Radiating element with masked feed handle and base station antenna comprising such radiating element

Abstract

A cross-dipole radiating element includes a feed shank having a base and a distal end positioned forward of the base; a first dipole radiator mounted at the distal end of the feed handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; and a second dipole radiator mounted at the distal end of the feed handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm. The feed stem includes a first ground line and a first signal trace at least partially overlapping the first ground line. The first ground line includes at least a first widened conductive segment, a second widened conductive segment, and a third widened conductive segment, where the first widened conductive segment and the second widened conductive segment are connected by a first narrowed conductive trace, and the second widened conductive segment and the third widened conductive segment are connected by a second narrowed conductive trace.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 437,146, filed on January 5, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to radio communications and, more particularly, to base station antennas for cellular communication systems and to radiating elements for such base station antennas. 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 configured to provide two-way radio frequency ("RF") communication with mobile users within the cell served by the base station. Typically, the base station antenna is mounted on a tower or other elevated structure, with the radiation pattern (also referred to herein as an "antenna beam") generated by the outward-pointing base station antenna. In many cases, each cell is divided into multiple smaller areas in the horizontal or "azimuth" plane, each of which is referred to as a "sector." 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 "sector" base station antennas that generate an antenna beam with an azimuth half-power beamwidth ("HPBW") of approximately 65° to provide good coverage of the entire 120° sector. The antenna beam is generated by a single or multiple phased arrays of radiating elements included in the antenna. The radiating element is typically mounted to extend forwardly from a metallic reflector which acts as a ground plane for the radiating element and serves to reflect backward-directed RF radiation emitted by the radiating element backwardly in a forward direction.

[0005] To accommodate the growing volume of cellular traffic, cellular operators have been adding cellular services in a variety of new frequency bands. To support services in these new frequency bands, most base station antennas are implemented as multi-band antennas, which have different arrays of radiating elements that support services in different frequency bands. To further increase capacity, cellular operators are interested in increasing the number of arrays included in many base station antenna designs. Unfortunately, the radiating elements in different arrays can interact with each other, which can make it challenging to add additional arrays to existing multi-band antennas while also meeting customer requirements related to the size (particularly width) of the base station antenna. Summary of the Invention

[0006] According to an embodiment of the present invention, a cross-dipole radiating element is provided, comprising: a feeding handle having a base and a distal end positioned in front of the base; a first dipole radiator mounted at the distal end of the feeding handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; and a second dipole radiator mounted at the distal end of the feeding handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm. The feeding handle comprises a first ground line and a first signal trace that at least partially overlaps the first ground line. The first ground line comprises at least a first widened conductive segment, a second widened conductive segment, and a third widened conductive segment, wherein the first widened conductive segment and the second widened conductive segment are connected by a first narrowed conductive trace, and the second widened conductive segment and the third widened conductive segment are connected by a second narrowed conductive trace.

[0007] In some embodiments, the average width of the first narrowed conductive trace can be less than half the average width of the first widened conductive segment.

[0008] In some embodiments, the feeding handle may further include a second grounding wire, the second grounding wire including at least a fourth widened conductive segment, a fifth widened conductive segment and a sixth widened conductive segment, wherein the fourth widened conductive segment and the fifth widened conductive segment are connected by a third narrowed conductive trace, and the fifth widened conductive segment and the sixth widened conductive segment are connected by a fourth narrowed conductive trace. In some embodiments, the first grounding wire may extend forward along substantially the entire length of the feeding handle, and the first grounding wire may further include a first branch extending toward the second grounding wire, and the second grounding wire may extend forward along substantially the entire length of the feeding handle, and the second grounding wire may further include a second branch extending toward the first grounding wire. In some embodiments, the average width of the first branch may be smaller than the average width of the first widened conductive segment. In some embodiments, the first branch may extend from the second narrowed conductive trace.

[0009] In some embodiments, the respective lengths of the first to third widened conductive segments may vary by less than 25%.

[0010] In some embodiments, the first signal trace may completely overlap the first narrowed conductive trace and may completely overlap the second narrowed conductive trace.

[0011] In some embodiments, the average width of the second leg can be less than the average width of the fourth widened conductive segment, and the second leg can extend from the fourth narrowed conductive trace.

[0012] In some embodiments, the first single track line may include a first forward extending segment, a second lateral extending segment, and a third rearward extending segment, wherein one of the first forward extending segment, the second lateral extending segment, and the third rearward extending segment includes a zigzag segment. In some embodiments, the first forward extending segment may include the zigzag segment.

[0013] In some embodiments, the first narrowed conductive trace may include a meandering segment.

[0014] In some embodiments, the feed handle may include a feed handle printed circuit board, and the first signal trace may be a first metallization pattern on a first side of the feed handle printed circuit board, and the first ground line may be a second metallization pattern on a second side of the feed handle printed circuit board.

[0015] According to another embodiment of the present invention, a cross-dipole radiating element is provided, comprising: a feed handle having a base and a distal end positioned forward of the base; a first dipole radiator mounted at the distal end of the feed handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; and a second dipole radiator mounted at the distal end of the feed handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm. The feed handle comprises a first ground wire and a first signal trace, wherein the first signal trace comprises a first forward-extending segment, a second laterally-extending segment, and a third segment. In addition, one of the first forward-extending segment, the second laterally-extending segment, and the third segment comprises a meandering segment.

[0016] In some embodiments, the zigzag section may include at least one U-shaped section. In some embodiments, the first forwardly extending segment may include the zigzag section.

[0017] In some embodiments, the first ground line may include a first widened conductive segment and a second widened conductive segment connected by a first narrowed conductive trace. In such embodiments, the average width of the first narrowed conductive trace may be less than half the average width of the first widened conductive segment. The first narrowed conductive trace may include a meandering segment.

[0018] In some embodiments, the first signal trace may completely overlap the first narrowed conductive trace.

[0019] In some embodiments, the feed handle may include a feed handle printed circuit board, and the first signal trace may be a first metallization pattern on a first side of the feed handle printed circuit board, and the first ground line may be a second metallization pattern on a second side of the feed handle printed circuit board.

[0020] In some embodiments, the first ground line may extend along a longitudinal direction of the feeding handle printed circuit board, and include a first branch line extending along a transverse direction of the feeding handle printed circuit board.

[0021] In some embodiments, the first leg may extend from the first narrowed conductive trace.

[0022] In some embodiments, the average width of the first branch line may be smaller than the average width of the first widened conductive segment.

[0023] According to another embodiment of the present invention, a cross-dipole radiating element is provided, comprising: a feeding handle having a base and a distal end positioned forward of the base; a first dipole radiator mounted at the distal end of the feeding handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; and a second dipole radiator mounted at the distal end of the feeding handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm. The feeding handle comprises a first ground line and a first signal trace. In addition, the first ground line comprises a first widened conductive segment and a second widened conductive segment connected by a first narrowed conductive trace, the first narrowed conductive trace comprising a first meandering section.

[0024] In some embodiments, the first meandering section may include a U-shaped section.

[0025] In some embodiments, the average width of the first narrowed conductive trace can be less than half the average width of the first widened conductive segment.

[0026] In some embodiments, the first single trace may include a first forward-extending segment, a second laterally-extending segment, and a third rearward-extending segment, wherein one of the first forward-extending segment, the second laterally-extending segment, and the third rearward-extending segment may include a second zigzag segment.

[0027] In some embodiments, the first forwardly extending segment may include the second tortuous segment.

[0028] In some embodiments, the feed handle may further include a second ground line including at least a third widened conductive segment and a fourth widened conductive segment connected by a second narrowed conductive trace.

[0029] In some embodiments, the first grounding wire can extend forward along substantially the entire length of the feeding handle, the first grounding wire can also include a first branch extending toward the second grounding wire, and the second grounding wire can extend forward along substantially the entire length of the feeding handle, and the second grounding wire can also include a second branch extending toward the first grounding wire.

[0030] In some embodiments, the first leg may extend from the first narrowed conductive trace.

[0031] In some embodiments, the first signal trace may at least partially overlap the first narrowed conductive trace and may completely overlap the second narrowed conductive trace.

[0032] In some embodiments, the third segment may be a rearwardly extending segment.

[0033] According to yet another embodiment of the present invention, a base station antenna is provided, comprising: a frequency selective surface; an array of lower-frequency-band radiating elements positioned in front of the frequency selective surface; and a multi-column array of higher-frequency-band radiating elements positioned behind the frequency selective surface. At least one of the lower-frequency-band radiating elements comprises a pair of dipole radiators, a first feeder cable, and a second feeder cable, wherein the first feeder cable and the second feeder cable extend forward from the frequency selective surface to be directly attached to the respective first and second dipole radiators.

[0034] In some embodiments, the diameter of the first feeder cable is less than 1.68 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1A is a schematic perspective view of a conventional crossed-dipole radiating element.

[0036] Figure 1B yes Figure 1A Schematic side view of a conventional crossed-dipole radiating element.

[0037] Figure 2A is a schematic perspective view of a passive / active antenna system including a passive base station antenna according to an embodiment of the present invention, which may be implemented using a low-band radiating element.

[0038] Figure 2B yes Figure 2A Schematic front view of a passive / active antenna system without its radome.

[0039] Figure 3A is a schematic perspective view of a low-frequency band radiation element according to an embodiment of the present invention.

[0040] Figure 3B and 3C yes Figure 3A A schematic plan view of a first main surface and a second main surface of a feed handle printed circuit board included in a radiating element.

[0041] Figure 3D It shows Figure 3B and 3C Schematic shaded plan view of the metallization on both sides of the feed handle printed circuit board.

[0042] Figure 4A is a schematic perspective view of a low-frequency band radiation element according to another embodiment of the present invention.

[0043] Figure 4B and 4C yes Figure 4A A schematic plan view of a first main surface and a second main surface of a feed handle printed circuit board included in a radiating element.

[0044] Figure 4D It shows Figure 4B and 4C Schematic shaded plan view of the metallization on both sides of the feed handle printed circuit board.

[0045] Figure 5 is a schematic side view of an array of radiating elements according to further embodiments of the present invention. DETAILED DESCRIPTION

[0046] As discussed above, providing a relatively narrow base station antenna with an array of radiating elements operating in several different frequency bands can be challenging. This is particularly true if the antenna includes a beamforming array, such as an eight-column array of high-band radiating elements coupled to a beamforming radio. The width of a multi-band base station antenna can be reduced by reducing the spacing between radiating elements of adjacent arrays. However, as the spacing between arrays decreases, the coupling between radiating elements of different arrays increases, which may, for example, cause RF signals at one frequency band to be "scattered" by radiating elements of other frequency bands. Scattering is undesirable because it can change the shape of the antenna beam in both the azimuth and elevation planes, and the change in the shape of the antenna beam can vary significantly with frequency. This can make it difficult to compensate for the effects of scattering using other techniques. For example, scattering tends to negatively impact the beamwidth, beam shape, pointing angle, gain, and front-to-back ratio of the antenna beam in the azimuth plane.

[0047] Scattering primarily occurs when the conductive structure of a first-band radiating element has an electrical length that causes the structure to resonate in the operating band of a nearby radiating element operating in a second (different) frequency band. For example, most modern base station antennas include both a "low-band" radiating element operating in the 617-960 MHz band or a portion thereof and a "mid-band" radiating element operating in the 1427-2690 MHz band or a portion thereof. If crossed-dipole radiating elements are used, each low-band dipole radiator is typically implemented as a pair of dipole arms, each having an electrical length of approximately 1 / 4 wavelength (referred to herein as the "center wavelength") corresponding to the center frequency of the operating band of the low-band radiating element. Thus, the electrical length of each dipole radiator is approximately 1 / 2 of the "center" wavelength.

[0048] Because the mid-band frequency range encompasses frequencies twice as high as those in the low-band frequency range, the electrical length of each low-band dipole arm can be approximately 1 / 2 wavelength of an RF signal transmitted in the lower portion of the mid-band operating band. Consequently, RF energy emitted by a mid-band radiating element (particularly when the mid-band radiating element operates in the lower portion of the mid-band operating band) can couple (scatter) to the dipole arms of nearby low-band radiating elements. As described above, this coupling can distort the antenna beam generated by the array of mid-band radiating elements. Similar distortion can occur if RF energy emitted by so-called high-band radiating elements (which typically operate in a portion of the 3.1-5.8 GHz frequency band) couples to low-band radiating elements or mid-band radiating elements. Radiating elements according to embodiments of the present invention can be designed to be substantially transparent to nearby radiating elements operating in other frequency bands, thereby largely eliminating scattering. Radiating elements designed to suppress such scattering are often referred to as "masked" radiating elements.

[0049] Shielded radiating elements are known in the art. For example, U.S. Patent No. 9,570,804 discloses a low-band radiating element comprising a dipole arm formed as a series of RF chokes. The RF chokes suppress the formation of mid-band currents in the low-band dipole arm, thereby rendering the low-band radiating element substantially transparent to mid-band RF energy. U.S. Patent No. 10,439,285 and U.S. Patent No. 10,770,803 each disclose a low-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 meandering trace segments on a printed circuit board. In each case, the narrow inductive segments act as high impedance elements for RF energy in the mid-band frequency range, thereby rendering the low-band radiating element substantially transparent to RF energy in this frequency range. As another example, U.S. Patent No. 11,018,437 discloses a low-band radiating element comprising two dipole arms substantially transparent to mid-frequency RF energy and another two dipole arms substantially transparent to high-frequency RF energy. Additional shielded radiating element designs are disclosed in Chinese Patent Nos. CN 112787061A, CN 112164869A, CN 112290199A, CN 111555030A, CN 112186333A, CN 112186341A, CN 112768895A, CN 112821044A, CN 213304351U, CN 112421219A, and PCT Publication No. WO 2021 / 042862.

[0050] The shielded radiating elements are designed so that the RF energy emitted by the higher-band radiating elements tends not to induce higher-band currents in the dipole arms of nearby lower-band radiating elements. The present invention is based, in part, on the recognition that the feed stems of the lower-band radiating elements can also cause scattering. The feed stem of a cross-dipole radiating element refers to the structure that feeds RF signals to and from the dipole arms of the radiating element. In most cases, the dipole arms are mounted on the distal (front) end of the feed stem, and the base (rear) end of the feed stem is mounted on the reflector of the base station antenna or on a feed board printed circuit board, which is mounted on the reflector.

[0051] The feed stem of a radiating element typically has a length of approximately ¼ of the center wavelength, so that RF radiation emitted backward by the dipole radiator will reflect from the reflector and be in phase with the RF radiation emitted in the forward direction by the dipole arm (because the phase of the RF radiation will change by 90° as it travels ¼ of the center wavelength from the dipole arm to the reflector, will change by another 180° as it reflects from the reflector, and will change by another 90° as it travels ¼ of the center wavelength backward toward the dipole radiator). The feed stem typically includes metal structures extending along the length of the feed stem, and these metal structures may therefore have a length of approximately ¼ of the center wavelength of the radiating element. Consequently, the feed stem of a lower-band radiating element may also cause scattering relative to the RF radiation emitted by a nearby higher-band radiating element. While the amount of scattering caused by the feed stem of a lower-band radiating element tends to be much lower than that caused by an unmasked lower-band dipole arm, the emission level may still be significant enough to distort the higher-band antenna beam. This is especially true when the higher band radiating element is mounted directly behind the lower band radiating element.

[0052] According to an embodiment of the present invention, a cross-dipole radiating element having a shielded feed stem is provided. The feed stem included in the radiating element according to an embodiment of the present invention may have a shielded ground line and / or a shielded signal trace. For example, one or both of the ground line and / or the signal trace on the feed stem may be implemented as a series of widened conductive segments interconnected by narrowed (and possibly meandering) conductive traces. Each narrowed conductive trace can create a high impedance for current at frequencies in the operating frequency band of a nearby higher frequency band radiating element, for example. The radiating element according to an embodiment of the present invention can be included in a multi-band base station antenna and can reduce the amount of interaction between arrays in different frequency bands. The base station antenna including the radiating element according to an embodiment of the present invention can be used as, for example, a sector antenna in the above-mentioned cellular communication system.

[0053] In some embodiments, a cross-dipole radiating element is provided, comprising: a feed handle having a base and a distal end positioned in front of the base; and a first dipole radiator and a second dipole radiator mounted at the distal end of the feed handle. The feed handle comprises a first ground wire and a first signal trace that at least partially overlaps the first ground wire. The first ground wire and the first signal trace can be implemented, for example, on a feed handle printed circuit board. The first ground wire comprises at least a first widened conductive segment, a second widened conductive segment, and a third widened conductive segment, wherein the first widened conductive segment and the second widened conductive segment are connected by a first narrowed conductive trace, and the second widened conductive segment and the third widened conductive segment are connected by a second narrowed conductive trace.

[0054] In other embodiments, a cross-dipole radiating element is provided, comprising a feed stem and first and second dipole radiators mounted at a distal end of the feed stem. The feed stem comprises a first ground wire and a first signal trace. The first signal trace comprises a first forward-extending segment, a second laterally-extending segment, and a third segment. Furthermore, one of the first forward-extending segment, the second laterally-extending segment, and the third segment comprises a meandering segment.

[0055] In yet other embodiments, a cross-dipole radiating element is provided, comprising a feed stem and first and second dipole radiators mounted at a distal end of the feed stem. The feed stem comprises a first ground line and a first signal trace, wherein the first ground line comprises a first widened conductive segment and a second widened conductive segment connected by a first narrowed conductive trace. The first narrowed conductive trace comprises a first meandering section.

[0056] In the embodiments discussed above, the average width of the first narrowed conductive trace can be less than half the average width of the first widened conductive segment. In addition, the feed handle can also include a second ground wire, which includes a plurality of widened conductive segments connected by one or more additional narrowed conductive traces. In such embodiments, the first ground wire and the second ground wire can extend forward along the feed handle, and the first ground wire can also include a first branch extending toward the second ground wire, and the second ground wire can also include a second branch extending toward the first ground wire. The first and / or second branches can extend from corresponding ones of the narrowed conductive traces.

[0057] Before discussing radiating elements according to embodiments of the present invention, it is helpful to discuss the design and operation of a representative conventional low-band radiating element for a base station antenna.

[0058] Figure 1A is a perspective view of a conventional low-band crossed-dipole radiating element 1 . Figure 1B is a shaded side view of the crossed dipole radiating element 1 showing the metallization pattern on the first feed shank printed circuit board 20 - 1 of the radiating element 1 . Figure 1B In FIG, the solid line is the metallization pattern on the first side of the feed handle printed circuit board 20 - 1 , and the dashed line is the metallization pattern on the second (opposite) side of the feed handle printed circuit board 20 - 1 . Figure 1B In the embodiment, since the main surface of the feed handle printed circuit board 20-2 is perpendicular to the viewing angle, only the side surface of the second feed handle printed circuit board 20-2 is visible. It should be noted that in this document, the same elements can be individually referenced by their full reference numerals (e.g., feed handle printed circuit board 20-2) and can be collectively referenced by the first part of their reference numerals (e.g., feed handle printed circuit board 20).

[0059] like Figure 1A As shown in FIG, a conventional cross-dipole radiating element 1 includes a feed stem 10 and a pair of dipole radiators 70-1, 70-2. The feed stem 10 includes a first feed stem printed circuit board and a second feed stem printed circuit board 20-1, 20-2. Each feed stem printed circuit board 20-1, 20-2 includes a corresponding RF transmission line structure 16-1, 16-2, which transmits RF signals between the first and second feed transmission lines (not shown) of the radiating element 1 and the corresponding cross-dipole radiators 70-1, 70-2. Each feed transmission line can include, for example, a coaxial cable or a microstrip transmission line on the feed board printed circuit board. The feed transmission line transmits RF signals between the radiating element 1 and other components of the base station antenna including the radiating element 1.

[0060] refer to Figure 1A and 1B In both cases, the feed handle 10 has a base 12 and a distal end 14. The distal end 14 is positioned forward of the base 12. The first feed handle printed circuit board 20-1 includes a slit 22-1 extending forward from the base 12 of the feed handle 10, and the second feed handle printed circuit board 20-2 includes a slit 22-2 extending rearward from the distal end 14 of the feed handle 10. The feed handle printed circuit boards 20-1 and 20-2 are arranged perpendicular to each other, with the slit 22-2 in the feed handle printed circuit board 20-2 received within the slit 22-1 in the feed handle printed circuit board 20-1, so that the two mating feed handle printed circuit boards 20-1, 20-2 have a cross shape when viewed from the front.

[0061] The rear portion of each feed handle PCB 20 may include a protrusion 24 that is inserted through a slot (not shown) in the feed board PCB. The metallized pads on the protrusion 24 can be soldered to metallized pads on the feed board PCB to mechanically mount the radiating element 1 on the feed board PCB and electrically connect the RF transmission line structures 16-1, 16-2 on the feed handle 10 to the feed transmission lines on the feed board PCB.

[0062] The dipole radiators 70-1, 70-2 are positioned at the distal end 14 of the feed stem 10 and can be (and typically are) physically mounted on the distal end 14 of the feed stem 10. The first dipole radiator 70-1 extends along a first axis, and the second dipole radiator 70-2 extends along a second axis that is substantially perpendicular to the first axis. The first dipole radiator 70-1 includes a first dipole arm and a second dipole arm 80-1, 80-2, and the second dipole radiator 70-2 includes a third dipole arm and a fourth dipole arm 80-3, 80-4. The dipole radiators 70-1, 70-2 can be formed in a dipole radiator printed circuit board 82. The dipole arm 80 is a shielded dipole arm formed as a series of widened metal segments 84 interconnected by narrow metal traces 86. The dipole radiators 70-1, 70-2 are shown as having an elongated "figure-8" shape, with each dipole arm 80 formed as a loop. A variety of dipole arms are known in the art, including those having many different shapes or formed in different ways (e.g., using metal plates). It should be understood that radiating elements according to embodiments of the present invention having the feed shank design disclosed herein can have any suitable dipole arm design, including dipole arms having any shape, such as formed in any of the ways discussed above.

[0063] The dipole arms 80-1 and 80-2 of the first dipole radiator 70-1 are centrally fed by the first RF transmission line structure 16-1 on the first feed shank printed circuit board 20-1 and radiate together at a first polarization. In the depicted embodiment, the first dipole radiator 70-1 is designed to transmit and receive signals with a tilt of +45°. ° The dipole arms 80-3 and 80-4 of the second dipole radiator 70-2 are centrally fed by the second RF transmission line structure 16-2 on the second feed handle printed circuit board 20-2 and radiate together at a second polarization orthogonal to the first polarization. The second dipole radiator 70-2 is designed to transmit and receive signals with a tilt of -45 ° Linearly polarized signal.

[0064] like Figure 1BAs shown in FIG, a two-wire transmission line structure is formed on the second side of the feed handle printed circuit board 20-1. The two-wire transmission line structure includes first and second ground lines 30-1 and 30-2, which are implemented as first and second metallized regions extending from the base 12 of the feed handle 10 to the distal end 14 thereof. Each ground line 30-1 and 30-2 is coupled to a ground conductor (not shown) of the first feed transmission line for the radiating element 1. The connection between the first and second ground lines 30-1 and 30-2 and the ground conductor of the first feed transmission line can be at the base 12 of the feed handle 10. The first and second ground lines 30-1 and 30-2 can each have an electrical length of approximately 1 / 4 of the center wavelength of the radiating element 1.

[0065] The signal trace 40 is formed on a first side of the feed handle printed circuit board 20-1. The signal trace 40 is connected to a signal conductor of a feed transmission line that feeds the feed handle printed circuit board 20-1. The signal trace 40 extends forward from the base 12 of the feed handle 10 and travels approximately two-thirds of the way toward the distal end 14 of the feed handle 10. The signal trace 40 then passes through the first 90 ° Finally, the signal trace 40 passes through the second 90 ° It turns to extend rearwardly toward the base 12 of the feeding handle 10 .

[0066] The signal trace 40 includes a forward extending segment 42-1, a laterally extending segment 42-2, and a rearward extending segment 42-3. The forward extending segment 42-1 overlaps the first ground line 30-1. In this document, two elements "overlap" if an axis perpendicular to the main surface of the printed circuit board intersects with the two elements on the printed circuit board (or equivalent structure). The laterally extending segment 42-2 extends from the end of the forward extending segment 42-1 to span the gap 34 (i.e., the unmetallized area) provided between the first and second ground lines 30-1, 30-2. The laterally extending segment 42-2 partially overlaps with both the first ground line 30-1 and the second ground line 30-2. The rearward extending segment 42-3 extends from the end of the laterally extending segment 42-2 rearwardly toward the base 12 of the feed handle 10 at right angles. The rearward extending segment 42-3 overlaps with the second ground line 30-2.

[0067] As discussed above, embodiments of the present invention provide a cross-dipole radiating element having a shielded feed stem that can be substantially transparent to RF energy in the operating frequency band of one or more nearby higher-band radiating elements. The metallization of the feed stem used in radiating elements according to embodiments of the present invention can have a shielding structure that provides improved shielding performance. The improved shielding performance can improve the peak directivity of nearby higher-band radiating elements.

[0068] The following discussion of crossed-dipole radiating elements according to embodiments of the present invention will focus on low-band radiating elements designed to be masked relative to, for example, nearby mid-band and / or high-band radiating elements. However, it should be understood that the techniques disclosed herein can be used, for example, to provide mid-band radiating elements that are masked relative to nearby high-band radiating elements or in any other suitable application. Thus, while radiating elements according to embodiments of the present invention will be described below as low-band radiating elements, it should be understood that they can alternatively be reduced in size to operate as mid-band radiating elements or high-band radiating elements.

[0069] Before describing an exemplary embodiment of a radiating element of the present invention, an exemplary base station antenna in which a radiating element according to an embodiment of the present invention may be used will first be described.

[0070] Figures 2A-2B A conventional passive / active antenna system 100 is shown, which includes both a passive base station antenna 110 and an active antenna module 150. Specifically, Figure 2A is a schematic rear perspective view of the passive / active antenna system 100, and Figure 2B The antenna covers of both the passive base station antenna 110 and the active antenna module are omitted. Figure 2A A schematic perspective view of a passive / active antenna system 100 is shown. Figure 2A and 2B , the axes illustrate the longitudinal (L), transverse (T), and forward (F) directions of the base station antenna system 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.

[0071] refer to Figure 2A, the passive / active antenna system 100 can be mounted on, for example, an antenna tower 102 using mounting hardware 104. The active antenna module 150 can be mounted directly on the rear surface of the passive base station antenna 110, or can be held in place behind the passive base station antenna 110 by the mounting hardware 104. The front surface of the passive / active antenna system 100 can face the antenna tower 102 facing the coverage area of the passive / active antenna system 100. The passive base station antenna 110 includes a tubular radome 112 that surrounds and protects the antenna assembly mounted inside the radome 112. A top end cap 114 covers a top opening in the radome 112, and a bottom end cap 116 covers a bottom opening in the radome 112. A plurality of RF ports 118 extend through the bottom end cap 116 and are used to connect the passive base station antenna 110 to one or more external radio devices (not shown). The active antenna module 150 may be removably mounted behind the passive base station antenna 110 so that the active antenna module 150 may be later replaced with a different active antenna module.

[0072] refer to Figure 2B The passive base station antenna 110 includes a reflector assembly 120. The reflector assembly 120 may be referred to herein as a "passive reflector assembly" because it is part of the passive base station antenna 110. The passive reflector assembly 120 includes a main reflector 122 and first and second spaced-apart reflector strips 124-1 and 124-2 that extend longitudinally from respective first and second opposing sides of the main reflector 122. The passive reflector assembly 120 may also include a third reflector strip 124-3 that extends in a transverse direction between the top ends of the first and second reflector strips 124-1 and 124-2. An opening 126 is defined between the first and second reflector strips 124-1 and 124-2. For example, the opening 126 can be defined by the top portion of the main reflector 122, the first and second reflector strips 124-1, 124-2, and the third reflector strip 124-3. At least the main reflector 122 can include or contain 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. Various mechanical and electronic components (not shown) of the antenna can be mounted behind the passive reflector assembly 120, such as phase shifters, remote electronic tilt units, mechanical linkages, controllers, duplexers, etc.

[0073] The passive base station antenna 110 also includes a plurality of passive linear arrays of radiating elements extending forward from the passive reflector assembly 120. The linear arrays may support, for example, 2G, 3G, and / or 4G cellular services. Figures 2A-2BIn the illustrated exemplary passive base station antenna 110, the linear arrays include first and second low-band linear arrays 130-1 and 130-2 configured to operate in all or part of the 617-960 MHz frequency band. Each low-band linear array 130 includes a vertically extending column of low-band radiating elements 132. The passive base station antenna 110 also includes first through fourth mid-band linear arrays 140-1, 140-4 configured to operate in all or part of the 1427-2690 MHz frequency band. Each mid-band linear array 140 includes a vertically extending column of mid-band radiating elements 142. Each of the low-band and mid-band linear arrays 130, 140 can generate relatively static antenna beams (e.g., antenna beams each configured to cover a sector of a base station) that provide coverage to a predefined coverage area, wherein only the coverage area changes when the electronic downtilt of the generated antenna beam is adjusted (e.g., to change the size of a cell).

[0074] Each of the low-band and mid-band radiating elements 132 and 142 can be implemented as a dual-polarization radiating element, comprising a first radiator and a second radiator that transmit and receive RF energy with orthogonal polarizations. When such dual-polarization radiating elements are used, each of the low-band and mid-band linear arrays 130 and 140 can be connected to a pair of RF ports 118. The first RF port 118 is connected between a first port of a radio device (e.g., a remote radio head mounted on an antenna tower 102 near a passive base station antenna 110) and a first polarization radiator of a radiating element in one of the linear arrays, and the second RF port 118 is connected between a second port of the radio device and a second polarization radiator of a radiating element in the linear array. The RF signal transmitted by a selected one of the linear arrays 130, 140 is passed from the radio device to one of the RF ports 118, and from the RF port 118 to a power splitter (or, alternatively, a phase shifter assembly including a power splitter), which splits the RF signal into a plurality of sub-components, which are fed to corresponding first radiators or second radiators of the radiating elements in the linear array, where the sub-components of the RF signal are radiated into free space.

[0075] The low-band radiating elements and / or mid-band radiating elements 132, 142 may be mounted on a feed board printed circuit board that couples RF signals to and from the respective radiating elements 132, 142. Figure 2B, mid-band radiating elements 142 are shown mounted in pairs on a plurality of mid-band feed board printed circuit boards 148. (Low-band radiating elements are also mounted on the feed board printed circuit boards, but they are not visible in the figure.) Cables can be used to connect each feed board printed circuit board 148 to other components of the antenna, such as a duplexer, phase shifters, etc.

[0076] Most of the low-band and mid-band radiating elements 132, 142 are mounted to extend forward from the main reflector 122. However, the low-band linear arrays 130-1, 130-2 extend substantially the full length of the passive / active antenna system 100 and, therefore, extend beyond the main reflector 122. The first and second reflector strips 124-1, 124-2 can provide mounting locations for the low-band radiating elements 132 positioned above the main reflector 122. The first and second reflector strips 124-1, 124-2 can be integral with the main reflector 122 so that the first and second reflector strips 124-1, 124-2 and the main reflector 122 are maintained at a common ground voltage, which can improve the performance of the low-band linear arrays 130-1, 130-2.

[0077] Each low-band radiating element 132 may include a tilted -45 ° / +45 ° A crossed dipole radiating element comprising a tilted-45 ° Polarized dipole radiator 134-1 and tilted +45 ° Polarized dipole radiator 134-2. The dipole radiators 134-1, 134-2 can be mounted on a feed stem (not shown). In some cases, the three uppermost low-band radiating elements 132 above the main reflector 122 can be mounted on a frequency selective surface ("FSS") covering the opening 126. This FSS is described in further detail below. In other cases, the low-band radiating elements 132 may include an angled feed stem that allows these radiating elements to be mounted on the first and second reflector strips 124-1, 124-2 with their dipole arms in front of the opening 126. Each low-band radiating element 132 has a dipole arm that is designed to be substantially transparent to the RF energy emitted by the mid-band radiating element 142.

[0078] Active antenna module 150 includes a multi-column beamforming array 160 of radiating elements 162 and a beamforming radio (not visible in the figure). The multi-column beamforming array 160 can be mounted in the front portion of active antenna module 150, and the beamforming radio can be mounted behind the beamforming array 160. Beamforming array 160 may, for example, include multiple vertically extending columns of high-band radiating elements 162 configured to operate in all or part of the 3.1-4.2 GHz frequency band. The high-band radiating elements 162 are mounted to extend forward from the reflector 154 (herein referred to as the "active reflector") of active antenna module 150. The beamforming radio is capable of electronically adjusting the amplitude and / or phase of sub-components of the RF signal output to different radiating elements 162 of the multi-column beamforming array 160. For example, each port of a beamforming radio may be coupled to a column of radiating elements of the beamforming array 160, and the amplitude and phase of the subcomponents of the RF signal fed to each column may be adjusted so that the generated antenna beam is narrowed in the azimuth plane and pointed in a desired direction in the azimuth plane.

[0079] The beamforming array 160 of the active antenna module 150 is mounted behind the opening 126 in the passive reflector assembly 114. The beamforming array 160 is positioned at Figure 2B It can be seen in Figure 2B The radomes of the passive base station antenna 110 and active antenna module 150 are omitted from the view of FIG. Opening 126 in the passive reflector assembly 120 allows the antenna beam generated by the beamforming array 160 to pass through the passive base station antenna 110 to provide service to the coverage area of the passive / active antenna system 100.

[0080] An FSS (not shown) may cover the opening 126. The FSS may be configured to allow RF energy emitted by the high-band radiating elements 162 in the beamforming array 160 to pass therethrough, while reflecting RF energy in the lower frequency bands (and specifically, the low-band RF signals emitted by the low-band radiating elements 132). The FSS may be coplanar with the opening 126, in front of the opening 126, or behind the opening 126. The FSS may have a grid pattern, such as a grid of metal patches and / or other metal structures. The grid pattern may be arranged in any suitable manner and may be symmetrical or asymmetrical across the width and / or length of the FSS. The grid pattern may include sub-wavelength periodic microstructures. The metal patches / structures may be arranged in one or more layers. The FSS may be formed on a substrate (e.g., a printed circuit board) or formed from a metal sheet. In some embodiments, the FSS may include a portion of the passive reflector assembly 120 that is stamped to form a metal grid structure therein. In such cases, “opening 126 ” comprises a large number of small openings that act as large openings relative to the RF energy in the operating frequency band of the beamforming array 160 .

[0081] Now refer to Figure 3A-5 Embodiments of the present invention are described in more detail.

[0082] Figure 3A is a perspective view of a low-band radiation element 200 according to an embodiment of the present invention. Figure 3B and 3C is a plan view of the first side and the second side of the first feed handle printed circuit board 220-1 included in the radiation element 200, and Figure 3D is a shaded plan view showing the metallization on both sides of the dielectric substrate of the first feed handle printed circuit board 220-1. Figures 3B-3D , the solid line shows the outline of the dielectric substrate of the first feed handle PCB 220-1, the dashed line shows the metallization pattern on the first side of the feed handle PCB 220-1, and the dotted line shows the metallization pattern on the second side of the feed handle PCB 220-1. For example, the low-band radiating element 200 can be used to implement the low-band radiating element 132 of the base station antenna 100.

[0083] refer to Figure 3A, the low-band radiating element 200 includes a feed handle 210, a first dipole radiator 270-1, and a second dipole radiator 270-2. The first dipole radiator 270-1 includes a first dipole arm and a second dipole arm 280-1, 280-2, and the second dipole radiator 270-2 includes a third dipole arm and a fourth dipole arm 280-3, 280-4. The dipole radiators 270-1, 270-2 of the radiating element 200 are located adjacent to the front end of the feed handle 210 and can be (and are typically) physically mounted on the distal end of the feed handle 210. The dipole radiator 270 and the dipole arm 280 can be similar to those described above with reference to Figures 1A-1B The described dipole radiator 70 and dipole arm 80 are identical, so further description thereof will be omitted here.

[0084] The feeding handle 210 has a base 212 and a distal (front) end 214 positioned in front of the base 212. The feeding handle 210 includes a first feeding handle printed circuit board and a second feeding handle printed circuit board 220-1, 220-2. The first feeding handle printed circuit board 220-1 includes a slot 222-1 extending rearward from the distal end base 214 of the feeding handle 210 (see FIG. Figure 3B ), and the second feeding handle PCB 220-2 includes a slit 222-2 extending forward from the base 212 of the feeding handle 210. The feeding handle PCBs 220-1 and 220-2 are arranged perpendicular to each other, wherein the slit 222-2 in the feeding handle PCB 220-2 is received within the slit 222-1 in the feeding handle PCB 220-1, so that when viewed from the front, the two mating PCBs 210-1, 210-2 have a cross shape.

[0085] The first feed handle printed circuit board 220 - 1 includes a dielectric substrate 224 having a first metallization layer 226 on one major surface of the dielectric substrate 224 and a second metallization layer 228 on the other major surface of the dielectric substrate 224 . Figure 3B and 3C 2 is a plan view of two major surfaces of the dielectric substrate 224 .

[0086] refer to Figure 3B, a first metallization layer 226 formed on a first major surface of the dielectric substrate 224 includes a signal trace 240. The signal trace 240 is connected to a signal conductor of a feed transmission line that feeds the feed handle printed circuit board 220-1, typically at the base of the feed handle 210. The signal trace 240 extends forward from the base of the first feed handle printed circuit board 220-1 and travels approximately two-thirds of the way toward the distal end of the first feed handle printed circuit board 220-1. The signal trace 240 includes a forward extending segment 242-1, a laterally extending segment 242-2, and a rearward extending segment 242-3. The forward extending segment 242-1 includes a widened pad area near the base of the first feed handle printed circuit board 220-1 and a narrower trace extending forward from the widened pad area. The laterally extending segment 242-2 includes a narrow trace that extends from the end of the forwardly extending segment 242-1 to span the gap 234 between the first and second ground wires 230-1, 230-2 (discussed below). The rearwardly extending segment 242-3 includes a narrow trace that extends at a right angle from the end of the laterally extending segment 242-2 toward the base 212 of the feed handle 210.

[0087] refer to Figure 3C The second metallization layer 228 formed on the second main surface of the dielectric substrate 224 includes first and second ground lines 230-1 and 230-2. Each ground line 230 extends substantially from the base of the first feed handle printed circuit board 220-1 to a distal end. The end of each ground line 230 located at the base of the first feed handle printed circuit board 220-1 can be connected to a ground conductor (not shown) of the first feed transmission line for the radiating element 200. As shown, the ground line 230 can have a widened pad area at the base of the first feed handle printed circuit board 220-1 to facilitate connecting the ground conductor of the first feed transmission line for the radiating element 200 to the ground line 230.

[0088] Each of the first and second ground lines 230-1 and 230-2 includes a corresponding inwardly extending protrusion 232-1 and 232-2. Thus, the distal end of the first protrusion 232-1 faces the distal end of the second protrusion 232-2. A small, unmetallized gap 234 separates the protrusions 232-1 and 232-2. The protrusions 232-1 and 232-2 are positioned just behind the slot 222-1.

[0089] The first and second ground lines 230 - 1 and 230 - 2 may each have a length of about ¼ of the central wavelength of the radiation element 200 .

[0090] Each ground line 230 can include a plurality of widened conductive segments 236 connected by one or more narrowed conductive traces 238. In the depicted embodiment, each ground line 230 includes three widened conductive segments 236 and two narrowed conductive traces 238. On a first ground line 230-1, a narrowed conductive trace 238-1 connects the widened conductive segment 236-1 to the widened conductive segment 236-2, and a narrowed conductive trace 238-2 connects the widened conductive segment 236-2 to the widened conductive segment 236-3. On a second ground line 230-2, a narrowed conductive trace 238-3 connects the widened conductive segment 236-4 to the widened conductive segment 236-5, and a narrowed conductive trace 238-4 connects the widened conductive segment 236-5 to the widened conductive segment 236-6.

[0091] Each widened conductive segment 236 has a corresponding width W1, where width W1 is measured in a direction generally perpendicular to the direction of current flow along the corresponding widened segment 236. The width W1 of each widened segment 236 need not be constant, and therefore, in some cases, reference will be made to the average width of each widened segment 236. The narrowed conductive traces 238 may similarly have a corresponding width W2, where width W2 is measured in a direction generally perpendicular to the direction of current flow along the narrowed conductive traces 238. The width W2 of each narrowed conductive trace 238 also need not be constant, and therefore, in some cases, reference will be made to the average width of each narrowed trace segment 238. The average width W1 of each widened conductive segment 236 can be, for example, at least twice the average width W2 of each narrowed conductive trace 238. In other embodiments, the average width W1 of each widened conductive segment 236 can be at least three times the average width W2 of each narrowed conductive trace 238.

[0092] Each narrowed conductive trace 238 can act as a high impedance element designed to interrupt currents in the higher-band frequency range that would otherwise be induced on the ground wire 230. The narrowed conductive trace 238 can be designed to create this high impedance to the higher-band currents without significantly affecting the ability of the low-band currents to flow on the feed stem 210. Thus, the narrowed conductive trace 238 can reduce the high-band currents induced on the feed stem 210 of the low-band radiating element 200 and, therefore, reduce interference with the antenna pattern of the higher-band linear array. In some embodiments, the narrowed conductive trace 238 can make the feed stem 210 of the low-band radiating element 200 virtually invisible to the higher-band radiating element.

[0093] The first protrusion 232-1 extends inwardly from the second narrowed conductive trace 238-2, and the second protrusion 232-2 extends inwardly from the fourth narrowed conductive trace 238-4.The first and second protrusions 232-1, 232-2 may each comprise a narrowed conductive trace that is open at its respective distal end.

[0094] refer to Figure 3D , it can be seen that the forward-extending segment 242-1 of the signal trace 240 overlaps the first ground line 230-1. The laterally-extending segment 242-2 of the signal trace 240 overlaps portions of both the first ground line 230-1 and the second ground line 230-2. The rearward-extending segment 342-3 of the signal trace 240 overlaps the second ground line 330-2.

[0095] The second feeding handle printed circuit board 220-2 (see Figure 3A ) is nearly identical to the PCB 220-1, except for: (1) the location of the slots 222-1 and 222-2; and (2) on the feed handle PCB 220-2, the transversely extending segment 242-2 is located closer to the base 212 of the feed handle 210 to allow this segment to span the axis defined by the slots 222-2 in the front portion of the feed handle PCB 220-2. Therefore, further description of the second feed handle PCB 220-2 will be omitted herein.

[0096] like Figures 3A-3D As shown in FIG, the radiating element 200 includes a feed stem 210 having a base 212 and a distal end 214 positioned forward of the base 212. The radiating element 200 also includes a first dipole radiator and a second dipole radiator 270-1, 270-2 mounted at the distal end 214 of the feed stem 210. The first dipole radiator 270-1 includes a first dipole arm 280-1 and a second dipole arm 280-2, and the second dipole radiator 270-2 includes a third dipole arm 280-3 and a fourth dipole arm 280-4. The feed stem 210 includes a first ground line 230-1 and a first signal trace 240 that at least partially overlaps the first ground line 230-1. Here, the first ground line 230-1 and the first signal trace 240 are each formed on a first feed stem printed circuit board 220-1. The first ground line 230-1 includes a first widened conductive segment, a second widened conductive segment, and a third widened conductive segment 236-1, 236-2, 236-3, wherein the first widened conductive segment and the second widened conductive segment 236-1, 236-2 are connected by a first narrowed conductive trace 238-1, and the second widened conductive segment and the third widened conductive segment 236-2, 236-3 are connected by a second narrowed conductive trace 238-2.

[0097] The feed handle printed circuit board 220-1 also includes a second ground line 230-2, which includes at least a fourth widened conductive segment, a fifth widened conductive segment, and a sixth widened conductive segment 236-4, 236-5, and 236-6, wherein the fourth widened conductive segment and the fifth widened conductive segment 236-4 and 236-5 are connected by a third narrowed conductive trace 238-3, and the fifth widened conductive segment and the sixth widened conductive segment 236-5 and 236-6 are connected by a fourth narrowed conductive trace 238-4. The first ground line 230-1 extends forward along substantially the entire length of the feed handle 210. The first ground line 230-1 includes a first branch in the form of a first protrusion 232-1 extending toward the second ground line 230-2. The second ground line 230-2 extends forward along substantially the entire length of the feed handle 210 and similarly includes a second leg in the form of a second protrusion 232-2 extending toward the first ground line 230-1. The first leg 232-1 extends from the second narrowed conductive trace 238-2, and the second leg 232-2 extends from the fourth narrowed conductive trace 238-4.

[0098] The first narrowed conductive trace 238-1 has an average width of W2, and the first widened conductive segment 236-1 has an average width of W1. W2 is less than half of W1. The average width W3 of the first branch 232-1 is less than the average width W1 of the first widened conductive segment 236-1. The average width W3 of the second branch 232-2 is less than the average width W1 of the fourth widened conductive segment 236-4, and the second branch 232-2 extends from the fourth narrowed conductive trace 238-4. The first through third widened conductive segments 236-1, 236-2, and 236-3 may have respective lengths L that vary by less than 25%. The fourth through sixth widened conductive segments 236-4, 236-5, and 236-6 may also have respective lengths L that vary by less than 25%. In some embodiments, the lengths L of the first through sixth widened conductive segments 236-1, 236-6 may vary by less than 25%. In some embodiments, the average width W1 of the first to sixth widened conductive segments 236 - 1 to 236 - 6 may vary by less than 15%.

[0099] The first signal trace 240 completely overlaps the first narrowed conductive trace 238 - 1 and completely overlaps the second narrowed conductive trace 238 - 2 .

[0100] Figure 4A is a perspective view of a low-band radiating element 300 according to an embodiment of the present invention, which is a side view. Figure 4B and 4C is a plan view of the first side and the second side of the first feed handle printed circuit board 320-1 included in the radiation element 300, and Figure 4Dis a shaded plan view showing the metallization on both sides of the dielectric substrate of the first feed handle printed circuit board 220-1. Figures 4B-4D In FIG, the solid line shows the outline of the dielectric substrate of the first feed handle printed circuit board 320-1, the dashed line shows the metallization pattern on the first side of the first feed handle printed circuit board 320-1, and the dotted line shows the metallization pattern on the second side of the first feed handle printed circuit board 320-1. For example, the low-band radiating element 300 can be used to implement the low-band radiating element 132 of the passive base station antenna 110. Since the low-band radiating element 300 is very similar to the low-band radiating element 200, the following description will focus on the differences between the two radiating elements 200 and 300.

[0101] By Figures 3B-3D and Figures 4B-4D As can be seen from the comparison, the first feed handle printed circuit board 320-1 is almost identical to the first feed handle printed circuit board 220-1, with the only difference being that the signal trace 340 (which includes segments 342-1, 342-2, and 342-3) on the first feed handle printed circuit board 320-1 includes a meandering segment 341, and one of the narrowed conductive traces on each of the ground lines 330-1 and 330-2 on the first feed handle printed circuit board 320-1 is similarly implemented as a meandering narrowing conductive trace segment 339-1 and 339-2. Here, a meandering segment of a conductive trace refers to a non-straight segment of a conductive trace that follows a meandering path to increase its path length. Including a meandering segment on a conductive trace provides a convenient way to extend the length of the conductive trace while still providing a relatively compact conductive trace.

[0102] like Figure 3C As shown in FIG, the meandering section 341 of the signal trace 340 is implemented by including a generally U-shaped section in the signal trace 340. The generally U-shaped section may have square corners, rounded corners, corners with one or more angled or inclined areas, etc. Similarly, the meandering section 339 of each of the ground lines 330-1, 330-2 is implemented by including a generally U-shaped section in the ground line 330. It should also be understood that the meandering sections 341, 339 can be implemented as a series of U-shaped sections forming a square wave, a sine wave, etc., or can include a plurality of spaced-apart U-shaped sections. Likewise, it should be understood that in other embodiments, the meandering section can be formed using forms other than generally U-shaped sections.

[0103] The meandering sections 341 and 339 serve to increase the overall inductance of the signal trace 340 and the first and second ground lines 330-1 and 330-2. The increased inductance in the signal trace 340 can help further suppress the formation of higher-frequency currents on the signal trace 340. Additionally, the meandering section 341 allows the signal trace to completely overlap with the first ground line 330-1 (which has a similar meandering section 339), so that the first signal trace 340 forms a microstrip transmission line along its entire length, except for a small portion of the signal trace 340 above the gap 334 that separates the first and second protrusions 332-1 and 332-2 of the respective first and second ground lines 330-1 and 330-2. The increased inductance in the ground line 330 and the fringe capacitive coupling between the widened conductive section 336 can create an LC circuit that acts as a filter to suppress the formation of higher-frequency currents on the ground line 330.

[0104] It should also be understood that some radiating elements are formed using sheet metal or die-cast feed stems rather than printed circuit based feed stems. Any of the techniques disclosed herein can be implemented in such sheet metal or die-cast based feed stems.

[0105] Figure 5 4 is a schematic side view of a base station antenna 400 including a low-frequency band radiating element 432 according to another embodiment of the present invention. The base station antenna 400 may be the same as the base station antenna 100 described above (even though the base station antenna 100 is not shown in FIG. 4 for simplicity of the drawings). Figure 5 Not all elements of the base station antenna 100 are shown. The base station antenna 400 includes a frequency selective surface 402, an array 430 of lower-band radiating elements 432, and a plurality of arrays 460 of higher-band radiating elements 462 positioned behind the frequency selective surface 402, with at least some of the lower-band radiating elements positioned in front of the frequency selective surface 402. At least one of the lower-band radiating elements 432 includes a pair of dipole radiators 470-1, 470-2, and a first feeder cable 434-1 and a second feeder cable 434-2. The first feeder cable 434-1 and the second feeder cable 434-2 each extend forward from the frequency selective surface 402 to be directly attached to the respective first and second dipole radiators 470-1, 470-2. The dipole radiators 470-1, 470-2 can be implemented using the dipole radiator printed circuit board 82 of the radiating element 1. The first and second feeder cables 434-1, 434-2 may be implemented, for example, using RG405 cables, which are very thin coaxial cables. The coaxial cables 434-1, 434-2 may each have a diameter of less than 1.68 mm.

[0106] Figures 2A-2BOne difficulty with the passive / active base station antenna system 100 is that the low-band radiating element 132 is mounted directly in front of the high-band beamforming array 160. Consequently, the metal elements of the low-band radiating element 132 may partially block / reflect the RF radiation emitted by the high-band beamforming array 160, and / or the high-band RF radiation may induce currents in the metal elements of the low-band radiating element 132, which may then re-radiate the high-band radiation in a manner that distorts the shape of the antenna beam generated by the high-band beamforming array 160. In some cases, the impact of the low-band radiating element 132 on the antenna beam generated by the high-band beamforming array 160 may be reduced by using very thin coaxial cables 434-1, 434-2 to feed the low-band radiating element 132.

[0107] Although the dipole arms of the low-frequency band radiating element described above are implemented on a dipole radiator printed circuit board, it should be understood that the embodiments of the present invention are not limited thereto. For example, in other embodiments, the dipole arms may be implemented as metal sheet dipole arms or may be implemented using other metal structures.

[0108] 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.

[0109] 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.

[0110] 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.).

[0111] 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.

[0112] In this context, the term "substantially" means within + / - 10%.

[0113] 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.

[0114] 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 crossed dipole radiating element, comprising: a feeding handle having a base and a distal end positioned forward of the base; a first dipole radiator mounted at a distal end of the feeding handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; as well as a second dipole radiator mounted at a distal end of the feeding handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm, wherein the feeding handle comprises a first ground line and a first signal trace at least partially overlapping the first ground line, The first grounding line includes at least a first widened conductive segment, a second widened conductive segment and a third widened conductive segment, wherein the first widened conductive segment and the second widened conductive segment are connected by a first narrowed conductive trace, and the second widened conductive segment and the third widened conductive segment are connected by a second narrowed conductive trace. 2 . The crossed-dipole radiating element of claim 1 , wherein an average width of the first narrowed conductive trace is less than half an average width of the first widened conductive segment.

3. The cross-dipole radiating element according to claim 2, the feed handle further comprising a second grounding line, the second grounding line comprising at least a fourth widened conductive segment, a fifth widened conductive segment and a sixth widened conductive segment, wherein the fourth widened conductive segment and the fifth widened conductive segment are connected by a third narrowed conductive trace, and the fifth widened conductive segment and the sixth widened conductive segment are connected by a fourth narrowed conductive trace.

4. The cross-dipole radiating element according to claim 3, wherein the first ground line extends forward along substantially the entire length of the feed handle, the first ground line further includes a first branch extending toward the second ground line, and the second ground line extends forward along substantially the entire length of the feed handle, the second ground line further includes a second branch extending toward the first ground line. The crossed-dipole radiating element of claim 4 , wherein an average width of the first leg is smaller than an average width of the first widened conductive segment.

6. The crossed-dipole radiating element of claim 4, wherein the first leg extends from the second narrowed conductive trace.

7. The cross-dipole radiating element according to any one of claims 1 to 6, wherein the respective lengths of the first widened conductive segment to the third widened conductive segment vary by less than 25%.

8. The crossed-dipole radiating element of any one of claims 1-6, wherein the first signal trace completely overlaps the first narrowed conductive trace and completely overlaps the second narrowed conductive trace.

9. The crossed-dipole radiating element of any one of claims 1-6, wherein an average width of the second leg is smaller than an average width of the fourth widened conductive segment, and the second leg extends from the fourth narrowed conductive trace.

10. The cross-dipole radiating element of any one of claims 1-6, wherein the first single trace comprises a first forward-extending segment, a second laterally-extending segment, and a third rearward-extending segment, wherein one of the first forward-extending segment, the second laterally-extending segment, and the third rearward-extending segment comprises a meandering segment.

11. The cross-dipole radiating element of claim 10, wherein the first forward-extending segment comprises the meandering section.

12. The crossed-dipole radiating element according to any one of claims 1-6, wherein the first narrowed conductive trace comprises a meandering section.

13. The cross-dipole radiating element according to any one of claims 1 to 6, wherein the feed handle comprises a feed handle printed circuit board, and the first signal trace is a first metallization pattern on a first side of the feed handle printed circuit board, and the first ground line is a second metallization pattern on a second side of the feed handle printed circuit board.

14. A crossed-dipole radiating element, comprising: a feeding handle having a base and a distal end positioned forward of the base; a first dipole radiator mounted at a distal end of the feeding handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; as well as a second dipole radiator mounted at a distal end of the feeding handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm, The feeding handle includes a first ground line and a first signal trace, wherein the first signal trace comprises a first forward extending segment, a second laterally extending segment, and a third segment, and wherein one of the first forwardly extending segment, the second laterally extending segment, and the third segment comprises a tortuous section.

15. The crossed-dipole radiating element of claim 14, wherein the meandering section comprises at least one U-shaped section.

16. The crossed-dipole radiating element of claim 14, wherein the first forward-extending segment comprises the meandering section.

17. The crossed-dipole radiating element according to any one of claims 14 to 16, wherein the first ground line comprises a first widened conductive segment and a second widened conductive segment connected by a first narrowed conductive trace.

18. The crossed-dipole radiating element of claim 17, wherein the average width of the first narrowed conductive trace is less than half the average width of the first widened conductive segment.

19. The crossed-dipole radiating element of claim 18, wherein the first narrowed conductive trace comprises a meandering segment.

20. The crossed-dipole radiating element of any of claims 14-16, wherein the first signal trace completely overlaps the first narrowed conductive trace.

21. The cross-dipole radiating element according to any one of claims 14 to 16, wherein the feed handle comprises a feed handle printed circuit board, and the first signal trace is a first metallization pattern on a first side of the feed handle printed circuit board, and the first ground line is a second metallization pattern on a second side of the feed handle printed circuit board.

22. The cross-dipole radiation element according to claim 21, wherein the first ground line extends along a longitudinal direction of the feed handle printed circuit board, and comprises a first branch line extending along a transverse direction of the feed handle printed circuit board.

23. The crossed-dipole radiating element of claim 22, wherein the first leg extends from the first narrowed conductive trace.

24. The crossed-dipole radiating element of claim 22, wherein an average width of the first legs is smaller than an average width of the first widened conductive segment.

25. A crossed-dipole radiating element, comprising: a feeding handle having a base and a distal end positioned forward of the base; a first dipole radiator mounted at a distal end of the feeding handle, the first dipole radiator comprising a first dipole arm and a second dipole arm; as well as a second dipole radiator mounted at a distal end of the feeding handle, the second dipole radiator comprising a third dipole arm and a fourth dipole arm, The feeding handle includes a first ground line and a first signal trace, The first ground line includes a first widened conductive segment and a second widened conductive segment connected by a first narrowed conductive trace, and the first narrowed conductive trace includes a first meandering section.

26. The crossed-dipole radiating element of Claim 25, wherein the first meandering section comprises a U-shaped section.

27. The crossed-dipole radiating element of claim 25, wherein the average width of the first narrowed conductive trace is less than half the average width of the first widened conductive segment.

28. The cross-dipole radiating element of claim 25, wherein the first single trace comprises a first forward-extending segment, a second laterally-extending segment, and a third rearward-extending segment, wherein one of the first forward-extending segment, the second laterally-extending segment, and the third rearward-extending segment comprises a second meandering section.

29. The crossed-dipole radiating element of Claim 28, wherein the first forward-extending segment comprises the second meandering section.

30. The cross-dipole radiating element according to any one of claims 25-29, the feed stem further comprising a second ground line comprising at least a third widened conductive segment and a fourth widened conductive segment connected by a second narrowed conductive trace.

31. The cross-dipole radiating element of claim 30, wherein the first ground line extends forward along substantially the entire length of the feed handle, the first ground line further comprises a first branch extending toward the second ground line, and the second ground line extends forward along substantially the entire length of the feed handle, the second ground line further comprises a second branch extending toward the first ground line.

32. The crossed-dipole radiating element of any of claims 25-29, wherein the first leg extends from the first narrowed conductive trace.

33. The crossed-dipole radiating element of any of claims 25-29, wherein the first signal trace at least partially overlaps the first narrowed conductive trace and completely overlaps the second narrowed conductive trace.

34. The cross-dipole radiating element according to any one of claims 14-16, wherein the third segment is a rearward extending segment.

35. A base station antenna, comprising: Frequency selective surfaces; an array of lower frequency band radiating elements positioned in front of the frequency selective surface; as well as a multi-column array of higher frequency band radiating elements positioned behind the frequency selective surface, At least one of the lower frequency band radiating elements includes a pair of dipole radiators, a first feed cable, and a second feed cable, wherein the first feed cable and the second feed cable extend forward from the frequency selective surface to be directly attached to the corresponding first dipole radiator and the second dipole radiator.

36. The base station antenna of claim 35, wherein a diameter of the first feeder cable is less than 1.68 mm.

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