GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- VI EXAMINATION — SUMMER 2020
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Subject Code: 2161003 Date:27/10/2020
Subject Name: ANTENNA & WAVE PROPAGATION
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1
(a) Explain the polarization of waves and describe elliptical polarization. 03
(b) Discuss the antenna field zone. 04
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(c) Define Antenna and enlist its functions. Compare it with transmission line. 07
Q.2
(a) Determine the distance from short dipole operating at IMHz at which radiation filed is 4 times the induction field. 03
(b) How does the Friis transmission theory help to determine loss between the two antennas located in free space? Explain with necessary formula and theory. 04
(c) Define the following terms.(draw necessary figures and write equations if any) 07
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- Front-to-back ratio
- Resolution
- Antenna apertures-physical and effective apertures
- Beam efficiency, stray factor
- Radiation resistance
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OR
(c) Starting from retarded current, derive an expressions for electric and magnetic components of a short dipole antenna if the spherical system is defined in r, ? and f. 07
Q.3
(a) Estimate directivity of an antenna with ?HP=2° and fHP=1°. Find gain of this antenna if efficiency factor k=0.5. 03
(b) Explain the experimental setup for the measurement of Gain of antenna. 04
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(c) Enlist various types of horn antennas. Describe their functioning. Explain corrugated horn antenna. 07
OR
Q.3
(a) Explain the principle of Folded dipole antenna with clean and neat figure. 03
(b) Explain how log-periodic antenna is works as broadband antenna. 04
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(c) Define Pattern Multiplication principle. Using it, explain radiation pattern of 4 isotropic elements fed in phase, spaced ?/2. 07
Q.4
(a) Explain reflector- lens antenna. 03
(b) Explain practical design consideration for the helical antenna. 04
(c) Describe the working principle, design and applications of microstrip patch antenna. Explain the physical significance of fringing field. 07
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OR
Q.4
(a) Explain Cassegrain feed with necessary figure. 03
(b) Compare the far field equations of small loop with short dipole. 04
(c) Explain the construction and radiation characteristics of rhombic antenna and enlist its advantages and disadvantages. 07
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Q.5
(a) Explain multihop propagation briefly. 03
(b) Explain Babinet’s principal. 04
(c) Explain the Different modes of Radio wave propagation. 07
OR
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Q.5
(a) Explain the features of Yagi Uda antenna 03
(b) Define the following terms.(draw necessary figures) 04
- Maximum usable frequency
- Skip distance
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(c) Explain the different layers of atmosphere. 07
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