mwe lab manual final

EXPERIMENT NO: 1 DATE:

Aim:- Introduction of microwave components & equipment.

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Theory:-

1] Klystron Power Supply:-

Klystron Power Supply, is a state-of-the-art solid-state, regulated power supply for operating low power Klystrons.It incorporates a number of property features:-

Regulated Beam Supply and Repeller Supply voltages. LED Digital meter for Beam voltage, current and Repeller voltage. Compact and Reliable. Modular construction for easy maintenance. In addition to AM and FM modulation of beam

-Beam supply:- Voltage range 200 to 450v continuously variable Current 50mA maximum Regulation .5% for 10% in main supply voltage Ripple less than 5mV rms-Repller supply:- Voltage range -10V to -270 continuously variable Regulation 0.25% for 10% in main supply voltage-Heat supply:- 6.3V DC (regulated)

2] Gunn Power Supply:-

Gunn power supply comprises of an electronically regulated DC power supply and a square wave generator designed to operate Gunn oscillator and pin modulator simultaneously. The DC voltage is variable from 0 to 10 volts. The frequency of square wave can be continuously varied from 800 to 1200 Hz. The front panel meter can read the Gunn voltage and the current drawn by the Gunn diode. The power supply is designed to protect Gunn diode from reverse voltage and from over voltage transients and from low frequency oscillations.

Voltage range 0 to 12V variable Current 1A max. Regulation 0.2% for 10% in main supply voltage Ripple 1mV rms3] VSWR Meter:-

The SWR meter or VSWR (voltage standing wave ratio) meter measures the standing wave ratio in a transmission line. The meter can be used to indicate the

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degree of mismatch between a transmission line and its load (usually a radio antenna), or evaluate the effectiveness of impedance matching efforts.

A VSWR meter should be installed near the antenna to avoid loss of transmission, which happens because transmission lines have a certain amount of loss. The reflected power travels back to the cable, producing a low reading on a VSWR meter.

4] Frequency Meter:-

Frequency meters, also called "wavemeters", the cylindrical cavity forms a resonator that produces a suck-out in the frequency response of the unit. This you would turn the knob until a dip in the response is observed. The graduations will tell you what frequency you are at.

Frequency meter are needed for moderate accuracy application in microwave application ans are usually best for this purpose since these permits full power flow down the transmission line except at the precise tuned frequency. The freq meter model of 455 consists of cavity with plunger and a section of standard waveguide. Direct reading freq meter model 710 measure freq accurately their long scale length.

5] Slotted Line:-

a device for measuring parameters in devices that have distributed constants (such as feeders or wave guides). It is used to find the standing-wave ratio (SWR) and the displacement d of the nodes or antinodes of the electric field intensity along the line; other physical quantities (total resistance, amplitude, and phase; coefficient of reflection) are found in terms of the SWR and d .Slotted lines in the form of a section of coaxial or wave-guide line connected between a generator G and object being measured Zl (see Figure 1) are used most frequently; a dial gauge head with a contact probe and a tuning oscillatory circuit (resonator) moves along a section of the line. The voltage from the circuit is fed to the detector and then to the indicator (in many cases, through an amplifier). Slotted lines are usually used in the frequency range from hundreds of megahertz to hundreds of gigahertz; the error of a slotted line is 2–5 percent.

6] Isolator:-

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An isolator is a two-port device that transmits microwave or radio frequency power in one direction only. A transmitter is a non-reciprocal transmitter device that is used to isolate one component relation from other component in the transmission line. An ideal isolator completely isolates the power from the propagation in the direction. Isolator is also known as UNILINE. It is used to shield equipment on its input side, from the effects of conditions on its output side; for example, to prevent a microwave source being detuned by a mismatched load.

7] Attenuator:-

Fixed Attenuator:- Fixed attenuators are used where fixed amount of attenuation is to be provide. If such a fixed attenuator absorb all the energy entering into it,we call it as a waveguide terminator. This normally consists of a short section of a waveguide with a tapered plug of absorbing material at the end.

Variable Attenuator:- Variable type of attenuator provide continuous or step wise variable attenuation. For rectangular waveguides, this attenuator can be flap type or van type. For circular waveguides rotary type is used.

8] A circulator:-

A circulator is a passive non-reciprocal three- or four-port device, in which microwave or radio frequency power entering any port is transmitted to the next port in rotation (only). Thus, to within a phase-factor, the scattering matrix for an ideal three-port circulator is

When one port of a three-port circulator is terminated in a matched load, it can be used as an isolator, since a signal can travel in only one direction between the remaining ports.

9] Twister:-

Twister is used to rotate the plane of polarization of waveguide transmission line. Twister is one type of waveguide, which is twisted such as 90º and 45º twists as shown in figure are helpful in converting vertical to horizontal polarization or vice versa. Twist can be incorporated along with bends also. Other configurations are available on special coder with different angle and different length.

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10] Magic Tee:-

Magic tee is a combination of E-plane and H-plane tee. The magic tee is a four-port, 180° hybrid splitter, realized in waveguide. Like all of the coupler and splitter structures, the magic tee can be used as a power combiner or a divider. It is ideally lossless, so that all power into one port can be assumed to exit the remaining ports. A signal incident on the sigma port (port 1) splits equally between ports 3 and 4, with the resulting signals being in phase. On the other hand, a signal incident on the delta port (port 2) also splits equally between ports 3 and 4, but the resulting signals are 180° out of phase. Ports 3 and 4 are sometimes called the co-linear ports as these are the only two ports that are in line with each other. its commonly used for mixing, duplexing and impedance measurement.

11] Horn Antenna:-

A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct the radio waves. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz. They are used as feeders (called feed horns) for larger antenna structures such as parabolic antennas, as standard calibration antennas to measure the gain of other antennas, and as directive antennas for such devices as radar guns, automatic door openers, and microwave radiometers. Their advantages are moderate directivity (gain), low SWR, broad bandwidth, and simple construction and adjustment.

12] Directional Coupler:-

Directional couplers are four-port circuits where one port is isolated from the input port. Directional couplers are passive reciprocal networks. All four ports are (ideally) matched, and the circuit is (ideally) lossless. Directional couplers can be realized in microstrip, stripline, coax and waveguide. They are used for sampling a signal, sometimes both the incident and reflected waves (this application is called a reflectometer, which is an important part of a network analyzer). Directional couplers generally use distributed properties of microwave circuits, the coupling feature is generally a quarter (or multiple) quarter-wavelengths.

13] Detector Mount:-

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The detector helps to detect the low frequency square wave modulated microwave signal. This is made possible by use of a non-reciprocal detector diode mounted in the microwave transmission line. The detector diode can be point contact type or metal semi-conductor Schottky Barrier Diode. There are three types of detector,

1) Tunable waveguide detector

2) Tunable co-axial detector

3) Tunable probe detector

14] Bands:-

The bend can be H bend or E bend. If the bend is in the direction of the wide dimension the H lines are affected and if the bend is un the direction of narrow dimension, the E line are affected. The bending radius must be at least 2λg to avoid SWR’s greater than 1.05 and mean length as long as possible. Sharp 90º bend creates total reflection resulting in infinite SWR. Therefore bends have to be gradual.

15] Terminator:-

Terminator is a device which is connected to the last peripheral device in a sequence or the last node in a network. Coaxial terminators and waveguide terminators are collectively known as radio frequency terminators or microwave terminators. They are used to absorb energy and prevent a signal from reflecting back from open-ended or unused ports. The loads are carefully designed to absorb virtually all the power ans assure allow SWR. They may be used where method load is required as in the measurement of reflection, discontinuities of obstacle in the waveguide system.

Conclusion:


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AIM: To Study the characteristics of the reflex klystron tube

EQUIPMENT: (1) Klystron power supply – SKPS-610.(2) klystron –tube 2k- 25 with klystron mount- XM-251,621,(4) frequency meter XF-710,(5) variable attenuator XA-520, (6) detector mount XD-, (7) guide stand XU-535, (8) VSWR meter SW-215, (9) oscilloscope, (10) BNC cable.

THEORY:Reflex klystron makes the use of velocity modulation to transform a continuous

beam power. Electrons emitted from the cathode are accelerated & passed through the positive towards negative reflector, which retards &, finally, reflects the electrons & the electrons turn the resonator. Suppose an if-field exist between the resonators, the electrons traveling for accelerated or retarded, as the voltage at resonator changes in amplitude. The accelerated & the resonator at an increased velocity and the retarded electrons leave at the reduce electrons leaving the resonator will need different time to return, due to change in velocities. As running electrons group together in bunches. As the electron bunches pass through resonator, with voltage at resonator grids. If the bunches pass the grid at such a time that the electrons own by the voltage that energy will be delivered to the resonator, and the klystron will oscillate the relation ship between out put power , frequency& reflector voltages .

The frequency is primarily determined by the dimensions resonant cavity. Hence, by changing the resonator, mechanical tuning of klystron is possible. Also, a small frequency change can be adjusting the reflector voltage. This is called Electronic Tuning.

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PROCEDURE: CARRIER WAVE OPERATION

1. Connect the components and equipments as shown in fig.2. Set the variable attenuator at the minimum at position.3. Set the Mod-switch of klystron power supply at CW position, beam voltage

control knob to fully anti clock wise and reflector voltage control knob to fully clock wise and the meter switch to ‘OFF’ position.

4. Rotate the knob of frequency meter at one side fully.5. Connect the D.C. microampere meter with detector.6. Switch ‘ON’ the klystron power supply, VSWR meter and cooling fan for the

klystron tube.7. Put on beam voltage switch and rotate the beam voltage knob clockwise slowly

up to 300 V meter reading and observe beam current position, “the beam current should not increase more than 30 mA”.

8. Change the reflector voltage slowly and watch current meter set the voltage for maximum deflection in the meter.

9. Tune the plunger of klystron mount for the maximum output.10. Rotate the knob of frequency meter slowly and stop at the position, where there is

lowest output current on multimeter. Read directly the frequency meter between two horizontal line and vertical marker. If micrometer type frequency meter is used, read the micrometer reading and use the frequency chart.

11. Change the reflector voltage and read the current and frequency for each reflector voltage.

SQUARE WAVE OPERATION1. Connect the equipments & components are as shown in fig 1.2. Set Meter of variable attenuator around some position.3. Set the range switch of VSWR meter at 40 db position, input selector switch to

crystal impedance position, meter switch to narrow position.4. Set Mod selector switch to AM-MOD position. Beam voltage control knob to

fully anticlockwise position.5. Switch on the klystron power supply, VSWR meter & Cooling fan.6. Switch on the beam voltage switch & rotate the beam voltage knob clockwise up

to 300v deflection in meter.7. Keep the AM-MOD amplitude knob and AM-FRE, knob at the mid position.8. Rotate the reflector voltage knob to get deflection in VSWR meter.9. Rotate the AM-MOD amplitude knob to get the maximum output in VSWR

meter.10. Maximize the deflection with frequency knob to get the maximum output in

VSWR meter.11. If necessary, change the range switch of VSWR meter 30 db to 50 db. If the

deflection in VSWR meter is out of scale or less than normal scale respectively. Further the output can be also reduced. Variable attenuator for setting the output for any particular position.

12. Find the oscillator frequency by frequency meter as described in the earlier setup.

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Conclusion:


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AIM: To study frequency & wavelength measurement using klystron power supply.

EQUIPMENT:(a) Klystron tube 2K25, (b) Klystron power supply 5KPS-610,Klystron mount,

XM-251, Isolator XI-621, Frequency meter X710, variable Attenuator XA-520, slotted section XS-651, tunable probe XP-655, VSWR meter SW-115, wave guide stand Xu-535, movable short XT-481/matched termination

THEORY:For domain TE10 mode rectangular wave guide lo, lg, lc is related as below:

Two method Directly from frequency meter By calculating

1/λ02 = 1/λg2 + 1/λc2

where λ0 is free space wavelength λg is guide wavelength

λc is cutoff wavelengthFor TE10 =2a where ‘a’ is broad dimension of wave guide

a=22.86mm for x-band.

PROCEDURE:1 Set up the components and equipments as shown in fig 2 Set up variable attenuator at minimum attenuation position3 Keep the control knobs of VSWR meter as below:

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Range =50 dbInput switch =crystal low impedanceMeter switch =Normal positionGain (Coarse- Fine) =mid position approx

4 Keep the controls knob of Klystron power supply as below:Beam voltage =OFFMid switch =AMBeam voltage knob =fully anticlockwiseReflector voltage knob = fully clockwiseAM- amplitude knob =around fully clockwise

AM- freq & amp. Knob =mid position

5 Switch ON the klystron power supply, VSWR meter and cooling fan.6 Switch ON the Beam voltage Switch position and set beam voltage at 300v

with help of beam voltage knob.7 Adjust the reflector voltage to get some deflection in VSWR meter8 Maximize the deflection with AM amplitude and frequency control knob of

power supply.

9 Tune the plunger of klystron Mount for maximum deflection10 Tune the reflected voltage knob for Maximum deflection.11 Tune the probe for maximum deflection in VSWR meter.

FREQUENCY MESUREMENT AFTER MAXIMIZING Method 1

1. Tune the frequency meter knob to get a ‘dip’ on the VSWR scale and note down the frequency directly from frequency meter.

2. Replace the termination with movable short, and detune the frequency meter.

METHOD 2 Move the probe along the slotted line. the deflection in VSWR

meter will vary. Move the probe to a minimum deflection position, to get accurate reading. If necessary increase the VSWR meter range db switch to higher position. Note and record the probe position.

Move the probe to next min. position and record the probe position again.

Calculate the guide wavelength as twice the distance between two successive minimum positions obtained as above.

Measure the waveguide inner broad dimension ‘a’ which will be around 22.86 mm (2.28 cm) for X-band.

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12 Calculate the frequency by following equationF = c/λ = c.(1/λg2 + 1/λc2)1/2

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Where c=3*10^8 meter/sec13 Verify with obtained by frequency meter.

CONCLUSION:


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Aim: To study frequency and wavelength using gunn power supply

EQUIPMENT:Gunn oscillator, gunn power supply, PIN modulator, isolator (XF621), frequency meter (XF710), variable attenuator (XA-520), detector mount, wave-guide stands, VSWR meter, cable and accessories, S-S tuner, termination (Xl400).

PROCEDURE:1. Set the components and equipments as shown in fig.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 fully anti-clockwisePin mod frequency any position

4. Keep the control knob of VSWR meter as below:Meter switch normalInput switch low impedanceRange db switch 40 dbGain control knob fully clockwise

5. Set the micrometer of gunn oscillator for required frequency of operation.6. ‘ON’ the gunn power supply, VSWR meter and cooling fan.

(A) Output power and frequency as a function of bias voltage1. Turn the meter switch of gunn power supply to voltage position.

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Gunn power supply

Gunn oscillator

Isolator Pin modulator

Variable attenuator

Frequency meter

Detector mount

OscilloscopeV.S.W.R meter

2. Increase the gunn bias control knob.3. Rotate PIN bias knob to around maximum position.4. Turn the output in the VSWR meter through frequency control knob of

modulation.5. If necessary change the range db switch of VSWR meter to higher or lower db

position to get deflection on VSWR meter. Any level can be set through variable attenuator and gain control knob of VSWR meter.

6. Measure the frequency-by-frequency meter and detune it.7. Reduce the gain bias voltage in the interval of 0.5 v to 1.0 v and note down

corresponding reading of output at VSWR meter and frequency-by-frequency meter.

8. Use the reading to draw the power vs. voltage curve and frequency vs. voltage and plot the graph.

9. Measure the pushing factor, which is frequency sensitivity against variation in bias voltage of an oscillator. The pushing factor should be measured around 8-volt bias.

(B) Square Wave Modulation1. Keep the meter switch of gunn power supply to volt position and rotate

gunn bias voltage slowly so that panel meter of gunn power supply reads 10v.

2. Tune the PIN modulator bias voltage and frequency knob for maximum output on the oscilloscope.

3. Coincide the bottom of square wave in 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 of the variable attenuator.

6. The difference of both db reading of VSWR meter gives the modulation depth of PIN modulator.

CONCLUSION:

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AIM: To determine standing wave ratio & reflection co-efficient using klystron power supply.

EQUIPMENTS:Klystron tube (2k25), Klystron power supply (skps-610), VSWR Meter (SW115), Klystron Mount (XM-25), Isolator (XF621), Frequency meter (XF710), variable attenuator (XA-520), Slotted line (X565), Tubal probe (XP655), waveguide stand (XU535), movable short/termination (XL400), or any unknown load and BNC cable, S-S tuner (XT441)

THEORY:The electro magnetic field at any point of transmission line may be considered as

the sum of two traveling waves the “Incident wave”. Which propagates from the source to the load and the reflected wave, which propagates towards the generator, the reflected wave is set up by reflection of incident wave from a discontinuity in the line or from the load impedance .the superposition of the two traveling waves gives rise to a standing wave along the line. The maximum field strength is found where the waves are in phase and minimum where the two waves add in opposite phase. The distance between two successiveMinimum (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 voltage standing wave ratio (VSWR) is defined as ratio between maximum and minimum field strength along the lineHence VSWR denoted by S is as follows

S= Emax / Emin

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

Where Ei= incident voltageEr= reflected voltage

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Reflection co-efficient r is,r = Er /Ei = (ZL –Z0) / (ZL + Z0)Where, ZL is the load impedance

Z0 is Chara. ImpedanceThe above equation can be written as,

r = S-1 /S+1

PROCEDURE:

1. Set up the equipment as shown in fig. 2. Keep variable attenuator in the minimum attenuation position. 3. keep the controls knobs of VSWR Meter as below:

Range 40/50 dbInput switch low impedanceMeter switch NormalGain (Coarse- Fine) mid position approx

4. Keep the controls knob of Klystron power supply as below:Beam voltage OFFBeam voltage knob fully anticlockwiseReflector voltage knob - fully clockwiseAM- amplitude knob around fully clockwiseAM-freq & amp. Knob mid position

5. Switch ON the klystron power supply, VSWR meter and cooling fan.6. Switch ON the Beam voltage Switch position and set beam voltage at 300v7. Rotate the reflector voltage knob to get deflection in VSWR meter.8. Turn the out put by turning the reflector voltage, amplitude & frequency of AM

modulation9. Tune the plunger of klystron mount & probe for maximum deflection in VSWR

meter10. If required change the range DB s/w variable attenuation position & gain control

knob to get deflection in the scale of VSWR meter.11. As you move probe along the slotted line, the detection will change.

A. MEASUREMENT OF LOW & MEDIUM VSWR1 Move the probe along the slotted line to get maximum deflection in VSWR

meter.2 Adjust the VSWR meter gain control knob or variable attenuator until the meter

indicates 1.0 on normal VAWR scale.3 Keep the entire control knob, as it is, move the probe to next minimum position.

Read the VSWR on scale.4 Repeat the above step for change of s.s tuner probe depth & record the

corresponding SWR.

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5 If the VSWR is between 3.2 & 10, change the range DB s/w to next higher position & read the VSWR on second VSWR scale of 3 to 10.

B. Measurement of High VSWR1. Set the depth of S.S. tuner slightly more for maximum VSWR.2. Move the probe along with slotted line until a minimum is indicated.3. Adjust the VSWR meter gain control knob and variable attenuator to obtain a

reading of 3 db in the normal dB scale (0 to 10 dB) of VSWR meter.4. 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 d1.5. Repeat the step-3 and move the probe right along the slotted line until full scale

deflection is obtained on 0-10 db normal db scale. Let it be d2.6. Replace the S S tuner and termination by movable short.7. Measure the distance between two successive minima positions of the probe.

Twice this distance is guide wave length λg.8. Compute SWR from the following equation:

SWR = λg/ π (d1-d2)

CONCLUSION:

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AIM: To determine standing wave ratio & reflection co-efficient using Gunn power supply.

EQUIPMENTS: Gunn oscillator, gunn power supply, PIN modulator, isolator (XF621), frequency meter (XF710), variable attenuator (XA-520), detector mount, wave-guide stands, VSWR meter, Tunable Probe, cable and accessories, S-S tuner, termination (Xl400).

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

the sum of two traveling waves the “Incident wave”. Which propagates from the source to the load and the reflected wave, which propagates towards the generator, the reflected wave is set up by reflection of incident wave from a discontinuity in the line or from the load impedance .the superposition of the two traveling waves gives rise to a standing wave along the line. The maximum field strength is found where the waves are in phase and minimum where the two waves add in opposite phase. The distance between two successiveMinimum (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.

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Isolator Gunn Microwave Source

Variable attenuator

Frequency meter

Slotted line

Tunable probeV.S.W.R meter

S-S Tuner

Terminator

The voltage standing wave ratio (VSWR) is defined as ratio between maximum and minimum field strength along the lineHence VSWR denoted by S is as follows

S= Emax / Emin

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

Where Ei= incident voltageEr= reflected voltage

Reflection co-efficient r is,r = Er /Ei = (ZL –Z0) / (ZL + Z0)Where, ZL is the load impedance

Z0 is Chara. ImpedanceThe above equation can be written as,

r = S-1 /S+1

PROCEDURE:

1. Set up the equipment as shown in fig. 2. Keep variable attenuator in the minimum attenuation position. 3. keep the controls knobs of VSWR Meter as below:

Range 40/50 dbInput switch low impedanceMeter switch NormalGain (Coarse- Fine) mid position approx

4. Keep the controls knob of Gunn power supply as below:

Meter Switch - OFF Gunn bias knob- fully anti-clockwise Pin bias knob- fully anti-clockwise Pin mod frequency- any position

5. Switch ON the gunn power supply, VSWR meter and cooling fan.6. Switch ON the Beam voltage Switch position and set beam voltage at 10v7. Rotate the reflector voltage knob to get deflection in VSWR meter.

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8. Turn the output by turning the reflector voltage, amplitude & frequency of AM modulation

9. If required change the range DB s/w variable attenuation position & gain control knob to get deflection in the scale of VSWR meter.

10. As you move probe along the slotted line, the detection will change.

A. MEASUREMENT OF LOW & MEDIUM VSWR6 Move the probe along the slotted line to get maximum deflection in VSWR

meter.7 Adjust the VSWR meter gain control knob or variable attenuator until the meter

indicates 1.0 on normal VSWR scale.8 Keep the entire control knob, as it is, move the probe to next minimum position.

Read the VSWR on scale.9 Repeat the above step for change of S S tuner probe depth & record the

corresponding SWR.10 If the VSWR is between 3.2 & 10, change the range DB s/w to next higher

position & read the VSWR on second VSWR scale of 3 to 10.B. Measurement of High VSWR

1. Set the depth of S.S. tuner slightly more for maximum VSWR.2. Move the probe along with slotted line until a minimum is indicated.3. Adjust the VSWR meter gain control knob and variable attenuator to obtain a

reading of 3 db in the normal dB scale (0 to 10 dB) of VSWR meter.4. 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 d1.5. Repeat the step-3 and move the probe right along the slotted line until full

scale deflection is obtained on 0-10 db normal db scale. Let it be d2.6. Replace the S S tuner and termination by movable short.7. Measure the distance between two successive minima positions of the probe.

Twice this distance is guide wave length λg.8. Compute SWR from the following equation:

SWR = λg/ π (d1-d2)

CONCLUSION:

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Aim:- To study impedance measurement using klystron power supply.

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Impedance Matching Using Klystron Power supply

Equipments:-

Klystron tube 2k25, Klystron power supply 5KPS-610, Klystron mount XM-251, isolator XF62, frequency meter XF710, variable attenuator XA-520, slotted line, tunable probe XP655, VSWR meter, waveguide stand SU 535, SS tuner, Movable short terminator .

Theory:

The impedance any point on a transmission line can be written in form R+jX.For comparison SWR can be calculated,As s= (1+R) / (1-R) where R= (Z-Z0) / (Z+Z0).

Z0= characteristic impedance of w/g at operating frequency.

Z= load impedance.The measurement is performed in following way,The unknown device is connected in the slotted line and the position of one minima is determined. The unknown device is replaced by movable slot to the slotted line. Two successive minima position are noted. The twice of the difference between minima position will be guide wave length. One of the minima is used for the reference for

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impedance measurement. Find the difference of reference minima and minima position obtain from reference load. Let it be d. take a smith chart taking ‘1’ as a centre. Draw a circle radius to S. make a point on a circumference on a smith chart towards load site at a distance equal to‘d’. Join the center with this point. Find the point where it cut draw the circle. The co-ordinates of this point will show the normalize impedance of load. Procedure:-

1. Set the components and equipments as shown in fig.2. Set the variable attenuator at minimum position.3. Keep the control knob of VSWR meter as below:

Meter switch - normal positionRange - 50 db positionInput switch - crystal low impedanceGain(coarse Fine) - mid position

4. Keep the control knob of Klystron power supply as below:Beam voltage switch - ‘OFF’Mod switch - AMBeam voltage knob - fully anticlockwiseReflector voltage - fully clockwiseAM amplitude - Around fully clockwiseAM frequency knob - Around mid position

5. ‘ON’ the klystron power supply, VSWR meter and cooling fan.6. Switch ON the beam voltage switch position and set beam voltage at 300 V with

help of beam voltage knob.7. Adjust the reflector voltage knob to get some deflection in VSWR meter.8. Maximize the deflection with AM amplitude and frequency control knob of

power supply.9. Tune the plunger of klystron mount for maximum deflection.10. Tune the reflector voltage knob for maximum deflection.11. Tune the prob for maximum deflection in VSWR meter.12. Tune the frequency meter knob to get ‘dip’ on a VSWR scale and note down the

frequency directly from frequency meter.13. Keep the depth of S.S. tuner to round 3-4 mm and lock it.14. Move the prob along the slotted line to get maximum deflection.15. Adjust VSWR meter gain control knob and variable attenuator until the motor

indicate 1 on the normal SWR scale.16. Move the prob to next minima position and note down SWR S on the scale. Also

note down the probe position, let it be‘d’.17. Remove the SS tuner and match terminator and place movable short at slotted

line. The plunger of short should be zero.18. Note the two successive minima position. Let it be as d1 and d2.

Hence λg= 2 (d1-d2).19. Calculate (d / λg)20. Find out the normalize impedance as describe in the theory portion.21. Repeat the same experiment for other frequency required.

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CONCLUSION:-


AIM: To study the V-I characteristic of gunn diode.

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Gunn power supply

EQUIPMENT:Gunn oscillator, gunn power supply, PIN modulator, isolator, frequency meter, variable attenuator, detector mount, wave-guide stands, SWR meter, cable and accessories.

THEORY:The gunn oscillator is based on negative differential conductivity effects in bulk

semi-conductors, which has two conduction bands minima separated by an energy gap. A disturbance at the cathode gives rise to high field region, which travels towards the anode. When this high field domain reaches the anode, it disappears and another domain is formed at the cathode and starts moving towards anode and so on. The time required for domain to travel from cathode to anode gives oscillation frequency.

In a gunn oscillator, the gunn diode is placed in a resonant cavity. In this case the oscillation frequency is determined by cavity dimension than by diode itself.

Although gunn oscillator can be amplitude modulated with the bias voltage. We have used separate PIN modulator through PIN diode for square wave modulation.

A measure of the square wave modulation capability is the modulation depth, i.e., the output ratio between ‘ON’ and ‘OFF’ state.

PROCEDURE:22. Set the components and equipments as shown in fig.23. Initially set the variable attenuator for maximum attenuation.24. Keep the control knob of gunn power supply as below:

Meter switch ‘OFF”Gunn bias knob fully anti-clockwisePin bias knob fully anti-clockwisePin mod frequency any position

25. Keep the control knob of VSWR meter as below:Meter switch normalInput switch low impedanceRange db switch 40 dbGain control knob fully clockwise

26. Set the micrometer of gunn oscillator for required frequency of operation.27. ‘ON’ the gunn power supply, VSWR meter and cooling fan.

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Gunn oscillator

Isolator Pin modulator

TerminatorFrequency meter

Voltage-current characteristic1. Turn the meter switch of gunn power supply to voltage position.2. Measure the gunn diode current corresponding to the various voltage controlled

by gunn bias knob through the panel meter and meter switch. Do not exceed the bias voltage above 10 volts.

3. Plot the voltage and current readings on the graph as shown in fig.4. Measure the threshold voltage switch, which corresponds to maximum current.

Conclusion:

EXPERIMENT NO: 9 DATE:AIM : To study & measurement of gain & polar pattern of Horn antenna.

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EQUIPMENTS:Gunn power supply, isolator, gun oscillator, variable attenuator, VSWR meter, tunable probe, detector mount, pin modulator, frequency meter, two horn antenna, etc.

THEORY:

There are several methods to measure the gain of antenna; one method is to compare the unknown antenna with a standard gain antenna with known gain.

Another method is to use two identical antennas as transmitter and other as receiver. From following formula the gain can be calculated:

Pr = (PtG1G2 λ0)/ (4πs) 2

Pt = Transmitted power Pr = Received power G1, G2 = gain of transmitting and receiving antenna. S = radial distance between two antenna λ0 = free space wavelength If both transmitting and receiving antennas are identical having gain equal, then

Pr= (PtG2 λ0)/ (4πs) 2

G= (4πs /λ0) √ (Pr/Pt)In the above equation Pt, Pr, s and = can be measured and gain can be computed.Pr / Pt and be measured on VSWR.

GunnPower supply

Gunn oscilla-tor

IsolatorX1-621

Pin mod-ulator

Varria-ble attenut-orxa

Freq. meterXf 455

Dect mou-nt

VSWR meter

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PROCEDURE:GAIN MEASUREMENT:1. Set up the equipment as shown in fig.2. Keep the range db switch of VSWR meter at 50 db position with gain control.3. Energize the Gunn oscillator for the maximum output at desired frequency with

modulating amplitude and frequency of Gunn power supply and by tuning the detector.

4. Obtain full-scale detection in VSWR meter with variable attenuator.5. Now remove transmitting horn by detector mount and change the appropriate range

db position to get the deflection. Note and record the range db position and deflection of VSWR meter.

6. Calculate the difference in db between the power measured in step 4 & step 5.

Antenna Radiation Pattern Set up the equipment shown in fig. Energize the gunn oscillator for maximum output of frequency. By square wave

amplitude and frequency modulating signal of Gunn power supply. Also tune S.S Tuner in line of maximum output Obtain full scale detection and normal db scale at any convenient range switch

position of the VSWR meter by gain control knob of VSWR meter Turn the receiving from to the left in 2° to 5° set up to 40° - 50° and note the

corresponding VSWR db reading in normal db range when necessary change te range switch to some higher range and add 10 db to observe value,

Repeat this process for moving horn antenna in right and note down reading Draw the relative pattern

CONCLUSION :


AIM: To study Magic Tee by measuring input VSWR isolation & coupling factor.

32

STUDY OF MAGIC TEE :-

EQUIPMENT REQUIRED: Microwave source, Isolator, Variable attenuator, frequency meter slotted line,

Tunable probe, Magic Tee, Matched terminations, Detector mount, VSWR meter & Accessories.

THEORY:

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The device magic Tee is a combination of E & H plane Tee. Arm 3, the H-arm forms an H-plane Tee and arm 4, the E plane arm forms E-plane Tee in combination with arm 1 & 2 as side or collinear arms. If the power is fed into arm – 3 (H -arm) the electrical field divides equally between arm1 & arm 2 with same phase & no electric field exists in arm 4. Reciprocity demands no coupling in port 3. If power is fed in to the arm 4, it divides equally into arm 1 and arm 2 but out of phase with no power to arm 3. Further if the power is fed from arm 1 and arm 2. It is added in arm 3 and it is subtracted in E arm i.e. arm 4 refer to shape.

The basic parameters to be measured for magic Tee are defined below.(1) Input VSWR : Value of SWR corresponding to each port, as a load to the line while

other parts are terminated in matched load.(2) Isolation : The isolation between E and H arms is defined as the ratio of power

supplied by the generator connected to E-arm (part 4) to the power detected at H-arm (part 3). Side arms 1 and 2 are terminated in matched load.

Hence Isolation 3-4 = 10 log10 (P4/P3)Similarly isolation between other parts may also be defined.

(3) Coupling Co-efficient: It is defined as Cij= 10^(-/20), where =10 log (Pi /Pj)

Pi is the power delivered to arm i. Pj is the power detected at j arm

PROCEDURE:

(1) VSWR measurement of ports:1. Set up the component & equipments as shown in the fig. Keeping E- arm towards

slotted line and matched termination to other ports2. Energize the microwave source for particular frequency of operation.3. Measure the VSWR of E arm as described in measurement of SWR for low and

medium value.4. Connect the other port with matched termination. Measure the VSWR as above.

In the same way VSWR of any port can be measured.(2) Measurement of Isolation and coupling coefficient:

1. Remove the tunable probe and Magic Tee from the slotted line & connect the detector mount to slotted line.

2. Energize the microwave source for particular frequency of operation & tune the detector mount for maximum output.

3. With the help of variable attenuator & gain control knob of VSWR meter set any power level in VSWR meter & note down. Let it be P3.

4. Without disturbing the position of variable attenuator & gain control knob, carefully place the magic tee after slotted line keeping H-arm to slotted line, detector to E-arm & matched termination to arm 1& 2. Note down the reading of VSWR meter. Let it be P4.

5. Determine isolation between port 3 & 4 as P3- P4 in dB.6. Find coupling coefficient from equatio0n given in the theory part.7. The same experiment may also be repeated foe the other ports also.8. Also repeat the same experiment for different frequencies also.

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CONCLUSION:-

EXPERIMENT NO: 11 DATE:AIM: To study function of multi hole directional coupler by measuring the following parameters

(1) Main line and auxiliary line VSWR.(2) Coupling factor and directivity of coupler.

35

36

Gunn power supply

Gunn oscillator

Pin modulator

Isolator Variable attenuator

Freq meter Directional

coupler

Matched termination

Detector mount

Detectoror mount

VSWR meter

Matched termination

Dector mount

Direction coupler

Dector mountMatched termination

Directional coupler

EQUIPMENT: Microwave source, Gunn diode, isolator, gun oscillator, variable attenuator, VSWR meter, tunable probe, detector mount, matched terminator and wave guide stand.

THEORY: A directional coupler is a device with which it is possible to measure the incident and

reflected wave separately. It consists of two-transmission line. The main arm and auxiliary arm electromagnetically coupled to each other.

The coupling factor = 10 log (P1 / P3) where port P4 is terminated with built in termination and power is exerting at port P1.

The directivity of coupler is measure of separation between incident wave and reflected wave,

Hence directivity D(db) =10 log(P3f /P3R) Where P3F & P3R is power measure at port 3 with equal amount of power fed to the

port 1 and port 2. Main insertion loss is the attenuation introduced in transmission line by insertion of coupler.

Insertion loss = 10 log (P1 /P2) where power is entering from port 1. Isolation is defined as ration of the incident power Pi to the back power Pb is

expressed in db, I = 10 log (Pi / Pb) db.

PROCEDURE:

37

Main line SWR Measurement: Set up the equipments as shown in the fig. Energize the microwave source of particular frequency of operation as described

in the procedures given in the operation of gunn oscillator Follow the procedure as described for VSWR measurement. Repeat the same for other frequencies.

Auxiliary Line SWR Measurement: Set up the equipments as shown in the fig. Energize the microwave source of particular frequency of operation as described

in the procedures given in the operation of gunn oscillator Follow the procedure as described for VSWR measurement. Repeat the same for other frequencies

Measurement of coupling factor, insertion loss, isolation & Directivity: Set up the equipment shown in fig. Energize the microwave source for particular operation of frequency. Remove the directional coupler as shown in fig 1 with detector to the auxiliary

port 3 and matched termination to port 2, without changing the position of variable attenuator and gain control knob of VSWR meter.

Note the reading of VSWR meter on the scale with help of range db switch if required let it by.

So coupling factor X-Y in db. Now carefully disconnect the detector from the auxiliary port 3 and match

termination from port 2 without disturbing the step up. Connect the matched termination to auxiliary port 3 and detector to port 2 and

measure reading on VSWR meter let say Z. So insertion loss = X-Z db.

Now connect the directional coupler in reverse position i.e. port 2 to frequency meter side, matched termination to port 1and detector mount to port 3 without disturbing the position of variable attenuator and gain control knob of VSWR meter.

Measure and note down the reading on VSWR meter let it be Y0. Complete the directivity as (Y-Y0) db. Complete isolation loss as (X-X0) db.

CONCLUSION:

38


AIM: To study the isolator by measuring input VSWR, insertion loss & isolation.

Measurement of VSWR of Isolator:-

39

M EASUREMENT OF INSERTION LOSS & ISOLATION OF ISOLATOR :-

EQUIPMENT:

40

Microwave source, Isolator, Frequency Meter, Variable Attenuator, Slotted line, Tunable probe, Detector mount, VSWR meter, Test isolation accessories

THEORY:An isolator two port device that transfers energy from input port to output

port with little attenuation and from output port to input port with very high attenuation.The isolator shown in the figure can be derived from three-port circulator by simply placing a matched load (reflection less termination) on port.

The important isolator parameters are as follows(1) Insertion loss : insertion loss is the ratio of power detected at the output port to the

power supplied by source to the input port, measured with other ports terminated in the matched load. It is expressed in dB.

(2) Isolation : Isolation is the ratio of power applied to the output to that measured at the input. This ratio is expressed in dB.

(3) Input VSWR : The input VSWR of an isolator is the ratio of voltage maximum to voltage minimum of the standing wave existing in the line with all ports except the test port is matched.

PROCEDURE:

(1) INPUT VSWR Measurement:-1. Setup the components & equipments as shown in fig.1 with input port of isolator

towards slotted line and match load on other ports of it.2. Energize the microwave source for particular operation of frequency.3. With the help of slotted line, probe and VSWR meter, find out SWR of the

isolator as described earlier for low and medium SWR measurement.4. The above procedure can be repeated for other ports or for other frequency.

(2) Measurement of Insertion and Isolation:-1. Remove the probe and isolator from slotted line and connect the detector mount to

slotted section. The output of the detector mount should be connected with VSWR meter.

2. Energize the microwave source for max. Output for a particular frequency of operation. Tune the detector mount for maximum output in VSWR meter.

3. Set any reference level of power in VSWR meter with the help of variable attenuator and gain control knob of meter let it be P1.

4. Remove the detector mount from slotted line without disturbing and position of setup. Insert the isolator between slotted line and detector mount. Keeping input port to slotted line and detector as its output port.

5. Record reading in VSWR meter. If necessary change range db switch to high or lower position and taking 10 db changes for one step change of switch position let it be P2.

6. Compute insertion loss on P1-P2 in db.

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7. For measurement of isolation, the isolator has to be connected reverse, i.e. output port with other port termination by matched termination after setting a reference level without isolator in setup as described in insertion loss measurement. Let same P1 level is set.

8. Record the reading of VSWR meter inserting the isolator as given in step 7, let it is P3.

9. Compute isolation as P1-P3 in db.10. Repeat the above experiment for other frequency if needed.

CONCLUSION:

EXPERIMENRT NO: 13 DATE

AIM: To study circulator by measuring input VSWR, insertion loss & isolation.

Measurement of VSWR of Circulator:-

MEASUREMENT INSERTION LOSS, ISOLATION OF ISOLATOR AND COLLECTOR

42

EQUIPMENT:Microwave source, Isolators, Circulators, Frequency meter, Variable attenuator,

Slotted line, Tunable probe, Detector mount, VSWR meter, Test isolation and circulation and accessories.

THEORY:

.

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Klystron oscillator

Isolator XI 621

Frequency meter (XF710)

Variable attenuator

Slotted line XL-451

Detector mount

V.S.W.R. meterSW-115

Circulator Detector mount



Matched load XL-400

Klystron power supply

CirculatorThe circulator is a multi port junction that permits transmission in certain ways.

For example if we r having a three port circulator then a wave incident in port1 will be coupled to port2 only, a wave incident at port2 is coupled to port3 only. Following is the basic parameters of isolator and circulator for study.

(a) Insertion Loss: The ratio of power supplied by a source to the input port to the power detected by a detector in the coupling arm, i.e., output arm terminated in the matched load, is defined as insertion loss or forward loss.

(b) Isolation: It is the ratio of power fed to input arm and the power detected at not coupled port with other port other terminated in the matched load.

(c) Input VSWR: The input VSWR of an isolator or circulator is the ratio of voltage maximum to the voltage minimum of the standing wave existing on the line, when one port of it terminates the line and other have matched termination.

PROCEDURE:

(a) Input VSWR Measurement1. Set up the components and equipments as shown in Fig. with input

port of circulator towards slotted line and matched load on other ports of it.

2. Energize the microwave source for particular operation of frequency.3. With the help of slotted line, probe and VSWR meter, find out SWR of

the isolator or circulator as described earlier for low and medium SWR measurements.

4. The above procedure can be repeated for other ports or for other frequencies.

(b) Measurement of Insertion Loss and Isolation 1. Remove the probe and circulator from slotted line and connect the

detector mount to the slotted section. The output of the detector mount should be connected with VSWR meter.

2. Energize the microwave source for maximum output for a particular frequency of operation. Tune the detector mount for maximum output in the VSWR meter.

3. Set any reference level of power in VSWR meter with the help of variable attenuator and gain control knob of VSWR meter. Let it be P1.

4. Carefully remove the detector mount from slotted line without disturbing and position of set up. Insert the isolator/ circulator between slotted line and detector mount. Keeping input port to slotted line and

44

detector at its output port. A matched termination should be placed at third port in case of circulator.

5. Record the reading in the VSWR meter. If necessary change range db switch to high or lower position and taking 10 db change for one step change of switch position. Let it is P2.

6. Computer insertion loss on P1-P2 in db.7. For measurement of isolation, the circulator has to be connected

reverse, i.e., output port to slotted line and detector to input port with other port terminated by matched termination (in case circulator) after setting a reference level without circulator in the set up as described in insertion loss measurement. Let same P1 level is set.

8. Record the reading of VSWR meter inserting the circulator as given in step 7, let it is P3.

9. Compute isolation as P1-P3 in db.10. The same experiment can be done for other ports of circulator.11. Repeat the above experiment for other frequencies if needed.

CONCLUSION:

EXPERIMENT NO:14 DATE:

AIM: To study attenuators (fixed & variable both) by measuring i/p VSWR & insertion

loss.

INSERTION LOSS AND ATTENUATION MEASUREMENT OF ATTENUATOR

45

Klystron oscillator

Isolator XI-621

Frequency meter (XF-710)

Variable attenuator

Slotted line XD

451

Detector mount

V.S.W.R meter SW-115

Klystron power supply

= Power P1

= Power P2

EQUIPMENT:Microwave source, Isolator, Frequency meter, Variable attenuator, Slotted line,

Tunable probe, Detector mount, Matched termination, VSWR meter, Test fixed and variable attenuator and Accessories.

THEORY:The attenuators are two-port bi-directional device, which attenuates some power

when inserted into the transmission line.Attenuation A (db) = 10 log (P1/P2)Where, P1 = power absorbed or detected by the load without the attenuator in the

line. P2 = power absorbed or detected by the load with the attenuator in the line.

The attenuators consist of a rectangular wave-guide with a resistive vane inside it to absorb microwave power according to their position with respect to sidewall of the wave-guide. An electric field is maximum at center in TE10 mode; the attenuation will be maximum if the vane is placed at the center of the wave-guide. Moving from center towards the sidewall, attenuation decreases in the fixed attenuator, the vane position is fixed where as in variable attenuator, its position can be changed by the help of micrometer or by other methods.

Following characteristics of attenuators can be studied:1. Input VSWR.2. Insertion loss (in case of variable attenuator)3. Amount of attenuation offered into the lines.4. Frequency sensitivity, i.e., variation of attenuation at any fixed

position of vane and frequency is changed.

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Attenuator Detector mount

PROCEDURE:(a)Input VSWR Measurement

1. Connect the equipments as shown in fig.2. Energize the microwave source for maximum power at any

frequency of operation.3. Measure the VSWR with the help of tunable probe, Slotted line

and VSWR meter as described in the experiment of measurement of low and medium VSWR.

4. Repeat the above steps for other frequencies if required.(b)Insertion Loss/Attenuation Measurement

1. Remove the tunable probe, attenuator and matched termination from the slotted section in the above set up.

2. Connect the detector mount to the slotted line, and tune the detector mount also for the maximum deflection in the VSWR meter.

3. Set any reference level on the VSWR meter with the help of variable attenuator and gain control knob of VSWR meter. Let it be P1.

4. Carefully disconnect the detector mount from the slotted line, without disturbing any position on the set up. Place the test variable attenuator to the slotted line and detector mount to the other port of the test variable attenuator. Keep the micrometer reading of test variable attenuator at zero and record the reading of VSWR meter. Let it be P2. Then the insertion loss of the test attenuator will be P1-P2 db.

5. For the measurement of attenuation of fixed and variable attenuator, after step 4 of above measurement, carefully disconnect the detector mount from the slotted line without disturbing any position obtained up to step 3. Place the test attenuator to the slotted line and detector mount to the other port of test attenuator. Record the reading of VSWR meter. Let it be P3. Then the attenuation value of fixed attenuator or attenuation value of variable attenuator for particular position of micrometer reading will be P1-P2 db.

6. In case of variable attenuator, change the micrometer reading and record the VSWR meter reading. Find out attenuation value for different position of Micrometer reading and plot the graph.

7. Now change the operating frequency whole step should be repeated for finding frequency sensitivity of fixed and variable attenuator.

CONCLUSION:

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mwe lab manual final

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