manual of rf and microwave -new (14 exps)

8/19/2019 Manual of RF and Microwave -New (14 Exps)

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FOUNDATION UNIVERSITYRAWALPINDI CAMPUS

ELECTRICAL ENGINEERINGDEPARTMENT

(EXPERIMENT MANUAL)

RF & Microwave Engineering Lab


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Table of Contents

EXPERIMENT # 1: THE GUNN OSCILLATOR ............................................................................................... 3

EXPERIMENT # 2: SQUARE WAVE MODULATION ..................................................................................... 6

EXPERIMENT # 3: SQUARE LAW CHARACTERISTICS OF A CRYSTAL DETECTOR ....................................... 8

EXPERIMENT # 4: PROPAGATION MODES, WAVELENGTH AND PHASE VELOCITY IN WAVEGUIDE ....... 10

EXPERIMENT # 5: MEASUREMENT OF Q USING THE POWER MEASUREMENT TECHNIQUE .................. 12

EXPERIMENT # 6: MEASUREMENT OF Q USING SWR METER................................................................. 14

EXPERIMENT # 7: DIRECT POWER MEASUREMENT ................................................................................ 15

EXPERIMENT # 8: MEASUREMENT OF CONJUGATE AND ZO POWER..................................................... 17

EXPERIMENT # 9: MEASUREMENT OF LOW AND MEDIUM RANGE SWR. .............................................. 19

EXPERIMENT # 10: MEASUREMENT OF HIGH RANGE SWR. ................................................................... 21

EXPERIMENT # 11: IMPEDANCE MEASUREMENT ................................................................................... 22

EXPERIMENT # 12: BASIC PROPERTIES OF DIRECTIONAL COUPLER ....................................................... 24

EXPERIMENT # 13: ATTENUATION MEASUREMENT ............................................................................... 27

EXPERIMENT # 14: STUDY OF A WAVEGUIDE HYBRID-TEE ..................................................................... 30


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Foundation University

Rawalpindi ampus (FURC) Electrical Engineering Department

EXPERIMENT # 1: THE GUNN OSCILLATOR

Objective:

The objectives of this experiment are to obtain the knowledge on the theory and the operation

of the Gunn oscillator as a source of microwave frequency.

List Of Equipment:

Power supply, Gunn Oscillator, variable attenuator, waveguide to coax adapter, thermocouple

mount, power meter, frequency meter, ammeter, voltmeter and coaxial cable with connector.

Procedure:

Part A: Current vs. Voltage Characteristics

[1] Set the equipment as shown.

[2] Set the voltage to 4V. Set the variable attenuator to 10dB. This will ensure proper isolation

to the gun isolator.

[3] Raise the voltage to 0.5V increment. Measure and record the current each time in the table

(do not exceed 10V).

[4] Construct the V-I curve as suggested.

Supply

voltage(V)

4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

Supply

current(mA)


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Part B: Measurement of Oscillator output Power vs. Supply Voltage

[1] Turn the power meter ON calibrate the power meter to zero.

[2] Raise the Gunn diode voltage in 0.5V increment and record the power indication on the

power meter and the attenuator setting.

[3] Convert the obtained power meter reading in milliwatts to dBm. Then add the attenuation

(dB) to the dBm.

[4] Repeat the step 3 and complete the table

Supply voltage

(V)

Power meter

reading(mW)

Converted

power(dBm)

Attenuator

setting(dB)

Gun diode

output(dBm)

Gunn diode

output(mW)

4

4.5

5

5.5

6

6.5

77.5

8

8.5

9

9.5

10

[5] Draw a graph showing the relationship between supply voltage and the output power.

Part C: Measurement of Oscillator Output Frequency vs. Supply Voltage.

[1] Setup the equipment as shown.

[2] Set the supply voltage to 9V. Set the attenuator to maximum attenuation. Switch the power

meter to 1.0 range.

[3] Reduce the attenuation until the power meter reading is close to the right side of the meter

scale (Approx. 0.8-1mw). Slowly turn the frequency meter. Observe a dip on the power


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meter when the frequency of the frequency meter is exactly same as the frequency of the

Gunn oscillator.

[4] From the lowest supply voltages at which oscillation occur to the maximum of 10V supply

voltage, vary the voltage in an increment of 0.5V.

[5] Repeat from [3] by varying the voltage. Each time, fill in the table. Notice that the frequency

meter is calibrated in 10MHz increment.

Supply

voltage(V)

7.5 8 8.5 9 9.5 10

Measured

frequency(GHz)


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EXPERIMENT # 2: SQUARE WAVE MODULATION

Objective:

Learn the basic theory and operation of the PIN diode modulator.

Learn the basic theory and operation of the crystal detector.

List of Equipment:

Gunn oscillator, PIN modulator, crystal detector, variable attenuator, fixed attenuator,

waveguide to coax adapter, power supply, coaxial cable with connector, square wave generator,

thermocouple mount, oscilloscope, SWR meter, power meter.

Procedure:

Part A: Square Wave Modulation

[1] Set up equipment as shown in figure.

[2] Apply 9V to the Gunn oscillator.

[3] Set the variable attenuator to 10dB.

[4] Adjust the square wave generator to 1 KHz and 2Vp-p output. Connect the generator to the

pin modulator.

[5] Adjust the scope so that the top of the square wave aligns to the zero level on the screen.

[6] Adjust the attenuator so that the bottom of the square wave aligns to the zero level on the

screen.

[7] Repeat above measurements for 1Vp-p negative square wave.


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[8] Calculate the modulation depth for the two modulation inputs of 2Vp-p 1Vp-p and using the

following equations

A dB=20 log ( )

Where A is the difference in the attenuator settings between step (3) and step (6).

m=

Where m is the modulation depth.

As one can see from above figure the attenuator setting deviation A can be expressed

as;

A dB=10 log ( ) =20 log ( )

Att Vmax Vmin A ㏈ M 2Vp-p, 1KHz

Att Vmax Vmin A ㏈ M 1Vp-p, 1KHz


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EXPERIMENT # 3: SQUARE LAW CHARACTERISTICS OF A CRYSTAL DETECTOR

Part B: The Square Law Characteristics of a Crystal Detector.

[1] Setup the equipment as shown in figure.

[2] Calibrate the power meter to zero at X0.1 range. Observe the meter for a few

minutes. Make sure the calibration is maintained.

[3] Apply 9 volts to the Gunn oscillator. Also apply 1Vp-p & 1 KHz square wave to the

pin modulator. At this point, modulation should take place.

[4] Set the variable attenuator to 0. The power meter should indicate between

0.002-0.15mw. Referring to the conversion table, change mW reading to dBm.

As shown in figure, replace the waveguide to coax adapter, the thermocouple mount

and the power meter with a crystal detector and a SWR indicator. Adjust the

m

o

d

u

l

at

i

o

n frequency and range such that the deflection of SWR meter is maximized.


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[5] Select a range on the SWR meter. Adjust the gain control to the SWR meter to

obtained convenient reading on the dB scale. Once the range and the gain control

are set, do not touch the gain control.

[6] Vary the attenuator setting up to 20 dB in 1 dB increment. At each step, record theSWR meter deflection (in dB) and the gain range.

A dB Input power SWR indicator

(mW) (dBm) Deflection(dB) Range(dB)

0

1

2

3

4

56

7

8

9

10

11

12

13

14

1516

17

18

19

20


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EXPERIMENT # 4: PROPAGATION MODES, WAVELENGTH AND PHASE

VELOCITY IN WAVEGUIDE

Objective:

Learn the theory of waveguide.

Experiment the propagation characteristics of microwave in free space as well as in waveguide.

List of Equipment:

Gunn oscillator, slotted line, PIN modulator, variable attenuator, frequency meter, straight wave

guide, reflector with stand, power supply, coaxial cable with connector, square wave generator,

SWR meter.

Procedure:

Part A: Frequency Measurements.


[2] Apply 9V to the Gunn oscillator. Also apply 1 KHz, 2Vp-p square wave to the pin modulator.

[3] Adjust the variable attenuator to 10dB. Set the SWR meter such that the meter indicates

approximately the middle of the scale.

[4] Adjust the frequency of the square wave generator so that the SWR indication is maximized.


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[5] Turn the frequency meter until there is a significant drop on the SWR indicator. Record the

frequency in the table.

Frequency(GHz) 9.980

Measured 39mm

Measured g 40mm

Calculated 30mmCalculated g 37mm

Part B: Measurement of Free Space Wavelength and Guide Wavelength

[1] When the reflecting sheet is moved toward the open end of waveguide, with the reflecting

sheet oriented to the waveguide right-angle, then the standing wave pattern should vary

due to the reflection from the plate. This variance of the standing waves is detected by the

probe in the slotted line. Find two adjacent positions where the two detected values are

minimum. The distance between these two points corresponds to the half wavelength in

free space. Record the distance in the table. [2] Cover the output of the slotted line with the shorting plate. Vary the slotted line and locate

a position where detected output voltage is minimum. From that point, find another

adjacent point where a minimum is detected again. The distance between two points is the

half of the guide wavelength. Record the values in the table.


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EXPERIMENT # 5: MEASUREMENT OF Q USING THE POWER MEASUREMENT

TECHNIQUE

Objective:

Learn the theory of a resonance cavity.

Experiment the relation between Q and bandwidth.

Learn how to measure the Q of a resonance cavity.

List of Equipment:Gunn oscillator, PIN modulator, crystal detector, frequency meter, variable attenuator, fixed

attenuator, waveguide to coax adapter, power supply, coaxial cable with connector, square

wave generator, thermocouple mount, SWR meter, power meter.

Procedure:

Part A: Measurement of Q Using the Power Measurement Technique.


[2] Apply 9V to the Gunn oscillator. Set the range switch of power meter to x1mw. The variableattenuator should be at 10dB and then adjust frequency meter for the maximum power

meter deflection. Refer this value as Po.

[3] Turn the frequency meter slowly and find the power and frequency reading when the power

meter reading is minimized. Call these values PB for power and FO for frequency.


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[4] Slowly rotate the frequency meter. Find two frequencies

(F1 & F2) where the power reading equals to (PB + ∆P/2).

Variable Power PB fo ∆ P f1 f2 attenuator meter


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EXPERIMENT # 6: MEASUREMENT OF Q USING SWR METER

Part B: Measurement of Q Using SWR Meter


[2] Apply 9V to the Gunn oscillator and set the attenuator to 10dB.

[3] Apply 1 KHz & 1Vp-p to the PIN-Diode modulator.

[4] Adjust the range switch and the gains adjust to obtain 0dB on the SWR meter.

[5] Slowly rotate the frequency meter. Find the point where the SWR meter reading is

minimum. Note the reading on dB-scale and call it P.[6] Plug-in the value obtained from (4) into the following equation to get the ratio PB.

P dB=10 log ( )

[7] Since ∆P=1 –PB,

Calculate PB + and Convert it into dB

X dB=10 log ( )

[8] Slowly rotate the frequency meter and find F1, F2 and ∆F where the SWR meter reading

indicates X dB as calculated above.

PdB PB ∆P XdB F1 F2


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EXPERIMENT # 7: DIRECT POWER MEASUREMENT

Objective:

Learn different ways of measuring power.

Learn how to evaluate the accuracy of the power measurements.

List of Equipment:

Gunn oscillator, slide screw tuner, PIN-diode modulator, crystal detector, variable attenuator,

terminator, directional coupler, waveguide to coax adapter, power supply, coaxial cable with

connector, square wave generator, thermocouple mount, power meter, SWR meter.

Procedure:

Part A: Direct Measurement.


[2] Without the signal activated, set the range to x1mW and adjust the meter to zero.

[3] Turn on the Gunn oscillator. Adjust the variable attenuator to 3dB. Read the power meter

and record the reading.

Attenuator

Power meter reading


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Part B: Power Measurement Using a Directional Coupler


[2] Do not alter settings on the power supply, Gunn oscillator and the variable attenuator. Take

the reading of the power meter.

AttenuatorPower meter reading


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EXPERIMENT # 8: MEASUREMENT OF CONJUGATE AND ZO POWER

Part C: Measurement of Conjugate and Z0 Power


[2] Set the variable attenuator to 3 db. Modulate the output of directional coupler with square

wave of 1 kHz & 1Vp-p.adjust the pulse frequency to minimize the SWR meter.

[3] Do not change the signal power level. Adjust the slide screw tuner for the minimum

indication on the SWR meter. Use the most sensitive range of SWR meter.

[4] Record the reading on the power meter.

[5] Adjust the slide screw tuner to get the maximum indication on the power meter. Record the

reading.

Attenuator

Zo powerConjugate power

Part D: Modulated Signal

[1] Setup equipment as shown.


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[2] Adjust the variable attenuator to 10dB.

[3] Adjust the output of pulse generator to 0Vp-p. Offset the output by +0.5V. Observe the

power meter and record the meter reading.

[4] Adjust the output of the pulse to 2Vp-p. Set the offset 0V. Record the power meter reading.

[5] Replace the thermocouple mount and the power meter with crystal detector. Connect

oscilloscope to the crystal detector. Adjust the vertical position of the scope to align the top

of the square wave to the zero level on the screen. The reason for this adjustment is thatthe output of the crystal detector is negative. Therefore, the power at the top of the pulse is

actually less than the power at the bottom of the pulse.

[6] Reduce the attenuation of the attenuator until the bottom of the square wave lines up with

the zero level of the scope. Record the change in attenuation.

Attenuator Power meteroutput

Power meteroutput

Top oscilloscopelevel

Top oscilloscopelevel

Part E: The dB-Scale.

[1] Repeat the setup of figure of part-A with the variable attenuator at 20dB.

[2] Vary the attenuator as in table. At each time record the power meter reading. When the

meter switched to a new range, make sure the meter is properly zeroed.

Attenuator

setting(dB)

5 8 10 12 15 20

Power meter

reading(mW)


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EXPERIMENT # 9: MEASUREMENT OF LOW AND MEDIUM RANGE SWR.

Objective:

Learn how to measure SWR using slotted line and SWR indicator.

List of Equipment:

Gunn oscillator, slide screw tuner, slotted line, PIN modulator, variable attenuator, terminator,

power supply, coaxial cable with connector, square wave generator, SWR meter.

Procedure:

Setup equipment as shown.

Set the Gunn diode supply voltage to +9V, do not exceed this value.

Set the variable attenuator to 10dB.

Apply 1 KHz & 1Vp-p to the PIN-Diode modulator.

Set the SWR indicator range switch to 20-40dB. Turn on the indicator.

Turn on the Gunn oscillator.

Apply the modulation signal to pin diode modulator. Adjust the SWR indicator frequency for the maximum meter deflection (toward right 1.0).

Part A: Measuring Low and Medium Range SWR.

[1] Move the probe of slotted line and observe the SWR indicator meter deflection.

[2] Completely disengage the probe of slide screw tuner. At this point, the VSWR indication

should be very small (less than 1.3). Therefore, use the expanded scale for better reading.


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[3] Move the probe in the slotted line until a maximum deflection is observed in the SWR

indicator. Adjust the gain of SWR indicator until the expanded meter reading reaches 1.0.

Both coarse and the fine gain adjust are needed in the expanded scale.

[4] Move the probe to where a minimum deflection is observed. Take the reading on the

expanded scale and record it in the table.

[5] Repeat the above procedure with three different probe depths. The three different probe

depths are required to be greater than the depth used in the above procedure.

Probe depth(mm)

VSWR

Part B: Measuring High Range SWR

[1] Maximize the depth of the probe of the slide screw tuner. Large depth of the probe is

necessary for high SWR measurement.

[2] Move the probe along the slotted line until a minimum is observed on the indicator.

[3] Adjust the gain of the indicator until 3dB is shown on the dB scale. If necessary, reduce theattenuation of the variable attenuator.

[4] Move the probe along the slotted line until 0dB (full scale) is obtained on the dB scale.

[5] Record the position of the probe under the D1 column in the table.

Probe penetration D1(mm) D2(mm) 1st

min(mm)

2nd

min(mm)g(mm) SWR

[6] Repeat the above procedure while moving the probe toward the right and record the

position of the probe under the D2 column. Repeat the measurement at three different

probe depths.

[7] Replace the slide screw tuner with a shorting plate. Find the distance between two adjacent

minimums. The guide wavelength (∏g) is twice of the distance.

[8] Compute the SWR using the following formula:

SWR= =


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EXPERIMENT # 10: MEASUREMENT OF HIGH RANGE SWR.

Part C: Measuring High SWR Using a Calibrated Attenuator

[1] Maximize the probe depth of slide screw tuner.

[2] Move the probe along the slotted line until a minimum is observed.

[3] Set the variable attenuator to 10dB. (Call this value A1). Adjust the gain of SWR indicator

until 3dB attenuation is observed.

[4] Move the probe along the slotted line and adjust the attenuator until the same maximum

value as in the previous step. Read the dB value (call this value A2) and record it.

Probe penetration A1(dB) A2(dB) SWR

[5] Calculate the SWR using the following formula and fill in the table

S=10(

Repeat the procedure at the different probe depths.


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EXPERIMENT # 11: IMPEDANCE MEASUREMENT

Objective:

Learn smith chart and its application in determining unknown impedance.

List of Equipment:

Gunn oscillator, slide screw tuner, slotted line, PIN modulator, frequency meter, variable

attenuator, terminator, power supply, coaxial cable with connector, square wave generator,

SWR meter.

Procedure:

Part A: Basic Measurement.

[1] Setup equipment as shown.

[2] Completely unscrew the probe.


[4] Apply 1 KHz &1Vp-p modulation signal to the pin modulator.

[5] Variable attenuator should be 2dB.

[6] Measure the maximum and minimum value on the SWR indicator. Also measure thefrequency of the oscillator.

Part B: Impedance Measurement

[1] Observe the SWR indicator deflection (maxima & minima) at the 40dB range. Take the

reading.


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[2] Bring the probe of the slide screw tuner into the device such that the depth of the probe is

approximately 5mm.

[3] Move the probe using along the slotted line until a maximum deflection is observed on the

SWR indicator.

[4] Adjust the SWR indicator until the meter indicates 1.0.

[5] Move the probe along the slotted line until minimum deflection is observed. Record the

SWR value (SL) and the depth of the probe (dL) in the table

Probe

penetration(mm)

Load

SWR(SL)

Load

min dL

(mm)

Short minima

ds1(mm)

ds2(mm)

g=2(ds1-

ds2)

(mm)

(dL-

(ds1))/

g

Load

impedance

Frequency : 9.960 GHz

Note: In the following measurement, in case (dL-ds1) turn out to be positive, move probe

toward the generator. If the value is negative move it toward the load. Also note that

(" Is always less than 0.25.

[6] Remove the slide screw tuner and the matched termination from the setup. Place a shorting

plate to the slotted line.

[7] Obtain the distance ds1 and ds2 which correspond to two adjacent minimum VSWRs. The

guide wavelength obtained ∏g is 2(ds1-ds2).

Note: when measuring the minimum, it may be helpful to increase the gain of SWR indicator

to obtain better frequency.[8] Repeat the procedure for two more different probe depths.


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EXPERIMENT # 12: BASIC PROPERTIES OF DIRECTIONAL COUPLER

Objective:

Learn the basic properties of a directional coupler including the coupling coefficient and the

directivity.

List of Equipment:

Gunn oscillator, slide screw tuner, PIN modulator, frequency meter, variable attenuator, fixed

attenuator, terminator, power supply, coaxial cable with connector, square wave generator,

SWR meter, crystal detector, waveguide .

Procedure:

Part A: Coupling Factor Measurement

[1] Setting up the equipment as shown.

[2] Set the variable attenuator to 20dB. Apply 1000pps modulation signal to pin diode

modulator and turn on the Gunn oscillator. Read the SWR indicator. Use this value as a

reference. Fill in the table.

[3] Replace the waveguide with the directional coupler as shown in figure.


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Move the crystal detector to the auxiliary arm of the coupler.

A1(dB) A2(dB) A3(dB) A1-A2(dB) A4(dB) (A3-A4) + n x10 (dB)

[4] Adjust the variable attenuator until the same reference reading as in [1] is obtained.

[5] Fill the table A2 with the attenuation of the attenuator. The coupling factor of the

directional coupler is A1-A2.

Part B: Directivity Measurement.

[1] Set the attenuator to 20dB.

[2] Read the SWR indicator. Use this value as a reference. Record the attenuator setting (20dB)

in table A3.

[3] Change the coupler orientation as specified in figure.

[4] Reduce the attenuation and increase SWR indicator gain by 10dB or 20dB (in 10dB steps)

until the same value in [2] is obtained. Fill in the table with A4 as attenuation of the

attenuator. The directivity is [(A3-A4) + n*10] (dB).


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Part C: Return Loss Measurement of a Load.

[1] Set up the equipment as shown.

[2] Set up probe depth of the slide screw tuner to 5mm.

[3] Set up attenuator to 0(dB) (A5). Read the SWR indicator. Use this as a reference.

[4] Change the attenuator to a maximum attenuation. Replace the load with a short.

[5] Decrease the attenuation until the reference level in [3] is obtained record the attenuator

position (A6). In case it is necessary to change the range on the SWR indicator, add the

increased value to the position of the attenuator to get A6.

[6] The return loss = ((A6-A5) + n x10) dB

A5 (dB) A6 (dB) ((A6-A5) + n*10) (dB) SWR

Where

=


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EXPERIMENT # 13: ATTENUATION MEASUREMENT

Objective:

Learn attenuation measurement techniques of microwave components.

List of Equipment:

Gunn oscillator, slotted line, PIN modulator, crystal detector, variable attenuator, fixed

attenuator, terminator, directional coupler, power supply, coaxial cable with connector, square

wave generator, SWR mete, shorting plate.

Procedure:

Part A: Preliminary Adjustment.


[2] Turn the power supply ON.

[3] Apply 1000pps modulation signal to pin diode.

[4] Adjust either the pulse repetition rate or the frequency on the SWR indicator for the

maximum deflection on the SWR meter.

Part B: Measurement Using the Power Ratio Method.


[2] Set the SWR gain indicator to either 30dB or 40dB range and adjust the indicator for 0dB.

[3] Using a directional coupler, add a matched termination to the setup as shown in figure.


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[4] Obtain the reading of the SWR indicator; calculate the actual coupling of the directional

coupler.

[5] Repeat the step [2], [3] and [4] with the attenuator set at 15 and 10 dB respectively.

A1(dB) A2(dB) Coupling factor

Part C: Measurement Using RF Substitution Method.

[1] Connect the crystal detector to the pin diode modulator(see figure of Part-A)

[2] Set the variable attenuator to 20dB. Adjust the SWR indicator’s range switch and gain

control so that the indicator can indicate 0dB.

[3] Insert the directional coupler and connect the crystal detector to the auxiliary arm of the

directional coupler (see figure of Part-B). Without altering the SWR indicator setting, adjust

the variable attenuator until the SWR indication is same as before, record the attenuator

setting. This is the actual value of the attenuation of the directional coupler in this case.

a) A1= dB A2= dB

b) A1= dB A2= dB

Part D: Measurement of Low Value of Attenuation.

[1] Set up the equipment as shown in figure.


[3] Measure the input SWR of the device under test (a directional coupler in this case).

[4] Determine the attenuation using the following expression.


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A=10x10 log ( )


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Rawalpindi ampus (FURC)

Electrical Engineering Department

EXPERIMENT # 14: STUDY OF A WAVEGUIDE HYBRID-TEE

Objective:

Understand the basic principle of Hybrid-T.

Learn measurement method of Hybrid-T characteristics.

List of Equipment:

Gunn oscillator, PIN modulator, crystal detector, frequency meter, variable attenuator, fixed

attenuator, terminator, directional coupler, hybrid Tee, waveguide to coax adapter, wave guide,

power supply, coaxial cable with connector, square wave generator, thermocouple mount, SWR

meter, power meter, shorting plate.

Procedure:

Part A: Initial Adjustments.


[2] Adjust the SWR indicator gain. For obtaining any convenient deflection.


[4] Apply 1V P-P & 1 KHz modulation voltage to the pin diode modulator.

[5] Adjust the offset voltage and the pulse frequency of the square wave generator to obtain

the maximum deflection on the SWR indicator.


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[6] Set the attenuator to 20dB (A1).

[7] Select a range on the SWR indicator which gives a reasonable deflection on the indicator.

Adjust the gain and frequency control to a reference reading on the dB-scale of the

indicator.

Part B: Measurement of the Decoupling between H-arm and E-arm

[1] Set the equipment as shown in the figure.

[2] Remove the detector and connect the variable attenuator to arm1.

[3] Connect matched terminations and power meter to arm2 and arm3 and connect the

detector to arm4. Keep the power meter at off deflection.

[4] Increase the sensitivity of the SWR indicator in 10dB increment until the same reference as

in [3] is obtained. The attenuation (A2) of the attenuator may be reduced if necessary.

[5] Record the result in the table.

Attenuation of the variable

attenuator

Variation of the SWR meter

gain(in 10dB steps) n steps

Decoupling A1-A2 + (n x10)

A1 (dB) A2 (dB)

Part C: Measurement of Insertion Loss of Hybrid-T (refer to figure of Part-A)

[1] Connect the detector to the attenuator which is set at 20dB.

[2] Select a range on the SWR indicator which gives a reasonable deflection on the indicator.Adjust the gain control to a reference reading on the dB-scale of the indicator.

[3] Remove the detector and connect the arm1 of the Hybrid-T to the attenuator.

[4] Connect the matched terminations and the power meter to arm3 and arm4. Also connect

the detector to arm2.

[5] Decrease the attenuation (A4) until the same reference level as in [2] is obtained. The

insertion loss between arm1 and arm2 is A3-A4.


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[6] For insertion loss between arm1 and arm2, repeat [4] and [5].

[7] For insertion loss between arm4 and arm2, [3], [4] and [5].

Signal path arms Variable attenuator attenuation Insertion loss

(dB)A3(dB) A4(dB)

Part D: Return Loss Measurement of H-arm

[1] Setup equipment as shown in figure 10-6.

[2] Apply 9V to the Gunn oscillator.do not exceed from 9V.

[3] Apply 1Vp-p & 1 KHz to PIN-diode modulator. Adjust the square wave output for maximum

deflection.

[4] Set the variable attenuator to 20dB (A5).

[5] Setup reference point on the SWR indicator.

[6] Remove the shorting plate. Connect arm1 to the directional coupler as shown in figure.


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Connect a matched termination to arm3. Leave arm4 open. (Arm4 is the E-plane T. since the

decoupling to arm4 is almost 30-40dB, leaving it open should not affect the accuracy).

[7] Increase the gain of the SWR indicator in 10dB increment. Decrease the attenuation (A6)

until the same level as in [4] is obtained. Record the result in table.

[8] Repeat [5] and [6] using E-plane T (arm4) instead of H-plane T (arm1).

Object Attenuation Gain increase of the SWR-meter in 10dB

steps

A6-A5 + (n*10)

Return loss

A5(dB) A6(dB) In dB Absolute

value

Arm 1

Arm 2

manual of rf and microwave -new (14 exps)

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