Question
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?
Answer Options
- A) Omni-directional
- B) Cardioid
- C) A figure-eight broadside to the axis of the array
- D) A figure-eight end-fire along the axis of the array
Correct Answer: C
Explanation
Antenna arrays where elements are spaced rac{1}{2}-wavelength apart and fed in phase typically create a broadside array, where the maximum radiation is perpendicular to the line connecting the elements. This configuration is widely used to achieve gain and directivity.
When two quarter-wave vertical antennas are spaced rac{1}{2}-wavelength apart and fed in phase, the energy combines constructively on the broadside direction and cancels on the end-fire direction. This results in a figure-eight pattern broadside to the axis of the array, meaning the maximum gain is perpendicular to the line connecting the two antennas, offering gain and rejection from the ends.
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