Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
1999-11-05
2001-06-05
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C434S383000
Reexamination Certificate
active
06243051
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to antenna systems, and more particularly, this invention relates to an antenna having helical antenna elements.
BACKGROUND OF THE INVENTION
A conventional satellite antenna system used for generating global positioning system (GPS) and similar signals typically includes the satellite body having a controller and transmitter. An earth deck panel is connected to the satellite body and includes phased array antenna elements supported by the earth deck panel that emits the GPS signals. However, in hostile areas in time of war, or when special operations are performed, such as by special forces, the hostile areas have enemy jamming stations that make the receipt of GPS signals difficult. Thus, not only do special forces in hostile areas have difficulty receiving GPS signals, but also cruise missiles and other modern electronic devices have trouble receiving the GPS signals because of jamming interference. This area of conflict could be a larger or smaller area depending on the fact situation. Depending on the particular problem, greater signal power must be generated over the area of regard.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an antenna that is selectable to broaden a transmitted energy beam and area of regard, such as for global positioning system signals in hostile areas.
In accordance with the present invention, the antenna includes a reflector having a focal point. A central support shaft extends axially from the reflector to the focal point. First and second selectable, multi-turn axial mode helical antenna elements are disposed on-bore on the central support shaft and spaced linearly from each other. The helical antenna elements are wound to have the same polarity. One of the helical antenna elements is disposed at the focal point, and the other helical antenna element is disposed at a defocused position to broaden the transmitted energy beam and area of regard.
In still another aspect of the present invention, first and second independent feed lines extend to respective first and second helical antenna elements. An antenna feed line switch is operatively connected to the first and second independent feed lines for switching from one feed line into the other feed line to switch between a narrow beam and a broadened energy beam and area of regard.
The first helical antenna element can be spaced distal from the reflector at the focal point, and the second helical antenna element can be spaced proximal to the reflector. The first and second independent feed lines connect to the respective first and second antenna elements. First and second ground planes are mounted on the central support shaft in spaced relation from each other and are operative with respective first and second helical antenna elements. The ground planes can be formed as circular plates supported on the central support shaft.
In still another aspect of the present invention, the first and second helical antenna elements comprise monofilar wire wound around the central support shaft. The helical antenna elements could be wound to have right-hand or left-hand polarization. The central support shaft further comprises material formed as a dielectric.
In still another aspect of the present invention, a satellite system of the present invention comprises a satellite body having a transmitter for generating signals to the earth. An earth deck panel is part of the satellite body. Phased array antenna elements are supported by the earth deck panel and emit the signals. A reflector boom extends from the satellite body. The antenna of the present invention is supported by the reflector boom for use in emitting the signals in times of conflict to overcome jamming.
The antenna includes the reflector having a focal point and a central shaft extending axially from the reflector through the focal point. First and second selectable, multi-turn axial mode helical antenna elements are disposed on the central support shaft, spaced linear from each other, and wound to have the same polarity. One of the helical antenna elements is disposed at the focal point, and the other helical antenna element is disposed at a defocused positioned to broaden a transmitted energy beam and area of regard.
A transmission line is operatively connected to the antenna feed line switch for carrying signals to be transmitted from the antenna. The central support shaft can include a passageway extending axially therethrough that receives the first and second independent feed lines.
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Corbit Robert A.
Vanstrum Mark D.
Yost Timothy L.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Chen Shih-Chao
Harris Corporation
Ho Tan
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