Radiating elements with META material lenses and related base station antennas

Abstract

Base station antennas are provided that comprise a reflector and a first array of first frequency band radiating elements that are mounted to extend forwardly from the reflector. Each first frequency band radiating element includes first and second dipole radiators and a meta material lens that is mounted forwardly of the first and second dipole radiators.

Description

Attorney Docket No.9833.7190.WO RADIATING ELEMENTS WITH META MATERIAL LENSES AND RELATED BASE STATION ANTENNAS 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 / 512,172, filed July 6, 2023, the entire content of which is incorporated by reference herein. FIELD

[0002] The present invention generally relates to radio communications and, more particularly, to base station antennas for cellular communications systems and to lensed radiating elements for such base station antennas. BACKGROUND

[0003] Cellular communications systems are well known in the art. 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 radio frequency ("RF") communications with subscribers that are positioned throughout the cell served by the base station. The base station antennas are often mounted on a tower or other raised structure, with the radiation pattern ("antenna beam") that is generated by each antenna directed outwardly to serve a respective sector. Typically, a base station antenna includes multiple phase- controlled arrays of radiating elements, with the radiating elements arranged in vertically- extending columns that are referred to as "linear arrays." Herein, "vertical" refers to a direction that is generally perpendicular relative to the plane defined by the horizon. References will alsoAttorney Docket No.9833.7190.WO be made herein to the "azimuth" plane, which refers to a horizontal plane that bisects the base station antenna that is parallel to the plane defined by the horizon.

[0004] Most cells are divided into a plurality of "sectors," and separate base station antennas provide coverage (service) to each of the sectors. The most common base station configuration is the so-called "three sector configuration" in which a cell is divided into three 120º "sectors" in the azimuth plane. In a three sector configuration, the antenna beams generated by the linear arrays typically have half power beamwidths in the azimuth plane ("azimuth HPBW") of about 65º (i.e., the angle subtended in the azimuth plane by the portion of the antenna beam that has a gain that is within 3 dB of the peak gain is about 65⁰). Generally speaking, an antenna beam having an azimuth HPBW of about 65⁰ will provide reasonably good coverage throughout a 120⁰ sector without having excessive spillover of RF energy into adjacent sectors. Such spillover of RF energy into adjacent cells is undesirable both because it reduces the gain of the antenna beam within the sector and because the spillover appears as interference to the antenna beams in the adjacent sectors. Unless noted otherwise, references to an azimuth HPBW of an antenna beam refer to the average azimuth HPBW over the operating frequency band of the array of radiating elements that form the antenna beam (since the azimuth HPBW will vary with frequency).

[0005] Typically, each base station antenna will include multiple linear arrays of radiating elements that operate, for example, using second generation ("2G"), third generation ("3G") or fourth generation ("4G") cellular network protocols. The linear arrays may be "perfect" columns of radiating elements where all of the radiating elements are aligned along a vertically-extending axis, or may be "staggered" columns in which some of the radiating elements are staggered horizontally (and may even be aligned with an adjacent column of radiating elements) in order to reduce (narrow) the azimuth HPBW of the antenna beams generated by the linear arrays. Most modern base station antennas include both "low-band" linear arrays of radiating elements that support service in some or all of the 617-960 MHz frequency band and "mid-band" linear arrays of radiating elements that support service in some or all of the 1427-2690 MHz frequency band. These linear arrays are typically formed using dual-polarized radiating elements, which allows each linear array to transmit and receive RF signals at two orthogonal polarizations.Attorney Docket No.9833.7190.WO

[0006] Each of the above-described linear arrays is coupled to two ports of a radio (one port for each polarization). An RF signal that is to be transmitted by a linear array is passed from the radio port to the antenna where it is divided into a plurality of sub-components, with each sub-component fed to a respective subset of the radiating elements in the linear array (typically each sub-component is fed to between one and three radiating elements). The sub-components of the RF signal are transmitted through the radiating elements to generate an antenna beam that covers a generally fixed coverage area, such as a sector of a cell. Since the antenna beams generated by the above-described 2G / 3G / 4G linear arrays generate static antenna beams, they are often referred to as "passive" linear arrays.

[0007] Most cellular operators are currently upgrading their networks to support fifth generation ("5G") cellular service. One important component of 5G cellular service is the use of so-called "active" beamforming arrays that operate in conjunction with "active" beamforming radios to dynamically adjust the size, shape and pointing direction of the antenna beams that are generated by the active beamforming array. Active beamforming arrays are typically formed using "high-band" radiating elements that operate in higher frequency bands, such as some or all of the 3.1-4.2 GHz and / or the 5.1-5.8 GHz frequency bands, although active beamforming arrays may also be provided that operate in the upper portion of the mid-band frequency range (e.g., 2300-2690 MHz).

[0008] Most modern base station antennas include multiple arrays of radiating elements. For example, most base station antennas include passive linear arrays of both low-band and mid- band radiating elements, and many base station antennas may further include one or more multi- column active beamforming arrays. Moreover, in order to support higher order multi-input- multi-output ("MIMO") communication techniques (e.g., 4xMIMO or 8xMIMO) and / or to provide service in multiple sub-bands of the mid-band frequency range, many base station antennas include multiple (e.g., two or four) low-band and / or mid-band linear arrays.

[0009] While there is commercial interest in base station antennas that have many different arrays of radiating elements, cellular network operators also often have strict limits on the widths of various types of base station antennas. Base station antennas are often mounted on antenna towers hundreds of feet above the ground and can be subject to very high wind levels. As a base station antenna is made wider, the wind loading increases, requiring that the base station antenna, its mounting hardware, and the antenna tower itself have increased structuralAttorney Docket No.9833.7190.WO durability. Thus, as the number of arrays included in a base station antenna is increased, the spacing between the arrays typically must be decreased to keep the width of the antenna within cellular network operator specified limits. Unfortunately, as the spacing between arrays is decreased, the adjacent arrays tend to interact with each other in undesirable ways, which can degrade the performance of the base station antenna. SUMMARY

[0010] Pursuant to embodiments of the present invention, base station antennas are provided that comprise a reflector and a first array of first frequency band radiating elements that are mounted to extend forwardly from the reflector. Each first frequency band radiating element includes first and second dipole radiators and a meta material lens that is mounted forwardly of the first and second dipole radiators.

[0011] In some embodiments, each meta material lens may be a flat meta material lens. In some cases, each meta material lens may be formed in a printed circuit board. Each meta material lens may, for example, comprise a plurality of meta structures. In some embodiments, the meta structures may be arranged to define a ring. In some embodiments, an interior of this ring may be devoid of any meta structures.

[0012] In some embodiments, each first frequency band radiating element further comprises a director mounted forwardly of the first and second dipole radiators. In some embodiments, the meta structures may overlap less than 50% of the director. In some embodiments, the meta structures may overlap less than 75% of the director. In some embodiments, the meta structures may overlap less than 90% of the director. In some embodiments, the meta structures may overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator. In some embodiments, the first dipole radiator may comprise a first dipole arm and a second dipole arm, and the meta structures may overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and may overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

[0013] In some embodiments, the base station antenna may further comprise a second array of second frequency band radiating elements, each second radiating elements mounted to extend forwardly from the reflector and including at least one radiator, where the second frequency band does not overlap the first frequency band. In these embodiments, an insertionAttorney Docket No.9833.7190.WO loss of each meta material lens with respect to RF energy in the second frequency band may be less than 0.2 dB.

[0014] In some embodiments, each meta structure comprises a circular ring. In some embodiments, the first and second dipole radiators of a first of the first frequency band radiating elements may be mounted rearwardly of the at least one radiator and the meta material lens of the first of the first frequency band radiating elements may be positioned forwardly of the at least one radiator.

[0015] In some embodiments, a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band. In some embodiments, a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0. In some embodiments, the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element. In some embodiments, the meta material lens includes an annular ring that has a higher effective dielectric constant than an interior of the annular ring.

[0016] Pursuant to further embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, a director positioned forwardly of the first and second dipole radiators, and a meta material lens positioned forwardly of the director.

[0017] In some embodiments, the meta material lens may be a flat meta material lens.

[0018] In some embodiments, the meta material lens comprises a plurality of meta structures that are arranged to define a ring. In some embodiments, an interior of the ring is devoid of any meta structures.

[0019] In some embodiments, the meta material lens comprises a plurality of meta structures. In some embodiments, each meta structure comprises a circular ring.

[0020] In some embodiments, the meta structures overlap less than 75% of the director or overlap less than 90% of the director. In some embodiments, the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator. In some embodiments, the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of theAttorney Docket No.9833.7190.WO first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

[0021] In some embodiments, a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band. In some embodiments, a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0. In some embodiments, the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element. In some embodiments, the meta material lens includes an annular ring that has a higher effective dielectric constant than an interior of the annular ring.

[0022] Pursuant to still further embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, a director positioned forwardly of the first and second dipole radiators, and a flat lens positioned forwardly of the director, the flat lens including a first region that has a first effective dielectric constant and a second region that is surrounded by the first region that has a second effective dielectric constant that is less than the first effective dielectric constant.

[0023] In some embodiments, the lens comprises a plurality of meta structures that are arranged to define a ring. In some embodiments, each meta structure comprises a circular ring. In some embodiments, the first region is the portion of the lens that includes the plurality of meta structures and the second region is the region within the ring defined by the plurality of meta structures. In some embodiments, an interior of the ring defined by the plurality of meta structures is devoid of any meta structures.

[0024] In some embodiments, the meta structures overlap less than 75%, or less than 90%, of the director. In some embodiments, the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator. In some embodiments, the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.Attorney Docket No.9833.7190.WO

[0025] In some embodiments, a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band. In some embodiments, a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0. In some embodiments, the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element. In some embodiments, the meta material lens includes an annular ring that has a higher effective dielectric constant than an interior of the annular ring.

[0026] Pursuant to yet additional embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, and a meta material lens positioned forwardly of the first and second dipole radiators. The meta material lens including a plurality of meta structures that are arranged to form a ring of meta structures.

[0027] In some embodiments, each meta structure comprises a circular ring. In some embodiments, the first region is the portion of the lens that includes the plurality of meta structures and the second region is the region within the ring defined by the plurality of meta structures. In some embodiments, an interior of the ring is devoid of any meta structures.

[0028] In some embodiments, the meta structures overlap less than 75%, or less than 90%, of the director. In some embodiments, the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator. In some embodiments, the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

[0029] In some embodiments, a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band. In some embodiments, a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0. In some embodiments, the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element. InAttorney Docket No.9833.7190.WO some embodiments, the meta material lens includes an annular ring that has a higher effective dielectric constant than an interior of the annular ring.

[0030] Pursuant to further embodiments of the present invention, base station antennas are provided that comprise a reflector, a first frequency band radiating element that is mounted to extend forwardly from the reflector and that includes a first frequency band radiator, and a second frequency band radiating element that is mounted to extend forwardly from the reflector and that includes a second frequency band radiator. The second frequency band does not overlap the first frequency band, and the first frequency band radiating elements comprises a lens that is mounted forwardly of both the first frequency band radiator and the second frequency band radiator. In some embodiments, the first frequency band radiating element may be part of an array of first frequency band radiating elements and the second frequency band radiating element may be part of an array of second frequency band radiating elements.

[0031] In some embodiments, the lens may be a flat lens. In some embodiments, the lens may be a meta material lens.

[0032] The first frequency band radiating element may further include a director. The director may be positioned between the first frequency band radiator and the second frequency band radiator. An insertion loss of the meta material lens with respect to radio frequency energy in the second frequency band may be less than 0.2 dB or even less than 0.1 dB.

[0033] The meta material lens may comprise a plurality of meta structures that are arranged to define a ring. In some embodiments, an interior of the ring may be devoid of any meta structures. In some embodiments, each meta structure may comprise a circular ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG.1A is a perspective view of a conventional multiband base station antenna.

[0035] FIG.1B is a schematic front view of the conventional base station antenna of FIG.1A with the radome removed that illustrates an antenna assembly of the antenna.

[0036] FIGS.2A and 2B are a schematic front perspective view and a schematic side view, respectively, of a mid-band cross-dipole radiating element according to embodiments of the present invention that may be used in the base station antenna of FIGS.1A-1B.

[0037] FIG.3A is an enlarged partial perspective view of the meta material lens included in mid-band cross-dipole radiating element of FIGS.2A-2B.

[0038] FIG.3B is a front shadow view of the radiating element of FIGS.2A-2B.Attorney Docket No.9833.7190.WO

[0039] FIG.4A is a graph of the insertion loss of the meta material lens of FIG.3 across the 1695-2690 MHz frequency range.

[0040] FIG.4B and 4C are graphs of the 3 dB and 10 dB azimuth beamwidths of a conventional mid-band radiating element as compared to the mid-band radiating element according to embodiments of the present invention of FIGS.2A-2B across the 1695-2690 MHz frequency range.

[0041] FIGS.4D and 4E are graphs of the peak directivity and peak gain, respectively, of a conventional mid-band radiating element as compared to a mid-band radiating element according to embodiments of the present invention of FIGS.2A-2B across the 1695-2690 MHz frequency range.

[0042] FIG.5 is a side perspective view of a mid-band cross-dipole radiating element according to further embodiments of the present invention.

[0043] FIGS.6A-6E are schematic shadow front views of radiating elements according to further embodiments of the present invention that have different meta material lens designs.

[0044] FIG.7 is a schematic perspective view of a meta material lens according to further embodiments of the present invention.

[0045] FIG.8 is a schematic front view of an alternative meta structure design that can be used in the meta material lenses of the radiating elements according to embodiments of the present invention.

[0046] FIG.9A is a schematic front view of a base station antenna according to embodiments of the present invention, with the radome thereof removed.

[0047] FIG.9B is a schematic side view of the base station antenna of FIG.9A DETAILED DESCRIPTION

[0048] While conventional mid-band radiating elements provide acceptable performance, in many applications wireless operators desire antennas that exhibit higher gain within a sector and reduced interference outside of the sector. One way to achieve these goals is to increase the size of the mid-band radiating elements, which will act to reduce the azimuth HPBW beamwidth of the mid-band arrays, resulting in more of the RF energy falling within the sector and less falling outside the sector. Another conventional technique to achieve this goal is to horizontally stagger one or more of the mid-band radiating elements in an array to increase theAttorney Docket No.9833.7190.WO aperture of the array in the azimuth plane. Once again, this technique acts to reduce the azimuth HPBW beamwidth of the mid-band arrays.

[0049] Both of the above techniques, however, have disadvantages. Increasing the size of the mid-band radiating element typically requires that a base station antenna manufacturer add another mid-band radiating element to its inventory of parts, which increases costs. Moreover, since many base station antennas include four mid-band linear arrays, the mid-band arrays are often spaced closely together and if the size of the mid-band radiating elements is increased, isolation between adjacent mid-band arrays will be degraded, which can hurt a number of performance parameters including cross-polarization discrimination, antenna beam shape, azimuth beamwidth and the like. Horizontally staggering one or more of the radiating elements in a mid-band array leads to a similar degradation in the isolation between adjacent mid-band arrays.

[0050] Pursuant to embodiments of the present invention, cross-dipole mid-band radiating elements are provided that can be formed using the feed stalk, dipole radiators and (any) director of a conventional mid-band radiating element yet are capable of generating antenna beams that have narrowed azimuth beamwidths that provide increased directivity and gain. The radiating elements according to embodiments of the present invention also exhibit good impedance matching over a broad frequency range so that the radiating elements have a wide operating frequency band. The mid-band radiating elements according to embodiments of the present invention use meta material based lenses to narrow the generated "element" radiation patterns in both the azimuth and elevation planes, which acts to narrow the azimuth HPBW of the antenna beams generated by an array of these mid-band radiating elements. Advantageously, the meta material lenses may redirect some of the RF energy emitted by the radiating elements that would otherwise fall outside of a sector back into the sector, increasing the gain of the antenna beam while simultaneously reducing the extent that the antenna beam spills over into adjacent sectors.

[0051] Many conventional mid-band cross-dipole radiating elements include a director, which refers to a parasitic element that is mounted in front of the dipole radiators that acts to narrow the azimuth HPBW of the radiating element. The mid-band cross-dipole radiating elements according to embodiments of the present invention may include both a director and a meta material lens that is mounted forwardly of the director. In some cases, the position of theAttorney Docket No.9833.7190.WO director may be modified from the position of the director in the conventional radiating element. For example, the director may be moved to be positioned farther forwardly of the dipole radiating elements than normal.

[0052] In some embodiments, the meta material lenses may be implemented as printed circuit board based lenses that include a dielectric substrate having meta structures printed on one or both major surfaces thereof. The meta structures may be symmetrically disposed on the printed circuit board. In some embodiments, the meta structures may be arranged to extend around a periphery of the meta material lens, and the center of the meta material lens may be devoid of meta structures. For example, the meta structures may form a circular ring with a relatively large open interior. In other embodiments, the meta structures may form a ring that has only a relatively small open interior. For example, the meta structures may be arranged to define a triangle, a square or a pentagon, for example.

[0053] In some embodiments, the meta material lens may include a plurality of meta structures that act to focus RF energy that is incident to the lens. In some cases, the meta structures may be primarily or exclusively positioned around the periphery of the meta material lens, and a center of the meta material lens may be devoid of these meta structures. Such a design may act to narrow the azimuth HPBW by redirecting RF energy that would otherwise fall near the edge of the sector (e.g., just outside the sector) further into the interior of the sector. Simulations indicate that the radiating elements according to embodiments of the present invention may exhibit smaller 3 dB and 10 dB azimuth beamwidths as compared to conventional radiating elements, while also exhibiting improved front-to-back ration, better cross-polarization discrimination performance, lower sidelobe and grating lobe levels, and higher peak directivity and gain values. While the simulations indicate that some degradation in isolation and return loss may occur, it is believed that these degradations may be reduced or likely completely eliminated though minor changes to the design of the meta material lens or the base station antenna.

[0054] While the above-described radiating elements are mid-band radiating elements that are suitable for use in a base station antenna for a three sector configuration, it will be appreciated that meta material lenses may be used to improve the performance of various other radiating elements that are used in other applications. For example, meta material lenses may be used with radiating elements that operate in other frequency bands, such as low-band radiatingAttorney Docket No.9833.7190.WO elements or high-band radiating elements. In addition, smaller meta material lenses may be used that are suitable for use in base station antennas having narrow housings.

[0055] Pursuant to some embodiments of the present invention, base station antennas are provided that comprise a reflector and a first array of first frequency band radiating elements that are mounted to extend forwardly from the reflector. Each first frequency band radiating element includes first and second dipole radiators and a meta material lens that is mounted forwardly of the first and second dipole radiators

[0056] Pursuant to other embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, a director positioned forwardly of the first and second dipole radiators, and a meta material lens positioned forwardly of the director.

[0057] Pursuant to still further embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, a director positioned forwardly of the first and second dipole radiators, and a flat lens positioned forwardly of the director, the flat lens including a first region that has a first effective dielectric constant and a second region that is surrounded by the first region that has a second effective dielectric constant that is less than the first effective dielectric constant.

[0058] Pursuant to yet additional embodiments of the present invention, radiating elements are provided that comprise a first dipole radiator, a second dipole radiator, and a meta material lens positioned forwardly of the first and second dipole radiators, the meta material lens including a plurality of meta structures that are arranged to form a ring of meta structures.

[0059] Before discussing the radiating elements according to embodiments of the present invention it is helpful to discuss the design of a conventional multiband base station antenna.

[0060] FIG.1A is a schematic front view of a conventional multiband base station antenna 1. In the description that follows, the base station antenna 1 and the radiating elements included therein will be described using terms that assume that the base station antenna 1 is mounted for normal use on a tower with a longitudinal axis of the base station antenna 1 extending along a vertical axis and the front surface of the base station antenna 1 mounted opposite the tower pointing toward the coverage area for the base station antenna 1.

[0061] As shown in FIG.1A, the conventional base station antenna 1 is an elongated structure that extends along a longitudinal axis L. The base station antenna 1 may have a tubularAttorney Docket No.9833.7190.WO shape with a generally rectangular cross-section. The base station antenna 1 includes a tubular radome 10 and a top end cap 12. The base station antenna 1 also includes a bottom end cap 14 which includes a plurality of connectors 16 such as RF ports mounted therein. The RF ports 16 extend through the bottom end cap 14. The radome 10, top cap 12 and bottom cap 14 may form an external housing 18 for the antenna 1. An antenna assembly 20 is contained within the external housing 18. The antenna assembly 20 (FIG.1B) may be slidably inserted into the radome 10 from either the top or bottom before the top end cap 12 or bottom end cap 14 are attached to the radome 10.

[0062] FIG.1B is a schematic perspective view of the antenna assembly 20 of base station antenna 1. As shown in FIG.1B, the antenna assembly 20 includes a ground plane structure 22 that includes a metallic surface (e.g., a sheet of aluminium) that serves as a reflector 24 and ground plane for the linear arrays of radiating elements included in the base station antenna 1. Various mechanical and electronic components of the antenna (not shown) may be mounted behind the reflector 24 such as, for example, phase shifters, remote electronic tilt units, mechanical linkages, controllers, diplexers, and the like.

[0063] A plurality of linear arrays of dual-polarized radiating elements are mounted to extend forwardly from the reflector 24. The linear arrays include two linear arrays 30-1, 30-2 that each comprise a respective vertically-extending column of low-band radiating elements 32, and four linear arrays 40-1 through 40-4 that each comprise a respective vertically-extending column of mid-band radiating elements 42. The base station antenna 1 is often referred to as a 2L4H antenna, reflecting that the antenna includes two low-band linear arrays and four higher- band (here mid-band) linear arrays. The RF ports 16 are used to connect the linear arrays 30, 40 to one or more external radios (not shown). Herein, the linear arrays 30-1, 30-2 of low-band radiating elements 32 may also be referred to as the low-band linear arrays 30-1, 30-2, and the linear arrays 40-1 through 40-4 of mid-band radiating elements 42 may also be referred to as the mid-band linear arrays 40-1 through 40-4. It should be noted that herein like elements may be referred to individually by their full reference numeral (e.g., low-band linear array 30-2) and may be referred to collectively by the first part of their reference numeral (e.g., the low-band linear arrays 30).

[0064] In the depicted embodiment, the first low-band linear array 30-1 is positioned between the first and second mid-band linear arrays 40-1, 40-2, and the second low-band linearAttorney Docket No.9833.7190.WO array 30-2 is positioned between the third and fourth mid-band linear arrays 40-3, 40-4. It will be appreciated that base station antenna 1 illustrates one typical layout of arrays of low-band and mid-band linear arrays 30, 40. It will likewise be appreciated that the number and / or types of arrays may be varied from what is shown based on applications and / or customer requirements, as may the positioning of the linear arrays on the reflector and / or the number of radiating elements included in each linear array. For example, the base station antenna 1 could alternatively include one or more planar arrays of high-band radiating elements that replace the second and third linear arrays 40-2, 40-3 of mid-band radiating elements 42.

[0065] The low-band radiating elements 32 may be configured to transmit and receive signals in a first frequency band such as, for example, the 617-960 MHz frequency range or a portion thereof (and most typically, in the 696-960 MHz frequency band). The mid-band radiating elements 42 may be configured to transmit and receive signals in a second frequency band such as, for example, the 1427-2690 MHz frequency range or a portion thereof (and most typically, the 1695-2690 MHz frequency band). The radiating elements 32, 42 may be dual polarized radiating elements (e.g., -45⁰ / +45⁰ cross-dipole radiating elements), and hence each linear array 30, 40 may be used to form a pair of antenna beams, namely an antenna beam for each of the two polarizations at which the dual-polarized radiating elements 32, 42 are designed to transmit and receive RF signals. While not shown in the drawings, the radiating elements 32, 42 may be mounted on feed board printed circuit boards that couple RF signals to and from the individual radiating elements 32, 42. One or more radiating elements 32, 42 may be mounted on each feed board printed circuit board. Cables may be used to connect each feed board printed circuit board to other components of the antenna such as diplexers, phase shifters or the like.

[0066] As will be explained below, embodiments of the present invention are directed to radiating elements that include individual lenses that focus the RF energy emitted by the radiators of the radiating element. The lensed radiating elements disclosed herein may, for example, be used in place of some or all of the mid-band radiating elements 42 of the base station antenna 1 of FIGS.1A-1B.

[0067] FIGS.2A and 2B are a schematic front perspective view and a schematic side view, respectively, of a mid-band cross-dipole radiating element 100 according to embodiments of the present invention. The mid-band radiating element 100 may, for example, be used in place of some or all of the mid-band radiating elements 42 that are included in the base stationAttorney Docket No.9833.7190.WO antenna 1 of FIGS.1A-1B to provide a base station antenna according to embodiments of the present invention. The base station antennas according to embodiments of the present invention may be used, for example, as sector base station antennas in the above-described base stations of a cellular communications network.

[0068] As shown in FIGS.2A-2B, the mid-band radiating element 100 includes a feed stalk 110, a dipole radiator printed circuit board 130, a director 150 and a meta material lens 160. The feed stalk 110 comprises first and second feed stalk printed circuit boards 120-1, 120-2. The two feed stalk printed circuit boards 120-1, 120-2 are arranged perpendicular to each other so that the feed stalk 110 has a cross-shape when viewed from the front.

[0069] Each feed stalk printed circuit board 120-1, 120-2 includes a respective RF feed line 122-1, 122-2 (FIG.2B). Rear portions of each feed stalk printed circuit board 120 may include projections that are inserted through slits in a feed board printed circuit board. Metallized pads on these projections may be soldered to metallized pads (not shown) on the feed board printed circuit board to mechanically mount the radiating element 100 on the feed board printed circuit board and to electrically connect RF transmission lines (not shown) on the feed board printed circuit board to the RF feed lines 122-1, 122-2 on the respective feed stalk printed circuit boards 120-1, 120-2. The RF transmission lines (not shown) on feed board printed circuit board carry RF signals between a pair of feed networks (one for each of two polarizations) and dipole radiators of the radiating element 100. The radiating element 100 may be mounted to extend forwardly from the feed board printed circuit board with the feed stalk printed circuit boards 120 extending perpendicularly to the feed board printed circuit board.

[0070] The dipole radiator printed circuit board 130 comprises a dielectric substrate 132 with a metal pattern formed on a forward surface thereof. The metal pattern forms first and second dipole radiators 140-1, 140-2. The first dipole radiator 140-1 includes first and second dipole arms 142-1, 142-2 that extend collinearly on the dielectric substrate 132 so that the first dipole radiator 140-1 will extend at an angle of -45⁰ with respect to the horizon when the radiating element 100 is mounted for use in a base station antenna. The second dipole radiator 140-2 includes third and fourth dipole arms 142-3, 142-4 that extend collinearly on the dielectric substrate 132 so that the second dipole radiator 140-2 will extend at an angle of +45⁰ with respect to the horizon when the radiating element 100 is mounted for use in a base station antenna. Dipole arms 142-1 and 142-2 of the first dipole radiator 140-1 transmit and receive signalsAttorney Docket No.9833.7190.WO having a slant -45⁰ linear polarization, while dipole arms 142-3 and 142-4 of second dipole radiator 140-2 transmit and receive signals having a slant +45⁰ linear polarization. Each dipole arm 142 has a leaf shape. This allows the physical length of each dipole arm 142 to be less than ¼ of a "center wavelength" corresponding to the center frequency of the operating frequency band for radiating element 100 while allowing the electrical length of each dipole radiator 140 to be about ½ the center wavelength.

[0071] Forward portions of each feed stalk printed circuit board 120 include a pair of projections 126 that are inserted through slits in the dipole radiator printed circuit board 130. Metallized pads on the projections 126 may be soldered to the base of each dipole arm 142 to mechanically mount the dipole radiator printed circuit board 130 on the feed stalk 110 and to electrically connect the RF feed lines 122-1, 122-2 on the feed stalk printed circuit boards 120-1, 120-2 to the respective dipole radiators 140-1, 140-2. Each of the dipole arms 142 are center fed (i.e., bases of the four dipole arms 142 are adjacent each other in the center of the radiating element 100 and the RF feed lines 122 on the feed stalk printed circuit boards 120-1, 120-2 electrically connect to the base of each dipole arm 142).

[0072] The director 150 comprises an electrically floating (i.e., not connected to electrical ground or another voltage source) piece of sheet metal (or other metal element) that is mounted forwardly of the dipole radiator printed circuit board 130 by, for example, a plastic mounting structure (not shown). The director 150 is a "parasitic" element in the sense that it is not connected to an RF signal source and instead operates by "collecting" RF energy emitted by the dipole radiators 140 and then re-radiates this RF energy. The director 150 may, in part, collect RF energy that is emitted by the dipole radiators 140 in undesired directions (e.g., towards neighboring sectors) and the reradiation of this collected RF energy may include more RF energy emitted in desired directions (e.g., within the sector), as is well understood by those of ordinary skill in the art. The director 150 is designed to shape the "element" antenna beams (i.e., the antenna beam generated by a single radiating element 100) emitted by the respective dipole radiators 140-1, 140-2, and are typically designed to narrow the azimuth HPBW of these individual "element" antenna beams. The director 150 has a smaller "footprint" (i.e., the area occupied by the director 150 when viewed from the front) than the footprint of the combination of the four dipole arms 142-1 through 142-4. The director 150 may, for example, be designed to narrow the azimuth HPBW for RF energy in the upper portion of the mid-band frequency rangeAttorney Docket No.9833.7190.WO (e.g., the 2180-2690 MHz frequency range), while having little or no impact on RF energy emitted in the lower portion of the mid-band frequency range.

[0073] The above described elements of mid-band radiating element 100 may be identical to the corresponding elements of the mid-band radiating elements 42 included in the conventional base station antenna 100, except that the director 150 is positioned a different distance forwardly of the dipole radiator printed circuit board 130 in radiating element 100. In particular, in mid-band radiating element 42 the director thereof is positioned 15 mm forwardly of the dipole radiators, while in mid-band radiating element 100 the director 150 is positioned 31 mm forwardly of the dipole radiators 140. This change in the positioning of the director relative to the dipole radiator printed circuit board 130 ensures that the combination of the director 150 and the meta material lens 160 (discussed below) direct the RF energy in the desired directions.

[0074] As shown in FIGS.2A-2B, the meta material lens 160 is positioned forwardly of the director 150. In an example embodiment, the meta material lens 160 may be positioned 36 mm forwardly of the director 150 and 67 mm forwardly of the dipole radiator printed circuit board 130. In example embodiments, the director 150 may be positioned between 0.15 to 0.3 center wavelengths forwardly of the dipole radiator printed circuit board 130 and the meta material lens 160 may be positioned between 0.4 and 0.6 center wavelengths forwardly of the dipole radiator printed circuit board 130, where the center wavelength is the wavelength corresponding to the center frequency of the operating frequency band of radiating element 100. The meta material lens 160 may be a phase shifting surface that acts to adjust the phase of RF energy that is incident on the lens in a manner that acts to focus the RF energy. Thus, the meta material lens 160160 may receive RF radiation from the radiators 140 and the director 150 and may focus that RF energy so that after passing through the meta material lens 160 the antenna beam will have a higher gain.

[0075] FIG.3A is an enlarged partial perspective view of the meta material lens 160 included in mid-band cross-dipole radiating element 100 of FIGS.2A-2B . FIG.3B is a front shadow view of the mid-band radiating element 100. FIGS.3A-3B more clearly show the construction of the meta material lens 160 and its positioning with respect to the dipole radiators 140-1, 140-2 and the director 150 of radiating element 100.

[0076] As shown in FIGS.3A-3B, in some embodiments, the meta material lens 160 may be formed using a printed circuit board 170. The printed circuit board 170 includes aAttorney Docket No.9833.7190.WO dielectric substrate 172 that has a first metallization layer 174-1 formed on a front (major) surface thereof and a second metallization layer 174-2 formed on a rear (major) surface thereof. The first and second metallization layers 174-1, 174-2 include a plurality of meta structures 162 formed therein. Each meta structure 162 comprises a pair of circular rings 164-1, 164-2 that are formed on opposed sides of the dielectric substrate 172 in the respective first and second metallization layers 174-1, 174-2. The two circular rings 164-1, 164-2 may completely overlap, meaning that a projection of each rings onto the dielectric substrate 172 along axes that are perpendicular to the major surfaces of the dielectric substrate 172 will be identical. Herein, two generally co-planar elements "overlap" if an axis that is perpendicular to the planes defined by the co-planar elements pass through both elements. It will be appreciated that while a pair of circular rings 164-1, 164-2 are used to form each meta structure 162 in FIG.3A, embodiments of the present invention are not limited thereto. For example, in other embodiments, only the first metallization layers 174-1 may be provided and each meta structure 162 may be formed as a single circular ring 164-1. The provision of two circular rings 164-1, 164-2 may provide improved impedance matching in some cases. As another example, while the two circular rings 164-1, 164-2 are only capacitively coupled to each other in FIG.3A, it will be appreciated that in other embodiments plated through holes may be provided through the dielectric substrate 172 that galvanically connect the two circular rings 164-1, 164-2.

[0077] The meta structures 162 are arranged about the periphery of the printed circuit board 170 to form a circular ring 166. Each meta structure 162 may be positioned at the same distance from the center of the meta material lens 160. The interior of the ring 166 is devoid of any meta structures 162. Consequently, as can best be seen in the front shadow view of FIG. 3B, the meta structures 162 overlap the outer portion of each dipole arm 142 and do not overlap (or barely overlap) the inner portion of each dipole arm 142 and / or the director 150. By positioning the meta structures 162 around the periphery of the meta material lens 160, it may be possible to achieve relatively equal phase across a large portion of the aperture, which leads to the narrowing of the beamwidth. In an example embodiment, the diameter of each meta structure 162 may be about 1 / 10thof the center wavelength.

[0078] In the embodiment shown in FIGS.3A-3B, the meta structures 162 may be positioned to generally surround the director 150 when the radiating element 100 is viewed from the front so that much of the director 150 does not overlap the meta structures 162. In someAttorney Docket No.9833.7190.WO embodiments, the meta structures 162 may overlap less than 50% of the director 150. In other embodiments, the meta structures 162 may overlap less than 75% of the director 150. In still other embodiments, the meta structures 162 may overlap less than 90% of the director 150. In some embodiments, the meta structures 162 may overlap less than 50% of the first dipole radiator 140-1 and less than 50% of the second dipole radiator 140-2. In some embodiments, the first dipole radiator 140-1 comprises a first dipole arm 142-1 and a second dipole arm 142-2, and the meta structures 162 overlap more of an outer half of the first dipole arm 142-1 than an inner half of the first dipole arm 14212 and overlap more of an outer half of the second dipole arm 142-2 than an inner half of the second dipole arm 142-2.

[0079] While the meta material lens 160 may advantageously focus the RF energy emitted by the dipole radiators 140, the lens 160 will also result in some level of insertion loss, as some amount of the mid-band RF energy incident on meta material lens 160 will be reflected or absorbed by the lens 160. FIG.4A is a graph of the insertion loss of meta material lens 160 that illustrates the impact of such absorption and reflections on the performance of mid-band radiating element 100. The insertion loss reflects how much a signal incident on the lens 160 will actually pass through the lens 160. As shown in FIG.4A, the insertion loss varies from 0.21 dB to 0.75 dB across the 1695-2690 MHz frequency range, with the insertion loss increasing with increasing frequency. This shows that the meta material lens 160 has some negative impact on insertion loss, although this impact is more than offset by the improvement the meta material lens 160 provides in terms of the gain performance for radiating element 100, as will be discussed in further detail below.

[0080] FIG.4B and 4C are graphs of the 3 dB and 10 dB azimuth beamwidths, respectively, of a conventional mid-band radiating element as compared to the mid-band radiating element 100 according to embodiments of the present invention across the 1695-2690 MHz frequency range. In particular, FIGS.4B and 4C illustrate the performance of an array of mid-band radiating elements 100 that is adjacent another array of mid-band radiating elements with no low-band radiating elements present. Simulations show that similar performance is achieved when two additional arrays of mid-band radiating elements 100 and / or two arrays of low-band radiating elements 132 are added to the antenna. The graphs of FIGS.4B and 4C represent the performance when no electronic downtilt has been applied to the mid-band linearAttorney Docket No.9833.7190.WO arrays. Similar performance improvements to that shown in FIGS.4B and 4C are realized when the arrays are subject to electronic downtilt.

[0081] As shown in FIG.4B, the antenna beam generated by an array of the mid-band radiating elements 100 according to embodiments of the present invention has a significantly reduced azimuth HPBW (see curve 180) as compared to the antenna beam generated by an array of the conventional mid-band radiating elements 42 (see curve 182). On average, the azimuth HPBW of the array of radiating elements 100 according to embodiments of the present invention is 13⁰ narrower than the azimuth HPBW of the array of conventional radiating elements 42, and is at least 4⁰ narrower at all frequencies across the 1695-2690 MHz operating frequency range for the radiating elements 100. Moreover, the variation in azimuth HPBW as a function of frequency is also reduced significantly to less than 19⁰, as compared to a variation of over 33⁰ that is present in the antenna beams generated by an array of the conventional radiating elements 42. In the 1.7-2.2 GHz frequency range (which is a frequency range of interest for many cellular operators), the antenna beams generated by an array of radiating elements 100 exhibit less than 2⁰ variation in azimuth HPBW, whereas the antenna beams generated by an array of the conventional radiating elements 42 exhibit a variation in azimuth HPBW of about 22⁰ over this same frequency range, which is more than an order of magnitude increase in variation. This is a very significant performance improvement, as cellular operators generally desire that the azimuth HPBW be relatively stable as a function of frequency.

[0082] As shown in FIG.4C, a similar improvement in performance is seen in azimuth 10 dB beamwidth performance. In particular, the 10 dB azimuth beamwidth of the antenna beam generated by an array of mid-band radiating elements 100 according to embodiments of the present invention (curve 184) is reduced, on average, by about 26⁰ across the 1695-2690 MHz operating frequency band as compared to the 10 dB azimuth beamwidth of the antenna beam generated by an array of conventional radiating elements 42 (curve 186). The variation in the 10 dB azimuth beamwidth as a function of frequency is greater with respect to the antenna beam generated by an array of the mid-band radiating elements 100 according to embodiments of the present invention, which is generally undesirable, but operators are less concerned with the amount of variation in the 10 dB azimuth beamwidth than the amount of variation in the azimuth HPBW, as much lower RF energy levels are implicated.Attorney Docket No.9833.7190.WO

[0083] FIGS.4D and 4E are graphs of the peak directivity and gain, respectively, of an array of conventional mid-band radiating elements 42 as compared to an array of mid-band radiating elements 100 according to embodiments of the present invention of FIGS.2A-2B across the 1695-2690 MHz frequency range.

[0084] As shown in FIG.4D, the array of radiating elements 100 according to embodiments of the present invention (curve 190) exhibits an average peak directivity (i.e., average as a function of frequency across the operating frequency range) that is more than 1.25 dB higher than the average peak directivity of the array of conventional radiating elements 42 (curve 192). Greater increases in peak directivity are seen at higher frequencies, but even at the lower end of the operating frequency band an increase in peak directivity of 0.7 dB is achieved. As shown in FIG.4E, similar improvements are seen in gain performance, with a minimum improvement in gain of more than 1 dB at all frequencies across the operating frequency band. In FIG.4E, curve 194 represents the peak gain of the array of mid-band radiating elements 100 while curve 196 represents the peak gain of the array 40 conventional mid-band radiating elements 42.

[0085] FIG.5 is a side perspective view of a mid-band cross-dipole radiating element 200 according to further embodiments of the present invention. The radiating element 200 is similar to radiating element 100 of FIGS.2A-2B, except that radiating element 200 includes first and second meta material lens 160-1, 160-2. The addition of a second meta material lens 160-2 may increase the amount of focusing of the RF energy emitted by the dipole arms 140-1, 140-2, thereby further narrowing the 3 dB and 10 dB azimuth beamwidths, resulting in further improvements in peak directivity and peak gain. While FIG.5 illustrates a radiating element 200 that includes two meta material lenses 160-1, 160-2, it will be appreciated that in still further embodiments more meta material lenses may be added (e.g., three, four, five or more meta material lenses 160).

[0086] It will be appreciated that many additional modifications may be made to the radiating elements discussed above without departing from the scope of the present invention. FIGS.6A-6E are schematic front shadow views of radiating elements according to further embodiments of the present invention that include other novel meta material lens designs. The radiating elements of FIGS.6A-6E can be used in place of the mid-band cross-dipole radiating elements 100 of FIGS.2A-2B.Attorney Docket No.9833.7190.WO

[0087] As shown in FIGS.6A-6D, in radiating elements according to other embodiments of the present invention, the number of meta structures 162 included in the meta material lens may be changed. In particular, FIG.6A illustrates a radiating element 300 according to embodiments of the present invention that has a meta material lens 360 that includes five meta structures 162 arranged in a ring 366 about the periphery of the lens. FIGS. 6B and 6C illustrate radiating elements 400 and 500 according to further embodiments of the present invention that have meta material lens 460 and 560, respectively, that each include four meta structures 162 arranged in respective rings 466, 566. FIG.6D illustrates a radiating element 600 according to embodiments of the present invention that includes a meta material lens 660 that has three meta structures 162 arranged in a ring 666. As can be seen by comparing FIG.3B to FIGS.6A-6D, as the number of meta structures 162 is reduced, the diameter of the ring defined by the meta structures 162 is also reduced. Thus, while in the meta material lens 160 of FIG.3B the meta structures 162 only overlap the outer halves of the dipole arms 142 and only barely overlap the director 150, in the meta material lens 660 of FIG.6D the meta structures 162 tend to only overlap the inner halves of the dipole arms 142 and exhibit significant overlap with respect to the director 150.

[0088] As can also be seen by comparing FIG.3B with FIGS.6A-6D, meta material lens 360, 460, 560, 660 are smaller than meta material lens 160. It may be advantageous to use radiating elements that include one of the smaller meta material lens 360, 460, 560, 660 when the radiating elements are used in base station antennas having narrow housings (e.g., housings having a width of 430 mm or less).

[0089] Since the meta material lenses 360, 460, 560, 660 have smaller apertures (i.e., the diameter of meta material lenses 360, 460, 560, 660 is smaller than the diameter of meta material lens 160), the meta material lenses 360, 460, 560, 660 will tend to have a smaller impact on the azimuth beamwidth. The smaller meta material lenses 360, 460, 560, 660 tend to have less of a negative effect on the impedance match, and hence meta structures 162 may be included in the central region of the meta material lenses 360, 460, 560, 660. In the larger aperture meta material lens 160, meta structures are omitted in the central portion of the lens (so that only a ring of meta structures 162 is provided about the periphery of the lens 160) in order to improve the impedance match.Attorney Docket No.9833.7190.WO

[0090] FIG.6E is a front shadow view of a radiating element 700 according to still further embodiments of the present invention. The radiating element 700 may be identical to radiating element 100 of FIGS.2A-2B, except that it includes a different meta material lens 760. As shown in FIG.6E, the meta material lens 760 is similar to meta material lens 160, but the meta structures 162 in meta material lens 760 are arranged to define a square having an open interior and hence define a square ring 766 as opposed to a circular ring. Thus, as shown in FIG. 6E, the meta structures 162 may be arranged in different configurations.

[0091] FIG.7 is a front perspective view of a meta material lens 860 according to additional embodiments of the present invention. The meta material lens 860 may be identical to the meta material lens 860 of FIG.3A, except that the center of the printed circuit board 870 of the meta material lens 860 is removed in order to reduce the weight of the radiating element 800.

[0092] FIG.8 is a front view of a meta structure 962 according to further embodiments of the present invention that can be used in any of the above-described radiating elements in place of the meta structures 162 (i.e., the meta structures 162 included in any of the above- described meta material lenses may be replaced with meta structures 962). As shown in FIG.8, the meta structure 962 has a significantly different design than the above-described meta structure 162. In particular, the meta structure 962 takes the form of a conductive ring 970 that includes a plurality of widened segments 972 that are interconnected by narrower trace sections 974. Edge coupling between the widened segments 972 may form capacitors and the narrow trace sections 974 may be meandered trace sections that have high inductance. As such, the conductive ring 970 forms an L-C circuit. A resonance of the L-C circuit may be set so that the conductive ring 970 is transparent to RF energy in certain frequency bands, such as operating frequency bands of other nearby radiating elements in a base station antenna that includes the meta material lenses according to embodiments of the present invention. As such, the meta structures 962, and hence the meta material lenses formed using the meta structures 962, may be "cloaked" (i.e., substantially invisible to) with respect to other radiating elements included in the base station antenna so that the meta material lenses do not negatively impact the performance of other arrays of radiating elements in the antenna.

[0093] FIG.9A is a schematic front view of a base station antenna 1000 according to embodiments of the present invention, with the radome of the base station antenna 1000 removed. FIG.9B is a schematic side view of the base station antenna 1000 of FIG.9A.Attorney Docket No.9833.7190.WO

[0094] As shown in FIGS.9A-9B, the base station antenna 1000 includes a reflector 1024 first and second arrays 1030-1, 1030-2 of low-band radiating elements 1032, and first and second arrays 1040-1, 1040-2 of mid-band radiating elements 1042 that are implemented using the radiating elements 100 according to embodiments of the present invention. The low-band radiating elements 1032 and the mid-band radiating elements 100 are mounted to extend forwardly from the reflector 1024. While in base station antenna 1000 each low-band array 1030 includes three low-band radiating elements 1032 and each mid-band array 1040 includes six mid-band radiating elements 100, it will be appreciated that each array may have any appropriate number of radiating elements. As discussed above with reference to FIGS.2A-3B, each mid- band radiating element 100 comprises first and second dipole radiators 140-1, 140-2, a director 150 that is mounted forwardly of the first and second dipole radiators 140-1, 140-2, and a meta material lens 160 that is mounted forwardly of the director 150.

[0095] The meta material lenses 160 may be flat meta material lenses in some embodiments and may, for example, be implemented using printed circuit boards 170. Each meta material lens 160 may include a plurality of meta structures 162. In some embodiments, each meta structure 162 may be a circular ring. In some embodiments, the meta structure 162 may also be arranged to define a ring 166. In some embodiments, an interior of the ring 166 may be devoid of any meta structures 162.

[0096] As shown best in FIG.9B, the meta material lenses 160 are positioned forwardly of the dipole arms of the low-band radiating elements 132, while the dipole radiators 140 and the director 150 are mounted rearwardly of the low-band radiating elements 132. As such, RF energy emitted by the low-band radiating elements 132 may need to pass through the meta material lenses 160. In some embodiments, an insertion loss of the meta material lens 160 with respect to RF energy emitted by the low-band radiating elements 132 may be low to ensure that the meta material lenses do not have much of an impact on the antenna beams (e.g., gain performance thereof) generated by the low-band arrays 1030. For example, the maximum insertion loss may be less than 0.3 dB, less than 0.2 dB, or even less than 0.1 dB with respect to RF energy emitted by the low-band radiating elements 132.

[0097] In some embodiments, a diameter of the meta material lens 160 may be between 0.4-0.6 a wavelength corresponding to a center frequency of the operating frequency band of the mid-band radiating elements 100. In some embodiments, a ratio of a distance that the metaAttorney Docket No.9833.7190.WO material lens 160 is positioned forwardly of the first and second dipole radiators 140-1, 140-2 to a diameter of the meta material lens 160 is between 0.6 and 1.0. In some embodiments, the director 150 is positioned between 0.15 and 0.3 of a center wavelength forwardly of the first and second dipole radiators 140-1, 140-2.

[0098] As can be seen from FIGS.9A-9B, pursuant to some embodiments of the present invention, base station antennas 1000 are provided that comprise a reflector 1024, a first frequency band radiating element 100 that is mounted to extend forwardly from the reflector 1024 and that includes a first frequency band radiator 140-1, and a second frequency band radiating element 1032 that is mounted to extend forwardly from the reflector 1024 and that includes a second frequency band radiator (e.g., a dipole radiator). The second frequency band does not overlap the first frequency band, and the first frequency band radiating element 100 comprises a lens that is mounted forwardly of both the first frequency band radiator 140-1 and the second frequency band radiator. In some embodiments, the first frequency band radiating element 100 may be part of an array 1040-1 of first frequency band radiating elements and the second frequency band radiating element 1032 may be part of an array 1030-1 of second frequency band radiating elements.

[0099] It will also be appreciated that the meta material lenses disclosed herein may be incorporated into radiating elements that operate in different frequency bands. For example, in other embodiments, radiating elements that include meta material lenses may be provided that operate in the full 1427-2690 MHz frequency range. In other embodiments, the dimensions of the meta material lenses disclosed herein may be scaled further so that the lenses can be incorporated into low-band radiating elements or into high-band radiating elements.

[0100] It will be appreciated that many modifications may be made to the radiating elements discussed above without departing from the scope of the present invention. For example, the dielectric constant and / or the thickness of the dielectric substrate 172 of printed circuit board 170 may be increased so that the meta material lens will perform more focusing. As another example, the diameter of the meta material lens 160 may be increased from what is shown, and / or the diameters of the individual meta structures 162 may be changed. Meta structures having other shapes (e.g., solid circles, or other shaped solid patches, hexagonal rings, octagonal rings, etc., the circular or other shaped rings could include gaps, rings with stubs may also be used).Attorney Docket No.9833.7190.WO

[0101] It will also be appreciated that the meta material lens disclosed herein may be used with a wide variety of radiating element designs, including cross dipole and patch radiating elements and / or with radiating elements that do or do not include directors.

[0102] 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 this 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.

[0103] 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.

[0104] 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.).

[0105] 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.

[0106] Herein, the term "substantially" means within + / - 10%.Attorney Docket No.9833.7190.WO

[0107] 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.

[0108] 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.9833.7190.WO That Which is Claimed is:

1. A base station antenna, comprising: a reflector; and a first array of first frequency band radiating elements, the first frequency band radiating elements mounted to extend forwardly from the reflector; and wherein each first frequency band radiating element comprises first and second dipole radiators and a meta material lens mounted forwardly of the first and second dipole radiators.

2. The base station antenna of Claim 1, wherein each meta material lens is a flat meta material lens.

3. The base station antenna of Claim 1, wherein each first frequency band radiating element further comprises a director mounted between the first and second dipole radiators and the meta material lens.

4. The base station antenna of any of Claims 1-3, wherein each meta material lens comprises a plurality of meta structures that are arranged to define a ring.

5. The base station antenna of Claim 4, wherein an interior of the ring is devoid of any meta structures.

6. The base station antenna of Claim 3, wherein the meta material lens comprises a plurality of meta structures.

7. The base station antenna of Claim 6, wherein the meta structures overlap less than 50% of the director.

8. The base station antenna of Claim 6, wherein the meta structures overlap less than 75% of the director.

9. The base station antenna of Claim 6, wherein the meta structures overlap less than 90% of the director.Attorney Docket No.9833.7190.WO 10. The base station antenna of Claim 6, wherein the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator.

11. The base station antenna of Claim 6, wherein the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

12. The base station antenna of any of Claims 1-3, wherein each meta material lens is formed in a printed circuit board.

13. The base station antenna of any of Claims 1-3, further comprising: a second array of second frequency band radiating elements, each second radiating elements mounted to extend forwardly from the reflector and including at least one radiator, where the second frequency band does not overlap the first frequency band, 14. The base station antenna of any of Claims 1-3, wherein an insertion loss of each meta material lens with respect to radio frequency energy in the second frequency band is less than 0.2 dB.

15. The base station antenna of Claim 13, wherein the first and second dipole radiators of a first of the first frequency band radiating elements are mounted rearwardly of the at least one radiator and the meta material lens of the first of the first frequency band radiating elements is positioned forwardly of the at least one radiator.

16. The base station antenna of Claim 3, wherein each meta structure comprises a circular ring.

17. The base station antenna of any of Claims 1-16, wherein a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band.

18. The base station antenna of Claim 3, wherein a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0.Attorney Docket No.9833.7190.WO 19. The base station antenna of Claim 3, wherein the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

20. A radiating element, comprising: a first dipole radiator; a second dipole radiator; a director positioned forwardly of the first and second dipole radiators; and a meta material lens positioned forwardly of the director.

21. The radiating element of Claim 20, wherein the meta material lens is a flat meta material lens.

22. The radiating element of Claim 21, wherein the meta material lens comprises a plurality of meta structures that are arranged to define a ring.

23. The radiating element of Claim 22, wherein an interior of the ring is devoid of any meta structures.

24. The radiating element of any of Claims 20-23, wherein the meta material lens comprises a plurality of meta structures.

25. The radiating element of Claim 24, wherein the meta structures overlap less than 75% of the director.

26. The radiating element of Claim 24, wherein the meta structures overlap less than 90% of the director.

27. The radiating element of Claim 24, wherein the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator.

28. The radiating element of Claim 24, wherein the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half ofAttorney Docket No.9833.7190.WO the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

29. The radiating element of Claim 24, wherein each meta structure comprises a circular ring.

30. The radiating element of any of Claims 20-23, wherein a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

31. The radiating element of any of Claims 20-23, wherein a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.

0.

32. The radiating element of any of Claims 20-23, wherein the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

33. A radiating element, comprising: a first dipole radiator; a second dipole radiator; a director positioned forwardly of the first and second dipole radiators; and a flat lens positioned forwardly of the director, the flat lens including a first region that has a first effective dielectric constant and a second region that is surrounded by the first region that has a second effective dielectric constant that is less than the first effective dielectric constant.

34. The radiating element of Claim 33, wherein the lens comprises a plurality of meta structures that are arranged to define a ring.

35. The radiating element of Claim 34, wherein the first region is the portion of the lens that includes the plurality of meta structures and the second region is the region within the ring defined by the plurality of meta structures.Attorney Docket No.9833.7190.WO 36. The radiating element of Claim 34, wherein an interior of the ring is devoid of any meta structures.

37. The radiating element of Claim 34, wherein the meta structures overlap less than 75% of the director.

38. The radiating element of Claim 34, wherein the meta structures overlap less than 90% of the director.

39. The radiating element of Claim 34, wherein the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator.

40. The radiating element of any of Claims 34-39, wherein the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

41. The radiating element of any of Claims 34-40, wherein each meta structure comprises a circular ring.

42. The radiating element of any of Claims 33-41, wherein a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

43. The radiating element of any of Claims 33-42, wherein a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.

0.

44. The radiating element of Claim 43, wherein the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

45. A radiating element, comprising: a first dipole radiator;Attorney Docket No.9833.7190.WO a second dipole radiator; a meta material lens positioned forwardly of the first and second dipole radiators, the meta material lens including a plurality of meta structures that are arranged to form a ring of meta structures.

46. The radiating element of Claim 45, wherein the meta material lens is a flat meta material lens.

47. The radiating element of Claim 45, wherein an interior of the ring is devoid of any meta structures.

48. The radiating element of Claim 45, wherein the meta structures overlap less than 75% of the director.

49. The radiating element of Claim 45, wherein the meta structures overlap less than 90% of the director.

50. The radiating element of Claim 45, wherein the meta structures overlap less than 50% of the first dipole radiator and less than 50% of the second dipole radiator.

51. The radiating element of any of Claims 45-50, wherein the first dipole radiator comprises a first dipole arm and a second dipole arm, and the meta structures overlap more of an outer half of the first dipole arm than an inner half of the first dipole arm and overlap more of an outer half of the second dipole arm than an inner half of the second dipole arm.

52. The radiating element of any of Claims 45-50, wherein each meta structure comprises a circular ring.

53. The radiating element of any of Claims 45-50, wherein a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

54. The radiating element of any of Claims 45-50, wherein a ratio of a distance that the meta material lens is positioned forwardly of the first and second dipole radiators to a diameter of the meta material lens is between 0.6 and 1.0.Attorney Docket No.9833.7190.WO 55. The radiating element of Claim 54, wherein the director is positioned between 0.1 and 0.3 of a center wavelength forwardly of the first and second dipole radiators, where the center wavelength is a wavelength corresponding to a center frequency of an operating frequency band of the radiating element.

56. A base station antenna, comprising: a reflector; a first frequency band radiating element that is mounted to extend forwardly from the reflector and that includes a first frequency band radiator; and a second frequency band radiating element that is mounted to extend forwardly from the reflector and that includes a second frequency band radiator; wherein the second frequency band does not overlap the first frequency band, and wherein the first frequency band radiating element comprises a lens that is mounted forwardly of both the first frequency band radiator and the second frequency band radiator.

57. The base station antenna of Claim 56, wherein the lens is a flat lens.

58. The base station antenna of Claim 56, wherein the lens is a meta material lens.

59. The base station antenna of Claim 58, wherein the first frequency band radiating element further includes a director that is positioned between the first frequency band radiator and the second frequency band radiator.

60. The base station antenna of Claim 58, wherein an insertion loss of the meta material lens with respect to radio frequency energy in the second frequency band is less than 0.2 dB.

61. The base station antenna of Claim 58, wherein the meta material lens comprises a plurality of meta structures that are arranged to define a ring.

62. The base station antenna of Claim 61, wherein an interior of the ring is devoid of any meta structures.

63. The base station antenna of Claim 61, wherein each meta structure comprises a circular ring.Attorney Docket No.9833.7190.WO 64. The base station antenna of Claim 61, wherein a diameter of the meta material lens is between 0.4-0.6 a wavelength corresponding to a center frequency of the first frequency band.

65. The base station antenna of Claim 58, wherein the first frequency band radiating element is part of an array of first frequency band radiating elements and the second frequency band radiating element is part of an array of second frequency band radiating elements.

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