High efficiency optical limited scan antenna
First Claim
1. A high efficiency, limited scan optical antenna system, comprising:
- an aperture lens having a circular inner surface with a finite radius and a linear aperture, said aperture lens comprising a plurality of radiating elements disposed along said linear array and a corresponding plurality of pickup elements disposed along said inner surface, corresponding ones of said radiation and pickup elements being coupled together by equal lengths of transmission lines;
an rf feed system comprising a plurality of feed elements, said system comprising means for providing a source distribution of rf radiation; and
a symmetric optical corrective lens centered at the center of said inner surface, said corrective lens comprising means for imaging the radiation at each feed element to a corresponding image point on said inner surface of said aperture lens so as to map the source distribution of said feed elements onto said inner surface to form an aperture distribution which is a scaled version of said source distribution.
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Accused Products
Abstract
An optical limited scan antenna system is disclosed. The invention is a dual lens type array antenna system with a small array feed network. The system includes a bootlace-type microwave aperture lens with an array of radiating elements arranged along the linear aperture and an array of pickup elements arranged along the curved inner surface, an intermediate optical corrective lens, a feed array for illuminating the corrective lens with a source distribution, and with a power divider and phase shifters arranged to drive the feed array. The corrective lens is circularly symmetric (spherically symmetric in the three-dimensional case), and its radially varying dielectric constant is such that a point source on its surface is focused to an image point on the inner surface. The pickup elements on the curved surface of the aperture lens are coupled to corresponding radiating elements on the linear aperture. The corrective and aperture lens cooperate to map an input or source distribution into an aperture distribution which is a scaled version of the source distribution. The system results in high efficiency obtained with a minimum number of active elements and relatively low cost optical components.
76 Citations
21 Claims
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1. A high efficiency, limited scan optical antenna system, comprising:
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an aperture lens having a circular inner surface with a finite radius and a linear aperture, said aperture lens comprising a plurality of radiating elements disposed along said linear array and a corresponding plurality of pickup elements disposed along said inner surface, corresponding ones of said radiation and pickup elements being coupled together by equal lengths of transmission lines; an rf feed system comprising a plurality of feed elements, said system comprising means for providing a source distribution of rf radiation; and a symmetric optical corrective lens centered at the center of said inner surface, said corrective lens comprising means for imaging the radiation at each feed element to a corresponding image point on said inner surface of said aperture lens so as to map the source distribution of said feed elements onto said inner surface to form an aperture distribution which is a scaled version of said source distribution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A high efficiency, limited scan optical antenna system, comprising:
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an aperture lens having a circular inner surface and a linear aperture; a plurality of radiating elements disposed along said linear aperture; and a plurality of corresponding pick-up elements disposed along said circular inner surface, corresponding ones of said radiating elements and said pick-up elements being coupled together by equal lengths of transmission lines; a feed network comprising a plurality of feed elements for providing a source distribution of rf energy; a circularly symmetric optical corrective lens centered at the center of said circular inner surface of said aperture lens, said feed elements being disposed adjacent the surface of said corrective lens to illuminate said surface with said source distribution, said corrective lens comprising means for imaging each point source of radiation at the surface of the corrective lens to a corresponding image point on the inner surface of the aperture lens so as to map the source distribution onto said circular inner surface of said aperture lens to form an aperture distribution at said linear aperture which is a scaled version of said source distribution.
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14. A high efficiency, limited scan antenna system, comprising:
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a bootlace-type aperture means, comprising a concave inner surface and a linear aperture, a plurality of equally spaced radiating elements disposed along said linear aperture, a plurality of equally spaced pickup elements disposed along said inner surface, and a plurality of transmission lines of equal length connecting respective ones of said pickup elements to a corresponding one of said radiating elements, said respective corresponding radiating element being spaced from the center of the linear aperture by a distance equal to the arc length distance from the corresponding pickup element to a central surface point on said inner surface; a circularly symmetric intermediate lens having a radially varying dielectric constant, said lens disposed at the focal point of said inner surface and adapted such that each radiation source point on is surface is focused at a corresponding image point on said inner surface of said aperture lens; a power divider having an input port and a plurality N of output ports; a feed array comprising N feed elements for illuminating the corrective lens with an input distribution; a plurality N of phase shifters for respectively coupling respective output port to a corresponding feed element; said power divider and phase shifters adapted to provide a source distribution having a constant amplitude and constant phase; and phase shifter controller for controlling the amount of phase shift introduced by the respective phase shifters so as to position the beam produced by said system over a limited angular scan from broadside.
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15. A limited scan antenna system, comprising:
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means for providing a substantially two dimensional source distribution of electromagnetic energy, said means comprising a plurality of feed elements disposed along a source arc of radius f; a circularly symmetric corrective lens having a radius substantially equal to the radius f of said source arc for transforming said source distribution into a corresponding image distribution along an image arc at a radius F from the center of the corrective lens, said lens at a corresponding image point on said image arc; means for transforming said image distribution into a substantially linear aperture distribution; and means for scanning said source distributed over a limited angular scan about the broadside condition. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification