Steerable beam antenna system using butler matrix
First Claim
1. A method of operating a frequency addressable, steerable beam antenna system, comprising the steps of:
- (a) providing a set of first signals having a predetermined phase relationship with respect to one another and containing information to be transmitted, each of said first signals having a carrier frequency related to its corresponding phase;
(b) generating a set of second signals from said set of first signals by at least approximately performing a spatial transformation on the amplitude and distribution of said set of first signals, including the step of feeding said first set of signals to the inputs of a Butler matrix such that the phase of the first signals varies from input-to-input of said matrix in a predetermined relationship, said Butler matrix including a plurality of outputs for delivering said second set of signals, the phase distribution of said second set of signals at said outputs being determined by the predetermined relationship of the phases of said first signals;
(c) feeding said second set of signals from the outputs of said Butler matrix to a plurality of feed elements of an antenna array in a manner such that the phases of the second set of signals vary from feed element to feed element in accordance with said predetermined phase relationship; and
(d) transmitting said set of second signals toward a reflector from said antenna array at a position located near a focal point of the reflector in a manner to from a plurality of beams of electromagnetic radiation where each of said beams is associated with a particular one of said carrier frequencies.
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Abstract
A steerable beam antenna system for use in satellite communication systems and including a main reflector and an antenna array having a plurality of feed elements is disclosed. The antenna array is positionable at or near at least one focal point of the main reflector, and its feed elements can receive microwaves from or transmit microwaves toward the main reflector. A Butler matrix having multiple input ports and multiple outputs is connected to the array of feed elements and substantially performs a spatial Fourier transformation on a generated set of signals to be transmitted which have a predetermined phase relationship between the signals, which is necessary to create the steerable beam. The Butler matrix also can perform an inverse spatial transformation on a set of incoming signals focused on the array by the reflector and received by the feed elements. By using a Butler matrix, the antenna system of the present invention is able to communicate with multiple ground stations simultaneously and with high gain using many virtual spot beams, each oriented to a distinct location on the earth that is dependent on the relative frequency of the beam.
78 Citations
29 Claims
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1. A method of operating a frequency addressable, steerable beam antenna system, comprising the steps of:
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(a) providing a set of first signals having a predetermined phase relationship with respect to one another and containing information to be transmitted, each of said first signals having a carrier frequency related to its corresponding phase; (b) generating a set of second signals from said set of first signals by at least approximately performing a spatial transformation on the amplitude and distribution of said set of first signals, including the step of feeding said first set of signals to the inputs of a Butler matrix such that the phase of the first signals varies from input-to-input of said matrix in a predetermined relationship, said Butler matrix including a plurality of outputs for delivering said second set of signals, the phase distribution of said second set of signals at said outputs being determined by the predetermined relationship of the phases of said first signals; (c) feeding said second set of signals from the outputs of said Butler matrix to a plurality of feed elements of an antenna array in a manner such that the phases of the second set of signals vary from feed element to feed element in accordance with said predetermined phase relationship; and (d) transmitting said set of second signals toward a reflector from said antenna array at a position located near a focal point of the reflector in a manner to from a plurality of beams of electromagnetic radiation where each of said beams is associated with a particular one of said carrier frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 28)
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12. An antenna system for producing a set of frequency addressable beams of electromagnetic radiation, comprising:
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a reflector for reflecting electromagnetic radition and having a focal point associated therewith; a frequency selective beam former for forming a plurality of beams of electromagnetic radiation using a plurality of respectively associated beam forming signals, said beam forming signals being shifted in phase relative to each other and possessing carrier frequencies which are a function of the phase shift between said signals; transformation means coupled with said beam former and positioned essentially at said focal point of said reflector for essentially performing a spatial transformation on the amplitude and phase distribution of said beam forming signals, said transformation means including a plurality of inputs for receiving said beam forming signals, the phase distribution of said signals being in a predetermined relationship among said inputs, and a plurality of outputs for delivering the transformer beam forming signals, the phase distribution of said signals delivered at said outputs being determined by said preselected relationship of the phase distribution of said signals at said inputs; and an antenna array having a plurality of feed elements coupled with said outputs of said transformation means so as to receive the beam forming signals as a function of the phase distribution of said signals, said antenna array being positioned so as to direct electromagnetic energy toward said reflector, the electromagnetic energy received by said reflector from said antenna array being reflected to form a plurality of beams of electromagnetic energy where each of said beams is associated with a particular one of said frequencies and emanates from one of said feed elements which receives a beam forming signal having a phase corresponding to the particular frequency. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 29)
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Specification