## December 17, 2011

### MICROWAVE ENGINEERING JNTU previous years question papers

MICROWAVE ENGINEERING JNTU previous years question papers

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

1. (a) Find expressions for the electric surface current density on the wall of a rectangular wave guide for a TE10 mode.
(b) A rectangular wave guide of cross section 5 cm × 2 cm is used to propagate TM11 mode at 9 GHz. Determine the cut off wave length and wave impedance.[8+8]

2. (a) Prove that a cavity resonator is nothing but an LC circuit.
(b) Derive an expression for Q of a cavity supporting TE101 mode. What is the resonant frequency of the cavity if each side of the guide is 3 cm? [8+8]

3. (a) Explain the operation of a directional coupler with the help of a sketch, showing the field lines at the junction.
(b) A 20 dB coupler has a directivity of 30 dB. Calculate the value of isolation.[8+8]

4. (a) What is Faraday rotation? Explain how a three port circulator operates.
(b) Write short notes on “Properties of S - matrix”. [8+8]

5. (a) Explain in detail bunching process & obtain expression for bunching parameter in a two cavity klystron amplifier.
(b) A reflex klystron is to be operated at a frequency of 10GHZ, with dc beam voltage 400v. Repeller spacing 0.1cm for 134 mode. Determine the maximum value of power & corresponding repeller voltage for beam current of 30mA.[8+8]

6. (a) In a circular Klystron , a=0.10m, b=0.40m, ß= 1.0 mT, Vb=5KV. Find the Hulls Cut-off VOltage & cut-off magnetic flux density.
(b) Compare & contrast TWT & Klystron amplifier. [8+8]

7. (a) Derive the criterion for classifying the modes of operation for Gunn effect diodes
(b) An n-type GaAs Gunn diode has following parameters
Electron drift velocity: Vd = 2.5 × 105m/s
Negative Electron mobility: µn = 0.015 m2/ v s
Relative dielectric constant: er = 13.1
Determine the criterion for classifying the modes of operation.

8. (a) Two identical 30dB directional couplers are used to simple incident and reflected power in a wave guide. VSWR=2 and the output of the coupler sampling incident power=4.5mW.What is the value of reflected power.
(b) Describe a microwave bench.

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