M. Sc Electronics (Communication Science) (Semester II)
(CBCS) Examination, 2017
MODERN ANTENNA DESING
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Day Date: Wednesday, 19-04-2017 Max. Marks: 70
Time: 10.30 AM to 01.00 PM
N.B. Questions NO.1 and 2 are Compulsory.
Answer any three questions from Q.NO.3 to Q.NO.7
All questions carry equal marks.
Q.1 Objective Questions. 14
Choose the correct alternative given in the bracket. 06
An antenna have radiation resistance 73 and its total ohmic
loss resistance is 7 its efficiency is
81% 91% 71% None
2 Dipole antenna has maximum radiation in a plane.
Normal to the axis Both x
Far field region None i
3 Fresnel field region is also called region.
Reactive near field Radiating near field
Far field region None of the above
4 Which of the following is non uniform amplitude array
Broad side End fire
Binomial Harsen and wood yard
5 The advantage of the offset feed system is
Avoid aperture blocking Reduction in spill over
Increase in spill over None
6 Front fed parabolic reflectors suffer due to
Aperture blocking Both
Mismatch in main feed None
State True/False 08
Power pattern is half of the field pattern.
Beam area of a radiator is inversely proportional to the total
radiated power.
The vertical plane pattern of short dipoles and half wave dipole
is dumbbell.
Linear antennas are straight thin wire radiators.
Half wave dipole is derived from the /2.
Total charge in the array phase function
Resonant antenna carries current of standing wave.
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s
In lens antennas the spherical wave to plane wav is front is
achieved based on principle of Reflection.
SLR-RH 370
Q.2 Answer the following: 14
State some applications of folded dipoles. 05
Discuss patch antenna. Write down the advantages. 04
What are radiation pattern F/B ratio? 05
Q.3 Answer the following: 14
Write a suitable diagram, the construction and operation of a Yagi
antenna.
10
If the effective height of an aerial is 1/150th of the wave emitted
determine its radiations resistance.
04
Q4 Answer the following: 14
Derive the expression for relation between current and charge of
single wire. What are different conditions while radiation is possible
in single wire?
08
Explain Beam width of major lode 06
Q.5 Answer the following: 14
Describe the parabolic reflector used at micro frequencies? 08
Write short notes on Luneburg lens? 06
Q.6 Answer the following: 14
Define radiation intensity. The radial component of the radiated
power density is given by, Wrad ar Wr ar A0sin r2
08
Differentiate broad side End fire array? 06
Q.7 Answer the following: 14
Write detailed notes on 10
Parabolic reflectors
Log periodic antennas
Write a note on effective aperture of the antenna 04