Uttar Pradesh Technical University (UPTU) 2011-3rd Year B.Tech Electrical and Electronics Engineering Antenna and wave propagation,gbtu,,6th sem. - Question Paper

1.Attempt any 4 parts of the following:
(i) The radial component of the radiated power density of an antenna is provided by P-(A0 sin?)/r2. Where A0 is the peak value of power density. Determine total normalised radiated power.
(ii) describe gain and directivity of an antenna.
(iii) Draw the radiation trend of a dipole of length ?/2.
(iv) A dipole antenna of ?/8 length has an equivalent loss resistance of 1.5 ohm. compute the efficiency of the antenna.
(v) Derive an expression for magnetic field intensity in spherical coordinate system due to current element.
(vi) discuss reciprocity theorem in brief.

2. Attempt any 2 parts of the following:
(i) What do you understand by array of an antenna? Derive an expression for excitation angle for broad side and end fire array.
(ii) 2 isotropic radiator A and B are placed along the x-axis at position (-?/8,0) and (?/8,0) respectively. The elements are fed by current of equal amplitude with the phase of B leading the A by 900. Fin the direction of maxima.
(iii) What do you mean by trend multiplication? discuss in detail.

3. Attempt any 2 parts of the following:
(i) discuss ionosphere in detail. The critical frequency of an ionospheric layer is 10MHz. What is the maximum launching angle from the horizon for which 20 MHz will be reflected by the layer?
(ii) describe the following:
(a)MUF
(b)Virtual height
(c)Skip distance
(d)Radio horizon
(iii) discuss in detail:
(a)Duct propagation
(b)LOS propagation
4. Attempt any 2 parts of the following:
(i)What is folded dipole? How it is applicable in Yagi-Uda antenna?
(ii)What are the salient features of frequency independent antennas? Derive an expression for a in terms of s and t of log periodic dipole array.
(iii)Plot the neat sketches for the radiation trend of subsequent antennas:
(a) Parabolic reflector
(b) Helical antenna(axial mode)
(c) Horn antenna
(d) Log periodic dipole array
(e) Folded dipole.

Earning:   Approval pending.