ECE 305 5TH Sem May 2005
ANTENNA & WAVE PRPAGATION
Note: Section A is compulsory. Attempt any Four questions from Section B and two from Section C.
Section A Marks 2 each
1.
(a) What do you mean by antenna tuning?
(b) How do you distinguish between “near zone” and “far zone” of an antenna?
(c) How does an antenna radiate electromagnetic energy?
(d) What do you mean by elliptical polarization?
(e) How do you define an impedance of an antenna?
(f) What is folded dipole?
(g) What do you mean by parasitic elements?
(h) What is maximum usable frequency?
(i) What is optimum traffic frequency?
(j) What is the effect of fading on signal strength?
Section B Marks 5 each
2. Find out the phase difference between the direct and reflected rays in space wave propagation.
3. Write notes on any one of the following:
(a) Duct propagation
(b) Whip Antennas.
4. What is paraboloid antenna? Derive an expression for its gain.
5. Compute the radiation resistance, the power radiated and efficiency of an antenna having total resistance of 50 ohms, an effective height of 60.96 meters and current of 50 A (r.m.s.) at 0.480 MHz.
6. An antenna has radiation resistance and loss resistance of 72 O and 8 O respectively. Calculate its directivity given that its power gain is 17.
Section C Marks 10 each
7. Show that radiation field electric intensity of quarterwave monopole is:
Eq=60Im/r {[cos(p/2 cos q)]/sin q} V/m
8. Derive an expression for radiation pattern of broad side, uniform, linear array of 4 equally spaced (l/2) isotropic antenna. Calculate the width of its major lobe between first null and draw its pattern.
9. Radio waves projected towards the atmosphere do not return if the frequency is raised above a particular frequency which also changes with the angle of projection. Explain.
ANTENNA & WAVE PRPAGATION
Note: Section A is compulsory. Attempt any Four questions from Section B and two from Section C.
Section A Marks 2 each
1.
(a) What do you mean by antenna tuning?
(b) How do you distinguish between “near zone” and “far zone” of an antenna?
(c) How does an antenna radiate electromagnetic energy?
(d) What do you mean by elliptical polarization?
(e) How do you define an impedance of an antenna?
(f) What is folded dipole?
(g) What do you mean by parasitic elements?
(h) What is maximum usable frequency?
(i) What is optimum traffic frequency?
(j) What is the effect of fading on signal strength?
Section B Marks 5 each
2. Find out the phase difference between the direct and reflected rays in space wave propagation.
3. Write notes on any one of the following:
(a) Duct propagation
(b) Whip Antennas.
4. What is paraboloid antenna? Derive an expression for its gain.
5. Compute the radiation resistance, the power radiated and efficiency of an antenna having total resistance of 50 ohms, an effective height of 60.96 meters and current of 50 A (r.m.s.) at 0.480 MHz.
6. An antenna has radiation resistance and loss resistance of 72 O and 8 O respectively. Calculate its directivity given that its power gain is 17.
Section C Marks 10 each
7. Show that radiation field electric intensity of quarterwave monopole is:
Eq=60Im/r {[cos(p/2 cos q)]/sin q} V/m
8. Derive an expression for radiation pattern of broad side, uniform, linear array of 4 equally spaced (l/2) isotropic antenna. Calculate the width of its major lobe between first null and draw its pattern.
9. Radio waves projected towards the atmosphere do not return if the frequency is raised above a particular frequency which also changes with the angle of projection. Explain.