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EASWARI ENGINEERING COLLEGE

Ramapuram, Chennai-89

DEPARTMENT OF ELECTRONICS AND

COMMUNICATION ENGINEERING

LAB MANUAL

Subject code: EC2405

Subject: OPTICAL AND MICROWAVE LAB

Year /Semester: IV/VII

Department: ECE

Prepared by: Reviewed By Approved by:

(R.Hema) HOD/ECE

(A.Ponraj)



Microwave Experiments:

1. Reflex Klystron – Mode characteristics

2. Gunn Diode – Characteristics

3. VSWR, Frequency and Wave Length Measurement

4. Directional Coupler – Directivity and Coupling Coefficient

S – Parameter measurement

5. Isolator and Circulator – S - parameter measurement

6. Attenuation and Power measurement

7. S - matrix Characterization of E-Plane T, H-Plane T and

Magic T.

8. Radiation Pattern of Antennas.

9. Antenna Gain Measurement

Optical Experiments:

1. DC characteristics of LED and PIN Photo Diode.

2. Mode Characteristics of Fibers

3. Measurement of Connector and Bending Losses.

4. Fiber Optic Analog and Digital Link

5. Numerical Aperture Determination for Fibers

6. Attenuation Measurement in Fibers

Extra Experiments

1. DC characteristics of Laser.

2. DC characteristics of APD



OPTICAL AND MICROWAVE LAB

LIST OF EXPERIMENTS

I CYCLE

1. Study of Microwave Components.

2. Reflex Klystron – Mode characteristics.

3. DC characteristics of Gunn diode oscillator.

4. Isolator and Circulator – S - parameter measurement

5. S - matrix Characterization of E-Plane T, H-Plane T and

Magic T

6. DC characteristics of LED and PIN Photo Diode

7. Numerical Aperture Determination for Fibers

8. Fiber Optic Analog and Digital Link

9. DC Characteristics of Laser.

II CYCLE

1. Determination of VSWR, guided wavelength, frequency

measurement.

2. Directional Coupler – Directivity and Coupling Coefficient

S – parameter measurement.

3. Attenuation and Power measurement.

4. Radiation Pattern of Antennas.

5. Antenna Gain Measurement

6. Mode DC characteristics of Single mode fibers.

7. Measurement of Connector and Bending Losses

8. Attenuation Measurement in Fibers

9. DC characteristics of APD



STUDY OF MICROWAVE COMPONENTS

AIM:

To study the microwave components.

RECTANGULAR WAVEGUIDE:

Waveguides are manufactured to the highest mechanical and electrical standards

and mechanical tolerance to meet internal specifications, L and S band

waveguides are fabricated by precision brazing of brast plate and all other

waveguides are in extrusion quality. Waveguide sections of specified length can

be supplied with flinges, painted outside and silver or gold plated inside.

VARIABLE ATTENUATOR:

Model 5020 is a simple and conveniently variable type set level attenuators to

provide at least 20db of continuously variable attenuation. These consist of a

movable lossy vane inside the section of a waveguide by means of a micrometer.

The configuration of lossy vane is so designed to obtain the low VSWR

characteristics over the entire frequency band. These are meant for adjusting

power levels and isolating a source and load.

FREQUENCY METER MICROMETER TYPE:

Model 4055 are absorption type cavity wavemeter called frequency meter. These

are made of tunable resonant cavity of particular size. The cavity is connected to

the source of energy through a section of waveguide. The cavity absorbs some

power at resonance, which is indicated as a sip in the output power. The tuning



of the cavity is achieved by means of a plunger connected to a Microcontroller.

The readings of the micrometer at resonance gives frequency from the calibration

chart, provided calibration is normally provided at 200Mhz internals.

TUNABLE PROBE

Model 6055 tunable probes are designed for use with model 6051 slotted

sections. These are meant for exploring the energy of the electric field in a

suitable fabricated section of the waveguide. The depth of penetration into a

waveguide section is adjustable by knob of the probe. The tip picks up the RF

power from the line and this power is rectified by crystal detector, which is then

fed to the VSWR meter or indicating instrument.

WAVEGUIDE DETECTOR MOUNT:

Model 4051 tunable detector mounts are simple and easy to use instruments for

detecting microwave power through a suitable detector. It consists of a detector

crystal mounted in a section of waveguide and a shorting plunging for matching

purpose. The output of the crystal may be fed to and indicating instrument. In K

and R band detector mounts, the plunger is driven by a micrometer.

THREE PORT FERRITE CIRCULATOR:

Model 6021 and 6022 are T and Y type of the three port ferrite circulators

respectively. These are precisely machined and matched three port devices and

these are meant for allowing microwave energy to flow in clockwise direction

with negligible loss but almost no transmission in anticlockwise direction.



Purpose and for measuring reflections and impedance. These consist of a section

of waveguide thus making it a four-part network. However, the fourth port is

terminated with a matched load. These two parallel sections are coupled to each

other through many holes almost to give uniform coupling minimum frequency

sensitivity and high directivity. These are available in 3,6,10,20 and 40 db

couplings.

E-PLANE BEND:

Model 7071 E-plane bends are fabricated from a section of waveguide to provide

one 90° ± 1 bend in E-plane. The cross section of bent waveguide is kept

throughout uniform to give VSWR less than 1.05 or 1.08 or 1.02 over the entire

frequency band. Bends other than 90° can also be fabricated.

KLYSTRON POWER SUPPLY:

Model KP-1010 power supply has been designed to operate low power klystrons

such as 2K25, 756A, RK5976 etc. Beam voltage may be continuously varied and

is indicated on the front panel meter which can be read the beam supply current

and repeller supply volts also by changing the switch. Internal modulation square

waves with continuous variable frequency and amplitude are provided. An

external modulation may be used through the UHF(F) connector provided on

front panel.

GUNN POWER SUPPLY:

Model X-110 Gunn power supply comprises of a regulated DC power supply and

a square wave generator, designed to operate Gunn oscillator model 2151 or

2152 and pin modulate model 451 respectively. The DC voltage is variable from

0 to 10v. The front panel meter monitors the gunn voltage and the current drawn



by the Gunn diode. The square waves of the generator are variable from 0 to 10v

in amplitude and 900 to 1100Hz in frequency. The power supply has been so

designed to protect Gunn diode from reverse voltage application, over transit and

low frequency oscillators by negative resistance of Gunn diode.

RESULT:

Thus the various microwave components were studied.

BLOCK DIAGRAM

MODEL GRAPH

Gunn

Power

Supply

Gunn

Oscillator

With mount

PIN

Modulator

Isolator

Variable

Attenuator

Frequency

Meter

Detector

Mount

CRO /

VSWR

meter



G U N N BIAS [VOLTS]

CHARACTERISTICS OF GUNN DIODE OSCILLATOR

Aim : To plot the characteristics of Gunn diode oscillator.

Apparatus/Components Required :

1. Gunn Power supply 2. Gunn oscillator with mount 3. PIN modulator

4. Isolator 5. Variable Attenuator 6. Frequency meter

7. Detector Mount 8. CRO 9. Probes

10. Cooling Fan 11. Stands

Theory :

Gunn diodes are made up of bulk semiconductor materials like Gallium

Arsenide[GaAs],Indium Phosphide[InP] and Cadmium Telluride[CdTe] which

G U N N BIAS [VOLTS] G U N N BIAS [VOLTS]



exhibit negative resistance. Initially for a range of bias voltages the current

increases with voltage and later starts decreasing with increase in bias voltage. In

this negative resistance region they exhibit Gunn effect or transfer electron effect

and generates microwave oscillatios. Gunn diode operates in 4 different modes

viz. Gunn or TT mode,LSA mode, quenched domain mode and delayed mode.

Microwave oscillations are generated in Gunn or TT mode. A Gunn diode

oscillator is designed by mounting the diode inside a waveguide cavity formed by

a short circuit termination at one end and by an Iris at the other end.

Precautions :

1. Before switching ON the Gunn power supply ensure that the Gunn Bias

voltage knob is in the minimum position[Left extreme] and the PIN Bias

voltage knob is in the middle position.

2. While doing the experiment ensure that the Gunn Bias voltage does not

exceed 9 Volts.

3. Before switching OFF the Gunn Bias power supply ensure that the Gunn Bias

voltage knob is in the minimum position[Left extreme].

1. V-I Characteristics :

Sl.No Gunn Bias

[Volts]

Current

[mA]

1.

2.

3.

4.

5.

6.

7.

8.



9.

Sl.No Gunn Bias

[Volts]

Output

Power [dB]

Micrometer

reading

[Divisions]

Frequency

[GHz]

1.

2.

3.

4.

5.

Procedure :

1. Obtain square wave output by setting the Gunn bias voltage around 6 volts

or above and maximize the output by adjusting the micrometers attached to

the short-circuit plunger of the gunn diode mount and the detector mount.



2. Now starting from 0 Volt vary the Gunn bias in steps of 1 Volt up to a

maximum of 9 Volts. Note down the corresponding currents from the

milliammeter.

3. Tabulate the readings and plot the V-I characteristics.

4. In the region of oscillations i.e. for Gunn bias voltages in the range 6-9

Volts, for different bias voltages tune the frequency meter and observe dip

in the output and the corresponding micrometer position. After noting

down the micrometer reading, release[detune] the frequency meter and

connect the detector output to VSWR/POWER meter and note down the

output power.

5. Tabulate the readings and plot the input-output characteristics[output

power Vs Gunn bias voltage] and the frequency response[Frequency Vs

Gunn bias vltage].

Result :

Thus the characteristics of Gunn diode has been plotted.

BLOCK DIAGRAM



Horn Antenna

[Transmitting]

Horn Antenna

[Receiving]

Horn Antenna

[Transmitting]

Parabolic reflector

[Receiving]

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Detector

Mount

CRO / VSWR

meter

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Detector

Mount

CRO / VSWR

meter



RADIATION PATTERN OF HORN/PARABOLIC

REFLECTOR ANTENNA

Aim : To plot the radiation pattern of horn and parabolic reflector antenna.


1. Klystron Power supply 2. Klystron with mount

3. Isolator 4. Variable Attenuator

5. Horn Antenna[2 nos] 6. Detector Mount

7. CRO 8. Probes


11. Parabolic reflector antenna

Theory :

Radiation pattern of an antenna is obtained by plotting the voltage or

power or gain at various angles from the antenna. Both horn and parabolic

reflector antenna the radiation pattern is uni-directional i.e. maximum energy is

radiated in a particular direction and in other directions minimum or zero

radiation. In addition to the major lobe there may be few minor side lobes

existing. Half-power or 3-dB beam width may be found by measuring the angle

between the two half-power points or the 3-dB points or the angle between two

points where the voltage is Vmax/√2. Similarly the beam width between first

nulls[BWFN] may be found by measuring the angle between two tangential lines

to the major lobe from the origin.



MODEL GRAPH

Tabulation :

1. Horn Antenna & PARABOLIC ANTENNA: Vin= Volts d= cms

Sl.No Angle in

degrees

Output

Voltage

[Volts]

Angle in

degrees

Output

Voltage

[Volts]

1. 0 350

2. 10 340

3. 20 330

4. 30 320

5. 40 310

6. 50 300

7. 60 290

8. 70 280

9. 80 270

10. 90 260

11. 100 250

12. 110 240



Precautions :

1. Before switching ON the Klystron power supply ensure that the beam

voltage knob is in the minimum position[Left extreme] and the repeller

voltage knob is in the maximum position[right extreme].

2. While doing the experiment ensure that the beam voltage and beam current

do not exceed 250 Volts and 20 mA respectively.

3. Before switching OFF the Klystron power supply ensure that the beam

voltage knob is in the minimum position [Left extreme] and the repeller

voltage knob is in the maximum position [right extreme].

Procedure :

1. Obtain square wave output without the antenna in the set-up and maximize

the output by adjusting beam voltage, repeller voltage, modulating

amplitude and the attenuator and note down this voltage as Vin.

2. Now connect the two horn antenna in the set-up and align the two antenna

both vertically and horizontally for maximum output. Ensure a minimum

distance(end to end) of 15 cms between the antenna.

3. Set the angle where maximum output obtained as zero degrees and note

down the output voltage.

4. Vary the angle from zero degrees through 360 degrees and note down the

corresponding output voltages. Tabulate the readings.

5. Plot the Output voltage Vs Angle in degrees in a polar sheet.

6. Find the 3dB beam width and BWFN.

7. Repeat steps 1 to 6 with parabolic reflector antenna in the receiving

antenna position instead of horn antenna.

Result :

Thus the radiation pattern of horn and parabolic reflector antenna were

plotted and the 3-dB beamwidth and BWFN were found to be :

3-dB beamwidth = degrees

BWFN = degrees



BLOCK DIAGRAM : Direct Method

BLOCK DIAGRAM : Indirect Method

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter

Detector

Mount

CRO /

VSWR meter

CRO / VSWR

meter

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter

Slotted Line

with tunable

probe

Matched

Termination



MEASUREMENT OF WAVELENGTH AND FREQUENCY

Aim : To measure wavelength and the frequency of the microwave

signal by both direct and indirect methods.

Apparatus/Components Required : 1. Klystron Power supply 2. Klystron with mount


5. Frequency meter 6. Detector Mount

7. slotted line with tunable probe 8. Matched Termination

9. CRO 10. Cooling Fan

11. Probes 12. Stands

Theory :

I. DIRECT METHOD:

Frequency meter is made up of a cylindrical cavity[absorption type]. By

varying the effective height(d) of the cavity its resonance frequency (fr) may be

varied. At resonance i.e. when the incoming signal frequency matched with the

‘fr’ of the cavity, maximum energy is stored in the cavity resulting in a minimum

transmitted output.

II. INDIRECT METHOD:

While studying the standing wave pattern, the distance between two

successive minima or maxima corresponds to ‘λg/2’ or λg= 2*(distance between



successive minima or maxima ). The cutoff wavelength of rectangular wave

guide for dominant[TE10] mode is given by λc=2*a.

Then the free space wavelength ‘λo’ can be found using the formula:

λo= λg λc/√( λg2 + λc2) and the frequency of the signal is given by :

f = C/ λo where C = 3 X 108 m/sec [Velocity of EM waves in free space].

Tabulation :

I. DIRECT METHOD:

Sl.No Micrometer

Reading

Frequency [GHz]

I. INDIRECT METHOD:

a = cms

Sl.No. d1

[cms]

d2

[cms]

λg

[cms]

λc =2*a

[cms]

λo

[cms]

Frequency

[GHz]



Precautions :




2. While doing the experiment ensure that the beam voltage and beam current


3. Before switching OFF the Klystron power supply ensure that the beam



Procedure :

I.DIRECT METHOD :

1. Obtain square wave output and maximize the output by adjusting beam

voltage, repeller voltage, modulating amplitude and the attenuator.



2. Adjust the micrometer attached to the frequency meter till the output

becomes minimum or a dip is observed in the CRO. Now, note down the

micrometer reading.

3. Refer to the conversion chart and note down the corresponding frequency

in GHz.

II.INDIRECT METHOD :

4. Without disturbing the settings remove the detector mount from the setup

and connect the slotted line with tunable probe and the the matched

termination as in the diagram.

5. Observe the variation in the output in the CRO by moving the probe along

the slotted line from left to right.

6. Note down two successive minima or maxima points as d1 and d2.

7. Find λg from λg = 2*(d1~ d2)

8. Calculate λc from λc=2*a where ‘a’ is the broader inner dimesion of the

wave guide.

9. Calculate λo from λo= λg λc/√( λg2 + λc2)

10. Calculate ‘f’ from f = C/ λo where C = 3 X 108 m/sec [Velocity of EM

waves in free space].

11. Obtain signal with a different frequency[mode] by adjusting the repeller

voltage.

12. Repeat steps 1 to 10 for the new frequency.



Result :

Thus the wavelength and frequency of the signal is

measured by both direct and indirect methods and are :

f1 GHz f2 GHZ

Direct method

Indirect Method

BLOCK DIAGRAM

MODEL GRAPH

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter

Detector

Mount

CRO /

VSWR meter



REPELLER VOLTAGE [VOLTS]

CHARACTERISTICS OF REFLEX KLYSTRON

Aim : To plot the characteristics of reflex klystron oscillator.



5. Frequency meter 6. Detector Mount

7. CRO 8. Probes


Theory :



Reflex Klystron Oscillator works on the principle of Velocity Modulation.

The velocity of the electrons[electron beam] vary in accordance with the

variation of the RF field setup in the cavity. By varying the repeller voltage the

frequency of the signal and also the output power/voltage varies. While varying

repeller voltage continuously the output waveform[square wave] appears and

disappears several times. Each appearance of the output within a given range of

repeller voltage is called a “mode”. The method of varying the output frequency

by varying the repeller voltage is called “ Electronic tuning of reflex klystron”.

Precautions :




2.While doing the experiment ensure that the beam voltage and beam current


3.Before switching OFF the Klystron power supply ensure that the beam



Procedure :

1.Obtain square wave output and maximize the output by adjusting beam

voltage, repeller voltage, modulating amplitude and the attenuator.

2. For each mode note down the maximum output voltage and the

corresponding repeller voltage[X Volts] and the micrometer position for

which the output becomes minimum/disappears. Also note down the above

values for repeller voltages: X+5V and X-5V.

3.Repeat step 2 for atleast 3 different modes.



4.Tabulate the readings.

5.Plot the Output Vs repeller voltage and Frequency Vs repeller voltage.

Result :

Thus the characteristics of reflex klystron has been plotted .

Tabulation :

Sl.No Repeller

Voltage [Volts]

Output

Voltage

Micrometer

reading

Frequency

[GHz]



[Volts] [Divisions]

1.

2.

3.

4.

5.

6.

7.

8.

9.

BLOCK DIAGRAM : to measure VSWR :

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter



BLOCK DIAGRAM : to measure voltages :

Directional

Coupler

Matched

Termination

Matched

Termination

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter

Directional

Coupler

Wave guide

Detector

Matched

Termination

Slotted line

With tunable

probe

CRO /

VSWR meter

CRO /

VSWR meter



STUDY OF DIRECTIONAL COUPLER

Aim : To study the characteristics of directional coupler and find its S-matrix.



5. Frequency meter 6. Slotted line with tunable probe

7. Matched Termination__ Nos 8. Directional Coupler

9. VSWR meter 10. CRO

11. Stands 12. Probes

13. Cooling Fan

Theory :

Directional Coupler is used to couple a fraction of the input power in either

the forward or backward directions. It works on the principle of aperture

coupling. In a forward coupler desirable amount of power is coupled in the

forward direction through single, two or multiple holes[apertures]. In the

backward direction the amount of power coupled is ideally zero, but practically

there may be a meager[negligible] amount of power which is absorbed by the

matched termination connected internally. Hence practically it remains a closed

port. Ideal values for the parameters are as below :

Main line VSWR = 1

Transmission loss = 10 log[P1/P2] = 20 log[V1/V2] = 0 dB

Coupling coefficient = 10 log[P1/P4]=20 log[V1/V4] is a design parameter

Directivity = 10 log[P4/P3] = 20 log[V4/V3] = ∞ dB

Precautions : 1.Before switching on the Klystron power supply ensure that the beam voltage

knob is in the minimum position[Left extreme] and the repeller voltage knob

is in the maximum position[right extreme].



3.Before switching off the Klystron power supply ensure that the beam



3 4

4 1 2



Tabulation :

VSWR Input Output

At port -1

= _______ V

At port -2

= _______ V

At port -3

= _______ V

At port -4

= _______ V



Procedure :

To measure VSWR : 1.Make the microwave set-up as in the diagram-I, with the directional coupler

with matched terminations at appropriate ports as the terminating load. Obtain

square wave output and maximize the output by adjusting beam voltage,

repeller voltage, modulating amplitude and the attenuator.

2.VSWR measurement : First identify the maxima position in the slotted line

with the help of CRO. Now, without disturbing the set-up connect the probe

output to VSWR meter. Select the appropriate range where deflections in the

meter are obtained. Now using the gain control [ Course and Fine] set the

VSWR to 1 [i.e. 0 dB]. Now move the slotted line to a nearest minima

position on either side. The maximum deflection in the meter gives the VSWR

directly.

3.From the value of VSWR[S], find the reflection coefficient using :

Γ = [S-1]/[S+1] = S11=S22=S33=S44

To meaure voltages :

1.Without disturbing the setup, remove the slotted line and connect a

waveguide detector and measure its output without directional coupler as the

input voltage V1.

2.Now again without disturbing the setup, insert the directional coupler

into the setup as shown in the diagram-II. 3.Measure the voltage at port-2[V2] with the detector at port-2 and a matched

termination at port-4.

4.Interchange the detector and matched termination without disturbing the

setup. Measure the voltage at port-4[V4].

5.Without disturbing the setup reverse the directional coupler and measure

voltage at port-3[V3], with detector at port-3 and matched termination at port-

2.

6.Tabulate the readings and calculate the s-parameters from :

S21 = V2/V1 ; S31 = V3/V1 ; S41 = V4/V1

Transmission loss[T] in dB = 20 log [1/S21]

Coupling Coefficient [C] in dB = 20 log [1/S31] and

Directivity [D] in dB = 20 log [S41/S31]

Result :



The characteristics of directional coupler is studied and the S – parameters

and the other parameters are found as below:

S11 S21 S31 S41

Transmission Loss

[dB]

Coupling Coefficient

[dB]

Directivity [dB]

BLOCK DIAGRAM : VSWR measurement

Klystron

Power

Supply

Klystron

with

mount

Isolator

r

Variable

Attenuator

Frequency

Meter

Slotted line

section

CRO /

VSWR meter

Matched

Termination



VSWR MEASUREMENT

AIM:

To measure VSWR introduced by the wave guide in dominant mode

of propagation.

COMPONENTS REQUIRED:

1. Microwave source (klystron power supply)

2. Klystron Mount

3. Isolator

4. Variable Attenuator

5. Slotted section

6. Matched Termination

7. VSWR meter (or) CRO

FORMULA: VSWR = V max / V min

Precautions : 1.Before switching on the Klystron power supply ensure that the beam voltage

knob is in the minimum position[Left extreme] and the repeller voltage knob

is in the maximum position[right extreme].





3.Before switching off the Klystron power supply ensure that the beam



PROCEDURE:

1. Arrange the bench setup as shown in figure.

2. Adjust the probe carriage to measure V max and note the readings.

3. Adjust the probe carriage to measure V min and note the readings.

4. Use the formula to find VSWR.



RESULT:

Thus the VSWR introduced by the wave guide in dominant mode of

propagation was determined and verified.



BLOCK DIAGRAM :ATTENUATION MEASUREMENT

Klystron

Power

Supply

Klystron

with

mount

Isolator

r

Variable

Attenuator

Frequency

Meter

Detector

mount

CRO /

VSWR meter

Klystron

Power

Supply

Klystron

with

mount

Isolator

r

Variable

Attenuator

Frequency

Meter

Device under

Test

Detector

mount

CRO /

VSWR meter



ATTENUATION AND POWER MEASUREMENT

AIM

To measure the output of a variable attenuator and to verify its attenuation

characteristics.

APPARATUS REQUIRED:

Klystron power supply, Klystron with mount, Isolator, Variable attenuator,

Frequency meter, Detector mount, CRO, cooling fan, probes, stands

PRECAUTIONS:

1.Before switching on the klystron power supply ensure that beam voltage knob

and repeller voltage knob are in the min and max position respectively.

2. At no point should voltage or current exceed 250 mA and 20mA respectively.

3. Ensure that knobs are at the original position before switching off.

THEORY:

THERMOCOUPLE:

Thermocouples are based on the fact that dissimilar metals generate a voltage

due to temperature difference at a hot and a cold junction of the two metals.

The increased density of free electrons at the left causes diffusion towards the

right. The migration of electrons towards the right is by diffusion, the same

physical phenomenon that tends to equalize the partial pressure of a gas

throughout the space. The rod reached equilibrium when the rightward force of

heat induced diffusion.



MODERN POWER METER:

A 16- bit analog digital converter (ADC) processes the average power signal.

A highly sophisticated video amplifier design is implemented for the normal

path to pressure envelop fidelity and accuracy. The central gun for peak and

average power meters is to provide reliable accurate and fast characteristics of

pulsed and complex modulation envelops. The meters excel in versatility

featuring a techniques called time gated measurements.

PROCEDURE:

1. Set the micro bench as per the block diagram.

2. Initial setting in the power meter is set.

3. Resolution→ 0.1 db]

4. Select absolute unit option and select dbm.

5. Select bar graph required.

6. Select the band as X

7. Select the number of samples/sec as 100/sec.

8. Enter the switch, which is used to store the selected mean option.

9. Escape switch is used to cancel any command.

10. The maximum output power is obtained by properly adjusting the klystron

power supply.

11. By varying the variable attenuator corresponding output power is

measured from the power meter.

12. A graph is drawn between micrometer reading of VA and power meter.

RESULT:



Thus the output of a variable attenuator was measured and its characteristics

were verified.

CIRCUIT DIAGRAM:

Model Graph :

P-I Characteristics V-I Characteristics

P

0

w

Optical

Power

Meter

OFC

Vbias

(1-10V)

180

ohms R2

VLED



e

r

(μ

W) C U R R E N T [mA] V O L T AG E [Volts]



DC CHARACTERISTICS OF LED

Aim : To plot the VI and PI characteristics of LED operating at 850 nm

wavelength and find the conversion efficiency.

Apparatus Required :

1. OFT powers supply

2. LED module

3. Optical power meter

4. Bare Fiber adapter-Plastic

5. 1.25m plastic fiber

6. 180 Ω resistor

7. Digital multimeter

Theory :

LEDs, used in optical communication have high modulation rate

capability, high radiance, high reliability and emission wavelengths restricted to

the near-IR spectral regions of low attenuation in fibers. The materials used are

GaAs, InGaAs. The internal quantum efficiency is only 1% and external

efficiency is much lower due to light emitted from semiconductor-air surface,

angle of incidence, the light reflected back and absorption at the point of

generation and emitting surface. Recombination of excess electrons and holes

takes place whenever current is passed through the PN junction of LED. The

energy released by photons results in light emission.

Precautions :

1. Before switching on the power supply ensure that the

potentiometer[R2] is in the minimum position[Left extreme].

2. After completing the experiment before switching of the power

supply to the LD module ensure that the potentiometer[R2] is in the

minimum position[Left extreme].



Tabulation :

Vf volts If mA VLED volts Power

[dBm]

Power in

μW [Po]



Procedure :

1. Make the set-up as in the diagram.

2. With potentiometer in the minimum position switch on the power

supply.

3. Measure the voltage across resistor R1 and note down as V1;

4. Measure the voltage across the LED and note it as VLED; Also note

down the corresponding output power in dBm from the optical power

meter.

5. Calculate If from the formula: If = V1/180.

6. Calculate power in microwatts from the formula :

Power[μW] = 1mW * 10 [Power in dBm/10]

7. Vary the potentiometer slowly and for various values of V1 repeat

steps 3 to 6.

8. Tabulate the readings.

9. Plot the VI characteristics taking VLED in the x-axis and If in the y-

axis.

10. Plot the P-I characteristics taking If in the x-axis and the Power in

watts in the y-axis.

11. By taking the average values of power in watts, VLED and If and using

the following formula calculate the conversion efficiency:

η = [Po*100/ (VLED* If)] %



Result :

Thus the VI and PI characteristics of LED was plotted and the conversion

efficiency is found as ___________________.

CIRCUIT DIAGRAM:

Model Graph :

P-I Characteristics V-I Characteristics

P

0

L

D

U

N

I

T

Opt

ical

Po

wer

Met

er

R1 R2

VLD

VPD

Vbias



w

e

r

(μ

W) C U R R E N T [mA] V O L T AG E [Volts]

CHARACTERISTICS OF LASER DIODE

Aim : To Study the VI characteristics of LASER diode.


1.OFT powers supply

2.LD unit and driver module

3.Optical power meter

4.Digital multimeter

5.Mounting Posts

Theory :

LASER diode is a semiconductor diode which is capable of producing a

lasing action by applying a potential difference across a modified PN junction.

This modified PN junction is heavily doped and contained within a cavity thus

providing the gain medium for LASER. The built-in photo diode senses the



light sent from the LD and the output of this PD can be used as feedback for

controlling the current through the LD. Light from LD is directional.

Precautions :

1.Before switching on the power supply ensure that the potentiometer[R2]

is in the minimum position[Left extreme].

2.After completing the experiment before switching of the power supply

to the LD module ensure that the potentiometer[R2] is in the minimum

position[Left extreme].

Tabulation :

V1 volts ILD mA VLD volts Power

[dBm]

Power in

μW



Procedure :

1.Make the set-up as in the diagram.

2.With potentiometer in the minimum position switch on the power

supply.

3.Focus the LASER beam onto the aperture of the connector connected to

the optical power meter and align the beam to the aperture to get

maximum output in the power meter.

4.Measure the voltage across resistor R1 and note down as V1;

5.Measure the voltage across the LD and note it as VLD; Also note down

the corresponding output power in dBm from the optical power meter.

6.Calculate ILD from the formula: ILD = V1/24.

7.Calculate power in microwatts from the formula :

Power[μW] = 1mW * 10 [Power in dBm/10]

8.Vary the potentiometer slowly and for various values of V1 repeat steps

4 to 7.

9.Tabulate the readings.

10.Plot the VI characteristics taking VLD in the x-axis and ILD in the y-

axis.

11.Plot the P-I characteristics taking ILD in the x-axis and the Power in

watts in the y-axis.

12. Note down the value of threshold current where the optical output

appears.

Result :

Thus the VI and PI characteristics of LASER diode was plotted and the

threshold current is found as _________________.



CIRCUIT DIAGRAM: PIN Photodiode- zero bias configuration:

Model Graph : PIN Photodiode- zero bias configuration:

P O W E R [μw]

V PD

1 MΩ

VL

L

O

A

D

C

U

R

R

E

N

T

m

A



DC CHARACTERISTICS OF PIN Photo diode

Aim : To study the zero bias, forward bias and reverse bias characteristics of

PIN photo diode and plot the VI and PI characteristics and to determine the

responsivity and quantum efficiency.



9. PD module


11. Optical power source


13. 1m patch cord

14. 1MΩ,10KΩ resistors


Theory :

If a photon having adequate energy[should be greater than the band gap]

is absorbed by a p-n junction, an electron will be transferred to the conduction

band, thereby forming a hole in the valence band. As a result, an open circuit

voltage is created and a current will flow, provided the circuit is closed through

a load resistor. In case of reverse bias p-n junction, the transit time can be made

small and it will produce current linearly proportional to the incident photon

energy. The frequency response can be improved if the p-n junction is separated

by an intrinsic region. The introduction of the intrinsic region decreases the

junction capacitance. This is called ‘Positive Intrinsic Negative’[PIN] photo

diode. For high frequency operation, the PIN diode can be made as small as

practical, to match the size of the spot of the optical beam.



Tabulation : PIN Photo Diode- zero bias configuration:

Power

[dBm]

VL volts PO [μW] Iz mA

CIRCUIT DIAGRAM: PIN Photo Diode- forward bias

configuration:



Procedure :

Zero bias :

1. Make the set-up as in the diagram and connect the 1MΩ resistor across VL.

2. Set the power source in CW mode and adjust to get maximum output.

Connect the 1m ST-ST patch cord between source and power meter and

adjust the power to -18 dBm.

3. Connect the optical fiber cable to the PD module and measure the voltage

across RL[1MΩ] and note as VL.

4. Vary the optical power input in steps of 2 to 3 dBms.

5. Tabulate the readings and calculate IZ = VL / (1 x 106).


i. Power[μW] = 1mW * 10 [Power in dBm/10]

7. Draw the graph :Power[in Watts] Vs IZ.

Forward bias :

1. Connect the 10 KΩ resistor across VL.

2. Adjust the potentiometer and set the bias voltage at 10 V.

RL[10 KΩ]

VBIAS VPD







across RL[10 KΩ] and note as VL.

5. Vary the optical power in steps of 2 to 3 dBm and note down the

corresponding VL.

6. Calculate IF = VL / (1 x 104).

7. Plot the graph : Power in Watts Vs IF.

8. Now, fix the optical power at some constant value say -10 dBm and vary

the VBIAS from 1V to 10 V in steps of 1 V and note down the

corresponding VL.

9. Plot VBIAS Vs IF.

Model Graph : PIN Photo Diode- forward bias configuration:



V BIAS [V]

F

O C

R U

W R

A R

R E

D N

T

[mA]

Power [μW]

F

O C

R U

W R

A R

R E

D N

T

[mA]



Reverse bias :

1. Connect the 10 KΩ resistor across VL.



Connect the 1m ST-ST patch cord between source and power meter

and adjust the power to -18 dBm.

4. Connect the optical fiber cable to the PD module and measure the

voltage across RL[10 KΩ] and note as VL.

5. Vary the optical power in steps of 2 to 3 dBm and note down the

corresponding VL.

6. Calculate IR = VL / (1 x 104).

7. Plot the graph : Power in Watts Vs IR.

8. Now, fix the optical power at some constant value say -10 dBm and

vary the VBIAS from 1V to 10 V in steps of 1 V and note down the

corresponding VL.

9. Plot VBIAS Vs IF.

10. Calculate the responsivity from :

Rλ = VL/(RL*PS) A/W where PS is the power in Watts.

11. From the average value of Rλ, calculate the quantum efficiency using

:

ηC = (Rλhν/e) x 1/100 %

where h=6.64 x 10-34 Js; e = 1.6 x 10-19 C; ν = c/λ = 3 x 108 /λ

Result :



Thus zero bias, forward bias and reverse bias characteristics of PIN Photo

diode were plotted and the responsivity and quantum efficiency were found to

be ___________________ and _____________________.

Tabulation : PIN Photo Diode- forward bias configuration:

VBIAS = ____V

P[dBm] PO[μW] VL[V] IF[mA]

P = -_____ dBm VBIAS[V] VL mV IF [mA]



PIN Photo Diode- reverse bias configuration

Power [μW]

R

E C

V U

E R

R R

S E

E N

T

[μA]

RL[10 KΩ]

VBIAS VPD

VL



Tabulation : PIN Photo Diode- reverse bias configuration:

VBIAS = ______ V

P[dBm] PO[μW] VL[V] IR[μA]

P[dBm] = ________ dBm VBIAS[V] VL mV IR [mA]



CIRCUIT DIAGRAM: APD zero bias configuration:

Model Graph : APD zero bias configuration:

P O W E R [μw]

V APD

V1

R1 1 MΩ

VL

L

O

A

D

C

U

R

R

E

N

T

μ

A



DC CHARACTERISTICS OF APD

Aim : To study the zero bias and reverse bias characteristics of APD and plot

the VI and PI characteristics and to determine the responsivity and quantum

efficiency.



2. PD module


4. Optical power source


6. 1m patch cord

7. 1MΩ,10KΩ resistors


Theory :

If a photon having adequate energy[should be greater than the band gap]

is absorbed by a p-n junction, an electron will be transferred to the conduction

band, thereby forming a hole in the valence band. As a result, an open circuit

voltage is created and a current will flow, provided the circuit is closed through

a load resistor. In case of reverse bias p-n junction, the transit time can be made

small and it will produce current linearly proportional to the incident photon

energy. The frequency response can be improved if the p-n junction is separated

by an intrinsic region. The introduction of the intrinsic region decreases the

junction capacitance. This is called ‘Positive Intrinsic Negative’[PIN] photo

diode. For high frequency operation, the PIN diode can be made as small as

practical, to match the size of the spot of the optical beam. A reverse bias

junction can produce secondary emission under high field conditions. It can

result in a noiseless gain and a large reverse current will flow across the

junction. This is known as ‘Avalanche action’ and the diode is referred to as



‘Avalanche Photo diode’[APD].It has internal gain and its responsivity is better

than that of PN or PIN photodiode. Its internal gain yields much better S/N

Tabulation : APD zero bias configuration:

Power

[dBm]

VL volts PO [μW] IL μA

CIRCUIT DIAGRAM: APD reverse bias configuration:



.Procedure :

Zero bias :

1. Make the set-up as in the diagram and connect the 1MΩ resistor across VL.





across RL[1MΩ] and note as VL.

4. Vary the optical power input in steps of 2 to 3 dBms.

5. Tabulate the readings and calculate IZ = VL / (1 x 106).


i. Power[μW] = 1mW * 10 [Power in dBm/10]

7. Draw the graph :Power[in Watts] Vs IZ.

Reverse bias :

1. Connect the 1KΩ resistor across VL.


RL[1 MΩ] R1

VBIAS

APD

+

_




Connect the 1m ST-ST patch cord between source and power meter

and adjust the power to -18 dBm.

4. Connect the optical fiber cable to the PD module and measure the

voltage across RL[1KΩ] and note as VL.

5. Vary the bias voltage from 10 V in steps of 20 V up to 140 V and note

down the corresponding VL.

6. Calculate IR = VL / (1 x 103).

7. Plot the graph : VBIAS Vs IR.

8. Repeat steps 4 to 7 for different input powers say -25 dBm, -40 dBm,

etc.

9. Calculate the responsivity from :

Rλ = VL/(RL*PS) A/W where PS is the power in Watts.

10. From the average value of Rλ, calculate the quantum efficiency using

:

ηC = (Rλhν/e) x 1/100 %

where h=6.63 x 10-3 Js; e = 1.6 x 10-19 C; ν = c/λ = 3 x 108 /λ

Model Graph : APD reverse bias configuration:

Tabulation : APD reverse bias configuration:

VBIAS[V] VL mV IR [mA] Rλ[A/W]

V BIAS [V]

Ir [mA]



Result :

Thus zero bias and reverse bias characteristics of APD were plotted and

the quantum efficiency is found to be ___________________.

BLOCK DIAGRAM



ANALOG TRANSMISSION THROUGH OPTICAL FIBER -

Determination of Bandwidth and various losses

Light

Source

(Optical

Txr)

Signal

Source

[Function

Generator]

OFC

Light

Sensor

[Optical

Rxr]

CRO



Aim : To establish a fiber optic analog link and determine the bandwidth,

attenuation loss, bending loss and coupling losses.

Apparatus/Components Required : 1. OFT Kit 2. CRO

3. Function Generator 4. 1m and 3m OF cables

5. 10 mm and 12 mm Mandrels 6. Jig for connecting 2 fibers

Theory :

Though optical fibers offer many advantages including very low EM

interference, the signal strength decreases as light travels longer distances. This

is because of the various losses including rayleigh scattering loss and increases

with length.

Unless proper splicing techniques are used for connecting 2 fibers there

exists considerable coupling losses due to various misalignments including

axial misalignment.

Similarly there exist two kinds of bending losses viz. micro bending loss

and constant radius bending losses. The former is because of the light absorbed

by the water/air molecules or any irregularities which could have occurred at

the time of manufacturing of the fibers. Constant radius bending losses occur

because of fiber bending during cable laying.



Tabulation : 1. For Bandwidth : Vin = __________ Volts

Frequency

[Hz]

Output

Voltage

[Volts]

Gain

[dB]

Tabulation : 2. For Atenuation Loss : Vin = __________ Volts

Cable Output voltage

[Volts]

1m V1=

3m V3=

Tabulation : 3. For Bending Loss :

Cable/Bend Output voltage

Voutbb[Volts]

Output voltage

Voutab[Volts]

1m / 10 mm

1m / 12 mm

3m / 10 mm

3m / 12 mm Voutbb = output voltage without any bending

Voutab = output voltage with bend



Procedure :

1.Make the connections as in the diagram. Connect the input signal from FG

to I/O-1. Short I/O-1,I/O-2 and P11 ________. Connect I/O-2 and the output

from P31 to the two channels of CRO. Set the switch SW8 to analog

position. Adjust the gain control knob to obtain proper shape of the output

signal.

2.[a] To measure the bandwidth of the fiber :

Note down the amplitude of input signal as Vin. Vary the frequency

of the input signal from a few Hz to MHz and note down the

corresponding output voltages. Tabulate the readings and calculate the

gain from the formula :

Gain[dB]= 20 * log[Vout/Vin].

Plot the gain Vs frequency graph. Note down the two points which

are 3 dB lower from the maximum gain on either side. Note down the

corresponding frequencies as f1 and f2; then the bandwidth of the fiber is

: [f2-f1]

[b] To measure the attenuation loss in the fiber :

Connect the 1m fiber between the Tx and Rx. Note down the input

voltage as Vin and the output voltage as V1.Replace the 1m fiber with 3m

fiber and for the same Vin note down the output as V3. Then the

attenuation loss in Np/m can be calculated from :

α[Np/m]= -[1/2]* ln[V3/V1] and α’[dB/m]= 4.343*α



Tabulation : 4. For coupling Loss :

Vin = __________ Volts

Coupling Output voltage

[Volts]

Without Gap

With 1 cm Gap

[c] To measure the Bending loss in the fiber :

1.Connect the 1m fiber between the Tx and Rx. Note down the

output voltage as Voutbb.Take the 10mm radius mandrel and make 1 or 2

turns of the fiber on the mandrel and note down the output as Voutab. Now

replace the 10mm mandrel with 12mm mandrel and note down the

output voltage.

2.Repeat step 1 for 3m cable.

3. Calculate the bending loss from the formula:

Bending Loss[dB]= 20*log[Voutbb/Voutab]

[d] To measure the Coupling loss in the fiber :

Connect one end of the 1m fiber to the Tx and one end of the 3m

fiber to the Rx. Connect the remaining 2 end together using the Jig



making the ends to touch each other. Note down the input and output

voltages.

With the same input voltage, introduce 1cm gap between the fiber

ends connected in the jig and note down the output voltage. Calculate the

coupling losses without gap and with 1cm gap using the formula:

η= 20*log [Vin / Vout] – α’[L1+L2] where α’= 4.343α and L1=

1m and L2= 3m

Result : The fiber optic link for analog transmission has been set up and the

following were determined:

Bandwidth of the analog link :

Attenuation loss in Np/m:

Attenuation loss in dB/m:

Coupling loss without Gap in dB:

Coupling loss with 1cm Gap in dB:

================================ 1m cable 3m cable

Bending loss with 10mm radius bend[dB]

Bending loss with 12mm radius bend[dB]



DETERMINATION OF NUMERICAL APERTURE

Aim : To establish a fiber optic data link and determine the numerical aperture

of the fiber and to demonstrate TDM.

Apparatus/Components Required : 1. OFT Kit 2. CRO

3. Function Generator 4. Patch cords

5. Optical fiber cable[1m,3m] 6. Jig for numerical aperture

measurement

Theory :

Large bandwidth, low attenuation are the important characteristics of

optical fibers which makes them suitable for long distance communication,

more particularly data communication. fiber systems for rates below 10 Kbps

are cheap and can be readily constructed from basic components. Data



rates from 100 Kbps to 10 Mbps are costly and difficult to implement.

However, with advancement in technology data rates more than 10 Mbps are

also possible.

Procedure :

To measure data rate:

Make the connections as in the diagram. Connect the data input signal

from FG to _____. Short I/O-1,I/O-2 and P11 ________. Connect I/O-2 and

the output from P31 to the two channels of CRO. Set the switch SW8 to

analog position. Adjust the gain control knob to obtain proper shape of the

output signal. Trace both input and output signals.

Tabulation : 1. For data transmission :

Input Output

Amplitude[V] Frequency[Hz] Amplitude[V] Frequency[Hz]



To measure the Numerical Aperture of the fiber :

1. Insert one end of the fiber into the numerical aperture measurement

2. Gently tighten the screw to hold the fiber firmly in place.

3. Connect the other end of the fiber to LED2. The fiber will project a circular

patch of the light on the screen. Let ‘d’ be the distance between the fiber tip and

the screen. Now measure the diameter of circular patch of red light in

perpendicular directions.

4.The mean radius of the circular patch is calculated from :



X = [DE + BC] /4

5.Calculate NA from : NA = sinθ = X /√[d2+X2]

6.Repeat the above steps fro different values of ‘d’.

7.Tabulate the readings and find the average value of NA.

Tabulation : 2. For Maximum Bit Rate :

Maximum

Bit Rate

Tabulation : 3. For Numerical Aperture :

X[cms] d[cms] NA

Average NA

Result : The fiber optic link for data transmission has been set up, TDM

demonstrated and the following were determined:

Numerical Aperture[Average] :

Data Rate :



BLOCK DIAG Fiber

O/P

Power

Gaussian

2 curve

(Degrees)

Figure: Field Distribution

He-Ne LASER

FIBER COUPLER

ROTATION

STAGE

DETECTOR

POWER METER



MODE CHARACTERISTICS OF SINGLE MODE FIBERS

Aim: To Study the Mode Characteristics of Single Mode Fibers.

Components Required:

1.Single mode fiber

2.He-Ne laser

3.power meter

4.fiber coupler

5.fiber cleaver

6.20x objective lens

7.rotation stage

8.micro series holder

9.micro series poster

10.fiber positioner

11.methylene chloride

Theory: The propagation characteristics of a single mode fiber can be obtained by

solving Maxwell’s equation for the cylindrical fiber waveguide.This leads to the

knowledge of the allowed modes which may propagate in the fiber .When the

number of the allowed modes is very large ,the mathematics becomes very

complex ;this is when the ray picture is used to describe the waveguide

properties.

The V-number of the fiber is given by:

V=kf.a.NA

Where kf is the free – space wavenumber ,2/o (o is the wavelength of the

light in free space ),

a is the radius of the core,and NA is the numerical aperture of the fiber .

The V –number can be used to characterize which guided modes are allowed to

propagate in a particular waveguide structure.When V < 2.405, only a single

mode ,the HE11 mode,may propagate in the waveguide.This is the single mode

regime.The wavelength at which Vis equal to 2.405 is called the “cut-off



wavelength”,(denoted by c) because that is the wavelength at which the next

higher order mode is cut off and no longer propagates.

TABULATION

Exponential Curve

CLOCKWISE ANTICLOCKWISE

Angle (Degrees) Power (m) Angle (Degrees) Power (m)

Gaussian Curve

CLOCKWISE ANTICLOCKWISE

Angle (Degrees) Power (m) Angle (Degrees) Power (m)

Result:



Thus the mode characteristics of the single mode fibers were studied.

FERRITE DEVICES

AIM:

To find the characteristics of ferrite device – circulator.


1. Microwave source (klystron power supply)

2. Klystron Mount

3. Isolator


5. Frequency meter

6. Circulator

7. Power Detector

8. Matched termination ----- 1 No

FORMULA:

1. The S – matrix of 3 – port circulator is

0 0 1

S = 1 0 0

0 1 0



Where

S11 = s22 = s33 = 0

S12 = s23 = s31 = 0

S21 = 20log (V2 / V1)

S13 = 20log (V1 / V3)

1. Insertion loss = 10 log (p1/p2)

2. Isolation = 10 log (p1/p3)

PROCEDURE:

1. Arrange the bench setup with out connecting circulator

and measure the input power.

2. Now connect the circulator and note down the output

power at port 2 & port 3.

3. Substitute the values to estimate the S – matrix of

circulator.

RESULT:



Thus the characteristics of given 3 – port circulator was obtained and

verified.



BENCH SETUP DIAGRAM OF FERRITE DEVICES:

1 2

3

MICRO

WAVE

SOURCE

ISOLATOR

VARIABLE

ATTENUATOR

FREQUENCY

METER

DETECTOR

(or)

MATCHED

TERMINATION

CIRCULATOR

MATCHED

TERMINATION

(or)

DETECTOR



CHARACTERISTICS OF MAGIC TEE, E-PLANE AND H-PLANE TEE

AIM:

To find the characteristics of given Magic – Tee,E-plane and H-plane


1. Micro wave source(klystron power supply)

2. Klystron Mount

3. Isolator


5. Frequency meter

6. Magic – Tee

7. Power Detector

8. Matched termination ----- 2 No’s

FORMULA:

0 0 1 1

0 0 1 -1

The S – matrix of the magic – tee is S =1/√ 2 1 1 0 0

1 -1 0 0

Where S13 = √ V1/V3

S14 = √ V1/V4

S23 = √ V2/V3



S24 = √ V2/V4

1/2 1/2 1/ √2

1/2 1/2 -1/ √2

The S – matrix of the E-plane – tee is 1/√2 -1/√2 0

1/2 -1/2 1/ √2

-1/2 1/2 1/ √2

The S – matrix of the H-plane – tee is 1/√2 -1/√2 0

THEORY:

A T - junction is an intersection of three waveguides in the form of English alphabet

‘T’. There are several types of Tee Junctions.

TEE – JUNCTION:

In microwave circuits a wave guide line with three independent ports are commonly

referred to as Tee Junction.

Waveguide tees are three – port components. They are used to connect branch (or)

Section of the waveguide in series or parallel with the main waveguide transmission

Line for providing means of splitting and also of combining power in a waveguide System.



H-PLANE TEE

E-PLANE TEE



MAGIC TEE (HYBRID OR E – H PLANE TEES)



The

basic types are

1. E – Plane Tee (series)

2. H - Plane Tee (shunt)

3. Magic Tees (Hybrid or E-H plane Tees).

E – PLANE TEE:

An E – plane tee is a waveguide tee in which the axis of its side arm is parallel to the E

– field of the main guide. A rectangular slot is cut along the broader dimension of a Long

waveguide and side arm is attached. Ports 1 and 2 are the collinear arms and port 3 is the E-

arm.

When the waves are fed into the side arm (port 3), the waves appearing at port 1 and

Port 2 of the collinear arm will be in opposite phase and in the same magnitude. If two input

waves are fed into port 1 and port 2 of the collinear arm, the output Wave at 3 will be opposite

in phase and subtractive. Hence it is called difference Arm

H – PLANE TEE:

An H –Plane Tee junction is formed by cutting a rectangular slot along width of a main

waveguide and attaching another waveguide, the side arm is called the H-arm. Ports 1 and 2

are the collinear arms and port 3 is the H- arm.

If two input waves are fed into port 1 and port 2 of the collinear arm, the output wave at

port 3 will be in phase and additive. Because of this, the third port is called the sum Arm. All

three arms of H – Plane tee lie in the plane of magnetic field, the magnetic field itself into the

arms. This is also called as current junction.

MAGIC TEES (HYBRID OR E – H PLANE TEES):

Here rectangular slots are cut both along the width and breadth of a long waveguide and

side arms are attached. Ports 1 and 2 are collinear arms, port 3 is the H- arm, and port 4 is the

E- arm. So Magic tee is the combinations of E and H Plane Tee.

A wave incident at port 3 (E –arm) divides equally between ports 1 and 2 but opposite

in phase with no coupling to port (H-ram).

A wave fed into collinear port 1 or 2 will not appear in the other collinear port 2 or 1.

Hence two collinear ports 1 and 2 are isolated from each other.



PROCEDURE:

1. Arrange the bench setup with out connecting magic – tee/E-plane/

H-Plane and measure the input power.

2. Now connect the Tee junctions and note down the output power

at port 2, port 3 & port 4.

3. Substitute the value of the port currents to obtain the scattering

parameters of given magic – tee.

3. For various values of input power find the scattering matrix.

RESULT:

Thus the characteristics of given Magic – Tee was found and verified.



BENCH SETUP DIAGRAM OF MAGIC – TEE CHARACTERISTICS:

3

1 2

4

MICRO

WAVE

SOURCE

ISOLATOR

VARIABLE

ATTENUATOR

MATCHED

TERMINATION

(or)

DETECTOR

DETECTOR

(or)

MATCHED

TERMINATION

MATCHED

TERMINATION

(or)

DETECTOR

FREQUENCY

METER

MAGIC

TEE



BLOCK DIAGRAM:

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Frequency

Meter

Detector

Mount

CRO / Power

meter

Klystron

Power

Supply

Klystron

with

mount

Isolator

Variable

Attenuator

Detector

Mount

CRO / Power

meter



ANTENNA GAIN MEASUREMENT

Aim : To find the antenna gain using two-antenna method.


1. Klystron Power supply 2. Klystron with mount


5. Horn Antenna[2 nos] 6. Detector Mount

7. CRO 8. Probes

9. Cooling Fan 10. Stands. 11. Power meter

Theory :

Gain as a parameter measures the directionality of a given antenna. An

antenna with a low gain emits radiation in all directions equally, whereas a

high-gain antenna will preferentially radiate in particular directions.

Specifically, the Gain or Power gain of an antenna is defined as the ratio of

the intensity (power per unit surface) radiated by the antenna in a given

direction at an arbitrary distance divided by the intensity radiated at the same

distance by an hypothetical isotropic antenna:

Precautions :






3.Before switching OFF the Klystron power supply ensure that the beam



http://en.wikipedia.org/wiki/Intensity_%28physics%29

http://en.wikipedia.org/wiki/Isotropic_antenna



Tabulation:

Transmitted

power(Pt)

dBm

Received

power(Pr)

dBm

Antenna

Dimension

(D in mm)

Wavelength

λ

(m)

Distance

between

antennas

(R in m)

Gain

(G in

dBm)



Procedure :

1. Obtain square wave output without the antenna in the set-up and maximize

the output by adjusting beam voltage, repeller voltage, modulating

amplitude and note down the power(Pt)

2. Now connect the two horn antenna in the set-up and align the two antenna

both vertically and horizontally for maximum output. Ensure a minimum

distance(end to end) of (2D2/λ). Where D is the maximum dimension of

antenna.

3. Note the distance between two antennas(R).

4. Note the power received(Pr) in the power meter.

5. Calculate the gain using following formula

G=1/2(Pr-Pt-20log10(λ/4ΠR))

Result

Thus the gain of the antenna is found as ___________

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