Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 6th Semester (Sixth Semester) 2016-2017 NEN023 Antenna And Wave Propagation Question Paper
B.TECH.
THEORY EXAMINATION (SEM?VI) 2016-17
ANTENNA AND WAVE PROPAGATION
Time : 3 Hours Max. Marks : 100
Note : Be precise in your answer. In case Ofnumerical problem assume data wherever not provided.
SECTION ? A
1. Explain the following: 10 X 2 = 20
(3) Why directional antenna efficiency compared with Isotropic antenna, calculate the
directivity of isotropic antenna?
(b) List out which parameters to consider for receiving antenna design.
(c) What are the disadvantages of binomial array?
((1) Give the relation for field strength ,at a distance ?d? from transmitting antenna to show
that as ?d? increases ,electric field decreases
(e) Why sky wave propagation is not possible above 30 MHZ.
(f) List out difference between broadside and end fire array.
(g) Draw the unidirectional and bidirectional pattern for U=UmCOS G
(h) Find the directivity of an antenna radiator only over half sphere.
(i) Find out the power gain in db of a paraboloidal re?ector of open mouth aperture 10 X.
(j) Explain HPBW and BWFN ,give relation between them.
SECTION ? B
2. Attempt any five of the following questions: 5 x 10 = 50
(a) (i) Define aperture and effective aperture of antenna, If the gain of antenna is
reduced to Mt, what will be the effect of aperture.
(b) Find maximum power received at the distance of 0.5 km over free space lGHZ .
circuit consisting of transmitting antenna with 25 dB gain and receiving
antenna with 20 dB gain .input power of transmitting antenna is 150 W.
(b) Define antenna array .What is meant by the gain of an antenna ?Show that for a linear
array of ?N? isotropic point source equal amplitude and spacing, carrying equal currents
and in phase ,the normalized field is given by
1 SinN g
2
N Sin ?
11 0 rm
(c) (i) Define MUF and give its relation( for ?at earth) in terms of critical frequency ,
propagation distance D and height of layer .
(ii) At what frequency a wave must propagate for the D- region to have an index of
refraction 0.5 for N: 100 elec/c.c for D?region.
(d) (i) Explain the mechanism of radio wave bending by the ionosphere with neat
diagram .
(ii) Explain the structural details of ionosphere with neat diagram.
(e) (i) Make a detailed comparison between corner re?ector and parabolic re?ector.
(ii) Give the statement of reciprocity theorem in terms of antenna and give the
relation for Mutual impedance Zm between the two antennas.
(f) (i) Give the relation for far field pattern of binomial array by using the principle of
pattern multiplication.
P. T . 0.
(ii) For an end fire array having several half wave length long isotropic radiator is
to have Directivity 0f 30 .find the array length and width of major lobe
.what will be these values for a broadside array.
(g) (i) Derive far field expression for small loop antenna?
(ii) What is Yagi antenna? Design Yagi antenna of five elemenet for the frequency
band of 61?68 MHz.
(h) What is the principle of rhombic antenna? Draw its diagram and explain the design of
rhombic antenna to obtain maximum field intensity.
SECTION ? C
Attempt any two of the following questions: 2 x 15 = 30
3. (a) Show that the directiVity for an ordinary end?fire array of two identical isotropic point
sources spaced a distance d is given by
D = 2
. 27rd
1 + Sln 7
27rd [ /'L
(b) Define beam width of an antenna and show that its directivity is given by
D _ 41,257
_ 929%
4. (3) Define radiation resistance, Calculate the radiation resistance of short electric dipole
with uniform current and show that
RT: 80 7:2 (L002
(b) Define the term critical frequency, Virtual height ,skip distance, silence zone.
5. Write a short note on following:
(a) VLF and LF transmitting antenna
(b) Effect of earth on ground wave propagation.
(c) Frequency independent conical spiral antenna
This post was last modified on 29 January 2020