G.H.RAISONI COLLEGE OF ENGINEERING, NAGPUR Department: -Electronics & Communication Engineering

Branch: -8th 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:-

X band microwave bench set up Theory: - 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.

Isolator

Klystron with Mount

Frequency meter

Variable attenuator

Detector mount

Multimeter

Klystron power supply

V.S.W.R Meter

Oscilloscope

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:-

Beam voltage= Beam current= Repeller voltage = For mode I

Sr.No. Repeller voltage (Volts)

Power(dB)

For mode II

Sr.No. Repeller voltage (Volts)

Power(dB)

Procedure:-

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 Reflex klystron. Apparatus:- Reflex Klystron, Klystron power supply, Isolator, frequency meter, Variable attenuator, Detector mount, VSWR meter, BNC cable. Block Diagram:- X band microwave bench set up Theory:- 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.

Isolator

Klystron with Mount

Frequency meter

Variable attenuator

Detector mount

Multimeter

Klystron power supply

V.S.W.R Meter

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

Repeller voltage (Volts)

Frequency (GHz)

For Mode II

Repeller voltage (Volts)

Frequency (GHz)

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

VSWR meter to 40-db positions. 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:- Reflex Klystron, Klystron power supply, Isolator, frequency meter, Variable & variable attenuator, Detector mount, VSWR meter, BNC Cable Matched load Block Diagram:- Attenuation of fixed and variable attenuator Insertion loss and attenuation measurement of attenuator

Klystron with Mount

Klystron power supply

Isolator Frequency meter

Variable attenuator

Slotted line Attenuator

V.S.W.R meter

Matched load

Microwave source

Klystron power supply

Isolator Frequency meter

Variable attenuator

Slotted line

Attenuator

V.S.W.R meter

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:-

Beam voltage = Beam current = Repeller voltage =

Output Power( without attenuator) = Fixed attenuation O/p power

(forward direction)

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) = 2) Attenuator (6 dB) = 3) Attenuator (9 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:- Reflex Klystron, Klystron power supply, Isolator, frequency meter, Variable & variable attenuator, Detector mount, VSWR meter, BNC cable Matched load. Block Diagram:-

Measurement of VSWR of M.H.D.coupler

Theory:- 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.

Microwave source

Isolator Variable Attenuator

Frequency meter

Probe

Slotted line

M.H.D coupler

Matched load

VSWR meter

Matched load

Matched load

Matched load M.H.D coupler

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:- Beam voltage = Beam current= Transmitted power= Forward power= Reverse power= Directivity= Coupling factor = Isolation loss = Insertion loss= Procedure:

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?

Experiment No: 6 Aim: -To measure the power distribution of various magic Tee i.e. E plane, H plane. 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. Block Diagram: -

Study of Magic Tee Theory:- 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.

Microwave source

Isolator Frequency meter

Variable attenuator

Slotted line

VSWR meter

Tee 2

1

Matched termination

Matched termination

Matched termination Slotted

line Detector mount

Tee 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 2nd 3rd 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 a) Give i/p at port 1. 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?

Experiment No: 7

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. Block Diagram:- Standing wave using slotted line section Theory:- 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 wave- length 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.

Klystron power supply

Klystron mount

Isolator Variable attenuator

Frequency meter

VSWR meter

Slotted line section

Slide screw tuner

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. |e| = (s-1) / (s+1) Observation:-

Beam voltage= 236 V Beam current= 13 mA Repeller voltage= 5V

Main scale reading Venier scale

reading Total reading Power (db)

Procedure: -

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?

Experiment No: 8 Aim: - To find load impedances using smith chart. 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. Block Diagram:-

Set up for Impedance measurement Theory: - 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|) 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

Klystron power supply

2K25

Klystron mount

Isolator Frequency meter

Variable Attenuator

Slotted line

Probe

S. S. Tuner

Matched terminator r

Movable short

V.S.W.R meter

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= Repeller voltage Current (mA) Micrometer

readings Frequency from calibration chart

Result:- The calculated load impedance is = Question:-

1) What are various application of smith chart?

2) How to measure load impedance using smith chart?

Experiment No: 9 Aim: - Calibration of indirect type frequency meter using direct frequency meter. 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. Block Diagram:-

X band microwave bench set up Theory:- 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

Isolator

Klystron with Mount

Frequency meter

Variable attenuator

Detector mount

Multimeter

Klystron power supply

V.S.W.R Meter

Oscilloscope

S=1-P1 /1-P2, C= (Z/Z0-1)/Z/Z0 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. 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:- Beam voltage=

Beam current= Repeller voltage=

Calculate power by Pmax & Pmin:- Pmax= Pmin= R= F= λ= 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?

Experiment No: 10 Aim: - Study of Gunn diode and plot VI characteristics of Gunn diode. 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. Block Diagram:-

Set for study of a gunn oscillator

Theory:- 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

Gunn diode

Isolator PIN modulator

Variable attenuator

Klystron power supply

Frequency meter

VSWR meter

Detector

CRO

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 voltage = Beam current =

Repeller voltage =

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?

Experiment No: 11 Aim: -To study the various antennas. Block Diagram:-

Set up for antenna measurement Theory:- 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 wave-guide 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.

Gunn power supply

Gunn oscillator Isolator Pin

modulator Variable

attenuator

Frequency meter Detector V.S.W.R.

Meter

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?

Experiment no 12 Aim: - To study relationship between beam voltage & Repeller voltage in Reflex klystron. Apparatus:- Reflex Klystron, Klystron power supply, Isolator, frequency meter, Variable attenuator, Detector mount, VSWR meter, BNC cable. Block diagram:- X band microwave bench set up 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:-

Beam voltage Repeller voltage

Isolator

Klystron with mount

Frequency meter

Variable attenuator

Detector mount

VSWR meter

Klystron power supply

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

VSWR meter to 40-db positions. 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?

Experiment no 13 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. Block diagram:- X band microwave bench set up Theory:- 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

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Circulator Detector VSWR meter

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=

2. Input power at port 2= 40 dB Output power At port 3=

3. Input power at port 3= 44 dB

Output power At port 4=

4. Input power at port 4= 48 dB

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?

Experiment no 14 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. Block diagram:- X band microwave bench set up Theory:- 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

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Detector VSWR meter

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=

2) Input 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 4) Observe o/p on VSWR meter at port 1.

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?

Experiment no 15 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. Block diagram:- X band microwave bench set up Theory:- 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

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Phase shifter

Detector VSWR meter

is 180 degree. When wave travel in the reverse direction from port 2 to 1 the faradays rotation is unchanged. Observation:-

1) Input power at port 1= Output power At port 2=

2) Input 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 4) Observe o/p on VSWR meter at port 1.

Result:- Find path followed by the Phase shifter. Viva Question: -

1) What do you mean by gyrator?

2) What are the applications of gyrator?

Experiment no 16 Aim: - To study the VSWR measurement using Double minima method. Apparatus:- Reflex Klystron, Klystron power supply, Isolator, phase shifter, frequency meter, Variable attenuator, Detector mount, VSWR meter, and BNC cable. Block diagram:- X band microwave bench set up Theory:- 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

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Detector VSWR meter

= (|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) 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. 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 full-scale 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?

Experiment no 17

Aim: - To study the VSWR measurement using calibrator attenuator. Apparatus:- Reflex Klystron, Klystron power supply, Isolator, phase shifter, frequency meter, Variable attenuator, Detector mount, VSWR meter, and BNC cable. Block diagram:- X band microwave bench set up Theory:- 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 wave- length 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.

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Slotted section

Detector VSWR meter

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:-

Vmax= Vmin=

A2(dB)=20 log(Vmax)= A1(dB)=20 log(Vmin)= A2-A1=

Procedure:- 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?

Experiment no: 18 Aim: -To studies variable attenuator & plot the micrometer reading vs. Attenuation. Apparatus:- Reflex Klystron ,Klystron power supply ,Isolator ,frequency meter, Variable & variable attenuator, Detector mount, VSWR meter, BNC cable Matched load. Block diagram:- Attenuation of fixed and variable attenuator Theory:- 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.

Klystron with mount

Klystron power supply

Isolator Variable attenuator

Direct reading frequency

VSWR meter

Detector mount

Fixed attenuator

Observation:- Beam voltage= Beam current= Repeller voltage= Least Count =

Micrometer scale reading

O/p power (db)

Procedure:- 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

Viva Question: -

1) What do you mean by Flap type of attenuator? 2) What are the different application of attenuator?

Experiment no: 19 Aim: - To measure the power distribution of Magic Tee Apparatus:- Reflex Klystron ,Klystron power supply ,Isolator ,frequency meter, Variable & variable attenuator, Detector mount, VSWR meter ,BNC cable Matched load ,Magic Tee. Block diagram:-

Theory:- 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.

Klystron power supply

Klystron mount

Klystron oscillator

Isolator

Variable attenuator

Frequency meter

Fixed attenuator

Slide screw tuner

Magic Tee

Detector VSWR meter

Observation:- Magic Tee

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=

Procedure:- Magic Tee

a) Give i/p at port 1. 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. Viva Question: -

1) State Carlins theorem. 2) What do you understand by scattering matrix of magic Tee?