JNTU B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008
( Common to Electronics & Communication Engineering and Electronics &
1. (a) An air field rectangular wave guide has dimensions of a = 6 cm, b = 4 cm.
The signal frequency is 3 GHz. Compute the following for TE10, TE11 modes.
i. Cut off frequency
ii. Wave length in the waveguide
iii. Phase constant and phase velocity in the wave guide
iv. Group velocity and wave impedance in the wave guide.
(b) Discuss the methods of excitations of modes in the rectangular wave guide.
2. (a) With a schematic diagram, explain the construction of a micro strip line.
(b) Mention the advantages of strip lines over other transmission lines.
3. (a) Show the attenuation produced by rotary vane attenuator is given by – 40 log
(b) Describe in detail about linear phase changer.
4. What is a Gyrator? Describe how isolators can be realized by using Gyrators and
Hybrids. Give the S matrix for an ideal Gyrators.
5. (a) Give the analysis of reflex klystron & derive the expression for repeller voltage
Vr interms of l,n & Va.
(b) Explain clearly the classification of microwave sources.
6. (a) Derive the Hartree anode Voltage equation for linear magnetron.
(b) A linear magnetron has following operating pars:
Vo=15KV, Io=1.2A,f=8GHZ, Bo= 0.015 wb/m2, d= 5CM,h=2.77CM. Calculate
i. Electron velocity at hub surface
ii. phase velocity for synchronism
iii. Hartree anode Voltage.
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. Write short notes on:
(a) Measurement of low and high VSWR.
(b) Measurement of phase shift.