JNTU
JNTU B.Tech III ANTENNAS AND WAVE PROPAGATION Previous Question Paper (October - 2020 - R13)
Answer any five questions. All questions carry equal marks.
Main
Explain the various antenna Parameters.
Answer
Antenna parameters define the performance characteristics of an antenna in transmitting or receiving electromagnetic waves:
- Radiation Pattern: A graphical representation of the radiation properties of an antenna as a function of space coordinates, typically showing field strength or power density.
- Directivity: The ratio of the radiation intensity in a given direction to the average radiation intensity over all directions.
- Gain: A measure that takes into account the efficiency of the antenna and its directional capabilities, defined as the product of directivity and radiation efficiency.
- Radiation Resistance: The equivalent resistance that would dissipate the same amount of power as the antenna radiates.
- Bandwidth: The range of frequencies within which the performance of the antenna, with respect to some characteristic (like impedance or gain), conforms to a specified standard.
- Beamwidth: The angular width of the main lobe, usually measured between half-power points (Half-Power Beamwidth, HPBW).
- Polarization: The orientation of the electric field vector of the radiated wave as a function of time.
Explain the antenna noise temperature.
Answer
Antenna noise temperature is a parameter used to quantify the noise power received by an antenna from its environment. It represents the temperature of a hypothetical resistor that would produce the same amount of thermal noise power at the antenna terminals.
The total noise temperature
Where
Derive an expression for the far field component of a half wave dipole of an antenna.
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Compare the fields of small loop and short dipole.
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Discuss the design considerations of pyramidal horn antenna.
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Write short notes on:
i) Folded dipole antenna ii) Yagi-Uda array
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Discuss about the helical antenna geometry, axial mode of radiation and its applications.
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Discuss different types of Horn antennas.
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Explain the features of corner reflectors.
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Explain the principle of operation of dielectric lens antenna.
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Discuss the construction of rectangular patch antenna.
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A parabolic reflector antenna with diameter 20 m is designed to operate at frequency of 6 GHz and illumination efficiency of 0.54. Calculate antenna gain in decibels.
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Define directivity. Give the procedure for the measurement of directivity.
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Explain near and far fields with respect to antenna measurements.
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Discuss the atmospheric effects in space wave propagation.
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Explain the following:
i) Virtual height ii) Skip distance iii) Multi-hop propagation.
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