Communications: radio wave antennas – Antennas – Active sleeve surrounds feed line
Reexamination Certificate
1999-11-05
2001-03-13
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Active sleeve surrounds feed line
C343S785000, C343S787000, C343S890000
Reexamination Certificate
active
06201509
ABSTRACT:
BACKGROUND
1. The Field of the Invention
This invention relates generally to antennas, filters and transmission lines. More specifically, the invention relates to a new configuration of a continuous transverse stub element array structure which is formed in a coaxial arrangement to provide superior omnidirectional performance at microwave, millimeter, and quasi-optical wavelengths.
2. The State of the Art
The state of the art of antennas, antenna arrays, parallel plate waveguides, filters and couplers beginning at microwave frequencies is characterized, for example, by several types of more conventional designs of mono-poles or dipoles, slotted waveguide arrays, printed patch arrays, and reflector and lens systems as mobile or base station terminal antennas. These designs are used to build high gain antenna arrays, adaptive arrays, phased arrays and smart antennas. Furthermore, when moving into frequencies which are greater than 20 GHz and commonly known as millimeter wave and quasi-optical frequencies, antennas and filters suffer from relatively low Q factors due to high dissipative conductor and dielectric losses, interconnect losses, and from relatively difficult fabrication due to dimensional tolerances. Accordingly, antenna and filter designs have moved to more advantageous configurations which are known as continuous transverse stub element array structures which can be radiating (antenna) or reactive (filter).
The known configurations and methods of fabricating these continuous transverse stub element array structures are generally taught, for example, in U.S. Pat. Nos. 5,266,961, 5,412,394, 5,583,524, 5,604,505 and 5,771,567 to list but a few. In essence, these patents teach that a continuous transverse stub element residing in one or both conductive plates of a parallel plate waveguide is employed as a coupling, reactive, or radiating element in coupler, filter and antenna designs. These patents contributed to the parallel-plate continuous transverse array designs that are characterized by pencil beam patterns.
In the planar-type prior art, a typical continuous transverse stub element array structure will include a dielectric element forming a plane which has a second dielectric element which extends transversely to the plane to form a stub. A first conductive element is disposed coextensive with the dielectric element forming the plane, and a second conductive element is disposed along a surface of the second dielectric stub element.
FIG. 1
is provided as a close-up illustration of the prior art which shows a typical dielectric plane
10
and stub element
12
.
FIG. 2
is provided to show a perspective view of an array of stub elements
14
in a planar array
16
.
It is taught in the prior art that purely-reactive stub elements are realized through conductively terminating (a short circuit) or by narrowing (an open circuit) the terminus of the stub element. Radiating elements are formed when stub elements of moderate height are opened to free space. Precise control of stub element coupling or excitation by way of coupling of parallel plate waveguide modes is accomplished through variation of longitudinal stub element length, stub element height, parallel plate separation, and the properties of the parallel plate and the stub element media.
The prior art is also characterized by teaching that continuous transverse stub elements can be arrayed to form planar apertures and structures of arbitrary area which are comprised of a linear array of continuous transverse stub elements fed by a conventional line-source or sources.
The prior art teaches that the transverse stub elements are varied by modifying their height, width, length, and cross section. Other cited variations include changing the number of stub elements, and adding additional structures to the basic stub element. However, these arrays structure fail to provide a coaxial arrangement for a filter or antenna array system, or any means of conveniently providing a signal feed thereto.
It would be an advantage over the prior art to provide a different continuous transverse stub element array design which can provide a high Q-factor filter and a low cost antenna array with two-dimensional beam steering capability. It would be another advantage to provide omnidirectional capabilities at microwave, millimeter wave and quasi-optical wavelengths which would permit construction of a small and mobile array design. It would be a further advantage to provide a large beam scan width in a new continuous transverse stub element array design which provided low loss and had improved impedance matching.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and low cost configuration for a continuous transverse stub element array structure for both antenna array and filter designs.
It is another object to provide the new continuous transverse stub element antenna array which is omnidirectional at millimeter frequencies.
It is another object to provide the new continuous transverse stub element array which can accomplish two-dimensional steering using ferro-electric or liquid crystal materials.
It is another object to provide the new continuous transverse stub element array which utilizes thin film technology for the ferro-electric or liquid crystal materials to obtain uniform distribution for improved steering characteristics.
It is another object to provide the new continuous transverse stub element array structure which can operate over a broad frequency band.
It is another object to provide the new continuous transverse stub element array structure which can be used for base stations or mobile units.
It is another object to provide the new continuous transverse stub element array structure which is characterized by low losses and superior impedance matching.
It is another object to provide the new continuous transverse stub element array structure in the form of a coaxial design which provides improved tolerance for manufacturing errors.
The preferred embodiment of the present invention is a continuous transverse stub element array structure which forms a coaxial geometry formed from a plurality of cylindrical segments, wherein each of the cylindrical segments has a rim at a top end and a bottom end, wherein each rim extends transversely away from the cylindrical segment relative to a longitudinal axis thereof to thereby form a stub element, wherein the individual cylindrical transverse stub elements are aligned end-to-end to thereby form a cable structure which surrounds a central axis material. A linked series of these stubs form reactive or radiating elements for microwave, millimeter-wave, and quasi-optical wavelength filters and antennas. Purely reactive elements are formed by leaving the conductive coating on the terminus of the stub elements, whereas radiating elements are formed when stub elements of moderate radius are opened to free space. Where tunability of the array structure is desired, each of the plurality of cylindrical segments and the central axis material are coated with a conductive material which is ferro-electric or liquid crystal in nature. The individual stub elements are separated from each other by air gaps or an appropriate material.
In a first aspect of the invention, the ferro-electric or liquid crystal material is applied to the dielectric material of the individual stub elements using thin-film coating technologies.
In a second aspect of the invention, the thickness of the ferro-electric or the liquid crystal material is modified depending upon the desired characteristics of the array which are a function of the thickness of the ferro-electric or liquid crystal material, and the applied voltages.
In a third aspect of the invention, precise control of element coupling or excitation (amplitude and phase) via coupling of coaxial waveguide modes is accomplished through variation of longitudinal stub length, dish stub radius, interior and exterior radius of the coaxial structure, and the properties of the coaxial structure and stub filling media.
In a fourth
Iskander Magdy F.
Yun Zhengqing
Zhang Zhijun
Morriss Bateman O'Bryant & Compagni
Nguyen Hoang
University of Utah Research Foundation
Wong Don
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