1
GATE ECE 1996
Subjective
+5
-0
Two isotropic antennas A and B from an array as shown in Fig. The currents fed to the two antennas are $${{\rm I}_0}\,\angle 0$$ and $${{\rm I}_0}\,\angle \alpha$$ respectively. What should be the value of $$\alpha$$ so that the radiation pattern has a null at $$\theta = {30^ \circ }$$. Find the direction of the maximum radiation for that value of $$\alpha$$ and draw the radiation pattern. ($$\lambda \,\,$$ is the wavelength of operation) 2
GATE ECE 1995
Subjective
+5
-0
Two dipoles are so fed and oriented in free space that they produce the following electromagnetic waves: $${E_x} = 10\,{e^{j\left( {\omega t - z\pi /3} \right)}}\,\,volts/metre$$$$${E_y} = j\,\,10\,{e^{j\left( {\omega t - z\pi /3} \right)}}\,\,volts/metre$$$

(a) Write down the expression for the corresponding magnetic field strength vector.
(b) Calculate the frequency of the wave.
(C) Give the complete description of the polarization of the wave.

3
GATE ECE 1994
Subjective
+5
-0
Two spacecrafts are separated by 3000 km. Each has a paraboloidal reflector antenna of 0.85 m diameter operating at a frequency of 2 GHz with an aperture efficiency of 64%. If the space crafts A's receiver requires 1pW for a 20 dB signal-to-noise ratio, what transmitter power is required on the spacecraft B to achieve this signal-to-noise ratio?
4
GATE ECE 1993
Subjective
+5
-0
Consider an array of two non-directional radiators with spacing $$d\,\, = \,\,0.5\,\,\lambda$$. Determine the directions of maximum radiation when the radiators are excited as shown in Fig.. Calculate the phase shift required for turning the direction of the maximum radiation by $${90^ \circ }$$ keeping the separation d unchanged. GATE ECE Subjects
Network Theory
Control Systems
Electronic Devices and VLSI
Analog Circuits
Digital Circuits
Microprocessors
Signals and Systems
Communications
Electromagnetics
General Aptitude
Engineering Mathematics
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