Base station antenna having radiating element with stealth director and / or plurality of directors

Abstract

A radiating element includes a first radiator and a first director including first to fourth arms. Each of the first to fourth arms includes a respective metallization pattern extending radially from a central metallization region, and the first arm includes a resonant circuit having at least one inductive element and at least one capacitive element.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. 119 to U.S. Provisional Patent Application No. 63 / 437,160, filed on January 5, 2023, the entire contents of which are incorporated herein by reference as if fully set forth. Technical Field

[0003] The present invention relates generally to radio communications and, more particularly, to base station antennas for cellular communication systems. Background Art

[0004] Cellular communication systems are well known in the art. In a cellular communication system, a geographic area is divided into a series of areas called "cells" that are served by corresponding base stations. A base station may include one or more base station antennas that are configured to provide two-way radio frequency ("RF") communications with mobile users within the cell served by the base station. Typically, the base station antennas are mounted on a tower or other elevated structure, with a radiation pattern (also referred to herein as an "antenna beam") generated by the base station antenna pointing outward. In many cases, each base station is divided into "sectors." In one common configuration, a hexagonal cell is divided into three 120° sectors in the azimuth plane, and each sector is served by one or more base station antennas that generate an antenna beam with an azimuth half-power beamwidth ("HPBW") of approximately 65°, thereby providing good coverage of the entire 120° sector. Base station antennas that provide less than omnidirectional (360°) coverage in the azimuth plane are often referred to as "sector" base station antennas. The antenna beams formed by both omnidirectional and sector base station antennas are typically generated by linear or planar phased arrays of radiating elements included in the antennas.

[0005] To accommodate the growing volume of cellular traffic, cellular operators have been adding cellular services in a variety of new frequency bands. While in some cases, a single array of so-called "wideband" or "ultra-wideband" radiating elements can be used to provide service in multiple frequency bands, in other cases, different arrays of radiating elements must be used to support services in different frequency bands. However, as the operating bandwidth increases, it can become difficult to provide the desired level of antenna directivity across the entire operating band.

[0006] As the number of frequency bands has proliferated, and as increased sectorization has become more common (e.g., dividing a cell into six, nine, or even twelve sectors), the number of base station antennas deployed at a typical base station has increased significantly. However, there are often limits on the number of base station antennas that can be deployed at a given base station due to, for example, local zoning regulations and / or weight and wind load constraints on the antenna tower. To increase capacity without further increasing the number of base station antennas, so-called multi-band base station antennas have been introduced that include multiple arrays of radiating elements. Multi-band base station antennas are currently being developed that include arrays that operate in three (or more) different frequency bands, and typically within multiple sub-bands within one or more of these bands. For example, base station antennas are now being deployed that include two linear arrays of "low-band" radiating elements operating in some or all of the 617-960 MHz frequency band, two linear arrays of "mid-band" radiating elements operating in some or all of the 1427-2690 MHz frequency band, and one or more multi-column (planar) arrays of "high-band" radiating elements operating in some or all of higher frequency bands, such as the 3.3-4.2 GHz band. Unfortunately, the different arrays can interact with each other, which can make it challenging to implement such multi-band antennas while also meeting customer requirements related to the size (particularly width) of the base station antenna. Summary of the Invention

[0007] According to an embodiment of the present invention, a radiating element is provided, comprising a first radiator and a first director comprising first to fourth arms. Each of the first to fourth arms comprises a respective metallization pattern extending radially from a central metallization region, wherein the first arm comprises a resonant circuit comprising at least one inductive element and at least one capacitive element.

[0008] In some embodiments, the first director is configured to be substantially transparent to RF energy within a first sub-band of an operating frequency band of the radiating element.

[0009] In some embodiments, the resonant circuit is configured to resonate with respect to RF energy within a second sub-band of an operating frequency band of the radiating element.

[0010] In some embodiments, the first director is configured to generate surface currents in response to RF energy within a second sub-band of an operating frequency band of the radiating element. In some embodiments, the second sub-band includes lower frequencies than the first sub-band.

[0011] In some embodiments, the radiating element is part of an array of first radiating elements included in a base station antenna, and wherein the first director is configured to be substantially transparent to RF energy within an operating frequency band relative to an array of second radiating elements also included in the base station antenna, wherein the array of first radiating elements operates at a lower frequency than the array of second radiating elements.

[0012] In some embodiments, each metallization pattern includes a plurality of metal segments, and the at least one inductive element includes a metal trace interconnecting two of the metal segments of the first metallization pattern on the first arm, wherein the average width of the metal trace is less than half the average width of the two metal segments. In some embodiments, the metal trace is a serpentine metal trace. In some embodiments, the at least one capacitive element includes edge coupling between the two metal segments of the first metallization pattern on the first arm.

[0013] In some embodiments, the first radiator is a first dipole radiator, wherein the radiating element comprises a cross-dipole radiating element, the cross-dipole radiating element comprises the first dipole radiator and the second dipole radiator, and wherein the first arm and the second arm extend along a first axis extending parallel to the first dipole radiator, and the third arm and the fourth arm extend along a second axis extending parallel to the second dipole radiator.

[0014] In some embodiments, the central metallized region includes a second director configured to reduce an azimuth half-power beamwidth of a radiation pattern emitted by the radiating element within a first sub-band of an operating frequency band of the radiating element.

[0015] In some embodiments, the first to fourth arms of the first director are configured to reduce the azimuth half-power beamwidth of a radiation pattern emitted by the radiating element within a second sub-band of an operating frequency band of the radiating element.

[0016] In some embodiments, each of the first to fourth arms comprises a frequency selective surface. In some embodiments, each frequency selective surface comprises a plurality of unit cell structures.

[0017] In some embodiments, the first director is mounted in front of the radiator.

[0018] In some embodiments, the resonant frequency of the resonant circuit is within the operating frequency band of the radiating element.

[0019] In some embodiments, the radiating element is part of a first array of radiating elements of a base station antenna, and the base station antenna also includes a second array of radiating elements operating in a second operating frequency band, wherein the resonant frequency of the resonant circuit is within the second operating frequency band.

[0020] According to another embodiment of the present invention, radiating elements configured to transmit and receive RF signals in an operating frequency band are provided. The radiating elements include a first radiator and a first director, wherein the first director is configured to be substantially transparent to RF energy in a first sub-band of the operating frequency band, the first sub-band being in an upper portion of the operating frequency band.

[0021] In some embodiments, the first director is configured to generate a surface current in response to RF energy within a second sub-band of the operating frequency band in a lower portion of the operating frequency band.

[0022] In some embodiments, the first director comprises a resonant circuit, the resonant circuit comprising at least one inductive element and at least one capacitive element. In some embodiments, a resonant frequency of the resonant circuit is within the operating frequency band.

[0023] In some embodiments, the first director comprises a plurality of metal segments, and the at least one inductive element comprises a serpentine metal trace interconnecting a first metal segment and a second metal segment of the metal segments. In some embodiments, the at least one capacitive element comprises an edge coupling between the first metal segment and the second metal segment of the metal segments.

[0024] In some embodiments, the radiating element comprises a cross-dipole radiating element, and the first radiator is a first dipole radiator, and the cross-dipole radiating element further comprises a second dipole radiator, and wherein the first director comprises a first arm and a second arm extending along a first axis extending parallel to the first dipole radiator, and a third arm and a fourth arm extending along a second axis extending parallel to the second dipole radiator.

[0025] In some embodiments, the first director is configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiating element in the second sub-band of the operating frequency band, and the radiating element also includes a second director, which is configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiating element in the first sub-band of the operating frequency band.

[0026] In some embodiments, the first director comprises a frequency selective surface. In some embodiments, the frequency selective surface comprises a plurality of unit cells.

[0027] In some embodiments, the first director comprises a conductive ring. In some embodiments, the conductive ring comprises a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces.

[0028] According to another embodiment of the present invention, radiating elements configured to transmit and receive RF signals in an operating frequency band are provided. The radiating elements include: a first radiator; and a first director and a second director, wherein the first director is configured to reduce the azimuth half-power beamwidth of a radiation pattern generated by the first radiator in a lower portion of the operating frequency band; and the second director is configured to reduce the azimuth half-power beamwidth of a radiation pattern generated by the first radiator in an upper portion of the operating frequency band.

[0029] In some embodiments, the first director is configured to be substantially transparent to RF energy in an upper portion of the first operating frequency band.

[0030] In some embodiments, the first director comprises a resonant circuit comprising at least one inductive element and at least one capacitive element. In some embodiments, a resonant frequency of the resonant circuit is within a lower portion of the operating frequency band.

[0031] In some embodiments, the first director comprises a plurality of metal segments, and the at least one inductive element comprises a metal trace interconnecting two of the metal segments, wherein the average width of the metal trace is less than half the average width of the two of the metal segments. In some embodiments, the metal trace is a serpentine metal trace. In some embodiments, the at least one capacitive element comprises edge coupling between two of the metal segments.

[0032] In some embodiments, the radiating element comprises a cross-dipole radiating element comprising the first dipole radiator and the second dipole radiator, and wherein the first director comprises a first arm and a second arm extending along a first axis extending parallel to the first dipole radiator, and a third arm and a fourth arm extending along a second axis extending parallel to the second dipole radiator.

[0033] In some embodiments, the first to fourth arms extend from the second director.

[0034] In some embodiments, the first director comprises a frequency selective surface.

[0035] In some embodiments, the first director comprises a conductive ring. In some embodiments, the conductive ring comprises a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces. In some embodiments, the second director is positioned within the conductive ring.

[0036] According to yet other embodiments of the present invention, a radiating element is provided, comprising: a first radiator; and a first director, the first director being mounted in front of the first radiator, the first director comprising a frequency selective surface. In some embodiments, the frequency selective surface comprises a plurality of unit cell structures. In some embodiments, the frequency selective surface is configured to be substantially transparent to RF energy within a first sub-band of an operating frequency band of the radiating element. In some embodiments, the first sub-band is an upper portion of the operating frequency band of the radiating element.

[0037] According to yet further embodiments of the present invention, cross-dipole radiating elements operating in a first operating frequency band are provided. These radiating elements include: a first dipole radiator; a second dipole radiator extending perpendicular to the first dipole radiator; and a first director, the first director including a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces to form a conductive loop overlapping the first dipole radiator and the second dipole radiator.

[0038] In some embodiments, the cross-dipole radiating element further includes a second director positioned within the conductive loop.

[0039] In some embodiments, the first director is configured to be substantially transparent to RF energy within a first sub-band of the first operating frequency band.

[0040] In some embodiments, the first director is configured to resonate with respect to RF energy within a second sub-band of the first operating frequency band. In some embodiments, the second sub-band includes lower frequencies than the first sub-band. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a perspective view of a base station antenna according to an embodiment of the present invention.

[0042] Figure 2 The radome is removed Figure 1 Front view of a base station antenna.

[0043] Figure 3 The radome is removed Figure 1 Cross-sectional view of a base station antenna.

[0044] Figures 4A-4CThey are the side view, perspective view and front view of a conventional mid-frequency band radiating element.

[0045] Figures 5A-5C They are a side view, a perspective view and a front view, respectively, of a radiating element comprising two directors according to an embodiment of the present invention, wherein at least one of the directors is a stealth director.

[0046] Figure 6 is a front view of a portion of a multi-band base station antenna including a mid-band radiating element with a stealthy director according to an embodiment of the present invention.

[0047] Figure 7A and 7B is a front view of a stealth director according to another embodiment of the present invention.

[0048] Figure 8 is a front view of a director having a frequency selective surface according to another embodiment of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present invention generally relate to radiating elements for base station antennas, and to related base station antennas. A base station antenna comprising a radiating element according to embodiments of the present invention may be used, for example, as a sector antenna in the above-mentioned cellular communication system.

[0050] The radiating elements used in base station antennas typically include parasitic elements known as "directors". As is well understood by those skilled in the art, a director is a "parasitic" device in the sense that it is not connected to an RF signal source, but rather works by "collecting" the RF energy emitted by the active feed element (e.g., a dipole radiator) of the antenna and then re-radiating this RF energy. A director is a metal element used to shape the antenna beam generated by the radiator of the radiating element including the director. In most cases, the director is designed to reduce the azimuth HPBW of each "element" antenna beam generated by the radiator of the radiating element including the director. Each director is typically implemented as an electrically floating (i.e., not electrically grounded) metal sheet that is mounted in front of the radiator of the radiating element via, for example, a plastic support. The director is typically smaller than the radiator and is typically implemented as a square or nearly square metal piece.

[0051] Directors are typically included in mid-band radiating elements operating in the 1427-2690 MHz or 1695-2690 MHz frequency bands. By adding a director to each radiating element in a mid-band linear array, the beamwidth of the generated antenna beam can be narrowed in the azimuth plane, which serves to increase the directivity of the antenna beam.

[0052] Unfortunately, because the mid-band frequency range is so large (the fractional bandwidth of the full 1427-2690 MHz mid-band frequency range is (2690-1427) / 2690=47% fractional bandwidth), it can be difficult to design a director that will improve the directivity of a radiating element across the full mid-band operating frequency band. In particular, if the director is designed to narrow the azimuth beamwidth in the lower portion of the mid-band frequency range, the size of the director becomes large enough that the director can block some of the RF radiation emitted in the upper portion of the mid-band frequency range. Therefore, conventional directors for mid-band radiating elements are designed to narrow the azimuth beamwidth of RF energy in the upper portion of the mid-band frequency range (e.g., the 2180-2690 MHz frequency range). Such directors have little or no effect on the RF energy emitted in the lower portion of the mid-band frequency range. A mid-band radiating element including such a director may have a dipole arm having an electrical length of approximately one-quarter wavelength at frequencies in the lower portion of the mid-band frequency range (rather than having an electrical length of one-quarter wavelength at the center frequency of the mid-band frequency range) because the use of such a physically larger dipole arm increases directivity in the lower portion of the mid-band frequency range. However, increased directivity may be desired throughout the entire mid-band frequency range, particularly in the lower portion of the mid-band frequency range.

[0053] According to embodiments of the present invention, radiating elements are provided that have so-called "stealth" directors that are designed to be substantially transparent to RF energy within a sub-band of the operating frequency band of the radiating element in which the director is included. For example, according to embodiments of the present invention, mid-band radiating elements are provided that have stealth directors that are designed to reduce the azimuth HPBW of RF energy emitted in the lower portion of the mid-band frequency range. The stealth director is substantially transparent to RF energy within the upper portion of the mid-band frequency range. These radiating elements may also include non-stealth directors that are designed to reduce the azimuth HPBW of RF energy emitted in the upper portion of the mid-band frequency range. Thus, radiating elements according to embodiments of the present invention may exhibit improved directivity, particularly in the lower portion of the operating frequency band, without negatively impacting performance in the upper portion of the operating frequency band.

[0054] Additionally, radiating elements according to embodiments of the present invention can also improve the performance of other arrays included in a base station antenna. In particular, a known challenge in the design of multi-band base station antennas is reducing the effects of scattering of RF signals in one frequency band by radiating elements in other frequency bands. Scattering is undesirable because it can affect the shape of the antenna beam in both the azimuth and elevation planes, and this effect can vary significantly with frequency, which can make compensating for these effects difficult. Furthermore, at least in the azimuth plane, scattering often affects the beamwidth, beam shape, pointing angle, gain, and front-to-back ratio of the antenna beam in undesirable ways.

[0055] Dipole-based radiating elements typically have a dipole radiator with an electrical length of approximately 1 / 4 of the wavelength of the center frequency of the designed operating frequency band for the radiating element. 1 / 2 (although as discussed above, there may be some variation in electrical length to achieve desired performance across the entire operating band). The 3.1-4.2 GHz high-band frequency range contains frequencies that are twice as high as the frequencies in the lower portion of the mid-band frequency range. Therefore, RF energy emitted by a high-band radiating element may tend to couple into the dipole arms of a nearby mid-band radiating element because such high-band RF energy will be coupled to the dipole arms of a nearby mid-band radiating element. 1 The antenna array is configured to resonate in a dipole arm having a length of 1 / 2 wavelength. The coupled RF energy generates high-band currents in the mid-band dipole arm, which in turn generate high-band radiation emitted from the mid-band dipole arm. The high-band RF energy emitted from the mid-band dipole arm distorts the antenna beam generated by the high-band array because (1) the radiation is emitted from a different location than expected, and (2) the radiation emitted from the mid-band dipole radiator may be out of phase with the radiation emitted by the high-band radiating element.

[0056] Stealth radiating elements are known in the art and are designed to reduce or eliminate such scattering of RF energy emitted by a higher-band radiating element by the dipole arms of a nearby lower-band radiating element. For example, U.S. Patent No. 9,570,804 discloses a lower-band radiating element comprising a dipole arm formed as a series of RF chokes so as to render the lower-band radiating element substantially transparent to RF energy emitted by a nearby higher-band radiating element. U.S. Patent No. 10,439,285 and U.S. Patent No. 10,770,803 each disclose a lower-band radiating element comprising a dipole arm formed as a series of widened segments connected by narrow inductive segments, which can be implemented as small serpentine trace segments on a printed circuit board. In each case, the narrow inductive segments act as high impedance elements for RF energy in the higher-band, thereby rendering the lower-band radiating element substantially transparent to RF energy in the higher-band. Additional stealth radiating element designs are disclosed in U.S. Patent No. CN 11,018,437, Chinese Patent No. CN 112787061A, Chinese Patent No. 112164869A, Chinese Patent No. CN 112290199A, Chinese Patent No. CN 111555030A, Chinese Patent No. CN112186333A, Chinese Patent No. CN 112186341A, Chinese Patent No. CN 112768895A, Chinese Patent No. CN112821044A, Chinese Patent No. CN 213304351U, Chinese Patent No. CN 112421219A and PCT Publication WO 2021 / 042862.

[0057] While the dipole arms of lower-band radiating elements are often the primary source of the aforementioned scattering phenomenon, applicants have discovered that the directors of lower-band radiating elements can also cause a certain amount of scattering relative to the RF radiation emitted by nearby higher-band radiating elements. Stealth directors according to embodiments of the present invention can be designed to be substantially transparent not only to RF energy within the upper portion of the radiating element's operating frequency band, but also to RF energy emitted by nearby higher-band radiating elements. Thus, stealth directors according to embodiments of the present invention can, for example, improve the performance of both mid-band and high-band arrays of a multi-band base station antenna.

[0058] According to some embodiments of the present invention, a radiating element is provided, comprising a first radiator and a first director comprising first to fourth arms. Each of the first to fourth arms comprises a corresponding metallization pattern extending radially from a central metallization region, and the first arm comprises a resonant circuit comprising at least one inductive element and at least one capacitive element. The first director may be configured to be substantially transparent to RF energy within a first sub-band of an operating frequency band of the radiating element. The resonant circuit may be configured to resonate with respect to RF energy within a second sub-band of the operating frequency band of the radiating element. The second sub-band may include lower frequencies than the first sub-band. In addition, the central metallization region may be a second director configured to narrow the azimuth half-power beamwidth of a radiation pattern emitted by the radiating element within the first sub-band of the operating frequency band of the radiating element.

[0059] According to another embodiment of the present invention, a radiating element is provided, which includes a first radiator and a first director, wherein the first director is configured to substantially transmit RF energy in a first sub-band of an operating frequency band of the radiating element, wherein the first sub-band is in an upper portion of the operating frequency band.

[0060] According to yet other embodiments of the present invention, a radiating element is provided, comprising: a first radiator; and a first director and a second director, wherein the first director is configured to reduce the azimuth half-power beamwidth of the radiation pattern generated by the first radiator in the lower part of the operating frequency band of the radiating element, and the second director is configured to reduce the azimuth half-power beamwidth of the radiation pattern generated by the first radiator in the upper part of the operating frequency band.

[0061] According to still further embodiments of the present invention, there is provided a radiating element comprising a first radiator and a first director mounted in front of the first radiator, the first director comprising a frequency selective surface.

[0062] According to yet other embodiments of the present invention, a radiating element is provided, which includes a first dipole radiator, a second dipole radiator extending perpendicular to the first dipole radiator, and a first director, wherein the first director includes a plurality of widened conductive segments, and the plurality of widened conductive segments are interconnected by a plurality of serpentine conductive traces to form a conductive ring overlapping the first dipole radiator and the second dipole radiator.

[0063] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0064] Figure 1-3 1 shows a base station antenna 100 according to some embodiments of the present invention. Specifically, Figure 1 is a perspective view of the antenna 100, and Figure 2 and Figure 3 1 and 2 are front and cross-sectional views, respectively, of the antenna 100 with its radome removed to illustrate the antenna assembly 200 of the antenna 100. In the following description, the antenna 100 and the radiating elements included therein will be described using the following terms that assume that the antenna 100 is mounted on a tower for normal use, wherein the longitudinal axis of the antenna 100 extends along a vertical axis and the front surface of the antenna 100 is mounted opposite the tower pointing toward the coverage area of the antenna 100.

[0065] like Figure 1-3 As shown in , the base station antenna 100 is an elongated structure extending along a longitudinal axis L. The base station antenna 100 may have a tubular shape with a generally rectangular cross-section. The antenna 100 includes a radome 110 and a top cover 120. The antenna 100 also includes a bottom cover 130, which includes a plurality of connectors 140, such as RF ports, mounted therein. When the antenna 100 is mounted for normal operation, the antenna 100 is typically mounted in a vertical configuration (i.e., the longitudinal axis L may be generally perpendicular to a plane defined by a horizon). The radome 110, the top cover 120, and the bottom cover 130 may form an outer housing for the antenna 100. The antenna assembly 200 is contained within the outer housing. The antenna assembly 200 may be slidably inserted into the radome 110 from the top or bottom before the top cover 120 or the bottom cover 130 is attached to the radome 110.

[0066] Figure 2 and Figure 3 They are respectively a front view and a cross-sectional view of the antenna assembly 200 of the base station antenna 100. Figure 2 and Figure 3 , the antenna assembly 200 includes a ground plane structure 210 having sidewalls 212 and a reflector surface 214. Various mechanical and electronic components (not shown) of the antenna, such as phase shifters, remote electronic tilt units, mechanical linkages, controllers, duplexers, etc., can be mounted in a cavity defined between the sidewalls 212 and the back side of the reflector surface 214. The reflector surface 214 of the ground plane structure 210 can include or comprise a metal surface (e.g., an aluminum sheet) that acts as a reflector and a ground plane for the radiating elements of the antenna 100. The reflector surface 214 may also be referred to herein as the reflector 214.

[0067] The dual-polarized radiating elements are mounted to extend forward from the reflector 214. The radiating elements include a low-band radiating element 224, a mid-band radiating element 234, and a high-band radiating element 244. The low-band radiating elements 224 are mounted in two columns to form two linear arrays 220-1 and 220-2 of the low-band radiating elements 224. It should be noted that when a plurality of like or similar elements are provided, they may be labeled in the drawings using two-part reference numerals (e.g., linear arrays 220-1, 220-2). Such elements may be referred to herein individually by their full reference numerals (e.g., linear array 220-2) and collectively by the first part of their reference numerals (e.g., linear array 220). The mid-band radiating elements 234 may also be mounted in two columns to form two linear arrays 230-1 and 230-2 of the mid-band radiating elements 234. A first and second planar arrays 240-1, 240-2 of high-band radiating elements 244 are included in the antenna 100, each planar array including four columns 242 of high-band radiating elements 244. All four columns 242 of high-band radiating elements 244 in each high-band array 240 can be coupled to four corresponding ports of a corresponding first beamforming radio device and a second beamforming radio device (not shown). Thus, each high-band array 240 can perform active beamforming to generate a higher gain antenna beam. In this document, the linear arrays 220-1, 220-2 of low-band radiating elements 224 may also be referred to as low-band linear arrays 220-1, 220-2, the linear arrays 230-1, 230-2 of mid-band radiating elements 234 may also be referred to as mid-band linear arrays 230-1, 230-2, and the arrays 240-1, 240-2 of high-band radiating elements 244 may also be referred to as high-band arrays 240.

[0068] In the depicted embodiment, the two high-band arrays 240-1, 240-2 are positioned between the two low-band arrays 220-1, 220-2, and each linear array 220 of low-band radiating elements 224 is positioned between the high-band arrays 240-1, 240-2 and a respective one of the mid-band linear arrays 230-1, 230-2. The antenna 100 illustrates one typical layout of arrays of low-band radiating elements, mid-band radiating elements, and high-band radiating elements. Many other array configurations are typically used based on the application and customer requirements. Therefore, it should be understood that the number of arrays of low-band radiating elements, mid-band radiating elements, and / or high-band radiating elements can vary. Figure 2 and Figure 3The number of columns and / or the number of radiating elements in each array, as well as the relative positions of the arrays, may also vary from those shown in FIG. For example, the two high-band arrays 240 may be omitted in another exemplary embodiment or replaced by two additional mid-band linear arrays 230. Radiating elements according to embodiments of the present invention may be used in arrays having any suitable configuration.

[0069] The low-band radiating element 224 can be configured to transmit and receive signals in a first frequency band. In some embodiments, the first frequency band may include the 617-960 MHz frequency range or a portion thereof (e.g., the 617-896 MHz frequency band, the 696-960 MHz frequency band, etc.). The mid-band radiating element 234 can be configured to transmit and receive signals in a second frequency band. In some embodiments, the second frequency band may include the 1427-2690 MHz frequency range or a portion thereof (e.g., the 1695-2690 MHz frequency band, the 1710-2200 MHz frequency band, the 2300-2690 MHz frequency band, etc.). The high-band radiating element 244 can be configured to transmit and receive signals in a third frequency band. In some embodiments, the third frequency band may include the 3100-4200 MHz frequency range or a portion thereof. The two low-band linear arrays 220-1, 220-2 may or may not be configured to transmit and receive signals in the same portion of the first frequency band. For example, in one embodiment, the low-band radiating elements 224 in the first linear array 220-1 can be configured to transmit and receive signals in the 700 MHz frequency band, and the low-band radiating elements 224 in the second linear array 220-2 can be configured to transmit and receive signals in the 800 MHz frequency band. In other embodiments, the low-band radiating elements 224 in both the first and second linear arrays 220-1, 220-2 can be configured to transmit and receive signals in the same frequency band, for example, to support the use of multiple-input multiple-output ("MIMO") communication technology. The mid-band and high-band radiating elements 234, 244 in the different mid-band and high-band arrays 230, 240 can similarly have any suitable configuration. The radiating elements 224, 234, 244 can be dual-polarized radiating elements (e.g., -45° / +45° cross-dipole radiating elements or -45° / +45° polarized patch radiating elements), and therefore, each array 220, 230, 240 can be used to form a pair of antenna beams, that is, the dual-polarized radiating elements are designed to transmit and receive one antenna beam for each of the two polarizations of RF signals.

[0070] Although not shown in the figure, the radiating elements 224, 234, 244 can be mounted on a feed board that couples RF signals to and from each radiating element 224, 234, 244. One or more radiating elements 224, 234, 244 can be mounted on each feed board. Cables can be used to connect each feed board to other components of the antenna, such as a duplexer, phase shifter, etc.

[0071] As discussed above, mid-band radiating elements (e.g., radiating element 234) typically include a director for narrowing the azimuth HPBW of the generated "element" radiation pattern (i.e., the antenna beam generated by the individual radiating element). However, in practice, the director may only be designed to narrow the element radiation pattern for RF energy in the upper portion of the mid-band frequency range (e.g., the 2180-2690 MHz frequency range or the 2300-2690 MHz frequency range). As a result, these conventional radiating elements may exhibit less than desirable directivity values in the lower portion of the mid-band frequency range.

[0072] Figures 4A-4C A conventional mid-band radiating element 300 is shown that includes a director that narrows the azimuth beamwidth only in the upper portion of the mid-band frequency range. In particular, Figure 4A is a side view of the radiating element 300, Figure 4B is a perspective front view of the radiating element 300, and Figure 4C 3 is a front view of the radiation element 300. The radiation element 300 includes a feeding stem 310, first and second dipole radiators 320-1, 320-1, and a director 340.

[0073] The first feed handle 310-1 of the feed handles may include a front slot, and the second feed handle 310-2 of the feed handles may include a rear slot. These slots allow the two feed handles 310 to be assembled together to form a forward-extending column with a generally X-shaped vertical cross-section. The rear portion of each feed handle 310 may include a protrusion that is inserted through a slot in the feed plate 246 to mount the radiating element 300 thereon. The feed plate 246 may be mounted on the reflector 214 of the base station antenna. In some embodiments, each feed handle 310 may include a printed circuit board having RF transmission lines formed thereon. These RF transmission lines transmit RF signals between the feed plate 246 and the dipole radiator 320. The dipole radiator 320 is mounted at the front end of the feed handle 310. The RF transmission lines can provide center feed to the dipole radiators 320-1 and 320-2.

[0074] In the depicted embodiment, the first and second dipole radiators 320-1, 320-2 are formed using a dipole radiator printed circuit board 322 and sheet metal dipole arm extensions 334-1 to 334-4. The first dipole radiator 320-1 includes first and second dipole arms 330-1, 330-2, and the second dipole radiator 320-2 includes third and fourth dipole arms 330-3, 330-4. Figure 4B and Figure 4C As shown in FIG, the dipole radiators 320-1, 320-2 can be implemented in a "cross" arrangement to form a pair of center-fed -45 ° / +45 ° Dipole radiator 320. The inner portion 332 of each dipole arm 330 can be formed on the dipole radiator printed circuit board 322. The inner portion 332 of each dipole arm 330 can be capacitively coupled to a corresponding one of the dipole arm extensions 334. The inner portion 332 of each dipole arm 332 and the dipole arm extension 334 to which it is capacitively coupled together form a corresponding dipole arm 330-1 to 330-4.

[0075] A director 340 is mounted in front of the dipole radiator 320. The director 340 may comprise a flat sheet of stamped metal. A plastic support (not shown) may be used to secure the director 340 in place. The director 340 is substantially smaller than the dipole radiator 320. The director 340 extends further in the horizontal plane than in the vertical plane, which allows the director to narrow the radiation pattern generated by its associated dipole radiator 320 more in the azimuth plane than in the elevation plane.

[0076] Director 340 is designed to reduce the azimuth beamwidth of the radiation pattern generated by its associated dipole radiator 320 within the 2180-2690 MHz frequency range. Director 340 has minimal impact on the radiation pattern generated by its associated dipole radiator 320 within the 1427-1980 MHz frequency range. Directors with slightly different dimensions can be used to target specific sub-ranges within the 2180-2690 MHz frequency range. The distance at which director 340 is mounted in front of dipole radiator 320 can be set to tune the shape of the radiation pattern in the azimuth plane.

[0077] The director 340 can effectively narrow the azimuth beamwidth in the upper portion of the mid-band frequency range. For example, simulations indicate that the radiating element 300 exhibits a 71.6 ° The average azimuth HPBW is compared to that of the azimuth HPBW, which shows 64.9 in the frequency range of 2300-2690MHz. 0The larger dipole arm 330 helps provide 58.6 in the 1427-1518 MHz frequency range. 0 However, in all three frequency ranges and specifically in the 1427-1518 MHz and 1695-2180 MHz bands, a smaller azimuth HPBW would be desirable.

[0078] The radiating element 300 is discussed in detail in U.S. Patent Publication No. 2022 / 0190470, filed on September 25, 2021, the entire contents of which are incorporated herein by reference. Therefore, further description of the radiating element 300 will be omitted here.

[0079] According to an embodiment of the present invention, a radiating element is provided, the radiating element having a director configured to narrow the azimuth beamwidth of a radiation pattern generated by a dipole radiator of the radiating element in a first portion of an operating frequency band of the radiating element, while substantially transmitting more RF energy in a second portion of the operating frequency band of the radiating element. For example, the director can be configured to narrow the azimuth beamwidth of a radiation pattern generated by a dipole radiator of the radiating element in a lower portion of the operating frequency band of the radiating element, while substantially transmitting RF energy in an upper portion of the operating frequency band. Such a director can improve the shape and / or directivity of an antenna beam generated by the dipole radiator in the lower portion of the operating frequency band without adversely affecting the radiation pattern generated by the radiating element in the upper portion of the operating frequency band.

[0080] In some embodiments, the radiating element may include both a first director and a second director. As discussed above, the first director may be a "stealth" director that is configured to improve the shape and / or directivity of the antenna beam generated by the dipole radiator in the lower portion of the operating frequency band without adversely affecting the radiation pattern generated by the radiating element in the upper portion of the operating frequency band. The second director may be, for example, a director that is designed to narrow the azimuth beamwidth of the radiation pattern generated by the dipole radiator of the radiating element in the upper portion of the operating frequency band of the radiating element. Thus, radiating elements according to embodiments of the present invention may provide improved performance compared to conventional radiating elements.

[0081] In some embodiments, the radiating element can be a mid-band radiating element configured to operate in the 1427-2690 MHz frequency band. In such embodiments, the first director can be configured to, for example, reduce the azimuth beamwidth of the radiation pattern generated by the RF signal in the 1427-1920 MHz frequency range, while the second director can be configured to, for example, reduce the azimuth beamwidth of the radiation pattern generated by the RF signal in the 2180-2690 MHz frequency range. In some embodiments, the first director and the second director can be implemented as an integral director element, such as a director printed circuit board or a metal plate. The central portion of the director element can serve as the second director (and can also serve as a part of the first director), and the outer portion of the director element can serve as the remainder of the first director.

[0082] Now refer to Figure 5A-8 Examples of radiating elements including a stealth director and / or a first director and a second director according to embodiments of the present invention are discussed. While these exemplary embodiments describe mid-band radiating elements, it should be understood that embodiments of the present invention are not limited thereto. For example, in other embodiments, the radiating element may be a high-band radiating element having a first director and a second director configured to act as directors in different portions of the high-band frequency range (wherein one or both of the directors may be stealth directors).

[0083] Figures 5A-5C An exemplary radiating element 400 according to an embodiment of the present invention is shown. In particular, Figure 5A is a side view of the radiation element 400, Figure 5B is a perspective view of the radiating element 400, and Figure 5C is a front view of the radiation element 400.

[0084] The radiating element 400 may be Figures 4A-4C The radiating element 400 is similar or identical to the radiating element 300, except that the radiating element 400 may include a director element 440 instead of the director 340 included in the radiating element 300. Therefore, the same reference numerals are used to identify components of the radiating element 400 that may be identical to corresponding elements of the radiating element 300, and further discussion of these elements will be omitted.

[0085] In the depicted embodiment, the director element 440 is implemented on a director printed circuit board 450. The director printed circuit board 450 may include a dielectric substrate 452 having a metal pattern 458 printed on a first side thereof. The metal pattern 458 is formed on the dielectric substrate 452. The metal pattern 458 includes a center section 454 and first to fourth arms 456-1 to 456-4 extending outwardly from the center section 454. The arms 456-1 to 456-4 are arranged at +45 °、+135 ° 、-135 ° and -45 ° The first and second arms 456-1 and 456-2 extend from the center section 454 at an angle of . Thus, the first and second arms 456-1 and 456-2 extend along a first axis extending parallel to the first dipole radiator 320-1, and the third and fourth arms 456-3 and 456-4 extend along a second axis extending parallel to the second dipole radiator 320-2. The metal pattern 458 forms a first director 460 and a second director 470. The director printed circuit board 450 is mounted in front of the first and second dipole radiators 320-1 and 320-2. Thus, the first and second directors 460 and 470 are mounted in front of the first and second dipole radiators 320-1 and 320-2.

[0086] The second director 470 includes a metallization pattern formed in the central section 454 of the director printed circuit board 450. The second director 470 is configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiating element 400 within the first (upper) sub-band of the operating frequency band of the radiating element 400. In some embodiments, the second director 470 may have the same shape and size as the director 340 included in the radiating element 300, wherein the only difference between the two directors 340, 470 is that the second director 470 is implemented as metallization on the printed circuit board, while the director 340 is implemented using a metal plate (and may be a thicker metal layer than the second director 470).

[0087] First director 460 is configured to be visible to RF energy within the lower portion of the operating frequency band of radiating element 400. Thus, in response to such radiation, surface currents are generated on first director 400, and these surface currents generate RF radiation from first director 460 in the lower portion of the operating frequency band. First director 460 is configured so that the RF radiation emitted therefrom in the lower portion of the operating frequency band serves to reduce the azimuth half-power beamwidth of the radiation pattern emitted by radiating element 400 in the lower portion of the operating frequency band. Additionally, first arm 456-1 through fourth arm 456-4 are configured to be substantially transparent to RF energy within the first (upper) sub-band of the operating frequency band of radiating element 400. Thus, first director 460 is substantially transparent to RF energy within the first (upper) sub-band of the operating frequency band of radiating element 400 because the only portion of first director 460 that is visible to RF energy within the first (upper) sub-band of the operating frequency band is the portion thereof that serves as second director 470.

[0088] The first orienter 460 includes the remainder of the metallization pattern on the orienter printed circuit board 450, including four metallization arms 456-1 to 456-4. In addition, the metallization pattern formed in the center section 454 of the orienter printed circuit board 450 can serve as both the second orienter 470 and a portion of the first orienter 460. Therefore, the first metal arm 456-1 to the fourth metal arm 456-4 form the first orienter 460 in conjunction with the center section 454. As can be seen, the metallization pattern forming each arm 456 includes a first widened metal segment and a second widened metal segment 462-1, 462-2, as well as three narrow metal segments 464-1 to 464-3. The first narrow metal segment 464-1 electrically connects the center section 454 to the first widened metal segment 462-1. The second narrow metal segment 464-2 electrically connects the first widened metal segment 462-1 to the second widened metal segment 462-2. The third narrow metal segment 464-3 extends outward from the third widened metal segment 462-3. Thus, on each arm 456, the first and second widened metal segments 462-1, 462-2, and the first to third narrow metal segments 464-1, 464-3 are electrically connected in series to the central segment 454 and extend outward from the central segment 454 along the axis.

[0089] The first widened metal segment and the second widened metal segment 462-1, 462-2 may each have a first average width (where the width direction is perpendicular to the longitudinal axis of the arm 456), and the three narrow metal segments 464-1 to 464-3 may each have a second average width. In some embodiments, the first average width of at least some of the first widened metal segment and the second widened metal segment 462-1, 462-2 may be at least two times, at least three times, at least four times, or at least five times the second average width of at least some of the three narrow metal segments 464-1 to 464-3.

[0090] Each narrow metal segment 464 is implemented as a serpentine segment, such that the length of the segment (if stretched into a straight line) is much longer than the width of the segment. Therefore, the inductance of each narrow metal segment 464 can be much greater than the inductance of the widened metal segment 462. In addition, because the narrow metal segments 464 are formed as U-shaped metal segments, the two widened metal segments 462 on each arm 456 can be very close to each other, so that the two widened conductive segments 462, together with a portion of the central segment 454, appear as a single continuous metal arm at frequencies within the lower portion of the operating frequency range of the radiating element 400. The narrowed serpentine segment 464 acts as a high-impedance segment that interrupts currents in the upper portion of the operating frequency range of the radiating element 400 that would otherwise be induced on the arm of the first director 460. In other words, each arm 456 can act as a low-pass (or band-pass) filter that allows currents in the lower portion of the operating frequency range to form on the arm 456 while attenuating currents in the upper portion of the operating frequency range. Each arm 456 may include a corresponding resonant circuit having at least one inductive element (e.g., serpentine narrow metal segment 464) and at least one capacitive element (e.g., fringe capacitance between widened metal segments 462 and / or between widened metal segments 462 and narrow metal segments 464). Each resonant circuit may be configured to resonate within the operating frequency band of the radiating element 400. For example, each resonant circuit may be configured to resonate with respect to RF energy within a second sub-band (e.g., a lower sub-band) of the operating frequency band of the radiating element.

[0091] Therefore, the RF energy emitted by the radiating element 400 in the lower portion of the operating frequency band will induce currents on the first director 460, and these currents will cause the RF energy to be radiated from the first director 460. The first director 460 is positioned so that when the RF energy emitted by the dipole radiators 320-1, 320-2 reaches the first director 460, the RF energy emitted by the dipole radiators 320-1, 320-2 is substantially in phase with the RF energy emitted by the first director 460. The phase difference ψ between the current I1 flowing in one of the dipole arms 330 and the current I2 flowing in the corresponding arm of the first director 460 can be determined as follows:

[0092] ψ=π+arctan(x 21 / R 21 )–arctan(x 11 / R 11 )

[0093] where x 21 is the imaginary component of the mutual impedance between the dipole arm 330 and the metal arm of the first director 440, R 21 is the real component of the mutual impedance between the dipole arm 330 and the metal arm of the first director 440, x11 is the imaginary component of the self-impedance of the metal arm of the first director 440, and R 11 is the real component of the self-impedance of the metal arm of the first director 440 .

[0094] Based on the above formula, the phase difference between I1 and I2 can be adjusted by changing the self-impedance value and the mutual impedance value. The phase difference can be adjusted to increase the directivity of the radiating element 400. For example, the mutual impedance can be changed by changing the distance between the dipole radiator 320 and the director printed circuit board 450. The self-impedance of the first director 460 can be changed, for example, by changing the size or size of the first director 460, or the shape or size of the metal segment forming the first director 460. Therefore, the radiating element 400 can be designed so that when the RF energy is combined, the RF energy emitted by the corresponding metal arms of the dipole radiator 320 and the first director 460 is in phase (or at least relatively close to being in phase). When this occurs, the first director 460 serves to focus the RF energy, thereby reducing both the azimuth beamwidth and the elevation beamwidth of the element pattern of the radiating element 400, thereby increasing the directivity of the RF radiation emitted by the radiating element 400 relative to the RF energy in the lower portion of the operating frequency band of the radiating element 400. Furthermore, the first director 460 has minimal effect on the radiation pattern generated by its associated dipole radiator 320 in the upper portion of the operating frequency band (e.g., it does not partially block radiation in this band), and therefore, the first director 460 does not serve to degrade the performance of the radiating element 400 in the upper portion of the operating frequency band.

[0095] Radiating element 400 exhibits improved performance compared to conventional radiating element 300. For example, simulations indicate that radiating element 400 exhibits 63.3 ° The average azimuth HPBW of the radiating element 300 is 1.6 narrower than the average azimuth HPBW of the radiating element 300 in this portion of the operating frequency band. ° The simulation also indicates that the radiating element 400 exhibits a power of 69.1 in the 1695-2180 MHz frequency band. ° The average azimuth HPBW of the radiating element 300 is 2.5 narrower than the average azimuth HPBW of the radiating element 300 in this portion of the operating frequency band. ° The simulation also indicates that the radiating element 400 exhibits a 55.4 ° The average azimuth HPBW of the radiating element 300 is 3.2 narrower than the average azimuth HPBW of the radiating element 300 in this portion of the operating frequency band. °Due to these narrowed azimuth HPBWs, the directivity of radiating element 400 is greater than that of radiating element 300 by 0.27 dBi, 0.15 dBi, and 0.1 dBi in the 1427-1518 MHz, 1695-2180 MHz, and 2300-2690 MHz frequency bands, respectively.

[0096] As discussed above, the mid-band radiating element 400 may exhibit improved performance compared to a comparable conventional radiating element 300. However, when the radiating element 400 is used in a multi-band base station antenna, the use of a stealth director may also improve the performance of nearby arrays operating in higher frequency bands. This may be referred to as Figure 6 See.

[0097] In particular, Figure 6 1 is a front view of a portion of a multi-band base station antenna 500 according to an embodiment of the present invention, wherein the multi-band base station antenna includes a mid-band linear array implemented using the mid-band radiating element 400 described above. The base station antenna 500 may be similar to the one described above with reference to FIG. Figure 1-3 The base station antenna 100 discussed above differs primarily in that (1) the base station antenna 500 includes four linear arrays 230 of mid-band radiating elements, rather than the two mid-band arrays 230 included in the base station antenna 100, and (2) the mid-band radiating elements are implemented using the mid-band radiating elements 400 described above. Figure 1-3 The same reference numerals used in the drawings are used to mark the same components, and further description of these components is omitted.

[0098] As described above, the high-band radiating element 244 is designed to operate in the 3.1-4.2 GHz frequency band. Therefore, the RF energy emitted by the high-band radiating element 244 will tend to resonate with respect to structures resonating in the lower portion of the 1427-2690 MHz operating frequency band of the mid-band radiating element. Therefore, if the first director 460 included in the mid-band radiating element 400 is not a stealthy director, the RF energy emitted by the high-band radiating element 244 will induce currents in the arms of the first director 460 because the mid-band radiating element 400 is mounted very close to the high-band radiating element 244. However, because the first director 460 may be substantially invisible to the RF energy emitted by the high-band radiating element 244, the mid-band radiating element 400 may have a reduced impact on the radiation pattern of the high-band array 240.

[0099] Figure 7A and 7B FIG. 1 is a front view of a radiation element with a stealth director according to another embodiment of the present invention. Figure 7AAs shown in FIG, the director element 600 includes a conductive ring formed on a director printed circuit board 610. The director element 600 may be used, for example, in place of the director element 440 of the radiating element 400.

[0100] like Figure 7A As shown in FIG, the director element 600 includes a metallization pattern 622 on a surface (or multiple surfaces) of a dielectric substrate 612 of a director printed circuit board 610. The metallization pattern 622 forms a first director 620. The metallization pattern 622 may include a plurality of relatively wide metal segments 624 that are physically and electrically connected to each other via a plurality of relatively narrow metal traces 626. In an exemplary embodiment, the average thickness of the relatively wide metal segments 624 may be at least two times, at least three times, at least four times, or at least five times the average thickness of the relatively narrow metal traces 626. As shown, at least some of the relatively narrow metal traces 626 may be implemented as serpentine trace segments, which allows the length of the relatively narrow metal traces 626 to be significantly increased (compared to the width of the traces) while still allowing adjacent metal segments in the relatively wide metal segments 624 to be positioned in close proximity to each other. The fringe capacitance between the relatively wide metal segments 624 and the relatively narrow metal traces 626, as well as the inductance of the relatively narrow metal traces 626, can be selected to form a filter that passes RF current in the lower portion of the operating frequency band of, for example, a radiating element including director element 600, while attenuating RF current in the upper portion of the operating frequency band of the radiating element. In other words, first director 620 can function like a low-pass filter tuned to have a transition between a passband and a stopband within the operating frequency band of the radiating element including first director 620. Thus, first director 620 can perform the same function as first director 460 of radiating element 400. In the depicted embodiment, relatively wide metal segments 624 are implemented as serpentine segments that allow the length of these segments to be substantially greater than their width. In this way, relatively wide metal segments 624 can also contribute to the inductance of the filter formed by first director 600.

[0101] Figure 7B It is for Figure 7A A front view of a modified version of director element 600 is shown, showing director element 600A. As can be seen, director element 600A may be identical to director element 600, except that director element 600A further includes a second director 630 implemented in the middle of the conductive loop of first director 620. Second director 630 may have the same design as second director 470 of radiating element 400 and may perform the same functions as second director 470 of radiating element 400. Therefore, further description of director element 600A will be omitted.

[0102] According to another embodiment of the present invention, a director for a radiating element is provided that is implemented as a frequency selective surface. A frequency selective surface is a conductive structure (usually metal) comprising a plurality of unit cells. The frequency selective surface can be visible to RF energy within some frequency ranges while being substantially transparent to RF energy within other frequency ranges.

[0103] As described above, in some cellular frequency bands, including the mid-band frequency range and the high-band frequency range, it can be difficult to design a director that focuses RF energy in the lower portion of the operating band in the azimuth plane because the size of the director required to perform such focusing is sufficiently large that the director serves to block some of the RF energy in the upper portion of the operating band. However, by fabricating a director that focuses RF energy in the lower portion of the operating band using a frequency selective surface that is substantially transparent to RF energy in the upper portion of the operating band, it is possible to form a director that focuses RF energy in the lower portion of the operating band without negatively impacting the performance of radiating elements in the upper portion of the operating band.

[0104] Figure 8 2 is a front view of a director element 700 formed as a frequency selective surface according to another embodiment of the present invention. The director element 700 can be used, for example, in place of the director element 440 of the radiating element 400.

[0105] like Figure 8As shown in FIG, the director element 700 includes a metallization pattern 722 on a surface (or multiple surfaces) of a dielectric substrate 712 of a director printed circuit board 710. The metallization pattern 722 forms a first director 720. The metallization pattern 722 may include a plurality of unit cells 724, each of which may have a length and width less than one-tenth of a frequency in the operating frequency band of the radiating element including the director element 700. Each unit cell 724 may include a separate metallization structure arranged to form a capacitor and an inductor. Thus, each unit cell 724 may include one or more resonant circuits. As will be understood by those skilled in the art, the resonant circuits of the unit cells 724 are configured to provide a desired frequency response. The desired frequency response may be one in which the unit cells are substantially transparent to RF energy in the upper portion of the operating frequency band of the radiating element including the director 700, while being visible to RF energy in the lower portion of the operating frequency band of the radiating element including the director 700. The size of the first director 720 may be selected so that the first director resonates with RF energy in the lower portion of the operating frequency band. Therefore, the RF energy in the lower portion of the operating frequency band emitted by the dipole radiator of the radiating element can form an RF current on the first director 720, which in turn causes the RF radiation from the first director 720 to be in phase with the RF energy emitted by the dipole radiator of the radiating element including the first director 720. This serves to reduce the HPBW of the antenna beam generated by the radiating element in the azimuth plane for the RF signal in the lower portion of the operating frequency band.

[0106] It should be understood that Figure 8 An exemplary frequency selective surface is shown. Various frequency selective surfaces are known in the art, and any suitable frequency selective surface design may be used to implement a director according to an embodiment of the present invention. It should also be understood that many frequency selective surfaces are multi-layer frequency selective surfaces, and such multi-layer frequency selective surfaces may replace Figure 8 The exemplary embodiment shown uses a single-layer frequency selective surface.

[0107] While the embodiments of the present invention discussed above include a passive director mounted in front of a dipole radiator, it should be understood that embodiments of the present invention are not limited thereto. In particular, in other embodiments, the director may be positioned behind the dipole radiator (i.e., between the dipole radiator and the reflector). In this position, the director acts as a reflector rather than a director and can again be designed to increase the directivity of the radiating element.

[0108] While the director described above is implemented using a printed circuit board, it should be understood that embodiments of the present invention are not limited thereto. For example, in other embodiments, any of the above-described director can be implemented using sheet metal or a combination of sheet metal and printed circuit board elements. In such embodiments, the director can be formed by stamping a suitably shaped structure from sheet metal.

[0109] It should be understood that radiating elements according to embodiments of the present invention are not limited to dipole arms having the shape of the above-described dipole arm 330. Instead, the dipole arm may have any suitable shape, such as a linear shape, a circular shape, an oval shape, a square shape, etc.

[0110] Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the present invention may 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. Throughout, like reference numerals represent like elements.

[0111] It will be understood that although the terms first, second, etc. can 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 element. For example, without departing from the scope of the present invention, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0112] It will be understood that when an element is described as being "on" another element, the element can be directly on the other element, or there can be an intermediate element. Conversely, when an element is described as being "directly on" another element, there are no intermediate elements. It will also be understood that when an element is described as being "connected" or "coupled" to another element, the element can be directly connected or coupled to the other element, or there can be an intermediate element. Conversely, when an element is described as being "directly connected" or "directly coupled" to another element, there are no intermediate elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (i.e., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0113] Relative terms, such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe the relationship of one element, layer or region to another element, layer or region, as illustrated in the figures. It is to be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0114] In this context, the term "substantially" means within + / - 10%.

[0115] The terms used in this document are for the purpose of describing specific embodiments only and are not intended to limit the present 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 also be understood that the terms "including," "comprising," and / or "having," when used herein, refer to the presence of the recited 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 groupings thereof.

[0116] Aspects and elements of all of the embodiments disclosed above may be combined in any manner and / or with aspects or elements of other embodiments to provide multiple additional embodiments.

Claims

1. A radiating element, comprising: a first radiator; as well as A first director includes first to fourth arms, wherein each of the first to fourth arms includes a respective metallization pattern extending radially from a central metallization region, wherein the first arm includes a resonant circuit having at least one inductive element and at least one capacitive element.

2. The radiating element of claim 1 , wherein the first director is configured to be substantially transparent to radio frequency ("RF") energy within a first sub-band relative to an operating frequency band of the radiating element.

3. The radiating element of claim 2, wherein the resonant circuit is configured to resonate with respect to RF energy within a second sub-band of an operating frequency band of the radiating element.

4. The radiating element of claim 2, wherein the first director is configured to generate a surface current in response to RF energy within a second sub-band of an operating frequency band of the radiating element. The radiating element of claim 4 , wherein the second sub-band comprises lower frequencies than the first sub-band.

6. A radiating element according to any one of claims 1-5, wherein the radiating element is part of an array of first radiating elements included in a base station antenna, and wherein the first director is configured to be substantially transparent to radio frequency ("RF") energy within an operating frequency band relative to an array of second radiating elements also included in the base station antenna, wherein the array of first radiating elements operates at a lower frequency than the array of second radiating elements.

7. The radiating element according to any one of claims 1 to 5, wherein each metallization pattern comprises a plurality of metal segments, and the at least one inductive element comprises a metal trace interconnecting two of the metal segments of the first metallization pattern on the first arm, and wherein the average width of the metal trace is less than half the average width of both of the two metal segments. The radiating element of claim 7 , wherein the metal trace is a serpentine metal trace.

9. The radiating element of claim 7, wherein the at least one capacitive element comprises an edge coupling between two metal segments of a first metallization pattern on the first arm.

10. The radiating element of claim 2, wherein the first radiator is a first dipole radiator, wherein the radiating element comprises a crossed dipole radiating element, the crossed dipole radiating element comprising the first dipole radiator and a second dipole radiator, and wherein the first arm and the second arm extend along a first axis extending parallel to the first dipole radiator, and the third arm and the fourth arm extend along a second axis extending parallel to the second dipole radiator.

11. The radiating element of claim 10, wherein the central metallized region comprises a second director configured to narrow the azimuth half-power beamwidth of a radiation pattern emitted by the radiating element within a first sub-band of an operating frequency band of the radiating element.

12. The radiation element according to claim 11, wherein the first arm to the fourth arm of the first director are configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiation element within the second sub-band of the operating frequency band of the radiation element.

13. The radiating element according to any one of claims 1 to 5, wherein the first to fourth arms each comprise a frequency selective surface. The radiating element according to claim 13 , wherein each frequency selective surface comprises a plurality of unit cell structures.

15. The radiation element according to any one of claims 1 to 5, wherein the first director is installed in front of the radiator.

16. The radiation element according to any one of claims 1 to 5, wherein a resonant frequency of the resonant circuit is within an operating frequency band of the radiation element.

17. A radiating element according to any one of claims 1-5, wherein the radiating element is part of a first array of radiating elements of a base station antenna, and the base station antenna also includes a second array of radiating elements operating in a second operating frequency band, wherein the resonant frequency of the resonant circuit is within the second operating frequency band.

18. A radiating element configured to transmit and receive radio frequency ("RF") signals in an operating frequency band, comprising: a first radiator; as well as A first director is configured to substantially transmit RF energy in a first sub-band of the operating frequency band, the first sub-band being in an upper portion of the operating frequency band.

19. The radiating element of claim 18, wherein the first director is configured to generate surface currents in response to RF energy within a second sub-band of the operating frequency band in a lower portion of the operating frequency band.

20. The radiating element of claim 18, wherein the first director comprises a resonant circuit comprising at least one inductive element and at least one capacitive element.

21. The radiation element according to claim 20, wherein a resonant frequency of the resonant circuit is within the operating frequency band.

22. The radiating element of claim 20, wherein the first director comprises a plurality of metal segments, and the at least one inductive element comprises a serpentine metal trace interconnecting a first metal segment and a second metal segment of the metal segments.

23. The radiating element of claim 22, wherein the at least one capacitive element comprises edge coupling between a first metal segment and a second metal segment of the metal segments.

24. The radiating element of any one of claims 18-23, wherein the radiating element comprises a cross-dipole radiating element, and the first radiator is a first dipole radiator, and the cross-dipole radiating element further comprises a second dipole radiator, and wherein the first director comprises a first arm and a second arm extending along a first axis extending parallel to the first dipole radiator, and a third arm and a fourth arm extending along a second axis extending parallel to the second dipole radiator.

25. The radiating element according to claim 24, wherein the first director is configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiating element in the second sub-band of the operating frequency band, and the radiating element further comprises a second director, and the second director is configured to reduce the azimuth half-power beamwidth of the radiation pattern emitted by the radiating element in the first sub-band of the operating frequency band.

26. The radiating element of any one of claims 18-23, wherein the first director comprises a frequency selective surface.

27. The radiating element of claim 26, wherein the frequency selective surface comprises a plurality of unit cells.

28. The radiating element of any one of claims 18-23, wherein the first director comprises a conductive ring.

29. The radiating element of claim 28, wherein the conductive loop comprises a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces.

30. A radiating element configured to transmit and receive radio frequency ("RF") signals in an operating frequency band, the radiating element comprising: a first radiator; as well as A first director and a second director, wherein the first director is configured to reduce the azimuth half-power beamwidth of the radiation pattern generated by the first radiator in the lower part of the operating frequency band, and the second director is configured to reduce the azimuth half-power beamwidth of the radiation pattern generated by the first radiator in the upper part of the operating frequency band.

31. The radiating element of claim 30, wherein the first director is configured to be substantially transparent to RF energy in an upper portion of the first operating frequency band.

32. The radiating element of claim 30, wherein the first director comprises a resonant circuit comprising at least one inductive element and at least one capacitive element.

33. The radiating element of claim 32, wherein the resonant frequency of the resonant circuit is within a lower portion of the operating frequency band.

34. A radiating element according to claim 32, wherein the first director comprises a plurality of metal segments, and the at least one inductive element comprises a metal trace interconnecting two of the metal segments, wherein the average width of the metal trace is less than half the average width of both of the two metal segments.

35. The radiating element of claim 34, wherein the metal trace is a serpentine metal trace.

36. The radiating element of Claim 35, wherein the at least one capacitive element comprises edge coupling between two of the metal segments.

37. A radiating element according to any one of claims 30-36, wherein the radiating element comprises a cross-dipole radiating element, the cross-dipole radiating element comprises the first dipole radiator and the second dipole radiator, and wherein the first director comprises a first arm and a second arm extending along a first axis extending parallel to the first dipole radiator, and a third arm and a fourth arm extending along a second axis extending parallel to the second dipole radiator.

38. The radiating element of claim 37, wherein the first to fourth arms extend from the second director.

39. The radiating element of any one of claims 30-36, wherein the first director comprises a frequency selective surface.

40. The radiating element of any one of claims 30-36, wherein the first director comprises a conductive ring.

41. The radiating element of claim 40, wherein the conductive loop comprises a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces.

42. The radiating element of claim 40, wherein a second director is positioned inside the conductive ring.

43. A radiating element, comprising: a first radiator; as well as A first director is installed in front of the first radiator, and the first director includes a frequency selective surface.

44. The radiating element of claim 43, wherein the frequency selective surface comprises a plurality of unit cell structures.

45. A radiating element according to claim 43 or claim 44, wherein the frequency selective surface is configured to be substantially transparent to radio frequency ("RF") energy within a first sub-band of an operating frequency band of the radiating element.

46. The radiating element of claim 45, wherein the first sub-band is an upper portion of an operating frequency band of the radiating element.

47. A cross-dipole radiating element operating in a first operating frequency band, comprising: first dipole radiator; a second dipole radiator, the second dipole radiator extending perpendicularly to the first dipole radiator; as well as A first director includes a plurality of widened conductive segments interconnected by a plurality of serpentine conductive traces to form a conductive loop overlapping the first dipole radiator and the second dipole radiator.

48. The radiating element of claim 47, further comprising a second director positioned within the conductive ring.

49. The radiating element of claim 47, wherein the first director is configured to be substantially transparent to radio frequency ("RF") energy within a first sub-band relative to the first operating frequency band.

50. The radiating element of claim 49, wherein the first director is configured to resonate with respect to RF energy within a second sub-band of the first operating frequency band.

51. The radiating element of claim 50, wherein the second sub-band comprises lower frequencies than the first sub-band.

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