VTU Previous Exam Papers BE EC 6th Semester
Transmission Lines and Antennas June-July 2009
PART – A
1 a. Obtain the required condition for a transmission line to have neither frequency nor delay distortion.
b. A generator of 1-0 volt, 1kHz supplies power to 100 km open wire line terminated in Zo and having following parameters. R = 10.4 ohms / km ; L = 0.00367 henry per km ; G-0.8xl0′6mhosperkm C = 0.00835 |iF per km.
Find, characteristic impedance, Propagation constant, wavelength of the
propagating wave, sending end current.
2 a. Comment with Justification on the correctness of the statement – “Standard reference antenna for the directive gain is the istropic antenna”.
b. Comment with justification on the correctness of the statement – “A quarter wave section of the line may be thought of as a transformer to match a load and to a source impedance”.
c. A line of characteristic impedance 200 ohms is terminated in a load of 80 – J100 ohms. Determine the location and length of the single stub matching section. The characteristic impedance of stub is same as that of line.
3 a. Derive Frii’s Transmission formula.
b. Define Stray factor, Effective length, Effective Aperture. State the expressions, notations used.
a. T and n equivalent to lines.
b. Telephone cables.
c. Antenna Field Zones.
PART – B
5 a. Find the directivity for the source with unidirectional cosine squared power pattern.
b. Illustrate the principles of pattern multiplication.
c. Derive the expression for an N-element uniform array. Further show that the peaks of this array factor are given by the solution of the equation. N.tan(\j//2) = tan (N y/2).
6 a. Derive the expressions for Electric and magnetic fields of a short dipole.
b. Give the properties of Horn Antenna.
c. Illustrate – Babinet’s Principle.
7 a. Derive instantaneous electric field at a large distance V from a loop antenna of radius ca.
b. Give the properties of Parabolic reflector. How a parabolic reflector servers the purpose of transmitting and receiving antenna? Discuss in detail its short comings.
8 Write short notes on :
a. Broad side array with non uniform amplitude distribution.
b. Lens antenna.
c. Plasma antenna.