| ANTENNA AND WAVE PROPAGATION |
| PAPER NO. 4 |
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EC-305 ANTENNA AND WAVE PROPAGATION (B.Tech 5th Semester, 1202) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1(a) Can you use the same antenna satisfactory for transmission as well as reception. (b) What is the significance of polarisation in communication ? (c) What are the factors that determine the characteristics of an antenna array ? (d) How do you determine a particular mode for communication in a comm. system ? (e) How does antenna radiate em energy? (f) Justify that the strength of electromagnetic waves is recieved inversly proportional to the distance from the transmitting antenna. (g) Why can we not have communication at low frequencies from ionosphere when low frequency waves are bent to the maximum extent ? (h) Why do we use more no. of directors and only one reflector ? (i) What are the merits and demerits of multihop transmission ? (j) What is troposphere scatter ? What are its applications ? Section-B Marks:5 Each 2. Calculate the value of effective aperture in case of: (a) Hertzian dipole (b) half wave dipole. 3. How do you visualise the concept of radiation ? 4. Find the areal drawing current in case of element dipole of λ/360 length to radiate a power of 61 kW ? 5. how does radiation from a hertzian dipole differ from that of a half wave dipole ? 6. Define directivity and gain of an antanna. Section-C Marks : 10 Each 7. Define terminal impedence, noise temperature of an antenna. Also define array factor, directivity and beam of an antenna. 8. Approximate the fields in the vicinity of an antenna. 9. Write notes on any two of the following: (a) Self and mutual impedence (b) Array of point sources (c) Duct propagation |
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