360.degree. Azimuth scanning antenna without rotating RF joints
First Claim
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1. A 360* scanning high-frequency antenna system comprising:
- an antenna platform;
a supporting framework surrounding and attached to said platform;
tertiary reflecting means for reflecting electromagnetic energy;
rotating means attached between said tertiary reflecting means and said platform for rotating said tertiary reflecting means about an axis of rotation;
a plurality of high-frequency primary focusing-structures attached to said supporting framework and arranged in a generally circular fashion about said axis of rotation;
a plurality of secondary focusing-structures attached to said supporting framework and arranged in a generally circular fashion about said axis of rotation, each said secondary focusing-structure being associated with a corresponding one or said primary focusing-structures; and
, switching means for energizing selected primary-focusing structures when said tertiary reflecting means is positioned to reflect energy radiating from said selected primary focusingstructures as collimated by said corresponding secondary focusing-structure whereby said energy is reflected by said tertiary reflecting means.
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Abstract
A 360* scanning radar antenna has a plurality of primary focusing-structures arranged in a circular fashion illuminating corresponding secondary focusing-structures which in turn are arranged about, and directed toward, a rotating multi-sided halfwave plane reflector. Radar energy is switched to radiate from a given primary focusing-structure during the time when the plane reflector is in position to reflect all of the energy collimated by the corresponding secondary focusing-structure. The secondary focusing-structure may be made to appear transparent to the beam reflected by the plane reflector.
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Citations
6 Claims
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1. A 360* scanning high-frequency antenna system comprising:
- an antenna platform;
a supporting framework surrounding and attached to said platform;
tertiary reflecting means for reflecting electromagnetic energy;
rotating means attached between said tertiary reflecting means and said platform for rotating said tertiary reflecting means about an axis of rotation;
a plurality of high-frequency primary focusing-structures attached to said supporting framework and arranged in a generally circular fashion about said axis of rotation;
a plurality of secondary focusing-structures attached to said supporting framework and arranged in a generally circular fashion about said axis of rotation, each said secondary focusing-structure being associated with a corresponding one or said primary focusing-structures; and
, switching means for energizing selected primary-focusing structures when said tertiary reflecting means is positioned to reflect energy radiating from said selected primary focusingstructures as collimated by said corresponding secondary focusing-structure whereby said energy is reflected by said tertiary reflecting means.
- an antenna platform;
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2. The 360* scanning antenna system of claim 1, wherein:
- said primary focusing-structures are adapted to radiate linearly polarized energy of predetermined orientation;
said secondary focusing-structures are made polarization sensitive so as to reflect energy polarized in one direction and to pass orthogonally polarized energy without attenuation;
said tertiary reflecting means is a reflector having a plurality of half-wave plane reflective surfaces constructed so that the direction of polarization energy incident on any of said half-wave reflective surfaces will be changed by 90* upon reflection, whereby energy from said primary focusing-structures polarized in one direction is collimated and reflected to said tertiary reflecting means by said secondary focusing structures and said reflected energy is rotated in polarization by 90* and reflected back through said secondary focusing-structures by said tertiary reflecting means.
- said primary focusing-structures are adapted to radiate linearly polarized energy of predetermined orientation;
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3. The 360* scanning antenna system of claim 2 wherein the width of said tertiary reflecting means is 1/cos 45* times the width in the scan plane of one of said secondary focusing-structures.
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4. The antenna system of claim 3 wherein said switching means energizes selected primary focusing-structures when said tertiary reflector forms an angle of not more than 45* to either side of the optical axis of said corresponding secondary focusing-structure.
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5. The 360* scanning antenna system of claim 4 wherein a environment stable, electromagnetically transparent enclosure is attached to and encloses said supporting framework.
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6. The 360* scanning antenna system of claim 5 wherein said enclosure is constructed of fiberglass.
Specification