Patent Publication Number: US-10312583-B2

Title: Antenna systems with low passive intermodulation (PIM)

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/US2014/050301 filed Aug. 8, 2014 (published as WO 2015/041768 on Mar. 26, 2015) which, in turn, claims the benefit of and priority to Malaysian Application No. PI2013701673 filed Sep. 17, 2013. The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to antenna systems with low or good PIM (passive intermodulation), and which may also have improved and/or good isolation and bandwidth. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Examples of infrastructure antenna systems include customer premises equipment (CPE), satellite navigation systems, alarm systems, terminal stations, central stations, and in-building antenna systems. With fast growing technologies, antenna bandwidth has become a great challenge along with the requirement to miniaturize CPE device size or antenna system size in order to maintain a low profile. In addition, multi-antenna systems having more than one antenna have been used to increase capacity, coverage, and cell throughput. 
     Also with fast growing technologies, many devices have gone to multiple antennas in order to satisfy the end customers&#39; demand. For example, multiple antennas are used in multiple input multiple output (MIMO) applications in order to increase user capacity, coverage, and cell throughput. With the current market trend towards economical, small, and compact devices, it is not uncommon to use multiple antennas identical in form that are placed in very close proximity to each other due to size and space limitations. Moreover, antennas for customer premises equipment, terminal stations, central stations, or in-building antenna systems, must usually be low profile, light in weight, and compact in physical volume, which makes Planar Inverted F-Antennas (PIFAs) particularly attractive for these types of applications. 
       FIG. 1  illustrates a conventional Planar Inverted F-Antenna (PIFA)  10 . As shown in  FIG. 1 , this basic design consists of a radiating patch element  12 , a ground plane  14 , a shorting element  16 , and a feeding element  18 . The width and length of the radiating patch element  12  determines the desired resonant frequency. The summation of the width and length of the radiating patch element  12  is about one quarter wavelength (λ/4). The radiating patch element  12  may be supported by a dielectric substrate above the ground plane  14 . 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to various aspects, exemplary embodiments are disclosed of antenna systems. In an exemplary embodiment, an antenna system generally includes a ground plane and first and second antennas. A first isolator is disposed between the first and second antennas. A second isolator extends outwardly from the ground plane. The antenna system is configured to be operable with low passive intermodulation. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  illustrates a conventional Planar Inverted-F Antenna (antenna); 
         FIG. 2  is a exploded perspective view of a multi-band antenna system configured to have low PIM (passive intermodulation) according to an exemplary embodiment; 
         FIG. 3  is another exploded perspective view of the antenna system shown in  FIG. 2 , where the ground plane (and vertical wall isolator and antenna coupled thereof) are mounted to a base; 
         FIG. 4  is a plan view of the antenna system shown in  FIGS. 2 and 3  after the various antenna components have been assembled on and/or mounted to the base; 
         FIG. 5  is a perspective view of the antenna system shown in  FIG. 4 , and also illustrating an exemplary coaxial cable connected to an antenna; 
         FIG. 6  is a partial perspective view of the coaxial cable and antenna shown in  FIG. 5 , and illustrating the exemplary way that a cable holder may be directly formed from the ground plane; 
         FIG. 7  is another partial perspective view of the coaxial cable and antenna shown in  FIGS. 5 and 6 , and illustrating the exemplary way that the center conductor of the coaxial cable may be connected to the antenna; 
         FIG. 8  illustrates a conventional way for soldering a coaxial cable braid to a ground plane; 
         FIG. 9  illustrates an exemplary way for soldering a coaxial cable braid to a cable holder integrally formed from a ground plane according to exemplary embodiments; 
         FIGS. 10A and 10B  are respective perspective views of an exemplary NF bulkhead connector and exemplary insulator that may be used with the antenna system shown in  FIGS. 2 through 5  where the insulator helps to minimize (or at least reduce) contact area to the ground plane and subsequently minimize (or at least reduce) PIM issues according to exemplary embodiments; 
         FIG. 11  is a cross-sectional view showing the exemplary way that the NF bulkhead connector and insulator shown in  FIG. 10  may be connected to the ground plane and antenna of the antenna system shown in  FIGS. 2 through 5 ; 
         FIGS. 12A, 12B, and 12C  are respective side and end views of the NF bulkhead connector shown in  FIG. 11 , where exemplary dimensions (in millimeters, after plating) are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 13  is a partial perspective view showing the exemplary way that the center conductor and four outer conductors/contacts of the NF bulkhead connector may be respectively connected to the ground plane and antenna of the antenna system shown in  FIGS. 2 through 5 ; 
         FIG. 14  is a perspective view of an exemplary antenna that may be used with an antenna system according to exemplary embodiments, where the antenna includes a removed portion for connector soldering purposes, an added tab for center conductor soldering purposes, and a tab that is small and/or reduced in size to minimize (or at least reduce) PIM issues and inconsistent soldering; 
         FIGS. 15A, 15B, and 15C  are respectively inner, outer, and partial perspective views of a base that may be used with the antenna system of  FIGS. 2 through 5  according to exemplary embodiments; 
         FIG. 16A  is a perspective view of a ground plane and parasitic elements that may be used in the antenna system shown in  FIGS. 2 through 5  according to an exemplary embodiment, where the ground plane includes holes for the contacts of the NF connector shown in  FIG. 10  and openings for a PCB holder directly formed (e.g., molded, etc.) in the base plate, and where the dimension and shape of the gap between the parasitic elements and the ground plane may be used for adjusting the resonance for high and low band; 
         FIG. 16B  is a perspective view of a portion of the ground plane that may be used in the antenna system shown in  FIGS. 2 through 5  according to another exemplary embodiment, where the ground plane includes holes for the contacts of the NF connector shown in  FIG. 10  and a PCB holder directly or integrally formed (e.g., stamped and bent tabs, etc.) from the ground plane; 
         FIG. 17A  is a perspective view of the ground plane and parasitic elements shown in  FIG. 16A  mounted to a base, and also illustrating the exemplary way that a printed circuit board (PCB) or vertical wall isolator may be held by a PCB holder of the base that passes through openings in the ground plane shown in  FIG. 16A ; 
         FIG. 17B  illustrates the exemplary way that a printed circuit board (PCB) or vertical wall isolator may be held by the PCB holder of the ground plane shown in  FIG. 16B ; 
         FIGS. 18A, 18B, and 18C  are respective top, side, and bottom plan views of the antenna system shown in  FIGS. 2 through 5  after being positioned within an interior enclosure cooperatively defined by a base and radome, and also illustrating an exemplary pigtail type connector configuration according to exemplary embodiments; 
         FIGS. 19A and 19B  are respective bottom and top perspective views of the antenna system shown in  FIGS. 2 through 5  after being positioned within an interior enclosure cooperatively defined by a base and radome, and also illustrating an exemplary fixed N-female (NF) bulkhead connector configuration according to exemplary embodiments; 
         FIG. 20  includes exemplary line graphs of Voltage Standing Wave Ratio (VSWR) (S 11 , S 22 ) and isolation (S 21  in decibels) versus frequency measured for a prototype of the example antenna system shown in  FIGS. 2 through 5  within the radome and with the pigtail connection as shown in  FIG. 18B ; 
         FIG. 21  shows the pattern orientation and planes relative to the antenna prototype with the pigtail connection during radiation pattern testing; 
         FIGS. 22 through 29  illustrate radiation patterns (azimuth plane, Phi 0° plane, and Phi 90° plane) measured for the first and second multi-band antennas (shown in broken lines and solid lines) of the prototype of the example antenna system shown in  FIGS. 2 through 5  with the pigtail connection and pattern orientation shown in  FIG. 21  at frequencies of about 698 megahertz (MHz), 824 MHz, 894 MHz, 960 MHz, 1785 MHz, 1910 MHz, 2110 MHz, and 2700 MHz, respectively; 
         FIGS. 30 and 31  are exemplary line graphs of PIM (in decibels relative to carrier (dBc)) versus frequency (in MHz)) measured for ports  1  and  2  of the prototype of the example antenna system shown in  FIGS. 2 through 5  with the pigtail connection shown in  FIG. 18B , where the line graphs show the low PIM performance (e.g., less than −150 dBc, etc.) at both a low band ( FIG. 30 ) and a high band ( FIG. 31 ); 
         FIG. 32  includes exemplary line graphs of Voltage Standing Wave Ratio (VSWR) (S 11 , S 22 ) and isolation (S 21  in decibels) versus frequency measured for a prototype of the example antenna system shown in  FIGS. 2 through 5  within the radome and with the fixed NF bulkhead connector shown in  FIG. 19A ; 
         FIGS. 33 through 40  illustrate radiation patterns (azimuth plane, Phi 0° plane, and Phi 90° plane) measured for the first and second multi-band antennas (shown in solid lines and broken lines) of the prototype of the example antenna system shown in  FIGS. 2 through 5  with the fixed NF bulkhead connection shown in  FIG. 19A  (and same pattern orientation as in  FIG. 21 ) at frequencies of about 698 MHz, 824 MHz, 894 MHz, 960 MHz, 1785 MHz, 1910 MHz, 2110 MHz, and 2700 MHz, respectively; and 
         FIGS. 41 and 42  are exemplary line graphs of PIM (in dBc) versus frequency (in MHz) measured for ports  1  and  2  of the prototype of the example antenna system shown in  FIGS. 2 through 5  with the fixed NF bulkhead connector shown in  FIG. 19A , where the line graphs show the low PIM performance (e.g., less than −150 dBc, less than −153 dBc, etc.) at both a low band ( FIG. 41 ) and a high band ( FIG. 42 ). 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     The inventors hereof have recognized a need for relatively low profile antenna systems that have low PIM (Passive Intermodulation) (e.g., able to qualify as a low PIM rated design, etc.), good or improved bandwidth (e.g., meet the LTE/4G application bandwidth from 698-960 MHz and from 1710-2700 MHz, etc.), good or improved isolation (e.g., at low band, etc.), and/or provide more VSWR margin at production. Accordingly, disclosed herein are exemplary embodiments of antenna systems (e.g.,  100  ( FIGS. 2-5 ),  200  ( FIGS. 18A, 18B, 18C ),  300  ( FIGS. 19A and 19B ), etc.) that have a low PIM rated design or configuration. 
     In exemplary embodiments, a low PIM design may be realized by reducing galvanic metal-to-metal contact surface and minimizing (or at least reducing) soldering area, along with good or improved bandwidth and isolation by introducing parasitic elements and a unique isolator configuration. The low PIM design also has the design flexibility and capability to accommodate both a pigtail connector type (e.g.,  FIGS. 18B and 21 , etc.) and a fixed connector type (e.g.,  FIGS. 10A and 19A , etc.) with good or improved performance consistency. The disclosed exemplary embodiments have superior or increased bandwidth, improved isolation without compromising overall bandwidth, and improved or low PIM. 
     According to aspects of the present disclosure, exemplary embodiments may include one or more (or all) of the following features to realize or achieve low PIM. In an exemplary embodiment, the antenna system preferably does not include any ferromagnetic material or ferromagnetic components including right plating that could otherwise be a source of PIM. Instead, the radiating elements and ground plane (e.g., antennas  110  and ground plane  112  in  FIGS. 2 and 3 , etc.) may instead be made of brass or other suitable non-ferromagnetic material. The connectors and cable are preferably PIM rated components. 
     The radiating element grounding may be based on proximity couple grounding by introducing dielectric adhesive tape (broadly, dielectric member) below the radiating elements to avoid direct galvanic contact between the radiating elements and the ground plane. See, for example,  FIG. 3  in which dielectric adhesive tape  113  is aligned for positioning between the antenna  110  and ground plane  112 . 
     There may be relatively small areas for soldering the contacts of the connector to the ground plane. Accordingly, the connector may be connected or grounded to the ground plane with a relatively small area soldering contact. See, for example,  FIG. 13  in which there are four relatively small soldering areas for soldering the contacts  122  of the connector  114  ( FIG. 10A ) to the ground plane  112  ( FIG. 13 ). 
     A dielectric member may be positioned between an upper surface of the connector and the ground plane to electrically insulate and minimize (or at least reduce) direct galvanic contact between the connector&#39;s upper surface and the ground plane. See, for example,  FIG. 2  in which a circular dielectric or insulator  116  (e.g., FR-4 fiberglass reinforced epoxy laminate material, etc.) is aligned for positioning between the upper surface of the connector  114  and the ground plane  112 . 
     Further, the ground plane may include an integrally formed (e.g., stamped, etc.) feature for soldering a cable braid. This feature provides minimum (or at least reduced) direct galvanic contact surface between the cable braid and the ground plane as only the cross section of the integrally formed feature contacts the ground plane. Advantageously, this helps to prevent (or at least reduce) any inconsistency in the contact between the cable braid and the ground plane. See, for example,  FIGS. 6, 7, and 9  in which a cable holder  124  has been directly formed (e.g., stamped, etc.) from the ground plane  112 .  FIG. 9  shows a cable braid  126  soldered to the stamped cable holder  124 . By comparison,  FIG. 8  illustrates a conventional way for soldering a coaxial cable braid to a ground plane, which may introduce inconsistent contact especially along the bottom of the cable braid where solder is not present. In  FIG. 9 , there is no contact along the bottom of the cable braid  126 , which is hollow or open due to the stamping and repositioning of ground plane material to make the cable holder  124 . 
     The ground plane and/or base may also include one or more integrally formed (e.g., stamped, etc.) features for holding a PCB or vertical wall isolator to reduce solder areas, e.g., by eliminating the need for solder pads on the ground plane that would otherwise be used for attaching the PCB to the ground plane. The reduced solder areas reduce PIM and inconsistency that may arise with soldering. See, for example,  FIGS. 2, 16A, and 17A  in which a PCB holder  128  is directly molded from and protrudes outwardly from the base  133  (e.g., plastic base plate, etc.). Pieces or portions of the PCB holder  128  pass through openings  123  ( FIG. 16A ) in the ground plane  112 . As shown in  FIG. 17A , the pieces of the PCB holder  128  may retain or hold a PCB or vertical wall isolator  130  such that only a single or two solder pads  129  is needed for electrically connecting the PCB or isolator  130  to the ground plane  112 . Alternatively,  FIGS. 16B and 17B  illustrate an example in which the ground plane  112  includes a PCB holder directly formed (e.g., stamped and bent tabs  128 , etc.) from the ground plane  112 . The PCB holder of the ground plane  112  may retain or hold a PCB or vertical wall isolator  130  such that only a single solder pad  129  is needed for electrically connecting the PCB or isolator  130  to the ground plane  112 . 
     According to other aspects of the present disclosure, exemplary embodiments may include one or more features to realize or achieve good or improved bandwidth. In an exemplary embodiment, parasitic elements are added or introduced adjacent or beside the radiating elements to enhance bandwidth for both low and high band while maintaining good isolation between radiators. See, for example,  FIGS. 4 and 5  in which first and second parasitic elements  132  are positioned adjacent or beside the first and second antennas  110 , respectively, without making direct galvanic contact therewith. 
     According to further aspects of the present disclosure, exemplary embodiments may include one or more features to realize or achieve good or improved isolation. In an exemplary embodiment, an isolator is added between two radiating elements thereby improving isolation at low band by increasing the ground surface electrically. See, for example,  FIG. 5  in which a T-shaped isolator  134  extends outwardly from the ground plane  112  and increases the ground surface electrically. The improved isolation allows more antenna radiating elements to be positioned in the same volume of space or allows a smaller overall antenna assembly to be used for the same number of antenna radiating elements (e.g., for an end use where space is limited or compactness is desired, etc.). 
       FIGS. 2 through 5  illustrate an exemplary embodiment of an antenna system or assembly  100  embodying one or more aspects of the present disclosure. As disclosed herein, the antenna system  100  is configured so as to have low PIM as well as good bandwidth and isolation. 
     The antenna system  100  includes two antennas  110  spaced apart from each other on a ground plane  112 . In this example, the antennas  110  are identical to each other and symmetrically placed relatively close to each other on the ground plane  112 . In alternative embodiments, the antennas  110  may be asymmetrically placed, may be dissimilar or non-identical, and/or configured differently than the antenna  110 . By way of example, another exemplary embodiment may include one or more antennas (e.g., PIFAs, etc.) as disclosed in PCT International Patent Application WO 2012/112022, the entire contents of which is incorporated herein by reference. 
     As shown in  FIG. 3 , dielectric adhesive tape  113  (broadly, dielectric member) is used between the bottom surface of the antennas  110  and the ground plane  112 , to avoid direct galvanic contact between the antennas  110  and the ground plane  112 . Accordingly, the radiating element grounding in this example is based on proximity couple grounding. 
     The antennas  110  may be coupled to the base  133  via mechanical fasteners, etc. For example, the antennas  110  and tape  113  include openings therethrough for receiving mechanical fasteners. In addition, dielectric standoffs  136  may be positioned or slotted between the base  133  and the upper surface or radiating patch element  138  of the antennas  110 . The standoffs  136  are configured to physically or mechanically support the upper radiating patch elements  138  of the antennas  110  with sufficient structural integrity. Alternative embodiments may be configured differently, such as without the standoffs or with different means for supporting the radiating patch elements and/or for coupling the antennas to the base. 
     With continued reference to  FIGS. 2 through 5 , first and second parasitic elements  132  are positioned adjacent or beside the first and second antennas  110 , respectively, such that the parasitic elements  132  do not make direct galvanic contact with the antennas  110  or ground plane  112 . In this example, the first and second parasitic elements  132  are identical and symmetrically placed relative to each other when coupled (e.g., mechanically fastened, etc.) to the base  133  (e.g., base plate, etc.). The introduction of the parasitic elements  132  enhances the antenna&#39;s bandwidth for both low and high band while maintaining good isolation between the antennas  110 . Also, the dimension and shape of the gap  149  may be adjusted to provide minor tweaking of the resonance for high and low band ( FIG. 16A ). 
     The antenna system  100  includes first and second isolators  130  and  134 . The dimensions, shapes, and locations of the isolators  130 ,  134  relative to the antennas  110  and ground plane  112  may be determined (e.g., optimized, etc.) to improve the isolation and/or to enhance bandwidth. 
     As shown in  FIG. 5 , the second isolator  134  is generally T-shaped and extends outwardly from the ground plane  112  to thereby increase the ground surface electrically. The isolator  134  is generally between the antennas  110  such that isolation is improved at low band by increasing the ground surface electrically. In this example, the isolator  134  is an integral piece or part of the ground plane  112  that has been formed (e.g., stamped, etc.) to have a T-shape that is co-planar with the ground plane  112 . Alternative embodiments may include an isolator that is not T-shaped and/or that is a separate, non-integral piece electrically connected to the ground plane. 
     As shown in  FIGS. 5 and 17A -B, the first isolator  130  comprises a vertical wall isolator. The vertical wall isolator  130  may be configured such that its upper, free edge is the same height (e.g., 20 millimeters, etc.) above the ground plane  112  as the upper surfaces of the radiating patch elements  138  of the antennas  110 . Alternative embodiments may include an isolator between the antennas  110  that is configured differently (e.g., non-rectangular, non-perpendicular to the ground plane, taller or shorter, etc.) than what is illustrated. 
     The vertical wall isolator  130  is held in place by the integral features of the base  133  and/or ground plane  112 , which reduce solder areas, e.g., by eliminating the need for solder pads on the ground plane  112  that would otherwise be used for attaching the PCB to the ground plane  112 . The reduced solder areas reduce PIM and inconsistency that may arise with soldering. See, for example,  FIGS. 2, 16A, and 17A  in which a PCB holder  128  is directly molded from and protrudes outwardly from the base  133  (e.g., plastic base plate, etc.). Pieces or portions of the PCB holder  128  pass through openings  123  ( FIG. 16A ) in the ground plane  112 . As show in  FIG. 17A , the pieces of the PCB holder  128  may retain or hold a PCB or vertical wall isolator  130  such that only a single or two solder pads  129  is needed for electrically connecting the PCB or isolator  130  to the ground plane  112 . 
     Alternatively,  FIGS. 16B and 17B  illustrate another exemplary embodiment in in which the ground plane  112  includes a PCB holder directly formed (e.g., stamped and bent tabs  128 , etc.) from the ground plane  112 . The PCB holder of the ground plane  112  may retain or hold a PCB or vertical wall isolator  130  such that only a single solder pad  129  is needed for electrically connecting the PCB or isolator  130  to the ground plane  112 . As shown in  FIG. 16B , the ground plane  112  includes first and second stamped and bent tabs  128  that are generally opposite or opposing a third stamped and bent tab  128 . The tabs  128  are generally perpendicular to the ground plane  112 . The stamped and bent tabs  128  may retain or hold the vertical wall isolator  130  in place, such that only a single solder pad  129  ( FIG. 17B ) is needed for electrically connecting the isolator  130  to the ground plane  112 . For example, the vertical wall isolator  130  has first and second opposite sides. The vertical wall isolator  130  is positioned relative to the tabs  128  such that at least one tab is along the first side of the vertical wall isolator  130  and at least one oppositely facing tab is along the second side of the vertical wall isolator  130 , such that the tabs  128  cooperate to frictionally retain the vertical wall isolator  130  therebetween. This isolator mounting arrangement advantageously reduces solder areas, e.g., by eliminating the need for solder pads on the ground plane  112  that would otherwise be used for attaching the isolator  130  to the ground plane  112 . The reduced solder areas reduce PIM and inconsistencies that may arise from soldering. 
     The vertical wall isolator  130  is generally perpendicular and vertical relative to the ground plane  112 . In this particular illustrated embodiment, the antennas  110  are spaced equidistant from the vertical wall isolator  130 . The antennas  110  are symmetrically arranged on opposite sides of the vertical wall isolator  130  about an axis of symmetry through or defined by the vertical wall isolator  130 , such that each antenna  110  is essentially a mirror image of the other. 
     During operation, the vertical wall isolator  130  improves isolation. The frequency at which the isolator  130  is effective is determined primarily by the length of the horizontal section and height of the isolator  130 . The horizontal section is generally parallel to the ground plane  112  in this illustrated embodiment. 
     As shown in  FIGS. 2, 6, 7, and 9 , the ground plane  112  includes an integrally formed (e.g., stamped and bent tabs  124 , etc.) feature  124  for soldering a cable braid  126 . This feature provides minimum (or at least reduced) direct galvanic contact surface between the cable braid  126  and the ground plane  112  as only the cross section of the integrally formed feature contacts the ground plane  112 . Advantageously, this helps to prevent (or at least reduce) any inconsistency in the contact between the cable braid  126  and the ground plane  112 . In this exemplary embodiment, the ground plane  112  includes first and second pairs of stamped and bent tabs  124  that are at an acute angle (e.g., 30 degrees, etc.) relative to the ground plane  112 . By way of example, each tab  124  may be at about 30 degrees relative to the ground plane  112  such that each of the first and second pairs of tabs  124  defines an angle therebetween of about 60 degrees.  FIG. 9  shows the solder joints  125  and cable braid  126  soldered to the integral cable holder  124  of the ground plane  112 . In  FIG. 9 , there is no contact along the bottom  127  of the cable braid  126 , which is hollow or open due to the stamping and repositioning of ground plane material to make the cable holder  124 . By comparison,  FIG. 8  illustrates a conventional way for soldering a coaxial cable braid  126  to a ground plane, which may introduce inconsistent contact especially along the bottom  127  of the cable braid  126  where there is no solder between the cable braid  126  and ground plane. 
     With reference to  FIGS. 6, 7, 11, 13, and 14 , the center conductor  131  of a coaxial cable  137  may be connected (e.g., soldered, etc.) to the antenna  110  and the center conductor or contact  120  of the connector  114 . From underneath, the connector  114  may be positioned so that the connector&#39;s center contact  120  passes through a hole in a tab  140  of the antenna  110  ( FIGS. 11 and 13 ). From above, the center conductor  131  of the coaxial cable  137  may be placed on the tab  140  in physical galvanic contact with or close proximity to the connector&#39;s center conductor  120 , and then soldered together. 
     To allow access for soldering purposes, a portion  142  of the antenna  110  may be removed (e.g., cut, etc.) as shown in  FIGS. 13 and 14 . The antenna  110  also includes a tab  144  that is small and/or reduced in size to minimize (or at least reduce) PIM issues and inconsistency that may arise from soldering. 
     The antenna system  100  is also configured so as to have relatively small areas for soldering the outer contacts  122  of the connector  114  to the ground plane  112 . As shown in  FIG. 13 , there are four relatively small soldering areas for soldering the contacts  122  of the connector  114  ( FIG. 10A ) to the ground plane  112 . As shown in  FIG. 16 , the ground plane  112  includes openings  117  to allow the connector&#39;s center contact  120  and four outer contacts  122  to pass therethrough. The small soldering areas also help to provide a low PIM design. 
       FIGS. 10A through 12C  illustrate an exemplary embodiment of a connector  114  that may be used with the antenna system  100 . As shown, the connector  114  includes the center contact or pin  120  and four outer contacts or pins  122 . The connector  114  also includes a nut  146 , a lock washer  148 , and an O-ring  150 . 
     Advantageously, the connector  114  is designed so as to have a small soldering pin to reduce the soldering area, and thereby reduce PIM. The base material of the connector shell is a non-ferromagnetic material, such as Trimetal or albaloy. The pins or contacts are also made of non-ferromagnetic material, such as beryllium copper. By using non-ferromagnetic materials, the antenna system will have a better or lower PIM performance. 
     In one specific example, the connector body/shell plating is brass with an albaloy finish. The contacts  120 ,  122  are beryllium copper with gold finish. The O-ring  150  is silicon rubber. The lock washer  148  and nut  146  are brass with albaloy/copper finish. In this specific example, the connector  114  also has an impedance of 50 ohms, a frequency range of 0 to 6 GHz, a maximum VSWR of 1.2 over the frequency range, and an operating temperature of −55° C. to +125° C. The specific materials, dimensions, and technical data are provided only for purposes of illustration and not for purposes of limitation. Alternative embodiments may include connectors that are configured differently, e.g., made from difference materials, different sizes, different technical data, etc. 
     As shown in  FIG. 2 , a dielectric member or insulator  116  is positioned between an upper surface of the connector  114  and the ground plane  112  to electrically insulate and minimize (or at least reduce) direct galvanic contact between the connector&#39;s upper surface and the ground plane  112 . In this exemplary embodiment, the insulator  116  is circular and made of FR-4 fiberglass reinforced epoxy laminate material. As shown in  FIG. 10B , the insulator  116  includes openings  118  to allow the connector&#39;s center contact  120  and four outer contacts  122  to pass therethrough for electrical connection (e.g., soldering, etc.) to the antenna  110  and ground plane  112 , respectively. Alternative embodiments may include a differently configured insulator, e.g., non-circular and/or made of a different material, etc. 
     The configuration of the ground plane  112  may depend, at least in part, on the particular end use intended for the antenna system  100 . Thus, the particular shape, size, and material(s) (e.g., brass, other non-ferromagnetic material, etc.) of the ground plane  112  may be varied or tailored to meet different operational, functional and/or physical requirements. But in view of the relatively small lower surfaces of the antennas  110 , the ground plane  112  is configured to be sufficiently large enough to be a fully effective ground plane for the antenna system  100 . 
     In the illustrated embodiment of  FIG. 16 , the ground plane  112  has a trapezoidal portion and a rounded portion. The ground plane  112  may be sized or trimmed so as to fit onto a relatively small radome base (e.g., base  233  in  FIG. 18C , base  333  in  FIG. 19A , etc.) and so as to fit under a radome or housing (e.g., radome  235  in  FIG. 18A , radome  335  in  FIG. 19A , etc.). Alternative embodiments may include differently configured ground planes having other shapes, such as the shape shown in  FIG. 11 , non-trapezoidal shapes, non-rectangular shapes, entirely rectangular shapes, entirely trapezoidal shapes, etc. 
     With ground planes, the length may be increased or maximized to increase bandwidth. As noted above, however, the ground plane  112  may be sized small enough so that it may be confined within a relatively small radome assembly. For example, an exemplary embodiment may include the ground plane  112  being configured (e.g., shaped and sized) so as to be mounted on the circular radome base  233  (shown in  FIG. 18C ) having a diameter of about 219 millimeters or less. 
     A small ground plane may not have sufficient electrical length for some end use applications. As shown in  FIG. 4 , the ground plane  112  includes a T-shaped extension or isolator  134 . The isolator  134  serves the purpose of bandwidth enhancement by increasing the electrical length of the ground plane  112  and improving isolation. 
     With reference to  FIG. 14 , the driven radiating section of the antenna  110  includes a radiating patch element  138  (or more broadly, an upper radiating surface or planar radiator). The radiating patch element  138  includes a slot  139  for forming multiple frequencies (e.g., frequencies from 698 megahertz to 960 megahertz and from 1710 megahertz to 2700 megahertz, etc.) and for frequency tuning at the high band. The slot  139  may be configured such that the antenna  110  improves the return loss level at high frequencies or high frequency bands for a higher patch. For a lower profile patch option, a slot may not be needed to improve high band in other embodiments. In this illustrated example embodiment, the slot  139  is generally rectangular (except for the removed portion  142 ) and divides the radiating patch element  138  so as to configure the antenna  110  to be resonant or operable in at least a first frequency range and a second frequency range, which is different (e.g., non-overlapping, disjoint, higher, etc.) than the first frequency range. For example, the first frequency range may be from about 698 megahertz to about 960 megahertz, while the second frequency range may be from about 1710 megahertz to about 2700 megahertz. Or, for example, the antenna  110  may be operable across a single wide frequency range from about 698 MHz to about 2700 MHz. The slot  139  may be configured for different frequency ranges and/or have any other suitable shape, for example a line, a curve, a wavy line, a meandering line, multiple intersecting lines, and/or non-linear shapes, etc., without departing from the scope of this disclosure. The slot  139  is an absence of electrically-conductive material in the radiating patch element  138 . For example, the radiating patch element  138  may be initially formed with the slot  139 , or the slot  139  may be formed by removing electrically-conductive material from the radiating patch element  138 , such as etching, cutting, stamping, etc. In still yet other embodiments, the slot  139  may be formed by an electrically nonconductive or dielectric material, which is added to the upper radiating patch element  138  such as by printing, etc. 
     The radiating patch element  138  is spaced apart from and disposed above a lower surface  141  of the antenna  110 . By way of example only, the radiating patch element  138  may include a top surface that is about 20 millimeters above the bottom of the lower surface. This dimension and all other dimensions provided herein are for purposes of illustration only, as other embodiments may be sized differently. 
     In this example, the radiating patch element  138  and lower surface  141  are generally parallel to each other and are also planar or flat. Alternative embodiments may include different configurations, such as non-planar, non-flat, and/or non-parallel radiating elements and lower surfaces. 
     The antenna  110  includes a feeding element  143  ( FIGS. 2, 3, and 7 ). The tab  140  ( FIG. 7 ) along the bottom of the feeding element  143  provides or is operable as the feeding point. The center conductor  131  of the coaxial cable  137  and center contact  120  of the connector  114  may be electrically connected, e.g., soldered, to each other and to the tab  140  for feeding the antenna  110 . 
     In operation, the feeding points of the antennas  110  may receive signals to be radiated by the radiating patch elements  138  from the coaxial cables  137 , which signals may be received by the coaxial cables  137  from a transceiver, etc. Conversely, the coaxial cables  137  may receive signals from the feeding points of the antennas  110  that were received by the radiating patch elements  138 . Alternative embodiments may include other feeding arrangements or means for feeding the antennas  110  besides coaxial cables, such as transmission lines, etc. 
     With reference to  FIG. 3 , the feeding element  143  is electrically connected to and extends between the radiating patch element  138  and the lower surface  141 . The feeding element  143  is relatively wide as the feeding element  143  may be defined or considered as being the entire illustrated side of the antenna  110  between the radiating patch element  138  and lower surface  141 . In this exemplary embodiment, the feeding element  143  is electrically connected to and extends between the edges of the radiating patch element  138  and lower surface  141 . In other embodiments, however, the feeding element may be electrically connected to the radiating patch element and/or lower surface of the antenna at a location inwardly spaced from an edge. 
     Also shown in  FIG. 3 , the feeding element  143  includes tapering or inwardly slanted features  145  along opposite side portions of the feeding element  143 . The feeding element  143  with the tapering features  145  may be configured for impedance matching purposes that broaden antenna bandwidth, such that the antenna  110  is operable in at least two frequency bands. 
     In this illustrated embodiment, the tapering features  145  comprise side edge portions of the feeding element  143  that are slanted or angled inwardly towards the middle of feeding element  143 . Stated differently, the side edge portions  145  of the feeding element  143  are slanted or angled inwardly toward each other along these edge portions in a direction from the radiating patch element  138  downward towards the lower surface  141 . Accordingly, the upper portion of the feeding element  143  adjacent and connected to the radiating patch element  138  decreases in width due to the tapering features or inwardly angled upper side edge portions  145 . In alternative embodiments, the feeding elements  143  may include only one or no tapering features. 
     The lower surface  141  of the antenna  110  may also be considered a ground plane. But depending on the particular end use, the size of the lower surface  141  may be relatively small and of insufficient size for providing a fully effective ground plane. In such embodiments, the lower surface  141  may be used mostly for mechanically attaching the antenna  110  to a base  133 , which, in turn, is coupled to a sufficiently large enough ground plane. 
     The antenna  110  also includes first and second shorting elements  160 ,  162 . The first and second shorting elements  160 ,  162  electrically connect and extend between the radiating patch element  138  and the lower surface  141 . In this exemplary embodiment, the first and second shorting elements  160 ,  162  are electrically connected along the edges of the radiating patch element  138  and lower surface  141 . In other embodiments, however, the first and/or second shorting element  160 ,  162  may be electrically connected to the radiating patch element  138  and/or lower surface  141  at a location inwardly spaced from an edge. In addition, the first and second shorting elements  160 ,  162  may also help mechanically support the radiating patch element  138  above the lower surface  141  of the antenna  110 . 
     The first shorting element  160  may be configured or formed to provide basic antenna operations or functions. For example, the first shorting element  160  may be configured or formed to allow a smaller radiating patch element  138  to be used, e.g., smaller than one-half wavelength patch antenna. By way of example, the radiating patch  138  may be sized such that the sum of its length and width is about one-fourth wavelength (¼λ) of a desired resonant frequency. 
     The second shorting element  162  may be configured or formed to enhance or improve bandwidth of the antenna  110  at a first, low frequency range or bandwidth (e.g., frequencies from 698 megahertz to 960 megahertz, etc.). Thus, the second shorting element  162  may allow a smaller patch to be used by broadening the bandwidth. Accordingly, this exemplary antenna  110  includes double shorting (via the elements  160 ,  162 ) and a radiating element  138  with a slot  139  to excite multiple frequencies while enhancing the bandwidth of the antenna  110 . 
     In this exemplary embodiment, the first shorting element  160  is generally flat or planar, rectangular, and perpendicular to the upper radiating patch element  138  and lower surface  141 . Alternative embodiments may include a first shorting element configured differently, such as a non-flat shorting and/or a shorting that is non-perpendicular to the upper radiating patch element  138  and/or lower surface  141 . 
     Also in this exemplary embodiment, the second shorting element  162  is configured such that it has an overall length greater than the spaced distance or gap separating the radiating patch element  138  and the lower surface  141 . In this example, the second shorting element  162  has a non-planar or non-flat configuration. As shown in  FIG. 14 , the second shorting element  162  includes a first or lower portion  164  that is flat or planar. The first portion  164  is adjacent and perpendicular to the lower surface  141  of the antenna  110 . The second shorting element  162  also includes a second or upper portion  166  adjacent and connected to the radiating patch element  138 . The second portion  166  is not co-planar with and protrudes or extends outwardly relative to the first portion  164 , thus providing the second shorting element  162  with a three-dimensional, non-flat or non-planar configuration. 
     By way of example, the second portion  166  may comprise a bent portion, staircase-shaped portion, portion having a step configuration, etc. Differently-shaped first and/or second shorting elements may be disposed between a radiating patch element and a lower surface of an antenna in alternative embodiments. For example, the second shorting element  162  may have a flat configuration when viewed from the side. A second shorting element may be perpendicular to the upper and lower surfaces of the antenna  110 , where this second shorting element  162  may have a meandering or non-linear configuration when viewed from the front or back such that its length is greater than the spaced distance or gap separating the antenna&#39;s upper and lower surfaces. A second shorting element may be non-perpendicular to the upper and lower surfaces of the antenna  110 , where the second shorting element  162  has a length greater than the spaced distance or gap separating the antenna&#39;s upper and lower surfaces. The first and second shorting elements  160 ,  162  should not be limited to only the particular shapes illustrated in the figures. 
       FIG. 3  illustrates a capacitive loading element  170  of the antenna  110  configured or formed (e.g., bent or folded backwardly, etc.) to provide capacitive loading to widen the bandwidth of the antenna  110  at a second, high frequency range or bandwidth (e.g., frequencies from 1710 megahertz to 2700 megahertz, etc.). As shown in  FIG. 3 , the element  170  extends inwardly from the feeding element  143  and is disposed generally between the radiating patch element  138  and lower surface  141  of the antenna  110 . Alternative embodiments may be configured differently (e.g., without the capacitive loading or bend back element, etc.) than what is illustrated in  FIG. 3 . 
     As shown in  FIG. 14 , the illustrated embodiment of the antenna  110  includes capacitive loading elements or stubs  172  on opposite sides of the second shorting element  162 . These elements  172  are configured or formed so as to create capacitive loading for tuning the antenna  110  to one or more frequencies. For example, the elements  172  may be configured for tuning the antenna  110  to a first or low frequency range or bandwidth (e.g., frequencies from 698 megahertz to 960 megahertz, etc.) and to a second or high frequency or bandwidth (e.g., frequencies from 1710 megahertz to 2700 megahertz, etc.). Alternative embodiments may be configured differently (e.g., without the capacitive loading elements or stubs, etc.). 
     In exemplary embodiments, the antennas  110  may be integrally or monolithically formed from a single piece of electrically-conductive non-ferromagnetic material (e.g., brass, etc.) by stamping (e.g., via single stamping or progressive stamping technique, etc.) and then bending, folding, or otherwise forming the stamped piece of material. The antenna  110  may not include any dielectric (e.g., plastic) substrate that mechanically supports or suspends the upper radiating patch element  138  above the lower surface  141  or ground plane of the antenna  110 . Instead, the upper radiating patch element  138  of the antenna  110  may be mechanically supported above the lower surface  141  by the antenna&#39;s shorting elements. Accordingly, the antenna  110  may be considered as having an air-filled substrate or air gap between the upper radiating patch element  138  and lower surface  141 , which allows for cost savings due to the elimination of a dielectric substrate. Alternative embodiments may include a dielectric substrate that supports the upper radiating patch element above the ground plane or lower surface of the antenna and/or one or more components or elements that are not integrally formed, but which are separately attached to the antenna. 
     A wide range of materials may be used for the components of the antenna systems disclosed herein. By way of example, the antennas, isolators, and ground plane may all be made of brass or materials that are not ferromagnetic. In this example, there would preferably not be any ferromagnetic material or ferromagnetic components, which might otherwise be a source of PIM. The selection of the particular non-ferromagnetic material may depend on the suitability of the material for soldering, hardness, and costs. 
       FIGS. 18A through 18C  illustrate an exemplary embodiment  200  that includes the antenna system  100  ( FIGS. 2 through 5 ). A radome  235  is positioned over the antenna system  200  and coupled to the base  233 . In this example shown in  FIG. 18A , the base  233  has an outer diameter of about 219 millimeters (e.g., 218.7 millimeters+/−1 millimeter, etc.). The overall radome and base assembly ( FIG. 18B ) has an overall height of about 43.5 millimeters (e.g., 43.5 millimeters+/−1 millimeter, etc.). Also shown in  FIG. 18B  is a threaded portion protruding outwardly from the base  233 . By way of example only, the threaded portion may have a length of about 50.8 millimeters and 1″-8 thread size. Pigtail type connectors  251  are also shown extending outwardly from within the threaded portion. The antenna system  200  may be mounted to a support surface (e.g., ceiling, etc.) by positioning the base  233  on one side of the support surface and positioning and threading a mounting nut  246  and locking washer or gasket  248  (e.g., a rubber locking gasket, etc.) onto the threaded portion on the opposite side of the support surface. In exemplary embodiments that include a rubber locking gasket, the rubber locking gasket may be removed and not used when the antenna system  200  is going to be installed to ceiling tile. Exemplary dimensions in this paragraph and all other dimensions herein are provided for purposes of illustration only, as alternative embodiments may be sized differently. 
       FIGS. 19A and 19B  illustrate an exemplary embodiment  300  that also includes the antenna system  100  ( FIGS. 2 through 5 ), where a radome  335  is positioned over the antenna system  300  and coupled to the base  333 . But this exemplary embodiment  300  includes a fixed NF bulkhead connector instead of the pigtail type connection shown in  FIG. 18B . 
       FIGS. 20 through 29  provide analysis results measured for a prototype  200  shown in  FIGS. 18A, 18B, and 18C . The prototype  200  included the antenna system  100  ( FIGS. 2 through 5 ), which was positioned within a radome and configured with a pigtail type connection. These analysis results are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIG. 20  includes exemplary line graphs of Voltage Standing Wave Ratio (VSWR) (S 11 , S 22 ) and isolation (S 21  in decibels) versus frequency measured for the prototype antenna system  200 . Generally,  FIG. 20  shows that the prototype antenna system  200  is operable with good voltage standing wave ratios (VSWR) and with relatively good isolation between the two antennas  110 . 
       FIGS. 22 through 29  illustrate radiation patterns (azimuth plane, Phi 0° plane, and Phi 90° plane) measured for the first and second multi-band antennas  110  (shown in broken lines and solid lines) of the prototype antenna system  200  with the pigtail type connection and pattern orientation shown in  FIG. 21  at frequencies of about 698 megahertz (MHz), 824 MHz, 894 MHz, 960 MHz, 1785 MHz, 1910 MHz, 2110 MHz, and 2700 MHz, respectively. Generally,  FIGS. 22 through 29  show the quasi-omnidirectional radiation pattern (low profile antenna radiation pattern) and good efficiency of the antenna system  200 . Accordingly, the antenna system  200  has a large bandwidth that allows multiple operating bands for wireless communications devices, including FDD and TDD LTE frequencies or frequency bands. In addition, the antenna system  200  of this exemplary embodiment has vertical or horizontal polarization like a conventional PIFA antenna (e.g., PIFA  10  shown in  FIG. 1 , etc.). 
       FIGS. 30 and 31  are exemplary line graphs of passive intermodulation (PIM) versus frequency measured for ports  1  and  2  of the prototype antenna system  200  with the pigtail type connection ( FIG. 18B ). As shown, the antenna system  200  has low PIM performance (e.g., less than −150 dBc, etc.) at both a low band ( FIG. 30 ) and a high band ( FIG. 31 ). For example, the antenna system  200  may preferably have a low PIM of −153 dBc or less at low and high bands. 
     Immediately below are tables  1  and  2  with performance summary data measured for the first and second antennas  110  ( FIGS. 2 through 5 ) of the prototype antenna system  200  ( FIG. 18B ) with the pigtail type connection. As shown by the tables, the prototype antenna system  200  with the pigtail connection has good efficiency through the whole band with better efficiency at low band. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 (First Antenna with Pigtail Connection) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 3D 
                 Azimuth 
                 Elevation 0° 
                 Elevation 90° 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Frequency 
                   
                 Max 
                 Max 
                 Average 
                   
                 Max 
                 Average 
                 Max 
                 Average 
               
               
                 (MHz) 
                 Efficiency 
                 Gain 
                 Gain 
                 Gain 
                 Ripple 
                 Gain 
                 Gain 
                 Gain 
                 Gain 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 698 
                 76% 
                 1.92 
                 0.72 
                 −1.68 
                 5.96 
                 0.97 
                 −0.72 
                 0.81 
                 −1.02 
               
               
                 750 
                 89% 
                 1.87 
                 1.42 
                 −0.93 
                 5.52 
                 1.87 
                 0.08 
                 1.41 
                 −0.38 
               
               
                 800 
                 87% 
                 2.56 
                 1.36 
                 −0.98 
                 5.94 
                 2.24 
                 0.00 
                 1.88 
                 −0.84 
               
               
                 824 
                 80% 
                 2.58 
                 1.53 
                 −1.20 
                 6.69 
                 2.30 
                 −0.34 
                 1.86 
                 −1.28 
               
               
                 849 
                 79% 
                 3.25 
                 1.98 
                 −1.05 
                 8.89 
                 2.59 
                 −0.64 
                 1.71 
                 −1.56 
               
               
                 869 
                 78% 
                 3.58 
                 2.21 
                 −0.95 
                 9.74 
                 3.07 
                 −0.74 
                 1.72 
                 −1.88 
               
               
                 880 
                 74% 
                 3.54 
                 2.19 
                 −1.15 
                 10.39 
                 3.16 
                 −0.95 
                 1.55 
                 −2.26 
               
               
                 894 
                 74% 
                 3.93 
                 2.67 
                 −1.11 
                 11.53 
                 3.81 
                 −0.86 
                 1.18 
                 −2.63 
               
               
                 915 
                 74% 
                 4.61 
                 2.83 
                 −1.08 
                 13.56 
                 4.48 
                 −0.82 
                 1.02 
                 −3.17 
               
               
                 925 
                 77% 
                 4.88 
                 2.92 
                 −0.88 
                 14.17 
                 4.68 
                 −0.68 
                 1.31 
                 −3.14 
               
               
                 960 
                 78% 
                 4.40 
                 3.00 
                 −0.71 
                 12.66 
                 4.18 
                 −0.58 
                 1.37 
                 −3.27 
               
               
                 1710 
                 70% 
                 4.62 
                 1.59 
                 −2.85 
                 15.44 
                 4.52 
                 −0.42 
                 4.42 
                 0.07 
               
               
                 1785 
                 76% 
                 5.33 
                 −0.23 
                 −3.33 
                 9.92 
                 5.20 
                 −0.02 
                 4.66 
                 0.11 
               
               
                 1805 
                 74% 
                 5.37 
                 −0.76 
                 −3.54 
                 10.01 
                 5.27 
                 −0.11 
                 4.97 
                 −0.03 
               
               
                 1850 
                 68% 
                 4.88 
                 −0.83 
                 −3.41 
                 10.57 
                 4.88 
                 −0.54 
                 3.99 
                 −0.86 
               
               
                 1880 
                 69% 
                 4.84 
                 −0.46 
                 −3.10 
                 10.76 
                 4.83 
                 −0.52 
                 2.95 
                 −1.39 
               
               
                 1910 
                 69% 
                 4.34 
                 0.28 
                 −2.99 
                 11.26 
                 4.34 
                 −0.80 
                 2.11 
                 −1.93 
               
               
                 1920 
                 68% 
                 4.06 
                 0.47 
                 −2.92 
                 11.33 
                 4.06 
                 −0.94 
                 1.80 
                 −2.15 
               
               
                 1930 
                 67% 
                 3.83 
                 0.48 
                 −2.84 
                 11.33 
                 3.83 
                 −1.07 
                 1.45 
                 −2.37 
               
               
                 1980 
                 63% 
                 3.12 
                 0.20 
                 −2.76 
                 9.67 
                 3.08 
                 −1.39 
                 0.50 
                 −3.03 
               
               
                 1990 
                 63% 
                 3.01 
                 0.34 
                 −2.75 
                 9.61 
                 2.96 
                 −1.44 
                 0.47 
                 −3.04 
               
               
                 2110 
                 57% 
                 2.21 
                 −1.20 
                 −3.86 
                 8.42 
                 2.09 
                 −2.38 
                 1.88 
                 −2.35 
               
               
                 2170 
                 62% 
                 3.35 
                 −0.89 
                 −3.66 
                 8.72 
                 3.10 
                 −1.78 
                 2.25 
                 −1.92 
               
               
                 2500 
                 75% 
                 7.02 
                 −1.56 
                 −4.90 
                 11.04 
                 4.83 
                 −3.16 
                 6.03 
                 0.51 
               
               
                 2600 
                 72% 
                 7.17 
                 −1.83 
                 −5.26 
                 15.97 
                 4.21 
                 −3.30 
                 6.02 
                 0.42 
               
               
                 2700 
                 70% 
                 6.48 
                 −1.65 
                 −4.40 
                 8.04 
                 3.95 
                 −2.42 
                 5.61 
                 0.14 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 (Second Antenna with Pigtail Connection) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 3D 
                 Azimuth 
                 Elevation 0° 
                 Elevation 90° 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Frequency 
                   
                 Max 
                   
                 Average 
                   
                 Max 
                 Average 
                 Max 
                 Average 
               
               
                 (MHz) 
                 Efficiency 
                 Gain 
                 Max 
                 Gain 
                 Ripple 
                 Gain 
                 Gain 
                 Gain 
                 Gain 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 698 
                 77% 
                 1.81 
                 1.67 
                 −1.23 
                 8.16 
                 1.58 
                 −0.25 
                 1.03 
                 −1.01 
               
               
                 750 
                 89% 
                 2.11 
                 2.04 
                 −0.58 
                 7.64 
                 1.88 
                 0.38 
                 1.53 
                 −0.49 
               
               
                 800 
                 87% 
                 2.36 
                 1.87 
                 −0.65 
                 8.69 
                 2.13 
                 0.24 
                 1.83 
                 −1.05 
               
               
                 824 
                 81% 
                 2.42 
                 1.86 
                 −0.83 
                 8.96 
                 1.94 
                 −0.06 
                 1.68 
                 −1.48 
               
               
                 849 
                 79% 
                 2.90 
                 2.31 
                 −0.68 
                 10.96 
                 2.10 
                 −0.35 
                 1.13 
                 −1.73 
               
               
                 869 
                 77% 
                 3.02 
                 2.74 
                 −0.60 
                 13.16 
                 2.06 
                 −0.47 
                 0.93 
                 −2.08 
               
               
                 880 
                 73% 
                 3.15 
                 2.96 
                 −0.81 
                 14.07 
                 2.29 
                 −0.52 
                 0.44 
                 −2.41 
               
               
                 894 
                 74% 
                 3.49 
                 3.32 
                 −0.75 
                 16.11 
                 2.58 
                 −0.38 
                 0.29 
                 −2.68 
               
               
                 915 
                 75% 
                 4.00 
                 3.86 
                 −0.63 
                 18.31 
                 2.86 
                 −0.42 
                 0.10 
                 −3.12 
               
               
                 925 
                 78% 
                 4.23 
                 4.06 
                 −0.46 
                 18.40 
                 3.06 
                 −0.36 
                 0.24 
                 −3.08 
               
               
                 960 
                 79% 
                 4.31 
                 4.03 
                 −0.54 
                 15.76 
                 2.77 
                 −0.31 
                 1.04 
                 −3.12 
               
               
                 1710 
                 73% 
                 4.75 
                 1.45 
                 −2.67 
                 17.59 
                 4.66 
                 −0.63 
                 4.62 
                 0.34 
               
               
                 1785 
                 76% 
                 5.28 
                 −1.58 
                 −3.40 
                 6.98 
                 5.07 
                 −0.25 
                 4.83 
                 0.36 
               
               
                 1805 
                 74% 
                 5.28 
                 −1.78 
                 −3.54 
                 7.49 
                 5.16 
                 −0.32 
                 4.69 
                 0.13 
               
               
                 1850 
                 68% 
                 4.69 
                 −1.20 
                 −3.38 
                 8.49 
                 4.63 
                 −0.75 
                 3.88 
                 −0.73 
               
               
                 1880 
                 67% 
                 4.52 
                 −0.52 
                 −3.11 
                 10.06 
                 4.50 
                 −0.87 
                 3.09 
                 −1.32 
               
               
                 1910 
                 68% 
                 4.06 
                 0.49 
                 −2.66 
                 10.84 
                 4.05 
                 −0.95 
                 2.25 
                 −1.89 
               
               
                 1920 
                 68% 
                 3.90 
                 0.61 
                 −2.58 
                 10.95 
                 3.90 
                 −0.96 
                 2.03 
                 −2.07 
               
               
                 1930 
                 68% 
                 3.79 
                 0.70 
                 −2.53 
                 11.26 
                 3.79 
                 −0.99 
                 1.89 
                 −2.21 
               
               
                 1980 
                 64% 
                 3.17 
                 0.32 
                 −2.63 
                 10.79 
                 3.12 
                 −1.15 
                 1.56 
                 −2.75 
               
               
                 1990 
                 64% 
                 3.10 
                 0.38 
                 −2.57 
                 10.43 
                 3.05 
                 −1.16 
                 1.60 
                 −2.73 
               
               
                 2110 
                 67% 
                 2.96 
                 −0.02 
                 −2.70 
                 10.03 
                 2.86 
                 −1.28 
                 2.22 
                 −1.91 
               
               
                 2170 
                 61% 
                 3.27 
                 −0.65 
                 −3.46 
                 9.23 
                 2.57 
                 −2.20 
                 2.54 
                 −1.86 
               
               
                 2500 
                 76% 
                 7.03 
                 −1.16 
                 −4.87 
                 13.68 
                 4.39 
                 −3.29 
                 6.39 
                 0.81 
               
               
                 2600 
                 70% 
                 6.94 
                 −1.37 
                 −5.12 
                 17.34 
                 3.17 
                 −3.77 
                 6.16 
                 0.43 
               
               
                 2700 
                 73% 
                 6.55 
                 −1.38 
                 −3.98 
                 8.69 
                 2.96 
                 −2.93 
                 5.96 
                 0.37 
               
               
                   
               
            
           
         
       
     
       FIGS. 32 through 42  provide analysis results measured for a prototype  300  shown in  FIGS. 19A and 19B . The prototype  300  included the antenna system  100  ( FIGS. 2 through 5 ), which was positioned within a radome and configured with a fixed NF bulkhead connector. These analysis results are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIG. 32  includes exemplary line graphs of Voltage Standing Wave Ratio (VSWR) (S 11 , S 22 ) and isolation (S 21  in decibels) versus frequency measured for the prototype antenna system  300 . Generally,  FIG. 32  shows that the prototype antenna system  300  is operable with good voltage standing wave ratios (VSWR) and with relatively good isolation between the two antennas  110 . 
       FIGS. 33 through 40  illustrate radiation patterns (azimuth plane, Phi 0° plane, and Phi 90° plane) measured for the first and second multi-band antennas  110  (shown in solid lines and broken lines) of the prototype antenna system  300  with the fixed NF bulkhead connector ( FIG. 19B ) at frequencies of about 698 megahertz (MHz), 824 MHz, 894 MHz, 960 MHz, 1785 MHz, 1910 MHz, 2110 MHz, and 2700 MHz, respectively. The pattern orientation for this series of testing is the same as that shown in  FIG. 21 . Generally,  FIGS. 33 through 40  show the quasi-omnidirectional radiation pattern (low profile antenna radiation pattern) and good efficiency of the antenna system  300 . Accordingly, the antenna system  300  has a large bandwidth that allows multiple operating bands for wireless communications devices, including FDD and TDD LTE frequencies or frequency bands. In addition, the antenna system  300  of this exemplary embodiment has vertical or horizontal polarization like a conventional PIFA antenna (e.g., conventional PIFA  10  in  FIG. 1 , etc.). 
       FIGS. 41 and 42  are exemplary line graphs of passive intermodulation (PIM) versus frequency measured for ports  1  and  2  of the prototype antenna system  300  with the fixed NF bulkhead connector ( FIG. 19B ). As shown, the antenna system  300  has low PIM performance (e.g., less than −150 dBc, etc.) at both a low band ( FIG. 41 ) and a high band ( FIG. 42 ). For example, the antenna system  300  may preferably have a low PIM of −153 dBC or less at low and high bands. 
     Immediately below are tables  3  and  4  with performance summary data measured for the first and second antennas  110  ( FIGS. 2 through 5 ) of the prototype antenna system  300  ( FIG. 19B ) with the fixed NF bulkhead connector. As shown, the prototype antenna system  300  with the fixed NF bulkhead connector has good efficiency through the whole band with better efficiency at low band. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 (First Antenna with fixed NF Bulkhead Connector) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 3D 
                 Azimuth 
                 Elevation 0° 
                 Elevation 90° 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Frequency 
                   
                 Max 
                   
                 Average 
                   
                 Max 
                 Average 
                 Max 
                 Average 
               
               
                 (MHz) 
                 Efficiency 
                 Gain 
                 Max 
                 Gain 
                 Ripple 
                 Gain 
                 Gain 
                 Gain 
                 Gain 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 698 
                 84% 
                 2.54 
                 −0.36 
                 −2.55 
                 16.72 
                 2.40 
                 −0.21 
                 2.52 
                 0.34 
               
               
                 750 
                 91% 
                 2.68 
                 0.54 
                 −1.87 
                 15.76 
                 2.46 
                 0.35 
                 2.59 
                 0.47 
               
               
                 800 
                 91% 
                 3.50 
                 0.00 
                 −1.95 
                 10.09 
                 3.32 
                 0.39 
                 3.49 
                 0.20 
               
               
                 824 
                 85% 
                 3.50 
                 −0.14 
                 −2.17 
                 10.21 
                 3.36 
                 0.04 
                 3.48 
                 0.01 
               
               
                 849 
                 83% 
                 2.83 
                 0.59 
                 −1.94 
                 10.73 
                 2.27 
                 −0.12 
                 2.75 
                 −0.13 
               
               
                 869 
                 84% 
                 2.21 
                 1.03 
                 −1.82 
                 11.91 
                 2.10 
                 −0.12 
                 2.15 
                 −0.26 
               
               
                 880 
                 80% 
                 2.11 
                 0.82 
                 −2.06 
                 12.21 
                 2.11 
                 −0.29 
                 2.11 
                 −0.51 
               
               
                 894 
                 80% 
                 2.43 
                 1.20 
                 −2.09 
                 13.40 
                 2.42 
                 −0.23 
                 2.43 
                 −0.57 
               
               
                 915 
                 81% 
                 2.54 
                 1.38 
                 −2.01 
                 13.70 
                 2.54 
                 −0.31 
                 2.51 
                 −0.41 
               
               
                 925 
                 86% 
                 2.75 
                 1.59 
                 −1.64 
                 13.70 
                 2.74 
                 −0.28 
                 2.68 
                 −0.12 
               
               
                 960 
                 87% 
                 3.43 
                 3.06 
                 −0.93 
                 13.78 
                 2.49 
                 −0.47 
                 2.86 
                 −0.11 
               
               
                 1710 
                 70% 
                 5.39 
                 −0.67 
                 −3.89 
                 10.68 
                 5.27 
                 0.16 
                 5.37 
                 0.12 
               
               
                 1785 
                 79% 
                 5.71 
                 −1.46 
                 −3.06 
                 6.42 
                 5.57 
                 0.30 
                 5.13 
                 −0.13 
               
               
                 1805 
                 79% 
                 5.74 
                 −1.32 
                 −3.03 
                 6.41 
                 5.45 
                 0.29 
                 5.53 
                 −0.22 
               
               
                 1850 
                 70% 
                 5.33 
                 −0.78 
                 −3.40 
                 8.19 
                 5.29 
                 −0.13 
                 5.12 
                 −0.90 
               
               
                 1880 
                 69% 
                 5.17 
                 −0.22 
                 −3.02 
                 9.88 
                 5.15 
                 −0.29 
                 4.44 
                 −1.76 
               
               
                 1910 
                 69% 
                 4.40 
                 0.58 
                 −2.63 
                 11.72 
                 4.39 
                 −0.57 
                 3.74 
                 −2.18 
               
               
                 1920 
                 69% 
                 4.08 
                 0.40 
                 −2.51 
                 11.41 
                 4.07 
                 −0.64 
                 3.39 
                 −2.33 
               
               
                 1930 
                 69% 
                 3.90 
                 0.43 
                 −2.33 
                 10.98 
                 3.85 
                 −0.67 
                 2.96 
                 −2.55 
               
               
                 1980 
                 69% 
                 3.51 
                 1.36 
                 −2.14 
                 10.12 
                 3.49 
                 −0.69 
                 1.87 
                 −3.09 
               
               
                 1990 
                 68% 
                 3.46 
                 1.32 
                 −2.22 
                 10.51 
                 3.44 
                 −0.78 
                 1.75 
                 −3.16 
               
               
                 2110 
                 65% 
                 2.94 
                 0.68 
                 −2.56 
                 11.16 
                 2.93 
                 −1.47 
                 0.82 
                 −3.52 
               
               
                 2170 
                 69% 
                 3.56 
                 1.13 
                 −2.64 
                 13.70 
                 3.32 
                 −1.25 
                 1.91 
                 −2.54 
               
               
                 2500 
                 73% 
                 5.81 
                 0.44 
                 −3.50 
                 17.60 
                 3.13 
                 −2.74 
                 5.48 
                 0.47 
               
               
                 2600 
                 71% 
                 6.15 
                 1.08 
                 −3.17 
                 13.94 
                 1.47 
                 −3.62 
                 5.61 
                 −0.13 
               
               
                 2700 
                 71% 
                 5.99 
                 0.85 
                 −2.74 
                 10.99 
                 2.62 
                 −3.02 
                 4.70 
                 −0.48 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 (Second Antenna with fixed NF Bulkhead Connector) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 3D 
                 Azimuth 
                 Elevation 0° 
                 Elevation 90° 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Frequency 
                   
                 Max 
                   
                 Average 
                   
                 Max 
                 Average 
                 Max 
                 Average 
               
               
                 (MHz) 
                 Efficiency 
                 Gain 
                 Max 
                 Gain 
                 Ripple 
                 Gain 
                 Gain 
                 Gain 
                 Gain 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 698 
                 83% 
                 2.26 
                 −0.47 
                 −2.71 
                 10.89 
                 2.23 
                 −0.37 
                 2.24 
                 0.30 
               
               
                 750 
                 93% 
                 2.96 
                 0.52 
                 −1.95 
                 11.07 
                 2.53 
                 0.23 
                 2.83 
                 0.43 
               
               
                 800 
                 93% 
                 3.40 
                 0.18 
                 −1.81 
                 9.00 
                 3.20 
                 0.09 
                 3.40 
                 0.24 
               
               
                 824 
                 87% 
                 3.17 
                 0.34 
                 −2.02 
                 9.85 
                 3.10 
                 −0.20 
                 3.16 
                 0.06 
               
               
                 849 
                 87% 
                 2.50 
                 0.78 
                 −1.87 
                 10.74 
                 2.09 
                 −0.27 
                 2.45 
                 −0.11 
               
               
                 869 
                 85% 
                 2.16 
                 0.75 
                 −1.90 
                 10.97 
                 1.18 
                 −0.31 
                 2.10 
                 −0.34 
               
               
                 880 
                 82% 
                 1.70 
                 0.62 
                 −2.18 
                 11.84 
                 1.52 
                 −0.36 
                 1.51 
                 −0.55 
               
               
                 894 
                 82% 
                 1.97 
                 1.13 
                 −2.16 
                 12.09 
                 1.74 
                 −0.30 
                 1.48 
                 −0.68 
               
               
                 915 
                 83% 
                 2.25 
                 1.40 
                 −1.97 
                 13.57 
                 1.87 
                 −0.46 
                 1.37 
                 −0.65 
               
               
                 925 
                 89% 
                 2.66 
                 1.68 
                 −1.58 
                 14.18 
                 2.33 
                 −0.34 
                 2.05 
                 −0.36 
               
               
                 960 
                 91% 
                 3.44 
                 2.57 
                 −1.07 
                 14.28 
                 2.88 
                 −0.36 
                 2.94 
                 −0.31 
               
               
                 1710 
                 73% 
                 5.33 
                 0.52 
                 −3.63 
                 12.47 
                 5.13 
                 0.32 
                 5.25 
                 0.31 
               
               
                 1785 
                 79% 
                 5.59 
                 −0.67 
                 −2.86 
                 6.80 
                 5.46 
                 0.14 
                 5.11 
                 −0.12 
               
               
                 1805 
                 79% 
                 5.68 
                 −0.15 
                 −2.77 
                 7.27 
                 5.57 
                 0.12 
                 5.07 
                 −0.29 
               
               
                 1850 
                 68% 
                 5.32 
                 0.13 
                 −2.87 
                 9.74 
                 4.96 
                 −0.59 
                 4.30 
                 −1.36 
               
               
                 1880 
                 60% 
                 4.42 
                 0.16 
                 −2.75 
                 11.07 
                 4.18 
                 −1.01 
                 3.65 
                 −2.11 
               
               
                 1910 
                 66% 
                 4.33 
                 0.97 
                 −2.46 
                 14.67 
                 4.16 
                 −0.65 
                 3.72 
                 −1.95 
               
               
                 1920 
                 68% 
                 4.21 
                 1.21 
                 −2.28 
                 15.27 
                 4.06 
                 −0.60 
                 3.39 
                 −1.99 
               
               
                 1930 
                 70% 
                 4.18 
                 0.99 
                 −2.13 
                 13.04 
                 4.03 
                 −0.53 
                 3.06 
                 −2.01 
               
               
                 1980 
                 73% 
                 4.07 
                 1.49 
                 −2.16 
                 12.07 
                 4.07 
                 −0.31 
                 3.36 
                 −2.17 
               
               
                 1990 
                 73% 
                 4.09 
                 1.61 
                 −2.11 
                 11.94 
                 4.09 
                 −0.35 
                 3.33 
                 −2.18 
               
               
                 2110 
                 70% 
                 3.16 
                 1.42 
                 −2.29 
                 12.74 
                 2.92 
                 −1.17 
                 2.29 
                 −2.90 
               
               
                 2170 
                 71% 
                 3.89 
                 1.08 
                 −2.34 
                 14.62 
                 3.69 
                 −1.42 
                 2.21 
                 −2.22 
               
               
                 2500 
                 75% 
                 6.07 
                 −0.34 
                 −3.77 
                 18.20 
                 3.79 
                 −2.69 
                 5.48 
                 0.68 
               
               
                 2600 
                 72% 
                 6.26 
                 1.07 
                 −3.13 
                 15.42 
                 2.34 
                 −3.24 
                 5.39 
                 −0.18 
               
               
                 2700 
                 74% 
                 6.26 
                 1.18 
                 −2.60 
                 10.73 
                 3.25 
                 −2.54 
                 4.74 
                 −0.41 
               
               
                   
               
            
           
         
       
     
     Exemplary embodiments of the antenna systems disclosed herein allow multiple operating bands for wireless communications devices. By way of example, an antenna system as disclosed herein may be configured to be operable or cover FDD (Frequency Division Duplex) and TDD (Time Division Duplex) LTE (Long Term Evolution) frequency bands (Table 5 below) as defined by 3GPP (3 rd  Generation Partnership Project). By way of background, different frequency bands are used to send and receive operations with the FDD technique so that sending and receiving data signals don&#39;t interfere with each other. By comparison, the TDD technique allocates different time slots in the same frequency band to separate uplink from downlink. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Band 
                 Uplinks MHz 
                 Downlink MHz 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 1 
                 1920-1980 
                 2110-2170 
                 FDD 
               
               
                 2 
                 1850-1910 
                 1930-1990 
                 FDD 
               
               
                 3 
                 1710-1785 
                 1805-1880 
                 FDD 
               
               
                 4 
                 1710-1755 
                 2110-2155 
                 FDD 
               
               
                 5 
                 824-849 
                 869-894 
                 FDD 
               
               
                 6 
                 830-840 
                 875-885 
                 FDD 
               
               
                 7 
                 2500-2570 
                 2620-2690 
                 FDD 
               
               
                 8 
                 880-915 
                 925-960 
                 FDD 
               
               
                 9 
                 1749-1784 
                 1844-1879 
                 FDD 
               
               
                 10 
                 1710-1770 
                 2110-2170 
                 FDD 
               
               
                 11 
                 1427-1452 
                 1475-1500 
                 FDD 
               
               
                 12 
                 698-716 
                 728-746 
                 FDD 
               
               
                 13 
                 777-787 
                 746-756 
                 FDD 
               
               
                 14 
                 788-798 
                 758-768 
                 FDD 
               
               
                 17 
                 704-716 
                 734-746 
                 FDD 
               
               
                 18 
                 815-830 
                 860-875 
                 FDD 
               
               
                 19 
                 830-845 
                 875-890 
                 FDD 
               
               
                 20 
                 832-862 
                 791-821 
                 FDD 
               
               
                 21 
                 1448-1463 
                 1496-1511 
                 FDD 
               
               
                 33 
                 1900-1920 
                 1900-1920 
                 TDD 
               
               
                 34 
                 2010-2025 
                 2010-2025 
                 TDD 
               
               
                 35 
                 1850-1910 
                 1850-1910 
                 TDD 
               
               
                 36 
                 1930-1990 
                 1930-1990 
                 TDD 
               
               
                 37 
                 1910-1930 
                 1910-1930 
                 TDD 
               
               
                 38 
                 2570-2620 
                 2570-2620 
                 TDD 
               
               
                 39 
                 1880-1920 
                 1880-1920 
                 TDD 
               
               
                 40 
                 2300-2400 
                 2300-2400 
                 TDD 
               
               
                   
               
            
           
         
       
     
     In exemplary embodiments, an antenna system that includes one or more multi-band antennas (e.g., antenna with double shorting and modified from the PIFA antenna shown in  FIG. 1 , a modified PIFA with double shorting, etc.) may be operable for covering all of the above-listed frequency bands with good voltage standing wave ratios (VSWR) and with relatively good efficiency. Alternative embodiments may include an antenna system operable at less than or more than all of the above-identified frequencies and/or be operable at different frequencies than the above-identified frequencies. 
     Exemplary embodiments of the antenna systems (e.g.,  100 ,  200 ,  300 , etc.) disclosed herein are suitable for a wide range of applications, e.g., that use more than one antenna, such as LTE/4G applications and/or infrastructure antenna systems (e.g., customer premises equipment (CPE), satellite navigation systems, alarm systems, terminal stations, central stations, in-building antenna systems, etc.). An antenna system (e.g.,  100 ,  200 ,  300 , etc.) may be configured for use as an omnidirectional MIMO antenna, although aspects of the present disclosure are not limited solely to omnidirectional and/or MIMO antennas. An antenna system (e.g.,  100 ,  200 ,  300 , etc.) disclosed herein may be implemented inside an electronic device, such as machine to machine, vehicular, in-building unit, etc. In which case, the internal antenna components would typically be internal to and covered by the electronic device housing. As another example, the antenna system may instead be housed within a radome, which may have a low profile. In this latter case, the internal antenna components would be housed within and covered by the radome. Accordingly, the antenna systems disclosed herein should not be limited to any one particular end use. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. In addition, advantages and improvements that may be achieved with one or more exemplary embodiments of the present disclosure are provided for purpose of illustration only and do not limit the scope of the present disclosure, as exemplary embodiments disclosed herein may provide all or none of the above mentioned advantages and improvements and still fall within the scope of the present disclosure. 
     Specific dimensions, specific materials, and/or specific shapes disclosed herein are example in nature and do not limit the scope of the present disclosure. The disclosure herein of particular values and particular ranges of values for given parameters are not exclusive of other values and ranges of values that may be useful in one or more of the examples disclosed herein. Moreover, it is envisioned that any two particular values for a specific parameter stated herein may define the endpoints of a range of values that may be suitable for the given parameter (i.e., the disclosure of a first value and a second value for a given parameter can be interpreted as disclosing that any value between the first and second values could also be employed for the given parameter). For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     The term “about” when applied to values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters. For example, the terms “generally,” “about,” and “substantially,” may be used herein to mean within manufacturing tolerances (e.g., angle+/−30′, 0-place decimal+/−0.5, 1-place decimal+/−0.25, 2-place decimal+/−0.13, etc.). Whether or not modified by the term “about,” the claims include equivalents to the quantities. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.