Sixth Semester B.E. Degree Examination, June / July 2014 Antennas and Propagation Note: Answer FIVEfull questions, selecting at least TWO questions from each part. PART-A a. Defme the fo Howingterms with respect to antenna: i) Gain ii) Isotropic radiator iii) Beam area iv) Radiation resistance. (08 Marks) b. Prove thatmaximum effective aperture for a ~ antenna is 0.13A 2 . (06 Marks) 2 •• ":) c. The effective apertures of transmitting and receiving ante{lnasin acommunication system are 8A.? and l2A? respej)tively, with aseparation ofl',1.~ l<.~ between them. The e.ffi. wave is travelling with a frequency of 6 MHzand the total UP power is 25 KW. Find the power received by thereceiving antenna. (06 Marks) a. Derive an expression for power radiated from an isotropic point source with "sine squared power pattern". Also find directivity "0" and draw power pattern. (06 Marks) b. Find the power radiated and directivity for the unidirectional point sources, having the following point sources power patterns: i) U =U mcos 2 esin 3 ~, 0~e ~ 7t, 0 ~ ~ ~ 7t ii) U=Umsin2esin3~, O~e~7t, 0~~~7t (06 Marks) c. Eight point sources are spaced A apart. They haveaphase difference of 7tbetween adjacent 6 3 elements. Obtain the field pattern. Also find BWFN and HPBW. (08 Marks) a. Show that the radiation resistance of a half wave (~) dipole antennais 73 Q. (06 Marks) b. Write an explanatory note on folded dipole antenna, giving neat figures. (06Marks) c. A magnetic field strength of 20 !lA/m is required to be produced at apoint2\.5km from the antenna in the broadside plane, in freespace. How much power istransmitted by, i) a hertzian dipole, with l=!:-'. 15 ii) a halfwave dipole and iii) amonopole antenna. a. Discuss the features of a loop antenna. Derive an expression for the far field components of a loop antenna. (10 Marks) b. Explain Babinet's principle with illustrations. Discuss features of complementary antennas, with neat figures. (10 Marks) www.bookspar.com | VTU NOTES | QUESTION PAPERS | NEWS | VTU RESULTS | FORUM | VTU BOOKSPAR APP www.bookspar.com | VTU NOTES | QUESTION PAPERS | NEWS | VTU RESULTS | FORUM | VTU BOOKSPAR APP