Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
1999-11-30
2001-08-14
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C343S853000
Reexamination Certificate
active
06275184
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to antenna systems and more particularly to an improved multi-level system and method for steering an antenna.
BACKGROUND OF THE INVENTION
Communications networks employ satellites operating in geosynchronous orbits in combination with terrestrial facilities such as land lines, microwave repeaters, and undersea cables to provide communications over vast areas of the earth. Geosynchronous satellites and terrestrial facilities are both expensive to install and to maintain and thus are not a cost effective means of increasing network capacity. In addition, geosynchronous satellites which operate at an altitude of 22,300 miles above the earth are unsuitable for supporting cellular service because of the extremely high power levels that would be required to communicate with satellites at that altitude.
More recently, constellations of low earth orbit (LEO) satellites have been proposed and are being developed as a cost effective means for providing increased capacity and supporting cellular and broadband data service for communications networks. In such a constellation, the satellites are divided into a number of orbital planes. Because low earth orbit satellites move rapidly with respect to the earth, each orbital plane includes a number of satellites that maintain continuous coverage for underlying cells defined on the surface of the earth. The cells represent coverage regions for the satellites.
Low earth orbit satellites utilize antennas which form a cluster of beams matching the ground-based cells. In each satellite, the beams must be steered to maintain alignment with the cells during the time the satellite moves one cell width along its orbit. After the satellite has moved one cell width, all the beams are ratcheted forward one cell width in the direction of flight and the beams are reassigned to the next set of cells in the flight direction.
Existing beam steering systems are inadequate due to their size, complexity, and cost. Mechanical steering apparatuses, for example, are too bulky, heavy and/or consume too much power for use in satellites. Electronic steering systems typically use multiple phase shifters per antenna array element or a hybrid divider network with distributed phase shifters as a variable power divider network. The use of phase shifters greatly increases complexity of the antenna system and thus cost.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved multi-level system and method for steering an antenna are provided that substantially reduced disadvantages and problems associated with previously developed systems and methods.
In one embodiment of the present invention, a system for steering an antenna is disclosed that includes a first component that includes a first lens and is operable to perform a first focusing of a plurality of signals to form a plurality of focused signals. The system also includes a second component that includes a second lens and is operable to form a first focused beam by performing a second focusing of the plurality of focused signals. The second component further includes a first splitter and is further operable to split the first focused beam into a first set of intermediate beams. The system further includes a third component that includes a second splitter and is operable to split a particular one of the first set of intermediate beams into a second set of intermediate beams. The third component further includes a first combiner and is further operable to combine a particular one of the second set of intermediate beams with at least one other intermediate beam split from a second focused beam to generate a composite beam. The system includes an additional fourth component that includes a second combiner and is operable to combine the composite beam with at least one other composite beam to generate a steered final composite beam for a particular ground-based cell.
In another embodiment of the present invention, a system for steering an antenna includes a first component that includes a first lens and is operable to perform a first focusing of a plurality of signals received from a ground-based cell. The system further includes a second component that includes a second lens, a splitter, and a first combiner and is operable to perform a second focusing of the plurality of signals to form a first focused beam. The second component is further operable to split the first focused beam into a plurality of intermediate beams and combine at least one of the plurality of intermediate beams with at least one other intermediate beam split from a second focused beam to generate a composite beam. The system also includes a third component that includes a second combiner and is operable to combine the composite beam with at least one other composite beam thereby generating a steered final composite beam for the ground-based cell.
In yet another embodiment of the present invention, a method of steering an antenna includes focusing a plurality of signals into a focused beam, splitting the focused beam into a plurality of intermediate beams, combining at least one of the intermediate beams with at least one other intermediate beam split from another focused beam to generate a composite beam, and combining the composite beam with at least one other composite beam.
Technical advantages of the present invention include providing an improved system and method for steering an antenna. In particular, various embodiments of the antenna system use a planar lens array to focus signals. The planar lenses allow lensing and amplitude modulation functions to be combined into planar slats. As a result, the beam forming and steering network can be located internally to a satellite or other platform without only radiating elements protruding from the base. The planar slats can be manufactured in such a manner so as to be ideal for satellite or other applications where size or weight considerations are significant. Additionally, various embodiments of the present invention allow many different circuit elements to be fabricated within a common slat, such as a microwave circuit board, such that efficient steering of signals from distant cells may be accomplished using a compact structure composed of levels of slats. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
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Dover R. Thomas
Harrison, Jr. John H.
Haws James L.
Hemmi Christian O.
Webb David B.
Baker & Botts L.L.P.
Mull Fred H.
Raytheon Company
Tarcza Thomas H.
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