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EASWARI ENGINEERING COLLEGE
EASWARI ENGINEERING COLLEGE
Ramapuram, Chennai-89DEPARTMENT 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 Experiments1. DC characteristics of Laser.
2. DC characteristics of APDOPTICAL 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 measurement5. S - matrix Characterization of E-Plane T, H-Plane T and Magic T6. DC characteristics of LED and PIN Photo Diode
7. Numerical Aperture Determination for Fibers8. Fiber Optic Analog and Digital Link9. 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 Losses8. Attenuation Measurement in Fibers9. DC characteristics of APDSTUDY 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
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 supply2. Gunn oscillator with mount 3. PIN modulator4. Isolator
5. Variable Attenuator6. Frequency meter7. 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 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.NoGunn Bias [Volts]Current [mA]
1.
2.
3.
4.
5.
6.
7.
8.
9.
Sl.NoGunn 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]
RADIATION PATTERN OF HORN/PARABOLIC REFLECTOR ANTENNA
Aim : To plot the radiation pattern of horn and parabolic reflector antenna.Apparatus/Components Required :
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
9. Cooling Fan
10. Stands
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.NoAngle in degreesOutput Voltage [Volts]Angle in degreesOutput Voltage [Volts]
1.0350
2.10340
3.20330
4.30320
5.40310
6.50300
7.60290
8.70280
9.80270
10.90260
11.100250
12.110240
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
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
3. Isolator
4. Variable Attenuator
5. Frequency meter
6. Detector Mount
7. slotted line with tunable probe8. 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 g/2 or g= 2*(distance between successive minima or maxima ). The cutoff wavelength of rectangular wave guide for dominant[TE10] mode is given by c=2*a.
Then the free space wavelength o can be found using the formula:
o= g c/( g2 + c2) and the frequency of the signal is given by :
f = C/ o where C = 3 X 108 m/sec [Velocity of EM waves in free space].
Tabulation :
I. DIRECT METHOD:
Sl.NoMicrometer ReadingFrequency [GHz]
I. INDIRECT METHOD:
a = cms
Sl.No.d1 [cms]d2 [cms]g [cms] c =2*a [cms]o [cms]Frequency [GHz]
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 :
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 g from g = 2*(d1~ d2)
8. Calculate c from c=2*a where a is the broader inner dimesion of the wave guide.
9. Calculate o from o= g c/( g2 + c2)
10. Calculate f from f = C/ o 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 GHzf2 GHZ
Direct method
Indirect Method
BLOCK DIAGRAM
MODEL GRAPH
REPELLER VOLTAGE [VOLTS]
CHARACTERISTICS OF REFLEX KLYSTRON
Aim : To plot the characteristics of reflex klystron oscillator.Apparatus/Components Required :
1. Klystron Power supply
2. Klystron with mount
3. Isolator
4. Variable Attenuator
5. Frequency meter
6. Detector Mount
7. CRO
8. Probes
9. Cooling Fan
10. Stands
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 :
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 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.NoRepeller Voltage [Volts]Output Voltage [Volts]Micrometer reading [Divisions]Frequency [GHz]
1.
2.
3.
4.
5.
6.
7.
8.
9.
BLOCK DIAGRAM : to measure VSWR :
BLOCK DIAGRAM : to measure voltages :
STUDY OF DIRECTIONAL COUPLER
Aim : To study the characteristics of directional coupler and find its S-matrix.
Apparatus/Components Required :
1. Klystron Power supply
2. Klystron with mount
3. Isolator
4. Variable Attenuator
5. Frequency meter
6. Slotted line with tunable probe
7. Matched Termination__ Nos8. 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].
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].
Tabulation :
VSWRInputOutput
At port -1
= _______ VAt 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 :
= [S-1]/[S+1] = S11=S22=S33=S44To 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/V1Transmission 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:
S11S21S31S41
Transmission Loss [dB]Coupling Coefficient [dB]
Directivity [dB]
BLOCK DIAGRAM : VSWR measurement
VSWR MEASUREMENTAIM:
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].
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. 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
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 CharacteristicsV-I Characteristics
P
0
w
e
r
(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 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 voltsIf mAVLED voltsPower [dBm]Power in W [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[W] = 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:
= [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 CharacteristicsV-I Characteristics
P
0
w
e
r
(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.
Apparatus Required :
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 voltsILD mAVLD voltsPower [dBm]Power in W
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[W] = 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 [w]
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.
Apparatus Required :
8. OFT powers supply
9. PD module
10. Optical power meter
11. Optical power source
12. Bare Fiber adapter-Plastic
13. 1m patch cord
14. 1M,10K resistors
15. Digital multimeter
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 [W]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 1M 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[1M] 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).
6. Calculate power in microwatts from the formula :
i. Power[W] = 1mW * 10 [Power in dBm/10]
7. Draw the graph :Power[in Watts] Vs IZ.
Forward bias :1. Connect the 10 K resistor across VL.
2. Adjust the potentiometer and set the bias voltage at 10 V.
3. 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.
4. Connect the optical fiber cable to the PD module and measure the voltage across RL[10 K] 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:
Reverse bias :1. Connect the 10 K resistor across VL.
2. Adjust the potentiometer and set the bias voltage at 10 V.
3. 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.
4. Connect the optical fiber cable to the PD module and measure the voltage across RL[10 K] 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 :
R = VL/(RL*PS) A/W where PS is the power in Watts.
11. From the average value of R, calculate the quantum efficiency using :
C = (Rh/e) x 1/100 %
where h=6.64 x 10-34 Js; e = 1.6 x 10-19 C; = c/ = 3 x 108 /
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[W]VL[V]IF[mA]
P = -_____ dBm
VBIAS[V]VL mV IF [mA]
PIN Photo Diode- reverse bias configuration
Tabulation : PIN Photo Diode- reverse bias configuration: VBIAS = ______ V
P[dBm]PO[W]VL[V]IR[A]
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 [w]
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.
Apparatus Required :
1. OFT powers supply
2. PD module
3. Optical power meter
4. Optical power source
5. Bare Fiber adapter-Plastic
6. 1m patch cord
7. 1M,10K resistors
8. Digital multimeter
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 [W]IL A
CIRCUIT DIAGRAM: APD reverse bias configuration:
.Procedure :
Zero bias :
1. Make the set-up as in the diagram and connect the 1M 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[1M] 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).
6. Calculate power in microwatts from the formula :
i. Power[W] = 1mW * 10 [Power in dBm/10]
7. Draw the graph :Power[in Watts] Vs IZ.
Reverse bias :1. Connect the 1K resistor across VL.
2. Adjust the potentiometer and set the bias voltage at 10 V.
3. 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.
4. Connect the optical fiber cable to the PD module and measure the voltage across RL[1K] 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 :
R = VL/(RL*PS) A/W where PS is the power in Watts.
10. From the average value of R, calculate the quantum efficiency using :
C = (Rh/e) x 1/100 %
where h=6.63 x 10-3 Js; e = 1.6 x 10-19 C; = c/ = 3 x 108 /
Model Graph : APD reverse bias configuration:
Tabulation : APD reverse bias configuration:VBIAS[V]VL mV IR [mA]R[A/W]
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
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 Mandrels6. 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 = __________ VoltsCableOutput voltage
[Volts]
1mV1=
3mV3=
Tabulation : 3. For Bending Loss :
Cable/BendOutput 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 :
[Np/m]= -[1/2]* ln[V3/V1] and [dB/m]= 4.343*
Tabulation : 4. For coupling Loss :
Vin = __________ VoltsCouplingOutput 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:
= 20*log [Vin / Vout] [L1+L2] where = 4.343 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 cable3m cable
Bending loss with 10mm radius bend[dB]
Bending loss with 12mm radius bend[dB]
Determination of Numerical apertureAim : 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 :
InputOutput
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 betweenthe 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 = sin = 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
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 Maxwells 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 CurveCLOCKWISEANTICLOCKWISE
Angle (Degrees)Power ((m)Angle (Degrees)Power ((m)
Gaussian CurveCLOCKWISEANTICLOCKWISE
Angle (Degrees)Power ((m)Angle (Degrees)Power ((m)
Result:
Thus the mode characteristics of the single mode fibers were studied.
FERRITE DEVICESAIM:
To find the characteristics of ferrite device circulator.
COMPONENTS REQUIRED:1. Microwave source (klystron power supply)
2. Klystron Mount 3. Isolator
4. Variable Attenuator5. Frequency meter
6. Circulator
7. Power Detector
8. Matched termination ----- 1 No
FORMULA:
1. The S matrix of 3 port circulator is
001
S =
100
010
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
CHARACTERISTICS OF MAGIC TEE, E-PLANE AND H-PLANE TEEAIM:
To find the characteristics of given Magic Tee,E-plane and H-plane COMPONENTS REQUIRED:1. Micro wave source(klystron power supply)
2. Klystron Mount
3. Isolator
4. Variable Attenuator
5. Frequency meter
6. Magic Tee
7. Power Detector
8. Matched termination ----- 2 Nos
FORMULA:
0 0 1 1
0 0 1 -1
The S matrix of the magic tee is S =1/ 2
1 10 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 ArmH 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
BLOCK DIAGRAM:
ANTENNA GAIN MEASUREMENT
Aim : To find the antenna gain using two-antenna method.Apparatus/Components Required :
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
9. Cooling Fan
10. Stands.
11. Power meterTheory :
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 :
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].
Tabulation:
Transmitted power(Pt)
dBmReceived power(Pr)
dBmAntenna Dimension
(D in mm)Wavelength
(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/). 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(/4R))Result
Thus the gain of the antenna is found as ___________
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]
G U N N BIAS [VOLTS]
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
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
Klystron Power Supply
Klystron with
mount
Isolator
Variable Attenuator
Frequency Meter
Detector Mount
CRO / VSWR meter
Frequency Meter
Variable Attenuator
Isolator
Klystron with
mount
Klystron Power Supply
Matched Termination
Directional Coupler
Slotted line
With tunable
probe
CRO / VSWR meter
Matched Termination
Variable Attenuator
Isolator
Klystron with
mount
Klystron Power Supply
Matched Termination
Wave guide
Detector
Directional Coupler
Frequency Meter
CRO / VSWR meter
3 44
1 2
Isolator
Detector mount
Device under Test
Frequency Meter
Variable Attenuator
Isolator
r
Klystron with
mount
Klystron Power Supply
Matched Termination
CRO / VSWR meter
Slotted line section
Frequency Meter
Variable Attenuator
Isolator
r
Klystron with
mount
Klystron Power Supply
Klystron with
mount
Klystron Power Supply
CRO / Power meter
Detector Mount
Frequency Meter
VARIABLE
ATTENUATOR
FREQUENCY
METER
DETECTOR
(or)
MATCHED TERMINATION
CIRCULATOR
CRO / Power meter
Detector Mount
Variable Attenuator
CRO / VSWR meter
Optical
Power
Meter
OFC
L
D
U
N
I
T
Optical
Power
Meter
Light
Source
(Optical
Txr)
Signal
Source
[Function
Generator]
OFC
Light
Sensor
[Optical
Rxr]
CRO
R2
R1
_
+
APD
V PD
1 M
VL
L
O
A
D
C
U
R
R
E
N
T
m
A
RL[10 K]
VBIAS
VPD
Power [W]
F O C
R U
W R
A R
R E
D N
T
[mA]
V BIAS [V]
F O C
R U
W R
A R
R E
D N
T
[mA]
RL[10 K]
VBIAS
VPD
VL
Power [W]
R E C
V U
E R
R R
S E
E N
T
[A]
V APD
V1
R1
1 M
VL
L
O
A
D
C
U
R
R
E
N
T
A
RL[1 M]
R1
VBIAS
V BIAS [V]
Ir [mA]
He-Ne LASER
FIBER COUPLER
ROTATION STAGE
DETECTOR
POWER METER
Variable Attenuator
Isolator
VLD
Klystron with
mount
Klystron Power Supply
VPD
Vbias
Vbias (1-10V)
180 ohms
R2
VLED
ISOLATOR
MICRO WAVE SOURCE
MATCHED TERMINATION
(or)
DETECTOR
MATCHED TERMINATION
(or)
DETECTOR
DETECTOR
(or)
MATCHED TERMINATION
MAGIC
TEE
FREQUENCY
METER
VARIABLE
ATTENUATOR
ISOLATOR
MICRO WAVE SOURCE
MATCHED TERMINATION
(or)
DETECTOR
CRO / VSWR meter
Detector mount
Frequency Meter
Variable Attenuator
Isolator
r
Klystron with
mount
Klystron Power Supply