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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
BE SEMESTER-VI EXAMINATION SUMMER 2017
Subject Code: 161003 Date: 27/04/2017
Subject Name: Antenna Wave Propogation
Time: 10:30 AM to 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

What do you mean by an antenna? Derive the FRIIS formula relating to power received and radiated power.
07

Define following terms:
HPBW
Antenna radiation efficiency
Radiation density
Beam solid angle
Directivity
Far field
Effective length of an antenna
07
Q.2

Solve the followings:
Find the radiation resistance of a Hertzian dipole of length λ/40 ans λ/60.
An antenna whose radiation resistance is 300 Ω operates at a frequency of 1 GHz and with a current of 3 A. Find the radiated power.
Find the effective area of a Hertizian dipole operating at 100 MHz.
02
02
03

Derive necessary equations for E and H field of Half wave dipole antenna.
07
OR

Explain Broadside array and End fire array, considering linear array of four isotropic sources.
07
Q.3

What are the advantages of Dolph-Tchebysheff amplitude distribution of feeding current of linear array? Compare uniform, binomial and edge amplitude distribution of feeding current for linear array with optimum distribution.
07

Find the basic and actual transmission losses between two antennas separated by 30 m operating at 10 MHz when the gain of each antenna is 1.65 dB.
07
OR
Q.3

Define binomial arrays. Also write a brief note on Principle of Pattern Multiplication.
07

Derive the far field components and the radiation resistance of a small circular loop with radius and with a uniform phase current.
07
Q.4

What is the importance of parabolic structure as a reflector in antenna? Explain the cassegrain feed mechanism of parabolic reflector antenna.
07

State Babinet's principle and illustrate its application to slot antennas and complementary antennas.
07
OR
Q.4

What is log periodic antenna? Explain with neat sketch log periodic dipole array.
07

Draw and explain the Helical Geometry with neat diagram. Also explain transmission and radiation mode.
07
Q.5

Write a short note on sky wave and space wave propagations.
07

Explain Gain measurement and impedance measurement of antenna along with the experimental set-up.
07
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OR
Q.5

Define the following terms for radio wave propagation.
Virtual height
MUF
Critical frequency
Skip distance
Fading
Multi hope propagation
OWF
07

Write short notes on followings:
Lens antenna
Embedded antenna.
07