Jawaharlal Nehru Technological University Kakinada 2008 B.Tech Electronics and Communications Engineering ANTENNAS AND WAVE PROPAGATION - Question Paper

III B.Tech I Semester Supplimentary Examinations, February 2008
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
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1. (a) discuss the subsequent terms:
i. Beam Width
ii. Omni Directional trend
iii. Side Lobe Level
iv. Radiation resistance
v. Field trend of antenna.
(b) describe the terms Directivity and Power Gain. Show that the Directivity of a
short current element is 1.5. [8+8]
2. (a) Starting from the fundamentals, derive an expression for radiated electric field
for half wave dipole and sketch the field strength trend.
(b) Prove that leff(transmitting) is identical as leff(receiving) for any antenna where
leff is effective length of an antenna. [8+8]
3. (a) How an unidirectional trend is found in an end fire array? discuss in
detail.
(b) List out the mathematical relations for a N element half wavelength spaced
binomial array. Hence obtain the directivity, HPBW for N=20. [8+8]
4. (a) discuss how a rhombic Antenna is formed by a V antenna and an inverted V
Antenna.
(b) discuss the cause why length of a traveling wave radiation is multiple of half
wave length. [8+8]
5. (a) explain the application of the Image antenna concept to the 900 corner reflec-
tor.
(b) What is a parabolic cylinder antenna? Derive an expression for field distrib-
utions on the surface of reflector. [8+8]
6. (a) What is Zoning? elaborate its advantages?
(b) explain the applications of Horn Antenna. Sketch the sectoral horns. [8+8]
7. (a) Show that Ionosphere act as a variable refractive index medium.
(b) A radio link has to be established ranging from 2 earth station at a distance of
25000kms. If the height of ionosphere is 200kms and its critical frequency is
5MHz. compute the MUF for the provided path. Also compute the electron
density in the ionosphere layer. [8+8]
1 of 2
Code No: R05310403 Set No. 1
8. (a) A police radio transmitter operating at a frequency 1.69GHz is needed to
give a ground wave having a strength of 0.5mv/m at a distance of 16km.
The transmitter antenna, having an efficiency of 50% produces a radiating
field proportional of cos?. The ground wave has s= five × 10-5 mho/cm and er
= 15. compute the power transmitted.
(b) Derive the fundamental formula for free space propagation. [8+8]
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2 of 2
Code No: R05310403 Set No. 2
III B.Tech I Semester Supplimentary Examinations, February 2008

Earning:   Approval pending.