1
GATE ECE 2020
MCQ (Single Correct Answer)
+1
-0.33

The impedances $Z=j X$, for all $X$ in the range ( $-\infty, \infty$ ), map to the Smith chart as

A

a circle of radius 1 with centre at $(0,0)$.

xx
B

a line passing through the centre of the chart.

C

a circle of radius 0.5 with centre at $(0.5,0)$.

D

a point at the centre of the chart.

2
GATE ECE 2020
Numerical
+2
-0

The magnetic field of a uniform plane wave in vacuum is given by

$$ \vec{H}(x, y, z, t)=\left(\hat{a}_x+2 \hat{a}_y+b \hat{a}_z\right) \cos (\omega t+3 x-y-z) . $$

The value of $b$ is $\_\_\_\_$ .

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3
GATE ECE 2020
MCQ (Single Correct Answer)
+2
-0.67

For an infinitesimally small dipole in free space, the electric field $E_\theta$ in the far field is proportional to $\frac{e^{-j k r}}{r} \sin \theta$, where $k=\frac{2 \pi}{\lambda}$. A vertical infinitesimally small electric dipole ( $\delta l \ll \lambda$ ) is placed at a distance $h(h>0)$ above an infinite ideal conducting plane, as shown in the figure. The minimum value of $h$, for which one of the maxima in the far field radiation pattern occurs at $\theta=60^{\circ}$, is

GATE ECE 2020 Electromagnetics - Antennas Question 2 English
A

$0.75 \lambda$

B

$0.25 \lambda$

C

$0.5 \lambda$

D

$\lambda$

4
GATE ECE 2020
MCQ (Single Correct Answer)
+1
-0.33

Consider the recombination process via bulk traps in a forward biased $p n$ homojunction diode. The maximum recombination rate is $U_{\max }$. If the electron and the hole capture cross sections are equal, which one of the following is FALSE?

A

$U_{\max }$ occurs at the edges of the depletion region in the device.

B

$U_{\max }$ depends exponentially on the applied bias.

C

With all other parameters unchanged, $U_{\max }$ increases if the thermal velocity of carrier increases.

D

With all other parameters unchanged, $U_{\max }$ decreases if the intrinsic carrier density is reduced.