1
GATE ECE 2016 Set 1
MCQ (Single Correct Answer)
+2
-0.6
An antenna pointing in a certain direction has a noise temperature of $$50K$$. The ambient temperature is $$290K$$. The antenna is connected to a pre-amplifier that has a noise figure of 2 dB and an available gain of 40 dB over an effective bandwidth of $$12$$ $$MHz$$. The effective input noise temperature $${T_e}$$ for the amplifier and the noise power $${P_{ao}}$$ at the output of the preamplifier, respectively, are
A
$${T_e} = 169.36K$$ and $${P_{ao}} = 3.73 \times {10^{ - 10}}\,\,\,W$$
B
$${T_e} = 170.8K$$ and $${P_{ao}} = 4.56 \times {10^{ - 10}}\,\,\,W$$
C
$${T_e} = 182.5K$$ and $${P_{ao}} = 3.85 \times {10^{ - 10}}\,\,\,W$$
D
$${T_e} = 160.62K$$ and $${P_{ao}} = 4.6 \times {10^{ - 10}}\,\,\,W$$
2
GATE ECE 2016 Set 1
Numerical
+2
-0
Two lossless X-band horn antennas are separated by a distance of $$200\lambda $$. The amplitude reflection coefficients at the terminals of the transmitting and receiving antennas are $$0.15$$ and $$0.18$$, respectively. The maximum directivities of the transmitting and receiving antennas (over the isotropic antenna) are $$18$$ $$dB$$ and $$22$$ $$dB$$, respectively. Assuming that the input power in the lossless transmission line connected to the antenna is $$2$$ $$W$$, and that the antennas are perfectly aligned and polarization matched, the power ( in mW) delivered to the load at the receiver is ________ .
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3
GATE ECE 2016 Set 1
MCQ (Single Correct Answer)
+2
-0.6
The far-zone power density radiated by a helical antenna is approximated as: $$$\overrightarrow W {\,_{rad}} = \overrightarrow W \,average\, \approx \,\widehat a{}_rC{}_0\,{1 \over {{r^2}}}{\cos ^4}\theta $$$

The radiated power density is symmetrical with respect to $$\phi $$ and exists only in the upper hemisphere: $$0 \le \theta \le {\pi \over 2};\,\,\,\,0 \le \theta \le 2\pi ;$$

$${C_0}$$ is a constant. The power radiated by the antenna (in watts) and the maximum directivity of the antenna, respectively, are

A
$$1.5{C_0},\,\,10dB$$
B
$$1.256{C_0},\,\,10dB$$
C
$$1.256{C_0},\,\,12dB$$
D
$$1.5{C_0},\,\,12dB$$
4
GATE ECE 2015 Set 2
Numerical
+2
-0
Two half-wave dipole antennas placed as shown in the figure are excited with sinusoidally varying currents of frequency 3 MHz and phase shift of $$\pi /2$$ between them (the element at the origin leads in phase). If the maximum radiated E-field at the point P in the x-y plane occurs at an azimuthal angle $${60^ \circ }$$, the distance d (in meters) between the antennas is ___________ . GATE ECE 2015 Set 2 Electromagnetics - Antennas Question 28 English
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