of electrical field strength of reflected and incident wave is called reflection coefficient. 

The unknown device is connected to slotted line and SWR=S0 and position of one of 

the max is found. The device of the difference between min positions is used as 

reference position for reference position for impedance measurement. The unknown 

device is replaced by movable short now successive maximal positions are noted. 

Matched 

termination

Find the difference between min position and max position obtained due to continuous 

load slotted line section consist of precision mechanism section of wave guide in which 

small longitudinal slot has been cut which is basic means of non tearing. A built probe 

has a scale with vernier reading of a form 0.01 cm. 

The voltage standing wave Ratio (VSWR) is defined as ratio between maximum and 

minimum field strength along the line. 

Hence VSWR S = Emax/Emin 

= (|Ei| + |Er|) / (|Ei| - |Er|) 

Reflection Coefficient P = Er / Ei = (Z - Z0) / (Z + Z0) 

Where Z is the impedance at a point on line. Z0 is characteristic impedance. 

The above equation gives following equations. 

Observation:- 

|e| = (s-1) / (s+1) 

Main scale reading Venier scale 

reading 

Procedure: - 

Beam voltage= 236 V 

Beam current= 13 mA 

Repeller voltage= 5V 

Total reading Power (db) 

1) First Switch on the supply 

2) Tune the bench 

3) Move the slotted line section slowly so that SWR meter reading is minimum 

4) Now take the reading of VSWR for different position 

5) Plot the graph between VSWR and distance. 

Result:- Thus, standing waves in wave guide is plotted and theoretical practical 

value of guide wavelength are found. 

Question:- 

1) What do you mean by standing wave ratio? 

2) Which meter we used to measure standing wave?


Aim: - To find load impedances using smith chart. 

Apparatus:- 



BNC cable Matched load E plane, H plane & Magic Tee. 


Klystron 

power supply 

2K25 

Klystron 

mount 

Theory: - 

Isolator 

Frequency 

meter 

Variable 

Attenuator 

Set up for Impedance measurement 

The impedance at any point of a transmission line can be written in the form R + jX. 

For comparison SWR can be calculated as, 

S = (1 + |R|) / (1 - |R|) 

Probe 

Slotted 

line 

V.S.W.R 

meter 

S. S. 

Tuner 

Movable 

short 

Where c = (Z/Zo + 1) / (Z/Zo – 1) 

Z is the impedance at any point. The measurement is performed in following way. 

The unknown device is connected to the slotted line and the SWR = so and the position 

of one minima is determined. Then unknown device is replaced by movable short to 

the slotted line. Two successive minima positions are noted. The twice of the 

difference between minima position will be guide wavelength. One of the minima is 

used as reference for impedance measurement. Find the difference of reference minima 

and minima position obtained form unknown load. Let it be‘d’. Take a smith chart 

‘taking ‘1’ as center, draw a circle of radius equal to so. Mark a point on circumference 

Matched 

terminator 

r

of chart towards load side at a distance equal (to-d)/λ. Join the center with this point. 

Find the point where it cut the drawn circle. The co-ordination of this point will show 

the normalized impedance of load. 

Procedure: - 

1) Connect the component and equipment as shown in the diagram 

2) Set the modulation switch of the klystron power supply to CW position. Beam 

voltage control knob should be kept at mini. Repeller voltage knob should be at 

mini. 

3) On the klystron power supply. 

4) Gradually increase the beam voltage up to 250v Limiting the beam current 

below 20mA. 

5) Keep the direct frequency meter completely open &adjust the attenuator to 

obtained current of 1 mA at the o/p 

6) Move the plunger of indirect frequency meter to obtain adapt in ammeter 

7) Note the micrometer reading on the direct frequency meter &observe the 

corresponding frequency on the direct frequency meter. 

8) Repeat steps 5, 6&7 after changing the setting of frequency on the direct 

frequency meter. 

9) Plot the graph between frequency &micrometer readings. 

. 

Observation:- 

Beam voltage= 

Beam current= 


Repeller voltage Current (mA) Micrometer 

readings 

Result:- The calculated load impedance is = 

Question:- 

1) What are various application of smith chart? 

2) How to measure load impedance using smith chart? 

Frequency from 

calibration chart


Aim: - Calibration of indirect type frequency meter using direct frequency meter. 

Apparatus:- 



BNC cable Matched load E plane, H plane & Magic Tee. 


Klystron 

power 

supply 

Klystron 

with 

Mount 

Theory:- 

Isolator 

Frequency 

meter 

Variable 

attenuator 


Detector 

mount 

Basically there are two types of frequency meter available in our lab. They are Direct 

frequency meter and indirect frequency meter. 

Direct frequency meter – In direct frequency meter we get direct reading as by simple 

observation basically we are aligning horizontal line on the vertical line and particular 

obtained in between two horizontal lines is required frequency. 

Indirect frequency meter – Here in these we are measuring frequency indirectly that 

is we are required to calculate least count of frequency meter and corresponding 

frequency we will get by measuring both the main scale reading and variable scale 

reading along with the least count. 

The impedance at any point of transmission line can be calculated as 

Multimeter 

V.S.W.R 

Meter 

Oscilloscop 

e

S=1-P1 /1-P2, C= (Z/Z0-1)/Z/Z0 





Find the difference between min position and max position obtained 

due to continuous load slotted line section consist of precision mechanism section of 

wave guide in which small longitudinal slot has been cut which is basic means of non 

tearing. A built probe has a scale with venire reading of a form 0.01 cm least counts and 

can be mounted easily if precision readings are required 

Procedure: - 

1) Tune the test bench 

2) Note down the max & min VSWR values by changing slotted line section 

distance 

Observation:- 

Calculate power by Pmax & Pmin:- 

Pmax= 

Pmin= 

R= 

F= 

λ= 

Beam voltage= 

Beam current= 


Result: - Discuss the power distribution in each Tee. 

Question:- 

1) Which type of frequency meter is convenient to use? 

2) How we can measure direct frequency meter?


Aim: - Study of Gunn diode and plot VI characteristics of Gunn diode. 

Apparatus:- 


Variable & variable attenuator, Detector mount, VSWR meter, BNC 

Cable Matched load E plane, H plane & Magic Tee. 


Klystron 

power 

supply 

Gunn 

diode 

Theory:- 

Isolator PIN 

modulator 

CRO 

Frequency 

meter 

Set for study of a gunn oscillator 

Variable 

attenuator 

VSWR 

meter 

Detector 

The Gunn oscillator is based on negative differential conductivity effect in bulk 

semiconductors which has two conduction band minima separated by an energy gap .A 

disturbance at cathode gives rise to high field region which travel’s towards the anode 

.When this high field domains reaches the anode, it disappears and another domain is 

formed at the cathode and starts moving anode and so on. The time required for domain 

to travel from cathode to anode gives oscillation frequency. 

A uniform type of uniform type of Gunn diode with same contact as the end surface. 

Above some critical voltage current becomes function of time .It was discovered by J B 

Gunn. It uses bulk property of semiconductor only. So it must be associated with 

electron rather than holes .The voltage applied is proportional to the sample length and 

hence electric field is expressed in v/m. 

When DC voltage is applied across the side of Gunn diode, cadmium ferrite in -ve 

resistance property across at particular voltage range value .As the applied potential 

increases i.e. greater than electric field higher electron present, hence higher current 

across the line in short time so acceleration occur in microwave range. Actually

Frequency of oscillation in determined the time so acceleration occurs in microwave 

range. Actually frequency of oscillation is determined the time that the bunches of 

electron form and arrive at the end. 

Procedure: - 

1) Switch on the Gunn power supply. 

2) Adjust the bench to get maximum o/p waveform 

3) By making voltage initially zero note down the current. 

Observation:- 


Beam current = 


Voltage (volt) Current (mA) 

Result:- Thus the VI characteristics of Gunn diode is studied. 

Question:- 

1) How Gunn diode is different from other diode? 

2) What are different applications of Gunn diode?

Aim: -To study the various antennas. 


Gunn 

power 

supply 

Gunn 

oscillator 

Theory:- 

Isolator 

V.S.W.R. 

Meter 


Pin 

modulator 

Detector 

Variable 

attenuator 

Set up for antenna measurement 

Frequency 

meter 

Antennas are used at all frequency but in actual practice the frequency on which it 

operates depends on its shape to the large extent . Antenna types are 

1) Horn antenna- A horn antenna may be regarded as a flared out or open out 

wave guide A wave guide is capable of radiating in to open space provided the 

same is excited at one end and open at other end. However the radiation is much 

greater through wave-guide than the two-wire transmission the line in waveguide 

is small in portion of incident wave is radiated and large portion is 

reflected back by the open circuit. 

2) Parabolic reflector or microwave dish- A parabola is a two-dimensional plane 

curve .A practical reflector is a three dimensional curved surface. Therefore 

rotating a parabola about its axis .The surface so generated is called as 

“Parabolic” Which is also called as “Microwave Dish or Parabolic Reflector” 

forms practical reflector. Parabolic produces a parallel beam of circular cross 

section because the mouth of parabolic is circular.

3) Hertz antenna- It is also a half wave dipole antenna .The dipole antenna dates 

back to the early half RF experiments in the center so that RF power can be 

applied to it .One can think of the half wave dipoles an open circuited 

transmission line that has been spread out so that the transmission line that has 

been spread out so that transmission can be spread out in space .A dipole can be 

of any length commonly is just under ½ wavelength long. 

L=486/F 

F=Frequency 

L= length 

Result:- Thus the different antennas are studied. 

Question:- 

1) What are different types of antennas? 

2) What do you mean by microwave dish?


Aim: - To study relationship between beam voltage & Repeller voltage in 


Apparatus:- 


Variable attenuator, Detector mount, VSWR meter, BNC cable. 

Block diagram:- 

Theory:- 


In Reflex klystron oscillation are obtained only for particular combination of Vo & Vr 

which gives desired transient time. The each shaded area correspond to oscillation at a 

particular transit time mode between 1(3/4) to 4(3/4) cycles and each value of n is said 

to be different modes in a reflex klystron .The earlier the mode the larger will be the 

amount of power which is advantages but it require higher voltage so lower efficiency 

and also increase the insulation problem. 

If the frequency of oscillation change appreciably the pattern still has the same general 

characteristic but location of the region of oscillation of the region of oscillation are 

shifted because of the fact that with a new frequency different transit time in second is 

required to give same transit time in cycle. 

Observation:- 

Klystron 

power 

supply 

Klystron 

with 

mount 

Isolator 

Frequen 

cy meter 

Variable 

attenuator 

Beam voltage Repeller voltage 

VSWR 

meter 

Detector 

mount

Procedure:- 

1. Connect the equipment &component s as shown in the figure 

2. Set the variable attenuator to around zero position & set the range switch of 


3. Set the mid selector switch to AM –MOD position, beam voltage knob fully 

anti-clockwise direction, repeller voltage knob to minimum position. 

4. On the klystron power supply, VSWR meter &cooling fan .Set limiting beam 

current to less than 16 mA 

5. Gradually increase beam voltage &look for sudden variation in repeller voltage 

6. Note the corresponding voltage with the help of meter. Also note the repeller 

voltage. 

7. Slightly vary the repeller voltage on either side of this reading. Note the 

corresponding variation of the repeller voltage. 

Result:- 

Study relationship between beam voltage & repeller voltage in reflex klystron. 

Viva Questions :- 

1) What is the nature of the graph between repeller voltage and the beam voltage? 

2) What do you mean by optimum bunching?


Aim: - To study and verify the operation of Circulator. 

Apparatus:- Reflex Klystron ,Klystron power supply ,circulator ,Isolator ,frequency 

meter, Variable attenuator Detector mount ,VSWR meter ,BNC cable. 


VSWR 

meter 

Theory:- 

Klystron 

power 

supply 

Detector 

Klystron 

mount 

Circulator 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 


Variable 

attenuator 

Frequenc 

y meter 

Fixed 

attenuator 

It is a multipart microwave junction device providing one way sequential transmission 

of power between the ports .It has a property that terminal is connected to next 

clockwise terminal depending upon the direction of wave-guide. Following the 

different ways to construct a circulator. 

1) Circulator using faradays rotation isolator. 

2) Using two magic Tee and Gyrator. 

3) Using 2 side hole and 3db coupler, 2 non reciprocal &1 reciprocal phase shifter 

. 

Two additional ports 3&4 place the construction of faradays circulator using isolator 

without twist except the resistive card 1&2 respectively. Port 3 is a rectangular wave

guide fastened in perpendicular to the circular wave guide near port 1 such that the 

narrow dimension of port 3 is parallel to the broad dimension of port 1 ie port 3 is 

perpendicular to port 1 similarly every time. 

Observation:- 

1. Input power at port 1= 36 dB 

Output power 

At port 2= 


Output power 

At port 3= 


Output power 

At port 4= 


Output power 

At port 1= 

Procedure:- 

Circulator:- 

a) Give i/p at port 1 

b) Observe o/p on VSWR meter at port 2. 

c) Give i/p at port 2 

d) Observe o/p on VSWR meter at port 3. 

e) Give i/p at port 3 

f) Observe o/p on VSWR meter at port 4 

g) Give i/p at port 4 

h) Observe o/p on VSWR meter at port 1. 

Result:- Find out path followed by the Circulator. 

Viva Question :- 

1) What is the basic concept of Circulator? 

2) What are the different type of Circulator?


Aim: - To study and verify the operation of Isolator. 

Apparatus:- Reflex Klystron ,Klystron power supply ,Isolator ,frequency meter, 

Variable attenuator, Detector mount ,VSWR meter ,BNC cable. 


Theory:- 

Klystron 

power 

supply 

VSWR 

meter 

Klystron 

mount 

Detector 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 


Variable 

attenuato 

r 

Frequenc 

y meter 

Fixed 

attenuato 

r 

It is a two port device where wave propagate from one port to second with out any 

attenuation and when wave moves in back direction there will be maximum attenuation 

therefore it is a online device. Isolator is mostly used to couple microwave generator to 

load so with these arrangement efficiency of reflex klystron will increase and also avoid 

the damage of microwave source generator due to the reflected wave because of 

mismatching at the output load .Its construction is very much similar to Gyrator except 

uses a 45 degree twist and 45 degree rotation in addition to these two thin resistive card

are inserted in the input and output wave guide parallel to the broader wall of wave 

guide 

If the wave will not fully absorbed by resistive card 1 then reflection taking places 

move toward port 2 which is absorbed by the resistive card at port 2 . 

Observation:- 

1) Input power at port 1= 

Output power 

At port 2= 


Output power 

At port 1= 

Procedure:- 

1) Give i/p at port 1 

2) Observe o/p on VSWR meter at port 2. 

3) Give i/p at port 2 


Result:- Find path followed by the isolator . 

Viva Questions :- 

1. What is the basic concept of Isolator? 

2. What are the different types of Isolator?


Aim: - To study and verify the operation of phase shifter. 

Apparatus:- Reflex Klystron, Klystron power supply, Isolator, phase shifter, 

frequency meter, Variable attenuator, Detector mount, VSWR meter, and BNC cable. 


VSWR 

meter 

Theory:- 

Klystron 

power 

supply 

Detector 

Klystron 

mount 

Phase 

shifter 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 


Variable 

attenuator 

Frequenc 

y meter 

Fixed 

attenuator 

Gyrator is also called as phase shifter is two port microwave device introduce by Hogel. 

It also act as a non reciprocal phase shifter which gives the phase shift of 180 degree for 

the transmission from port 2 to 1 .It also uses the property of faradays rotation. 

It consist of a rectangular wave guide with a 90 degree twist connected to circular wave 

guide with which carries a cylindrical ferrite rod with the end tapered to reduce the 

reflection from it and a static magnetic field Bo is applied along the axis to produce the 

90 degree faradays rotation of TE11 dominant mode in circular wave guide When the 

wave propagate form 1 to 2 in the direction when it passes through the twist the plane 

of polarization by rotates by 90 degree clockwise direction. The total angle of rotation

is 180 degree. When wave travel in the reverse direction from port 2 to 1 the faradays 

rotation is unchanged. 

Observation:- 


Output power 

At port 2= 


Output power 

At port 1= 

Procedure:- 

1) Give I /P at port 1 


3) Give I /P at port 2 


Result:- Find path followed by the Phase shifter. 

Viva Question: - 

1) What do you mean by gyrator? 

2) What are the applications of gyrator?


Aim: - To study the VSWR measurement using Double minima method. 




Theory:- 

Klystron 

power 

supply 

VSWR 

meter 

Klystron 

mount 

Detector 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 


Variable 

attenuator 

Frequenc 

y meter 

Fixed 

attenuator 

The direct measurement of minima for high VSWR causes over loading of detector To 

avoided these double minima method are used. 

A load having the high VSWR form the standing wave pattern in such a manner that 

minima point will not define and hence detector does not obey the square law .These 

method is used to measure high VSWR measurement 

The voltage standing wave Ratio (VSWR) is defined as ratio between maximum and 

minimum field strength along the line. 

Hence VSWRS S = Emax/Emin

= (|Ei| + |Er|) / (|Ei| - |Er|) 

Reflection Coefficient P = Er / Ei = (Z - Z0) / (Z + Z0) 

Where Z is the impedance at a point on line. Z0 is characteristic impedance. The above 

equation gives following equations. 

|e| = (s-1) / (s+1) 





Observation:- 

Measure distance d1= 

Measure distance d2= 

Measure distance∆d = 

Measure distance λg= 

Procedure:- 

1) Set the depth of the tunner, then slightly move then λg/4. 

2) Move the probe along the slotted line until minima is indicated. 

3) Adjust the VSWR gain control knob or attenuator to obtained the reading of 30 

db of a normal dB scale (0 to 10 dB) on VSWR meter. 

4) Move the probe to the left of the slotted line until full scale deflection is 

obtained (o dB on 0 to 10 dB scale) note & record the probe position on the 

meter 

5) Repeat the step 3&4 and then move the probe right to the slotted line until fullscale 

deflection is obtained Note the reading of probe position let it be d2. 

6) The distance between (d2-d1) is ∆d. 

7) Replace the slide screw tuner by movable short. 

8) Move the probe position and measure the distance between two successive 

minima position of the probe is equal to the λg/42. Twice this distance gives the 

wavelength λg. 

9) The VSWR is given by 

VSWR=λg/Π∆d. 

Result:-Get the value and calculate VSWR power. 

Viva Question :- 

1) What do you mean by VSWR? 

2) What is the different method of VSWR power measurement?


Aim: - To study the VSWR measurement using calibrator attenuator. 




VSW 

R 

meter 

Theory:- 

Klystron 

power 

supply 

Detector 

Klystron 

mount 

Slotted 

section 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 


Variable 

attenuator 

Frequenc 

y meter 

Fixed 

attenuator 

The magnitude and phase of reflected wave depends upon amplitude and phase of the 

reflecting impedance. The presence of two traveling waves, gives rise to standing wave 

along with the line. The maximum field strength is found two waves are in phase and 

minimum where the two waves adds in opposite phase. The distance bet two 

successive minimum or maximum is half the guide wavelength on the line. The ratio 

of electrical field strength of reflected and incident wave is called reflection coefficient. 

Standing wave are created along the length of the transmission line due to mismatch 

between characteristic impudence ZL.

The actual voltage v on the line at any point is the sum of Vi+Vr of the voltage of 

incident &reflected wave at the point .This result in the voltage distribution of the line 

is called as the standing wave pattern 

In the particular line both the waves are present voltage maximal occurs at the point 

where the two waves are in the same phase and minima the point where two wave are 

in the same phase where the difference between maxima and the minima are more 

pronounce larger. 

Observation:- 

Procedure:- 

Vmax= 

Vmin= 

A2(dB)=20 log(Vmax)= 

A1(dB)=20 log(Vmin)= 

A2-A1= 

1) Keep the attenuator to the minimum position. 

2) On the klystron power supply, VSWR meter and cooling fan 

3) Turn the meter switch of power supply to the beam voltage position set Vo 

to 300v with tuning the same switch note down corresponding beam current 

order of the 20 to 30 mA. 

4) Turn the same meter switch of power supply to Vr position and get the 

oscillation in the VSWR meter 

5) Move the probe with slotted to get the maximum deflection in VSWR meter 

and note down the attenuator reading move the probe to minima position 

read the VSWR on the scale and record it move the probe carriage along the 

slotted line for maxima position and the change the attenuation so that 

indication in the VSWR meter is same . 

6) Move the probe of slotted section to the minima position and with changing 

the attenuator reading bring the VSWR deflection to the maxima .Note 

down the attenuator reading i.e. nothing but as the VSWR. 

A2(dB)=20 log(Vmax) 

A1(dB)=20 log(Vmin) 

Result:-Get the value and calculate VSWR power. 

Viva Question:- 

1) What do you mean by Calibrator VSWR? 

2) What is the range of high VSWR power measurement?


Aim: -To studies variable attenuator & plot the micrometer reading vs. 

Attenuation. 


Variable & variable attenuator, Detector mount, VSWR meter, BNC cable Matched 

load. 


Klystron 

power 

supply 

Klystron 

with 

mount 

Theory:- 

Isolator Variable 

attenuator 

Direct 

reading 

frequency 

Attenuation of fixed and variable attenuator 

VSWR 

meter 

Detector 

mount 

Fixed 

attenuator 

The variable attenuator resistive card mounted inside the wave guide with its surface 

parallel to magnetic field .The electromagnetic field varies over the cross section of a 

wave guide and it is strongest at the center of the broad wall .The Vane can be moved 

laterally from center of the wave guide towards the narrow wall. Where the attenuation 

is considerably reduced .The resistive card changes the intensity near the narrow wall 

the resistive wire tapered over the either side of over the length of λg to minimize the 

reflection from itself to reduce type reflection from mounting rod ,which are parallel to 

the electromagnetic field used or place. 

There are various advantages of flap type of attenuator such as support of resistive card 

is very simple, no of ports of support are extended in to wave guide.

Observation:- 

Procedure:- 

Beam voltage= 

Beam current= 


Least Count = 

Micrometer scale 

reading 

O/p power (db) 

Procedure for variable attenuator:- 

3) Insert the variable attenuator. 

4) Observed micrometer reading & VSWR meter reading for different 

Settings of variable attenuator. 

5) Plot graph between the micrometer reading & VSWR meter reading in 

db. 

Result:- Value of attenuator 

1) Attenuator 1 

2) Attenuator 2 


1) What do you mean by Flap type of attenuator? 

2) What are the different application of attenuator?

VSWR 

meter 


Aim: - To measure the power distribution of Magic Tee 


Variable & variable attenuator, Detector mount, VSWR meter ,BNC cable Matched 

load ,Magic Tee. 


Theory:- 

Klystron 

power 

supply 

Detector 

Klystron 

mount 

Magic 

Tee 

Klystron 

oscillator 

Slide 

screw 

tuner 

Isolator 

Variable 

attenuato 

r 

Frequenc 

y meter 

Fixed 

attenuato 

r 

Magic Tee has the property that when the power is fed from port1 it will appear at port 

2 &3 only equal in magnitude &in phase but in the port 4.similarly power fed from port 

4 is coupled equally in to port 2&3 only equal in magnitude & opposite in phase but not 

coupled to port 4 similarly power fed from the port 3 is coupled equally in port 1&4 but 

not into port 2. 

It is used in microwave impedance measuring bridge, as a antenna duplexer ,as a 

balanced microwave mixer in the super heterodyne microwave receiver ,also used as a 

balance phase detector it detect the relative phase of the two signal . 

Magic Tee – Model 3045 E-H consists of section of wave-guide with both series & 

shunt wave-guide are mounted at exact mid point of the main arm. This becomes four 

terminal devices where one terminal is isolated from the i/p. VSWR of 1.40 over +- 

15%freq range. This is achieved by inserting &connecting piece with stub.

Observation:- 

Magic Tee 

Procedure:- 

1. Input power at port 1= 

2. Output power 

At port 2= 

At port 3= 

At port 4= 

3. Input power at port 1= 

4. Output power 

At port 1= 

At port 2= 

At port 3= 

Magic Tee 


b) Observe the output at port 2,3&4 

c) Give i/p at port 4. 

d) Observe the output at port 1,2 & 3 

Result:- Discuss the power distribution in Magic Tee. 


1) State Carlins theorem. 

2) What do you understand by scattering matrix of magic Tee?

Electronics & Communication Engineering Branch: -8th Semester

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