Electromagnetically reflective surface device

Abstract

An electromagnetically reflective surface device including a substrate comprising a first major surface and a second major surface opposite the first major surface, the first major surface having a plurality of RIS elements, each RIS element of the plurality of RIS elements including an outer annular electrically conductive ring concentric with a center point, a plurality of curved segments disposed between the outer ring and the center point, a pair of electrically conductive patches between the plurality of curved segments and the center point, and a bar segment positioned between straight edges of the pair of patches.

Description

Attorney Docket No. SP25-051ELECTROMAGNETICALLY REFLECTIVE SURFACE DEVICECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit ofpriority under 35 U.S.C. § 119 ofU.S. Provisional Application No. 63 / 716457 filed on November 5, 2024 and U.S. Provisional Application No. 63 / 783524 filed on April 4, 2025, the contents of each of which are relied upon and incorporated herein by reference in their entireties.FIELD

[0002] The disclosure relates generally to structures for electromagnetic wave reflection, and more specifically, such as reconfigurable intelligent surface (RIS) devices for wireless communication systems (WCS), which can include fifth generation (5G) for later (6G) systems, 5G new-radio (5G-NR) systems, and / or a distributed communications system (DCS).BACKGROUND

[0003] The millimeter-wave (mm-wave) wavelength band is increasingly utilized for various communication applications, including 5G and 6G wireless communications. Communications employing a mm-wave wavelength band may provide benefits over previous communication technologies, such as greater communication speeds, reduced communication latencies, and greater capacity. For instance, mm-wave systems may operate in the 3 - 300 GHz frequency range. However, there are challenges transmitting and receiving wireless signals within mm-wave bands. For instance, propagation loss, penetration loss, and reflection loss may degrade the link corresponding budgets.

[0004] To compensate for these challenges, some systems may employ high gain phased array antennae. However, high gain phased array antennae may have their own drawbacks. For instance, the antennas may become saturated as the number of array elements increases. Moreover, high gain phased array antennas increase system loss and provide limited gains when employed in devices with limited space to accommodate the antennas, such as mobile devices.

[0005] More recently, electromagnetically reflective surface devices, such as reconfigurable intelligent surface (RIS) devices, have been proposed for improving propagation channelAtorney Docket No. SP25-051 conditions between base stations and mobile devices. Such electromagnetically reflective surface devices, also known as metasurfaces, may include the use of sub-wavelength resonators that may adaptively reflect, transmit, absorb, and / or convert the polarizations of incident waves with low power consumption. For instance, an electromagnetically reflective surface devices as a mm-wave device can be configured to control signal reflectance in a desired direction. Further, electromagnetically reflective surface device can generally be fabricated at low cost due to low-cost components.SUMMARY

[0006] In a first aspect, an electromagnetically reflective surface device is disclosed, comprising a substrate comprising a first major surface and a second major surface opposite the first major surface, the first major surface comprising a plurality of RIS elements, each RIS element of the plurality of RIS elements comprising: an electrically conductive annular outer ring concentric with a center point; a plurality of electrically conductive curved segments positioned between the annular outer ring and the center point and concentric with center point, the plurality of curved segments arranged angularly equidistant from each other; a pair of electrically conductive patches positioned between the plurality of curved segments, each patch of the pair of comprising a straight edge and a curved edge, the straight edges arranged parallel with and spaced apart from each other and the curved edges concentric with the center point; an electrically conductive bar segment positioned between and equidistant from the straight edges; and aground plane disposed on the second major surface.

[0007] In a second aspect, a width of the annular outer ring of the first aspect along a radial line extending outward from the center point may be in a range from about 0.2 mm to about 0.6 mm.

[0008] In a third aspect, the plurality of curved segments of the first through the second aspects comprises four curved segments.

[0009] In a fourth aspect, the four curved segments of the third aspect are arranged such that a midpoint of each curved segment of the four curved segment is positioned 90 degrees from an adjacent curved segment of the four curved segments.

[0010] In a fifth aspect, the ground plane of any one of the first through the fourth aspect comprises a metallic mesh.

[0011] In a sixth aspect, the substrate of any one of the first through the fifth aspects comprises a glass substrate.Atorney Docket No. SP25-051

[0012] In a seventh aspect, the glass substrate of the sixth aspect comprises a plurality of glass sheets arranged in a stack.

[0013] In an eighth aspect, the electromagnetically reflective surface device of any one of the first through the seventh aspects comprises a cover plate disposed over the plurality of RIS elements.

[0014] In a ninth aspect, the plurality of RIS elements of any one of the first aspect through the eighth aspects may be periodically arranged in a rectangular matrix.

[0015] In a tenth aspect, a dielectric constant of the substrate of any one of the first through the ninth aspects may be less than 10.

[0016] In an eleventh aspect, the bar segment of any one of the first aspect through the tenth aspects comprises a length in a direction parallel with the straight edges of the pair of patches, and the length of the bar segment is greater than an arc length of an outer edge of one curved segment of the plurality of curved segments.

[0017] In a twelfth aspect, the bar segment the bar segment of any one of the first aspect through the tenth aspects comprises a length in a direction parallel with the straight edges of the pair of patches, and a circumferential length of the annular outer ring is greater than four times the length of the bar segment.

[0018] In a thirteenth aspect, the bar segment of any one of the first aspect through the tenth aspects comprises a length in a direction parallel with the straight edges of the pair of patches, and a width of one patch of the pair of patches along a radial line extending outward from the center point and orthogonal to the straight edge of the one patch is greater than a width of the of the bar segment in a direction orthogonal to the length of the bar segment. The length of the bar segment may be equal to or less than a length of the straight edge.

[0019] In a fourteenth aspect, a radius of an outer edge of the annular outer ring of any one of the first aspect through the thirteenth aspects may be in a range from about 1.7 mm to about 3.7 mm.

[0020] In a fifteenth aspect, the curved edge of each patch of any one of the first aspect through the fourteenth aspects extends over an angular range p greater than 150 degrees but less than 180 degrees relative to the center point.

[0021] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.Atorney Docket No. SP25-051

[0022] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description explain principles and operation of the various embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is an edge cross-sectional view of an example electromagnetically reflective surface device comprising a plurality of RIS elements disposed on a substrate;

[0024] FIG. 2 is an edge cross-sectional view of another electromagnetically reflective surface device wherein the substrate comprises a plurality of layers;

[0025] FIG. 3 is a top view of an example electromagnetically reflective surface device comprising a plurality of circular RIS elements arranged in an 8x8 square array;

[0026] FIG. 4 is atop view of an example unit cell comprising an RIS element comprising a plurality of discrete electrically conductive components including an outer ring, a plurality of curved segments, a pair of patches, and a bar segment;

[0027] FIG. 5 is a top view of a ring component of the RIS element of FIG. 4, shown in isolation;

[0028] FIG. 6 is a top view of the curved segments of the RIS element of FIG. 4, shown together with the outer ring component of FIG. 5;

[0029] FIG. 7 is a top view of the RIS element of FIGS. 4-6 and depicting the bar segment disposed between the pair of patches;

[0030] FIG. 8 is a top view of the pair of patches of FIG. 7, in isolation, showing the radii of the curved edges of the patches;

[0031] FIG. 9 is a top view of one patch of the pair of patches shown in FIG. 8 and illustrating the angle subtended by the curved edge of the patch;

[0032] FIG. 10 is a top view of the pair of patches of FIG. 7 and various dimensional atributes thereof;

[0033] FIG. 11 is a botom view of substrate 16 shown in FIGS. 1-2 illustrating a mesh ground plane;Atorney Docket No. SP25-051

[0034] FIG. 12 is a plot of reflected phase as a function of the outer radius R1 for an electromagnetically reflective surface device comprising a 31x40 rectangular array of RIS elements as shown in FIG. 4;

[0035] FIGS. 13(a)-(f) are plots of reflected power in dB as a function of angle in degrees for the electromagnetically reflective surface device employed for FIG. 12. FIG. 13(a) shows this relationship for an 8 GHz signal. FIG. 13(b) shows the same for a 9 GHz signal. FIG. 13(c) shows this relationship for a 10 GHz signal. FIG. 13(d) shows it for an 11 GHz signal. FIG. 13(e) illustrates the scenario for a 12 GHz signal. FIG. 13(f) shows the data for a 13 GHz signal.DETAILED DESCRIPTION

[0036] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present disclosure. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present disclosure may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omited so as not to obscure the description of various principles of the present disclosure. Finally, wherever applicable, like reference numerals refer to like elements.

[0037] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0038] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including maters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.Atorney Docket No. SP25-051

[0039] As used herein, the singular forms “a,” “and,” and “the” include plural referents unless the context clear dictates otherwise. Thus, for example, reference to “an” element includes aspects having two or more such elements, unless the context clearly indicates otherwise.

[0040] For brevity, ranges of values disclosed herein, including compositional ranges or atribute (performance) ranges, or series of ranges, may be appended by the phrase “including all ranges and subranges therebetween,” which is to be interpreted as including whole number or decimal subranges as though explicitly presented. Thus, by way of example, a range between 6 and 8 (units omited) implicitly includes a subrange between 6.4 and 8, or a subrange between 6 and 7.2, or a subrange between 6 and 7, and so forth. Additionally, a series of ranges, such as “in a range from 6 to 11 or in a range from 6 to 8” implicitly includes a range from 7 to 10, or subranges therebetween, such as 7.2 to 10.4, as though explicitly presented, provided the range does not exceed the minimum or maximum endpoints of the explicitly presented range or series of ranges. Thus, for example, “in a range from 6 to 11 or in a range from 6 to 8” has as endpoints 6 and 11.

[0041] Reference throughout this disclosure to “in embodiments,” "one embodiment," "certain embodiments," "one or more embodiments" or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as” in embodiments,” "in one or more embodiments," "in certain embodiments," "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0042] An electromagnetically reflective surface device, e.g., RIS device, comprises a plurality of discrete electrically conductive elements (hereinafter RIS elements), disposed on a substrate, that act as electromagnetic wave scaterers. Typically, these conductive elements are arranged in a regular (e.g., periodic) array, for example a rectangular (e.g., square) array of rows and columns, although circular arrays may be formed as well. In embodiments, these conductive elements may be electronically reconfigurable to change the device properties, such as the surface reflectance, absorption, and / or permitivity. Reconfiguration of the elements may be controllable in real-time, allowing the electromagnetically reflective surface device to adapt to changing environmental conditions or system requirements. Beam forming can be achieved through the interference of scattered waves at a receiver. Such interference may beAtorney Docket No. SP25-051 dynamically alterable by the electromagnetically reflective surface device. Moreover, characteristics of the RIS elements may be configured to produce a desired outcome, for example a wave direction.

[0043] Functionality of the electromagnetically reflective surface device relies on unit cells that comprise the electrically conductive elements. Unit cells serve as phase distributors that enable the adjustment of outgoing (e.g., reflected) beams of electromagnetic energy. By choosing the dimensions (e.g., RIS element length, diameter) of the unit cells, the resonance frequency of the unit cell can be selected, facilitating phase tuning. The reflected phase can be calculated when the directions of the incident wave and the desired reflected wave are known.

[0044] RIS element structures with a wide bandwidth within the upper-mid frequency band are known. Such structures typically used low dielectric materials, e.g., organic substrates, with a dielectric constant less than 3 because a low dielectric constant can help obtain a wider bandwidth. However, such organic substrates with low dielectric constant also exhibit low mechanical strength, so warping of the substrate, and subsequent electromagnetically reflective surface device, can occur as the physical size of the substrate is increased. Some electromagnetically reflective surface devices are not necessarily large because they are designed to reflect electromagnetic signals from nearby horn antennas. However, this design consideration conflicts with the desire to have the electromagnetically reflective surface device as large as possible to receive as much power as possible from a base station. Electromagnetically reflective surface devices have incorporated air gaps to obtain wide bandwidth performance, but such structures typically exhibit low mechanical stability. To increase bandwidth, dual loop structures have been proposed. However, these devices are inadequate to cover the fractional bandwidth corresponding to the entire FR3 band for 6G (7- 15GHz). Accordingly, a unit cell geometry to solve insufficient bandwidth yet exhibit sufficient mechanical strength to enable large electromagnetically reflective surface devices is needed.

[0045] Referring to FIG. 1, a cross-sectional edge view of an example electromagnetically reflective surface device 10 is shown comprising a plurality of RIS elements 12 positioned on first major surface 14 of substrate 16. In some embodiments, the RIS element 12 is directly affixed to the first major surface 14. Meanwhile, a second adhesive layer 30 serves to bond the cover plate 26 and the substrate 16 together. As discussed more fully hereinbelow, each RIS element 12 within a unit cell may comprise a plurality of electrically conductive layers. In some embodiments, an electrically conductive ground plane 18 may be disposed on theAtorney Docket No. SP25-051 opposing second major surface 20 of substrate 16. In some embodiments, a fourth adhesive layer 34 may be used to bond the ground plane 18 to the substrate 16, providing both structural integrity and effective electrical grounding. As used herein, a ground plane is an electrically conductive surface that serves as a reflecting surface for radio frequency waves. The ground plane is typically large compared to the wavelength of the incident electromagnetic wave. The ground plane may generally extend across substantially all of the second major surface of substrate 16, or at least that portion opposite, (e.g., having the same general footprint as) the cumulative RIS elements 12. However, the ground plane need not be continuous and may, in various embodiments, comprise multiple openings (areas of non-electrical conductivity). For example, the ground plane may comprise a metallic mesh. These openings can serve various purposes, including transparency, weight reduction, cost reduction, capacitance control between RIS elements 12 and ground plane 18 or integration with other components.

[0046] First and second major surfaces 14, 20 may be parallel, or substantially parallel, for example within 5 degrees of parallel, or within 4 degrees, within 3 degrees, within 2 degrees, within 1 degree, within 0.5 degrees, or even within 0.25 degrees or less. Substrate 16 may comprise various materials, including glass, for example and without limitation, silicate glasses such as borosilicate glass (e.g., aluminoborosilicate glass); dielectric substrates like FR4 (a glass-reinforced epoxy laminate), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), ZEONEX®, a cyclo olefin polymer, and / or polyimide (PI); semiconductor materials such as Si and / or GaAs; as well as hybrid substrates like Rogers printed circuit board material manufactured by the Rogers Corporation. If the electromagnetically reflective surface device is to be optically transparent, a substrate 16 that exhibits the desired transparency may be selected.

[0047] In embodiments, thickness Ts of substrate 16 may be equal to or less than about 3.0 mm, for example equal to or less than about 2.8 mm, equal to or less than about 2.5 mm, equal to or less than about 2.3 mm, equal to or less than about 2. 1 mm, equal to or less than about 1.9 mm, equal to or less than about 1.7 mm, equal to or less than about 1.5 mm, equal to or less than about 1.3 mm, equal to or less than about 1.1 mm, equal to or less than about 0.9 mm, equal to or less than about 0.7 mm, or equal to or less than about 0.5 mm. For example, thickness Ts may be in a range from about 0.1 mm to about 3.0 mm. A desired thickness is varied according to the operation frequency, bandwidth, and dielectric constant of the substrate 16. In some embodiments, for a 7-14 GHz wideband, athickness Ts of 2.8 mm forthe substrate 16 may be selected to meet the operational requirements. In other embodiments, for a 25-30Atorney Docket No. SP25-051 GHz wideband, a thickness Ts of 0.5 mm for the substrate 16 may be more appropriate. The selected thickness ranges ensure that the required bandwidth can be achieved while also suppressing higher-order modes.

[0048] In some embodiments, substrate 16 may comprises a plurality of layers to achieve the desired glass thickness. Such a design not only aids in meeting precise thickness specifications but also enhances the robustness and durability of the product. For example, as shown in FIG. 2, in some embodiments, substrate 16 may comprise a plurality of glass sheets 22 arranged in a stack configuration, which may be bonded together using a third adhesive layer 32 or other suitable lamination technique. Various lamination processes can be employed, including but not limited to dry, wet, thermal, pressure, light, and low-temperature lamination methods. If the thickness of the third adhesive layer 32 exceeds 0.05 mm, this additional thickness must be considered when determining the overall thickness Ts of substrate 16. In such cases, it may be necessary to adjust the thickness of the individual glass sheets 22 or reduce the number of the third adhesive layer 32 to compensate for the increased bonding material thickness.

[0049] The glass substrates may have a dielectric constant equal to or less than 10. In some embodiments, a cover plate 26, e.g., a glass cover, may be positioned over and adhered to RIS elements 12 and substrate 16 with a first adhesive layer 28. The cover plate 26 should exhibit a coefficient of thermal expansion (CTE) value similar to that of the glass sheet 22 to minimize the risk of product warpage. In some embodiments, the difference between the CTE values of the cover 26 and the glass sheet 22 should be kept within a factor of ten to ensure dimensional stability and prevent deformation under varying temperature conditions. In some embodiments, for aesthetic enhancement, a decorative image can be directly printed on the cover plate 26, or alternatively, in some embodiments, a film featuring a printed decorative image can be applied.

[0050] The material used for RIS elements 12 may include one or more metals (e.g., copper, gold, silver, titanium), a metal oxide conductor (e.g., transparent metal oxide conductor), and / or graphene, to name a few. The thickness Tr of electrically conductive RIS elements 12 can be greater than the skin depth, 8, of RIS elements 12, where 8 = (2p / cop)1 / 2and the parameters p, co, and p represent the resistivity, angular frequency, and permeability of the electrically conductive layer, respectively. For example, thickness Tr of each RIS element 12 (i.e., the electrically conductive layers) may be, for example, in a range from about 100 nanometers (nm) to about 3 micrometer (pm), such as in a range from about 200 nm to about 3 pm, in a range from about 300 nm to about 3 pm, in a range from about 400 nm to about 3 pm, in aAtorney Docket No. SP25-051 range from about 500 nm to about 3 m, in a range from about 600 nm to about 3 pm, in a range from about 700 nm to about 3 pm, in a range from about 800 nm to about 3 pm, or in a range from about 900 nm to about 3 pm, including all ranges and subranges therebetween. In some embodiments, thickness Tr of each RIS element 12 may be in a range from about 100 nanometers (nm) to about 2.8 pm, for example in a range from about 100 nm to about 2.6 pm, in a range from about 100 nm to about 2.4 pm, in a range from about 100 nm to about 2.2 pm, in a range from about 100 nm to about 2.0 pm, in a range from about 100 nm to about 1.8 pm, in a range from about 100 nm to about 1.6 pm, in a range from about 100 nm to about 1.4 pm, in a range from about 100 nm to about 1.2 pm, in a range from about 100 nm to about 1.0 pm, in a range from about 100 nm to about 0.8 pm, in a range from about 100 nm to about 0.6 pm, in a range from about 100 nm to about 0.4 pm, or in a range from about 100 nm to about 0.2 pm, including all ranges and subranges therebetween.

[0051] In embodiments, RIS elements 12 may comprise a uniform layer. That is, RIS elements 12 may, in some embodiments, be substantially uniform in thickness and everywhere continuous (not include gaps, holes, etc.) within the boundaries of the electrically conductive layer comprising an individual RIS element. A substantially uniform (e.g., continuous and contiguous, solid) RIS element 12 such as described above will be referred to as a patch. However, as described later, RIS element 12 may be in a variety of different forms that are not uniformly continuous and may be paterned (e.g., comprising a plurality of open areas). For example, a RIS element 12 may comprise a plurality of discrete electrically conductive layers within a given unit cell, the plurality of electrically conductive layers disposed on a same plane.

[0052] As shown in FIG. 3, the plurality of RIS elements 12 may be arranged on substrate 16 in a periodic manner, e.g., a periodic array. For example, FIG. 3 depicts atop view of another example electromagnetically reflective surface device 10 comprising a plurality of RIS elements 12 configured as patches and arranged as an 8 x 8 array on first major surface 14, thereby forming a square array of 64 RIS elements arranged in 64 unit cells 24. That is, an RIS element 12 is separated from an immediately adjacent RIS element by a gap G. Each unit cell comprises an RIS element and a portion of the substrate 16 surrounding the RIS element within gap G (see FIG. 1). Unit cells 24 are arranged with a periodicity P, wherein the periodicity P can be determined between the midpoint of the gap G between a selected unit cell 24 and a first adjacent unit cell to the midpoint of another gap G between the selected RIS element and a second adjacent unit cell positioned opposite the first adjacent unit cell (i.e., the selected unitAtorney Docket No. SP25-051 cell is positioned between the first and second adjacent unit cells with no other unit cells therebetween). Accordingly, P may also be used to designate the length of a unit cell. Gap G may be uniform between the plurality of unit cells. Thus, for example, for an array of circular RIS elements, an RIS element selected from the array may have four adjacent RIS elements, and the gap G between each of the four adjacent RIS elements and the selected RIS element will be equal. Where the RIS element is an edge element with no adjacent RIS element on one side, the period P may be determined based on an equal distance on both sides (e.g., all sides) of the RIS element, provided the amount of substrate 16 extending past the edge RIS element is greater than 'A G. For example, referring to FIG. 1, period P of the left-most unit cell is G / 2 on the right side of the RIS element + the length L of the RIS element + G / 2 to the left of the left-most RIS element. Turning to FIG. 3, more generally, unit cells of the array have a period of Pl and P2, where, as used herein, Pl is the period of columns of the array and P2 refers to the period of rows of the array. In some embodiments, unit cells may be rectangular, where P 1 does not equal P2. For example, a length of the RIS element may be greater than or less than a width of the RIS element.

[0053] FIG. 4 is a top view of a single unit cell 24 for still another electromagnetically reflective surface device 10 comprising a period (length) P.

[0054] Outer Ring

[0055] RIS element 12 of unit cell 24 comprises a circular, annular, outer ring 100 (shown in isolation in FIG. 5) comprising a first outer edge 102 with a first radius R1 relative to a center point 104 and a second inner edge 106 with a second inner radius R2 relative to center point 104. A width W 1 of annular outer ring 100 between first outer edge 102 and second inner edge 106 along a radial line 108 extending outward from center point 104 (i.e., a difference between R1 and R2) may be in a range from about 0.2 mm to about 0.6 mm. Outer ring 100 is concentric with center point 104 and is comprised of an electrically conductive material, for example, but not limited to, a metal such as copper, silver, gold, titanium, or a metal alloy. In further embodiments, first outer edge 102 may be comprised of a conductive metal oxide or other conductive material such as graphene. An electrical conductivity of the electrically conductive material may be greater than about IxlO6Siemens / meter (S / m).

[0056] Curved Segments

[0057] RIS element 12 further comprises a plurality of curved segments 110 (i.e., curved dipoles), such as four curved segments 110a, 110b, 110c, and 1 lOd, and is shown together with outer ring 100 in FIG. 6. The curved segments 110 may be circular arcs concentric with centerAtorney Docket No. SP25-051 point 104 and therefore concentric with annular outer ring 100. Curved segments 110 may be annular segments positioned between annular outer ring 100 and center point 104. Each curved segment 110 comprises an outer edge 112 having an outer radius R3 and an inner edge 114 comprising an inner radius R4. For example, in the embodiment depicted in FIG. 6, each curved segment 110a, 110b, 110c, and 1 lOd comprises a corresponding outer edge 112a, 112b, 112c, and 112d, and a corresponding inner edge 114a, 114b, 114c, and 114d. Each of the outer edges 112a, 112b, 112c, and 112d and each of the inner edges 114a, 114b, 114c, and 114d is curved, for example a circular arc. In embodiments, each curved segment 110 is identical to another curved segment 110. A width W2 of each curved segment between outer edge 112 and inner edge 114 along radial line 108 extending outward from center point 104 through a curved segment may be in a range from about 0.2 to about 0.6. For example, W2 may be equal to W1. Each curved segment 110 is comprised of an electrically conductive material, for example, but not limited to, a conductive metal such as copper, silver, gold, titanium, or a metal alloy. In embodiments, the electrically conductive material may comprise a metal oxide or graphene.

[0058] In embodiments, outer edge 112 of each curved segment 110 may he on a circle 116 with radius R3 and extend over an angular range a from about 60 degrees to less than 90 degrees. That is, in embodiments comprising four curved segments, the four segments may be evenly distributed across four quadrants such that a distance D between ends of outer edges is equal between all segments. Or, in other words, four radial lines (shown as dashed and doted lines in FIG. 6) extending from center point 104 and bisecting each curved segment will be angularly separated from an adjacent similar radial line by 90 degrees.

[0059] First Gap

[0060] A gap G1 between interior radius R2 of annular outer ring 100 and each outer radius R4 (e.g., circle 116) along a radial line extending from center point 104 through any one of curved segments 102a-d may be in a range from about 0.25 to about 0.45 mm.

[0061] Patches

[0062] RIS element 12 further comprises a plurality of electrically conductive patches 120 (i.e., coupling patches), each patch comprising a curved edge 122 and a straight edge 124, as shown in FIG. 7 in combination with outer ring 100 and curved segments 110. Each curved edge 122 may be a circular arc wherein the curved edge is connected to the straight edge at both ends of the curved edge. Thus, each patch may comprise a segment of a circle. Each curved edge 122 is concentric with center point 104 and is comprised of an electrically conductive material, for example a metal such as, but not limited to, copper, silver, gold, titanium, or a metal alloy. InAtorney Docket No. SP25-051 embodiments, the electrically conductive material may comprise a metal oxide or graphene. An electrical conductivity of the electrically conductive material may be greater than about IxlO6S / m. In the embodiment of FIGS. 4 and 7, RIS element 12 comprises two patches 120, a first patch 120a and a second patch 120b, the two patches 120a, 120b each comprising respective curved edges 122a, 122b, and respective straight edges 124a, 124b, and wherein the straight edges 124a, 124b oppose each other and are parallel with each other such that auniform gap G2 is disposed between the two opposing straight edges 124a, 124b. Additionally, curved edge 122a of first patch 120a may have a first radius R5a and second curved edge 106b of second patch 120b may have a second radius of curvature R5b (see also FIG. 8 showing patches 120a, 120b in isolation). In embodiments, R5b may be equal to R5a. Moreover, curved edge 122a and 122b may be concentric with first outer edge 102 of annular outer ring 100 or an outer curved edge 112 of a curved segment 110 (e.g., circle 116). In embodiments, each curved edge 122a, 122b of patches 120a, 120b may extend over an angular range p greater than 150 degrees but less than 180 degrees (see FIG. 9 showing a single patch 120 in isolation), for example in a range from about 150 degrees to about 175 degrees, in a range from about 150 degrees to about 170 degrees, in a range from about 150 degrees to about 165 degrees, in a range from about 150 degrees to about 160 degrees, or in a range from about 150 degrees to about 155 degrees, including all ranges and subranges therebetween.

[0063] In embodiments, a gap G3 between each inner curved edge 114 of a curved segment 110 and a curved edge 122 of a patch 120 (e.g., patches 120a, 120b) along radial line 108 extending outward from center point 104 may be in a range from about 0.25 mm to about 0.45 mm.

[0064] Bar Segment

[0065] As shown in FIGS. 4 and 10, RIS element 12 may further comprise a bar segment 130 (i.e., dipole) disposed between straight edges 124a and 124b of patches 120a, 120b within gap G2 equidistant from both straight edge 124a and straight edge 124b. A width W3 of bar segment 130 may be in a range from about 0.2 mm to about 0.6 mm. A length LI of bar segment 130 may be greater than an arc length La of any one of the outer edges 112 of any one of curved segments 110, where arc length La is calculated as rOjt / l 80. and where r is the radius of the arc and 0 is the angle in degrees subtended by the arc. Thus, the arc length of any one of outer curved edges 112 is calculated as R3-0-K / 180. In embodiments, the circumferential length of first outer edge 102 of annular outer ring 100, calculated as 27tr, may be greater than four times the length LI of bar segment 130. In embodiments, the width W3 of bar segmentAtorney Docket No. SP25-051 130 is less than the maximum width W4 of any one of patches 120 in a direction orthogonal to the straight edge 124 adjacent to the bar segment (see FIG. 9). A gap between bar segment 130 and an adjacent patch 120 can be in a range from about 0.25 mm to about 0.45 mm.

[0066] Bar segment 130 is comprised of an electrically conductive material, for example a metal such as, but not limited to copper, silver, gold, titanium or a metal alloy. In embodiments, the electrically conductive material may comprise a metal oxide or graphene. An electrical conductivity of the electrically conductive material may be greater than about IxlO6S / m.

[0067] Patches 120 interact with bar segment 130 and can increase the bandwidth of the bar segment. Annular outer ring 100, bar segment 130, and curved segments 110 may be arranged to have different resonance frequencies within a target band, and the combination of different bands can provide a wide operational bandwidth.

[0068] In some embodiments, while one side of the substrate 16 (first major surface 14) may be paterned with an electrically conductive material (RIS elements 12) forming a plurality of unit cells 24, the opposing surface (second major surface 20) may be covered with a conducting material to form ground plane 18. Ground plane 18, if present, may be a uniform layer, for example a deposited metal layer or a metal oxide layer, or ground plane 18 may be a mesh ground plane as shown in FIG. 11. FIG. 11 depicts second major surface 20 of an electromagnetically reflective surface device 10 (e.g., substrate 16) comprising a plurality of interconnecting electrical conductors 30 that form the mesh. Pm is the period of the mesh (e.g., distance between parallel mesh conductors) and Wm is the mesh linewidth (i.e., width of individual mesh conductors).

[0069] Examples

[0070] Example 1

[0071] In a first example, an electromagnetic wave was directed at an electromagnetically reflective surface device comprising a rectangular patern of 31x40 unit cells comprising RIS elements in accordance with FIG 4 and incident thereon at an angle of 30 degrees relative to a normal to the surface of the electromagnetically reflective surface device. A frequency of the electromagnetic wave was varied to correspond to frequencies of 7 GHz, 8 GHz, 9 GHz, 10 GHz, 11 GHz, 12 GHz, 13 GHz, and 14 GHz. The unit cells had a period of 11 mm, the width W1 of the outer rings was 0.4 mm, the width W2 of the curved segments was equal to the width W1 of the outer ring, the width W3 of the bar segments was 0.4 mm, the width of the gap G1 was 0.35 mm, the width of the gap G2 was equal to the width of the gap Gl, and the width of the gap G4 between an edge of bar segment 130 and an adjacent straight edge 124 of a patchAtorney Docket No. SP25-051 120 was 035 mm. The substrate 16 was aglass substrate with atotal thickness of 2.8 mm. The reflected wave was detected at a reflection angle of 45 degrees and measured, and the phase of the reflected wave is ploted in FIG. 12 as a function of radius R1 for the indicated frequencies.

[0072] FIG. 12 shows various curves corresponding to each tested frequency, illustrating the relationship between the radius R1 and the reflected wave's phase shift. It reveals that as the radius R1 increases from approximately 1.70 mm to around 3.70 mm, there is a noticeable change in the phase of the reflected wave for each frequency. This phenomenon indicates the device's capability to manipulate the phase of reflected waves effectively by adjusting its physical parameters, such as the radius Rl. The data presented in FIG. 12 underscores the tunability and adaptability of the electromagnetically reflective surface device. By varying the radius Rl, one can achieve desired phase shifts across a wide range of frequencies, enabling precise control over the direction and shape of the reflected beam. This level of control is crucial for applications requiring dynamic beamforming capabilities, such as advanced communication systems or radar technologies.

[0073] Example 2

[0074] To evaluate the beamforming capability of this reflective surface under far-field conditions, results across frequencies from 8 GHz to 14 GHz are presented in FIG. 13 (a) through FIG. 13(f). These figures detail the directivity plots of reflected signal gain in decibels (dB) as a function of the theta angle, spanning from -100° to 100°. In these plots, each figure shows peak reflection points around the desired 45° angle, with variations in the reflected signal gains observed across the different frequencies. Notably, while the signal gain tends to decrease slightly as the frequency increases, the peak reflection points remain consistently near the target angle. This consistency is observed throughout the range from 8 GHz up to 14 GHz, indicating that the reflective surface maintains its ability to steer the incident wave towards the specified reflection angle effectively. The plots in FIGS. 13(a)-(f) validate the initial design parameters and highlight the reflective surface's proficiency in accurately steering an incident plane wave to the desired reflection angle of 45° across various frequencies. It demonstrates the robust performance and broad applicability of the reflective surface in electromagnetic wave manipulation across a wide frequency spectrum.

[0075] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modificationsAtorney Docket No. SP25-051 and variations provided they come within the scope of the appended claims and their equivalents.

Claims

Attorney Docket No. SP25-051What is claimed is:

1. An electromagnetically reflective surface device, comprising: a substrate comprising a first major surface and a second major surface opposite the first major surface, the first major surface comprising a plurality of RIS elements, each RIS element of the plurality of RIS elements comprising: an electrically conductive annular outer ring concentric with a center point; a plurality of electrically conductive curved segments positioned between the annular outer ring and the center point and concentric with center point, the plurality of curved segments arranged angularly equidistant from each other; a pair of electrically conductive patches positioned between the plurality of curved segments, each patch of the pair of comprising a straight edge and a curved edge, the straight edges arranged parallel with and spaced apart from each other and the curved edges concentric with the center point; an electrically conductive bar segment positioned between and equidistant from the straight edges; and a ground plane disposed on the second major surface.

2. The electromagnetically reflective surface device of claim 1, wherein a width of the annular outer ring along a radial line extending outward from the center point is in a range from about 0.2 mm to about 0.6 mm.

3. The electromagnetically reflective surface device of claim 1 or claim 2, wherein the plurality of curved segments comprises four curved segments.

4. The electromagnetically reflective surface device of claim 3, wherein the four curved segments are arranged such that a midpoint of each curved segment of the four curved segment is positioned 90 degrees from an adjacent curved segment of the four curved segments.

5. The electromagnetically reflective surface device of any one of claims 1 to 4, wherein the ground plane comprises a metallic mesh.Attorney Docket No. SP25-0516. The electromagnetically reflective surface device of any one of claims 1 to 5, wherein the substrate comprises a glass substrate.

7. The electromagnetically reflective surface device of claim 6, wherein the glass substrate comprises a plurality of glass sheets arranged in a stack.

8. The electromagnetically reflective surface device of any one of claims 1 to 7, further comprising a glass cover plate disposed over the plurality of RIS elements.

9. The electromagnetically reflective surface device of any one of claims 1 to 8, wherein the plurality of RIS elements may be periodically arranged in a rectangular matrix.

10. The electromagnetically reflective surface device of any one of claims 1 to 9, wherein a dielectric constant of the substrate is less than 10.

11. The electromagnetically reflective surface device of any one of claims 1 to 10, wherein the bar segment comprises a length in a direction parallel with the straight edges of the pair of patches, and the length of the bar segment is greater than an arc length of an outer edge of one curved segment of the plurality of curved segments.

12. The electromagnetically reflective surface device of any one of claims 1 to 10, wherein the bar segment comprises a length in a direction parallel with the straight edges of the pair of patches, and a circumferential length of the annular outer ring is greater than four times the length of the bar segment.

13. The electromagnetically reflective surface device of any one of claims 1 to 10, wherein the bar segment comprises a length in a direction parallel with the straight edges of the pair of patches, and a width of one patch of the pair of patches along a radial line extending outward from the center point and orthogonal to the straight edge of the one patch is greater than a width of the of the bar segment in a direction orthogonal to the length of the bar segment.Attorney Docket No. SP25-05114. The electromagnetically reflective surface device of any one of claims 1 to 13, wherein a radius of an outer edge of the annular outer ring is in a range from about 1.7 mm to about 3.7 mm.

15. The electromagnetically reflective surface device of any one of claims 1 to 14, wherein the curved edge of each patch extends over an angular range p greater than 150 degrees but less than 180 degrees relative to the center point.

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