ANTENNA & WAVE PROPAGATION PAPER 4

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ANTENNA AND WAVE PROPAGATION (B.Tech 5th Semester,2122)

NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from
Section B and any two questions from Section C

Section-A Marks : 20

1(a) What is Retarded Potential ?
(b) What is beam efficiency ?
(c) Explain the effective aperture of an antenna.
(d) What is Aperture Efficiency ?
(e) What is duality of an antenna ?
(f) What is a point source?
(g) What are null directions of an array ?
(h) Explain the effect of troposphere on wave propagation.
(i) What is Ionosphere ?
(j) What is Virtual height ?

Section-B Marks:5 Each

2. Explain the radiation between a current element and an electric dipole.
3. Explain the quality of direction pattern of antennas.
4. Explain horizontak pattern in Broadcast arrays.
5. Obtain the pattern for four element broad side array.
6. Obtain the expression for effective aperture of an antenna.

Section-C Marks : 10 Each

7. obtain the expression for 1 : 3 : 3 : 1 binomial array field pattern and draw the pattern when d=λ/2.
8. Prove that the surface impedence of the earth is given by:

where all the symblos have their usual meanings.
9. What is an Ionospaher ? Determine effective ∑ and σ of an ionized gas and explain the reflection and refraction of waves by the ionospher.