# JNTU B-Tech II Semester Examinations Microwave Engineering, Apr/May 2008

JNTU PAPERS

JNTU B.Tech II Semester Examinations, Microwave Engineering,, Apr/May 2008

( Common to Electronics & Communication Engineering and Electronics &

Telematics)

Time: 3 hours Max Marks: 80

All Questions carry equal marks

SET-III

1. (a) Derive the wave equation for a TM wave and obtain all the field components in a rectangular wave guide.

(b) A rectangular wave guide with dimension of 3 × 2 cm operates in the TM11mode at 10 GHz. Determine the characteristic wave impedance. [8+8]

2. (a) What is the impact of skin effect on a micro strip line?

(b) Derive an expression for attenuation factor for ohmic skin loss. [8+8]

3. (a) Show the attenuation produced by rotary vane attenuator is given by – 40 log(sin?).

(b) Describe in detail about linear phase changer. [8+8]

4. (a) Explain the characteristics of ferrite materials.

(b) Derive the S – matrix for 4 port directional coupler when the coupling factor is 3dB. [8+8]

5. (a) What are the limitations of conventional tubes at microwave frequencies. Describe the construction & working of two cavity klystron amplifier.

(b) A reflex klystron having an accelerated field of 300v oscillates at a frequency of

10GHZ with a retarding field of 500v. If its cavity is retured to 9GHZ. What must be the new value of retarding field fro oscillations in the same mode to take place? [8+8]

6. (a) In a circular Klystron , a=0.10m, b=0.40m, ?= 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 |?n| = 0.015 m2/ v s

Relative dielectric constant ?r = 13.1

Determine the criterion for classifying the modes of operation. [8+8]

8. (a) The cablibrated power from a generator as read at the power meter is 25mw.

When a 3dB attenuator with a VSWR of 1.3/1 is inserted between the generator and detector what value should the power meter read.

(b) Compare the power ratio and RF substitution methods of measuring attenuation provided by the microwave component. [8+8]