Microwave College Essay Example

10% mains variation, Modulation - Continuous wave, Square wave output, Audio modulation, PC data modulation, Nit. Modulating Frequency - 800 to 1200Hz, Nit. Modulating Voltage - O - 10 App bankable BANC for Gun Bias, Output Connector - PC-elementary, Dimension - 178 x 216 x 115mm.

The power switch is used to supply power to the instrument. The mode selection switch allows the user to select the type of modulation or input signal for the PIN supply output. In OCW mode, no signal is provided from the PIN supply output, meaning no modulation occurs. In Internal mode, the output of the PIN supply is a square wave. In PC data Mode, the output of the PIN supply is data from a connected PC. In Audio Mode, the output of the PIN supply is an audio wave. A microphone can be connected to provide an audio signal as a PIN supply to the PIN modulator. The selected output for modulation is available at the PIN Supply.

Gun supply: O - 10 Begun supply output is available here. PIN Bias: Amplitude control for the PIN supply (square wave) from O to IPPP. Gun Bias Mod. Frequency: Frequency control for the PIN supply (square wave). LCD Display:16 X 2 LCD display for Gun supply voltage and current measurements. Rear Panel Control 1. PC Interface: RESTS connector for PC interface. Operating Instructions: The following instructions should be followed for operating the Gun source. Gun Power Supply: 1 . 2. 3. 4. Before switching On the Power Supply, keep Gun Bias and Pin Bias knobs flirtatiousness's.

To connect the Gun oscillator to the Gun Bias Terminal of Gun Power

Supply within to BANC cable, switch on the power and gradually rotate the Gun bias knob to reach the operating voltage. For amplitude modulation of OCW output of Gun Oscillator, connect Pin Bias supply to Pin Modulator using a cable and keep the Mode select switch at internal modulation I.E. Square wave position. Rotate the pin bias knob in a clockwise direction to increase the depth of modulation. The maximum depth of modulation is achieved when the pin bias knob is fully clockwise. When using a detector with SIR meter, turn the Mod.

Rotate the Frequency Knob until the maximum reading is obtained on the SIR Meter. Prior to switching off the Power Supply, adjust the Gun Bias and Pin Bias knobs accordingly and disconnect the Gun Oscillator and Pin Modulator. There are three Gun Oscillators: 1, 2, and 3. Increase the Gun Supply Voltage to the operating voltage. The Gun Oscillator Cavity can be adjusted using a movable short that is connected to a micrometer. If the Gun oscillator fails to produce output, check the condition of the Gun-diode rent. If the meter fails to indicate current, it is possible that the Gun Diode may have burnt or failed. It is not advisable to test the Gun Diode using a multi-meter.

The Gun Oscillator should never be subjected to a negative or excessive positive IV, as this can permanently damage the Gun Diode. To achieve amplitude modulation, the Pin Modulator must be connected to the output of the X-band Gun sources. The power flow through the modulator should be in the direction indicated by the arrow on it, and the mode select switch should

be pressed to enable modulation. If a frequency of KHz and a duty cycle of 50% are required for measurements, bias the Pin modulator using the Power Supply as instructed.

A fixed attenuating vane is installed in the waveguide section of the Pin modulator for Oscillations Diode and Pin Diode. This allows for a DC biasing to the Pin Modulator which reduces the output by 10 dB. If an OCW output is needed, the Pin Modulator should be disconnected from the test setup. Safety precautions should be taken, including switching on the Gun Power Supply and checking the Gun bias before connecting it to the Gun Oscillator and Pin modulator. If the voltage exceeds a certain level, do not connect the Power Supply to the Gun Oscillator.

If the voltage variation is appropriate, fully rotate the Gun Bias Knob anti-clockwise and follow the operating instructions. If the meter reads more than IV during operation of the Gun Oscillator and the Gun Bias Control loses control of the supply, immediately disconnect the Gun Oscillator from the Power Supply. If rotating the Gun Bias Control Knob clockwise causes the Gun Supply Voltage to saturate at approximately 3 to 5 Volts, again disconnect the Power Supply immediately. In such a situation, the Power Supply needs to be reversed. The Klystron Power Supply (MIX) is an advanced solid-state regulated power supply designed for low-power Klystrons like KICK. It incorporates various exclusive features including regulated Beam Supply and Repelled Supply voltages, LED Digital metering for Beam voltage, current, and Repelled voltage, compact and reliable design, and modular construction for easy maintenance. Additionally, it includes provisions for both AM and FM modulation

of Beam current, as well as external modulation of the Klystron supply using desired signal waveforms.

The Klystron Power Supply is constructed with quality components and a sturdy design to ensure years of reliable service. The instrument is divided into two parts: a high voltage unit and a modulation unit, which makes it easy to use. The technical specifications include a Beam Supply Voltage of 190-420 VOID, bankable Current of 50 mA, Regulation of 0.5% for a 10% input variation, and Ripple of Repelled Supply Regulation. Additionally, it features Filament Supply Over-Load Trip Current, Modulation Frequency Range, Amplitude External Display with less than 5m Vrms and -10 to -240VDC variable amplitude.

The text below describes the features and specifications of a device, including adjustable Void, RNA AM, and FM capabilities. It also mentions a digital display for beam voltage and current, a meter selector, connectors, power supply dimensions, and front panel controls. The text indicates that the device is part of a Microwave lab with a subject code SEC 704. The front panel control in Figure 2 includes a power button for supplying power to the adulating signal. The text is aligned to justify and contains .

The Microphone Modulation Selection switch allows you to choose different modulation types. In OCW mode, no modulation signal is applied to the beam voltage. In AM mode, a square wave modulating signal is applied to the beam voltage. In FM mode, a sweep modulation is applied to the beam voltage. In Ext mode, an external modulating signal can be used for modulation or the beam current through the BANC connector. The AM modulation frequency is controlled by a frequency

potentiometer, which ranges from 500 to 2000 Hz. The amplitude of the square wave modulating signal can be controlled by an amplitude potentiometer, which goes from O (zero) to puppy.

The FM modulation, also known as frequency densitometer, controls the frequency or sweep modulating signal (50-150 Hz's). The amplitude potentiometer controls the amplitude or sweep modulating signal ( O - IPPP). The 8 pin octal socket has specific pin assignments. Pin 8-1 is for the beam voltage, Pin 8 for the repelled voltage, and Pin 2-7 is for the heater voltage. Pins 6, 7, 8, and 9 are reprogrammable and can be adjusted using a potentiometer ranging from -Pivot -IV DC. The beam voltage can also be adjusted using a potentiometer ranging from IV DC to 420 V DC. The meter select switch is used for selecting the display mode. It can show beam voltage (volts) in V mode, beam current (ma) in I mode, and repelled voltage in volts in REP mode. The display is used for monitoring the am voltage (in volts), repelled voltage, and beam current (ma). The beam voltage ranges from 190 V to 420 V DC, the reprogrammable voltage ranges from -10 V to -240 V DC, and the beam current ranges from 0 to 50 ma. On the rear panel, there is an external audio option where you can connect an external modulating signal using the External BANC provided on the front panel. If the audio option is selected, you can also connect a microphone to the audio input socket on the front panel for giving a modulating signal. The FM output is for observing the sawtooth signal used

for FM modulation. The heater adjust control allows for changing the heater supply after unsealing the cap. This equipment is used in microwave laboratories and has a code SEC 704 1.4.3 SIR Meter MIX. The SIR meter MIX is a high gain low noise, tuned voltmeter operating at a fixed frequency. It is designed for making standing wave measurements in conjunction with a suitable detector and slotted line or waveguide section.

This text can beand unified as:
This device has multiple uses, including functioning as a null detector in a bridge circuit and as a fixed frequency indicator. When used with square law devices like crystal diodes, it is calibrated to directly display SIR or db. It is specifically tuned to operate within the range of GHz to 1020 Hz to prevent any harmonics caused by the line frequency.

Technical Specifications Display:
- Sensitivity
- Noise Level Range
- Input Display Select
- LCD (16 X tune-up impedance)
- Less than db n db steps
- Un-biased low and high impedance crystal biased crystal (2000 and Instrument Modes)
- SW c External Mode : 10 approval external Y U- II Normal Loll PC (tans Moe can De uses nullity Gun based bench)
- Adjusts the reference level, variable range 0-db (approximately)
- BANC (F) OHIO'S ± 230 volts AC ± 10%, GHZ
- 290 x 216 x 115 Front panel control EXPO. NO : 01
Gain Control Input Connector
Input Frequency Power Dimension (mm)
Figure 3
1. 2. 3.

Power: Push button switch for supplying power to the instrument.
Crystal: An input impedance selector switch for low and high inputs, i.e. High ASK-Low 2000.
Mode select: This switch is used to select different modes of the SIR meter.
Modes are: 7 Engineering Subject-Microwave

lab Sub. Code- SEC 704 Expo. No : 01
Normal: In this mode, the 1 KHz square wave detected output is given to the input of the SIR meter. All measurements of gain and SIR should be measured in this mode.
Audio: Select this mode if the input of the pin modulator is an audio signal.
PC: Select this mode if the input of the PIN modulator is PC data. This mode can be used with a monolith gun-based bench.
SIR/db: This switch is provided to select display modes, either displaying in db power or SIR of the device.
Audio Output: This socket is provided for connecting headphones.
Input: BANC (Female) connector for connecting the signal to be measured.
Gain Coarse: A control for adjustments of the meter or any other convenient reading.
Gain Fine: A control for fine adjustments of the meter or any other convenient reading.
LCD display in SIR: An LCD display for measuring SIR and gain.
Range Switch: A seven-position attenuator minimum in 10 db steps.

The Rear panel Control PC Interface allows for connecting the RESTS cable for PC communication. To adjust PC to PC communication, use the Comparator Adjust potentiometer to ensure that output BANC provides the PC signal achieved from the transmitter PC. The detected signal can be observed on CROP from output BANC. The Operating Theory and Instructions state that for SIR measurement, the following equipment is required: 1. Signal Source - the signal source should cover the desired frequency range and be amplitude modulated at the operating frequency of the SIR meter.

The use of square wave modulation is common to minimize the impact of harmonic and frequency modulation. It is important to minimize interaction

between the oscillator and the load in any application, which may require the use of an isolation device. Additionally, when connecting the source to a slotted section, cables or waveguides should be used to match the source impedance over the desired frequency range. The slotted section itself should cover the desired frequency and have a precise scale or indicator.

The detector used in the measurements should be a square law device, such as a Barrette or a crystal diode, which operates at low signal levels and gives an output proportional to the RF power input. While a Barrette can function reasonably well as a square law detector at low signal levels, this cannot be said for crystal diodes in general. However, crystals have considerably better sensitivity compared to Barrettes, so Tanat crystals are used as detectors for Tort's R measurements.

Various terminations, such as a fixed and a movable short circuit, are required to establish reference points and help calibrate the test setup.

To measure the standing wave ratio (SIR), keep the SIR/db switch at the db position. The measurement involves probing at a voltage maximum position and adjusting the gain to obtain a reading of 0 dB, which corresponds to an SIR of 1. By switching the SIR/db switch to the SIR position, the SIR can be read directly. Move the probe along the slotted line to a voltage minimum or gain minimum and note the corresponding reading at the SIR position. The SIR value is shown directly on the LCD display.

Engineering Subject: Microwave Lab
Subject Code: SEC 704 Expo.

There are certain cases, particularly in the field of design and development, where it is important

to have thorough knowledge of the terminating equipment. One way to obtain this knowledge is by measuring the SIR and phase in the standing wave pattern. Usually, the impedance characteristic of the dad is determined by measuring the location of the voltage minimum. This location is then compared to a shifted position of the voltage minimum that occurs when a known load replaces the load being tested at a reference point on the slotted line. The distance between these two minima is recorded on a smith chart in order to determine the reactive component.

For the sake of convenience, the known load is typically a short circuit or a shorting plate, and the load connection serves as the reference point. When it comes to slotted line work, it is generally advisable to minimize the depth to which a sampling probe penetrates into the line. The power drawn by the sampling probe distorts the standing-wave pattern. As the probe penetrates further, this distortion tends to become more pronounced. This phenomenon can be understood by considering the probe as an admittance that diverts current from the line. The impedance in the standing-wave pattern varies along the line, with maximum impedance occurring at a voltage maximum and minimum impedance at a voltage minimum.

The shunt admittance of the probe decreases the impedance and results in a lower measured SIR compared to the actual SIR. This also shifts the maxima and minima from their neutral position. The shift is more significant at a voltage maximum than at a voltage minimum. Additionally, the probe absorbs power, affects the standing-wave pattern, and causes reflections in the line. These reflections travel towards

the signal source and, if the signal source is not matched, they are reflected towards the load. This leads to additional errors in low SIR measurements.

An exception to the minimum penetration rule occurs when there is a desire to examine a voltage minimum in a high SIR measurement. In this case, some tolerance for greaseproof penetration is allowed because the voltage minimum corresponds to a low impedance point in the line. However, substantial probe penetration is only tolerable at a voltage minimum. Precautions should be taken when using crystal detectors. For optimal sensitivity, select a ten Input Impedance wanly that provides maximum sensitivity with an unloaded crystal. Typically, the STALL 200 ohm position will yield the best sensitivity.

However, in the STALL-200 K ohms position, some crystal diodes may provide a higher output. It is ideal to achieve maximum sensitivity in order to minimize probe penetration in the slotted line. The following are the operation procedures for low SIR measurements (10 and below):

a. Turn on the instrument and allow approximately 5 minutes for it to warm up for maximum stability.

b. Select Normal mode using the Mode select option.

c. Set the Crystal Switch to the desired detector type, in this case, ohm.

d. Connect the detector cable to the input of the meter.

e. Set the Gain (Coarse) control to maximum power.

f. Set the range switch to either 40-db or 50-db position.

g. Adjust probe penetration to obtain the maximum reading and peak the meter reading by adjusting the modulation frequency of the signal source.

h. Reduce probe penetration to maintain the reading on display and peak the meter reading by tuning the probe detector.

i. Reduce the

gain control knob or attenuator to keep reading on display while peaking the meter reading by moving the probe Cambridge along the line.

j. Adjust Gain controls and output power from the signal source until a reading of exactly 0 Db is obtained.

k. Calculate the SIR (Signal-to-Interference Ratio) which is equal to I.E. SIR=I.

Move the probe Cambridge along the line to obtain the minimum reading in db, without disturbing the probe or any setting. Now keep SIR/db switch at SIR position. Read SIR, which is directly the SIR of the load. Note: 1. If the reading at the minimum is less than-db on the meter, then the meter displays Switch Range, so we have to switch to the next higher sensitivity anger (clockwise). 2. If the reading at the maximum is more than O db on the meter, then the meter displays Over Range, so we have to switch to the next appropriate range (anticlockwise). 3. However, all readings on the display in db must be added in the range selector switch position.

When the SIR is high (above 10), increasing the probe coupling is necessary to obtain a reading at the voltage minimum. However, this high coupling at the voltage maximum can cause deformation of the pattern and lead to reading errors. Additionally, there is a risk of error due to changes in detector characteristics at higher R.F. levels. The double minimum method involves determining the electrical distance between points where the output is double the minimum. To perform this method: repeat steps stated in the low SIR measurement procedure, move the Cambridge probe along the line to obtain the minimum reading

and note its position, adjust gain controls for a reference reading of 3.Db (or any other chosen reference), move the Cambridge probe along the line to obtain a reading of 0.Db on each side of the minimum and record these positions as del and do, respectively. Measure the distance between successive points manually by shortening the line, and substitute this distance into the expression SIR = O (where Go is the guide wavelength and del and do are the locations of the twice-minimum points) to calculate SIR.

The use of a calibrated variable attenuator between the signal source and the slotted line is another method to measure high signal-to-interference ratios (SIRs). This method effectively addresses the issue of probe loading by setting the probe around a voltage minimum where larger probe loading can be tolerated. However, it does not eliminate the impact of detector characteristics.

Adjust the attenuator to maintain the rectified output of the crystal diode at the same voltage at both the minimum and maximum points. The difference in attenuator settings represents the SIR in db. To measure a low SIR, repeat the steps below:
1. Move the probe Cambridge along the line.
2. Adjust the attenuator to achieve a convenient indication on the meter for a voltage minimum, and take note of the attenuator setting.
3. Continue moving the probe along the line to a voltage maximum.
4. Adjust the attenuator to obtain the same indication on the meter as previously established in step 2, and take note of the attenuator setting.

The SIR can be measured directly in decibels (db) by subtracting the second reading from the first. Although this approach compensates

for variations in detector characteristics due to the square Law, the issue of probe loading still persists. It is important to exercise caution and ensure minimal probe penetration. In terms of probe loading, it is preferable to locate the voltage minimum rather than the voltage maximum, as the impact of probe loading is reduced at the minimum.

However, determining the location of the voltage minimum accurately through a single measurement, especially with low SIR, is often imprecise due to its broadness, making it difficult to identify the true minimum position. To accurately locate the voltage minimum, a method entails obtaining the position of the probe Cambridge at two equivalent output readings on both sides of the minimum and then calculating the average of these deux readings.