# Microwave Engineering Questions and Answers – Antenna Basics

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This set of Microwave Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Antenna Basics”.

1. The basic requirements of transmitting antennas are:
a) High efficiency
b) Low side lobes
c) Large signal to noise ratio
d) Lone of the mentioned

Explanation: The basic requirements of a transmitting antenna are high gain and efficiency while requirements of receiving antennas are low side lobes and large signal to noise to ratio.

2. _________ is a device that converts electrons to photons or vice-versa.
a) Antenna
b) Electron gun
c) Photon amplifier
d) Microwave tube

Explanation: Antenna is a device that converts electrons into photons or vice versa. A transmitting antenna converts electrons into photons while a receiving antenna converts photons into electrons.

3. The basic equation of radiation that is applied to any antenna irrespective of the type of the antenna is:
a) iL= Qv
b) iQ = Lv
c) i/L=Q/v
d) None of the mentioned

Explanation: Basic equation of radiation is given by iL=Qv. i is the time change in current, l is the length of the current element, q is the charge v is the acceleration of the charge.
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4. When the separation between two lines that carry the TEM wave approaches λ the wave tends to be radiated.
a) True
b) False

Explanation: When the separation between two lines that chary the TEM wave approaches λ the wave tends to be radiated so that the opened – out line act as an antenna which lunches a free space wave.

5. The number of patterns radiation pattern required to specify the characteristic are :
a) Three
b) Four
c) Two
d) Five

Explanation: The three patterns required are, θ component of the electric field as the function of the angles as θ and φ, the φ component of the electric field as the function of the angles θ and φ, the phase of these fields as a functions of the angle φ and θ .

6. The beam width of the antenna pattern measured at half power points is called:
a) Half power beam width
b) Full null beam width
c) Beam width
d) None of the mentioned

Explanation: The beam width of an antenna measure at half of the maximum power received by an antenna or the 3 dB beam width of the antenna is termed as half null beam width.

7. An antenna has a field pattern of E (θ) = cos2 θ, θ varies between 0 and 900. Half power beam width of the antenna is:
a) 330
b) 660
c) 12000
d) None of the mentioned

Explanation: Half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. Solving the given problem in the same flow, half power beam width of the antenna is 660.

8. An antenna has a field pattern E (θ) =cos θ. cos 2θ. The first null beam width of the antenna is:
a) 450
b) 900
c) 1800
d) 1200

Explanation: Half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. Twice the half power beam width gives the first null beam width. With the same steps applied, the half power beam width of the antenna is 450. First null beam width is 900.

9. The solid area through which all the power radiated by the antenna is:
a) Beam area
b) Effective area
c) Aperture area
d) Beam efficiency

Explanation: The beam area is the solid angle through which all of the power radiated by the antenna would stream if P (θ, φ) maintained its maximum value over beam area and zero elsewhere. This value is approximately equal to the angles subtended by the half power points of the main lobe in the two principal planes.

10. Power radiated from an antenna per unit solid angle is called radiation intensity.
a) True
b) False

Explanation: Power radiated from an antenna per unit solid angle is called radiation intensity. Unit of radiation intensity is watts per steridian or per square degree.

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