Antennas and Microwave Engineering MCQs | Page - 3

Explanation: beamwidth and directivity are both measures of the focusing ability of an antenna. an antenna with a narrow main beam will have high directivity, while a pattern with low beam will have low directivity.

Explanation: given the beam width of the antenna in 2 planes, the directivity is given by 32400/θ*∅, where θ,∅ are the beam widths in the two orthogonal planes. substituting in the equation, directivity of the antenna is 18.

Explanation: antenna efficiency is defined as the ratio of radiated power to the input power to the antenna. substituting the given data in the efficiency equation, the efficiency of the antenna is 90%.

Explanation: gain of an antenna is given by the product of radiation efficiency of the antenna and the directivity of the antenna.

Explanation: gain of an antenna is always smaller than the directivity of an antenna. gain is given by the product of directivity and radiation efficiency. radiation efficiency can never be greater than one. so gain is always less than or equal to directivity.

Explanation: given the aperture dimensions of an antenna, the maximum directivity that can be achieved is 4π a/λ2, where a is the aperture area and λ is the operating wavelength. substituting the given values in the above equation, the maximum directivity achieved is 19 db.

Explanation: given the aperture dimensions of an antenna, the directivity that can be achieved is ap4π a/λ2, where a is the aperture area and λ is the operating

Explanation: for a resistor noise power produced is given by ktb, where t is the system temperature and b is the bandwidth. substituting in the above expression, the noise power produced is 4.14×10-15 watts.

Explanation: the plot of frequency v/s background noise temperature shows that with the increase of the signal frequency, the

Explanation: the noise temperature of an antenna is given by the expression radtb + (1-rad) tp. here, tb is the brightness temperature and tp is the physical