System for simplification of reconfigurable beam-forming network processing within a phased array antenna for a telecommunications satellite
First Claim
1. A method of beam-forming for an antenna of a telecommunications spacecraft, the antenna comprising a phased array antenna, and the antenna providing a plurality of communications beams within a predefined geographical region, the method comprising:
- providing the phased array antenna as a plurality of antenna elements, each antenna element having an antenna element signal having a phase relationship and an amplitude relationship to the other element signals, and partitioning said antenna elements into a plurality of overlapping sub-arrays, each sub-array comprising a subset of all the antenna elements of the phased array, and at least some or all the antenna elements participating in more than one sub-array,allocating to elements of each sub-array respective intra sub-array beam-forming weights, and allocating to each sub-array respective main beam-forming weights for said plurality of communications beams such that the composite radiation pattern of the antenna provides said plurality of communications beams within said region,wherein a desired antenna directivity value for the plurality of communications beams is determined by an optimisation process, involving changing, in iterations, of said intra sub-array beam-forming weights, together with determination of main beam-forming weights for said beams at each said iteration.
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Abstract
A telecommunications satellite having a phased array antenna, wherein the beam-forming function within the phased array is simplified by partitioning it into two stages, in which the sub-array stage relates to a fixed, or infrequently changed, set of overlapping sub-arrays and the main stage provides the main pattern reconfiguration, typically in the form of multiple reconfigurable spot beams within a defined coverage region. The key advantage lies in the significant reduction in number of second stage beam-forming control points (at which independent amplitude and phase is applied) when compared with a conventional phased array (where amplitude and phase control is applied for each element of the array). The sub-array stage beam-forming may be implemented in analogue technology. The main beam-former may be implemented in digital technology, where the key processing functions of A/D or D/A conversion, frequency (de)multiplexing and digital beam-forming all scale with the number of control points.
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Citations
35 Claims
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1. A method of beam-forming for an antenna of a telecommunications spacecraft, the antenna comprising a phased array antenna, and the antenna providing a plurality of communications beams within a predefined geographical region, the method comprising:
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providing the phased array antenna as a plurality of antenna elements, each antenna element having an antenna element signal having a phase relationship and an amplitude relationship to the other element signals, and partitioning said antenna elements into a plurality of overlapping sub-arrays, each sub-array comprising a subset of all the antenna elements of the phased array, and at least some or all the antenna elements participating in more than one sub-array, allocating to elements of each sub-array respective intra sub-array beam-forming weights, and allocating to each sub-array respective main beam-forming weights for said plurality of communications beams such that the composite radiation pattern of the antenna provides said plurality of communications beams within said region, wherein a desired antenna directivity value for the plurality of communications beams is determined by an optimisation process, involving changing, in iterations, of said intra sub-array beam-forming weights, together with determination of main beam-forming weights for said beams at each said iteration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A phased array antenna, the antenna providing coverage over a predefined geographical region and providing a plurality of beams within said region, and comprising:
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a plurality of antenna elements, each antenna element having an antenna element signal having a phase relationship and an amplitude relationship to the other element signals, and said antenna elements being partitioned into a plurality of overlapping sub-arrays, each sub-array comprising a subset of all the antenna elements of the phased array, and at least some of the antenna elements participating in more than one sub-array, a sub-array beam-forming network which allocates to elements of each sub-array respective intra sub-array beam-forming weights, and a main beam-forming network which allocates to each sub-array main beam-forming weights for each of said plurality of beams such as to produce said plurality of beams within said region wherein intra sub-array beam-forming weights allocated to each sub-array have been optimised in order to attain a desired level of said directivity for said plurality of beams by an optimisation process wherein said intra sub-array beam-forming weights are changed in value in iterations, and at each iteration main beam-forming weight values allocated to said sub-arrays are determined. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. An optimisation process for determining beam-forming parameters of a phased array antenna, the antenna providing coverage over a predefined geographical region, and a plurality of beams within said region, the antenna having a plurality of antenna elements, each antenna element providing an antenna element signal having a phase relationship and an amplitude relationship to the other element signals, and the antenna elements being partitioned into a plurality of overlapping sub-arrays, each sub-array comprising a subset of all the antenna elements of the phased array, and at least some of the antenna elements participating in more than one sub-array, the optimisation process comprising:
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setting intra sub-array beam-forming weights allocated to each sub-array are set to initial values; determining in which main beam-forming weight values allocated to said sub-arrays are determined, to provide values of directivity at the locations of at least some of said beams; and changing, in iterations, the values of said intra sub-array beam-forming weights and determining at each iteration main beam-forming weight values allocated to said subarrays, until a desired level of said directivity for said beams is attained. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
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Specification