Mumbai University Previous year question papers
VI Sem Electronics Examination June 2009
Antena and Wave Propogation
NB:-Question No.1 is compulsory.
Attempt any four of remaining six questions.
Assume suitable data if needed.
Support your answer with neat sketches.
1 Write briefly about :-
(a) Radiation resistance
(c) Antenna resolution
(d) Rhombic antenna
(e) Critical frequency
(f) Antenna arrays
2. (a) Derive an expression for near field and for field equation of short electric dipole. 10
(b) An antenna has a field pattern given by E(e)=cose cos2e for 0 < e < 90° 10
1) Half power beamwidth
2) First Null beamwidth.
3. (a) Describe space wave propogation and derive relation for maximum distance between transmitting and recieving antenna. Earth is assumed to be flat.
(b) Explain ducting effect. Under what conditions this effect takes place. 8
4.(a) What is array factor? 5
(b) Explain pattern multiplication. Draw the radiation for an array of two parallel, half wavelength space short dipoles using pattern multiplication.
(c) Explain briefly about parasitic array. 5
5.(a) Explain working of leg periodic antenna. Write down practical application of the antennas. .-
(b) What do you mean by fading? How it can be minimized? 5
(c) Discuss behaviours of loop antenna and sketch its field pattern. 5
6. (a) Describe parabolic reflector and its use of microwave frequencies. Discuss Cassegrain method of feeding parabolic reflectors.
(b) Explain structure of microstip antenna. Discuss its feed mechanisms and application.
7. Write technical notes on :-
(a) Sleeve dupole
(b) Biconical antenna
(c) Friss Transmission formula
(d) Formation of layer in Ionosphere