Jawaharlal Nehru Technological University Anantapur 2011-2nd Year B.Tech Electronics and Communications Engineering Antennas and Wave Propagation s, - Question Paper

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY, Anantapur
ans Any 5 ques.
All ques. Carry Equal Marks Max Marks:80

1. (a) describe the terms:
i. Beam Width
ii. Side Lobe Level
iii. Polarization
iv. Effective Aperture Area.
(b) What is the effective length of an antenna. Determine the effective length of a half wave dipole antenna? [8+8]

2. (a) Assuming the expression of radiation fields for alternating current element,find out its radiation resistance. discuss the significance of the term Rr?
(b) An antenna whose effective height is 100 meters at a frequency of 60KHz radiated 100KWof power. Determine the strength of the electric field at a distance of 100km from the antenna. Neglect the ground effect and atmospheric losses.? [8+8]

3. (a) calculate the principle beam width for broadside and end fire array?
(b) A uniform linear array consisting of isotropic radiators spaced half wavelength apart has 10 elements, every element carries 0.5 amperes. compute the width of principle beam and maximum power radiated if operated as
i. Broadside array
ii. End fire array. [10+6]

4. (a) discuss the construction of Rhombic Antenna with balloon and termination.
Draw the radiation trend of rhombic antenna
i. over perfectly conducting plane.
ii. in the presence of earth.
(b) Derive electric field expression for Non Resonant antenna? [8+8]

5. (a) For what mouth diameter and capture area of a paraboloid reflector is a BWFN of 120 found when it is operated at 2.5 GHz?
(b) define the cassegrain feed mechanism of a parabolic reflectors? [8+8]

6. (a) What is an electromagnetic horn antenna? elaborate its applications? The length of an E-plane sectoral horn is 15cms. Design the horn dimensions such that it is optimum at 10GHz?
(b) compute the minimum distance needed to measure the field trend of an antenna of diameter 2m at a frequency of 3GHz. Derive the necessary equation? [8+8]

7. (a) Show that MUF of ionized layer is provided by fcp1+(D/2h)2 for flat earth.
(b) explain the following:
i. Ionospheric Storms.
ii. Sudden Ionospheric Disturbances. [8+8]

8. A television transmitting antenna mounted at a height of 120m radiates 15kw power equally in all directions in azimuth at a frequency of 50MHz. compute
(a) the maximum LOS range.
(b) the field strength at a receiving antenna mounted at a height of 16m at a distance of 12km.
(c) the distance at which the field strength decreases to 1mv/m. Derive the formulas used. [7+4+5]

Earning:   Approval pending.