Multi-beam and multi-band antenna system for communication satellites
First Claim
1. An antenna system, comprising:
- a reflector having a modified-paraboloid shape; and
a multi-beam, multi-band feed array wherein;
said feed array is located close to a focal plane of said reflector;
said feed array includes at least one horn;
said feed array forms a plurality of multi-band beams, each of said plurality of multi-band beams being formed by a single horn of said feed array and each of said plurality of multi-band beams propagating signals over at least three frequency bands; and
said antenna system forms said plurality of beams so that each of said plurality of multi-band beams is congruent over said at least three frequency bands, and said plurality of beams is contiguous.
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Abstract
An antenna system includes a reflector having a modified-paraboloid shape; and a multi-beam, multi-band feed array located at a focal point of the reflector so that the antenna system forms a multiple congruent beams that are contiguous. The system has a single reflector with non-frequency selective surface. The reflector is sized to produce a required beam size at K-band frequencies and is oversized at EHF-band frequencies. The synthesized reflector surface is moderately shaped and disproportionately broadens EHF-band and Ka-band beams compared to K-band beams. The synthesized reflector surface forms multiple beams each having a 0.5-degree diameter at K-band, Ka-band, and EHF band. The multi-beam, multi-band feed array includes a number of high-efficiency, multi-mode circular horns that operate in focused mode at K-band and defocused mode at Ka-band and EHF-band by employing “frequency-dependent” design for the horns.
33 Citations
34 Claims
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1. An antenna system, comprising:
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a reflector having a modified-paraboloid shape; and a multi-beam, multi-band feed array wherein; said feed array is located close to a focal plane of said reflector; said feed array includes at least one horn; said feed array forms a plurality of multi-band beams, each of said plurality of multi-band beams being formed by a single horn of said feed array and each of said plurality of multi-band beams propagating signals over at least three frequency bands; and said antenna system forms said plurality of beams so that each of said plurality of multi-band beams is congruent over said at least three frequency bands, and said plurality of beams is contiguous. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An antenna system, comprising:
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a reflector having a modified-paraboloid shape; and a multi-beam, multi-band feed array, wherein; said feed array is located close to a focal plane of said reflector; said feed array includes at least one horn; said multi-beam, multi-band feed array is focused at a lowest frequency band, wherein a lowest frequency horn phase center of said at least one horn is located close to said focal plane; said multi-beam, multi-band feed array is defocused at a highest frequency band and at an intermediate frequency band, wherein a highest frequency horn phase center and an intermediate frequency horn phase center are located behind said focal plane away from said reflector said feed array forms a plurality of beams, each of said plurality of beams being formed by a single horn of said feed array; and said antenna system forms said plurality of beams so that each of said plurality of beams is congruent, and said plurality of beams is contiguous. - View Dependent Claims (10)
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11. An antenna system, comprising:
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a reflector having a modified-paraboloid shape; and a multi-beam, multi-band feed array, wherein; said multi-beam, multi-band feed array is located close to a focal plane of said reflector; said multi-beam, multi-band feed array comprises a plurality of feed horns; and said feed horns are placed on a spherical cap with a radius of a distance from an aperture center of said reflector to said focal point, said radius of said spherical cap centered at the aperture center; said multi-beam, multi-band feed array forms a plurality of beams, each of said plurality of beams being formed by a single feed horn of said feed array; and said antenna system forms said plurality of beams so that each of said plurality of beams is congruent, and said plurality of beams is contiguous.
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12. An antenna system, comprising:
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a reflector having a modified-paraboloid shape; a compact 6-port OMT/polarizer wherein said feed array provides dual-circular polarization capability at each of three distinct frequency bands; and a multi-beam, multi-band feed array wherein; said feed array is located close to a focal plane of said reflector; said feed array includes at least one horn; said feed array forms a plurality of beams, each of said plurality of beams being formed by a single horn of said feed array; and said antenna system forms said plurality of beams so that each of said plurality of beams is congruent, and said plurality of beams is contiguous.
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13. A reflector for an antenna system, comprising:
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a non-frequency selective reflector surface, wherein; said reflector surface has a modified-paraboloid shape; said reflector is sized having an aperture D to produce a required beam size at a lowest frequency band; said reflector is oversized at an intermediate frequency band, wherein said reflector is oversized in that a reflector having aperture D with unmodified paraboloid shape produces a beam size at said intermediate frequency band that is smaller than said required beam size; and said reflector is oversized at a highest frequency band, wherein said reflector is oversized in that a reflector having aperture D with unmodified paraboloid shape produces a beam size at said highest frequency band that is smaller than said required beam size. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A reflector for an antenna system, comprising:
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a non-frequency selective reflector surface, wherein said reflector surface has a modified-paraboloid shape; and
wherein;said reflector is sized to produce a required beam size at a lowest frequency band; and said reflector is sized to have an aperture D according to; D=70×
(wavelength (at 20.2 GHz))/(half-power beam-width) to produce said required beam size at a K-band frequency taking the effect of beam broadening at K-band caused by said reflector having said modified paraboloid shape into account; andsaid reflector is oversized at a highest frequency band, wherein said reflector is oversized in that a reflector having aperture D with unmodified paraboloid shape produces a beam size at said highest frequency band that is smaller than said required beam size.
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21. A feed array for an antenna system, comprising:
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a plurality of high-efficiency multi-mode circular horns, wherein; said feed array is focused at a lowest frequency band; said feed array is defocused at a highest frequency band; and
wherein;said feed array has a maximum feed size of 0.892 inch; and each of said plurality of high-efficiency multi-mode circular horns of said feed array is connected to a distinct compact 6-port OMT/polarizer wherein said feed array provides dual-circular polarization capability at each of the K, Ka, and EHF frequency bands.
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22. A feed array for an antenna system, comprising:
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a plurality of high-efficiency multi-mode circular horns, wherein; said feed array is focused at a lowest frequency band; said feed array is defocused at a highest frequency band; and
wherein;said feed array has a maximum feed size of 0.892 inch; and each of said plurality of high-efficiency multi-mode circular horns of said feed array is connected to a distinct compact 6-port OMT/polarizer wherein said feed array provides dual-circular polarization capability at each of the C, X, and Ku frequency bands.
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23. A satellite communication system comprising:
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a radio frequency communication system; an antenna system connected to said radio frequency communication system, wherein said antenna system includes; a reflector having a non-frequency selective reflector surface, wherein; said reflector is sized to produce a required beam size at a K-band frequency; said reflector is oversized at an EHF-band frequency, wherein said reflector is oversized at said EHF-band frequency compared to a reflector sized to produce a beam at said EHF-band frequency of said required beam size; said reflector surface is a synthesized surface of modified-paraboloid shape; said synthesized reflector surface is moderately shaped and disproportionately broadens EHF-band and Ka-band beams compared to K-band beams; said synthesized reflector surface forms a 0.5 degree beam at K-band, Ka-band, and EHF band; a multi-beam, multi-band feed array located at a focal point of said reflector, said feed array including a plurality of high-efficiency multi-mode circular horns, wherein; said feed array is focused at a K-band frequency; said feed array is defocused at a Ka-band frequency and an EHF-band frequency; a horn of said plurality of high-efficiency multi-mode circular horns of said feed array has an aperture diameter and a waveguide diameter; said horn has a first step, between said aperture diameter and said waveguide diameter, at which the diameter of the circular cross-section of said horn abruptly changes; and said horn has a second step, between said first step and said waveguide diameter, at which the diameter of the circular cross-section of said horn abruptly changes. - View Dependent Claims (24, 25, 26, 27)
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28. A method of propagating a multi-beam, multi-band radio signal comprising steps of:
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forming a plurality of multi-band beams having at least three frequency bands wherein a lowest frequency band is formed in a focused mode, an intermediate band is formed in a defocused mode, and a highest frequency band is formed in a defocused mode; and reflecting said multi-band beams off a shaped reflector to form multi-band beams that are congruent over the at least three frequency bands and are contiguous. - View Dependent Claims (29, 30, 31, 32, 33)
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34. A method of propagating a multi-beam, multi-band radio signal comprising steps of:
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forming a plurality of congruent multi-band beams having at least three frequency bands, including forming a circularly polarized beam using an OMT/polarizer that provides dual-circular polarization capability at each of the at least three frequency bands, wherein a lowest frequency band is formed in a focused mode, a higher frequency band is formed in a defocused mode and a highest frequency band is formed in a defocused mode; and reflecting said multi-band beams off a shaped reflector to form congruent multi-band beams that are contiguous.
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Specification