KIIT University 2008 B.Tech Electronics and Tele-Communication Engineering Antenna and wave propagation - Question Paper
SEE THA ATTACHEMENTS beneath..
USE PICASA IMAGE VIEWER FOR BETTER OUTPUT.
YfTak
AW* EC 604 <E*TC)
SIXTH SEMESTER EXAMINATION-2008
ANTENNA & WAVE PROPAGATION [ EC 604 ]
Time: 3 Hours
Answer tuty SIX questions including Question No. I which compulsory. Thefigure* Ac margin Indicate full marts. m required to give their answers in their own words as far as prtuUrM* and of ad parts of" i should be answered at one place only.
1. Answer the following questions:
(2x10
a) State the four Maxwells equations in time domain notation.
b) Determine the magnetic field strength in free-space rf the electric field strength of a plane wave is 1 v/m.
c) A power of 100 watt is incident in a load of a loss-less transmission line. The measured VSWR at load is 1.18. Determine the reflected back power.
d) The radiation resistance of an antenna is 72 ohm and loss resistance is 2 ohm. What would be the directivity in dB if the power gain is 16?
e) A mast antenna consisting of a 50 meter long vertical conductor operates over a perfectly conducting ground plane. It is base-fed at a frequency of 600 KHz. Determine the radiation resistance of the antenna.
(i)
KHT-W2008/Spring Uni Stmtlltr f ianmmion-lOOS
I) DetBrr*irte the minimum distance forfar-feld pattern
measurement at 10 GHz far a parabolic reflector 0 antenna with diameter of 3 nfr.
g) A radio Station worts ai 800 KHz and uses AM What is the Iransmifling antenna used if this is a public broadcast system?
h) Determine ihe maximum usable frequency of an ionospheric layer at 45* angle of itdefence and wrtfi 9 MHz ciUical frequency
i) Sbte the principal application of Horn Antenna and about Ihe shape of tadabon pattern.
j) A pulseat2MHzisttansmiledifmi'd&. The reflected pulse from the Ionosphere reaches the ground after a delay of 1.5 m sec What would be the virtual height of Ihe ionosphere?
ElalnfcefolkavwigpararneterBin relation to antenna. [2x4
(a) Bearn width (b) Percentage band width
(c)Antennatemperature (d)Stub
a) Stow U\at the inpul resistance ofa A/2 folded dpote I4 antenna is tour times that of single half-wave dipole
b) Calculate the dimensions of elements of a Yagi-Uda 4* array antenna that has a directivity of 12 dBi al 145
MHz. Consider at least six diedors to achieve such directivity.
c) Why do we generally use a folded dipole instead of a simple dipole for the reception of TV signals?
4. a) What is a log periodic array antenna? Why is it so
named? Explain its operations and applications.
b) What Is monopole antenna? Sketch Its geometry, dipole equivalent and the radiation pattern.
5. a) What do you mean by polarization in anterma?
b) How are LHCP and RHCP produced in antenna? Explain briefly.
c) The instantaneous electric field vector of a wave, propagating along the positive r-directon, at a fixed point in space is given by,
E(t) a* cos(wt) -at2cos(wt+*/4) v/m
Plot this vector as a function of time and describe the polarization of the wave.
6. a) What is Frw Transmission formula ? Derive It
K!IT-W}WV5p**t W .Vtnulir tinmrniliooJOM
b) An antenna having a gain of 12 dBi is used to recent a 24 GHz signal propagating in free-space if the power density of the wave is 25 jiw/m2, calculate:
(i) the power received into a matched load of 50 ohm connected to this antenna.
(ii) Express this power in dBm.
c) What is Anechoic Chamber? State its necessity in antenna community.
7. a) Describe the ground-wave propagation. What is the
angle of tilt? How does it affect the field strength at a distance from the transmitter?
b) Explain the concept of the skip distance' and virtual height in the ionospheric propagation.
8. a) Write short notes on theD. E, F,and F2layereofthe
ionospheric propagation and explain their seasonal variations.
b) Explain the phenomenon of duct propagation. What are the atmospheric condition under which duct propagation can take place?
c) State the factors that lead to fading in ionospheric propagation.
X X X XX
KllT'J/2008/Spnng KnJ S*meinr Kjutminanom-HM
|
Attachment: |
| Earning: Approval pending. |
