Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-05-26
2001-11-27
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06323809
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to the field of broadband antennas, and more particularly, to fragmented aperture antennas with tailored electromagnetic performances.
BACKGROUND OF THE INVENTION
An antenna is a device that can both transmit and receive electromagnetic waves of energy. Designing an antenna can be a complicated task because of the inherent properties of electromagnetics. Presently, antenna engineers physically scale or modify conventional antennas to best meet a particular application. However, in many instances, this procedure is suboptimal because a suitable conventional antenna may not exist or is not similar enough to meet a particular need. Antennas with broadband frequency coverage are desirable so the antenna can operate in a greater number of applications, but many conventional antennas with broadband coverage also include inadequacies that render them ultimately unacceptable.
For example, a multi-turn spiral antenna is a broadband antenna. However, the gain of the spiral antenna is essentially flat with frequency. The optimal use of the aperture area would yield a gain that increases with frequency, so the spiral antenna is suboptimal from because of its increases in gain over frequency.
Another example of a broadband antenna is the bow-tie antenna. A bow-tie antenna will radiate over a wide range of frequencies. Because the direction of radiation for the bow-tie antenna changes over the range of frequency, this feature renders the bowtie as suboptimal.
Thus, there is a need for an antenna that can overcome these limitations, deficiencies and inadequacies that is heretofore unaddressed.
SUMMARY OF THE INVENTION
Briefly described, the preferred embodiment of the present invention provides a new family of antennas—fragmented aperture antennas. The antenna includes a planar layer having a plurality of conductive and substantially non-conductive areas. Each area has a periphery that extends along a grid of first and second sets of parallel lines so that each area comprises one or more contiguous elements defined by the parallel lines. The locations of the conducting materials in the fragmented aperture antenna are determined by a multi-stage optimization procedure that tailors the performance of the antenna to a particular application. The resulting configuration and arrangement of conductive and substantially non-conductive areas enable communication of electromagnetic energy wirelessly in a specific direction to the planar layer when an electrical connection is made to at least one of the conductive areas.
The present invention can also be viewed as providing one or more methods. As an example, one such method is for making an antenna. The method includes a step of defining a planar grid defined by first and second sets of parallel lines so that the grid comprises a plurality of elements defined by the lines. The method additionally includes determining a first plurality of said elements that should be substantially conductive and a second plurality of said elements that should be substantially nonconductive so that a hypothetical antenna formed from said planar grid elements exhibits a desired frequency spectrum.
In an alternative embodiment, a broadband ground plane is created by using a similar optimization strategy as described above. The fragmented ground plane is a second patterned sheet placed behind the radiating layer to reflect the energy in the forward direction of the antenna. The fragmented ground plane is a patterned layer similar to the radiating antenna aperture. A feed is applied to the radiating aperture, and the ground plane layer is placed in parallel to the radiating aperture at a predetermined distance.
The single fragmented aperture antenna as described above may also be placed in an array of multiple antenna elements. In an alternative embodiment, the fragmented aperture antennas configured in the array environment are allowed, through the optimization process, to physically touch neighboring antenna elements, thereby creating a connected array. To create the connected antenna array, a suitable antenna element is selected and then the spacing and size are chosen such that no grating lobes exist and that the required array gain is met. In the connected array, the individual antenna array elements may physically touch, so the embedded array behavior does not resemble the isolated antenna behavior. By allowing the individual antenna array elements to touch, the low frequency limit of operation is not set by the size of the isolated elements, but rather, it is set by the size of the array antenna.
Another embodiment of the invention realizes a reconfigurable aperture and achieves multiple fragmented aperture designs from a single aperture. The reconfigurable aperture is comprised of conducting elements and configurable switches that may be opened or closed to create a fragmented antenna. The switches may be configured to steer the emitted energy at some predetermined angle from broadside.
In yet another alternative embodiment, the switched aperture antenna may be constructed in a connected array such that a large configurable aperture is comprised of an array of identically smaller, reconfigurable elements. The switched fragmented aperture array structure is a connected array similar to the connected non-switched arrays as discussed above. Metal patches are connected by closed switches to form the antenna array. A separate feed patch feeds each antenna element of the array. In the switched fragmented aperture array, the antenna elements in the array may physically touch; hence, the embedded array behavior does not resemble the isolated antenna behavior. Different configurations of a configurable array can operate broadband for a particular set of beam widths and steering angles, and the configuration of each array element can be changed from different beam widths and steering angles.
Many antennas, methods, features, and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description.
REFERENCES:
patent: 4728805 (1988-03-01), Dempsey
patent: 5001493 (1991-03-01), Patin et al.
patent: 5262790 (1993-11-01), Russo
patent: 5719794 (1998-02-01), Altshuler et al.
patent: 5912645 (1999-06-01), Wight et al.
Harms Paul H.
Kesler Morris Philip
Maloney James Geoffrey
Smith Glenn Stanley
Georgia Tech Research Corporation
Le Hoang-anh
Nguyen Hoang
Thomas Kayden Horstemeyer & Risley LLP
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