JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III ANTENNAS AND WAVE PROPAGATION Previous Question Paper (February - 2023 - R16)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Write the relation between effective aperture and directivity.
Answer
The relationship between the effective aperture (Ae) and directivity (D) of an antenna is given by the formula:
where λ represents the operating wavelength of the antenna.
Explain the concept of Retarded vector potential.
Answer
The Retarded Vector Potential accounts for the finite speed of electromagnetic wave propagation in free space. When a time-varying current source at a point source changes, the effect of this change does not reach a distant observation point instantaneously but is delayed by the time taken for the wave to travel the distance between them.
If the distance between the source point and the observation point is r and the velocity of propagation is c, the time delay is tr = r/c. The retarded vector potential A at the observation point at time t is defined as:
In this expression, J(r', t - r/c) is the current density evaluated at the retarded time tr. This concept is fundamental in antenna theory as it allows for the calculation of radiated fields by considering the phase shift introduced by the propagation delay across the antenna structure.
Why folded dipole antenna is used in yagi antenna?
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Comparison between axial mode and normal mode of helical antenna.
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What are the merits of Microstrip antennas?
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Explain the need of reflector antenna.
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Why array antennas are preferred over a single radiator?
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Define principle of Pattern multiplication.
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What are the factors that affect the propagation of radio waves?
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What is wave tilt? List all the factors that affect wave tilt.
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Part B
Derive the expressions for field components of an alternating current element located at the origin.
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The radiation intensity of an antenna is given by U(θ) = cos2θ; (0≤ θ≤900, 0≤ φ≤3600) Find i) HPBW ii) Beam width between first nulls (FNBW).
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Derive the expression for far field components of a small loop antenna.
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Explain about the operating principle of Helical antenna in Axial mode.
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Design and explain Folded dipole Antenna and their characteristics.
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What is electromagnetic horn antenna? What are the various types of horn? What are their practical applications?
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Design a 6-element yagi-uda antenna with folded dipoles operating with a frequency of 300 MHz.
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Compare different feed methods used for parabolic reflector antennas.
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Write about the designing procedure of rectangular patch antenna.
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Explain about the Reflector Antennas.
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Compare UHF and VHF antennas.
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What is linear array? Compare Broad side array and End fire array.
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What is binomial array antenna? What its basic principle of working? Mention the advantages and disadvantages.
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Explain how to measure the radiation pattern of simple dipole with neat experimental setup and also write what type of precautions has to be consider while measuring.
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Draw all the atmospheric layers and discuss about each layer in ionospheric Region.
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What are the different mechanisms of propagation of electromagnetic waves? Explain.
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Prove that the radio horizon distance between transmitting and receiving antenna is given by d (km)=4.12[√(ht)+√(hr)].
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