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Derive an expression for effective aperture area of antenna. Calculate the maximum effective aperture area of antenna which is operating at a wavelength of 2 meters and has a directivity of Define Antenna Efficiency. Write note on radiation pattern. What is radiation intensity and explain in terms of poynting vector?
Explain directivity of an antenna. Find out the radiation resistance of a? Define power gain and write down the relation between directive gain and power gain. Define radiation resistance and write down the expression for it. Differentiate antenna bandwidth and beam width. Define beam solid angle and antenna beam efficiency. An antenna has a radiation resistance of 72 Ohms, a loss resistance of 8 Ohms and a power gain of 12dB. Determine the antenna efficiency and its directivity.
Define Terminal impedance. State reciprocity theorem and briefly explain it. Calculate the radiation resistance of short dipole. Calculate a maximum effective aperture of a half wave dipole. Calculate the length of a half wave dipole antenna meant to have correct half wave length at 60 MHz. Calculate the maximum effective aperture of a microwave antenna which has a directivity of Calculate the radiation resistance of an antenna which is drawing 15A current and radiating 5 KW. Calculate the power being radiate by an antenna having a radiation resistance of 50 Ohms and is drawing a current of 8A.
Calculate the radiation resistance of an antenna which is radiating W and drawing current of 5A. How much current does an antenna draw when radiating W and is having a radiation resistance of Ohms.
Mention the radiation and Induction field component for a small current element. Define poynting vector. What is effectiveness ratio? What is scattering loss aperture? Define effective length of an antenna. PART - B 1. Explain the retarded vector potential in detail.
Derive an expression for the power radiated by the current element and calculate the radiation resistance. Derive an expression for the far field component of a half wave dipole of an antenna. Explain the reciprocity theorem in detail. Derive an expression for the electric field and magnetic field due to a current element at a distance point in free space. At what distance in? At what distance is it times. What is an array and mention the various forms of antenna arrays?
What is a uniform linear array? What is Broad side array and draw its radiation pattern? What is End fire array and draw its radiation pattern? What is collinear array? What is parasitic array?
What is pattern multiplication concept? List some of the advantages of pattern multiplication. What is tapering of array? Write a note on Binomial array.
How the secondary lobes are eliminated? What is a Phased array? What is a smart antenna? PART-B 1. Write short notes on various forms of arrays i. Broad side array ii. End fire array iii. Collinear array iv. Derive the expression for the far field pattern of an array of 2 — isotropic point sources i Equal amplitude and phase ii Equal amplitude and opposite phase iii Unequal amplitude and any phase 3.
Explain the principle of Pattern multiplication. Explain the array of N- sources of equal amplitude and spacing- Broad side case i. Direction of pattern maxima ii. Direction of pattern minima ii. Beam width of major lobe 5. Explain the array of N- sources of equal amplitude and spacing- End fire case i Direction of pattern maxima ii.
Direction of pattern minima ii Beam width of major lobe 6. Write short notes on i. Binomial arrays ii. What are the applications of loop antenna? Give the reason for poor radiation of a loop antenna. Distinguish between sectorial and pyramidal Horn antenna. What are the advantages of folded dipole?
What is a folded dipole? What are its important properties? Draw the structure of Log- periodic antenna. What is a Yagi — Uda array? Why is flaring required in Horn antennas? What is primary radiation and secondary radiation as applicable to parabolic reflector?
What is the reason for using Yagi antenna for TV broadcast reception? What are the applications of Yagi — Uda antenna? How does a parabolic reflector provide very high gain? What is a parasitic element? How does it act when length is greater than and smaller than? What is cheese feed as applicable to parabolic reflectors? Mention the antennas used in medium frequency range. How is a high frequency dipole antenna fed and matched with driving source?
Sketch the diagrams of various types of Horn antennas. What are Traveling wave antennas? Distinguish between resonant antenna and TWA? Distinguish between standing wave antenna and TWA? Define Spill over. What is meant by smart antenna? What is the principle of microwave antenna? Define pitch angle. What are the parameters to be considered in the design of an helical antenna?