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Friday, 6 December 2013

Antenna theory and design- model question paper for B.E/B.Tech



1(a) Write a note on directivity and gain of antennas. (4 Marks)
(b) What is a monopole? (4 Marks)
(c) Small loop antennas have considerable ohmic resistance. Explain. Mention some applications of Small loop antennas. (8 Marks)
(d) A 2m long dipole made of 6.35 mm diameter aluminium is operated at 500 kHz. Assuming current is uniform and triangular, determine its radiation frequency. (4 Marks)
2 (a) What is an isotropic radiator? (4 Marks)
(b) What are HP and BWFN? Show that HP is roughly one half of the corresponding BWFN value for long, uniformly excited linear arrays. (6 Marks)
(c) What is a beam forming network? (4 Marks)
(d) An interferometer is constructed from five collinear half-wave dipoles spaced two wavelengths apart. Sketch the polar plot of the complete array pattern. (6 Marks)
3 (a) Construct the linear, polar plot of the pattern factor for a broadside cosine-tapered line source that is three wavelengths long. (8 Marks)
(b) What are straight wire diploes? (4 Marks)
(c) The simplistic beauty of the Yagi is revealed by lengthening the parasite. Explain. (4 Marks)
(d) Design an optimum directivity vee dipole to have a directivity of 6 dB. (4 Marks)
4 (a) Differentiate between normal mode helix antenna and axial mode helix antenna. (6 Marks)
(b) A sinuous antenna is more complicated than the spiral antenna. Explain why? (4 Marks)
(c) Derive optimum pyramidal horn design equation. (6 Marks)
(d) Show that the directivity-beamwidth product for a uniform phase rectangular aperture with cosine amplitude taper in the H-plane and uniform amplitude in the E-plane is 35230 square degrees. (4 Marks)
5 (a) Explain Woodward-Lawson sampling method. (6 Marks)
(b) Explain Dolph-Chebyshev linear array method of antenna synthesis. (6 Marks)
(c) What is radar equation? Define radar cross section. (4 Marks)
(d) Calculate the antenna factor of a matched antenna operating at 30 MHz with a gain of 3 dB and terminated with a 50 Ω resistor. (4 Marks)
6 (a) Derive Pocklington’s integral equation. (8 Marks)
(b) Explain why delta gap model is known as slice generator. (4 Marks)
(c) What are compressed matrices? (4 Marks)
(d) Sketch a wire grid model for a square plate 1λ1λ. If pulse expansion functions are to be used, how many unknowns will your model have? (4 Marks)
7 (a) What is FD-TD approach? Explain with the help of a flowchart. (8 Marks)
(b) Write a detailed note on Vivaldi slotline array. (8 Marks)
(c) Can numerical dispersion occur in a non-dispersive medium? (4 Marks)
8 (a) Explain the postulates of Keller’s theory. (4 Marks)
(b) Explain the PTD formulation for surfaces with perfectly cutting edges. (6 Marks)
(c) Using physical optics, show that the radar cross section of a flat rectangular plate at normal incidence is σ = 4π (A22) where A is the area of the plate. (6 Marks)
(d) Write a note on the importance of GTD method in antenna and scattering problems. (4 Marks)

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