Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1998-12-16
2001-06-12
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000, C343S872000
Reexamination Certificate
active
06246368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to antennas and to antenna/radome combinations for receiving and transmitting Radio Frequency (RF) signals. More particularly, the present invention relates to a small RF microstrip antenna and an antenna/radome having a relatively low or thin height profile, and to a radome that is forms an integral support element of the antenna. While not necessarily limited thereto, the present invention is particularly useful for the exchange of high frequency RF signals at relatively low power.
2. Description of the Related Art
Several varieties of Radio Frequency (RF) antennas have evolved in the past. For instance, U.S. Pat. No. 5,444,453 by Lalezari describes a parallel plate, inverted, microstrip type of antenna using air as a dielectric, and intended to operate in the 10 to 40 GigaHertz range. A relatively large dielectric plate (i.e., 1×1 to 2×2 inch square plates, or one to two inch diameter circular plates) operates to physically support a smaller metallic radiator patch that is centrally located over a metallic ground plane member, the ground plane member being about the same size as the dielectric plate. A number of support posts of substantially the same height operate to maintain a uniform 0.1 mm to 1.0 mm spacing, between the dielectric plate and the ground plane member.
In addition, U.S. Pat. No. 5,442,366 to Sanford describes a raised patch antenna structure for the circular polarized transmission and reception of signals, wherein a raised patch antenna element is provided at the top surface of a hollow cube-shaped housing. The flat bottom surface of the cube comprises a feed base portion having phasing means and power dividing means for the four walls of the cube. Each cube wall contains a feed-leg line, whereby the two pairs of opposite sides of the raised patch antenna element are feed with balanced signals of equal amplitude that are 180-degrees out of phase. Each of the four feed-legs includes an impedance matching means.
Additional examples of microstrip antennas include U.S. Pat. Nos. 3,938,161 to Sanford and 5.210,542 to Pett et al.
Additional examples of microstrip antennas include U.S. Pat. Nos. 3,938,161 to Sanford and 5,210,542 to Pett et al.
In the prior art, a radome has been provided to cover an antenna device. U.S. Pat. No. 5,355,142 to Marshall et al is an example.
While prior antennas/radomes, as above exemplified, are generally satisfactory for their limited intended purposes, the need remains in the art for a small, low profile, microstrip antenna, and for such an antenna/radome combination device, that is aesthetically pleasing to the human eye, whose physical shape generally disappears to human view when the antenna is mounted in a use environment, and which antenna is of a minimum part construction and arrangement that provides exceptional radiation/reception performance improvements.
SUMMARY OF THE INVENTION
The present invention finds utility in a wide variety of signal transmission applications, and it is especially useful for the specialized needs of wireless communication equipment, such as those operating in the unlicensed (U.S.A) 2.4 to 2.4835 Giga Hertz (GH) frequency band.
The present invention provides a physically small antenna, for example, a square 4.755-inch by 4.755-inch box-like structure that is 0.66-inch thick, or a rectangular 10-inch by 8-inch box-like structure that is ⅞-inch thick, i.e., an antenna that is generally the size of the well-known domestic smoke detectors. Preferably, an antenna in accordance with this invention is provided in a conformal design whose base fits relatively flush against a flat support structure, such as a vertically extending wall, or against a curved support structure, such as an antenna mast
This invention advantageously utilizes a metal planar, or curved active element, also sometimes called a radiating element or a radiating patch, wherein the surface of the radiating element is oriented at an angle (i.e., the radiating element is tilted) relative to an adjacent surface of a metal planar or curved ground plane element. The angled or tilted construction and arrangement of the present invention operates to provide an aesthetically pleasing antenna whose physical shape almost disappears to human view in most environments, and yet the construction and arrangement of the present invention offers exceptional radiation/reception performance improvements, including a reduction in the antenna's feed inductance.
A general object of the present invention is to provide a microstrip antenna having a metallic ground plane element of a first shape and a first physical size, a metallic radiating element of a second shape that is generally identical to the above-mentioned first shape and of a second physical size that is smaller, or at least no larger than, the above mentioned first physical size of the ground plane element, with mounting means operating to position the radiating element at a fixed position and generally centered over the ground plane element, the mounting means operating to mount the radiating element away from the ground plane element to define a dielectric space between the radiating element and the ground plane element, and the mounting means additionally operating to mount the radiating element in an inclined attitude relative to the ground plane element and wherein a signal feed means extends into this dielectric space, the signal feed means including metallic electrical conductor means that is fixed to a feed point on a surface of the radiating element that faces the ground plane element.
As a feature of this invention, the geometric shape of the radiating element and the ground plane element are both selected from the group flat-planar shape or partial-cylinder shape.
As an additional feature of this invention, the antenna may include a radome covering the assembly that consists of the ground plane element and the radiating element.
In an embodiment of the invention a two-piece radome is provided wherein a first portion of the radome supports the antenna's inclined radiating element, the antenna's feed cable, and the antenna's ground plane element, wherein edge portions of a second portion of the radome snap-fit to the first portion, and wherein this second radome portion includes internal tabs that engage the ground plane member to assist in maintaining the ground plane member nonmovable in position.
As an additional feature of this invention, the mounting means includes the use of a metallic electrical feed conductor to physically support the radiating element adjacent to one of its edges, while using first and second dielectric-material and physically spaced support posts of generally equal length to support an opposite edge of the radiating element.
Those having normal skill in the art will recognize the foregoing and other objects, features, advantages and applications of the present invention from the following more detailed description of the preferred embodiments as illustrated in the accompanying drawings.
REFERENCES:
patent: 3938161 (1976-02-01), Sanford
patent: 4123758 (1978-10-01), Shibano et al.
patent: 4653889 (1987-03-01), Bizouard et al.
patent: 5155493 (1992-10-01), Thursby et al.
patent: 5166697 (1992-11-01), Viladevall et al.
patent: 5210542 (1993-05-01), Pett et al.
patent: 5355142 (1994-10-01), Marshall et al.
patent: 5438697 (1995-08-01), Fowler et al.
patent: 5442366 (1995-08-01), Sanford
patent: 5444453 (1995-08-01), Lalezari
patent: 5734350 (1998-03-01), Deming et al.
patent: 5757327 (1998-05-01), Yajima et al.
patent: 5977710 (1999-11-01), Kuramoto et al.
patent: 0278069 (1988-08-01), None
patent: 2553584 (1983-10-01), None
patent: 09083242 (1997-03-01), None
Craig Dax
Deming Douglas R B
Munson Robert E
Negler Joseph T
Centurion Wireless Technologies, Inc.
Hancock E. C.
Ho Tan
Holland & Hart LLP
Sirr F. A.
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