Patent Publication Number: US-2023147511-A1

Title: Base station antennas having radomes that reduce coupling between columns of radiating elements of a multi-column array

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Application Ser. No. 17/468,783, filed Sep. 8, 2021, which claims the benefit of and priority to U.S. Provisional Application Ser. No. 63/083,379, filed Sep. 25, 2020, the contents of which are hereby incorporated by reference as if recited in full herein. 
    
    
     BACKGROUND 
     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 cellular communications system, a geographic area is divided into a series of regions or “cells” that are served by respective base stations. Each base station may include one or more base station antennas that are configured to provide two-way radio frequency (“RF”) communications with subscribers that are within the cell served by the base station. In many cases, each base station is divided into “sectors.” In one common configuration, a hexagonally-shaped cell is divided into three 120° sectors in the azimuth plane, and each sector is served by one or more base station antennas that have an azimuth Half Power Beamwidth (HPBW) of approximately 65°. Typically, the base station antennas are mounted on a tower or other raised structure, with the radiation patterns that are generated by the base station antennas directed outwardly. Base station antennas are often implemented as linear or planar phased arrays of radiating elements. 
     Conventionally, most cellular communications systems have operated in frequency bands that are at frequencies of less than 2.8 GHz. In order to accommodate the increasing volume of cellular communications, a variety of new frequency bands are being assigned for cellular communications service. Some of the new frequency bands that are being introduced for cellular communications service are within the 3-6 GHz frequency range. The use of these frequency bands, which may be nearly an order of magnitude higher in frequency than some of the existing cellular frequency bands, may result in new challenges in base station antenna design. Additionally, so-called massive multi-input-multi-output (“MIMO”) arrays are now routinely being included in base station antennas. These massive MIMO arrays typically operate in the higher frequency bands (e.g., above 2.3 GHz) and may include arrays having, for example, four, eight or even sixteen columns of radiating elements. While these massive MIMO arrays can dramatically increase the capacity of a base station antenna, they also raise certain challenges. 
    
    
     
         FIG.  1    illustrates an example of prior art base station antennas  10 . The base station antenna  10  is typically mounted with the longitudinal axis L of the antenna  10  extending along a vertical axis (e.g., the longitudinal axis L may be generally perpendicular to a plane defined by the horizon) when the antenna  10  is mounted for normal operation. The front surface of the antenna  10  is mounted opposite the tower or other mounting structure, pointing toward the coverage area for the antenna  10 . The antenna  10  includes a radome  11  and a top end cap  20 . The antenna  10  also includes a bottom end cap  30  which includes a plurality of connectors  40  mounted therein. As shown, the radome  11 , top cap  20  and bottom cap  30  define an external housing  10   h  for the antenna  10 . An antenna assembly is contained within the housing  10   h.    
     
    
    
     SUMMARY 
     Pursuant to embodiments of the present invention, base station antennas are provided with an internal radome spaced apart, in a front to back direction, from an outer (external) radome. 
     Embodiments of the present invention provide base station antennas with a radome having a plurality of peak segments, separated by valley segment. 
     Each peak segment can be aligned in front of a respective center of a radiating element of a column of a multi-column massive MIMO antenna array. 
     The inner radome may be closely spaced apart from (one wavelength or less) from the outer radome and/or the radiating elements of a massive MIMO antenna array. 
     Embodiments of the invention provide an active antenna module with a radome that is configured to reside inside a base station antenna, closely spaced apart from and facing an outer radome (a passive antenna radome). 
     The radome of the active antenna module can have a plurality of shaped outer facing segments, each shaped segment aligned with one or more column of radiating elements of a massive MIMO antenna array. 
     Embodiments of the invention are directed to a base station antenna that includes: an outer radome defining a front of the base station antenna; an internal radome; and a multi-column antenna array positioned behind the internal radome. 
     The internal radome can be configured with a plurality of peak segments that are laterally spaced apart, and wherein the peak segments project outwardly toward the front of the base station antenna behind the outer radome. 
     A respective peak segment of the plurality of peak segments can reside in front of and longitudinally and/or laterally aligned with at least one radiating element of a corresponding column of radiating elements of the multi-column antenna array. 
     Each peak segment can be separated by a pair of valley segments, one valley segment on a right side and one valley segment on a left side of the peak segment. 
     Each peak segment can be provided as a longitudinally extending peak segment that is positioned over a respective column of the multi-column antenna array to thereby reduce coupling between columns of radiating elements and/or provide a common near field environment for each radiating element and/or each column of radiating elements. 
     The multi-column antenna array can include radiating elements held by respective stalks. Radiating arms of the radiating elements can be positioned at a first distance d 1  from the outer radome and a second distance d 2  from the internal radome. The outer radome can be positioned a third distance d 3  from the internal radome and d 2  can be less than d 1  and d 3 . 
     The multi-column antenna array can have radiating elements with radiating arms. The radiating arms can be positioned at a H wavelength or less from the inner radome, where the wavelength refers to the wavelength corresponding to the center frequency of the operating frequency band of the multi-column array, and the radiating arms can be positioned at 1 wavelength or more from the outer radome. 
     The internal radome can be configured to direct reflected signal back to an originating radiating element and/or column of radiating elements of the multi-column array to thereby reduce scattering and improve antenna performance. 
     A respective peak segment of the plurality of peak segments can define a cavity that is positioned over a respective radiating element of the multi-column antenna array. 
     The cavity can have an arcuate shape with an arc thereof curving over the respective radiating element to provide a maximal front facing portion laterally centered over a center of the respective radiating element. 
     The respective peak segment can merge into right and left side valley segments that project inwardly toward ends of radiating arms of neighboring radiating elements. 
     The plurality of peak segments can be arranged to be in a range of 4 and 16 laterally spaced apart peak segments that extend longitudinally along a length of the internal radome. 
     The internal radome can have opposing right and left sides that extend inwardly and couple to a reflector. 
     The internal radome can be configured to generate a near-field environment that is substantially the same for each radiating element and/or columns of radiating elements of the multi-column array. 
     The internal radome can be configured to cooperate with radiating elements of the multi-column array to provide an isolation of at least 19 dB between radiating elements in adjacent columns. 
     Yet other aspects are directed toward a base station antenna that includes: a reflector; a multi-column antenna array that extends forwardly from the reflector; and a radome that is positioned in front of the multi-column array. The radome includes a plurality of laterally spaced-apart peak segments that project outwardly away from the multi-column array. 
     A respective peak segment of the plurality of peak segments can reside in front of and longitudinally and/or laterally aligned with at least one radiating element of a corresponding column of radiating elements of the multi-column antenna array. 
     Each peak segment can be separated by a pair of valley segments, one valley segment on a right side and one valley segment on a left side of the peak segment. 
     Each peak segment can be provided as a longitudinally extending peak segment that is positioned over a respective column of the multi-column antenna array to thereby reduce coupling between columns of radiating elements and/or provide a common near field environment for each radiating element and/or each column of radiating elements. 
     The multi-column antenna array can include radiating elements held by respective stalks. Radiating arms of the radiating elements can be positioned at a first distance d 1  from the outer radome and a second distance d 2  from the internal radome. The outer radome can be positioned a third distance d 3  from the internal radome, and d 2  can be less than d 1  and d 3 . 
     The multi-column antenna array can have radiating elements with radiating arms. The radiating arms can be positioned at a H wavelength or less from the inner radome, where the wavelength refers to the wavelength corresponding to the center frequency of the operating frequency band of the multi-column array. The radiating arms can be positioned at 1 (one) wavelength or more from the outer radome. 
     The internal radome can be configured to direct reflected signal back to an originating radiating element and/or column of radiating elements of the multi-column array to thereby reduce scattering and improve antenna performance. 
     A respective peak segment of the plurality of peak segments can define a cavity that is positioned over a respective radiating element of the multi-column antenna array. 
     The plurality of peak segments can be arranged to be in a range of 4 and 16 laterally spaced apart peak segments that extend longitudinally along a length of the internal radome. 
     The internal radome can be configured to generate a near-field environment that is substantially the same for each radiating element and/or columns of radiating elements of the multi-column array. 
     The internal radome can be configured to cooperate with radiating elements of the multi-column array to provide an isolation of at least 19 dB between radiating elements in adjacent columns. 
     Still other aspects are directed to base station antennas that have: a reflector; a multi-column antenna array that extends forwardly from the reflector; and a radome that is positioned in front of the multi-column array. The radome includes a plurality of longitudinally extending segments that are aligned in front of respective columns of the multi-column array, where each longitudinally-extending segment has a transverse cross-section that includes sub-segments that are at different front-to back-distances from the reflector. 
     The sub-segments can have respective peak segment that resides in front of and longitudinally and laterally aligned with a respective column of the multi-column antenna array. 
     Each peak segment can be separated by a pair of valley segments, one valley segment on a right side and one valley segment on a left side of the peak segment. 
     The sub-segments each have a peak segment that is positioned over a respective column of the multi-column antenna array to thereby reduce coupling between columns of radiating elements and/or provide a common near field environment for each radiating element and/or each column of radiating elements. 
     The radome can be an internal radome. The base station antenna can further include an external radome that resides in front of the internal radome. The multi-column antenna array can have radiating elements held by respective stalks. Radiating arms of the radiating elements can be positioned at a first distance d 1  from the outer radome and a second distance d 2  from the internal radome. The outer radome can be positioned a third distance d 3  from the internal radome, and d 2  can be less than d 1  and d 3 . 
     The radome can be an internal radome. The base station antenna can further include an external radome that resides in front of the internal radome. The multi-column antenna array can have radiating elements with radiating arms. The radiating arms can be positioned at a ½ wavelength or less from the inner radome, where the wavelength refers to the wavelength corresponding to the center frequency of the operating frequency band of the multi-column array, and the radiating arms can be positioned at 1 (one) wavelength or more from the outer radome. 
     The internal radome can be configured to direct reflected signal back to an originating radiating element and/or column of radiating elements of the multi-column array to thereby reduce scattering and improve antenna performance. 
     A respective peak segment can define a cavity that is positioned over a respective radiating element of a corresponding column of the multi-column antenna array. The plurality of peak segments can be arranged to be in a range of 4 and 16 laterally spaced apart peak segments that extend longitudinally along a length, typically an entire length, of the internal radome. 
     The internal radome can be configured to generate a near-field environment that is substantially the same for each radiating element and/or columns of radiating elements of the multi-column array, and the internal radome can be configured to cooperate with radiating elements of the multi-column array to provide an isolation of at least 19 dB between radiating elements in adjacent columns. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
       FIG.  1    is a front, perspective view of an example prior art base station antenna. 
       FIG.  2    is a simplified section view of a base station antenna according to embodiments of the present invention. 
       FIG.  3    is a simplified schematic illustration of a massive MIMO antenna array with an internal radome according to embodiments of the present invention. 
       FIG.  4    is a front perspective view of an example radome according to embodiments of the present invention. 
       FIG.  5 A  is a section view of a massive MIMO antenna array configured to reside under a curved internal radome. 
       FIG.  5 B  is a section view of a massive MIMO antenna array under a flat internal radome according to embodiments of the present invention. 
       FIG.  5 C  is a section view of a massive MIMO antenna array under a shaped internal radome configured to reduce coupling between one or more adjacent rows and/or columns of radiating (antenna) elements of the massive MIMO antenna array according to embodiments of the present invention. 
       FIGS.  6 A- 6 C  are magnetic field graphs of respective massive MIMO antenna arrays and radomes corresponding to the massive MIMO antenna arrays and internal radomes shown in corresponding  FIGS.  5 A- 5 C , as generated by a computational model. 
       FIG.  7 A  is a graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and curved radome shown in  FIG.  5 A , as generated by a computational model. 
       FIG.  7 B  is a graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and flat radome shown in  FIG.  5 B , as generated by a computational model. 
       FIG.  7 C  is a graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and pattern shaped radome shown in  FIG.  5 C , as generated by a computational model. 
       FIG.  8 A  is a graph of the azimuth pattern for an antenna beam that is not electronically scanned from boresight for the massive MIMO antenna array and flat radome shown in  FIG.  5 B , as generated by a computational model. 
       FIG.  8 B  is a graph of the azimuth pattern for an antenna beam that is electronically scanned from boresight to a maximum scan angle (here 53°) for the massive MIMO antenna array and flat radome shown in  FIG.  5 B , as generated by a computational model. 
       FIG.  9 A  is a graph of the azimuth pattern for an antenna beam that is not electronically scanned from boresight for the massive MIMO antenna array and pattern shaped radome shown in  FIG.  5 C , as generated by a computational model. 
       FIG.  9 B  is a graph of the azimuth pattern for an antenna beam that is electronically scanned from boresight to a maximum scan angle (here 53°) for the massive MIMO antenna array and pattern shaped radome shown in  FIG.  5 C , as generated by a computational model. 
       FIG.  10 A  is a section view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 B  is a section view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 C  is a section view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 D  is a section view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 E  is a front perspective view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 F  is a section view of another embodiment of a pattern shaped radome according to embodiments of the present invention. 
       FIG.  10 G  is a schematic top perspective view of an example pocket shaped segment of a pattern shaped radome configured to cover a single radiating element of a multi-column antenna array according to embodiments of the present invention. 
       FIG.  11    is an enlarged section view of the pattern shaped radome shown in  FIG.  5 C  illustrating an example spacing (H) between a radiating (antenna) element and a maximum outer projection (e.g., peak) of the pattern shaped radome according to embodiments of the present invention. 
       FIG.  12    is a section view that shows example positions, H 1 , H 2 , H 3  for the internal radome relative to an outermost surface of radiating elements of the massive MIMO array and inside an outer radome according to embodiments of the present invention. 
       FIG.  13    is a graph of phase distribution using the position H 1  of  FIG.  12   , generated by a computational model. 
       FIG.  14    is a graph of phase distribution using the position H 2  of  FIG.  12   , generated by a computational model. 
       FIG.  15    is a graph of phase distribution using the position H 3  of  FIG.  12   , generated by a computational model. 
       FIG.  16    is a partially exploded side perspective view of an example active antenna module comprising the shaped internal radome according to embodiments of the present invention. 
       FIGS.  17 A and  17 B  are back perspective views of example antenna base stations comprising a shaped internal radome according to embodiments of the present invention. 
       FIG.  18    is a flow chart of example actions that can be carried out to reduce (near-field) cross-column coupling and/or reflection (scattering) according to embodiments of the present invention. 
     DETAILED DESCRIPTION 
     Referring to  FIG.  2   , the base station antenna  100  typically includes a radome  111  that serves as (defines) at least part of an outer housing  100   h  for the base station antenna  100 . The radome  111  may protect the interior components of the antenna from damage during shipping and installation, and from rain, ice, snow, moisture, wind, insects, birds, and other environmental factors once the base station antenna  100  is installed for use. While base station antenna radomes may be formed of a variety of different materials, fiberglass radomes are the most common, as they are relatively lightweight, exhibit high mechanical strength and are reasonably inexpensive to manufacture. 
     Conventionally, the shape of a radome  111  for a base station antenna  100  is driven by wind loading concerns, as the radome forms most of the exterior of the base station antenna. As base station antennas  100  are often mounted hundreds of feet above the ground and have large surface areas, reducing wind loading may be very important in order to reduce the structural requirements for the mounting structure (e.g., an antenna tower). 
     With the introduction of fifth generation (“5G”) cellular services, the base station antenna  100  can include a massive MIMO antenna array  120  ( FIGS.  3 ,  5 A- 5 C ). “MIMO” refers to a communication technique in which a data stream is divided into individual sub-groups of data that are simultaneously transmitted, at the same frequency and using certain coding techniques, over multiple relatively uncorrelated transmission paths between a transmitting station and a receiving station. In a massive MIMO array  120 , the radiating elements  121  ( FIGS.  3 ,  5 A- 5 C ) are typically implemented as dual-polarized radiating elements. Since the two polarizations at which a dual polarized radiating element transmits and receives RF signals generally are uncorrelated from each other, each column of radiating elements in a massive MIMO array may form two of the relatively uncorrelated transmission paths. 
     Referring to  FIG.  3   , the columns  125  of radiating elements  121 , labeled as columns C 1 -Cn, (C 1 -C 8  in the example embodiment shown) are spaced sufficiently far apart (e.g., at least a wavelength apart) so that the columns  125  will also be sufficiently uncorrelated from each other. Thus, a massive MIMO array having X columns and Y rows, labeled as rows R 1 -Rn (R 1 -R 12  in the example embodiment shown), of dual-polarized radiating elements  121  will typically be operated as a (2*X) MIMO antenna. The columns  125  can have any suitable number of radiating elements  121  such as  6 ,  8 ,  12  and  20 , for example. Further details of example radiating elements  121  can be found in co-pending WO2019/236203 and WO2020/072880, the contents of which are hereby incorporated by reference as if recited in full herein. 
     Base station antennas  100  are also being introduced in which the massive MIMO antenna is an active antenna. An “active antenna” refers to an antenna in which the amplitude and/or phase of the RF signals transmitted and received by each radiating element (or small groups of radiating elements) may be manipulated in order to actively steer the pointing direction and shape of the antenna beams generated by the antenna. In some cases, the massive MIMO active antenna may be provided as an active antenna module  110  ( FIGS.  16 ,  17 A,  17 B ) that may be mounted on, typically coupled to a rear of the antenna  100  or in a conventional passive base station antenna housing  100   h . The module  110  can include both the active radio circuitry as well as the radiating elements  121  that form all or part of the massive MIMO array  120 . 
     As discussed above, each column  125  of a massive MIMO array  120  typically forms two of the multiple transmission paths. As also discussed above, the separate transmission paths used with MIMO communications need to be relatively uncorrelated with respect to each other (e.g., by using polarization diversity and/or physical separation). Of course, the more coupling that occurs between the columns of a massive MIMO antenna, the less the columns will be uncorrelated. Thus, reducing coupling between the columns  125  of a massive MIMO array  120  may be an important performance consideration for a massive MIMO antenna. 
     Unfortunately, the radome  111  of a base station antenna  100  can negatively impact the RF signals transmitted by the radiating elements of the base station antenna. For example, a radome  111  may reflect some of the RF energy transmitted by the linear arrays (columns) of radiating elements  121  of a base station antenna. Such reflections may undesirably increase coupling between the columns  125  of a massive MIMO array. Moreover, since the impact of the radome  111  is a function of the thickness of the radome  111  along the direction of travel of the RF energy, the radome  111  tends to have a greater impact on RF energy emitted at larger angles from the boresight pointing direction of the linear arrays, as at such angles the RF energy travels through more radome material. Consequently, the radome  111  may tend to have a greater impact in cases where the array active beam-steering is used to electronically scan the pointing direction of the antenna beam from the boresight pointing direction of the antenna. Additionally, the degree to which a radome will reflect RF signals tends to increase as the ratio of the thickness of the radome to the wavelength of the RF signal increases. Accordingly, the impact of a radome on the RF signals tends to increase as the thickness of the radome is increased and/or as the wavelength of the RF signal is reduced. As higher frequency RF signals have shorter wavelengths, massive MIMO arrays tend to be more negatively impacted by the radome of the base station antenna as these arrays tend to operate in higher frequency bands. 
     Pursuant to embodiments of the present invention, base station antennas  100  are provided that have a radome  119  ( FIGS.  2 ,  3 ,  16   , for example) that reduces coupling between adjacent columns. The radome  119  may be provided as an internal radome that resides between the outer radome  111  and the radiating elements  121 . The radome  119  covers (resides in front of) at least some of the radiating elements  121  of the massive MIMO array  120  in order to improve performance of the base station antenna  100 . For example, the radome  119  can be configured to reduce near-field coupling between radiating elements  121  of adjacent columns  125  and/or to improve reflection such as to reduce scattering of the transmitted RF signals. In such cases, the internal radome  119  will be located inside the base station antenna housing  100   h  (passive base station antenna housing) under the outer radome  111  and hence wind loading will not represent a performance issue with respect to this internal radome  119 . 
     It is also contemplated that the radome  119  can be configured as the outer radome with an outer surface configured to accommodate the wind loading requirements and so as to not require a separate external radome. See, e.g.,  FIG.  10 A . For ease of discussion, the radome  119  will be primarily referred to herein as the “internal” radome. 
     With columns spaced one wavelength (k) apart, at higher frequencies such as 5 GHz, the spacing between columns  125  is much more narrow than at lower frequencies, e.g., 1.0 GHz and, without the internal radome  119 , coupling between columns  125  can be stronger at 5 GHz. 
     The internal radome  119  can be configured to reduce mutual coupling of respective radiating elements  121  and/or columns  125  of radiating elements  121  and/or provide a common near field environment for each radiating element  121  and/or each column  125  of radiating elements  121 . 
     The internal radome  119  and the outer/external radome  111  can both reside in a near-field environment. 
     The internal radome  119  can be configured to provide substantially the same near-field environment for at least a plurality of, and typically each, column  125  of the massive MIMO array  120 . 
     The internal radome  119  can be configured to provide substantially the same near-field environment across all columns  125  when at a spacing of about one (1) wavelength λ between columns  125  (measured center to center) at a frequency band of about 1.8 GHz, 2.5 GHz and/or 5 GHz. The term “substantially the same” with respect to the near-field environment refers to +/−10% variation across the columns  125  under the internal radome  119 . The near-field coupling can be similar at different operating frequency bands whereas the far field coupling/operation can be different. 
     The internal radome  119  can be configured to reflect all or most of a transmitted RF signal back to the originating column  125  of radiating elements  121 . 
     The internal radome  119  can be configured to reduce scattering and RF coupling to neighboring columns  125  of radiating elements  121  relative to the same base station antenna  100  without the internal radome  119 . 
     Embodiments of the present invention will now be discussed in greater detail with reference to the attached figures. 
       FIG.  2    illustrates a base station antenna  100  according to certain embodiments of the present invention. In particular,  FIG.  2    is a simplified section view of the base station antenna  100 . In the description that follows, the antenna  100  will be described using terms that assume that the antenna  100  is mounted for normal use on a tower or other structure with the longitudinal axis of the antenna  100  extending along a vertical axis (i.e., generally perpendicular to a plane defined by the horizon) and the front surface  100   f  of the antenna  100  mounted opposite the tower pointing toward the coverage area for the antenna  100 . The base station antenna  100  has a housing  100   h  with a front surface  100   f  and an opposing rear surface  100   r  with sides  102 ,  103  coupled between the front and rear surfaces defining an interior cavity  100   c . An external radome  111  defines and/or provides at least the front surface  100   f  of the housing  100   h . The massive MIMO antenna array  120  resides inside the housing  100   h  facing an internal radome  119  that resides between the radiating elements  121  and the external radome  111 . A reflector  115  can be positioned in the cavity  100   c  of the housing  100   h  behind the massive MIMO antenna array  120 . 
     Referring to  FIGS.  2   ,  FIGS.  17 A and  17 B , the base station antenna  100  is an elongated structure that extends along a longitudinal axis L. The base station antenna  100  may have a tubular shape with a generally rectangular cross-section. The antenna  100  includes the outer radome  111  at the front  100   f  of the housing  100   h , a bottom end cap  130   b  and a top end cap  130   t . In some embodiments, the radome  111  and the top end cap  130   t  may comprise a single integral unit, which may be helpful for waterproofing the antenna  100 . Other configurations may be used that do not require a top end cap and seal the housing from the top in other ways. The external radome  111  may serve as a segment of the housing  100   h  that protects internal components of the antenna  100  from precipitation, moisture ingress, wind and the like. Preferably, the radome  111  is relatively rigid and mechanically strong to protect the internal components of the antenna during shipping and installation. One or more mounting brackets  107  can be provided, typically on the rear side  100   r  of the antenna  100 , which may be used to mount the antenna  100  onto an antenna mount (not shown) on, for example, an antenna tower. The bottom end cap  130   b  includes a plurality of connectors  140  mounted therein. 
     The antenna  100  includes an antenna assembly  200  that includes the massive MIMO antenna array  120 . At least part of the antenna assembly  200  may be slidably inserted into the housing  100   h  from either the top or bottom before the top cap  130   t  or bottom cap  130   b  are attached to the radome  111 . 
     Referring to  FIG.  3   , the internal radome  119  can be provided with a patterned outer surface comprising contoured segments with a maximally outwardly projecting segment  119   p , that can be referred to as a “peak”, that resides between a pair of laterally spaced apart segments  119   v  that reside inward a distance relative to the peak  119   p , in one or more planes behind and on each side of the peak  119   p , that can be respectively referred to as a “valley”. The internal radome  119  can also have laterally spaced apart outer sides  195  that extend inwardly further than the valleys  119   v  and that may couple directly or indirectly to the reflector  115  ( FIG.  2   ). 
     In the embodiment shown in  FIG.  3   , the internal radome  119  comprises a plurality of peaks  119   p , each configured to reside over a column  125  of the massive MIMO antenna array  120 . Each peak  119   p  can be laterally aligned with and positioned medially over a radiating element  121  of a column  125  of the massive MIMO antenna array  120 . 
     As shown in  FIG.  4   , the peak  119   p  can be a continuous outwardly projecting and longitudinally extending segment  119   s  forming a longitudinally extending peak segment  119   p  that extends over a column  125  of the internal radome  119 , typically over an entire length L of the internal radome  119  or at least 50% of the length thereof. 
     The number of longitudinally extending segments  119   s  can equal the number of columns  125  of the radiating elements  121  of the massive MIMO array  120  ( FIG.  2   ). 
       FIG.  5 A  illustrates that the internal radome  119 ′ can have a curved shape that is arcuate over a laterally extending width W of the internal radome  119 ′ and over the columns  125  (labeled as C 1 -C 8 ) of the radiating elements  121  of the massive MIMO antenna array  120 . 
       FIG.  5 B  illustrates that the internal radome  119 ″ can be flat across the width W thereof and over the columns  125  (labeled as C 1 -C 8 ) of the radiating elements  121  of the massive MIMO antenna array  120 . 
       FIG.  5 C  illustrates the embodiment shown in  FIG.  4    with the radome  119  provided as a patterned outer surface comprising peaks  119   p  and valleys  119   v  arranged with one peak  119   p  and a pair of valleys  119   v  corresponding to one column  125  of the columns (labeled as C 1 -C 8 ) of the radiating elements  121  of the massive MIMO array  120 . 
     As shown by the line marking the centerline through a radiating element in column  4  (C 4 ) in  FIG.  5 C , a respective (outermost projection of) peak  119   p  can reside aligned with and in front of a centerline of the radiating element  121 . The valleys  119   v  can reside adjacent outer ends  121   e  of the arm  121   a . The valleys  119   v  can reside laterally spaced apart a short distance from a neighboring end  121   e , typically within a short distance. In some embodiments, this short distance is about 0.1 mm or greater. This short distance can vary based on the separation distance between columns  125 . A respective valley  119   v  can be configured to reside midway between neighboring columns  125  of the radiating elements. The short distance spacing can depend on the column spacing. Thus, the short distance spacing can be between 0.1 mm and 50% of the column spacing, in some embodiments. For example, the lower band has a much larger element spacing than higher band columns. For example, if the band is at about 1.9 GHz, the column spacing is typically about 75 mm. Then the short distance between the neighboring ends  121   e  may be over 10 mm, but can be within 50% of the column spacing. For embodiments comprising a mMIMO antenna, the short distance spacing can be in a range of 0.1 mm and within 25% of the column spacing. However, for a 4×4 MIMO antenna, the column spacing is typically much larger comparing the mMIMO antenna column spacing and the short distance spacing is greater than about 0.1 mm and less than 50% of the column spacing. 
     The valleys  119   v  can extend down toward the ends  121   e  of the radiating elements  121  and terminate at a position that is in front of, flush with or behind the ends  121   e  of the radiation elements  121  in a normal operational position (or above, flush with or beneath the ends  121   e  of the radiating elements  121  in the orientation of the radiating elements  121  and internal radome  119  shown in  FIG.  5 C ). 
     An inwardly extending centerline (C/L) intersecting the radome  119  (in a front to back direction) can reside between two laterally adjacent innermost columns  125  of radiating elements  121  and can be aligned with a valley  119   v  of the internal radome  119  as shown in  FIG.  5 C , in some embodiments. 
       FIGS.  6 A- 6 C  are magnetic field graphs of respective radomes with massive MIMO antenna arrays  120  corresponding to the internal radomes  119 ,  119 ′,  119 ″ shown in corresponding  FIGS.  5 A- 5 C , as generated by a computational model. As shown in  FIG.  6 C , the radome  119  with the patterned shape of  FIG.  5 C  has the lowest magnetic field and fewer “hot spots” relative to the curved radome ( FIG.  6 A / FIG.  5 A ) which has perimeter hot spots and the flat radome  119 ″( FIG.  6 B ) which as an interior row of hot spots. 
       FIG.  7 A  is a graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and curved radome  119 ′ shown in  FIG.  5 A , as generated by a computational model. The four curves in  FIG.  7 A  represent the isolation between two adjacent columns in each direction for each polarization. As shown, the isolation exceeds 16 dB across the entire 3.3-4.0 GHz operating frequency range.  FIG.  7 B  is a similar graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and flat radome  119 ″ shown in  FIG.  5 B , as generated by a computational model. As shown in  FIG.  7 B , the isolation exceeds 17.5 dB across the entire 3.3-4.0 GHz operating frequency range. The isolation is between the two polarizations in column, the BASTA name for this isolation is intra-band isolation. The four curves in the graphs/charts are the column  1  to column  4  intra-band isolation: the weaker coupling from the adjacent column, the higher polarization purity in column, and also the higher intra-band isolation. 
       FIG.  7 C  is a graph of the isolation between adjacent columns (frequency (GHz) versus isolation decibel) for the massive MIMO antenna array and pattern shaped radome  119  shown in  FIG.  5 C , illustrating an ISO: 19.5 dB, as generated by a computational model. This shape provides the highest isolation of about 17.5 dB. 
       FIG.  8 A  is a graph of the azimuth pattern for an antenna beam that is not electronically scanned from boresight for the massive MIMO antenna array and flat radome  119 ″ shown in  FIG.  5 B , as generated by a computational model.  FIG.  8 B  is a graph of the azimuth pattern for an antenna beam that is electronically scanned from boresight to a maximum scan (here 53°) for the massive MIMO antenna array and radome  119 ″ shown in  FIG.  5 B , as generated by a computational model. 
       FIG.  9 A  is a graph of the azimuth pattern for an antenna beam that is not electronically scanned from boresight for the massive MIMO antenna array and pattern shaped radome  119  shown in  FIG.  5 C , as generated by a computational model.  FIG.  9 B  is a graph of the azimuth pattern for an antenna beam that is electronically scanned from boresight to a maximum scan (53°) for the massive MIMO antenna array and the pattern shaped radome  119  shown in  FIG.  5 C , as generated by a computational model. The graphs of  FIGS.  9 A- 9 B  illustrate the radiated RF energy as a function of azimuth angle from the boresight pointing direction for both the excited polarization and the non-excited polarization. As can be seen by comparing  FIGS.  8 B and  9 B , the radome  119  exhibits better cross-polarization discrimination performance and has lower side lobe levels at the maximum scan angle as compared to the radome  119 ″, as shown by the arrows in  FIG.  9 B . 
       FIG.  10 A  is a section view of another embodiment of a pattern shaped radome  119  according to embodiments of the present invention. The radome  119  comprises a plurality of peaks  119   p  and valleys  119   v  as discussed above with respect to  FIGS.  3 ,  4  and  5 C . In the embodiment shown in  FIGS.  3 ,  4  and  5 C , the outer wall is shaped to define the peaks  119   p  and valleys  119   v . In the embodiment shown in  FIG.  10 A , the outer surface can be flat  119   f  and the peaks  119   p  and valleys  119   v  can be formed in the interior part of the radome  119 , similar to a scalloped configuration. 
       FIG.  10 B  is a section view of another embodiment of a pattern shaped radome  119  according to embodiments of the present invention. In this embodiment, the outwardly projecting peaks  119   p  are defined by pointed tips rather than curved (arcuate) segments shown in  FIG.  5 C . 
       FIG.  10 C  is a section view of another embodiment of a pattern shaped radome  119  according to embodiments of the present invention. In this embodiment, the peaks  119   p  can have a frustoconical or flat segment  119   s  across a front (forwardmost) edge and have curvilinear or linear segments  119   c  connecting the valleys  119   v  to a corresponding peak  119   p.    
       FIG.  10 D  is a section view of another embodiment of a pattern shaped radome  119  according to embodiments of the present invention. In this embodiment, the peaks  119   p  can be flat segments  119   g  with stepped-down segments connecting valleys  119   v , and the valleys  119   v  can be flat valley segments rather than a pointed or curved valley. 
       FIG.  10 E  is a front perspective view of another embodiment of a pattern shaped radome  119 ″″ according to embodiments of the present invention. In this embodiment, the radome  119 ″ can have a peak segment  119   p  that resides between a pair of neighboring columns  125   1 ,  125   2  of radiating elements  121  with the valleys  119   v  separating the next laterally spaced apart neighboring shaped segment of the radome  119 ″″. 
       FIG.  10 F  is a section view of another embodiment of another pattern shaped radome  119 ″ ″ according to embodiments of the present invention. In this embodiment, the radome  119 ″ ″ can have a pattern with at least one peak segment  119   p  covering a plurality of adjacent columns  125   1 - 125   n . As shown, one peak  119  spans across/covers two columns, C 1 -C 2 , of radiating elements and other peak segments  119   p  spans across/covers a single column  125   1 , while yet another peak segment  119   p  spans across/covers three columns, C 6 -C 8 . The plurality of peak segments  119   p  covering a single column  125  can reside between the larger lateral span peak segments  119   p  (peak segments of larger width) that span across a plurality of columns  125   1 - 125   n . In some embodiments, the number “n” can be a number between 2 and 16, for example. Any combination or single configuration of the above example configuration of peak segments  119   p  can be used according to some embodiments. In addition, the height of the peaks  119   p  for a respective radome  119  can be the same over respective lengths and a width of the inner radome  119  or can vary laterally and/or longitudinally. For example, the peaks  119   p  that are closer to the side walls  195  may have a greater height than the medial peaks or the reverse may be true. By way of another example, alternating rows of peaks  119   p  may vary in height. The depth of the valleys  119   v  can be the same or vary as well. 
       FIG.  10 G  is a schematic top perspective view of an example pocket shaped segment  119   d  of a pattern shaped radome  119 . The pocket shaped segment can be configured as a dome  119   d  that can be configured to cover a plurality of or a single radiating element  121  in a column  125  of a multi-column antenna array  120  according to embodiments of the present invention. The pocket shaped segment  119   d  can have any sectional profile such as those described above and is not required to be an arcuate dome, e.g., the pocket shaped segment  119   d  can comprise a frustoconical shape. The dome  119   d  can be repeated across and along the radome  119  to be aligned with radiating elements  121  in the columns and across the rows of the array  120 . 
       FIG.  11    is an enlarged section view of the shaped radome shown in  FIG.  5 C  illustrating an example spacing (H) between a radiating (antenna) element  121  and a maximum outer projection (e.g., peak)  119   p  of the pattern shaped radome  119  according to embodiments of the present invention. This spacing H can vary. In some embodiments, the spacing H may be about one wavelength or less than one wavelength such as about ⅛) ¼ λ, ½λ or ¾λ. Note that references herein to “wavelength” refer to the wavelength corresponding to the center frequency of the operating frequency band of the radiating element/array. 
     In some particular embodiments, for a 3.5 GHz radiating element  121 , the H spacing can be about 9 mm. However, this distance H will vary with the operating frequency, different kinds/configurations of a radiating element  121  and different outer radomes  111  and positions thereof. 
     It is contemplated that the outer radome  111  and its spacing with respect to the inner radome  119  will affect the H spacing. Thus, the different height of the outer radome  111  can impact an optimum spacing H. For outer radomes  111  that are spaced apart greater than H wavelength from the inner radome  119 , the H spacing may be larger relative to those embodiments that position the outer radome  111  closer than H wavelength to the inner radome  119 . 
     The different shape of the radome  119  and/or the radome  111  can also affect the spacing H. For example, if the outer radome  111  has the very irregular curve, it may be difficult to find a good H spacing. 
     The dielectric constant (DK) of the outer radome  111  can also cause a different H spacing. 
     If the outer radome  111  is very far in front of the radiating element  121  (one wavelength or greater than one wavelength, for example), the spacing H (i.e., the distance between the radiating element  121  and the peak of the inner radome  119 ) may be positioned to be close to the arm (less than H wavelength) of the radiating element  121 , because the outer radome  111  has a lower impact on the radiating element  121 , so the H spacing is mostly related to the radiating element  121  itself. 
     In some embodiments, the distance between the outer radome  111  and a respective arm of a radiating element  121  can be larger than one-half wavelength and this spacing can have a lesser impact on the near field of the radiating element  121 . If the outer radome  111  is positioned at greater than H wavelength from the arm of the radiating element  121  (e.g., greater than ½ wavelength and less than 3 wavelengths), the distance between the internal radome  119  to the radiating element  121  can be less than a half wavelength, such as % wavelength or ⅛ wavelength, in some embodiments. 
     The valleys  119   v  can reside at a common inward location across all rows or vary in an inwardly projecting depth. The peak segment  119   p  can extend a distance “h” outward from the valleys  119   v  in a range of about 5 mm-2 inches. The spacing between the peaks and valleys can depend on the element arm and the feeding point on the feed stalk. But normally, the distance of the peaks to the arm is over 5 mm, so the minimum spacing between the peaks and the valleys can also be over 5 mm. 
     The peaks  119   p  can reside over an open interior space  1191  and this space can be an arcuate cavity (arcuate in the lateral dimension), in some embodiments. 
       FIG.  12    shows example positions of the internal radome  119  that are labelled H 1 , H 2 , H 3  that correspond to distances d 1 , d 2 , d 3 , respectively, for the internal radome  119  relative to the outer radome  111 , and to distances D 1 , D 2 , D 3  of the internal radome  119  from an outermost surface of the arm of the radiating element  121  according to embodiments of the present invention. When the internal radome  119  is closest to the radiating element D 1  it is further away from the outer radome  111  as shown. 
     If the outer radome  111  is very close to the radiating element  121 , such as, less than one half wavelength, it may be difficult to identify an optimum phase center above the radiating element  121 . In this case, the internal radome  119  can be at H 1  with a distance d 1  to be as far away as possible from the outer radome  111 , and the internal radome  119  can be at a distance D 1  that is very close to the radiating element  121 . 
     If the outer radome  111  is positioned at a range of one half of a wavelength to one wavelength from the radiating element  121 , the outer radome  111  may not overly impact the radiating element  121 , but still may cause a phase center to get higher, so the internal radome  119  can be positioned at H 2  to be a little higher above the radiating element at D 2  and with d 2  being related to the dielectric constant DK and the shape of the outer radome  111 . 
     If the distance between the outer radome  111  and the radiating element  121  is larger than a wavelength (e.g., position H 3 ), the impact is much weaker. So the phase center is most related to the radiating element  121 , normally the inner radome  119  should be close to the element radiating arm. 
       FIGS.  13 - 15    are graphs of the distribution of the phase centers of the radiating elements in a row of the massive MIMO array  120  when the internal radome  119  is at the positions H 1 , H 2 , H 3 , respectively of  FIG.  12   . The phase distribution data in  FIGS.  13 - 15    was generated by a computational model. The three separate curves in each graph represent three different frequencies, namely the blue curve (LE) is the lowest frequency in the operating frequency band; the red curve (MB) is the center frequency of the operating frequency band; and the green curve (HE) is the highest frequency in the operating frequency band. The marks m 1 -m 8  show the simulated phase value of the radiating element for each radiating element  121  in the row of the array  120  from left to right across the array  120 . As can be seen by comparing the three graphs, the most stable or best phase center distribution is provided when the inner radome is at position H 2 . The H 2  position is the best height for the radome  119 , as the phase center is stable across the entire array for the full operating frequency band (flat graph of phase across distance). 
       FIG.  16    is a partially exploded side perspective view of an example active antenna module  110  comprising the pattern shaped internal radome  119  according to embodiments of the present invention. The term “active antenna module” refers to an integrated cellular communications unit comprising a remote radio unit (RRU) and associated antenna elements that is capable of electronically adjusting the amplitude and/or phase of the subcomponents of an RF signal that are output to different antenna elements or groups thereof. The active antenna module  110  comprises the RRU and antenna but may include other components such as a filter, a, calibration network, a controller and the like. The active antenna module  110  can have an outer perimeter  112  with an inner facing seal interface  1121 . The active antenna module  110  can also include connectors  113 . 
     As shown in  FIG.  16   , the active antenna module  110  can comprise an RRU (remote radio unit) unit  1120  with heat sink  215  and fins  215   f , an integrated filter and calibration printed circuit board assembly  1180 , and massive MIMO array  120 . The RRU unit  1120  is a radio unit that typically includes radio circuitry that converts base station digital transmission to analog RF signals and vice versa. The RRU unit  1120  can couple to the integrated filter and calibration board assembly  1180  via connectors. 
     The antenna module  110  may optionally further include an outer radome  1111 . The outer radome  1111  covers the first (inner) radome  119 . 
       FIGS.  17 A and  17 B  are back perspective views of an example base station antenna  100  comprising the pattern shaped internal radome  119  according to embodiments of the present invention. 
     The active antenna module  110  can be sealably coupled to the housing  100   h  and, when installed, can form part of the rear  100   r  of the antenna  100 . The active antenna module  110  can have an inner facing surface that has a seal interface  1121  that is be sealably and releasably coupled to the rear  100   r  of the housing  100   h  to provide a water-resistant or water-tight coupling therebetween. The active antenna module  110  can be mounted to a recessed segment  108  of the antenna housing  100   h  surrounding a cavity  155  configured to receive and position the active antenna module  110  so that a rear face  110   r  is externally accessible and exposed to environmental conditions. The antenna housing  100   h  can include a passive antenna assembly comprising radiating elements. 
     The base station antenna  100  can also include planar seal interface  160  and a seal cap  165  positioned at the rear of the housing  100   h  between the upper segment with the active antenna module  110  and a lower segment. The sidewalls of the housing  100   h  can project rearward a greater distance D 2  at the lower segment than at the upper portion, having a shorter outward extent of distance (D 1 ) for a length corresponding to the active antenna module  110 . For further discussion of example active antenna modules  110  for base station antennas  100 , see, co-pending, co-assigned U.S. Provisional Application Ser. No. 63/075,344, filed Sep. 8, 2020, the contents of which are hereby incorporated by reference as if recited in full herein. 
     Referring to  FIGS.  16 ,  17 A and  17 B , the base station antenna  100  can include an antenna assembly  200  that includes the radiating elements  121  and a backplane  210  that has sidewalls  212  and a planar front surface  214  that acts as a reflector  115  to reflect rearwardly emitted RF radiation in the forward direction. Herein, the front surface of backplane  210  is referred to as the first reflector  115 . Various mechanical and electronic components of the antenna (not shown) may be mounted in the chamber defined between the sidewalls  212  and the back side of the reflector surface such as, for example, phase shifters, remote electronic tilt units, mechanical linkages, a controller, diplexers, and the like. The first reflector  115  may comprise or include a metallic surface that serves as a reflector and ground plane for the radiating elements  121  of the antenna  100 . 
     The radiating elements  121  can be provided as a plurality of dual-polarized radiating elements that are mounted to extend forwardly from the first reflector  115 . The radiating elements  121  can include low-band radiating elements, mid-band radiating elements and high-band radiating elements. The low-band radiating elements can be mounted in two columns to form two linear arrays of low-band radiating elements. The low-band radiating elements may be configured to transmit and receive signals in a first frequency band such as, for example, the 694-960 MHz frequency range or a portion thereof. The mid-band radiating elements may likewise be mounted in two columns to form two linear arrays of mid-band radiating elements. The mid-band radiating elements may be configured to transmit and receive signals in a second frequency band such as, for example, the 1427-2690 MHz frequency range or a portion thereof. The high-band radiating elements can be mounted in four columns to form four linear arrays f high-band radiating elements. The high-band radiating elements may be configured to transmit and receive signals in a third frequency band such as, for example, the 3300-4200 MHz frequency range or a portion thereof. 
     The low-band, mid-band and high-band radiating elements  121  may each be mounted to extend forwardly from the first reflector  115 . The first reflector  115  may comprise a sheet of metal that, as noted above, serves as a reflector and as a ground plane for the radiating elements  121 . Each radiating element  121  can be implemented as a cross-polarized dipole radiating element having feed stalks  121   s  that can be formed using a pair of printed circuit boards that are configured in an “X” shape and a pair of dipole radiator arms  121   a  that are mounted forwardly from the backplane by the feed stalks  121   s.    
     Since the high-band radiating elements operate in a much higher frequency band, the feed stalks  121   s  on the high-band radiating elements may be much shorter than the feed stalks  121   s  on the low-band radiating elements, and hence the dipole radiators on the high-band radiating elements may be positioned relatively further back from a front surface  100   f  of the housing and/or the outer radome  111 . 
     As discussed above, a radome  111  may start to reflect RF signals emitted by a radiating element that is mounted behind the radome as the ratio of the thickness of the radome to the wavelength of the RF signal increases. Various other factors, including the dielectric constant of the radome material and the distance separating the radiating element from the radome also impact the degree of reflection. 
       FIG.  18    is a flow chart of example actions that can be carried out to reduce (near-field) cross-column coupling and/or reflection (scattering) according to embodiments of the present invention. A base station antenna with a massive MIMO antenna array comprising columns of radiating antenna elements and an internal radome resides over the columns of radiating elements and under an outer radome of the base station antenna is provided (block  800 ). 
     An RF signal is transmitted toward and out of the internal and outer radomes while inhibiting reflection (scattering) and/or coupling of a transmitted signal between adjacent columns of radiating elements (block  810 ). 
     The internal radome is spaced a first distance from an outermost surface of a radiating element and a second distance from the outer radome (block  820 ). 
     The first distance can be in a range of % wavelength to H wavelength and the second distance can be greater than the first distance and/or in a range of about H wavelength or greater such as about one wavelength or greater (block  825 ). 
     The internal radome has a series of shaped columns, with each shaped column having an outermost (peak segment) dimension laterally centered over a center of a radiating element and/or a longitudinally extending centerline of a column of radiating elements (block  830 ). 
     The base station antenna can be configured for 5G operation (block  840 ). 
     The internal radome directs reflected signal to be off-boresight (block  850 ). The signal can be directed to be at 30-60 degrees off centerline of the boresight. 
     Reducing near-field coupling between radiating elements in different columns relative to a base station antenna of the same configuration without an internal radome (block  860 ). 
     Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). 
     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. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof. 
     Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.