B. Tech. IN ELECTRONICS AND COMMUNICATION ENGINEERING
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Term-End Examination
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December, 2011 BIEL-013 : ANTENNAS AND PROPAGATION Time : 3 hours Note :
Maximum Marks : 70
(i) Attempt any seven questions. Each question carries ten marks (ii) Use of scientific calculator is permitted
1.
For an antenna, define the terms Directivity and Gain. Derive the relevant expressions for these parameters.
10
2.
For an antenna of lossless end-fire array
10
compressing 10 isotropic point sources spaced Y4 and operating with increased directivity, the normalised field pattern is :
En = sin
sin (n (1/ 1 ) , where (2n) sin (IX) (
—1) — 71/n , dr = 7/2 , n=10, HPBW = 40°.
BIEL 013 -
1
P.T.O.
Calculate : (a)
Gain G
(b)
Approximate gain
(c)
Difference between the two
3. Explain the significance of the following with respect to point sources and arrays : 5+5=10 (a)
Field patterns
(b)
Phase patterns
4. Prove that the radiation resistance for a short electric dipole with uniform current is given by Rr = 790LX2 . Write the equation for its radiated
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power. 5. Explain Loop Antenna and prove that for a loop
10
antenna with radius 'a' : . !Ito E 4) — Jil(?, a sin 0) and 2r 13- a [I] H (I)= Ji(I5, a sin 0). 2r
6. Write the general properties of a parabolic reflector and compare it with a corner reflector. BIEL-013
2
10
7.
Explain space wave and surface wave. •
3+7=10
A ground wave of 0.5 mV/m at 20 Km distance is obtained from a transmitter operating at 2MHz. The vertically polarized field produced is proportional to cos0, 0 is the angle of elevation. Given antenna efficiency = 50%, 6 = 5 x 10 -5, Er =15. Determine E at the transmitting end.
Explain a Turnstile and a super-Turnstile Antenna 10. briefly with relevant diagrams. 10. Write short notes on any two : (a) Plasma Antenna. (b) Slot Antenna.
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and WiMAX (again, several bands are proposed). Many of these systems will be required to operate simultaneously. Multi-mode, multi-band operation presents a formidable challenge to mobile phone designers, particularly for the RF parts. Of these, the
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an elastic routing protocol, which enables to increase per-hop distance elastically according to the scalable beamwidth, while maintaining a constant average ...
A simple alternative to complex hardware design of adaptive antennas along with optimizing SNR is proposed by the application of genetic algorithms. Adaptive antennas are antenna arrays with phase angle associated with each element of the array. The
An effective thickness, which represents the electrical thickness of the substrate ... Engineering and Computer Science, University of Michigan, Ann Arbor, MI.
This kind of system is called a MIMO ... a SISO (Single-Input Single-Output) system that uses one transmit ... Today most high-rate wireless systems use MIMO.
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