Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
1998-12-23
2001-07-24
Phan, T. (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S757000, C343S761000, C343S7810CA
Reexamination Certificate
active
06266024
ABSTRACT:
TECHNICAL FIELD
The present invention relates to space and communications antennas. More particularly, the present invention relates to a rotatable and scannable reconfigurable shaped reflector with a movable feed system.
BACKGROUND ART
It is typical to customize a satellite for a particular country or geographic area based on a given orbital location of the satellite. This limits the satellite to use only for that specific application. If a situation arises where it becomes necessary to change geographic areas, a newly configured satellite must be launched in order to effect change.
In the case of a malfunction of a satellite, another satellite must be built to a similar performance specification. This can result in a delay of up to three years, for the build and launch of the replacement satellite. A reconfigurable antenna system would alleviate some of the drawbacks associated with area specific satellite systems.
There are complex approaches to achieving efficient reconfigurable antennas. However, these approaches have limited efficiency due to current amplifier designs. While in the future this approach may be possible with better amplifier designs, it is not yet practical to employ active antennas.
A rotatable antenna beam may be accomplished by rotating a subreflector in a Gregorian dual reflector. The subreflector is initially shaped to generate a simple elliptic beam. However, the beam size is limited to about 3 to 4 degrees, since the subreflector shaping is limited in its capabilities. This is a disadvantage because many current day C-band beams are very large. Another drawback is that subreflector shaping limits the beam shapes to simple shapes, and most applications require complex beam shape capability.
SUMMARY OF THE INVENTION
The present invention is an antenna system that provides efficient beam reconfiguration without the drawbacks associated with known technology. The antenna system of the present invention has at least one antenna that can be reconfigured to operate for a large coverage area and allows complex beam shape capability.
The antenna system of the present invention has a main reflector shape that is initially optimized for a predetermined radiation pattern or beam shape. From the optimized radiation pattern, an optimum axis is determined. A rotating and gimbaling mechanism is located on the optimum axis to allow beam rotation and gimbaling about the optimum axis. The optimum axis is used because it allows the beam to rotate without changing its shape. The beam position does not change as it is rotated about the optimum axis. Therefore the beam position does not change. The beam can be rotated without distorting the beam shape.
It is an object of the present invention to provide a low cost, high efficiency reconfigurable antenna. It is another object of the present invention to provide a reconfigurable antenna that is capable of producing very large, complex beam shapes.
It is still another object of the present invention to provide a reconfigurable antenna that will provide flexibility to satellite coverage patterns making it possible to alter a satellite's coverage area.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
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Cascia Vincent E.
Fermelia Louis R.
Park Brian M.
Ramanujam Parthasarathy
Gudmestad T.
Hughes Electronics Corporation
Phan T.
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