WO2019014673A1 - Wireless feed system for arrays - Google Patents

Abstract

A novel wireless feed system is described which employs a plasmonic surface that is excited by one or more antennas. The plasmonic surface produces replicated currents within a plurality of cell elements that are closely-spaced electrically, e.g., compared to an operational wavelength. The cell elements are preferably substantially fractal in shape for at least a portion of their geometry, and at least a first iteration of a motif on that portion. Such a plasmonic surface may be a single sheet or a looped manifold "shell." The cells of such a plasmonic surface act to deliver radiation, or conversely, receive radiation-without the use of direct electrical connections-due to the evanescent surface wave effect, r plasmonic transmission. This delivered radiation may accordingly be near-field coupled to an adjacent antenna, antenna array, or another plasmonic surface used as an antenna array.

Description

WIRELESS FEED SYSTEM FOR ARRAYS CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims priority to U.S. provisional patent application 62/532,615 entitled "Wireless Feed System for Arrays," filed July 14, 2017; the entire content of the noted provisional application is incorporated herein by reference.

BACKGROUND

For more than 100 years, arrays of antennas have been utilized to provide useful approximations to larger continuous apertures, whose size weight and overall form factor may previously have prevented their usage. Antenna arrays are thus integral part of modern radio-wave-based communication.

A typical implementation of an antenna array is a plurality of spaced-apart, usually evenly spaced, antenna elements each of which is attached by a feed system which not unlike a tree branch feeds back to a central point in this case a feed point. Such feed systems incorporate a significantly large amount of electrical length and thereby introduce insertion loss, which aggravates the very objective of the antenna array, which is usually to increase the effective radiated power of the antenna array.

SUMMARY

An aspect of the present disclosure is directed to apparatus and techniques of feeding electromagnetic energy or power to elements in an antenna array in which a direct-coupled feed system is undesirable, unnecessary, or inappropriate. Embodiments of the present disclosure provide systems, apparatus, and/or techniques that provide for desired transfer of radiation to and between elements of antenna arrays by employing close-packed arrangements of resonators as plasmonic surfaces. An exemplary embodiment of the present disclosure provides a novel wireless feed system that employs a plasmonic surface— preferably, a fractal plasmonic surface (FPS)— that is excited by one or a small number of antennas ("exciting" or "excitation" antennas). The plasmonic surface produces replicated currents within a plurality of "cell" elements that are closely-spaced electrically, e.g., compared to an operational wavelength. The cell elements are preferably substantially fractal in shape for at least a portion of their geometry, and at least a first iteration of a motif on that portion. Such a plasmonic surface may be a single sheet or a looped manifold "shell." The cells of such a plasmonic surface act to deliver radiation, or conversely, receive radiation— without the use of direct electrical connections— due to the evanescent surface wave effect (plasmonic transmission). This delivered radiation may accordingly be near-field coupled to an adjacent antenna, antenna array, or another FPS surface used as an antenna array. These antennas or plasmonic surfaces may be configured as modules of a larger system.

An exemplary embodiment of the present disclosure provides a novel system for feeding antenna elements, or systems that perform as antenna elements, without the use of direct electrically attached feeds, such as wires, conductive traces, and the like.

These, as well as other components, steps, features, objects, benefits, and advantages, will now become clear from a review of the following detailed description of illustrative embodiments, the accompanying drawings, and the claims.

BRIEF DESCRIPTION OF D RAWINGS

The drawings are of illustrative embodiments. They do not illustrate all embodiments. Other embodiments may be used in addition or instead. Details that may be apparent or unnecessary may be omitted to save space or for more effective illustration. Some embodiments may be practiced with additional components or steps and/or without all of the components or steps that are illustrated. When the same numeral appears in different drawings, it refers to the same or like components or steps. FIG. 1 depicts an example of a wireless feed system for an antenna array, according to a preferred embodiment of the present disclosure.

FIG. 2 depicts an example of a fractal plasmonic surface having certain fractal resonator shapes, according to a further embodiment of the present disclosure.

FIG. 3 depicts a portion of a fractal plasmonic surface that includes repeated conductive traces that are configured in an exemplary fractal -like shape, in accordance with exemplary embodiments of the present disclosure.

FIG. 4 depicts a further example of fractal cells used for a fractal plasmonic surface, according to embodiments of the present disclosure.

FIG. 5 illustrates how a fractal plasmonic surface provides robustness or anti- fragility under conditions where some fractal cells are damaged or otherwise inoperative.

D ETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments are now described. Other embodiments may be used in addition or instead. Details that may be apparent or unnecessary may be omitted to save space or for a more effective presentation. Some embodiments may be practiced with additional components or steps and/or without all of the components or steps that are described.

An aspect of the present disclosure provides apparatus and techniques of feeding electromagnetic energy or power to elements in an antenna array in which a direct-coupled feed system is undesirable, unnecessary, or inappropriate. The transmission of electromagnetic waves via the feed system by direct electrical connection (galvanic connection) is thus replaced by a plurality of close-spaced resonators. The resonators act as cells of a plasmonic surface. These resonators preferably include, but are not limited to, fractal resonators, that is, self-similar structures with at least two iterations of structural magnification. For cases where such a plasmonic surface includes fractal resonators, the surface may be referred to as a fractal plasmonic surface ("FPS"). In exemplary embodiments, such a plasmonic surface, e.g., a FPS, can be utilized as a low-loss feed system for antenna elements in an antenna array. Because feed systems are an integral part of antenna arrays, the ability provided by embodiments of the present disclosure to reduce or remove this insertion loss represents a key improvement for antenna arrays relative to prior techniques and apparatus.

Such plasmonic surfaces work by the following mechanism. Resonator cells, for example fractal resonator cells, are excited by an existing resonator or antenna, and then the resonators themselves radiate. Their radiation is predominantly through an evanescent wave which propagates over a very small distance, electrically, to one or more adjacent resonators. In turn, each adjacent resonator is excited by this evanescent wave propagation, thus distributing the RF energy over a variety of resonators, or by separation control of nearby resonators, forcing the electromagnetic wave radiation to proceed as an evanescent-wave transmission line.

A novel wireless feed system according to the present disclosure employs a plasmonic surface— preferably, a fractal plasmonic surface (FPS)— that is excited by one or a small number of antennas ("exciting" or "excitation" antennas). The plasmonic surface then produces replicated currents within a plurality of "cell" elements that are closely-spaced electrically, e.g., compared to an operational wavelength. The cell elements are preferably substantially fractal in shape for at least a portion of their geometry, and at least a first iteration of a motif on that portion. Such a plasmonic surface may be a single sheet or a looped manifold "shell."

The cells of such a plasmonic surface act to deliver radiation, or conversely, receive radiation— without the use of direct electrical connections— due to the evanescent surface wave effect (plasmonic transmission). This delivered radiation may accordingly be near-field coupled to an adjacent antenna, antenna array, or another FPS surface used as or in an antenna array. These antennas or plasmonic surfaces may be configured as modules of a larger system. For example, as shown in FIG. 1, they may be placed as "cards" within the larger system to make a larger, antenna, functioning array, without any direct connection of feedlines, splitters, and so on. This novel arrangement of resonators acts as a transmission line which has no direct attachment of the radiators (cells) by any direct physical connection of conductors or conductive material (e.g., galvanic connection). The radiators or cells are indeed separated and distinct from each other with no direct connection of conductors between them. This modality of electromagnetic transmission avoids the significant amount of insertion loss that a direct feed to galvanic system would have otherwise. In addition, because the resonators are close-packed in a plurality, a malfunction or loss of one resonator does not affect large electromagnetic wave transmission along to or by the others.

FIG. 1 depicts an example of a wireless feed system 100 for an antenna array, according to a preferred embodiment of the present disclosure. Feed system 100 includes multiple plasmonic surfaces configured as fractal plasmonic surfaces (FPS) 102(l)-(2). In preferred embodiments, FPS 102(l)-(2) are connected to each other; any suitable connection structure, adhesive, or fastener may be used to connect the FPS. Each FPS 102(l)-(2) includes a number of resonator cells, e.g., fractal cells 104. The resonator cells 104 can be conductive traces, e.g., copper, silver, etc., in fractal shapes or outlines which are disposed on a substrate, e.g., polyimide with or without composite reinforcement, FR4, or the like. System 100 is excited by an external excitation antenna 106 such as a dipole, as shown. More than one excitation antenna may be used, and each is not necessarily a dipole; any suitable antenna may be used as an excitation antenna. Representative frequencies of operation of system 100 can include, but are not limited to, those over a range of 500 MHz to 5.5 GHz, though others may of course be realized. Operation at other frequencies, including for example those of visible light, infrared, ultraviolet, and as well as microwave EM radiation, e.g., K, Ka, X-bands, etc. may be realized, e.g., by appropriate scaling of dimensions and selection of shape of the resonator elements.

Each FPS 102(l)-(2) supports electromagnetic wave transmission across its surface area. As shown in FIG. 1, if a separate antenna or similar fractal plasmonic surface, e.g., 102(2), is aligned with say a row or column of such resonators on a first FPS, e.g., 102(1), these resonators will excite that second fractal plasmonic surface 102(2) thereby transmitting the electromagnetic wave from the first FPS 102(1) to the second FPS 102(2) without any direct physical connection of conductors between the FPS themselves. By incorporating a plurality of such plasmonic surfaces (e.g., FPS) many different antennas and antenna arrays can be realized— potentially for many different application— which are all fed by the first fractal plasmonic surface 102(1). Thus, in a very real sense, the feed system 100 is a wireless system as it incorporates no direct galvanic connections by feed wires, or other direct physical connection by conductive paths, between separate FPS or between the resonators of a FPS.

With continued reference to FIG. 1, it will be understood that system 100 can provide for near-field coupling of a plasmonic surface, e.g., FPS 102(1), to other components of an antenna or array. This radiation initially provided by the excitation antenna may accordingly be near-field coupled via the plasmonic surface to an adjacent antenna, antenna array, or another plasmonic surface used as or in an antenna array. Thus, while FIG. 1 designates 102(2) as a "Card" or "Antenna module" with multiple fractal cells, a person of ordinary skill in the art will appreciate that 102(2) can also refer to a single antenna or other component, which may be used alone or as part of an array.

FIG. 2 depicts an example of a fractal plasmonic surface 200 having certain fractal resonator shapes, according to a further embodiment of the present disclosure. FPS 200 includes a substrate 202 acting as a support surface for a number of fractal resonator cells 204. Fractal resonator cells 204 are hexagonal in shape and may be modeled after or based on a Sierpinski hexagon or orthogonal projection of a Cantor cube or a hexaflake.

FIG. 3 depicts an exemplary embodiment of a FPS 300 (only a portion is shown) that includes repeated conductive traces that are configured in a fractal shape 302 (the individual closed traces). For exemplary embodiments, each resonator shape 302 may be, e.g., about 1 cm on a side. The conductive trace is preferably made of copper. A single resonator is shown offset in white for the sake of illustration. Of course, it will be understood that while exemplary fractal shapes are shown in FIG. 3, the present disclosure is not limited to such and any other suitable shapes, including fractal and fractal-like shapes (including generator motifs) may be used in accordance with the present disclosure. The dimensions and type of fractal shape can be the same for each FPS, can vary between each FPS, and indeed can vary within an individual FPS. This variation (e.g., scaling of the same fractal shape) can afford increased bandwidth and/directivity for some applications.

Examples of suitable fractal shapes for use in one or more resonators or resonator arrays of a FPS can include, but are not limited to, fractal shapes described in one or more of the following patents, owned by the assignee of the present disclosure, the entire contents of all of which are incorporated herein by reference: U.S. Pat. No. 6,452,553; U.S. Pat. No. 6,104,349; U.S. Pat. No. 6,140,975; U.S. Pat. No. 7,145,513; U.S. Pat. No. 7,256,751; U.S. Pat. No. 6,127,977; U.S. Pat. No. 6,476,766; U.S. Pat. No. 7,019,695; U.S. Pat. No. 7,215,290; U.S. Pat. No. 6,445,352; U.S. Pat. No. 7,126,537; U.S. Pat. No. 7,190,318; U.S. Pat. No. 6,985,122; U.S. Pat. No. 7,345,642; and, U.S. Pat. No. 7,456,799. Other suitable fractal or fractal-like shapes for a resonator or resonant structures used for a FPS can include any of the following: a Koch fractal, a Minkowski fractal, a Cantor fractal, a torn square fractal, a Mandelbrot, a Caley tree fractal, a monkey's swing fractal, a Sierpinski gasket, and a Julia fractal, a contour set fractal, a Sierpinski triangle fractal, a Menger sponge fractal, a dragon curve fractal, a space-filling curve fractal, a Koch curve fractal, a Lypanov fractal, and a Kleinian group fractal.

FIG. 4 depicts an example of fractal resonators used for a fractal plasmonic surface (FPS) 400, according to a further embodiment of the present disclosure. The FPS 402 includes close packed arrangements of resonators having fractal shapes (e.g., "fractal cells") as denoted by 410 and 420. The FPS 402 may be part of a larger surface or area 404; in some embodiments that area 404 can include a resistive edge, layer, or boundary that is applied to or adjacent to the FPS. The individual fractal cells are separated from the adjacent fractal cells but are sufficiently close to one another (e.g., less than 1/20 wavelength, less than 1/10 wavelength) so that a surface (plasmonic) wave causes near replication of current present in one fractal cell in an adjacent fractal cell. While preferred fractal shapes are shown in FIG. 4 as being hexagonal or snowflake-like, any suitable fractal shape (e.g., deterministic) can be used and such a fractal may have two or more iterations. The fractal cells may lie on a flat or curved sheet or layer and be composed in layers for wide bandwidth or multibandwidth transmission. Each layer holding a FPS can utilize fractal cells of different size and shape than those of another layer.

FIG. 5 illustrates the robustness or anti-fragility presented by a FPS 500 under conditions where some fractal cells are damaged or otherwise inoperative. As show, FPS 500 has a close-packed arrangement of fractal cells, indicated by circles 502. The close-packed arrangement provides many paths by which energy may be transferred from one area of the FPS to another, even in the presence of damaged, obstructed, or otherwise inoperative fractal cells 504 (represented by the squares shown in the drawing).

Exemplary embodiments:

1. A wireless feed system for an antenna array, the system comprising: a first plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy; and an excitation antenna configured to transmit RF energy at an operational wavelength to the first plasmonic surface.

2. The wireless feed system of claim 1, further comprising a second plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy, wherein the second plasmonic surface is positioned sufficiently close to the first plasmonic surface such that RF energy transfers from the first plasmonic surface to the second plasmonic surface in operation when the excitation antenna transmits the RF energy to the first plasmonic surface.

3. The wireless feed system of claim 1, wherein the first plasmonic surface comprises a fractal plasmonic surface. 4. The wireless feed system of claim 2, wherein the second plasmonic surface comprises a fractal plasmonic surface.

5. The wireless feed system of claim 2, wherein the second plasmonic surface is connected to the first plasmonic surface.

6. The wireless feed system of claim 5, wherein the second plasmonic surface includes one or more protrusions and the first plasmonic surface includes one or more receiving slots adapted to receive the one or more protrusions for holding the second plasmonic surface in place relative to the first plasmonic surface.

7. The wireless feed system of claim 5, wherein the first plasmonic surface includes one or more protrusions and the second plasmonic surface includes one or more receiving slots adapted to receive the one or more protrusions for holding the first plasmonic surface in place relative to the second plasmonic surface.

8. The wireless feed system of claim 2, further comprising a third plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy; wherein the third plasmonic surface is positioned sufficiently close to the first plasmonic surface or the second plasmonic surface such that RF energy transfers from the first plasmonic surface or the second plasmonic surface, respectively, to the third plasmonic surface in operation when the excitation antenna transmits the RF energy to the first plasmonic surface.

9. The wireless feed system of claim 1, wherein the first plasmonic surface is configured to plasmonically transfer the RF energy to a separate antenna.

10. The wireless feed system of claim 1, wherein the first plasmonic surface is configured to plasmonically transfer the RF energy to a separate antenna array.

Accordingly, it will be appreciated that embodiments of the present disclosure can provide one or more significant benefits relative to the prior art. For example, an exemplary embodiment of the present disclosure provides a novel system for feeding antenna elements, or systems that perform as antenna elements, without the use of direct electrically attached feeds, such as wires, conductive traces, and the like.

Unless otherwise indicated, various features that have been discussed herein can be implemented with or controlled by a specially-configured computer system specifically configured to perform the functions that have been described herein for the component. For example, phase control of the elements of an array, pattern synthesis, and/or lobe generation can be implemented or controlled by a computer system. Each computer system includes one or more processors, tangible memories (e.g., random access memories (RAMs), read-only memories (ROMs), and/or programmable read only memories (PROMS)), tangible storage devices (e.g., hard disk drives, CD/DVD drives, and/or flash memories), system buses, video processing components, network communication components, input/output ports, and/or user interface devices (e.g., keyboards, pointing devices, displays, microphones, sound reproduction systems, and/or touch screens). Each computer system may include software (e.g., one or more operating systems, device drivers, application programs, and/or communication programs). When software is included, the software includes programming instructions and may include associated data and libraries. When included, the programming instructions are configured to implement one or more algorithms that implement one or more of the functions of the computer system, as recited herein. The description of each function that is performed by each computer system also constitutes a description of the algorithm(s) that performs that function.

The software may be stored on or in one or more non-transitory, tangible storage devices, such as one or more hard disk drives, CDs, DVDs, and/or flash memories. The software may be in source code and/or object code format. Associated data may be stored in any type of volatile and/or non-volatile memory. The software may be loaded into a non-transitory memory and executed by one or more processors.

The components, steps, features, objects, benefits, and advantages that have been discussed are merely illustrative. None of them, or the discussions relating to them, are intended to limit the scope of protection in any way. Numerous other embodiments are also contemplated. These include embodiments that have fewer, additional, and/or different components, steps, features, objects, benefits, and/or advantages. These also include embodiments in which the components and/or steps are arranged and/or ordered differently.

For example, while preferred configurations of the resonators or cells of a plasmonic surface have been described as being fractal or fractal-like, non-fractal resonators may be used within the scope of the present disclosure, such that the collection of resonators supports plasmonic (evanescent-wave) propagation. The resonators can be repeated patterns of suitable conductive traces. These conductive traces can be closed geometric shapes, e.g., rings, loops, closed fractals, etc. The resonator(s) can be self-similar to at least second iteration, and can include a higher number of iterations, i.e., be of higher order. The resonators can include split-ring shapes, for some embodiments. The resonant structures are not required to be closed shapes, however, and open shapes can be used for such. In exemplary embodiments, the resonators are relatively closely packed, e.g., with adjacent separations less than about 1/5 wavelength (or less) at lowest operational frequency. Other examples of separate distances between adjacent resonators or resonant structures can include any value between 1/5 wavelength to 1/20+ wavelength, inclusive, at lowest operational frequency (i.e., longest operational wavelength).

Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain.

All articles, patents, patent applications, and other publications that have been cited in this disclosure are incorporated herein by reference.

The phrase "means for" when used in a claim is intended to and should be interpreted to embrace the corresponding structures and materials that have been described and their equivalents. Similarly, the phrase "step for" when used in a claim is intended to and should be interpreted to embrace the corresponding acts that have been described and their equivalents. The absence of these phrases from a claim means that the claim is not intended to and should not be interpreted to be limited to these corresponding structures, materials, or acts, or to their equivalents.

The scope of protection is limited solely by the claims that now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows, except where specific meanings have been set forth, and to encompass all structural and functional equivalents.

Relational terms such as "first" and "second" and the like may be used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between them. The terms "comprises," "comprising," and any other variation thereof when used in connection with a list of elements in the specification or claims are intended to indicate that the list is not exclusive and that other elements may be included. Similarly, an element proceeded by an "a" or an "an" does not, without further constraints, preclude the existence of additional elements of the identical type.

None of the claims are intended to embrace subject matter that fails to satisfy the requirement of Sections 101, 102, or 103 of the Patent Act, nor should they be interpreted in such a way. Any unintended coverage of such subject matter is hereby disclaimed. Except as just stated in this paragraph, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims.

The abstract is provided to help the reader quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, various features in the foregoing detailed description are grouped together in various embodiments to streamline the disclosure. This method of disclosure should not be interpreted as requiring claimed embodiments to require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as separately claimed subject matter.

Claims

CLAIMS What is claimed is:

1. A wireless feed system for an antenna array, the system comprising: a first plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy; and

an excitation antenna configured to transmit RF energy at an operational wavelength to the first plasmonic surface.

2. The wireless feed system of claim 1, further comprising a second plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy, wherein the second plasmonic surface is positioned sufficiently close to the first plasmonic surface such that RF energy transfers from the first plasmonic surface to the second plasmonic surface in operation when the excitation antenna transmits the RF energy to the first plasmonic surface.

3. The wireless feed system of claim 1, wherein the first plasmonic surface comprises a fractal plasmonic surface.

4. The wireless feed system of claim 2, wherein the second plasmonic surface comprises a fractal plasmonic surface.

5. The wireless feed system of claim 2, wherein the second plasmonic surface is connected to the first plasmonic surface.

6. The wireless feed system of claim 5, wherein the second plasmonic surface includes one or more protrusions and the first plasmonic surface includes one or more receiving slots adapted to receive the one or more protrusions for holding the second plasmonic surface in place relative to the first plasmonic surface.

7. The wireless feed system of claim 5, wherein the first plasmonic surface includes one or more protrusions and the second plasmonic surface includes one or more receiving slots adapted to receive the one or more protrusions for holding the first plasmonic surface in place relative to the second plasmonic surface.

8. The wireless feed system of claim 2, further comprising a third plasmonic surface having a support surface and a plurality of resonator cells disposed on the support surface, wherein the plurality of resonators cells are arranged on the support surface in close proximity such that the cells are operative to plasmonically transfer RF energy; wherein the third plasmonic surface is positioned sufficiently close to the first plasmonic surface or the second plasmonic surface such that RF energy transfers from the first plasmonic surface or the second plasmonic surface, respectively, to the third plasmonic surface in operation when the excitation antenna transmits the RF energy to the first plasmonic surface.

9. The wireless feed system of claim 1, wherein the first plasmonic surface is configured to plasmonically transfer the RF energy to a separate antenna.

10. The wireless feed system of claim 1, wherein the first plasmonic surface is configured to plasmonically transfer the RF energy to a separate antenna array.