Reflective intelligent surfaces for communications systems that steer both horizontal and vertical components of reflections of incident radio frequency signals

Abstract

A reflective intelligent surface comprises a metasurface that is configured to steer both a horizontal component and a vertical component of a reflection of an incident RF signal.

Description

Attorney Docket No.9833.7410.WO REFLECTIVE INTELLIGENT SURFACES FOR COMMUNICATIONS SYSTEMS THAT STEER BOTH HORIZONTAL AND VERTICAL COMPONENTS OF REFLECTIONS OF INCIDENT RADIO FREQUENCY SIGNALS CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application Serial No.63 / 650,431, filed May 22, 2024, the entire content of which in incorporated herein by reference as if set forth in its entirety. FIELD

[0002] The present invention generally relates to radio communications and, more particularly, to reflective intelligent surfaces that can be used to redirect radio frequency ("RF") signals in desired directions. BACKGROUND

[0003] Numerous different wireless communications systems are known in the art such as, for example, cellular communications systems and wireless local area networks. In a cellular communications system, a geographic area is divided into a series of regions that are referred to as "cells" which are served by respective base stations. Each base station includes baseband equipment, radios and base station antennas that are configured to provide two-way RF communications with subscribers that are positioned throughout the cell served by the base station. The base station antennas generate radiation patterns (referred to herein as "antenna beams") that provide service to users within the coverage area of the base station or a predefined portion of the coverage area (e.g., a sector of the cell). Cellular network operators obtain exclusive licenses to use different portions of the frequency spectrum at each base station so that the base stations of different cellular network operators generally do not interfere with eachAttorney Docket No.9833.7410.WO other. Wireless local area networks (which are typically referred to as WiFi networks) operate in a similar manner to cellular communications systems, but typically over much smaller geographic areas such as a home, building or campus. WiFi networks include one or more radio / antenna units that are commonly referred to as access points to provide wireless service to the desired coverage area. WiFi networks, however, operate in several unlicensed frequency bands and thus nearby WiFi networks tend to interfere with each other.

[0004] Cellular operators and other communications companies are exploring providing cellular or other communications services such as fixed wireless access communication systems in frequency bands at 6 GHz or higher, including frequency bands throughout much of the millimeter wave frequency range. Much larger operating frequency bands are available in these higher frequency ranges, bringing about the possibility of extremely high bandwidth communications. However, operation in these higher frequency bands also brings about various challenges, as the size of the generated antenna beams decrease linearly with increasing frequency, potentially making it more difficult to provide coverage over wide areas, and because higher frequency RF signals do not pass well through obstacles such as hills, buildings vegetation and the like. SUMMARY

[0005] Pursuant to embodiments of the present invention, reflective intelligent surfaces are provided that comprise a metasurface that is configured to steer both a horizontal component and a vertical component of a reflection of an incident RF signal.

[0006] In some embodiments, the metasurface comprises a plurality of unit cells, and each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

[0007] In some embodiments, the metasurface is configured to steer both the horizontal and vertical components of the incident RF signal the same amount.

[0008] In some embodiments, the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 2⁰.

[0009] In some embodiments, the metasurface comprises a plurality of unit cells, and each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the firstAttorney Docket No.9833.7410.WO longitudinal axis. In some embodiments, the oblique angle is an angle of about 45⁰. In some embodiments, the reflective intelligent surface may further comprise a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis. In some embodiments, the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor. In some embodiments, the metasurface comprises a printed circuit board having a dielectric substrate, a first metallization pattern on a first major surface of the dielectric substrate and a second metallization pattern on a second major surface of the dielectric substrate. In some embodiments, the first through third metal segments of each unit cell are part of the first metallization pattern, and the second metallization pattern comprises a metal sheet.

[0010] In some embodiments, the metasurface comprises a plurality of unit cells, and each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring. In some embodiments, the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the first diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a fourth capacitor that has a longitudinal axis that extends along the second diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

[0011] In some embodiments, each first capacitor comprises facing first and second metal traces on a printed circuit board. In some embodiments, each first capacitor comprises a first varactor. In some embodiments, each unit cell further comprises second through fourth varactors. In some embodiments, the first through fourth varactors of each unit cell each extend at an angle of + / -45⁰ with respect to a side of the respective unit cell.

[0012] In some embodiments, the metasurface comprises a plurality of unit cells, and each unit cell comprises an outer annular metal ring and an inner annular metal ring. In some embodiments, each inner annular metal ring includes a plurality of varactors.Attorney Docket No.9833.7410.WO

[0013] In some embodiments, each annular metal ring is an annular square metal ring. In other embodiments, each annular metal ring is an annular octagonal metal ring. In some embodiments, a longitudinal axis of the first capacitor of each unit cell has a longitudinal axis that is offset from the diagonals of the respective annular metal rings. In some embodiments, each unit cell further comprises a discontinuous annular inner metal ring. In some embodiments, the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

[0014] Pursuant to further embodiments of the present invention, reflective intelligent surfaces are provided that comprise a metasurface comprising a plurality of unit cells, where the metasurface is configured to adjust reflection angles of both a horizontal component and a vertical component of an RF signal that is incident on the metasurface by at least 2⁰.

[0015] In some embodiments, the metasurface is configured to adjust a TE mode reflection phase and a TM mode reflection phase of the RF signal that is incident on the metasurface by at least 25⁰.

[0016] In some embodiments, each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the first longitudinal axis. In some embodiments, the oblique angle is an angle of about 45⁰. In some embodiments, the reflective intelligent surface may further comprise a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis, wherein the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor.

[0017] In some embodiments, each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

[0018] In some embodiments, the metasurface is configured to steer both the horizontal and vertical components of a reflection of the incident RF signal the same amount.

[0019] In some embodiments, each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring. In some embodiments, each first capacitor comprises facing first and second metal traces on a printed circuit board. In some embodiments, each first capacitor comprises a first varactor.Attorney Docket No.9833.7410.WO

[0020] In some embodiments, each unit cell comprises an outer annular metal ring and an inner annular metal ring.

[0021] In some embodiments, each inner annular metal ring includes first through fourth varactors.

[0022] Pursuant to still further embodiments of the present invention, reflective intelligent surfaces are provided that comprise a metasurface comprising a plurality of unit cells, where the metasurface is configured to adjust a first reflection angle of a vertical component of an incident RF signals in an operating frequency band of the reflective intelligent surface about the same amount as the metasurface adjusts a second reflection angle of a horizontal component of the incident RF signal.

[0023] In some embodiments, each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

[0024] In some embodiments, the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 2⁰.

[0025] In some embodiments, the metasurface comprises a plurality of unit cells, and each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an angle of about 45⁰ with respect to the first longitudinal axis. In some embodiments, the reflective intelligent surface may further comprise a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis to form a first capacitor.

[0026] In some embodiments, each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring.

[0027] In some embodiments, each unit cell comprises an annular metal ring and the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring.

[0028] In some embodiments, each first capacitor comprises facing first and second metal traces on a printed circuit board.

[0029] In some embodiments, each first capacitor comprises a first varactor. In some embodiments, each unit cell comprises an outer annular metal ring and an inner annular metalAttorney Docket No.9833.7410.WO ring. In some embodiments, each inner annular metal ring includes first through fourth varactors.

[0030] According to yet additional embodiments of the present invention, reflective intelligent surfaces are provided that comprise a metasurface comprising a plurality of unit cells, wherein each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the first longitudinal axis.

[0031] In some embodiments, the oblique angle is an angle of about 45⁰.

[0032] In some embodiments, the reflective intelligent surface further comprises a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis. In some embodiments, the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor. In some embodiments, each unit cell comprise part of an annular square metal ring and the first and second metal segments of each unit cell comprise part of the annular square metal ring. In some embodiments, the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular square metal ring. In some embodiments, each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the first diagonal of the annular square metal ring. In some embodiments, each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular square metal ring.

[0033] In some embodiments, each annular square metal ring is an outer annular square metal ring, and wherein each unit cell further comprises a discontinuous inner annular square metal ring. In some embodiments, the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

[0034] Pursuant to yet additional embodiments of the present invention, reflective intelligent surfaces are provided that comprise a metasurface having a plurality of unit cells, where each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular square metal ring.

[0035] In some embodiments, the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the firstAttorney Docket No.9833.7410.WO diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a fourth capacitor that has a longitudinal axis that extends along the second diagonal of the annular metal ring. In some embodiments, each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

[0036] In some embodiments, each first capacitor comprises facing first and second metal traces on a printed circuit board.

[0037] In some embodiments, each first capacitor comprises a varactor.

[0038] In some embodiments, each annular metal ring is an annular square metal ring.

[0039] In some embodiments, a longitudinal axis of the first capacitor of each unit cell has a longitudinal axis that is offset from the diagonals of the respective annular metal rings.

[0040] In some embodiments, the annular square metal rings are outer annular square metal rings, and wherein each unit cell further comprises a discontinuous annular inner metal ring.

[0041] In some embodiments, the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

[0042] Pursuant to yet other embodiments of the present invention, reflective intelligent surfaces are provided that comprise a a metasurface having a plurality of unit cells, where each unit cell comprises an outer annular metal ring, an inner annular metal ring having a plurality of discontinuities, and a plurality of circuit elements that span the respective discontinuities in the inner annular metal ring.

[0043] In some embodiments, the plurality of circuit elements comprises a plurality of varactors. In some embodiments, the plurality of circuit elements comprises a plurality of circuit elements that have adjustable reactances. In some embodiments, each circuit element extends at an angle of 45⁰ with respect to at least one side of the outer annular metal ring. In some embodiments, the metasurface is configured to steer both a horizontal component and a vertical component of an incident RF signal. In some embodiments, each outer annular metal ring is an annular square metal ring. In some embodiments, the circuit elements are positioned along diagonals of the respective outer annular metal rings. In some embodiments, the metasurface is configured to steer both the horizontal and vertical components of the incident RF signal theAttorney Docket No.9833.7410.WO same amount. In some embodiments, the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 25⁰. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG.1 is a is a schematic diagram illustrating operation of a reflective intelligent surface.

[0045] FIGS.2A-2F are schematic plan views of unit cells of conventional reflective intelligent surfaces.

[0046] FIGS.3A and 3B are graphs that illustrate how the TE mode reflection phase and the TM mode reflection phase, respectively, of the unit cell of FIG.2E vary for incident RF signals at different frequencies as a function of the capacitance of the unit cell.

[0047] FIG.4 is a plan view of a reflective intelligent surface according to embodiments of the present invention.

[0048] FIG.5 is a plan view of a reflective intelligent surface according to further embodiments of the present invention.

[0049] FIGS.6A and 6B are graphs that illustrate how the TE mode reflection phase and the TM mode reflection phase, respectively, of the unit cell of FIG.5 vary for incident RF signals at different frequencies as a function of the capacitance of the unit cell.

[0050] FIG.7 is a plan view of a unit cell of a reflective intelligent surface according to still further embodiments of the present invention.

[0051] FIGS.8A and 8B are graphs that illustrate how the TE mode reflection phase and the TM mode reflection phase, respectively, of the unit cell of FIG.7 vary for incident RF signals at different frequencies as a function of the capacitance of the unit cell.

[0052] FIG.9A is a graph of the directivity of the antenna beams reflected by the reflective intelligent surface of FIG.2E as a function of angle in the horizontal (azimuth) plane.

[0053] FIG.9B is a graph of the directivity of the antenna beams reflected by a reflective intelligent surface having the unit cell design of FIG.7 as a function of angle in the horizontal (azimuth) plane. DETAILED DESCRIPTION

[0054] Reflective intelligent surfaces are an emerging technology that may be used in wireless communications systems. A reflective intelligent surface does not actively generate RFAttorney Docket No.9833.7410.WO signals, but instead reflects RF signals that are incident thereto, and have the capability to "steer" the reflected signals in a desired manner. The incident RF signals may be signals that are generated by, for example, cellular base station antennas, WiFi access points, or the like. A reflective intelligent surface includes a surface that comprises a large number of "unit cell" structures that can be configured to cause the reflections of incident RF signals to exit the reflective intelligent surface in desired directions. Typically, a reflective intelligent surface has a frequency dependent response such that the direction at which the reflections of RF signals exit the surface will be dependent on the frequency of the RF signal as well as the configuration of the reflective intelligent surface.

[0055] A reflective intelligent surface may be a passive (unpowered) device or an active (powered) device. A passive reflective intelligent surface is preconfigured to redirect incident RF radiation in a frequency band of interest in a specific manner that does not change. A passive reflective intelligent surface may be used, for example, to reflect a portion of the RF radiation emitted by a nearby base station antenna into locations where the base station antenna does not have good service. For example, a base station antenna that provides coverage to a predefined region may struggle to provide acceptable levels of service to a courtyard within the predefined region that is surrounded by office buildings. A passive reflective intelligent surface may be deployed on one of the buildings or in another location and can be configured to redirect RF signals emitted by the base station antenna into the courtyard though a gap between the buildings. The passive reflective intelligent surface may likewise redirect signals emitted by user devices in the courtyard toward the base station antenna. The reflective intelligent surface steers the reflected RF energy in a desired direction by including resonant circuits in the unit cells that change the phase of the reflected RF signal in a desired fashion.

[0056] Active reflective intelligent surfaces are typically referred to as "reconfigurable" reflective intelligent surfaces, since the reflection properties of the reflective intelligent surface may be changed in real time. For example, the reflection properties of a reconfigurable reflective intelligent surface may be changed on a time-slot-by-time-slot basis of a time division duplex communication system. This may allow the reconfigurable reflective intelligent surface to redirect RF signals from a fixed source (e.g., a base station antenna or WiFi access point) in different directions during different time slots. As such, the reflective intelligent surface canAttorney Docket No.9833.7410.WO redirect incident RF signals toward specific users or groups of users on a time slot by time slot basis.

[0057] Existing reflective intelligent surfaces adjust the phase of the TE mode of the reflected RF signals. The present invention is based, in part, on a realization that both passive and reconfigurable reflective intelligent surfaces can be developed that will also adjust the phase of the TM mode of the reflected RF signals, and hence such reflective intelligent surfaces will change both the horizontal and vertical components of the reflected RF signals. This may provide, for example, up to a 3 dB increase in the peak magnitude of the reflected RF signals, providing a significant (doubling) of the effectiveness of the reflective intelligent surfaces.

[0058] Pursuant to embodiments of the present invention, reflective intelligent surfaces are provided that redirect both the horizontal and vertical components of incident RF signals. Herein, references to redirecting an RF signal that is incident on a reflective intelligent surface means that the angle at which the reflection of the incident RF signal exits the reflective intelligent surface is adjusted from the reflection angle that would occur if the reflective intelligent surface was replaced with a solid metal reflector. The reflective intelligent surfaces according to some embodiments of the present invention may be passive reflective intelligent surfaces that comprise one or more panels of unit cell structures that implement the reflective intelligent surface. The unit cell structures may have a preconfigured response whereby RF signals incident on the reflective intelligent surface are reflected at an angle that is determined by the frequency of the incident signal and the phase adjustment imparted by the reflective intelligent surface. Such passive reflective intelligent surfaces may be highly useful in situation where the positional relationships between (1) an RF source (e.g., a base station antenna, WiFi access point, etc.), (2) the reflective intelligent surface, and (3) a coverage area for the passive reflective intelligent surface (i.e., a region where the reflected RF energy needs to be redirected) are all known in advance. In such a situation, the passive reflective intelligent surface may be designed to reflect the incident RF signals from the base station at an angle that will redirect such RF signals to the coverage area for the passive reflective intelligent surface.

[0059] The reflective intelligent surfaces according to other embodiments of the present invention may be reconfigurable reflective intelligent surfaces that again comprise one or more panels of unit cell structures that implement the reflective intelligent surface. The unit cells may include varactors or other active (powered) components that allow the reactance (e.g.,Attorney Docket No.9833.7410.WO capacitance and / or inductance) of the unit cell to be changed, which in turn changes the phase of the reflected signal allowing the angle of the reflected signal to be adjusted. This capability may be particularly advantageous with respect to high frequency signals – which may have narrow beamwidth reflected antenna beams – as it allows the reflected antenna beams to actively be steered in the direction of individual users or groups of users on, for example, a time slot by time slot basis.

[0060] The reflective intelligent surfaces according to embodiments of the present invention may be used in a wide variety of applications. They may be particularly useful in higher frequency applications such as applications operating at frequencies above 6 GHz and throughout the millimeter wave frequency range, including WiFi application, high frequency cellular applications and fixed wireless access applications, since the size of the reflective intelligent surface scales inversely with frequency.

[0061] Specific example embodiments of the present invention will now be described with reference to the accompanying figures.

[0062] FIG.1 is a schematic diagram illustrating operation of a reflective intelligent surface. As shown in FIG.1, a signal source 10 is provided that transmits and receives RF signals. The signal source may be, for example, a base station of a cellular communication system that includes a radio 12 that generates RF signals from baseband data and a base station antenna 14 that transmits the RF signals into free space, typically by concentrating the RF energy into a narrowed antenna beam 16 that is emitted in a desired direction. The base station antenna may be configured to provide cellular service to users within a predefined coverage area 20, such as a cell of the cellular communication system or a sub-section thereof (e.g., a sector). In some cases, the antenna beam 16 may have a fixed shape and size that is designed to provide coverage throughout the predefined coverage area 20. In other cases, the antenna beam 16 may be a narrower antenna beam that may be steered throughout the predefined coverage area 20.

[0063] As is further shown in FIG.1, the coverage area 20 may include one or more regions 22 where the base station antenna 14 is unable to provide good service. This may happen, for example, because physical obstacles may be present on the line-of-sight path between the base station antenna 14 and the regions 22 such as hills, buildings 24 or the like. While the base station could be moved to provide better coverage to one or more regions 22, such moves are expensive and typically result in the creation of other regions 22 that have poorAttorney Docket No.9833.7410.WO service. Another option is to provide one or more separate base stations (e.g., small cell base stations) that provide service to the regions 22, but adding new base stations is very time consuming and expensive such that in most cases it will not be economically practical to add new base stations to enhance service in regions having poor service.

[0064] As shown in FIG.1, a reflective intelligent surface 30 may be used to redirect RF signals from the base station antenna 14 or other signal source that are incident on the reflective intelligent surface 30 in a desired direction. The reflective intelligent surface 30 may be mounted, for example, on the side of a building. As shown in FIG.1, the RF signals from base station antenna 14 that are incident on the reflective intelligent surface 30 are redirected at a desired angle so that the reflected RF signals provide coverage to region 22-1, which otherwise would not receive good service.

[0065] As is known in the art, reflective intelligent surfaces include a metamaterial surface which will be referred to herein as a "metasurface." As shown in FIG.1, the front surface of reflective intelligent surface 30 includes a metasurface 32 that is configured to steer the reflections of the RF signals that are incident on the metasurface 32. The metasurface 32 may have a unit cell structure, meaning that the metasurface 32 comprises a large number of much smaller unit cells. Each unit cell may include one or more tunable electromagnetic characteristics. For passive reflective intelligent surfaces, the tunable electromagnetic characteristic may be tuned at the time of manufacture; in other words, each unit cell is designed so that its electromagnetic characteristic is "tuned" to a desired value at the time of manufacture but afterwards cannot be further tuned. With reconfigurable (i.e., active) reflective intelligent surfaces, the tunable electromagnetic characteristic may be dynamically tuned so that during operation the tunable electromagnetic characteristic may be dynamically tuned to different desired values. In example embodiments, the tunable electromagnetic characteristic may be one or more reflection phases of the metasurface 32. The metasurface 32 may reflect incident signals in its operating frequency band with high reflection rates (i.e., with minimal losses) and the reflection phases of an incident RF signal can be set to a desired value (where the reflection phase will vary as a function of frequency) to cause incident RF signals to reflect from the metasurface 32 at a desired angle. The metasurface 32 may, therefore, steer an incident RF signal in a desired direction by changing the direction at which the main lobe of the incident signal is reflected form the metasurface 32.Attorney Docket No.9833.7410.WO

[0066] Each unit cell may include a resonant circuit and may optionally include one or more integrated tunable elements that is / are used to tune one or more electrical resonances of the resonant circuit in response to being energized. The integrated tunable elements may be active component such as, for example, PIN diodes, varactors, transistors, microelectromechanical (MEM) systems, and / or a liquid crystal polymer devices. An active reflective intelligent surface includes control lines that carry control signals that are supplied to these active components to adjust the electrical resonances of the unit cells dynamically during operation to steer the reflected RF signals in desired direction(s). In example embodiments, the active reflective intelligent surface may comprise a printed circuit board that has a dielectric substrate, and the units cells may be implemented as metal traces on a first major surface of the dielectric substrate. The control lines may be formed on a second major surface of the dielectric substate, and the integrated tunable elements may be formed or surface mounted on one or both of the first and second major surfaces of the dielectric substate. By adjusting the resonances of the unit cells (e.g., by changing capacitances of one or more capacitors that are included in each unit cell) the reflected phases are adjusted.

[0067] A number of unit cell designs are known for the metasurfaces of a reflective intelligent surface. FIGS.2A-2F are schematic plan views of various known unit cell designs for reflective intelligent surfaces. As shown in FIG.2A, a unit cell 40 comprises a dielectric substrate 42. An annular metal ring 44 is formed on a front surface of the dielectric substrate 42. A pair of T-shaped metal elements 46-1, 46-2 extend inwardly from sides of the annular metal ring 44 to form capacitors. A metal pad (not visible in FIG.2A) may be formed on the opposed side of the dielectric substrate 42. The unit cell 40 only works on the vertical component of an RF signal incident on the unit cell 40.

[0068] FIG.2B illustrates a unit cell 50 that comprises a dielectric substrate 52, an annular metal ring 54 that is formed on a front surface of the dielectric substrate 52, and a pair of T-shaped metal elements 56-1, 56-2 that extend inwardly from sides of the annular metal ring 54. A metal pad (not visible in FIG.2B) may be formed on the opposed side of the dielectric substrate 52. The unit cell 50 only works on the vertical component of an RF signal incident on the unit cell 50. The amount of capacitance may be adjusted by changing the shape and / or size of the inner T-shaped metal elements 56-1, 56-2.Attorney Docket No.9833.7410.WO

[0069] FIG.2C illustrates a unit cell 60 that comprises a dielectric substrate 62 that has a horizontally-extending wide metal segment 64 and a plurality of right angle metal segments 66 that extend in the vertical direction from corners of the wide metal segment 64. A metal pad (not visible in FIG.2C) may be formed on the opposed side of the dielectric substrate 62. The unit cell 60 only works on the horizontal component of an RF signal incident thereon.

[0070] FIG.2D illustrates a unit cell 70 that comprises a dielectric substrate 72 that has an outer annular metal ring 74 formed on a front surface thereof. An I-shaped metal structure is formed on the dielectric substrate 72. The I-shaped metal structure comprises a vertically- extending metal segment 74 and a pair of horizontally-extending metal segments 76 that extend in both horizontal directions from ends of the vertically-extending metal segment 74. A metal pad (not visible in FIG.2D) may be formed on the opposed side of the dielectric substrate 72. The unit cell 70 only works on the vertical component of an RF signal incident thereon.

[0071] The unit cells 40, 50, 60, 70 of FIGS.2A-2D are each passive unit cells in that the resonant circuit of each unit cell 40, 50, 60, 70 is fixed at the time of manufacture and thus reflective intelligent surfaces formed with these unit cells 40, 50, 60, 70 will have a fixed response that does not change over time. FIGS.2E and 2F illustrate two conventional active unit cells for reflective intelligent surfaces.

[0072] Referring to FIG.2E, the unit cell 80 comprises a dielectric substrate 82 that has a pair of metal pads 84-1, 84-2 formed on a front surface thereof. The metal pads 84-1, 84-2 are separated by a gap 86 where no metal is provided. A varactor 88 (e.g., a surface mount element) is mounted to cross the gap 86 with the ends of the varactor 88 connected to the respective first and second metal pads 84-1, 84-2. A control circuit (not shown) may control the DC voltage applied to the metal pads 84-1, 84-2 so as to set a capacitance of the varactor 88 at a desired level.

[0073] Referring to FIG.2F, the unit cell 90 comprises a pair of dielectric substrates 92- 1, 92-2. Metal patterns are provided on the upper surface of upper dielectric substrate 92-2, on the lower surface of lower dielectric substrate 92-1, and in between the two dielectric substrates 92-1, 92-2. The metal pattern on the upper surface of upper dielectric substrate 92-2 comprises a pair of metal pads 94-1, 94-2 that form a capacitor. The metal pattern in between the two dielectric substrates 92-1, 92-2 may comprise a large metal pad 94-3 that is electrically connected to a reference voltage (e.g., ground) to form a ground plane. The metal pattern on theAttorney Docket No.9833.7410.WO lower surface of lower dielectric substrate 92-1 may comprise a control line 94-4. A PIN diode 96 (shown by a dashed box in the figure) is mounted on the lower surface of lower dielectric substrate 92-1 and connected to the control line 94-4. A first conductive via 98-1 has one end that is connected to a first terminal of the PIN diode 96 and extends through an opening in the metal pattern in between the two dielectric substrates 92-1, 92-2 to electrically connect to the first metal pad 94-1. A second conductive via 98-1 connected to a first terminal of the PIN diode 96 to connect the second terminal of the PIN diode 96 to the ground plane 94-3. The PIN diode 96 may be used to turn a capacitor of the unit cell 90 on or off.

[0074] FIGS.3A-3B are graphs that illustrate how the TE mode reflection phase of the unit cell 80 of FIG.2E (FIG.3A) and the TM mode reflection phase of the unit cell 80 of FIG. 2E (FIG.3B) vary for incident RF signals at different frequencies as a function of the capacitance of the unit cell 80. As shown in FIG.3A, the TE mode reflection phase varies widely as a function of the capacitance of the unit cell 80. For example, for an RF signal at a frequency of 3.5 GHz, the TE mode reflection phase is about 132⁰ for a first capacitance value (i.e., for the uppermost curve in FIG.3A), but is nearly -137⁰ for a second capacitance value (i.e., for the lowermost curve in FIG.3A). In other words, at the center of the operating frequency band, the unit cell 80 of FIG.2E can vary the TE mode reflection phase by as much as 269⁰ by adjusting the capacitance of the varactor 88 across the varactors full capacitance range. This phase variation can support a redirection of the reflected signal by about 20⁰. However, as shown in FIG.3B, the unit cell of FIG.2E can only vary the TM mode reflection phase by about 3⁰ by making the same changes in the capacitance of the varactor 88, showing that varying the capacitance of unit cell 80 has essentially no impact on the TM mode reflection phase. Thus, FIGS.3A and 3B illustrate that while changing the capacitance of the unit cell 80 results in large changes in the TE mode reflection phase, the change in capacitance has almost no impact on the TM mode reflection phase. Thus, FIGS.3A and 3B show that the unit cell 80 is only changing the horizontal component of the incident RF signal and is not impacting the vertical component of the incident RF signal. The other unit cell designs shown in FIGS.2A-2D and 2F all have the same limitation.

[0075] FIG.4 is a plan (front) view of a reflective intelligent surface 100 according to embodiments of the present invention. The call-out in FIG.4 is an enlarged view of one of the unit cells 110 of the reflective intelligent surface 100. The reflective intelligent surface 100 mayAttorney Docket No.9833.7410.WO be implemented, for example, using a printed circuit board that comprises a dielectric substrate 102 having a metal pattern 104 formed on one side of the dielectric substrate 102. A metal pad (not shown) may be on the opposed side of the dielectric substrate 102. Each unit cell 110 of the reflective intelligent surface 100 may comprise a metasurface 112 so that the reflective intelligent surface comprises a large metasurface 106. The reflective intelligent surface 100 is a passive reflective intelligent surface 100 that is configured at the time of manufacture to adjust the reflection angle of incident RF signals within the operating frequency band of the reflective intelligent surface 100 in a predetermined fashion.

[0076] As shown in the call-out of FIG.4, each unit cell 110 comprises an outer annular metal ring 120 having four sides 122-1 through 122-4. In the embodiment of FIG.4, the outer annular metal ring 120 comprises an annular square metal ring 120. Each unit cell 110 further comprises a discontinuous inner annular metal ring 130 having four sides 132-1 through 132-4 that are not connected to each other. In the embodiment of FIG.4, the inner annular metal ring comprises a discontinuous annular square metal ring 132 that includes regions (discontinuities) 134 where no metal is provided. A plurality of metal segments 140-1 through 140-4 connect each side 122-1 through 122-4 of the outer annular metal ring 120 to a respective one of the sides 132-1 through 132-4 of the inner annular metal ring 130. Each unit cell 110 further comprises first through fourth capacitors 150-1 through 150-4, where each capacitor 150 comprises first and second spaced apart metal traces 152, 154. Each capacitor 150 extends along a respective longitudinal axis 156. As can be seen, the longitudinal axes 156 of the first and third capacitors 150 extend along a first diagonal of the outer annular square metal ring 120, while the longitudinal axes 156 of the second and fourth capacitors 150 extend along a second diagonal of the outer annular square metal ring 120. The gap between the first and second spaced apart metal traces 152, 154 of each capacitor 150 form the discontinuities 134 in the inner annular metal ring 130.

[0077] The longitudinal axis 156 of each capacitor 150 extends at an angle of 45⁰ with respect to a side 122 of the outer annular square metal ring 120. For example, the longitudinal axes 156 of capacitors 150-1 and 150-3 each extend at an angle of 45⁰ with respect to side 122-3. Typically, the reflective intelligent surface 100 will be positioned for use so that sides 122-1 and 122-3 of the outer annular square metal ring 120 of each unit cell 110 are parallel to a plane defined by the horizon, and so that the sides 122-2 and 122-4 of each unit cell 110 areAttorney Docket No.9833.7410.WO perpendicular to the plane defined by the horizon (or alternatively, sides 122-2 and 122-4 of each unit cell 110 are parallel to the plane defined by the horizon and sides 122-1 and 122-3 of each unit cell 110 are perpendicular to the plane defined by the horizon). Since the capacitors 150 extend at an angle of + / -45⁰ with respect to the plane defined by the horizon, the capacitors 150 will act to adjust the reflection angle of both the horizontal and vertical components of incident RF signals.

[0078] The design of the unit cells 110 of reflective intelligent surface 100 will typically vary in a stepped manner across the reflective intelligent surface 100. As noted above, the reflective intelligent surface 100 is used to steer the reflection of an incident RF signal in a desired direction. As the reflective intelligent surface 100 has a discrete area, the desired reflection angle for RF signals that are incident on one side (e.g., the left side) of the reflective intelligent surface 100 will be different from the desired reflection angle for RF signals that are incident on the opposed side (e.g., the right side) of the reflective intelligent surface 100. Thus, the design of the unit cells 110 will typically vary in a stepped fashion based on the position of the unit cells 110 within the reflective intelligent surface 100. The unit cell design may also vary in the top-to-bottom direction of the reflective intelligent surface 100. The design of each unit cell 110 may be changed, for example, by changing the length of the electrodes that form the first through fourth capacitors 150-1 through 150-4 so that the capacitance levels of different unit cells 110 are different.

[0079] While in the description of FIGS.3A-3B and 4 above the TE mode reflection phase and the TM mode reflection phase are varied by changing the capacitance of the unit cells, it will be appreciated that embodiments of the present invention are not limited thereto. In other embodiments, the TE mode reflection phase and the TM mode reflection phase may varied by changing one or more inductances in the unit cells or by changing a combination of capacitance(s) and inductance(s).

[0080] Comparing the unit cell 110 of FIG.4 to the conventional passive unit cells 40, 50, 60 and 70 of FIGS.2A-2D, it can be seen that the conventional unit cells form capacitors with respect to two sides of the unit cells, while the unit cell 110 of FIG.4 has T-shaped metal elements along all four sides of the unit cell 110. The edges of the unit cells act as patch elements that provide the resonances that control operation of the reflective intelligent surface. By providing unit cells that generate resonances along all four sides of the unit cell it is possibleAttorney Docket No.9833.7410.WO to change both the TE mode reflection phase and the TM mode reflection phase of the unit cell (by setting the capacitance of the unit cell), thereby impacting both the horizontal and vertical components of RF signals that are incident on the unit cell / reflective intelligent surface 110 / 100.

[0081] FIG.5 is a plan view of a reflective intelligent surface 200 according to further embodiments of the present invention. The call-out in FIG.5 is an enlarged view of one of the unit cells 210 of the reflective intelligent surface 200. The reflective intelligent surface 200 may be implemented, for example, using a printed circuit board that comprises a dielectric substrate 202 having a metal pattern 204 formed on one side of the dielectric substrate. As reflective intelligent surface 200 is similar to reflective intelligent surface 100 of FIG.4, the discussion below will focus on the differences between the two reflective intelligent surfaces 100, 200.

[0082] As can be seen by comparing the call-outs of FIGS.4 and 5, the unit cell 210 is very similar to unit cell 110, but in unit cell 210 triangular shaped metal segments 240-1 through 240-4 replace the skinnier rectangular metal segments 140-1 through 140-4 that are provided in unit cell 110. As the remaining elements of unit cell 210 are identical to the corresponding elements of unit cell 110, the same reference numbers are used in FIG.5 to identify these like elements as are used in FIG.4. Replacing the skinnier rectangular metal segments 140-1 through 140-4 of unit cell 110 with the wider triangular shaped metal segments 240-1 through 240-4 that are included in unit cell 210 may advantageously increase the bandwidth of the unit cell. In particular, by replacing the skinnier rectangular metal segments 140-1 through 140-4 with the wider triangular shaped metal segments 240-1 through 240-4 the more RF energy is supplied to the capacitors which allows the phase change to be enhanced at band edge, thereby increasing the operating bandwidth of unit cell 210 as compared to unit cell 110.

[0083] FIGS.6A-6B are graphs that illustrate how the TE mode reflection phase and the TM mode reflection phase, respectively, of the unit cell 210 of FIG.5 varies for incident RF signals at different frequencies as a function of the capacitance of the unit cell 210. As shown in FIG.6A, the TE mode reflection phase varies widely as a function of the capacitance, similar to the conventional unit cell 80 of FIG.2E. For example, for an RF signal at a frequency of 3.5 GHz, the TE mode reflection phase is nearly 110⁰ for a first capacitance value and is nearly -147⁰ for a second, different capacitance value. In other words, at the center of the operating frequency band, the unit cell 210 of FIG.5 can vary the TE mode reflection phase by as much as 257⁰, which is comparable to the unit cell 80 of FIG.2E. Moreover, as shown in FIG.6B, the TMAttorney Docket No.9833.7410.WO mode reflection phase for the unit cell 210 of FIG.5 also varies widely as a function of the capacitance of the unit cell 210. For example, for an RF signal at a frequency of 3.5 GHz, the TM mode reflection phase is also about 110⁰ for a first capacitance value and is about -147⁰ for a second, different capacitance value. Thus, at the center of the operating frequency band, the unit cell 210 of FIG.5 also can vary the TM mode reflection phase by as much about 257⁰. Thus, FIGS.6A and 6B illustrate that the unit cell 210 of FIG.5 can vary the reflection phase of both the horizontal and vertical components of incident RF signals by about the same amount. In some embodiments, the metasurface may be configured to adjust reflection angles of both a horizontal component and a vertical component of an RF signal that is incident on the metasurface by at least 1⁰, by at least 2⁰, by at least 5⁰, or by at least 10⁰.

[0084] FIG.7 is a plan view of a reflective intelligent surface 300 according to still further embodiments of the present invention. The call-out in FIG.7 is an enlarged view of one of the unit cells 310 of the reflective intelligent surface 300. The reflective intelligent surface 300 may be implemented, for example, using a printed circuit board that comprises a dielectric substrate 302 having a metal pattern 304 formed on one side of the dielectric substrate 302. Each unit cell 310 of the reflective intelligent surface 300 may comprise a metasurface so that the reflective intelligent surface 300 comprises a large metasurface. The reflective intelligent surface 300 is an active reflective intelligent surface that can be reconfigured during operation (e.g., on a time slot by time slot basis of a time division multiple access communication scheme) to adjust the reflection angle of incident signals within the operating frequency band of the reflective intelligent surface 300 in a desired fashion. In other words, the reflective intelligent surface 300 may steer different incident RF signals in different directions (e.g., in the directions of different users or different groups of users).

[0085] As shown in the call-out of FIG.7, each unit cell 310 comprises an outer annular metal ring 320 having four sides 322-1 through 322-4. In the embodiment of FIG.7, the outer annular metal ring 320 comprises an annular square metal ring 320. Each unit cell 310 further comprises a discontinuous inner annular metal ring 330 having four sides 332-1 through 332-4 that are spaced apart from adjacent sides 332 by small gaps 334. A plurality of metal segments 340-1 through 340-4 connect each side 322-1 through 322-4 of the outer annular metal ring 320 to a respective one of the sides 332-1 through 332-4 of the inner annular metal ring 330. In the embodiment of FIG.7, the inner annular metal ring 330 comprises a discontinuous annularAttorney Docket No.9833.7410.WO square metal ring 330. Each unit cell 310 further comprises first through fourth circuit elements 350-1 through 350-4, where each circuit element 350 spans one of the respective gaps 334 so that each circuit element 350 is interposed between two of the sides 332 of the discontinuous inner annular metal ring 330. In an example embodiment, each circuit element may comprise a respective varactor 350. As is known in the art, a varactor is a type of diode that has a variable capacitance, where the amount of capacitance varies with the DC voltage across the varactor.

[0086] As shown in the callout of FIG.7, each circuit element 350 extends along a respective longitudinal axis 356. The longitudinal axes 356 of the first and third circuit elements 350 extend perpendicularly to and intersect a first diagonal of the outer annular square metal ring 320, while the longitudinal axes 356 of the second and fourth circuit elements 350 extend perpendicularly to and intersect a second diagonal of the outer annular square metal ring 320.

[0087] The longitudinal axis 356 of each circuit element 350 extends at an angle of 45⁰ with respect to two sides of the outer annular square metal ring 320. For example, the longitudinal axes 356 of circuit elements 350-1 and 350-3 each extend at an angle of -45⁰ with respect to side 322-3 of the outer annular square metal ring 320. Typically, the reflective intelligent surface 300 will be positioned for use so that the sides 322-1 and 322-3 of each unit cell 310 are parallel to the plane defined by the horizon and so that the sides 322-2 and 322-4 of each unit cell 310 are perpendicular to the plane defined by the horizon. Since the circuit elements 350 extend at an angle of + / -45⁰ with respect to the plane defined by the horizon, the circuit elements 350 will act to adjust the reflection angle of both the horizontal and vertical components of incident RF signals.

[0088] Control lines 362 may be connected to each circuit element 350 that control the state of the circuit elements 350. The reflective intelligent surface 300 may further include a micro controller 360 or other control circuit 360. The control circuit 360 is in communication with the radio (e.g., a 5G radio of a cellular base station) that generates the RF signals that are incident on the reflective intelligent surface 300. RF signals that are generated by user devices that are incident on the reflective intelligent surface 300 are received at, for example, a beamforming array of a base station antenna and passed to the radio of the base station. Since the locations of the base station antenna and the reflective intelligent surface 300 are fixed, the radio can calculate the location of each user device (although typically there is some degree of error in these calculations). The radio may then calculate the settings that should be applied toAttorney Docket No.9833.7410.WO the reflective intelligent surface 300 and sends this information to the control circuit 360. The control circuit 360 then controls the circuit elements 350 (e.g., the settings of a plurality of varactors) to achieve desired phase changes for each unit cell by sending or applying control signals to the circuit elements 350 via the control lines 362. The reflective intelligent surface 300 may actively steer the reflections of the incident RF signals in desired directions.

[0089] FIGS.8A and 8B are graphs that illustrate how the TE mode reflection phase and the TM mode reflection phase of the unit cell 310 of FIG.7 varies for incident RF signals at different frequencies as a function of the capacitance of the unit cells 310. As shown in FIG. 8A, the TE mode reflection phase varies widely as a function of the capacitance. For example, for an RF signal at a frequency of 3.5 GHz, the TE mode reflection phase is about 104⁰ for a first capacitance value but is more than -156⁰ for a second, different capacitance value. Moreover, as shown in FIG.8B, the unit cell 310 of FIG.7 can also vary the TM mode reflection phase. For example, for an RF signal at a frequency of 3.5 GHz, the TM mode reflection phase is also about 104⁰ for a first capacitance value and is about -157⁰ for a second, different capacitance value. Thus, FIGS.8A and 8B illustrate that the unit cell 310 of FIG.7 can vary the reflection phase of both the horizontal and vertical components of incident RF signals by about the same amount

[0090] FIG.9A is a graph of the directivity of the antenna beams reflected by the reflective intelligent surface of FIG.2E as a function of angle in the horizontal (azimuth) plane. As shown in FIG.9A, the reflected antenna beams have a flat directivity over a fairly wide range of angles (more than 30⁰) with a peak directivity of about 12 dB. FIG.9B is a graph of the directivity of the antenna beams reflected by a reflective intelligent surface having the unit cell design of FIG.7 as a function of angle in the horizontal (azimuth) plane. As can be seen in FIG. 9B, the reflective intelligent surfaces according to embodiments of the present invention generate more focused reflected antenna beams that have a peak directivity of about 15 dB and a sharper beam peak. This reflects the fact that the reflective intelligent surfaces according to embodiments of the present invention steer both the horizontal and vertical components of the reflected signal, and hence a 3 dB increase is directivity is achieved.

[0091] Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that thisAttorney Docket No.9833.7410.WO disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

[0092] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0093] It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

[0094] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0095] Herein, the term "substantially" means within + / - 10%.

[0096] 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" "comprising," "includes" and / or "including" when used herein, specify the presence of stated features, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and / or groups thereof.Attorney Docket No.9833.7410.WO

[0097] Aspects and elements of all of the embodiments disclosed above can be combined in any way and / or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.

Claims

Attorney Docket No.9833.7410.WO CLAIMS:

1. A reflective intelligent surface, comprising: a metasurface that is configured to steer both a horizontal component and a vertical component of a reflection of an incident RF signal.

2. The reflective intelligent surface of Claim 1, wherein the metasurface comprises a plurality of unit cells, and each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

3. The reflective intelligent surface of Claim 1, wherein the metasurface is configured to steer both the horizontal and vertical components of the incident RF signal the same amount.

4. The reflective intelligent surface of any of Claims 1-3, wherein the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 2⁰.

5. The reflective intelligent surface of Claim 1, wherein the metasurface comprises a plurality of unit cells, and each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the first longitudinal axis.

6. The reflective intelligent surface of Claim 5, wherein the oblique angle is an angle of about 45⁰.

7. The reflective intelligent surface of Claim 5, further comprising a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis.

8. The reflective intelligent surface of Claim 7, wherein the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor.Attorney Docket No.9833.7410.WO 9. The reflective intelligent surface of Claim 5, wherein the metasurface comprises a printed circuit board having a dielectric substrate, a first metallization pattern on a first major surface of the dielectric substrate and a second metallization pattern on a second major surface of the dielectric substrate.

10. The reflective intelligent surface of Claim 9, wherein the first through third metal segments of each unit cell are part of the first metallization pattern, and the second metallization pattern comprises a metal sheet.

11. The reflective intelligent surface of any of Claims 1-3, wherein the metasurface comprises a plurality of unit cells, and each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring.

12. The reflective intelligent surface of Claim 11, wherein the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring.

13. The reflective intelligent surface of Claim 12, wherein each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the first diagonal of the annular metal ring.

14. The reflective intelligent surface of Claim 13, wherein each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

15. The reflective intelligent surface of Claim 14, wherein each unit cell further comprises a fourth capacitor that has a longitudinal axis that extends along the second diagonal of the annular metal ring.

16. The reflective intelligent surface of Claim 13, wherein each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

17. The reflective intelligent surface of Claim 11, wherein each first capacitor comprises facing first and second metal traces on a printed circuit board.Attorney Docket No.9833.7410.WO 18. The reflective intelligent surface of Claim 11, wherein each first capacitor comprises a first varactor.

19. The reflective intelligent surface of Claim 18, wherein each unit cell further comprises second through fourth varactors.

20. The reflective intelligent surface of Claim 19, wherein the first through fourth varactors of each unit cell each extend at an angle of + / -45⁰ with respect to a side of the respective unit cell.

21. The reflective intelligent surface of any of Claims 1-20, wherein the metasurface comprises a plurality of unit cells, and each unit cell comprises an outer annular metal ring and an inner annular metal ring.

22. The reflective intelligent surface of Claim 21, wherein each inner annular metal ring includes a plurality of varactors.

23. The reflective intelligent surface of Claim 11, wherein each annular metal ring is an annular square metal ring.

24. The reflective intelligent surface of Claim 11, wherein each annular metal ring is an annular octagonal metal ring.

25. The reflective intelligent surface of Claim 11, wherein a longitudinal axis of the first capacitor of each unit cell has a longitudinal axis that is offset from the diagonals of the respective annular metal rings.

26. The reflective intelligent surface of Claim 11, wherein each unit cell further comprises a discontinuous annular inner metal ring.

27. The reflective intelligent surface of Claim 26, wherein the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

28. A reflective intelligent surface, comprising:Attorney Docket No.9833.7410.WO a metasurface comprising a plurality of unit cells, where the metasurface is configured to adjust reflection angles of both a horizontal component and a vertical component of an RF signal that is incident on the metasurface by at least 2⁰.

29. The reflective intelligent surface of Claim 28, wherein the metasurface is configured to adjust a TE mode reflection phase and a TM mode reflection phase of the RF signal that is incident on the metasurface by at least 25⁰.

30. The reflective intelligent surface of Claims 28 or 29, wherein each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the first longitudinal axis.

31. The reflective intelligent surface of Claim 30, wherein the oblique angle is an angle of about 45⁰.

32. The reflective intelligent surface of Claim 30, further comprising a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis, wherein the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor.

33. The reflective intelligent surface of Claims 28 or 29, wherein each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

34. The reflective intelligent surface of Claims 28 or 29, wherein the metasurface is configured to steer both the horizontal and vertical components of a reflection of the incident RF signal the same amount.

35. The reflective intelligent surface of Claims 28 or 29, wherein each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring.Attorney Docket No.9833.7410.WO 36. The reflective intelligent surface of Claim 35, wherein each first capacitor comprises facing first and second metal traces on a printed circuit board.

37. The reflective intelligent surface of Claim 35, wherein each first capacitor comprises a first varactor.

38. The reflective intelligent surface of Claims 28 or 29, wherein each unit cell comprises an outer annular metal ring and an inner annular metal ring.

39. The reflective intelligent surface of Claim 38, wherein each inner annular metal ring includes first through fourth varactors.

40. A reflective intelligent surface, comprising: a metasurface comprising a plurality of unit cells, wherein the metasurface is configured to adjust a first reflection angle of a vertical component of an incident RF signals in an operating frequency band of the reflective intelligent surface about the same amount as the metasurface adjusts a second reflection angle of a horizontal component of the incident RF signal.

41. The reflective intelligent surface of Claim 40, wherein each unit cell includes a capacitor that extends at an angle of 45⁰ with respect to a side of the respective unit cell.

42. The reflective intelligent surface of Claim 40, wherein the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 2⁰.

43. The reflective intelligent surface of Claim 40, wherein the metasurface comprises a plurality of unit cells, and each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an angle of about 45⁰ with respect to the first longitudinal axis.

44. The reflective intelligent surface of Claim 43, further comprising a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis to form a first capacitor.Attorney Docket No.9833.7410.WO 45. The reflective intelligent surface of Claim 40, wherein each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular metal ring.

46. The reflective intelligent surface of Claim 40, wherein each unit cell comprises an annular metal ring and the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring.

47. The reflective intelligent surface of Claim 46, wherein each first capacitor comprises facing first and second metal traces on a printed circuit board.

48. The reflective intelligent surface of Claim 45, wherein each first capacitor comprises a first varactor.

49. The reflective intelligent surface of any of Claims 40-48, wherein each unit cell comprises an outer annular metal ring and an inner annular metal ring.

50. The reflective intelligent surface of Claim 49, wherein each inner annular metal ring includes first through fourth varactors.

51. A reflective intelligent surface, comprising: a metasurface comprising a plurality of unit cells, wherein each unit cell comprises a first metal segment having a first longitudinal axis, a second metal segment having a second longitudinal axis that is perpendicular to the first longitudinal axis, and a third metal segment having a third longitudinal axis that forms an oblique angle with the first longitudinal axis.

52. The reflective intelligent surface of Claim 51, wherein the oblique angle is an angle of about 45⁰.

53. The reflective intelligent surface of Claims 51 or 52, further comprising a fourth metal segment having a fourth longitudinal axis that extends in parallel to the third longitudinal axis.Attorney Docket No.9833.7410.WO 54. The reflective intelligent surface of Claim 53, wherein the third and fourth metal segments face each other and are spaced apart from each other by a dielectric material to form a first capacitor.

55. The reflective intelligent surface of Claim 54, wherein each unit cell comprise part of an annular square metal ring and the first and second metal segments of each unit cell comprise part of the annular square metal ring.

56. The reflective intelligent surface of Claim 55, wherein the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular square metal ring.

57. The reflective intelligent surface of Claim 56, wherein each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the first diagonal of the annular square metal ring.

58. The reflective intelligent surface of Claim 57, wherein each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular square metal ring.

59. The reflective intelligent surface of Claim 55, wherein each annular square metal ring is an outer annular square metal ring, and wherein each unit cell further comprises a discontinuous inner annular square metal ring.

60. The reflective intelligent surface of Claim 59, wherein the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

61. A reflective intelligent surface, comprising: a metasurface having a plurality of unit cells, where each unit cell comprises an annular metal ring and a first capacitor that extends at an angle of 45⁰ with respect to a side of the annular square metal ring.

62. The reflective intelligent surface of Claim 61, wherein the first capacitor of each unit cell has a longitudinal axis that extends along a first diagonal of the annular metal ring.Attorney Docket No.9833.7410.WO 63. The reflective intelligent surface of Claim 62, wherein each unit cell further comprises a second capacitor that has a longitudinal axis that extends along the first diagonal of the annular metal ring.

64. The reflective intelligent surface of Claim 63, wherein each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

65. The reflective intelligent surface of Claim 64, wherein each unit cell further comprises a fourth capacitor that has a longitudinal axis that extends along the second diagonal of the annular metal ring.

66. The reflective intelligent surface of Claim 63, wherein each unit cell further comprises a third capacitor that has a longitudinal axis that extends along a second diagonal of the annular metal ring.

66. The reflective intelligent surface of any of Claims 61-65, wherein each first capacitor comprises facing first and second metal traces on a printed circuit board.

68. The reflective intelligent surface of any of Claims 61-65, wherein each first capacitor comprises a varactor.

69. The reflective intelligent surface of any of Claims 61-65, wherein each annular metal ring is an annular square metal ring.

70. The reflective intelligent surface of any of Claims 61-65, wherein a longitudinal axis of the first capacitor of each unit cell has a longitudinal axis that is offset from the diagonals of the respective annular metal rings.

71. The reflective intelligent surface of any of Claims 61-65, wherein the annular square metal rings are outer annular square metal rings, and wherein each unit cell further comprises a discontinuous annular inner metal ring.Attorney Docket No.9833.7410.WO 72. The reflective intelligent surface of Claim 71, wherein the discontinuities in the discontinuous annular inner metal rings comprises gaps between the plates of capacitors of the unit cells.

73. A reflective intelligent surface, comprising: a metasurface having a plurality of unit cells, where each unit cell comprises an outer annular metal ring, an inner annular metal ring having a plurality of discontinuities, and a plurality of circuit elements that span the respective discontinuities in the inner annular metal ring 74. The reflective intelligent surface of Claim 73, wherein plurality of circuit elements comprises a plurality of varactors.

75. The reflective intelligent surface of Claim 73, wherein plurality of circuit elements comprises a plurality of circuit elements that have adjustable reactances.

76. The reflective intelligent surface of any of Claims 73-75, wherein each circuit element extends at an angle of 45⁰ with respect to at least one side of the outer annular metal ring.

77. The reflective intelligent surface of any of Claims 73-75, wherein the metasurface is configured to steer both a horizontal component and a vertical component of an incident RF signal.

78. The reflective intelligent surface of any of Claims 73-75, wherein each outer annular metal ring is an annular square metal ring.

79. The reflective intelligent surface of Claim 78, wherein the circuit elements are positioned along diagonals of the respective outer annular metal rings.

80. The reflective intelligent surface of any of Claims 73-75, wherein the metasurface is configured to steer both the horizontal and vertical components of the incident RF signal the same amount.Attorney Docket No.9833.7410.WO 81. The reflective intelligent surface of Claim 73, wherein the metasurface is configured to adjust reflection angles of both the horizontal and vertical components of the incident RF signal by at least 25⁰.

Images