Question
What is the 3 dB beamwidth of the antenna radiation pattern shown in Figure E9-1?
Answer Options
- A) 75 degrees
- B) 50 degrees
- C) 25 degrees
- D) 30 degrees
Correct Answer: B
Explanation
The beamwidth of a directional antenna is a measure of its directivity, defined as the angle between the two points in the main lobe where the radiated power drops to one-half (-3dB) of its peak value. This angular width determines the area over which the antenna is most effective.
Referring to Figure E9-1, the maximum gain is at 0°. The -3 dB points are located at approximately +25° and -25° relative to the main axis. The beamwidth is the angle between these two points: 25° - (-25°) = 50°. This value indicates that the antenna maintains high gain over a 50° arc.
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