ANTENNA AND WAVE PROPAGATIONS
SEM-V, 2012-13
B.TECH EXAMINATION
UTTARAKHAND TECHNICAL UNIVERSITY
(UTU)
Time: 3 Hours
Total
Marks: 100
Attempt any four of the
following:
- Define Gain and Beam width of an antenna.
- Explain the term " Antenna Impedance" and”
Radiation resistance".
- An antenna has a radiation resistance of 72 Ohms, a
loss resistance of 8 Ohms and a power gain of 12 dB. Determine the antenna
efficiency and its directivity.
- Write in brief the working of Yagi Antenna.
- Discuss the term " Linear Polarization" and
"Elliptical polarization"
- Determine the electric field at a point "p"
due to doublet of length "dl". Obtain the expression for
radiation resistance (Rr) of such doublet.
Attempt any two of
the following:
- Derive an expression for effective aperture area
of an antenna. Calculate the maximum effective aperture area of antenna
which is operating at a wavelength of 2 meter and has a directivity of
100.
- A transmitter provides 15 W to an antenna having
12 dB gains. The receiver antenna has a gain of 3 dB and the receiver
bandwidth is 30 kHz. If the receiver system noise figure is 8 dB and the
carrier frequency is 1800MHz, find the maximum T-R separation that will
ensure that a SNR of 20 dB is provided for 95% of the time. Assume n =4, σ=8
and do =1 km.
- A vehicle receives a 900 MHz transmission while
traveling at a constant velocity for 10 s. The average fade duration for a
single level 10 db below the rms level is 1 ms. How far dose the
vehicle travel during the 10 s interval? How many fades dose the signal
undergo at the rms threshold level during a 10 s interval? Assume that the
local mean remains constant during travel.
Attempt any two parts of
the following:
- Show that the magnitude (envelope) of the sum of two
independently identically distributed complex (quadrature) Gaussian
sources is Rayleigh distributed. Assume that the Gaussian sources are zero
mean and have unit variance.
- Define Isotropic radiator. Calculate the directivity of
an Isotropic antenna.
- Differentiate between Broad-side array and End-fire
array. Sketch their radiation pattern. Under what condition will the
pattern be unidirectional?
Attempt any two parts of
the following:
- Discuss in brief the working principle of parabolic
reflector antenna and mention its area of application. Find the
diameter of a dish antenna that will from a beam having a 0.5o
half-power beam width at a frequency of 8.2 GHz. Assuming an efficiency
constant k = 0.6, calculate the antenna gain and effective aperture.
- Derive the total power radiated by half wave dipole.
Also derive an expression for the gain of it.
- Write the ranges for various layers of atmosphere.
Explain the effect of Earth's Magnetic Field on Radio wave
Propagation.
Attempt any two parts of
the following:
- Describe how the radiation pattern and radiation
resistance of given antenna can be measured experimentally.
- Explain :
(i) Skip Distance
(ii) Optimum Working Frequency
(iii) Fading - Write in brief on:
(i) Normal E region
(ii) Sporadic E region
(iii) Various layers of Ionosphere.
----------utu previous year question papers of B.tech, Bba, B.com, B.sc and Mba old year question papers Uttarakhand technical University (UTU).-------------------------------
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