Patent Description:
The present invention generally relates to radio communications and, more particularly, to base station antennas for cellular communications systems.

Cellular communications systems are well known in the art. In a typical cellular communications system, a geographic area is divided into a series of regions that are referred to as "cells," and each cell is served by a base station. The base station may include baseband equipment, radios and base station antennas that are configured to provide two-way radio frequency ("RF") communications with subscribers that are positioned throughout the cell. In many cases, the cell may be divided into a plurality of "sectors," and separate base station antennas provide coverage to each of the sectors. The antennas are often mounted on a tower, with the radiation beam ("antenna beam") that is generated by each antenna directed outwardly to serve a respective sector. Typically, a base station antenna includes one or more phase-controlled arrays of radiating elements, with the radiating elements arranged in one or more vertical columns when the antenna is mounted for use. Herein, "vertical" refers to a direction that is perpendicular to the horizontal plane that is defined by the horizon. Reference will also be made to the azimuth plane, which is a horizontal plane that bisects the base station antenna, and to the elevation plane, which is a plane extending along the boresight pointing direction of the antenna that is perpendicular to the azimuth plane.

A common base station configuration is the "three sector" configuration in which a cell is divided into three <NUM>° sectors in the azimuth plane. A base station antenna is provided for each sector. In a three sector configuration, the antenna beams generated by each base station antenna typically have a Half Power Beamwidth ("HPBW") in the azimuth plane of about <NUM>° so that each antenna beam provides good coverage throughout a <NUM>° sector. Three such base station antennas provide full <NUM>° coverage in the azimuth plane. Typically, each base station antenna will include one or more so-called "linear arrays" of radiating elements that includes a plurality of radiating elements that are arranged in a generally vertically-extending column. Each radiating element may have an azimuth HPBW of approximately <NUM>° so that the antenna beam generated by the linear array will have a HPBW of about <NUM>° in the azimuth plane. By providing a phase-controlled column of radiating elements extending along the elevation plane, the HPBW of the antenna beam in the elevation plane may be narrowed to be significantly less than <NUM>°, with the amount of narrowing increasing with the length of the column in the vertical direction.

As the volume of cellular traffic has grown, cellular operators have added new cellular services in a variety of new frequency bands. When these new services are introduced, the existing "legacy" services typically must be maintained to support legacy mobile devices. In some cases, it may be possible to use linear arrays of so-called "wide-band" or "ultra-wide-band" radiating elements to support service in the new frequency bands. In other cases, however, it may be necessary to deploy additional linear arrays (or multi-column arrays) of radiating elements to support service in the new frequency bands. Due to local zoning ordinances and/or weight and wind loading constraints, there is often a limit as to the number of base station antennas that can be deployed at a given base station. Thus, to reduce the number of antennas, many operators deploy so-called "multiband" base station antennas that include multiple linear arrays of radiating elements that communicate in different frequency bands to support multiple different cellular services. Additionally, with the introduction of fifth generation (<NUM>) cellular services, multi-column arrays of radiating elements are being added to base station antennas that can support beamforming and/or massive multi-input-multi-output ("MIMO") <NUM> services.

One multiband base station antenna that is currently of interest includes two linear arrays of "low-band" radiating elements that are used to provide service in some or all of the <NUM>-<NUM> frequency band, as well as a massive MIMO array of "high-band" radiating elements that operate in, for example, some or all of the <NUM>-<NUM> frequency band, the <NUM>-<NUM> frequency band, or the <NUM>-<NUM> frequency band. Massive MIMO arrays typically have at least four columns of radiating elements, and as many as thirty-two columns of radiating elements. Most proposed implementations include eight columns of radiating elements (or vertically stacked sets of eight column arrays to obtain sixteen or thirty-two column arrays). One example of such a base station antenna <NUM> is shown schematically in <FIG>.

Referring to <FIG>, the base station antenna <NUM> includes first and second linear arrays <NUM>-<NUM>, <NUM>-<NUM> of low-band radiating elements <NUM> and a multi-column array <NUM> of high-band radiating elements <NUM>, here shown with eight columns. The multi-column array <NUM> of high-band radiating elements <NUM> may be a massive MIMO high-band array. The radiating elements <NUM>, <NUM> may be mounted to extend forwardly from a reflector <NUM> which may serve as a ground plane for the radiating elements <NUM>, <NUM>. As shown in <FIG>, the low-band linear arrays <NUM> typically extend for the full length of the base station antenna <NUM>. The multi-column high-band array <NUM> is positioned between low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM>. Note that herein like elements may be assigned two-part reference numerals. These elements may be referred to individually by their full reference numeral (e.g., low-band linear array <NUM>-<NUM>) and collectively by the first part of their reference numeral (e.g., the low-band linear arrays <NUM>).

The base station antenna <NUM>, however, can be challenging to implement in a commercially acceptable manner because achieving a <NUM>° azimuth HPBW antenna beam in the low-band typically requires low-band radiating elements that are, for example, about <NUM> (or more) wide. If the massive MIMO high-band array <NUM> is positioned between the two low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM>, the base station antenna <NUM> will become wider than is considered commercially acceptable (having a width that is, for example, wider than <NUM>). While, the massive MIMO high-band array <NUM> could alternatively be positioned either above or below the low-band arrays <NUM>-<NUM>, <NUM>-<NUM> on reflector <NUM> in order to decrease the width of the base station antenna <NUM>, this would increase the length and cost of the base station antenna <NUM> to the point where the antenna is likely to be considered commercially unacceptable. Accordingly, improved base station antenna designs are needed. <CIT> discloses a dual-polarized radiating element for a base station antenna, comprising:a first dipole radiator that includes a first dipole arm extending upwardly from a central region and a second dipole arm extending to a first side of the central region; a second dipole radiator that includes a third dipole arm extending downwardly from a central region and a fourth dipole arm extending to the first side of the central region; wherein, when the dual-polarized radiating element is viewed from the front, the first through fourth dipole arms meet in a central region of the radiating element, wherein the first and second dipole radiator are configured to transmit RF radiation having slant +<NUM>° and -<NUM>° polarization, respectively, wherein the dipole arms comprise inductive elements that are configured to suppress currents in a higher frequency band.

<CIT> discloses a dual-polarized radiating element with a first dipole arm and a second dipole arm of a first dipole radiator extending upwardly and to a first side, respectively, and a third dipole arm and a fourth dipole arm of a second dipole extending downwardly and to the first side, respectively, wherein the dipoles resonate on at least a low and a high frequency.

<CIT> discloses an annular construction by two pairs of orthogonally polarized dipoles.

<CIT> discloses asymmetric dipoles with a first active element having first electrical characteristics and a second active element having second electrical characteristics, the active elements having different shape and thus different electrical characteristics.

<CIT> discloses first to fourth dipoles included in the first radiating element module having at least one bent part among external ends of the dipole element.

<CIT> discloses a dual-polarized radiating element with a first dipole arm and a second dipole arm of a first dipole radiator extending upwardly and to a first side, respectively, and a third dipole arm and a fourth dipole arm of a second dipole extending downwardly and to the first side, respectively, operating in L-band.

Pursuant to embodiments of the present invention, dual-polarized radiating elements for base station antennas are provided that include first and second dipole radiators according to the appended claims. The first dipole radiator includes a first dipole arm that is configured to have an average current direction that extends in a first direction and a second dipole arm that is configured to have an average current direction that extends in a second direction, where the second direction forms a first oblique angle with the first direction. The second dipole radiator includes a third dipole arm that is configured to have an average current direction that extends in the third direction and a fourth dipole arm that is configured to have an average current direction that extends in a fourth direction, where the fourth direction forms a second oblique angle with the third direction.

In some embodiments, the first oblique angle may be substantially the same as the second oblique angle. In some embodiments, the first and second oblique angles may be obtuse angles, while in other embodiments the first and second oblique angles may be acute angles.

In some embodiments, at least one of the first and second dipole arms may include a plurality of spaced-apart conductive members that are connected to each other via respective inductive trace segments.

In some embodiments, at least one of the first through fourth dipole arms may be in the form of a conductive loop. For example, all of the first through fourth dipole arms may be conductive loops, where each conductive loop includes a plurality of conductive members and a plurality inductive trace segments, the inductive trace segments being narrower than the conductive members.

According to the invention, the first dipole radiator may be configured to transmit RF radiation having slant -<NUM>° polarization, and the second dipole radiator may be configured to transmit RF radiation having slant +<NUM>° polarization.

According to the invention, the first through fourth dipole arms may meet in a central region of the radiating element, and the first dipole arm may extend upwardly from the central region, the third dipole arm may extend downwardly from the central region, and the second and fourth dipole arms may both extend to a first side of the central region.

Pursuant to further embodiments of the present invention, dual-polarized radiating elements for base station antennas are provided that include first and second dipole radiators. The first dipole radiator includes a first dipole arm that generally extends along a first axis and a second dipole arm that generally extends along a second axis that is different from the first axis and a second dipole radiator that includes a third dipole arm that generally extends along the first axis and a fourth dipole arm that generally extends along a third axis that is different from the first axis. At least one of the first through fourth dipole arms comprises a cloaked dipole arm that include inductive elements that are configured to suppress currents in a higher frequency band.

In some embodiments, each of the first through fourth dipole arms may comprise a conductive loop. In some embodiments, each conductive loop may have first and second spaced apart opposed segments, and a first segment of the first dipole arm may be substantially collinear with a first segment of the third dipole arm.

In some embodiments, each conductive loop may have first and second spaced apart opposed segments, and a first segment of the second dipole arm may be substantially parallel to a first segment of the fourth dipole arm.

In some embodiments, the first through fourth dipole arms may each include a plurality of spaced-apart conductive members that are connected to each other via respective inductive trace segments.

In some embodiments, the first dipole arm may be configured to have an average current direction that extends in a first direction and the second dipole arm may be configured to have an average current direction that extends in a second direction, where the first and second directions intersect to define an obtuse angle.

In some embodiments, the first dipole radiator may be configured to transmit RF radiation having slant -<NUM>° polarization, and the second dipole radiator may be configured to transmit RF radiation having slant +<NUM>° polarization.

In some embodiments, the first through fourth dipole arms may meet in a central region of the radiating element, and the first dipole arm may extend upwardly from the central region, the third dipole arm may extend downwardly from the central region, and the second and fourth dipole arms may both extend to a first side of the central region.

Pursuant to additional embodiments of the present invention, dual-polarized radiating elements for base station antennas are provided that include a feed stalk and a dipole radiator printed circuit board mounted on the feed stalk, the dipole radiator printed circuit board including first through fourth dipole arms that extend from a central region where the feed stalk electrically connects to the dipole radiator printed circuit board. The first dipole arm extends generally upwardly from the central region, the third dipole arm extends generally downwardly from the central region, and the second and fourth dipole arms both extend generally to a first side of the central region.

In some embodiments, each of the first through fourth dipole arms may comprise a conductive loop.

In some embodiments, the first and third dipole arms may form a first dipole radiator and the second and fourth dipole arms may form a second dipole radiator.

In some embodiments, each conductive loop may have first and second opposed segments, and a first segment of the second dipole arm may extend substantially parallel to a first segment of the fourth dipole arm.

In some embodiments, a first segment of the first dipole arm may extend substantially collinear to a first segment of the third dipole arm.

In some embodiments, the first dipole arm may be configured to have an average current direction that extends in a first direction and the second dipole arm may be configured to have an average current direction that extends in a second direction, where the first and second directions intersect to define a first obtuse angle.

In some embodiments, the third dipole arm may be configured to have an average current direction that extends in a third direction and the fourth dipole arm may be configured to have an average current direction that extends in a fourth direction, where the third and fourth directions intersect to define a second obtuse angle.

In some embodiments, the first obtuse angle may be equal to the second obtuse angle.

Pursuant to further embodiments of the present invention, dual-polarized radiating elements for base station antennas are provided that include first and second dipole radiators. The first dipole radiator includes a first dipole arm and a second dipole arm and the second dipole radiator that includes a third dipole arm and a fourth dipole arm. The first and third dipole arms each include first and second spaced apart segments, where the first segment of the first dipole arm is collinear with the first segment of the third dipole arm.

In some embodiments, the second and fourth dipole arms each include first and second spaced apart segments, where the first segment of the first dipole arm is parallel to the first segment of the fourth dipole arm.

In some embodiments, the first segment of the first dipole arm may not be collinear with the first segment of the fourth dipole arm.

Pursuant to yet additional embodiments, base station antennas are provided that include a reflector, a first array comprising a first vertically-extending column of lower-band radiating elements that are mounted to extend forwardly from the reflector, a second array comprising a second vertically-extending column of lower-band radiating elements that are mounted to extend forwardly from the reflector, and a multi-column array of higher-band radiating elements that is positioned between the first array and the second array. The first and second arrays each include at least one radiating element of a first type that is horizontally adjacent the multi-column array of higher-band radiating elements and at least one radiating element of a second type that is not horizontally adjacent the multi-column array of higher-band radiating elements, wherein the first type is different from the second type. At least one of the radiating elements in the first array of lower-band radiating elements includes cloaked dipole arms that have inductive elements that are configured to suppress currents in an operating frequency band of the multi-column array.

In some embodiments, the first array of lower-band radiating elements may extend along a first side of the reflector and the second array of lower-band radiating elements may extend along a second side of the reflector.

In some embodiments, the radiating element of the first type may include a first dipole radiator that includes a first dipole arm that is configured to have an average current direction that extends in a first direction and a second dipole arm that is configured to have an average current direction that extends in a second direction, where the second direction forms a first oblique angle with the first direction, and a second dipole radiator that includes a third dipole arm that is configured to have an average current direction that extends in a third direction and a fourth dipole arm that is configured to have an average current direction that extends in a fourth direction, where the third direction forms a second oblique angle with the fourth direction.

In some embodiments, the first oblique angle may be substantially the same as the second oblique angle. In some embodiments, the first and second oblique angles may be obtuse angles.

In some embodiments, at least one of the first through fourth dipole arms may be in the form of a conductive loop.

In some embodiments, the radiating element of the second type may comprise a cross-dipole radiating element that includes a pair of dipole radiators that each comprise two collinear dipole arms.

In some embodiments, the radiating element of the first type may comprise first through fourth dipole arms that meet in a central region of the radiating element, and the first dipole arm extends upwardly from the central region, the third dipole arm extends downwardly from the central region, and the second and fourth dipole arms both extend to a first side of the central region.

In some embodiments, the radiating element of the first type may comprise a first dipole radiator that includes a first dipole arm and a second dipole arm that is not collinear with the first dipole arm and a second dipole radiator that includes a third dipole arm and a fourth dipole arm that is not collinear with the third dipole arm.

Pursuant to embodiments of the present invention, low-band radiating elements are provided that may be used in base station antennas that also include a massive MIMO array. The low-band radiating elements according to embodiments of the present invention may comprise modified tri-pol radiating elements that include a total of four dipole arms. The dipole arms include a generally upwardly extending dipole arm and a first generally laterally extending dipole arm that together form a first dipole radiator, and a generally downwardly extending dipole arm and a second generally laterally extending dipole arm that together form a second dipole radiator. The first and second laterally extending arms extend from the same side of an axis defined by the upwardly and downwardly extending dipole arms. The low-band radiating elements may be cloaked low-band radiating elements that are configured to be substantially transparent to RF energy in the operating frequency band of the massive MIMO array.

The first dipole arm may be configured so that when the first dipole radiator is excited the current flowing on the first dipole arm will have an average current direction that extends in a first direction, and the second dipole arm may be configured so that when the first dipole radiator is excited the current flowing on the second dipole arm will have an average current direction that extends in a second direction, where the second direction forms a first oblique angle with the first direction. Similarly, the third dipole arm may be configured so that when the second dipole radiator is excited the current flowing on the third dipole arm will have an average current direction that extends in a third direction, and the fourth dipole arm may be configured so that when the second dipole radiator is excited the current flowing on the fourth dipole arm will have an average current direction that extends in a fourth direction, where the third direction forms a second oblique angle with the fourth direction. The first and second oblique angles may be obtuse angles in some embodiments, while the first and second dipole radiators may be configured to transmit RF radiation having slant -<NUM>° and slant +<NUM>° polarization. These radiating elements may be particularly well-suited for use in base station antennas that have a multi-column array that operates in a higher frequency band than the radiating elements according to embodiments of the present invention.

One problem with including arrays of radiating elements that operate in different frequency bands in the same base station antenna is that undesired interactions may occur between the radiating elements that operate in different frequency bands. For example, radiation emitted by the higher band radiating element may induce currents on the dipole arms of nearby lower band radiating elements, which may distort the antenna beam generated by the higher band radiating elements. Such interactions can be reduced by increasing the spacing between the different arrays of radiating elements. However, as base station antennas are being introduced that include large numbers of columns of radiating elements that operate in different frequency bands, using spatial separation becomes impractical.

So-called "cloaked" low-band radiating elements have been developed that are designed to be "transparent" to RF signals in the operating frequency band of nearby higher-band radiating elements. <FIG> illustrate one example of a known cloaked dual-polarized low-band radiating element <NUM>, which is disclosed in <CIT>. The radiating element <NUM> generates both slant -<NUM>° and slant +<NUM>° radiation, and is typically called a "cross-dipole" radiating element as it includes two dipole radiators that form a cross shape when viewed from the front. <FIG> is a side perspective view of two of the conventional cloaked low-band radiating elements <NUM> of the '<NUM> publication mounted on a feed board <NUM>. <FIG> is a front view of one of the cloaked low-band radiating elements <NUM> that better illustrates the design of the dipole radiators thereof.

As shown in <FIG>, each cloaked low-band radiating element <NUM> includes first and second dipole radiators <NUM>-<NUM>, <NUM>-<NUM> that are mounted on a feed stalk <NUM> (which is barely visible in <FIG>). Dipole radiator <NUM>-<NUM> comprises a pair of dipole arms <NUM>-<NUM>, <NUM>-<NUM>, and dipole radiator <NUM>-<NUM> comprises a pair of dipole arms <NUM>-<NUM>, <NUM>-<NUM>. The length of each dipole arm <NUM> may be, for example, approximately <NUM> to <NUM> of an operating wavelength, where the "operating wavelength" refers to the wavelength corresponding to the center frequency of the operating frequency band of the radiating element <NUM>. Each dipole arm <NUM> may be formed as a metal pattern on a printed circuit board <NUM> that includes a plurality of widened conductive elements or "members" <NUM> that are physically and electrically connected by narrow meandered trace segments <NUM>. The narrowed meandered trace sections <NUM> are designed to act as high impedance sections that interrupt currents associated with radiation emitted by a nearby mid-band radiating element (not shown) that otherwise would be induced on the dipole arms <NUM>. In particular, the narrowed meandered trace sections <NUM> may act like inductors that help to interrupt currents in the mid-band frequency range while allowing currents in the low-band frequency range to pass between adjacent widened conductive members <NUM>. Thus, the narrowed meandered trace sections <NUM> may create a high impedance for mid-band currents without significantly impacting the ability of the low-band currents to flow on the dipole arms <NUM>. As such, the narrowed meandered trace sections <NUM> may reduce induced mid-band currents on the low-band radiating element <NUM> and consequent disturbance to the antenna pattern of nearby mid-band linear arrays (not shown).

While radiating element <NUM> may facilitate tightly packing both low-band and mid-band linear arrays into a base station antenna, other problems may arise when both low-band linear arrays and a massive MIMO high-band array are implemented in the same antenna, such as the antenna <NUM> of <FIG> discussed above. In particular, the high-band radiating elements in a massive MIMO array are typically closely packed together such that there may not be physical room between adjacent high-band radiating elements to mount the feed stalks for the low-band radiating elements. If that is the case, the feed stalks for the low-band radiating elements must be mounted on either side of the massive MIMO high-band array. Given the large physical size of the low-band radiating elements and the width of an eight column massive MIMO high-band array, the width of the antenna may become very large. Moreover, even if the feed stalks for the low-band radiating elements could potentially be fit in-between clusters of high-band radiating elements, in some applications the high-band array must be a modular array that can be removed and replaced, which precludes mounting low-band radiating elements within the footprint of the high-band array.

Another known dual-polarized radiating element is the so-called "tri-pol" radiating element. <FIG> is a schematic view of a conventional tri-pol radiating element that illustrates the operation thereof, while <FIG> is a perspective view of an actual implementation of the tri-pol radiating element of <FIG>. Both figures are taken from U. Patent No. <NUM><NUM>,<NUM>. As shown in <FIG>, the conventional tri-pol radiating element <NUM> has three arms: namely a pair of side arms <NUM>-<NUM>, <NUM>-<NUM> and a central arm <NUM>. The length of each arm <NUM>, <NUM> may be about one quarter wavelength of the center frequency of the operating frequency band. As shown schematically in <FIG>, the side arms <NUM>-<NUM>, <NUM>-<NUM> are connected to the central conductors of respective coaxial feed lines <NUM>-<NUM>, <NUM>-<NUM>, while central arm <NUM> is connected to the respective outer conductors of coaxial feed lines <NUM>-<NUM>, <NUM>-<NUM>. The outer conductors of coaxial feed lines <NUM>-<NUM>, <NUM>-<NUM> are connected to a reflector R of the base station antenna. The tri-pol radiating element <NUM> may be considered as a combination of two dipole radiators with arms bent by <NUM> degrees. Referring to <FIG>, an equivalent diagram shows the current directions on the dipole arms <NUM>, <NUM> and the polarization vectors of the radiation field (+<NUM>° and -<NUM>° slant polarizations). The +<NUM>° slant and the -<NUM>° slant are with respect to side arms <NUM> and <NUM>. Thus, side arms <NUM>-<NUM> and <NUM>-<NUM> may be oriented horizontally or vertically with respect to the longitudinal axis of the reflector R to achieve +/-<NUM>° slant polarization.

The tri-pol radiating element <NUM> is physically smaller than a conventional cross dipole radiating element. Additionally, the feed stalks <NUM> for the tri-pol radiating element <NUM> are not directly behind the center of the radiating element <NUM>, as is the case with respect to most conventional cross-dipole radiating elements, but instead is offset to one side. As such, columns of tri-pol radiating elements <NUM> could be mounted on either side of a high-band array without extending the width of the antenna as much as would an array of conventional cross-dipole radiating elements.

Unfortunately, however, undesired interaction may occur between low-band and high-band radiating elements when they are in close proximity to each other, just as can happen with low-band and mid-band radiating elements, as discussed above. Such interaction may cause a scattering of the high-band RF signals that can negatively impact various characteristics of the high-band antenna beams including the azimuth and elevation beamwidths, beam squint, antenna beam pointing angle, gain, front-to-back ratio, cross-polarization discrimination and the like. Moreover, the effects of scattering may vary significantly with frequency, which may make it hard to compensate for these effects using other techniques.

As noted above, pursuant to embodiments of the present invention, modified tri-pol radiating elements for base station antennas are provided that may allow for compact base station antennas that have a massive MIMO high-band array interposed between a pair of low-band linear array of radiating elements. The modified tri-pol radiating elements according to embodiments of the present invention may be cloaked radiating elements and may be mounted very close to the edge of a reflector of a base station antenna. In some embodiments, the low-band linear arrays may be implemented entirely using the modified tri-pol radiating elements according to embodiments of the present invention. However, in other embodiments, the low-band linear arrays may include a mixture of cross-dipole and modified tri-pol radiating elements, which may provide enhanced performance in some applications.

Pursuant to some embodiments, dual-polarized radiating elements are provided that include a first dipole radiator that has a first dipole arm that is configured to have an average current direction that extends in a first direction and a second dipole arm that is configured to have an average current direction that extends in a second direction, where the second direction forms a first oblique angle with the first direction. These dual-polarized radiating elements also include a second dipole radiator that has a third dipole arm that is configured to have an average current direction that extends in a third direction and a fourth dipole arm that is configured to have an average current direction that extends in a fourth direction, where the third direction forms a first oblique angle with the fourth direction.

In some embodiments, the first and second oblique angles may be obtuse angles. In other embodiments, the first and second oblique angles may be acute angles. The first and second oblique angles may be the same in some embodiments. In each of these embodiments, the first dipole radiator may be configured to transmit RF radiation having slant -<NUM>° polarization, and the second dipole radiator may be configured to transmit RF radiation having slant +<NUM>° polarization.

Pursuant to additional embodiments, a dual-polarized radiating element is provided that include a first dipole radiator that has a first dipole arm that generally extends along a first axis and a second dipole arm that generally extends along a second axis that is different from the first axis, and a second dipole radiator that has a third dipole arm that generally extends along the first axis and a fourth dipole arm that generally extends along a third axis that is different from the first axis. At least one of the first through fourth dipole arms may be a cloaked dipole arm that include inductive elements that are configured to suppress currents in a higher frequency band.

Pursuant to other embodiments, a dual-polarized radiating element is provided that include a feed stalk and a dipole radiator printed circuit board mounted on the feed stalk. The dipole radiator printed circuit board includes first through fourth dipole arms that extend from a central region where the feed stalk electrically connects to the dipole radiator printed circuit board. The first dipole arm extends generally upwardly from the central region, the third dipole arm extends generally downwardly from the central region, and the second and fourth dipole arms both extend generally to a first side of the central region.

Pursuant to still other embodiments, dual-polarized radiating elements are provided that include a first dipole radiator that includes a first dipole arm and a second dipole arm and a second dipole radiator that includes a third dipole arm and a fourth dipole arm. The first and third dipole arms each include first and second spaced apart segments, where the first segment of the first dipole arm is collinear with the first segment of the third dipole arm. The second and fourth dipole arms may also each include first and second spaced apart segments, where the first segment of the second dipole arm is parallel to the first segment of the fourth dipole arm. The first segment of the second dipole arm may not be collinear with the first segment of the fourth dipole arm.

Pursuant to further aspects of the present invention, base station antennas are provided that include a reflector, a first array comprising a first vertically-extending column of lower-band radiating elements that are mounted to extend forwardly from the reflector, a second array comprising a second vertically-extending column of lower-band radiating elements that are mounted to extend forwardly from the reflector, and a multi-column array of higher-band radiating elements that is positioned between the first array and the second array. The first and second arrays each include at least one radiating element of a first type that is horizontally adjacent the multi-column array of higher-band radiating elements and at least one radiating element of a second, different, type that is not horizontally adjacent the multi-column array of higher-band radiating elements. At least one of the radiating elements in the first array of lower-band radiating elements includes cloaked dipole arms that have inductive elements that are configured to suppress currents in an operating frequency band of the multi-column array.

In some embodiments, the first array of lower-band radiating elements extends along a first side of the reflector and the second array of lower-band radiating elements extends along a second side of the reflector. In some embodiments, the radiating element of the first type comprises any of the radiating elements according to embodiments of the present invention that are disclosed herein. In some embodiments, the radiating element of the second type may comprise a cross-dipole radiating element that includes a first dipole radiator having first and second collinear dipole arms and a second dipole radiator having third and fourth collinear dipole arms.

Embodiments of the present invention will now be described in further detail with reference to <FIG>.

<FIG> and <FIG> illustrate a base station antenna <NUM> according to certain embodiments of the present invention. In particular, <FIG> is a perspective view of the base station antenna <NUM>, while <FIG> is a front view of the base station antenna <NUM> with the radome removed that schematically illustrates the linear arrays of radiating elements included in the antenna <NUM>.

As shown in <FIG>, the base station antenna <NUM> is an elongated structure that extends along a longitudinal axis L. The base station antenna <NUM> may have a tubular shape with a generally rectangular cross-section. The antenna <NUM> includes a radome <NUM> and a bottom end cap <NUM>. A plurality of RF connectors <NUM> may be mounted in the bottom end cap <NUM>. The antenna <NUM> is typically mounted in a vertical configuration (i.e., the longitudinal axis L may be generally perpendicular to a plane defined by the horizon when the antenna <NUM> is mounted for normal operation).

Referring to <FIG>, the base station antenna <NUM> includes an antenna assembly <NUM> that may be slidably inserted into the radome <NUM>. The antenna assembly <NUM> includes a backplane structure <NUM> that may act as both a ground plane and as a reflector for the antenna <NUM>.

First and second low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> that each include a plurality of low-band radiating elements are mounted to extend forwardly from the reflector <NUM>. Two different styles of low-band radiating elements, namely low-band radiating elements <NUM> and low-band radiating element <NUM> are included in each low-band linear array <NUM>. First through fourth mid-band linear arrays <NUM>-<NUM> through <NUM>-<NUM> that each include a plurality of mid-band radiating elements <NUM> are also mounted to extend forwardly from the reflector <NUM>. The first and fourth mid-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> are mounted on the left and right edges of the reflector <NUM>, outside of the respective first and second low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM>. The second and third mid-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> are mounted between the first and second low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM>.

The first and second low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> each extend for substantially the full length of the reflector <NUM>. The first through fourth mid-band linear arrays <NUM>-<NUM> through <NUM>-<NUM> are mounted along a lower portion 318A of the reflector <NUM>, and do not extend for the full length of the reflector <NUM>. As noted above, the first and second low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> each include two different types of radiating elements <NUM>, <NUM>. The radiating elements <NUM> are cross-dipole radiating elements that include first and second dipole radiators that are arranged at angles of +<NUM>° and -<NUM>° with respect to the horizon when the base station antenna <NUM> is mounted for use. The radiating elements <NUM> may be implemented, for example, using any of the cloaking cross-dipole low-band radiating elements disclosed in the above-referenced '<NUM> publication, although embodiments of the invention are not limited thereto. The bottom four low-band radiating elements of each low-band linear array <NUM> are implemented as radiating elements <NUM>. The radiating elements <NUM> may all be in the lower portion 318A of the base station antenna <NUM>.

The radiating elements <NUM> are modified tri-pol radiating elements according to embodiments of the present invention, and will be discussed in more detail below with reference to <FIG>.

As is further shown in <FIG>, the base station antenna <NUM> further includes a multi-column high-band array <NUM> of high-band radiating elements <NUM>. The multi-column high-band array <NUM> is positioned between low-band linear arrays <NUM>-<NUM>, <NUM>-<NUM> in the upper portion 318B of the antenna <NUM> between the three modified tri-pol radiating elements <NUM> that are included in each low-band linear array <NUM>-<NUM>, <NUM>-<NUM>.

In order to reduce the width W of antenna <NUM>, the outer columns of radiating elements <NUM> in high-band array <NUM> may be in close proximity to the tri-pol radiating elements <NUM>. While not shown in <FIG>, the low-band radiating elements <NUM> extend farther forwardly from the reflector <NUM> than do the high-band radiating elements <NUM>, and portions of the low-band radiating elements <NUM> may "cover" some of the high-band radiating elements <NUM>, meaning that an axis that is perpendicular to the reflector <NUM> may extend through both the low-band radiating element <NUM> and the high-band radiating element <NUM>.

In an example embodiment, the low-band radiating elements <NUM>, <NUM> may each be configured to transmit and receive signals in at least a portion of the <NUM>-<NUM> frequency range. The mid-band radiating elements <NUM> may be configured to transmit and receive signals in a higher frequency range than the low-band radiating elements <NUM>, <NUM>, such as the <NUM>-<NUM> frequency range or a smaller portion thereof. The high-band radiating elements <NUM> may be configured to transmit and receive signals in a higher frequency range than the mid-band radiating elements <NUM>, such as the <NUM>-<NUM> and/or <NUM>-<NUM> frequency ranges or smaller portions thereof. In some cases, the high-band radiating elements <NUM> may be configured to transmit and receive signals in an upper portion of a mid-band frequency range such as <NUM>-<NUM>. It will be appreciated, however, that embodiments of the present invention are not limited to the example embodiments discussed above.

All of the radiating elements <NUM>, <NUM>, <NUM>, <NUM> may comprise dual-polarized radiating elements. Consequently, each array <NUM>, <NUM>, <NUM> may be used to form two separate antenna beams, namely an antenna beam having a slant +<NUM>° polarization and an antenna beam having a slant -<NUM>° polarization. It will be appreciated that the radiating elements in some or all of the linear arrays may not be perfectly aligned along a vertical axis but instead some of the radiating elements may be horizontally staggered with respect to other of the radiating elements in a particular array. Such a stagger is shown in <FIG> with the tri-pol radiating elements <NUM> positioned more toward the sides of the reflector <NUM> than the cross-dipole radiating elements <NUM>. Staggered linear arrays may be used, for example, to narrow the azimuth beamwidth of the antenna beams generated by the linear array.

<FIG> is a side perspective view of a tri-pol low-band radiating element <NUM> according to embodiments of the present invention. <FIG> is a front view of the cloaked tri-pol low-band radiating element <NUM> of <FIG>. The tri-pol low-band radiating element <NUM> may be used, for example, to implement the low-band radiating elements <NUM> included in base station antenna <NUM>. Note that the tri-pol radiating elements according to embodiments of the present invention may include four dipole arms. Nevertheless, they are still referred to herein as "tri-pol" radiating elements or as "modified tri-pol" radiating elements since the overall design of the radiating element is more akin to a tri-pol radiating element than it is to a convention cross-polarized radiating element.

Referring to <FIG>, the cloaked tri-pol low-band radiating element <NUM> includes a pair of feed stalks <NUM>-<NUM>, <NUM>-<NUM>, and first and second dipole radiators <NUM>-<NUM>, <NUM>-<NUM>. The first dipole radiator <NUM>-<NUM> includes first and second dipole arms <NUM>-<NUM>, <NUM>-<NUM>, and the second dipole radiator <NUM>-<NUM> includes third and fourth dipole arms <NUM>-<NUM>, <NUM>-<NUM>. The first and third dipole arms <NUM>-<NUM>, <NUM>-<NUM> generally extend along a first vertical axis A1 and the second and fourth dipole arms <NUM>-<NUM>, <NUM>-<NUM> generally extend along respective second and third axes A2, A3 that are horizontal axes. Thus, tri-pol radiating element <NUM> includes a first dipole radiator <NUM>-<NUM> that has a first dipole arm <NUM>-<NUM> that generally extends along the first (vertical) axis A1 and a second dipole arm <NUM>-<NUM> that generally extends along a second (horizontal) axis A2, and a second dipole radiator <NUM>-<NUM> that has a third dipole arm <NUM>-<NUM> that generally extends along the first vertical axis A1 and a fourth dipole arm that generally extends along a third (horizontal) axis A3.

The first and second dipole radiators <NUM>-<NUM>, <NUM>-<NUM> together have a shape similar to the Greek letter π (turned sideways in the view of <FIG>) when viewed from the front. In the depicted embodiment, dipole radiators <NUM>-<NUM>, <NUM>-<NUM> are implemented on a common printed circuit board <NUM>, although multiple printed circuit boards can be used in other embodiments, and/or the dipole radiators <NUM>-<NUM>, <NUM>-<NUM> may be implemented using sheet metal or in other ways.

The feed stalks <NUM> may extend in a direction that is generally perpendicular to a plane defined by the printed circuit board <NUM>. The feed stalks <NUM> may have RF transmission lines <NUM> formed thereon (see <FIG>) that are used to pass RF signals between the dipole radiators <NUM> and a feed network of a base station antenna that includes the tri-pol radiating element <NUM> (e.g., base station antenna <NUM> of <FIG>). The feed stalks <NUM> may be used to mount the dipole radiators <NUM> at an appropriate distance in front of the reflector <NUM> of base station antenna <NUM>, which is often approximately <NUM>/<NUM> to ¼ an operating wavelength. The "operating wavelength" refers to the wavelength corresponding to the center frequency of the operating frequency band of the radiating element <NUM>. Moreover, while the dipole radiators <NUM>-<NUM>, <NUM>-<NUM> extend in a plane that is generally parallel to the plane defined by an underlying reflector, it will be appreciated that in other embodiments the dipole arms <NUM>-<NUM>, <NUM>-<NUM> could be rotated <NUM>° along their respective longitudinal axes to be perpendicular to the reflector (or rotated at some other angle). The low-band radiating element <NUM> may be designed, for example, to operate in some or all the <NUM>-<NUM> frequency band.

<FIG> is a front view of radiating element <NUM> that more clearly shows the design of the dipole radiators <NUM>-<NUM>, <NUM>-<NUM> and the dipole arms <NUM>-<NUM> through <NUM>-<NUM> that form the dipole radiators <NUM>.

Referring to <FIG>, it can be seen that in radiating element <NUM>, the first through fourth dipole arms <NUM>-<NUM> through <NUM>-<NUM> each extend from a central region of the printed circuit board <NUM> where the feed stalks <NUM>-<NUM>, <NUM>-<NUM> electrically connect to the dipole radiator printed circuit board <NUM>. The first dipole arm <NUM>-<NUM> extends generally upwardly from the central region, the third dipole arm <NUM>-<NUM> extends generally downwardly from the central region, and the second and fourth dipole arms <NUM>-<NUM>, <NUM>-<NUM> both extend generally to a first side of the central region.

As is also shown in <FIG>, the first and third dipole arms <NUM>-<NUM>, <NUM>-<NUM> each include first and second spaced apart segments <NUM>-<NUM>, <NUM>-<NUM>, where the first segment <NUM>-<NUM> of the first dipole arm <NUM>-<NUM> is collinear with the first segment <NUM>-<NUM> of the third dipole arm <NUM>-<NUM>. The second and fourth dipole arms <NUM>-<NUM>, <NUM>-<NUM> may also each include first and second spaced apart segments <NUM>-<NUM>, <NUM>-<NUM>, where the first segment <NUM>-<NUM> of the second dipole arm <NUM>-<NUM> is parallel to the first segment <NUM>-<NUM> of the fourth dipole arm <NUM>-<NUM>. The first segment <NUM>-<NUM> of the second dipole arm <NUM>-<NUM> may be parallel to, but not collinear with, the first segment <NUM>-<NUM> of the fourth dipole arm <NUM>-<NUM> in some embodiments.

Each dipole arm <NUM> may be formed as a metal pattern on printed circuit board <NUM>. Each metal pattern includes a plurality of widened conductive members <NUM> that are connected by narrowed trace sections <NUM>. The narrowed trace sections <NUM> may be implemented as meandered conductive traces. Herein, a meandered conductive trace refers to a non-linear conductive trace that follows a meandered path to increase the path length thereof. The meandered conductive trace sections <NUM> may have extended lengths yet still have a small physical footprint.

As shown in <FIG>, each dipole arm <NUM> may comprise a loop that includes a series of alternating widened conductive members <NUM> and narrowed trace sections <NUM>. Each pair of adjacent widened conductive members <NUM> may be physically and electrically connected by a respective one of the narrowed trace sections <NUM>. Since the narrowed trace sections <NUM> have a small physical footprint, adjacent widened conductive members <NUM> may be in close proximity to each other so that the widened conductive members <NUM> together appear as a single dipole arm at frequencies within the operating frequency range of the low-band radiating element <NUM>. It will be appreciated that in other embodiments, the dipole arms need not have a closed loop design as explained, for example, in the '<NUM> publication (e.g., the distal ends of two segments that form the loop may not be electrically connected to each other).

As shown best in <FIG>, the widened conductive member at the base or "root" of each dipole arm <NUM> has a slot <NUM> formed therethrough. These slots <NUM> extend all the way through the printed circuit board <NUM>. Tabs (not shown) on each feed stalk <NUM> (which may be feed stalk printed circuit boards) may extend through the respective slots <NUM> allowing the feed stalks to be electrically connected to the respective dipole arms <NUM>, either through galvanic or capacitive connections. The feed stalks <NUM> may be positioned directly behind the slots <NUM> when the radiating element <NUM> is viewed from the front. As is readily apparent, the feed stalks <NUM> are not positioned at the horizontal center of the radiating element <NUM>, but instead are offset to one side. As such, the radiating element <NUM> can be positioned closer to a side of a reflector of a base station antenna than say, for example, the cross-dipole radiating element <NUM> discussed above.

As shown in <FIG>, the dipole arms <NUM>-<NUM> through <NUM>-<NUM> may have similar designs. While not visible in <FIG>, some or all of the widened conductive members <NUM> that are provided on the front side of the printed circuit board <NUM> may optionally be replicated on the back side of the printed circuit board <NUM> and may be aligned with the widened conductive members <NUM> that are provided on the front side of the printed circuit board <NUM>. In embodiments that include widened conductive members <NUM> on the back side of the printed circuit board <NUM>, metal-plated vias (not shown) may be used to electrically connect the widened conductive members <NUM> on the front side of printed circuit board <NUM> to the widened conductive members <NUM> on the rear side of printed circuit board <NUM>, or alternatively, the widened conductive members <NUM> on opposed sides of the printed circuit board <NUM> may be capacitively coupled to each other. Providing widened conductive members <NUM> on both sides of printed circuit boards <NUM> may help increase the operating bandwidth of the low-band radiating element <NUM>.

The narrowed meandered trace sections <NUM> are designed to act as high impedance sections that interrupt currents associated with nearby high-band radiating elements (e.g., a high-band radiating element <NUM> of base station antenna <NUM>) that otherwise would be induced on the dipole arms <NUM>. As discussed above, when a nearby high-band radiating element <NUM> transmits and receives signals, the high-band RF signals may tend to induce currents on the dipole arms <NUM> of the low-band radiating element <NUM>. This can particularly be true when the low-band and high-band radiating elements are designed to operate in frequency bands having center frequencies that are separated by about a factor of four, as a low-band dipole arm <NUM> having a length that is a quarter wavelength of the low-band operating frequency will, in that case, have a length of approximately a full wavelength of the high-band operating frequency. The greater the extent that high-band currents are induced on the low-band dipole arms <NUM>, the greater the impact on the characteristics of the radiation pattern of the high-band array. The narrowed meandered trace sections <NUM> are designed to create the high impedance for high-band currents without significantly impacting the ability of the low-band currents to flow on the dipole arms <NUM>. In some embodiments, the narrowed trace sections <NUM> may make the low-band radiating element <NUM> almost invisible to nearby high-band radiating elements, and thus the low-band radiating element <NUM> may not distort the high-band antenna patterns.

Each widened conductive member <NUM> may have a respective width W<NUM>, where the width W<NUM> is measured in a direction that is generally perpendicular to the direction of current flow along the respective widened conductive member <NUM>. The width W<NUM> of each widened conductive member <NUM> need not be constant. The narrowed trace sections <NUM> may similarly have widths W<NUM>, where each width W<NUM> is measured in a direction that is generally perpendicular to the direction of instantaneous current flow along the narrowed trace sections <NUM>. The width W<NUM> of each narrowed trace section <NUM> need not be constant. The average width of each widened conductive member <NUM> may be, for example, at least twice the average width of each narrowed trace section <NUM> in some embodiments. In other embodiments, the average width of each widened conductive member <NUM> may be at least three times, at least five times, or at least seven times the average width of each narrowed trace section <NUM>.

<FIG> are front views of the cloaked tri-pol low-band radiating element <NUM> of <FIG> that illustrate the operation thereof. As shown in <FIG>, dipole radiator <NUM>-<NUM> may be excited by feeding an RF signal to dipole arms <NUM>-<NUM>, <NUM>-<NUM>. In this embodiment, the radiating element <NUM> is designed so that equal magnitude currents will be excited onto each dipole arm <NUM>-<NUM>, <NUM>-<NUM> in response to the RF feed signal. Focusing on dipole arm <NUM>-<NUM>, the average current direction along the dipole arm is shown by line segment labelled <NUM>-<NUM>. Likewise, on dipole arm <NUM>-<NUM>, the average current direction along the dipole arm is shown by line segment labelled <NUM>-<NUM>. The segments <NUM>-<NUM>, <NUM>-<NUM> that represent the average current direction along dipole arms <NUM>-<NUM>, <NUM>-<NUM>, respectively, intersect at an angle θ<NUM>. Angle θ<NUM> is an oblique angle and, more particularly, in the depicted embodiment is an obtuse angle.

<FIG> illustrates the desired polarization for the antenna beam generated by dipole radiator <NUM>-<NUM> (which include dipole arms <NUM>-<NUM>, <NUM>-<NUM>), which is a slant -<NUM>° polarization.

<FIG> illustrates the average current direction along each dipole arm <NUM> as well as the polarization of the antenna beams generated by dipole radiators <NUM>-<NUM>, <NUM>-<NUM>. The average current directions <NUM>-<NUM>, <NUM>-<NUM> for dipole arms <NUM>-<NUM>, <NUM>-<NUM>, respectively, are discussed above. The average current direction along dipole arm <NUM>-<NUM> is shown by line segment labelled <NUM>-<NUM> and the average current direction along dipole arm <NUM>-<NUM> is shown by line segment labelled <NUM>-<NUM>. The segments <NUM>-<NUM>, <NUM>-<NUM> intersect at an angle θ<NUM>. Angle θ<NUM> is an oblique angle and, more particularly, in the depicted embodiment is an obtuse angle. Dashed line <NUM>-<NUM> shows the polarization of dipole radiator <NUM>-<NUM> and dashed line <NUM>-<NUM> shows the polarization of dipole radiator <NUM>-<NUM>. As can be seen, the dipole radiators <NUM>-<NUM>, <NUM>-<NUM> generate antenna beams having slant -<NUM>° and slant +<NUM>° polarization, respectively. Thus, the angles θ<NUM> and θ<NUM> are selected so that given the average current direction along the dipole arms of dipole radiators <NUM>-<NUM>, <NUM>-<NUM> the dipole radiators will generate antenna beams having slant -<NUM>° and slant +<NUM>° polarization, respectively.

As discussed above, pursuant to embodiments of the present invention, base station antennas are provided that include at least one vertically-extending low-band linear array and a multi-column high-band array. The at least one low-band linear array may include at least two different types of lower-band radiating elements. <FIG> schematically illustrated such a base station antenna. <FIG> illustrate another example of such a base station antenna <NUM>'. In particular, <FIG> is a schematic front view of base station antenna <NUM>', while <FIG> is a schematic top view of the base station antenna <NUM>' that illustrates how the use of the modified tri-pol radiating elements according to embodiments of the present invention provides room for more columns of radiating elements in the massive MIMO array.

As shown in <FIG>, base station antenna <NUM>' includes a reflector <NUM>, a first low-band array <NUM>-<NUM> comprising a first vertically-extending column of low-band radiating elements <NUM>, <NUM> that are mounted to extend forwardly from the reflector <NUM>, a second low-band array <NUM>-<NUM> comprising a second vertically-extending column of low-band radiating elements <NUM>, <NUM> that are mounted to extend forwardly from the reflector <NUM>, and a multi-column array <NUM> of high-band radiating elements (not individually shown) that is positioned between the first and second low-band arrays <NUM>-<NUM>, <NUM>-<NUM>. Each low-band array <NUM> may extend for most or all of the length of the base station antenna <NUM>'. In contrast, the high-band array <NUM> may be much shorter, and in the depicted embodiment is located in the upper half of base station antenna <NUM>'.

The first and second low-band arrays <NUM>-<NUM>, <NUM>-<NUM> each include two different types of radiating elements, namely cross-dipole radiating elements <NUM> as well as modified tri-pol radiating elements <NUM> according to embodiments of the present invention. As can be seen, the cross-dipole low-band radiating elements <NUM> are used in the portions of linear arrays <NUM>-<NUM>, <NUM>-<NUM> that are not horizontally adjacent to the high-band array <NUM>, while modified tri-pol radiating elements <NUM> according to certain embodiments of the present invention are used in the portions of linear arrays <NUM>-<NUM>, <NUM>-<NUM> that are horizontally adjacent to the high-band array <NUM>. As shown, the modified tri-pol radiating elements <NUM> may be positioned significantly closer to the side edges of the reflector <NUM> than the cross-dipole radiating elements <NUM>. Consequently, there is more room in the upper middle portion of the reflector <NUM> for the high-band array <NUM>. As shown in <FIG>, modified tri-pol radiating elements <NUM> may be positioned so that the dipole arms thereof extend substantially to the edge of the reflector <NUM> in order to reduce the width of the base station antenna <NUM>'. This may slightly degrade the performance of the low-band arrays <NUM> since the modified tri-pol radiating elements <NUM> do not have an optimum amount of reflector behind them, but this degradation may often be acceptable, particularly since most of the radiating elements <NUM> in the low-band arrays <NUM> are positioned more inwardly on the reflector <NUM>. Additionally, this arrangement where the modified tri-pol radiating elements <NUM> are positioned are outwardly than the cross-dipole radiating elements <NUM> creates a horizontal stagger in the linear arrays <NUM>, which may assist in narrowing the azimuth beamwidth of the antenna beams generated by the low-band linear arrays. This may result in enhanced performance and/or allow for the use of slightly smaller low-band radiating elements <NUM>, <NUM>, both of which are beneficial.

The modified tri-pol radiating elements <NUM> are implemented as cloaked radiating elements that may be substantially transparent to RF energy in the operating frequency band of the high-band array <NUM>. The cross-dipole radiating elements <NUM> are also implemented as cloaked radiating elements because, while not shown, additional arrays of radiating elements may be mounted on the lower portion of the reflector <NUM>. The cross-dipole radiating elements <NUM> may be designed to be transparent to RF energy in the operating frequency bands of any such arrays. For example, as discussed above with respect to <FIG>, a plurality of linear arrays of mid-band radiating elements may be included in antenna <NUM>'. If such mid-band linear arrays are included in base station antenna <NUM>, the cross-dipole radiating elements <NUM> may be designed to be transparent to RF energy in, for example, some or all of the <NUM>-<NUM> frequency bands.

<FIG> are schematic front views of modified tri-pol low-band radiating elements according to further embodiments of the present invention.

Referring to <FIG>, a modified tri-pol radiating element <NUM> includes a first dipole radiator that has dipole arms <NUM>-<NUM>, <NUM>-<NUM> and a second dipole radiator that has dipole arms <NUM>-<NUM>, <NUM>-<NUM>. While the dipole arms <NUM> are shown schematically in <FIG> as bold line segments, it will be appreciated that any dipole arm design may be used to form the dipole arms, including straight dipole arms (which may or may not be cloaked designs), loop dipole arms, leaf-shaped dipole arms, etc. The modified tri-pol radiating element <NUM> differs from the modified tri-pol radiating element <NUM> that is discussed above in that dipole arms <NUM>-<NUM> and <NUM>-<NUM> do not extend along a common vertical axis, but instead each dipole arm <NUM>-<NUM>, <NUM>-<NUM> is angled with respect to the vertical. Likewise, dipole arms <NUM>-<NUM> and <NUM>-<NUM> do not extend along a respective horizontal axes, but instead each dipole arm <NUM>-<NUM>, <NUM>-<NUM> is angled with respect to the horizontal. As a result, the axes defined by dipole arms <NUM>-<NUM>, <NUM>-<NUM> intersect to define an obtuse angle θ<NUM>, and the axes defined by dipole arms <NUM>-<NUM> and <NUM>-<NUM> intersect to define an obtuse angle θ<NUM>. The obtuse angles θ<NUM> and θ<NUM> may be selected so that dipole radiator <NUM>-<NUM> will emit radiation having a slant -<NUM>° polarization, and so that dipole radiator <NUM>-<NUM> will emit radiation having a slant +<NUM>° polarization.

Referring to <FIG>, a modified tri-pol radiating element <NUM> includes a first dipole radiator that includes dipole arms <NUM>-<NUM>, <NUM>-<NUM> and a second dipole radiator that includes dipole arms <NUM>-<NUM>, <NUM>-<NUM>. While the dipole arms <NUM> are shown schematically in <FIG> as bold line segments, it will be appreciated that any dipole arm design may be used to form the dipole arms, including straight dipole arms (which may or may not be cloaked designs), loop dipole arms, leaf-shaped dipole arms, etc. The modified tri-pol radiating element <NUM> differs from the modified tri-pol radiating element <NUM> that is discussed above, except that dipole arms <NUM>-<NUM> and <NUM>-<NUM> intersect to define an acute angle θ<NUM> as opposed to an obtuse angle. Dipole arms <NUM>-<NUM> and <NUM>-<NUM> are configured so that the emitted radiation will have a slant -<NUM>° polarization. Likewise, dipole arms <NUM>-<NUM> and <NUM>-<NUM> intersect to define an acute angle θ<NUM> as opposed to an obtuse angle. Dipole arms <NUM>-<NUM> and <NUM>-<NUM> are configured so that the emitted radiation will have a slant +<NUM>° polarization.

While <FIG> illustrate all of the dipole arms <NUM> of radiating element <NUM> being cloaked dipole arms, embodiments of the invention are not limited thereto. For example, in an alternative embodiment only dipole arms <NUM>-<NUM> and <NUM>-<NUM> may be configured as cloaked dipole arms, and dipole arms <NUM>-<NUM> and <NUM>-<NUM> may be configured as non-cloaked dipole arms (e.g., straight metal arms, metal leaf's, etc.). Thus, it will be appreciated that many modifications may be made to the radiating element <NUM>, for example, without departing from the scope of the appended claims.

It will also be appreciated that the current flow on the two dipole arms of a dipole radiator according to embodiments of the present invention need not be equal. In situations where the current flow is not equal, the angle defined by the intersection of the two dipole arms is modified so that the polarization of the radiating pattern generated by the dipole radiator will have a slant +/-<NUM>° polarization.

The tri-pol radiating elements according to embodiments of the present invention may facilitate implementing two low-band arrays and a massive MIMO high-band array in the same base station antenna while keeping the width of the antenna to a reasonable size. They also facilitate using modular massive MIMO arrays within a base station antenna, since they allow the low-band radiating elements to be positioned very close to the side edges of the reflector. The cloaking design allows the tri-pol radiating elements to be substantially invisible to the radiation emitted by the high-band radiating elements, and hence does not substantially impact characteristics of the high-band antenna beams.

While the discussion above focuses on low-band radiating elements, it will be appreciated that the techniques discussed above can be used with radiating elements that operate in any appropriate frequency band.

Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. 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.

It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

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

Claim 1:
A dual-polarized radiating element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for a base station antenna, comprising:
a first dipole radiator (<NUM>-<NUM>) that includes a first dipole arm (<NUM>-<NUM>, <NUM>-<NUM>) and a second dipole arm (<NUM>-<NUM>, <NUM>-<NUM>);
a second dipole radiator (<NUM>-<NUM>) that includes a third dipole arm (<NUM>-<NUM>, <NUM>-<NUM>) and a fourth dipole arm (<NUM>-<NUM>, <NUM>-<NUM>);
wherein, when the dual-polarized radiating element is viewed from the front, the first through fourth dipole arms (<NUM>-<NUM> - <NUM>-<NUM>, <NUM>-<NUM> - <NUM>-<NUM>) meet in a central region of the radiating element, with the first dipole arm extending upwardly from the central region, the third dipole arm extending downwardly from the central region, and the second and fourth dipole arms both extending to a first side of the central region, wherein the first and second dipole arms have axes that intersect to define a first oblique angle Θ1, and the third and fourth dipole arms have axes that intersect to define a second oblique angle Θ2,
where the oblique angles Θ1 and Θ2 are configured so that the first dipole radiator will emit radiation having a slant -<NUM>° polarization, and so that the second dipole radiator will emit radiation having a slant +<NUM>° polarization,
or, alternatively, the first and second dipole radiators (<NUM>-<NUM>, <NUM>-<NUM>) together have a shape similar to the Greek letter π turned sideways when viewed from the front,
wherein the first dipole radiator (<NUM>-<NUM>) is configured to transmit RF radiation having slant -<NUM>° polarization, and the second dipole radiator (<NUM>-<NUM>) is configured to transmit RF radiation having slant +<NUM>° polarization, and
wherein at least one of the first through fourth dipole arms comprises a cloaked dipole arm that include inductive elements that are configured to suppress currents in a higher frequency band.