| 摘要 |
22 A switched beam antenna comprising several spiral arms with a common axis of rotation and respective inner ends angularly spaced around a common circle generates high gain directional beams at an angle away from the antenna axis. Beam scanning is accomplished by rotating the feed to the arms by means of a commutator circuit. Intermediate beams may be generated by feeding two adjacent antenna arms simultaneously but with an appropriate phase shift. A comparator may be provided to compare signals from several arms and select the arm yielding maximum signal strength.
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