Antennas Multiple Choice Questions on “Corner Reflector”.
1. Corner reflector is designed for radiation in forward direction unlike in plane reflector.
a) True
b) False
Answer: a
Clarification: The plane reflector allows back and side radiation. In order to avoid this it is modifies to a corner reflector which consists of two plane reflectors joined at a corner to allow radiation in forward direction only.
2. In a corner reflector, included angle α refers to _______
a) angle at which two plane reflectors are joined
b) angle between vertex and the feed radiator
c) angle between major axis to the main beam
d) angle between vertex and the main beam axis
Answer: a
Clarification: A corner reflector consists of two plane reflectors joined at a corner to allow radiation in forward direction only. Included angle is the angle at which two reflectors are joined, measured at the corner.
3. In order to achieve good system efficiency in a corner reflector, the spacing between the vertex and the feed must be ______ as included angle decreases.
a) Increased
b) Decreased
c) Constant
d) Either increases or decreases
Answer: a
Clarification: The system efficiency in a corner reflector depends on the spacing between vertex of the corner and the feed. It is adjusted depending on the included angle. As the included decreases, spacing must be increased.
4. Corner angle of a corner reflector with 4 current elements is ______
a) (frac{π}{4})
b) (frac{π}{2})
c) (frac{π}{8})
d) 4π
Answer: a
Clarification: Corner angle of a corner reflector with 4 current elements is given by (α=frac{π}{N})
Given N=4
⇨ (α=frac{π}{N}=frac{π}{4}.)
5. Find the aperture dimension of the corner reflector having reflector sheet side length 1m?
a) 1.414
b) 2.828
c) 2
d) 1
Answer: a
Clarification: From the design equations of a corner reflector,
Aperture dimension DA= 1.414l
Where l is side length of reflector sheet and l=2d where d is distance between feed and vertex of the reflector.
6. In a corner reflector antenna, if the spacing between vertex of reflector and feed is 2m then side length of reflector sheet is _____cm.
a) 4
b) 2
c) 400
d) 200
Answer: c
Clarification: In a corner reflector antenna, side length of reflector sheet and l=2d
Where, d is distance between feed and vertex of the reflector.
Given d=2m so l=2*2=4m=400cm.
7. Which of the following statements is false for a corner reflector antenna?
a) Increases directivity in the forward direction
b) Back radiation is not reduced compare to the plane reflector
c) System efficiency depends on spacing between reflector vertex and the feed
d) Angle between the reflecting plates is called included angle
Answer: b
Clarification: Compared to the plane reflector antenna, back and side radiations are reduced in the corner reflector. A corner reflector consists of two plane reflectors joined at a corner to allow radiation in forward direction only. As the included angle decreases, spacing will increases.
8. The number of images, polarity and position in the analysis of the radiation field of corner reflector depends on what?
a) Only included angle
b) Polarization of feed element
c) Both included angle & Polarization of feed element
d) Neither included angle nor Polarization of feed element
Answer: c
Clarification: The number of images, polarity and position in the analysis of the radiation field of corner reflector depends on both included angle & Polarization of feed element with perpendicular polarization. Angle between the reflecting plates is called included angle.
9. Corner angle of a square corner reflector antenna is _____
a) 90°
b) 180°
c) 60°
d) 45°
Answer: a
Clarification: For a square reflector angle N=2 and corner angle is given by (α=frac{π}{N}=frac{π}{2}=90°.) A corner reflector consists of two plane reflectors joined at a corner to allow radiation in forward direction only. This is one of the most practically used antennas.
10. What is the corner angle of a flat reflector antenna?
a) 90°
b) 180°
c) 60°
d) 45°
Answer: b
Clarification: The corner angle depends on value of N (current element). For a flat reflector N=1. So the corner angle is (α=frac{π}{N}=π=180°.)