Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-01-21
2001-11-06
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S762000
Reexamination Certificate
active
06313798
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
U.S. Pat. No. 5,734,350, issued Mar. 31, 1998, entitled MICROSTRIP WIDE BAND ANTENNA, is incorporated herein by reference.
U.S. patent application Ser. No. 09/155,831, filed Oct. 6, 1998 entitled MICROSTRIP WIDE BAND ANTENNA AND RADOME, is incorporated herein by reference.
U.S. Patent application Ser. No. 09/441,529, filed Nov. 16, 1999, entitled WIDE BAND ANTENNA HAVING UNITARY RADIATOR/GROUND PLANE, is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of microstrip antennas. More specifically, this invention relates to a microstrip antenna having a microstrip feed line trough that is integrally formed in the antenna's radiating element.
2. Description of the Related Art
The art provides small patch and microstrip antennas that are generally useful for their limited intended purposes. However, the need remains in the art for a patch antenna that is of simple construction and that provides wide bandwidth operation.
As a feature of the present invention, an antenna having a two-section radiating element is provided, the radiating element having a microstrip feedline trough formed therein.
Uniform rectangular guides having a centered rectangular ridge on one, or both, of its wide sides is known. For example, see the publication WAVEGUIDE HANDBOOK by N. Marcuvitz, 1986, published by Peter Peregrinus Ltd., London, UK.
SUMMARY OF THE INVENTION
This invention provides a new and unusual form of a patch antenna having a wide bandwidth when the antenna is compared to existing patch antennas of a similar physical size. Antennas in accordance with the present invention are of relatively simple construction, and include a microstrip trough structure that is formed within a metal-radiating patch element. In preferred embodiments, the microstrip trough is formed generally in the center of the radiating element so as to divide the radiating element into two generally identical radiating portions.
The bottom of the trough is positioned closely adjacent to a metal ground plane element, to thereby form a pseudo microstrip transmission line by which a feed input is applied to the antenna's two-portion radiating element. A first input feed probe, or a first input feed conductor, is electrically connected to the bottom of the trough, and a second input feed conductor is electrically connected to the ground plane element. For example, the center conductor of a coaxial cable transmission line is connected to the bottom of the trough, and the metal sheath of the coaxial cable is connected to the ground plane element.
In accordance with an embodiment of the invention, a folded or bent radiating element is provided whereby a narrow, linear, elongated, and generally U-shaped cross-section trough is formed by bending, or forming, a rectangular shaped metal (copper) radiating patch generally in its mid-portion, thus providing a first radiating element portion on one side of the trough, and a second radiating element portion on the other side of the trough. In a non-limiting embodiment of the invention, the two radiating element portions are of the same physical shape and size. For example, the two radiating element portions are rectangular or square in shape.
The bottom of the U-shaped trough is located closely adjacent and generally parallel to a metal (copper) ground plane element that underlies the two radiating element portions. The bottom of the trough operates as the antenna's relatively low impedance (50 ohm) microstrip feed line. Since the bottom of the trough is substantially closer to the ground plane element than are the two portions of the radiating element, a shorter feed probe than is traditionally used can be provided to electrically connect to the trough and then to the two radiating elements. This shortness property of the probe operates to control the impedance of the probe in order to provide a good impedance match between the antenna and its feed line. More specifically, this construction and arrangement operates to lower the inductance that is required for a good impedance match, thus allowing the use of existing and well-known commercially-available probe terminating connectors to provide for input feed to the antenna, rather than requiring the use of more complicated structures that are sometimes used to achieve a broad bandwidth patch antenna.
In accordance with a feature of the invention, an input feed network is provided comprising a probe feed, or an edge feed, into the metal microstrip line that includes the bottom of the above-described trough. This microstrip line or trough is integral with the two-portion radiating patch element, and this microstrip line is physically sized in width to be of a desired impedance; for example, 50 ohms. This construction and arrangement of the invention provides an efficient electrical transition from a transmission line, such as a coaxial cable into the antenna, further resulting in a structure that provides a broadband characteristic to the antenna as a whole, in particular to the primary resonant mode in which the antenna operates as a one-half wavelength patch antenna, resulting in a directional radiation pattern over a wide range of frequencies.
Antennas in accordance with the present invention operate in multiple resonant modes within the same physical antenna structure, with a smooth transition being provided between the various resonant modes, where the various modes comprise regions of radiation in particular patterns. The presence of these multiple modes give rise to an overall bandwidth of 50-percent or more, all of the modes being effectively impedance matched by the impedance matching trough construction and arrangement above described. As a result, antennas in accordance with the invention are impedance matched across an extremely large frequency range as compared to known patch antennas of similar physical size. Stated another way, antennas in accordance with the invention, exhibit multiple resonances, all of which are impedance matched to the input feed line.
These and other features and advantages of the present invention will be apparent to those of skill in the art upon reference to the following detailed description, which description makes reference to the drawing.
REFERENCES:
patent: 5155493 (1992-10-01), Thursby et al.
patent: 5734350 (1998-03-01), Deming et al.
Waveguide Handbook by N. Marcuvitz, 1986, pp. 399-402.
Bancroft Randy Cecil
Bateman Blaine Rexel
Uspenski Alexis
Centurion Wireless Technologies, Inc.
Clinger James
Hancock E. C.
Holland & Hart LLP
Sirr F. A.
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