# Antennas · Electromagnetics · GATE ECE

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## Marks 1

GATE ECE 2015 Set 3
The directivity of an antenna array can be increased by adding more antenna elements, as a larger number of elements
GATE ECE 2014 Set 4
For an antenna radiating in free space, the electric field at a distance of 1 km is found to be 12 m V/m. Given that intrinsic impedance of the free s...
GATE ECE 2014 Set 4
Match column A with column B. Column 1. Point electromagnetic source 2. Dish antenna 3. Yagi-Uda antenna Column P. Highly directional Q...
GATE ECE 2012
The radiation pattern of an antenna in spherical co-ordinates is given by $$F\,(\theta )\, = {\cos ^4}\,\theta \,\,\,;\,\,0\,\, \le \,\,\theta \,\, \... GATE ECE 2008 For a Hertz dipole antenna, the half power beam width (HPBW) in the E-plane is GATE ECE 2006 A transmission line is feeding 1 Watt of power to a horn antenna having gain of 10 dB. The antenna is matched to the transmission line. The total powe... GATE ECE 2005 Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of$${10^{14}}$$Hz in glass. Assume velocity of light is$$...
GATE ECE 2004
Consider a lossless antenna with a directive gain of + 6 dB. If 1 m W of power is fed to it the total power radiated by the antenna will be
GATE ECE 2002
The line-of-sight communication requires the transmit and receive antennas to face each other. If the transmit antenna is vertically polarized for bes...
GATE ECE 2000
If the diameter of a $$\lambda /2$$ dipole antenna is increased from $$\lambda /100$$ to $$\lambda /50$$ then is
GATE ECE 1998
An antenna in free space receives 2$$\mu$$ W of power when the incident electric field is 20 m V/m rms. The effective aperture of the antenna is
GATE ECE 1998
The radiation resistance of a circular loop of one turn is 0.01 $$\Omega$$. The radiation resistance of five turns of such a loop will be
GATE ECE 1998
The far field of an antenna varies with distance r as
GATE ECE 1998
The vector $$\mathop H\limits^ \to$$ in the far field of an antenna satisfiels
GATE ECE 1995
An antenna when radiating, has a highly directional radiation pattern. When the antenna is receiving its radiation pattern
GATE ECE 1994
For a dipole antenna

## Marks 2

GATE ECE 2017 Set 1
A half wavelength dipole is kept in the x-y plane and oriented along $${45^ \circ }$$ from the x-axis. Determine the direction of null in the radiatio...
GATE ECE 2016 Set 1
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-...
GATE ECE 2016 Set 1
Two lossless X-band horn antennas are separated by a distance of $$200\lambda$$. The amplitude reflection coefficients at the terminals of the transm...
GATE ECE 2016 Set 1
The far-zone power density radiated by a helical antenna is approximated as: $$\overrightarrow W {\,_{rad}} = \overrightarrow W \,average\, \approx \... GATE ECE 2015 Set 2 Two half-wave dipole antennas placed as shown in the figure are excited with sinusoidally varying currents of frequency 3 MHz and phase shift of$$\pi...
GATE ECE 2008
At 20 GHz, the gain of a parabolic dish antenna of 1 meter diameter and 70% efficiency is
GATE ECE 2007
A $$\lambda /2$$ dipole is kept horizontally at a height of $${\lambda _0}/2$$ above a perfectly conducting infinite ground plane. The radiation patte...
GATE ECE 2006
A mast antenna consisting of a 50 meter long vertical conductor operates over a perfectly conducting ground plane. It is base-fed at frequency of 600...
GATE ECE 2005
Two identical and parallel dipole antennas are kept apart by a distance $$\lambda /4$$ of in the H-plane. They are fed with equal currents but the rig...
GATE ECE 2003
Two identical antennas are placed in the $$\theta = \pi /2$$ plane as shown in figure. The elements have equal amplitude excitation with 180° polarit...
GATE ECE 2002
A person with a receiver is 5 Km away from the transmitter. What is the distance that this person must move further to detect a 3-dB decrease in signa...
GATE ECE 2001
In a uniform linear array, four isotropic radiating elements are spaced $$\lambda /4$$ apart. The progressive phase shift between the elements require...
GATE ECE 2001
A medium wave radio transmitter operating at a wavelength of 492 m has a tower antenna of height 124m. What is the radiation resistance of the antenna...
GATE ECE 2000
For an 8 feet (2.4 m) parabolic disk antenna operating at 4 GHz, the minimum distance required for far field measurement is closest to
GATE ECE 2000
The half-power beam widths (HPBW) of an antenna in the two orthogonal planes are $${100^ \circ }$$ and $${60^ \circ }$$ respectively. The directivity...
GATE ECE 1999
A transmitting antenna radiates 251 W isotropically. A receiving antenna, located 100m away from the transmitting antenna, has an effective aperture o...
GATE ECE 1997
A parabolic dish antenna has a conical beam 20 wide. The directivity of the antenna is approximately
GATE ECE 1996
A transverse electromagnetic wave with circular polarization is received by a dipole antenna. Due to polarization mismatch, the power transfer efficie...
GATE ECE 1996
A 1 km long microwave link uses two antennas each having 30dB gain. If the power transmitted by one antenna is 1 W at 3 GHz, the power received by the...
GATE ECE 1992
Two dissimilar antennas having their maximum directivities equal
GATE ECE 1992
The beam width-between-first-null of a uniform linear array of N equally-spaced (element spacing = d) equally-excited antennas is determined by
GATE ECE 1991
In a board side array of 20 isotropic radiators, equally spaced at a distance of $$\lambda /2$$, the veam width between first nulls is
GATE ECE 1990
Two isotropic antennas are separated by a distance of two wavelengths. If both the antennas are fed with currents of equal phase and magnitude, the nu...
GATE ECE 1989
In the case of ground wave propagation, at far-off distances from the transmitting tower antenna, the Poynting vector is
GATE ECE 1988
The electric field E and the magnetic field H of a short dipole antenna satisfy the condition

## Marks 4

GATE ECE 1987
A thin dipole antenna is $$\left( {\lambda /15} \right)$$ long, where $$\lambda$$ is the voperating wavelength. If the dipole has a loss resistance o...

## Marks 5

GATE ECE 2002
Consider a linear array of two half - wave dipoles A and B as shown in Fig. The dipoles are $${\lambda \over 4}$$ apart and are excited in such a way...
GATE ECE 1999
The average power of an omni-directional antenna varies as the magnitude of cos($$\theta$$) where $$\theta$$ is the azimuthal angle. Calculate the m...
GATE ECE 1997
A dipole antenna has a sin$$\theta$$ radiation pattern where the angle $$\theta$$ is measured from the axis of the dipole. The dipole is vertically ...
GATE ECE 1996
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 $${{\rm I}_0}\,\a... GATE ECE 1995 Two dipoles are so fed and oriented in free space that they produce the following electromagnetic waves:$$\${E_x} = 10\,{e^{j\left( {\omega t - z\pi ...
GATE ECE 1994
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 apert...
GATE ECE 1993
Consider an array of two non-directional radiators with spacing $$d\,\, = \,\,0.5\,\,\lambda$$. Determine the directions of maximum radiation when th...

## Marks 8

GATE ECE 1992
Elements of a linear array of three equally spaced (element spacing $$0.5\lambda$$ ) vertical mast radiators are excited as given in Fig. For the hor...

## Marks 10

GATE ECE 1991
In the radiation pattern of a 3-element array of isotropic radiators equally spaced at distances of $${\lambda /4}$$ it is required to place a null a...
GATE ECE 1989
Two vertically oriented half wave dipoles are spaced 1.5 wavelengths apart to from an array. Calculate the half power beam widths of the major lobes o...
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