Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Reexamination Certificate
2000-08-11
2002-08-06
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
C343S777000, C343S914000
Reexamination Certificate
active
06429823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to antenna systems, and in particular to a horn reflect array element for enhanced performance.
2. Description of Related Art
Communications satellites have become commonplace for use in many types of communications services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such, satellites must provide signals to various geographic locations on the Earth's surface. As such, typical satellites use customized antenna designs to provide signal coverage for a particular country or geographic area.
Typical antenna systems use either parabolic reflectors or shaped reflectors to provide a specific beam coverage, or use a flat reflector system with an array of reflective printed patches or dipoles on the flat surface. These “reflect array” reflectors used in antennas are designed such that the reflective patches or dipoles shape the beam much like a shaped reflector or parabolic reflector would, but are much easier to manufacture and package on the spacecraft.
However, satellites typically are designed to provide a fixed satellite beam coverage for a given signal. For example, Continental United States (CONUS) beams are designed to provide communications services to the entire continental United States. Once the satellite transmission system is designed and launched, changing the beam patterns is difficult.
The need to change the beam pattern provided by the satellite has become more desirable with the advent of direct broadcast satellites that provide communications services to specific areas. As areas increase in population, or additional subscribers in a given area subscribe to the satellite communications services, e.g., DirecTV, satellite television stations, local channel programming, etc., the satellite must divert resources to deliver the services to the new subscribers. Without the ability to change beam patterns and coverage areas, additional satellites must be launched to provide the services to possible future subscribers, which increases the cost of delivering the services to existing customers.
Some present systems are designed with minimal flexibility in the delivery of communications services. For example, a semi-active multibeam antenna concept has been described for mobile satellite antennas. The beams are reconfigured using a Butler matrix and a semi-active beamformer network (BFN) where a limited number (3 or 7) of feed elements are used for each beam and the beam is reconfigured by adjusting the phases through an active BFN. This scheme provides limited reconfigurability over a narrow bandwidth and employs complicated and expensive hardware.
Another minimally flexible system uses a symmetrical Cassegrain antenna that uses a movable feed horn, which defocuses the feed and zooms circular beams over a limited beam aspect ratio of 1:2.5. This scheme has high sidelobe gain and low beam-efficiency due to blockage by the feed horn and the subreflector of the Cassegrain system. Further, this type of system splits or bifurcates the main beam for beam aspect ratios greater than 2.5, resulting in low beam efficiency values.
It can be seen, then, that there is a need in the art for a communications system that can be reconfigured in-flight to accommodate the changing needs of uplink and downlink traffic. It can also be seen that there is a need in the art for a communications system that can be reconfigured in-flight without the need for complex systems. It can also be seen that there is a need in the art for a communications system that can be reconfigured in-flight that has high beam-efficiencies and high beam aspect ratios.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a horn reflect array antenna system and a method for producing a signal using a horn reflect array antenna. The system comprises at least one reflective element illuminated by an incident radio frequency (RF) signal from a feed horn, the reflective element reflecting a portion of the incident RF signal as a portion of a reflected RF signal, and at least one phase shifting device, each phase shifting device coupled to a corresponding reflective element, wherein a beam pattern of the reflected RF signal is altered when the phase shifting element changes the phase of the portion of the reflected RF signal.
A method in accordance with the present invention comprises illuminating a reflector with an RF signal emanating from a feed horn, wherein the reflector comprises at least one reflective element, reflecting at least a portion of the RF signal from the reflective element, wherein the reflective element comprises a phase shifting device, and changing a phase of the portion of the reflected RF signal with the phase shifting device, therein altering the radiation pattern of the reflected RF signal.
The present invention provides a communications system that can be reconfigured in-flight to accommodate the changing needs of uplink and downlink traffic. The present invention also provides a communications system that can be reconfigured in-flight without the need for complex systems. The present invention also provides a communications system that can be reconfigured in-flight that has high beam-efficiencies and high beam aspect ratios.
REFERENCES:
patent: RE28546 (1975-09-01), Foldes
patent: 4198640 (1980-04-01), Bowman
patent: 4684952 (1987-08-01), Munson et al.
patent: 5543809 (1996-08-01), Profera
patent: 6081234 (2000-06-01), Huang et al.
patent: 6195047 (2001-02-01), Richards
Bains Paramjit S.
Ramanujam Parthasarathy
Gates & Cooper LLP
Hughes Electronics Corporation
Wimer Michael C.
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