Patent Grant
7889127
The present invention relates to antennas, antenna arrays and the like, and more particularly to wide angle impedance matching (WAIM) using metamaterials in a phased array antenna system.
Currently existing phased array antenna systems when scanned at wide elevation angles, such as past sixty degrees from an angle normal or perpendicular to the face of the array, experience severe reflections that can prevent detectable signals from being transmitted or received. Isotropic dielectric materials have been used for impedance matching of phased array antennas in attempts to improve at large scan angles but improvements have been limited.
In accordance with an embodiment of the present invention, a phased array antenna system may include a sheet of conductive material with a plurality of aperture antenna elements formed in the sheet of conductive material. Each of the plurality of aperture antenna elements is capable of sending and receiving electromagnetic energy. The phased array antenna system may also include a wide angle impedance match (WAIM) layer of material disposed over the plurality of aperture antenna elements formed in the sheet of conductive material. The WAIM layer of material includes a plurality of metamaterial particles. The plurality of metamaterial particles are selected and arranged to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation and all azimuthal angles.
In accordance with another embodiment of the present invention, a communications system may include a transceiver to transmit and receive electromagnetic signals and a tracking and scanning module coupled to the transceiver. A phased array antenna system may be coupled to the tracking and scanning module. The phased array antenna system may include a sheet of conductive material with a plurality of aperture antenna elements formed in the conductive sheet. Each of the plurality of aperture antenna elements may be capable of sending and receiving electromagnetic energy. The phased array antenna system may also include a wide angle impedance match (WAIM) layer of material disposed over the plurality of aperture antenna elements formed in the sheet of conductive material. The WAIM layer of material includes a plurality of metamaterial particles. The plurality of metamaterial particles are selected and arranged to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation.
In accordance with another embodiment of the present invention, a method for widening an angular scanning range of a phased array antenna system may include forming a wide angle impedance match (WAIM) layer of material. Forming the WAIM layer of material may include selecting and arranging a plurality of metamaterial particles to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation. The method may further include disposing the WAIM layer of material on a plurality of aperture antenna elements formed in a sheet of conductive material to form the phased array antenna system.
Other aspects and features of the present invention, as defined solely by the claims, will become apparent to those ordinarily skilled in the art upon review of the following non-limited detailed description of the invention in conjunction with the accompanying figures.
The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.
The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.
The aperture antenna elements 106 may be uniformly arranged to form the phased array antenna system 100. The aperture antenna elements 106 may be uniformly spaced from one another by a distance X and may have a predetermined opening size or diameter D. The distance X and opening size D will be a function of the operating parameters of the phased array antenna system 100, such as operating frequency and wavelength.
Each of the plurality of aperture antenna elements 106 may be fed by a waveguide 112. The aperture antenna elements 106 may be substantially circular in shape or may be formed in other shapes depending upon the desired radiation characteristics or other properties. Each of the waveguides 112 may have a cross-section corresponding to the shape of the aperture antenna elements 106. The waveguides 112 may couple the apertures elements 106 to a communications system (not shown in
One or more wide angle impedance match (WAIM) layers 114 and 116 of material may be disposed over the plurality of aperture antenna elements 106 formed in the sheet 104 of conductive material. Each of the WAIM layers 114 and 116 may include a plurality of metamaterial particles 120. The plurality of metamaterial particles 120 may be selected and arranged in a predetermined order or pattern substantially completely across each of the WAIM layers 114 and 116 similar to that illustrated in
Also referring to
As determined by the geometry, orientation, topology and physical parameters of the metamaterial elements, the metamaterials 120 (
The magnetic metamaterial particles 300 and the electric metamaterial particles 400 may be periodically arranged in a predetermined pattern or order relative to one another similar to that illustrated in
The metamaterial particles 300 and 400 may be arranged in different patterns in the plurality of WAIM layers 114 and 116 to provide different operating characteristics and wide angle scanning. The WAIM layers 114, 116 and 200 may also have varying thicknesses “T” as illustrated in
The selection and arrangement of the metamaterials 300 and 400 permit formation of an anisotropic WAIM layer of material wherein the material parameters may be different in different directions with the layer of material to provide optimum impedance matching and minimum return loss or reflection of the electromagnetic signal. In accordance with an aspect of the present invention, the selection and arrangement of the metamaterial particles 300 and 400 permit the permittivity in different directions (εx, εy, εz) with the WAIM layer and the permeability in different directions (μx, μy, μz) to be controlled to optimize the impedance match between the phased array antenna system 100 and the free space 122 and thereby to permit wider angle scanning of the phased array 100 of at least about 80 degrees than has been previously been achievable with other material layers, such as isotropic dielectric layers and the like. The geometry and dimensions of the elements in the WAIM layer 200 or layers 114 and 116 may also be varied to adjust or tune the material characteristics, such as permittivity and permeability. There is no limit to the number of metamaterial WAIM layers used to provide optimum matching for the antenna.
In accordance with one aspect of the present invention, the permittivities (εx, εy, εz) in different directions or orientation and the permeabilities (μx, μy, μz) in different directions or orientations in the WAIM layer may be determined by calculating the active element admittance that provide the minimum amount of reflected power or in other words, provides the maximum ratio of radiated (transmitted) power (PT) to input power (PI) at all scan angles theta (θ). This ratio may be expressed as equation 1.
PT/PI=(1−|Γ(θ|2)cos θ Eq. 1
The permittivity and permeability of each element array in the WAIM can be determined by quantitatively observing its response to an incoming plane wave of light at the design frequencies. The process is typically done using commercially available software that solve for electromagnetic scattering parameters, such as Ansoft HFSS (High Frequency Structure Solver) available from Ansoft of Pittsburgh, Pa., CST Microwave Studio available from Computer Simulation Technology of Framingham, Mass., or similar software. The electromagnetic scattering matrix retrieved from a simulation of the physical model of the element array is mathematically processed using an “inverse-problem” approach so as to extract the permittivity (electric) or permeability (magnetic) parameters that would elicit the response indicated in the scattering matrix of the element array. This process can also be done experimentally.
The communication system 500 may also include a tracking and scanning module 514 to control operation of the phased array antenna elements for scanning the radiation beam 508. The tracking and scanning module 514 may control phase shifters associated with feed waveguides (not shown in
The communications system 500 may also include a transceiver 516 to generate communications signals for transmission by the phased array antenna system 502 to a remote station 518 or other object and to receive communications signals received by the phased array antenna system 502.
The flowcharts and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” and “includes” and/or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
This invention was made with Government support under HR0011-05-C-0068 awarded by DARPA. The government has certain rights in this invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3577147 | Hannan | May 1971 | A |
| 20040017322 | Bostwick et al. | Jan 2004 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20100073232 A1 | Mar 2010 | US |
