Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
2000-10-06
2001-10-16
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S770000
Reexamination Certificate
active
06304228
ABSTRACT:
BACKGROUND
The present invention relates generally to spacecraft communication systems, and more particularly, to a stepped waveguide slot array antenna system having phase control and satellite communication system employing same.
The assignee of the present invention manufactures and deploys communication satellites. Such communication satellites carry communication systems and antennas that are used to communicate with ground-based communication devices. Heretofore, certain antennas used in such communication systems have employed conventional waveguide slot array designs.
Previous conventional waveguide slot array designs used in-phase radiation contributions from each slot in the array. These designs are well known for their high efficiency but are limited to applications where in-phase contribution produced rather simple beamshapes.
It would therefore be desirable to have a waveguide slot array antenna system for use in a satellite-based communication system that provides phase control. It is therefore an objective of the present invention to provide for a stepped waveguide slot array antenna system having phase control and satellite communication system employing same.
SUMMARY OF THE INVENTION
To accomplish the above and other objectives, the present invention comprises a satellite having a communication system employing an improved stepped waveguide slot array antenna system. The stepped waveguide slot array antenna system provides for improved phase control and results in an improved beam pattern produced by the antenna system.
The stepped waveguide slot array antenna system comprises a plurality of stepped slot waveguides arranged in an array that are fed by a feed waveguide. The stepped slot waveguides have a plurality of slots disposed in their respective radiating surfaces or broadwalls. The slots in each waveguide are alternately offset from a centerline of the waveguide.
More particularly, the slots are spaced at half guide wavelength intervals and adjacent slots are positioned on opposite sides of the centerline of the waveguide. In accordance with the present invention, the slots are located at different axial positions (i.e., orthogonal to the plane of the array). The plurality of stepped slot waveguides provide an impedance matched arrangement of axially stepped waveguide sections that couple RF energy between the feed waveguide and the plurality of radiating slots.
In general, a single feed waveguide couples energy between an input/output port at the back side of the array antenna system and each of the plurality of stepped slot waveguides. The stepped waveguide slot array antenna is part of a satellite communication system comprising a transmitter and/or a receiver that are disposed on a satellite. The transmitter and/or receiver are coupled to the input/output port of the feed waveguide.
The present invention thus provides for a waveguide slot array having high efficiency and structural rigidity that has a configuration capable of allowing electrical phase to be selected by design. This is accomplished by stepping the array (employing stepped waveguides) to provide the desired phase resulting from differential path length in the far field.
The advantage of using the stepped waveguide slot array antenna system is that the radiated phase contribution from each slot may be selected by design of the axially position of each slot in the array. The slots radiate in-phase field contributions but their out-of-plane axial positions allow them to contribute to any desired phase in the far field of the antenna system.
The out-of-phase contributions from each slot in the array antenna system produce a shaped beam. This is not possible using conventional waveguide slot arrays. In the present invention, the phases of each contributing slot is provided by a path length determined by the axial position of the slot. This path length phenomena results in an array antenna that provides very broadband performance.
REFERENCES:
patent: 5619216 (1997-04-01), Park
patent: 5650793 (1997-07-01), Park
patent: 5831583 (1998-11-01), Lagerstedt et al.
Duarte Juan
Hardie George
Smith Terry M.
Float Kenneth W.
Nguyen Hoang
Space Systems Loral, Inc.
Wong Don
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