GATE ECE
Electromagnetics
Antennas
Previous Years Questions

## Marks 1

The directivity of an antenna array can be increased by adding more antenna elements, as a larger number of elements
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...
Match column A with column B. Column 1. Point electromagnetic source 2. Dish antenna 3. Yagi-Uda antenna Column P. Highly directional Q...
The radiation pattern of an antenna in spherical co-ordinates is given by $$F\,(\theta )\, = {\cos ^4}\,\theta \,\,\,;\,\,0\,\, \le \,\,\theta \,\, \... For a Hertz dipole antenna, the half power beam width (HPBW) in the E-plane is A transmission line is feeding 1 Watt of power to a horn antenna having gain of 10 dB. The antenna is matched to the transmission line. The total powe... Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of$${10^{14}}$$Hz in glass. Assume velocity of light is$$...
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
The line-of-sight communication requires the transmit and receive antennas to face each other. If the transmit antenna is vertically polarized for bes...
If the diameter of a $$\lambda /2$$ dipole antenna is increased from $$\lambda /100$$ to $$\lambda /50$$ then is
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
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
The far field of an antenna varies with distance r as
The vector $$\mathop H\limits^ \to$$ in the far field of an antenna satisfiels
An antenna when radiating, has a highly directional radiation pattern. When the antenna is receiving its radiation pattern
For a dipole antenna

## Marks 2

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...
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-...
Two lossless X-band horn antennas are separated by a distance of $$200\lambda$$. The amplitude reflection coefficients at the terminals of the transm...
The far-zone power density radiated by a helical antenna is approximated as: $$\overrightarrow W {\,_{rad}} = \overrightarrow W \,average\, \approx \... Two half-wave dipole antennas placed as shown in the figure are excited with sinusoidally varying currents of frequency 3 MHz and phase shift of$$\pi...
At 20 GHz, the gain of a parabolic dish antenna of 1 meter diameter and 70% efficiency is
A $$\lambda /2$$ dipole is kept horizontally at a height of $${\lambda _0}/2$$ above a perfectly conducting infinite ground plane. The radiation patte...
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...
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...
Two identical antennas are placed in the $$\theta = \pi /2$$ plane as shown in figure. The elements have equal amplitude excitation with 180° polarit...
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...
In a uniform linear array, four isotropic radiating elements are spaced $$\lambda /4$$ apart. The progressive phase shift between the elements require...
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...
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
The half-power beam widths (HPBW) of an antenna in the two orthogonal planes are $${100^ \circ }$$ and $${60^ \circ }$$ respectively. The directivity...
A transmitting antenna radiates 251 W isotropically. A receiving antenna, located 100m away from the transmitting antenna, has an effective aperture o...
A parabolic dish antenna has a conical beam 20 wide. The directivity of the antenna is approximately
A transverse electromagnetic wave with circular polarization is received by a dipole antenna. Due to polarization mismatch, the power transfer efficie...
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...
Two dissimilar antennas having their maximum directivities equal
The beam width-between-first-null of a uniform linear array of N equally-spaced (element spacing = d) equally-excited antennas is determined by
In a board side array of 20 isotropic radiators, equally spaced at a distance of $$\lambda /2$$, the veam width between first nulls is
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...
In the case of ground wave propagation, at far-off distances from the transmitting tower antenna, the Poynting vector is
The electric field E and the magnetic field H of a short dipole antenna satisfy the condition

## Marks 4

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

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...
The average power of an omni-directional antenna varies as the magnitude of cos($$\theta$$) where $$\theta$$ is the azimuthal angle. Calculate the m...
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 ...
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 $${{\rm I}_0}\,\a... Two dipoles are so fed and oriented in free space that they produce the following electromagnetic waves:$$\${E_x} = 10\,{e^{j\left( {\omega t - z\pi ...
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...
Consider an array of two non-directional radiators with spacing $$d\,\, = \,\,0.5\,\,\lambda$$. Determine the directions of maximum radiation when th...

## Marks 8

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

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...
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...
EXAM MAP
Joint Entrance Examination
JEE MainJEE AdvancedWB JEE
Graduate Aptitude Test in Engineering
GATE CSEGATE ECEGATE EEGATE MEGATE CEGATE PIGATE IN
Medical
NEET