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Term End Examination - November 2012

Course : EEE533 - dvanced Radiation Systems Slot: A1+TA1

Class NBR : 3592

Time : Three Hours Max.Marks:100

General Instruction:

1. Assume suitable value for any missing data

2. Refer the table

Answer ALL the Questions

1. a) In free space a wave propagating radially away from the antenna at the origin has

sinR

IH ss = a , where the driving current phasor

j

s eII 0= . Determine the

i.Power radiated

ii.Beam width

iii.

Pattern solid angle

iv. Directivity

v.Power radiated through beam width

[15]

b) Sketch the current distribution along each arm of the dipole whose total length is

5/8 and 3/2.

[5]

2. a) Design a E plane horn such that the maximum phase difference between the two

points at the aperture, one at the center and the other at the edge is 120. Assuming

the maximum length along its wall from the aperture to the apex is E = 10 find,

i. the maximum total flare angle of the horn

ii.the largest dimension of horn at the aperture

iii. directivity of horn

iv. Gain of horn when the reflection coefficient within the waveguide feeding the

horn is 0.2. Assume only mismatch losses. The waveguide feeding the horn has

dimensions of 0.5and 0.25.

[20]

OR

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2. b) A rectangular aperture of dimension aand b is mounted on an infinite ground plane.

The far field radiated by the aperture in the E plane is expressed as

=

sin2

sin

2

sin

2

0

kb

kb

rejabkEE

jkr

Determine

i. the first null beamwidth

ii.Half power beamwidth

iii. Directivity

iv. Side lobe level

v. Compute the FNBW, HPBW and directivity if the rectangular aperture with

a=3and b=2is mounted on an infinite ground plane.

[20]

3. a) A 10-meter diameter paraboloidal reflector is used as a TV satellite antenna. The

focus-to-diameter ratio of the reflector is 0.536 and the pattern of the feed in the

forward region can be approximated by cos 2 (). Over the area of the reflector the

incident power density from the satellite can be approximated by a uniform plane

wave with a power density of 10W/m2at a center frequency of 9 GHz.

i.Assuming no losses of any kind and aperture efficiency of 71%, what is the

maximum power that can be delivered to a TV receiver connected to the

reflector through a lossless transmission line?

ii.Determine the position of focal point with reference to the reflector and the

angular aperture.

[6]

b) State Babinets principle. Determine the impedance of dipole and its complementary

structure.

[4]

4. A rectangular microstrip antenna with length L=5 cm and width W=3 cm is

fabricated on a substrate with r=2.5 and thickness h=7.94 cm. The patch is

operated in TM10mode.

i. Calculate and compare the resonance frequencies with open end effect and

without open end effect.

[20]

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ii. If the patch is fed at the radiating edge, what is the input impedance at resonance

frequency?

iii.If the patch is fed at one of the non radiating edges select the location that will

yield an input impedance of 50.

5. Design a linear array of isotropic elements placed along the z axis such that the nulls

of the array factor occur at =0,60,90,120,180. Assume that the elements are

spaced a distance d=/2 apart and that =0.

a) Sketch and label the visible region on the unit circle.

b) Find the required number of elements.

c) Determine their excitation coefficients.

d) Determine the length of the array.

[15]

6. Sketch at least five types of antenna which you see in your community, surrounding,

mobile etc., Explain the type of antenna, its operating frequency, how it is used and

performance parameter values.

[15]