Cochin University of Science and Techology (CUST) 2008 B.Tech Electronics and Communications Engineering RADIO COMMUNICATION - Question Paper

RADIO COMMUNICATION (NOVEMBER 2008)


1a. The derived E field for a Hertzian/Short dipole have 2 significant components. discuss these fields, their behavior and significance
b. discuss the following:
i) Radiation resistance and efficiency
ii) Effective aperture area
iii) Directivity and gain
2a. Draw a typical dipole antenna and its radiation trend and discuss
i) major lobe and beamwidth
ii) side lobe and its level
iii) polarisation
b. Compare ranging from lambda/2 dipole and lambda/4 monopole and folded dipole in terms of their radiation resistance, directivity, and beamwidth
3a. discuss clearly the reciprocity theorem for antennas
b. discuss and define the 3-element Yagi array, naming the elements, dimensions and their spacing
4a. Using the expression derived for total field for a 2-element array, derive the field expression for an n-element array of isotropic radiators with equal excitation and elements spaced lambda/2
b. Through geometrical interpretation discuss why parablic reflector antennas are almost always preferred at microwave frequencies
5a. Ionosphere supports long distance communication. Explain, indicating the behaviorand limitations of ground wave, space wave and troposphere
b. discuss Line Of Sight (LOS) communication and Horizon effect. The heights of transmitting and receiving antennas are 20m and 15m respectively from ground. Determine the maximum range obtainable in the line of sight mode
6a. discuss the folowing: critical frequency, virtual height, effect of earth's magnetic field, skip distance
b. Exlain with necessary figure and relation Antenna Gain measurement by substitution method
7a. discuss clearly with figures the subsequent : pulse width, pulse repetition frequency, range resolution, range ambiguity
b. A pulse radar has plse width of one microsecond and prf of 1000Hz. Determine range resolution and unambiguous range
8a. define the concept of Matched filter receiver and show that the impulse response of the matched filter is the signal itself reversed in time
b. discuss the "Chirp" radar and its necessity and functioning through waveforms
9a. discuss the functioning of fm-cw radar as an altimeter, bringing out the advantages
b. define the 2 main kinds of transmitter configuration normally used and compare them
10a.Describe Amplitude Comparison Monopulse Tracking radar using four antennas/ feeds. elaborate the criticalities in this approach?
b. define the passive ECm techniques normally used against radar

Earning:   Approval pending.