JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III ANTENNAS AND WAVE PROPAGATION Previous Question Paper (March - 2024 - 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
State reciprocity theorem related to antennas.
Answer
The reciprocity theorem for antennas states that if an antenna is used as a transmitting antenna, the ratio of the voltage applied at the terminals to the current at the terminals is equal to the ratio of the voltage induced at the terminals to the current flowing through the antenna when it acts as a receiving antenna in the same environment. Essentially, the receiving and transmitting patterns and the impedance of an antenna are identical regardless of the mode of operation, provided the medium is linear, passive, and isotropic.
Define (i) Beam efficiency (ii) Radiation Intensity.
Answer
(i) Beam Efficiency is defined as the ratio of the power radiated within the cone of the main beam to the total power radiated by the antenna. It provides a measure of how effectively an antenna concentrates its radiated energy into the main lobe.
(ii) Radiation Intensity (U) is defined as the power radiated from an antenna per unit solid angle. It is independent of the distance from the antenna and is expressed in watts per steradian (W/sr). Mathematically, it is given by:
where Wrad is the radiation power density and r is the distance from the source.
List the advantages of horn antenna.
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What is the condition for constructing optimum horn?
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What is Spillover?
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Write salient features of microstrip antenna.
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Differentiate Linear and Binomial arrays.
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How to increase the directivity of end-fire array?
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What is absorption?
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Write about directivity measurement.
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PART - B
Calculate the directivity D(θ,φ) for the three unidirectional sources with power pattern as U(θ,φ)=U0sinθsin2φ where U(θ,φ) lies between 0≤ θ≤ π and U0 is maximum radiation intensity.
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Explain the radiation mechanism in single wire antenna.
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Derive the electric and magnetic field components of half wave dipole.
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Explain the principle of pattern multiplication.
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Explain how the radiation pattern of folded dipole will be modified with the addition of a reflector and two directors parasitic elements.
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Write a short note on optimum horns.
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What are the Practical Design Considerations for Mono filar Helical Antenna?
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Explain the construction and working of microstrip antenna.
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Write about the applications of reflector antennas.
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List the applications of Microstrip antenna.
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Explain the construction and working of parabolic reflector antenna.
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Demonstrate the radiation pattern measurement.
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Draw the radiation pattern of a 10-element uniform linear end-fire array of isotropic point sources of spacing λ/2.
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Derive the expression for array factor of a linear broadside array of ‘n’ isotropic elements.
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Explain different sources of errors in antenna measurements.
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Write short notes on following: a) Maximum Usable Frequency (MUF) b) Skip Distance and c) Virtual height.
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What is Wave tilt? How does it affect the field strength at a distance from the transmitter?
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Find the relation between Maximum usable frequency and Skip distance.
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