# Mumbai University Previous year question papers

## VI Sem Electronics Examination June 2006

## Antena and Wave Propogation

N.S. (1) Question NO.1 is compulsory.

(2) Attempt * any *four of remaining six. (solve in all five)

(3) Assume suitablecdata, if needed.

(4) Support your answers with suitable sketches.

1. Write briefly about :-

(a) Radiation Resistance

(b) Directivity

(c) Beam ‘eff[ciency

(d) Critical frequency

(e) Antenna arrays

(f) Rhombic <Antenna

(g) Isotropic antenna.

2. (a) Derive * an *expression for the near field

*for field equation for a sr.ort electric cjipO!8.*

*and*(b) * An *antenna has a f,ieldpatfern given by E(8) = cosS.Cos28 for 0 ~ 8:<:;

*rind (i) HPBW al”‘d (ii) FNBW.*

*90°.*

3. (a) Calculate Radiation * of V16 *wire dipole in

*space. Also calculate antenna efficiency if loss r,:.!sistance is 1.1 ohm.*

*free*(b)Discuss the factors influencing the antenna efficiency. Differentiate folded dipole and half wave dipole antennae.

4. (a) Deriv-3 the relation for FRIIS formula. What is the maximum power feceived al a distance of 05 km 0″”;( a * free *space 1 GHz circuit consisting of a transmitting antenna with a 25 db gain and a receiving atenna with a gian of 20 db ? The transmitting antenna is fed 150 W of power.

(b) Explain pa:-abolic reflector antenna. How is it illuminated?

5.(a) Describe space wave propagation and derive the relation for the maximum distance between transmitting and receiving antenna. Earth is assumed to be flat.

(b) With the help of a neat sketch, explain ducting effect. In which conditions. this effe.:t takes place?

6. (a) What is array factor ?

(b) Explain pattern multiplication. Draw the radiation for an array of two parallel. half wave length spaced short dipoles using pattern multiplication.

(c) Explain briefly about parasitic array.

7. ~trite notes* on *(any

**four) :-**

(a) Sky wave propagation

(b) Effective Aperture

(c) Biconical antenna

(d) MiG’rostripantenna

(e) Monopole antenna

(f) Log periodic antenna.