lab sheet microwave devices emg 2026 - Faculty of Engineering ...

Microwave Devices Faculty of Engineering EMG2026
PROCEDURE:
CAUTION 1: The RF power levels in the following experiments are not harmful, but a human eye
may be damaged by low level of radiation. Do not look into the waveguide at any time when the
equipment are on.
CAUTION 2: Klystron tube get extremely hot when it is operated and must not be handled by hand.
Measurement of Frequency and power with variation in repeller voltage
1. Set up the equipment as shown in Figure 4. Switch on the power supply and RF output. Wait a few
seconds for the Klystron tube to warm up.
2. Select squarewave modulation. Set the modulation level to maximum. Adjust the repeller voltage to
maximum and then decrease it slowly until the largest deflection (maximum power) is indicated on the SWR
meter.
3. Adjust the modulation frequency so that the SWR meter deflection is further maximised.
4. Set the slotted-line probe at about 2-mm protrusion depth and adjust the tuner stub/knob for proper
matching of the detector.
5. Set the variable attenuator at 5-mm micrometer setting. (The reading of the SWR meter should be
constant when the probe carriage is moved along the slotted-line waveguide.)
6. Adjust the gain knob of the SWR meter so that the needle points at 0 dB. After this, the zeroing knob
should be fixed.
7. Measure the repeller voltage from the connector at the rear panel of the Klystron power supply using a
multimeter and record the reading. The multimeter reading shall be multiplied by 10x to give the repeller
voltage.
8. Measure the frequency using the cavity wavemeter and record the result.
(Starting with the cavity wavemeter dial set to maximum clockwise, unscrew the dial slowly. At first there
will be little effect on the SWR meter reading until at one point the power will fall sharply. Read the
frequency indicated on the scale.)
You may also use the alternative method given in Appendix A for microwave frequency measurement.
9. Vary the repeller voltage.
10. Measure the repeller voltage and record the reading.
11. Measure the frequency using the cavity wave meter and record the reading.
12. Repeat steps 9-11 for the full range of repeller voltage.
13. Plot relative power level in dB versus repeller voltage.
14. Plot frequency versus repeller voltage.
Revision Sept 2010