GATE EC||ELCTROMAGNETIC FIELD THEORY||ANTENNA|| PYQS(2000-2025)

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Question 1

For a Hertz dipole antenna, the Half Power Beam Width (HPBW) in the E-plane is

(GATE 2008|| EC || MCQ ||1 MARK)

  • 360°

  • 180°

  • 90°

  • 45°

Question 2

An antenna with a directive gain of 6 dB is radiating a total power of 16 kW. The amplitude of the electric field in free space at a distance of 8 km from the antenna in the direction of 6 dB gain (rounded off to three decimal places) is ____ V/m.

(GATE 2021|| EC || NAT||2 MARK)

  • 0.244

Question 3

Radiation resistance of a small dipole current element of length l at a frequency of 3 GHz is 3 ohms. If the length is changed by 1%, then the percentage change in the radiation resistance, rounded off two decimal places, is _________ %.

(GATE 2019|| EC || MCQ||1MARK)

  • 2

Question 4

Consider a wireless communication link between a transmitter and a receiver located in free space, with finite and strictly positive capacity. If the effective areas of the transmitter and the receiver antennas, and the distance between them are all doubled, and everything else remains unchanged, the maximum capacity of the wireless link.

(GATE 2017|| EC || MCQ||1MARK)

  • increased by a factor of 2

  • decreased by a factor of 2

  • remains unchanged

  • decreases by a factor 1.41

Question 5

A radar operating at 5 GHz uses a common antenna for transmission and reception. The antenna has a gain of 150 and is aligned for maximum directional radiation and reception to a target 1 km away having radar cross- section of 3 m 2 . If it transmits 100 kW, then the received power (in μW) is

(GATE 2016|| EC || NAT||2 MARK)


  • 0.0122

Question 6

Annotation-2025-09-19-233815

(GATE 2016|| EC || MCQ||2 MARK)

  • 1.5C 0 , 10 dB

  • 1.256C 0 , 10 dB

  • 1.256C 0 , 12 dB

  • 1.5C 0 , 12 dB

Question 7

Two lossless X-band horn antennas are separated by a distance of 200 λ. 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 ________.

(GATE 2016|| EC || NAT||2 MARK)

  • 2.99

Question 8

The directivity of an antenna array can be increased by adding more antenna elements, as a larger number of elements

(GATE 2015|| EC || MCQ||1 MARK)

  • improves the radiation efficiency

  • increases the effective area of the antenna

  • results in a better impedance matching

  • allows more power to be transmitted by the antenna

Question 9

For an antenna radiating in free space, the electric field at a distance of 1 km is found to be 12 mV/m. Given that intrinsic impedance of the free space is 120 π Ω, the magnitude of average power density due to this antenna at a distance of 2 km from the antenna (in nW/m 2 ) is ______.

(GATE 2014|| EC || NAT ||1 MARK)

  • 47.7

Question 10

Match Column A with Column B.

Column-A Column-B

1. Point electromagnetic P. Highly directional

source

2. Dish antenna Q. End fire

3. Yagi-Uda antenna R. Isotropic


(GATE 2014|| EC || MCQ ||1 MARK)

  • 1 2 3

  • 2 3 1

  • 2 1 3

  • 3 2 1

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