STUPIDSID
1 (a)
With the help of Maxwell's equation, explain how radiation and reception of EM takes place?
6 M
1 (b)
Explain the following terms as related to antenna system:
i) Directivity ii) HPBW iii) Effective length iv) Beam efficiency.
i) Directivity ii) HPBW iii) Effective length iv) Beam efficiency.
8 M
1 (c)
Show that the directivity for unidirectional operation is 2(n+1) for an intensity variation of U-Umcosnθ.
6 M
2 (a)
Write a neat diagram, obtain an expression for maximum effective aperture of a λ/2 dipole.
7 M
2 (b)
Derive relationship between effective aperture and directivity of an antenna.
8 M
2 (c)
Find the maximum power received at a distance of 0.75 km over free space 110 MHz circuit consisting of a transmitting antenna of 30dB gain and a receiving antenna of 25dB gain. If the power i/p to the transmitting antenna is 120 watts.
5 M
3 (a)
Starting from fundamentals derive the equation for radiation resistance of Hertzian dipole.
8 M
3 (b)
A dipole antenna of length 5cm is operated at a frequency of 100MHz with terminal current, I0-120mA. At time t=1 sec, 0=45° and r=3m, Find: (i) Er; (ii) Eθ and (iii) Hϕ
8 M
3 (c)
Calculate the radiation resistance of a length=λ/5. (Assume triangular current distribution).
4 M
4 (a)
Derive the far field expressions for small loop antenna.
8 M
4 (b)
Derive an expression and draw the field pattern for an array of two isotropic point source with equal amplitude and opposites phase. Take d=λ/2.
8 M
4 (c)
Find half power beam width directivity of a linear broadside array of four isotropic point sources of equal strength widht d=λ/2?
4 M
5 (a)
Write explanatory note on: i) Folded-dipole antenna; ii) Yagi-Uda antenna.
10 M
5 (b)
Find the length, L-H plane aperture and flare angles 0E and θH of a pyramidal horn for which E-plane aperture is 10λ. Horn is fed by a rectangular wavelength with TE10 mode. Assume ?=0.2λ in E-plane and 0.375λ in H-plane. Also find E-plane, H-plane beam widths and directivity.
6 M
5 (c)
A dish antenna operating at a frequency of 1.43 GHz has a diameter of 64mts and is fed by directional antenna. Calculate HPBW, BWFN and gain with respect to λ/2 dipole with even illumination.
4 M
6 (a)
Write short notes on:
i) Parabola reflectors
ii) periodic antenna
i) Parabola reflectors
ii) periodic antenna
12 M
6 (b)
Determine the cut off frequencies and bandpass of a log periodic dipole array with a design factor of 0.7. Ten dipoles are used in the structure, the smallest having a dimension L/2 equal to 0.3m.
8 M
7 (a)
Define a wave tilt of a surface wave propagation. Also prove that wave tilt \[ \alpha = \tan^{-1} \dfrac {E_n}{E_v} = \tan ^{-1} \left [ \dfrac {1}{\sqrt{\epsilon_r}} \cdot \dfrac {1}{[1+x^2]^{1/4}} \right ] \]
10 M
7 (b)
Derive the expression for resultant field strength at a point due to space wave propagation.
5 M
7 (c)
For a VHF communication link, a 35 watt transmitter is operating at 90MHz. Determine the distance up to which LOS would be possible given that height of the transmitting and receiving antenna are 40 m and 25m respectively. Evaluate the held strength at the receiving point.
5 M
8 (a)
Define the following: i) MUF; ii) Critical frequency; iii) Virtual height; iv) Skip distance.
8 M
8 (b)
Calculate the value of the operating frequency of the ionosphere layer specified by refractive index of 0.85 and an electron density 5×105 electron/m3. Calculate the critical frequency and MUF of the system with θ1=30°.
6 M
8 (c)
Calculate the critical frequencies for f1, f2 and f3 and E layers, for which the maximum ionic densities are 2.3×106, 3.5×106 and 1.7×106 elections/cm3 respectively.
6 M
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