30-10-2012, 12:50 PM
III B.Tech I Semester Regular Examinations - ANTENNAS AND WAVE PROPAGATION
WAVE PROPAGATION.pdf (Size: 96.38 KB / Downloads: 46)
1. (a) Draw the Dual characteristics of an antenna.
(b) Explain the Radiation from Two wire. [8+8]
2. (a) Derive the expressions for electric field in case of short current element and
hence obtain the conditions for the field to be in Franhofer region.
(b) Find 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 4 identical equal in phase point source with
λ/3 spacing. Calculate and plot the field pattern. Also find 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 find out input impedance
when two legs have unequal diameters.
(b) A Parabolic dish provides a power gain of 50dB at 10GHz, with 70% efficiency.
Find out
i. HPBW.
ii. BWFN, diameter. [8+8]
6. (a) Describe the method of measuring the gain and radiation pattern 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 same receiver output. Find out the gain of the large antenna. [8+8]
7. (a) Describe the following:
i. Space wave propagation.
ii. Duct propagation.