Jawaharlal Nehru Technological University Kakinada 2007 B.Tech Electronics and Communications Engineering ANTENNAS AND WAVE PROPAGATION - Question Paper

Code No: R05310403 Set No. 1
III B.Tech I Semester Regular Examinations, November 2007
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) Draw the Dual characteristics of an antenna.
(b) discuss the Radiation from 2 wire. [8+8]
2. (a) Derive the expressions for electric field in case of short current element and
hence find the conditions for the field to be in Franhofer region.
(b) obtain the distance from a radiating element with 60Hz current such that radi-
ation and induction fields are equal. [10+6]
3. (a) A linear broadside array consist of four identical equal in phase point source with
?/3 spacing. compute and plot the field trend. Also obtain the directivity
and beam width.
(b) What is optimum spacing used in parasitic array? Why. [12+4]
4. (a) Write short notes on “Helical Antenna”.
(b) Derive an expression for radiated electric field strength of a traveling wave
radiation of length ‘l’. [8+8]
5. (a) Sketch the current distribution of folded dipole and obtain out input impedance
when 2 legs have unequal diameters.
(b) A Parabolic dish provides a power gain of 50dB at 10GHz, with 70% efficiency.
obtain out
i. HPBW.
ii. BWFN, diameter. [8+8]
6. (a) define the method of measuring the gain and radiation trend of an an-
tenna.
(b) A standard gain horn antenna with a power gain of 12.5, is used to measure the
gain of a large directional antenna by comparison method. The test antenna
is connected to the receiver and an attenuator adjusted to 23dB in order to
have the identical receiver output. obtain out the gain of the large antenna. [8+8]
7. (a) define the following:
i. Space wave propagation.
ii. Duct propagation.
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Code No: R05310403 Set No. 1
(b) VHF communication is to be established with a 50watt transmitter at 100MHz.
compute the LOS distance if the heights of transmitting and receiving an-
tennas are respectively 50m and 10m. Assuming the capture area of the
transmitting antenna is 25sqmts, compute the field strength at the receiving
neglecting ground reflected wave. [8+8]
8. (a) explain the characteristics of F1 and F2 layers.
(b) explain the reasons for reduction of field strength in sky wave propagation.
[8+8]
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Code No: R05310403 Set No. 2
III B.Tech I Semester Regular Examinations, November 2007
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &

Earning:   Approval pending.