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Antennas and Wave Propagation: III B. Tech I Semester Supplementary Examinations, May/June - 2017

The document discusses antennas and wave propagation. It includes questions about retarded potentials, directivity, end-fire arrays, yagi-uda antennas, microstrip patch antennas, shadow zones, radiation resistance, antenna efficiency, dipole antennas, linear arrays, array factors, rectangular patch antennas, helical antennas, folded dipoles, measuring antenna gain, the structure of the atmosphere, electron density variations, and sky wave propagation.

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79 views1 page

Antennas and Wave Propagation: III B. Tech I Semester Supplementary Examinations, May/June - 2017

The document discusses antennas and wave propagation. It includes questions about retarded potentials, directivity, end-fire arrays, yagi-uda antennas, microstrip patch antennas, shadow zones, radiation resistance, antenna efficiency, dipole antennas, linear arrays, array factors, rectangular patch antennas, helical antennas, folded dipoles, measuring antenna gain, the structure of the atmosphere, electron density variations, and sky wave propagation.

Uploaded by

prasanth
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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INJNTU.

COM
Code No: RT31045 R13 SET - 1

III B. Tech I Semester Supplementary Examinations, May/June - 2017


ANTENNAS AND WAVE PROPAGATION
(Electronics and Communication Engineering)
Time: 3 hours Max. Marks: 70
Note: 1. Question Paper consists of two parts (Part-A and Part-B)
2. Answering the question in Part-A is compulsory
3. Answer any THREE Questions from Part-B
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PART –A
1 a) Explain the term retarded Potential and retarded vector magnetic potential? [3M]
b) Define directivity of an antenna and Calculate the maximum effective aperture of a [4M]
microwave antenna which has a directivity of 900.
c) Explain End-fire array? [3M]
d) Explain operation of 3 element yagi - Uda antenna. [4M]
e) Explain the structure of micro strip patch antenna. [4M]
f) What is shadow zone and its effects on EM wave propagation [4M]
PART –B
2 a) How does “directivity” differ from the maximum gain? [4M]
b) The radiation resistance of an antenna is 80Ωand loss resistance of 10 Ω. What is [6M]
the directivity if power gain is 20?
c) Explain the term Antenna efficiency. How it is related with radiation resistance? [6M]

3 a) Derive an expression for radiation resistance of a λ/4 dipole antenna? [10M]


b) State and prove that the same antenna can be used for transmission as well as for [6M]
reception?

4 a) What are the conditions for linear array of N isotropic sources to radiate in end fire [6M]
and broad side mode?
b) Derive an array factor for two point sources centered at origin with equal amplitude [10M]
and equal phase? Graph its radiation pattern?

5 a) Explain the working and operation of Rectangular patch antennas with the help of [10M]
neat sketch.
b) Explain the importance of axial ratio of Helical antenna for circular polarization. [6M]

6 a) Explain the working of folded dipole? Show that its radiation resistance is [8M]
N2 x 73 Ω
b) Explain the method of measuring gain of an antenna? [8M]

7 a) Describe the structure of atmosphere? How electron density varies during day and [8M]
night?
b) What is sky wave propagation? Explain radio wave bending in ionosphere . [8M]
*****

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