Patent Publication Number: US-8988295-B2

Title: Multiband antenna assemblies with matching networks

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/236,382 filed Sep. 19, 2011. This application is also a nonprovisional of U.S. Provisional Patent Application No. 61/701,814 filed Sep. 17, 2012. The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to matching networks and multiband antenna assemblies including the same that are operable with high gain and broad bandwidth coverage. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Multiband antennas typically include multiple antennas to cover and operate multiple frequency ranges. A printed circuit board (PCB) having a radiating antenna element thereon is a typical component of a multiband antenna assembly. Another typical component of a multiband antenna assembly is an external antenna, such as an aerial whip antenna rod. The multiband antenna assembly may be mounted to an antenna mount, which, in turn, is installed or mounted on a vehicle surface, such as the roof, trunk, or hood of the vehicle. The antenna mount may be interconnected (e.g., via a coaxial cable, etc.) to one or more electronic devices (e.g., a radio device, etc.), such that the multiband antenna is then operable for transmitting and/or receiving radio frequency signals to/from the radio device via the antenna mount. 
     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 base assemblies that include matching networks and multiband antenna assemblies including the same. For example, an exemplary embodiment of a base assembly includes a printed circuit board and a balun coupled to the printed circuit. The printed circuit board and balun are configured to be operable for providing impedance matching via a matching network that includes a first inductor, a second inductor, and a concentric capacitance. The base assembly is operable for providing a multiband antenna assembly with impedance matching simultaneously with more than one frequency band. 
     Another exemplary embodiment includes a multiband antenna assembly operable in at least a very high frequency (VHF) band from 136 Megahertz (MHz) to 174 MHz, an ultra high frequency (UHF) band from 380 MHz to 520 MHz, and a 700/800 MHz frequency band from 760 MHz to 870 MHz. The multiband antenna assembly includes a base assembly operable for providing impedance matching simultaneously with the VHF band, the UHF band, and the 700/800 MHz frequency band. An aerial whip antenna assembly is mounted to the base assembly. The base assembly includes a printed circuit board and a balun coupled to the printed circuit. The base assembly also includes a base ring portion configured for mounting the base assembly to an antenna mount. A contact pin is configured for providing an electrical connection between a contact of the antenna mount and the printed circuit board when the base assembly is mounted to the antenna mount. 
     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  is a perspective view of an exemplary spring contact assembly suitable for providing a solderless connection between a printed circuit board (PCB) and a center contact of an external antenna mount according to an exemplary embodiment; 
         FIG. 2  is an exploded perspective of the spring contact assembly shown in  FIG. 1 , and also illustrating an exemplary PCB configured for use with the spring contact assembly according to an exemplary embodiment; 
         FIG. 3  is a perspective view illustrating the spring contact assembly coupled to the PCB shown in  FIG. 2 ; 
         FIG. 4  is a side view of the spring contact assembly and PCB shown in  FIG. 3 ; 
         FIG. 5  is a top view of the spring contact assembly and PCB shown in  FIG. 3 ; 
         FIG. 6  is a lower perspective view of the spring contact assembly and PCB shown in  FIG. 3 ; 
         FIG. 7  is a cross sectional view of the spring contact assembly and PCB shown in  FIG. 3 , and illustrating the spring in an uncompressed, relaxed condition; 
         FIG. 8  is another cross sectional view of the spring contact assembly and PCB shown in  FIG. 3 , but now illustrating the spring in compressed condition; 
         FIG. 9  is an exploded perspective view of an antenna base assembly according to an exemplary embodiment; 
         FIG. 10  is a perspective view of the antenna base assembly shown in  FIG. 9  after being assembled together; 
         FIG. 11  is a perspective view of the antenna base assembly shown in  FIG. 10  with the housing installed; 
         FIG. 12  illustrates an exemplary multiband antenna assembly including the spring contact assembly shown in  FIG. 1 , the antenna base assembly shown in  FIG. 9 , and an exemplary external mobile antenna mount according to an exemplary embodiment; 
         FIG. 13  is an exploded perspective view of a multiband antenna assembly according to an exemplary embodiment; 
         FIG. 14  is a perspective view of the multiband antenna assembly shown in  FIG. 13  after being assembled; 
         FIG. 15  illustrates the multiband antenna assembly shown in  FIG. 14  with the housing shown in cross section to illustrate the antenna base assembly; 
         FIG. 16  illustrates the antenna base assembly shown in  FIG. 15 ; 
         FIG. 17  illustrates the multiband antenna assembly shown in  FIG. 15  side by side with a circuit diagram graphically representing the matching network provided by the base assembly and graphically representing components of the aerial whip assembly; 
         FIG. 18  is a circuit diagram graphically representing the full matching network shown in  FIG. 17  provided by the base assembly, including the concentric capacitance (C 2 ) between first and second inductors (L 1  and L 2 ) and the capacitances from ground (C 1 ); 
         FIG. 19  illustrates the multiband antenna assembly shown in  FIGS. 14 and 15  without the antenna base housing and with the phase coil housing shown in cross section, where the dimensions in millimeters [inches] are provided for purpose of illustration only according to an exemplary embodiment; 
         FIG. 20  is an exemplary line graph illustrating voltage standing wave ratio (VSWR) versus frequency in megahertz (MHZ) measured for a prototype of an antenna assembly having features and dimensions shown in  FIG. 19 ; 
         FIGS. 21A ,  21 B, and  21 C illustrate azimuth field radiation patterns measured for a prototype of an antenna assembly having features and dimensions shown in  FIG. 19  at frequencies of 156 MHz, 450 MHz, and 810 MHz; and 
         FIGS. 22A and 22B  illustrate elevation field radiation patterns measured for a prototype of an antenna assembly having features and dimensions shown in  FIG. 19  at frequencies of 450 MHz and 810 MHz. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Disclosed herein are exemplary embodiments of spring contact assemblies suitable for providing a solderless connection between a printed circuit board (PCB) and a contact. In an exemplary embodiment, a spring contact assembly may be used to provide a solderless connection between a center contact (e.g., pin, etc.) of an external antenna mount and an internal antenna element on a PCB of a multiband antenna assembly. In such exemplary embodiment, the spring contact assembly thus may be used as a connecting device to physically interconnect (without soldering) the center contact from the external antenna mount to the internal antenna element, such that radio frequency (RF) signals, electrical current, and/or modulated RF signals may be transferred (transmitted, or received) via the spring contact assembly between the multiband antenna assembly and a radio device coupled to the antenna mount, such as via a coaxial cable. Additional aspects of the present disclosure also include methods of connecting a center contact from an external antenna mount to an internal antenna element of a printed circuit board without soldering. 
     In addition to the spring contact assemblies disclosed herein, there are also disclosed exemplary embodiments of sealed antenna base assemblies. The sealed antenna base assemblies may be used individually or in conjunction with a spring contact assembly, or either may be used individually. Accordingly, an antenna assembly may include either or both of a sealed antenna base assembly and/or a spring contact assembly according to aspects of the present disclosure. 
     Multiband antenna structures commonly include PCBs, which require electrical ground sources. Typically, the ground sources are fed at deferent locations at the base of the PCB. Conventionally, grounding sources have been made available but the inventors hereof have recognized that such conventional methods breached the base of the antenna sacrificing the moisture and water seals. Accordingly, the inventors hereof have disclosed antenna base assemblies that provide the ground sources for the PCB while also maintaining a sealed base (e.g., a moisture, water, and/or dust sealed base, etc.). In an exemplary embodiment, there is an internal radiating element sealed foundation inside an antenna structure, which functions as an adaptor to mate an external antenna mount into the feeding point of a radiating element. This exemplary embodiment provides satisfactory multiple electrical grounding sources while preserving the sealing features. Additional aspects of the present disclosure also include methods of providing multiple electrical grounding sources for a printed circuit board without breaching the seal(s) of an antenna base assembly, thereby preserving the sealed interior of the antenna base assembly in which the printed circuit board is housed. 
     Additionally, there are also disclosed exemplary embodiments of antenna base body assemblies for multiband antennas. For example, an exemplary embodiment of a base body assembly is configured to provide or have a unique matching network structure operable for providing impedance matching and that works simultaneously with a wide band frequency spectrum (e.g., VHF 136-174 MHz, UHF 380-520 MHz, and Cell/LTE 700/800 MHz), supplementing a single Aerial structure of broadband coverage. In pursuing a balance of antenna aesthetic look, performance, and low cost on the LMR (Land, Mobile, Radio) realm, the inventors hereof sought to develop and disclose herein an exemplary embodiment of a single full spectrum antenna operable with VHF 136-174 MHz, UHF 380-520 MHz, and Cell/LTE 700/800 MHz in an overall antenna package that may be less than 20 inches in height and that has a relatively small base as a mechanical support for mounting on a standard vehicle for public safety wireless applications. As disclosed herein, an exemplary embodiment of an antenna assembly includes a vertically mounted mobile aerial structure. A primary aerial whip assembly is coupled or mounted to a base body assembly. The base body assembly may include a hermetically sealed housing and a base cap. The base body assembly may be encompass or be configured so as to provide a unique matching network. The primary aerial whip assembly may include a shock absorbing spring mounted to or coupled to the base body assembly. The primary aerial whip assembly may also include two metal rods top mounted to the shock absorbing spring. A radio wave impedance matching helical spring (or phasing coil) electrically connects and linearly joins the two metal rods with a separation or spaced distance between the two rods. An aerial radio waves defusing metal ball is coupled (e.g., via a press fit, etc.) to an upper portion of the top linearly mounted rod. For example, the top linearly mounted rod may be pressed into an opening or hole in the aerial radio waves defusing metal ball. 
     With reference now to the figures,  FIGS. 1 through 8  illustrate an exemplary embodiment of a spring contact assembly  100  embodying one or more aspects of the present disclosure. As disclosed herein, the spring contact assembly  100  may be used in a multiband antenna assembly (e.g., multiband antenna assembly  390  shown in  FIG. 12 , multiband antenna assembly  490  shown in  FIGS. 13 and 14 , etc.) to provide a solderless connection between a printed circuit board (PCB)  124  ( FIG. 2 ) (broadly, a substrate) and a center contact of an external antenna mount (e.g., center contact  397  of antenna mount  396  shown in  FIG. 12 , etc.). The spring contact assembly  100  may be used in conjunction with a sealed antenna base assembly, such as the sealed antenna base assembly  250  shown in  FIG. 9 . But the spring contact assembly  100  may also be used with other antenna base assemblies and/or other antenna assemblies than what is disclosed herein. 
     As shown in  FIG. 2 , the spring contact assembly  100  generally includes a body  104 , a spring  108  (broadly, a biasing member), a housing  112  (broadly, contact member), a bearing  116  (broadly, ring or annular member), and a rivet or pin  120  (broadly, a fastener or locking member).  FIG. 2  also illustrates the exemplary PCB  124 , which is provided with a hole or opening  128  configured for receiving the rivet  120  therein. The PCB  124  also includes a notch or cutout area  132  configured to accommodate positioning of portions  138  of body  104  about the opposite sides of the PCB  124 . With this relative positioning, the holes  142  in the body&#39;s portions  138  may be aligned with the hole  130  in the PCB  124  for receiving the rivet  120  therethrough. 
     When the holes  130 ,  142  are aligned, the rivet  120  may be positioned through the aligned holes  128 ,  130  to thereby connect or lock the spring contact assembly  100  to the substrate, board or body of the PCB  124  as shown in  FIG. 7 . The body&#39;s portions  138  and/or rivet  120  may electrically connect with (e.g., galvanically contact, etc.) one or more electrically-conductive portions (e.g., feeding point, radiating element, traces, etc.) of the PCB  124 . 
     With the spring contact assembly  100  coupled to the PCB  124  via the rivet  120 , the other end of the spring contact assembly  100  may be used to physically interconnect or electrically connect with a contact, such as a center contact of an external radio antenna mount (e.g., center contact  397  of antenna mount  396  shown in  FIG. 12 , etc.). By way of example, the spring contact assembly  100  may connect or mate the center contact of the antenna mount with a feeding point of a radiating element on the PCB  124 . In which case, the spring contact assembly  100  may then be used for transferring, transmitting, and/or receiving radio frequency (RF) signals, electrical current, and/or modulated RF signals between an external device (e.g., radio unit connected to the antenna mount  396  via a coaxial cable  399 , etc.) and the antenna assembly (e.g.,  390  ( FIG. 12 ),  490  ( FIGS. 13 and 14 ), etc.) including the spring contact assembly  100 . 
       FIG. 7  illustrates the spring  108  in its initial relaxed, uncompressed condition within the respective open end portions  106 ,  114  of the body  104  and housing  112  between their respective closed end portions  107 ,  113 . But when the spring contact assembly  100  is assembled between the PCB  124  and the external radio antenna mount, the housing  112  moves or slides at least partially along, within, or into the open end portion  106  tubular body  104  of the spring contact assembly  100  as shown by a comparison of  FIGS. 7 and 8 . This relative sliding movement of the housing  112  into the body  104  compresses the spring  108  ( FIG. 8 ) between the interior surface of the closed end portion  113  of the housing  112  and the interior surface of the closed end portion  107  of the body  104 . With this compression, the spring  108  is operable for providing a biasing force for urging the housing  112  to slide relative to the body  104  in a direction generally away from the closed end portion  107  of the body  104 . Accordingly, the spring  108  is thus operable for biasing, pressure loading, or spring loading the housing  112  and its end portion  113  (e.g., contact pin, etc.) into good electrical contact with a center contact of an antenna mount. At which point, the spring contact assembly  100  may thus transfer signals or electrical current between the antenna mount center contact and the PCB  124 . 
     With continued reference to  FIG. 2 , the various components of this illustrated embodiment of the spring contact assembly  100  will now be described in more detail for this example. The body  104  is cylindrical and electrically-conductive. The body  104  also includes an open end portion  106  and a closed end portion  107 . The body  104  also includes generally flat spaced-apart portions or flats  138 , which protrude or extend outwardly from the closed end portion  107 . These portions  138  include thru holes  142  aligned with each other for receiving the rivet  120  therethrough. The spacing between the body&#39;s portions  138  is predetermined or configured so as to be about equal to (e.g., only slightly larger) the thickness of the substrate or board of the PCB  124  to which the spring contact assembly  100  will be mounted. The body&#39;s portions  138  may be configured so as to snugly receive or grip the PCB substrate or board therebetween to thereby form an interference or friction fit. The body  104  may be made from any suitable electrically-conductive material, such as metal (e.g., brass, etc.) or other materials. 
     The spring  108  in this example embodiment is a helical metal compression coil spring made from a stainless steel alloy material. In operation, the spring  108  is operable for biasing or pressure loading the housing  112  and its end portion  113  into good electrical contact with a center contact of an external antenna mount. While this illustrated embodiment includes a coil spring, other suitable biasing members besides coil springs made from stainless steel alloy may be used in other embodiments. 
     The housing  112  includes a closed end portion  113  and open end portion  114  for receiving the spring  108  therein as shown in  FIGS. 7 and 8 . The closed end portion  113  is biased by the spring  108  when compressed ( FIG. 8 ) so that good electrical contact is established and maintained with a center contact of an external antenna mount. In this example, the housing  112  includes a cold drawn cup or cup-shaped member made from brass sheet metal and plated with gold for the purpose of corrosion resistance and maintenance of long term surface contact transitioning RF electrical current. The housing  112  includes a rim or lip  147  that is larger than the central opening of ring or annular member  116 , such that the housing  112  is retained to the body  104  and cannot be completely slid out of the body  104 . 
     While this illustrated embodiment includes a cup-shaped cold drawn housing  112  from brass sheet metal plated with gold, other embodiments may include housings with a different configuration, such as housings formed from other materials and/or other manufacturing processes. 
     Also in this illustrated embodiment, the ring or annular member  116  is a bearing that is inserted into the body  104  so as to provide a bearing surface for rotary and linear movement of the housing  112  relative to the bearing  116  and body  104 . The annular member  116  also prevents or at least inhibits the housing  112  from being slid completely out of the body  104 . The bearing  116  may be coupled to the inner walls of the body  104  via mechanical compression, interference/friction fit, or other suitable method. As shown in  FIG. 7 , the bearing  116  is in abutting contact with an internal shoulder  148  of the body  104 . 
     In this example, the rivet  120  is used as a mechanical fastener that couples the spring contact assembly  100  to the PCB  124 . The rivet  120  is a permanent or fixed mechanical fastener in this example that is not removable from the holes of the PCB  124  and body  104  after installation. Before being installed, the rivet  120  includes a smooth cylindrical shaft with a head  121  on one end ( FIG. 2 ). The end opposite the head  121  is called the buck-tail  122 . During installation, the rivet  120  is placed in the aligned holes  128 ,  142 . Then, the tail  122  of the rivet  120  is upset, bucked, or deformed (as shown by  FIG. 7 ) so that it expands (e.g., to about 1.5 times the original shaft diameter, etc.) thus holding the rivet  120  in place as both ends  121 ,  122  are larger than the holes  128 ,  142  thus preventing the rivet  120  from being removed from the holes  128 ,  142 . To distinguish between the two ends  121 ,  122  of the rivet  120 , the original head is called the factory head  121  and the deformed end is called the shop head or buck-tail  122 . While this illustrated embodiment includes the rivet  120  for coupling the spring contact assembly  100  to the PCB  124 , other embodiments may include other fasteners besides rivet  120 . 
     Regarding the PCB  124 , it may include a substrate or board body made of FR4 or other suitable material. The PCB  124  includes one or more antenna radiating elements (e.g., electrically-conductive traces, etc.) configured to be operable and resonant in one or more frequency ranges or bands, such as a very high frequency (VHF) band from 136 Megahertz (MHz) to 174 MHz, an ultra high frequency (UHF) band from 380 MHz to 520 MHz, and/or a 700/800 MHz band from 760 MHz to 870 MHz. These frequency bands are examples only as other exemplary embodiments may include a PCB with one or more antenna radiating elements configured to be operable and resonant at other frequencies and/or frequency bands. 
     In operation, the PCB  124  is operable for transmitting and receiving electrical current through a contact port physically attached to an edge of the PCB  124 . Also in this illustrated embodiment, the PCB  124  is configured with a specific or predetermined shape to accommodate the installation of the spring contact assembly  100 . As shown in  FIG. 2 , the PCB  124  includes the notch or cutout area  132  configured to accommodate positioning of the portions  138  of the body  104  about the opposite sides of the PCB  124 . This positioning allows the holes  142  in the body&#39;s portions  138  to be aligned with the hole  130  in the PCB  124 . 
     With continued reference to  FIG. 7 , the body  104  is used to house and control the linear movement of the housing  112 . As shown in  FIG. 7 , the helical coil spring  108  is placed within the open end portions  106  and  114  of the body  104  and housing  112 , respectively, such that the spring  108  is inside the space or void portion between the closed end portion  107  of the body  104  and the closed end portion  113  of the housing  112 . The ring  116  is pressed into the inner walls of the contact body  104  to thereby lock or retain the flanged portion  147  of the housing  112 . The flat extending portions  138  of the body  104  are positioned into the PCB notch  132  such that the holes  142  of the body&#39;s portions  138  line up with the PCB hole  130 . The rivet  120  is then inserted through the holes  142 ,  130 , and then the end  122  of the rivet  120  is deployed (e.g., deformed, etc.) to lock or retain the spring contact assembly  100  onto the PCB  124 . 
       FIGS. 9 through 11  illustrate an exemplary embodiment of an antenna base assembly  250  embodying one or more aspects of the present disclosure. The antenna base assembly  250  may be used as an adaptor to mate an external antenna mount into a feeding point of a radiating element. As disclosed herein, the antenna base assembly  250  provides multiple electrical grounding sources and also maintains a sealed antenna base (e.g., a moisture and/water sealed base, etc.). 
     The antenna base assembly  250  may be used in conjunction with a spring contact assembly, such as the spring contact assembly  100  shown in  FIG. 1 . Additionally, or alternatively, the antenna base assembly  250  may also be used with the multiband antenna assembly  390  shown in  FIG. 12  and/or the multiband antenna assembly  490  shown in  FIGS. 13 and 14 . But the antenna base assembly  250  may also be used with other spring contact assemblies and/or other antenna assemblies than what is disclosed herein. 
     As shown in  FIG. 9 , the antenna base assembly  250  generally includes a bushing  254  (broadly, an electrically-conductive grounding member) and a base  258 . The base  258  includes a seat formed in the bottom thereof for receiving the bushing  254  as shown in  FIG. 11 . Accordingly, the base  258  may also be referred to as a base seat. 
     With continued reference to  FIGS. 9 through 11 , fasteners  262 ,  266  respectively couple the bushing  254  and PCB  224  to the base  258 . The antenna base assembly  250  also includes a sealing member  270  (e.g., an O-ring, gasket, etc.), a contact  200  (e.g., contact pin, spring assembly  100 , etc.), and a housing or radome  274  (e.g., bell or dome shaped plastic housing, etc.). 
     In this illustrated example of  FIGS. 9 through 11 , the bushing  254  is an electrically-conductive ground bushing formed from metal or other suitable electrically-conductive material. The bushing  254  has a cylindrical, annular shape. The bushing  254  is also drilled or tapped with four threaded holes  255  on the upper side to respectively receive the four electrically-conductive fasteners  262  (e.g., metal screws, etc.). The bushing  254  is also configured (e.g., internally threaded, etc.) to mate with an antenna mount. For example,  FIG. 12  illustrates an exemplary antenna mount  396  having a threaded portion  398  onto which the bushing  254  may be threaded. By way of further example, the bushing  254  may be internally threaded to mate with a mobile antenna mount, such as an MBO 3/4″ NMO mount available from Laird Technologies, Inc. As another example, the bushing  254  may be internally threaded for mating to a New Motorola (NMO) antenna mount installed in a roof, trunk, hood, etc. of a vehicle. 
     The fasteners  262 ,  266  may be screws made from solderable material, such as brass, nickel-plated metal, gold-plated metal, tin-plated metal, etc. As shown by  FIG. 11 , the fasteners  262 ,  266  are used to fasten the bushing  254  and PCB  224 , respectively, to the base  258 . Alternatively, other embodiments may include more or less than four fasteners  262 , more or less than two fasteners  266 , and/or different fasteners besides metal screws for fastening the bushing  254  and PCB  224  to the base  258 . 
     The fasteners  262  are also deployed as electrical grounding taps for the PCB  224  in this example. The fasteners  262  are configured for establishing at least a portion of an electrically-conductive grounding pathway from outside of or external to the interior enclosure of the antenna base assembly  250  and which extends into the interior enclosure. As shown by  FIG. 11 , the fasteners  262  extend through the holes  259  in the base  258  with the first end portions or heads of the fasteners  262  within the interior enclosure while the other or second end portions are external to the interior enclosure and inserted into holes of the bushing  254 . Also, the fasteners  262  are disposed internally to or within the perimeter or footprint of the seal  270 , and thus do not breach or otherwise interfere with the sealing providing by the seal  270 . The fasteners  262  also do not breach or otherwise interface with the sealing provided by seals  273  or  278  either. 
     The fasteners  262  may be soldered directly to one or more electrically-conductive portions on the PCB  224  and/or by extending wire leads from the PCB  224  and soldering the wire leads to the ground taps/fasteners  262 . In either case, an electrically-conductive grounding pathway is thus established from the PCB  224  through the fasteners  262  to the bushing  254  and then to the threaded portion of the antenna mount on which the bushing  254  is mounted. 
     The base  258  may be formed from various dielectric materials. By way of example, the base  258  may be an injection molded plastic part configured (e.g., shaped, sized, etc.) to accept the mating of the bushing  254  and the PCB  224 . As shown in  FIG. 11 , the lower portion of the base  258  includes an opening, recess, or seat configured (e.g., sized, shaped, etc.) to receive the bushing  254  therein. The bushing  254  is positionable within the seat of the base  258  such that the bushing  254  is disposed and nests in the seat of the base  258  in a fixed or predetermined orientation. When the bushing  254  is positioned in the seat of the base  258 , the holes  255  of the bushing  254  are aligned with holes  259  through the base  258  for receiving the fasteners  262 . 
     The upper or top portion of the base  258  is shaped to mate with the PCB  224  aligned vertically. When the PCB  224  is positioned on the base  258  as shown in  FIGS. 10 and 11 , holes  267  in the base  258  align with holes  269  in the PCB  224  for receiving the fasteners  266 . 
     The PCB  224  also includes clearances or cutout areas  233  to accommodate and provide sufficient space for the heads of the fasteners  262  as shown in  FIG. 10 . The PCB  224  may also include one or more antenna radiating elements (e.g., electrically-conductive traces, etc.), one or more matching networks, among other components or portions of an antenna system or network, etc. In this illustrated example shown in  FIGS. 10 and 11 , the PCB  224  includes an aluminum transformer balun  282 , which is a part of the antenna matching circuit in this example. 
     In addition, the PCB  224  also includes holes or openings  230  and notches or cutout areas  232 . These PCB holes  230  and notches  232  may be used similar to that described above for the PCB  124  and spring contact assembly  100 . Accordingly, the spring contact assembly  200  shown in  FIG. 9  may be identical in structure and/or operation as the spring contact assembly  100  shown in  FIGS. 1 through 8 . But other embodiments may include a spring contact assembly  200  different than spring contact assembly  100 . 
     With continued reference to  FIG. 9 , the spring contact assembly  200  (e.g., spring loaded metal contact, etc.) includes an end portion  246  (e.g., a contact pin, etc.). The end portion  246  is configured (e.g., sized, shaped, etc.) to be pressed into an opening or thru hole  271  (e.g., tap hole, etc.) through a center or middle of the base  258 , such that a seal or sealed interface  273  ( FIG. 11 ) is formed between the end portion  246  and the sidewalls of the base  258  forming the hole  271 . Accordingly, the seal  273  helps prevent or inhibit the ingress or migration of water, moisture, dust, etc. into the inside of the antenna hull or antenna base assembly  250 . Other embodiments may include one or more sealing members, (e.g., an O-ring, a resiliently compressible elastomeric or foam gasket, caulk, adhesives, other suitable packing or sealing members, integral sealing features, etc.) for substantially sealing the hole  271  in the base, in addition to or as an alternative to the sealing provided by the end portion  246 . 
     In addition to the sealing function in this example, positioning the end portion  246  of the spring contact assembly  200  through the opening  271  also allows it to electrically connect with a center contact or pin (e.g., center contact  397  shown in FIG.  12 , etc.) of an antenna mount when the base assembly  250  is installed onto the antenna mount. In turn, the center contact of the antenna mount may be connected to an inner conductor of a coaxial cable (e.g., coaxial cable  399  also shown in  FIG. 12 , etc.). And, the coaxial cable may be connected to an electronic device, such as a radio device. The spring contact assembly  200  may thus connect or mate the center contact of the antenna mount with a feeding point of a radiating element on the PCB  224 . In operation, the spring contact assembly  200  may thus be operable for transferring electrical current between the center contact of the antenna mount to the antenna radiating element or a network of the antenna assembly that includes the base assembly  250 . 
     In addition to the seal  273  formed between the contact pin  246  and base  258 , the antenna base assembly  250  also includes the sealing member or seal  270 . In this example, the seal  270  is an elastomeric (e.g., rubber, silicone, foam, etc.) O-ring, gasket, or washer configured so as to seal an interface between the housing  274  and base  258 . As shown by  FIG. 11 , the seal  270  is disposed in a recessed channel, groove, or seat  277  of the antenna housing  274 . The seal  270  also abuts or is seated against a shoulder, rim, groove, or seat  275  of the base  258 . In this exemplary manner, the seal  270  substantially seals the interface between the housing  274  and base  258 , which helps prevent or inhibit the ingress or migration of water, moisture, dust, other contaminants, etc. into the interior enclosure defined between the housing  274  and base  258 . Other embodiments may include one or more other sealing members, such as caulk, adhesives, other suitable packing or sealing members, etc. for substantially sealing the interface between the base  258  and housing  274 . In other embodiments, sealing may be achieved by one or more integral sealing features rather than with a separate sealing mechanism. 
     The antenna housing  274  may be coupled to the base  258  by various suitable means, such as mechanical fasteners (e.g., screws, other fastening devices, etc.), a snap-fit connection, ultrasonic welding, solvent welding, heat staking, adhesives, latching, bayonet connections, hook connections, integrated fastening features, etc. within the scope of the present disclosure. When the housing  274  is coupled to the base  258 , the seals  270  and  273  may thus help protect components against ingress of contaminants (e.g., dust, moisture, etc.) into an interior enclosure defined between the housing or cover  274  and the base  258 . In this illustrated example, the antenna housing  274  is a generally bell shaped or dome shaped plastic housing. Alternative embodiments may include a differently configured housing having a different shape (e.g., aerodynamic configuration, etc.), formed from different materials, etc. 
     The antenna base assembly  250  may be threadedly coupled via the threaded portion of the bushing  254  to an external antenna mount. In turn, the external antenna mount may be mounted to a surface of an automobile such as the roof, trunk, hood, etc. In the illustrated example, there is shown a sealing member  278  (e.g., a weather resistant rubber or foam gasket, etc.) on the bottom of the antenna assembly  250 . In some embodiment, the sealing member  278  may be adhesively attached, etc. to the bottom of the base  258  and/or housing  274 . 
     When the antenna base assembly  250  is mounted to the antenna mount, the sealing member  278  is disposed between the mounting surface and the bottom of the antenna base assembly  250 . The sealing member  278  may help prevent damage to the vehicle roof (or other mounting surface). The sealing member  278  also provides further sealing features by helping to seal the mounting area against the ingress or migration of moisture, water, dust, etc. In other embodiments, the housing  274  and/or base seat  254  may be mounted to the antenna mount and/or mounting surface without any gasket  278  between the mounting surface and the antenna base assembly. 
       FIG. 12  illustrates an exemplary multiband antenna assembly  390 , which includes the spring contact assembly  100  ( FIGS. 1-8 ) and antenna base assembly  250  ( FIGS. 9-11 ). As shown in  FIG. 12 , the multiband antenna assembly  390  includes a shock spring  394  above the housing  374  and a whip antenna rod  392  extending thereabove. Also shown in  FIG. 12  is an antenna mount  396 , which generally includes a center contact  397 , a threaded portion  398 , and a coaxial cable  399  for connection with an external device, such as a radio unit, etc. The antenna base assembly  250  may be coupled to the antenna mount  396  by threading the bushing  254  onto the threaded portion  398  of the antenna mount  396 . Also in this example, a printed circuit board (e.g.,  124 ,  224 , etc.) internal to the housing  374  may be connected to the center contact  397  and to the whip antenna rod  392  via two spring contact assemblies  100  along the bottom and top of the printed circuit board. Accordingly, the spring contact assemblies  100  may be used for transferring, transmitting, and/or receiving radio frequency (RF) signals, electrical current, and/or modulated RF signals between an external device (e.g., radio unit, etc.) and the antenna assembly  390 . 
     The multiband antenna assembly  390  may be configured to be operable and resonant in various frequency ranges or bands, including a very high frequency (VHF) band from 136 MHz to 174 MHz, an ultra high frequency (UHF) band from 380 MHz to 520 MHz, a cell/LTE 700/800 MHz band from 764 MHz to 870 MHz. These frequency bands are examples only as other exemplary embodiments of an antenna assembly that includes a spring contact assembly  100  and/or antenna base assembly  250  may be configured to be operable and resonant at other frequencies and/or frequency bands. 
       FIGS. 13 through 19  illustrate another exemplary embodiment of a multiband antenna assembly  490  embodying one or more aspects of the present disclosure. As shown in  FIG. 13 , the multiband antenna assembly  490  includes a base assembly  450  and an aerial whip assembly  492  configured to be coupled or mounted to the base assembly  450 . 
     The base assembly  450  includes a printed circuit board (PCB)  424  and balun  482  configured so as to provide an impedance matching network structure as shown in  FIGS. 17 and 18  and described herein. In this exemplary embodiment, the matching network structure includes the matching PCB portion (e.g., metal laminated dielectric, etc.) comprising a dual double sided trace representing two inductors in parallel. The matching network structure also includes the matching balun portion comprising a matching RF transformer (e.g., metal balun, etc.) representing an inductor with a large mass body and surface. In this illustrated embodiment, two inductors on the PCB  424  are representing a single inductor, and the open space is used to control the capacitances interaction with the balun  482  by limiting the amount of surface area of the PCB trace that is coupling or bonding to the balun  482 . As most of the capacitive area is within the front and back traces on the PCB  424 , typically the wider the opening the less the coupling capacitances, this technique is used as means to fine tweak the matching circuit. 
     The base assembly  450  also includes upper and lower contact pins  400  and a base ring portion or bushing  454 . The contact pins  400  may comprise metal pogo pin devices and/or the spring contact assemblies  100  disclosed herein. In operation, the contact pins  400  conduct the electrical current through the PCB  424  and balun structure  482  towards the aerial whip assembly  492 . The base ring portion  454  comprises an electrically-conductive threaded nut (e.g., brass or other metal, etc.) threadedly attached to the base or housing cap  458  (e.g., thermoplastic cap, etc.). The base ring portion  454  may be used as a mounting part for mounting the antenna assembly  490  to an external mount port. In operation, the base ring portion  454  conducts the ground portion of the current flow into the antenna structure. The multiband band assembly  490  may be coupled to an antenna mount (e.g., NMO antenna mount, etc.) in a similar manner as the antenna assembly  390  is mounted to the mount  396  shown in  FIG. 12 . 
     With continued reference to  FIGS. 13 and 15 , the multiband antenna assembly  490  may further include a hermetically sealed housing  474  coupled to the base  458 . The aerial whip assembly  492  includes a shock absorbing spring  494  top mounted by first and second linear elements  501 ,  503 , shown as metal (e.g., stainless steel, etc.) rods. A radio wave impedance matching helical spring (or phasing coil) (shown in  FIG. 19 ) is disposed within a housing  505 . The radio wave impedance matching helical spring (or phasing coil) electrically connects and linearly joins the first and second metal rods  501 ,  503  (broadly, linear elements) with a separation or spaced distance between the two rods  501 ,  503 . An aerial radio waves defusing member  507  is coupled (e.g., via a press fit, etc.) to an upper portion of the top linearly mounted rod. For example, the top linearly mounted rod may be pressed into an opening or hole in an aerial radio waves defusing metal ball (e.g., stainless steel ball, etc.). 
       FIG. 17  includes a circuit diagram graphically representing the matching network provided by the base assembly  450  and graphically representing components of the aerial whip assembly  492 .  FIG. 18  includes a circuit diagram graphically representing the full matching network shown in  FIG. 17  provided by the base assembly  450 , including the concentric capacitance (C 2 ) between first and second inductors (L 1  and L 2 ) and the capacitance (C 1 ) from ground. The capacitance (C 1 ) is created between the base ring portion  458  (e.g., brass ring, etc.) and the base of the lower contact pin  400 . As shown by  FIGS. 17 and 18 , the matching network includes two primary inductors in parallel L 1  and L 2  in which both inductors are concentrically capacitive to each other thereby forming C 2  capacitance. The first inductor L 1  is provided by an electrically-conductive portion of the PCB  424 , such as a metal area (e.g., copper trace, etc.) on the PCB  424 . The second inductor L 2  is provided by the balun  482 . The capacitance C 2  is provided by a dielectric or non-conductive portion  425  of the PCB  424 , such as a metal-free area of the PCB  424  where the metal trace material has been etched or otherwise removed from the PCB  424 . The PCB portion  425  is between the metal (first inductor L 1 ) area on the PCB  424  and the balun  482  (second inductor L 2 ). In  FIG. 17 , AI represents antenna inductance, AC represents antenna capacitance, RR represent radiation resistance, LR represents loss resistance, ZA represents antenna impedance, and ZS represents source impedance. 
     In this example, the bulk circuit of the matching network represents an actual ¼ wave radiator for the upper 800 MHz frequency band, meanwhile the matching network serves the purpose of impedance matching for the middle and low frequency bands. The characteristics of the concentric capacitances C 2  between both inductors L 1  and L 2  and the capacitance C 1  from ground comprises the full matching circuit as shown in  FIG. 18 . An advantage or benefit of using the balun  482  for inductance L 2  is the increased width of the upper frequency band. This is because the larger the surface area and the mass of the balun the wider the frequency band width. The base ring portion  458  controls the shunt capacitances C 1  with respect to ground and controls the resonant frequency mainly at the higher frequency range. 
     During operation of the antenna assembly  490 , the matching network (L 1 , L 2 , C 1  and C 2 ) together with L 3  (bottom rod inductance) form a ½ wave radiator for 800 MHz and 5/16 wave radiator for UHF. A ¼ wave radiator for VHF is formed by the elements beginning with the source at the base ring portion  458  up to the metal ball  507  as shown in  FIG. 19 . With continued reference to  FIG. 17 , L 4  (phasing coil inductance) functions as phasing coil for the UHF and 800 MHz. The dimension of L 5  (top rod inductance) represents a ½ wave element for 800 MHz and ¼ wave for UHF. With the presence of L 5 , the antenna assembly  490  is operable and works at 800 MHz as a stacked ½ wave antenna which corresponds to the elevation pattern. 
     The multiband antenna assembly  490  may also include various components and elements similar to that described above for the base assembly  250  and shown in  FIG. 9 . For example, and with reference to  FIG. 13 , the multiband antenna assembly  490  may include spring contact assemblies  400 , rivets or pins, a PCB  424  with notches or cutout areas  432  and clearances or cutout areas  433 , fasteners  462  and  466 , sealing member  470 , and sealing member  478  similar to the corresponding features of the base assembly  250 . 
     Also shown in  FIG. 13  are fasteners  509  (e.g., screws, etc.) for attaching the housing  474  to the base  458 . The fasteners  509  pass through holes in the base  458  and into holes in the housing  474 , which holes can be seen in the base  258  and housing  274  shown in  FIG. 9 . A sealing member  511  (e.g., O-ring, etc.) is shown that may be used to seal the interface between the base assembly  450  and the aerial whip assembly  492 . The aerial whip assembly  492  may be mounted to the base assembly  450  via the threaded, e.g., metal, upper feed conductor  513 . A label  515  may be positioned (e.g., adhesively attached to, etc.) within the bottom of the base  458 , for example, to provide information (e.g., model, date, etc.) of the antenna assembly  490 . 
       FIG. 19  provides dimensions in millimeters and inches in brackets for the multiband antenna assembly  490  for purpose of illustration only according to an exemplary embodiment. By way of further example, this exemplary embodiment of the multiband antenna assembly  490  may be used as a commercial heavy duty vehicular broadband omnidirectional mobile antenna, that is vertically polarized and 50 ohm, with a VSWR&lt;2.5:1 at 17 feet of RG58A/U coaxial cable end, 100 Watts, less than 20 inches in height, a 2.5 inch diameter base, and operable for covering frequency bands of VHF 136-174 MHz with unity gain, UHF 380-520 MHz with a gain of 3 dBi (decibels relative to isotropic), and 760-870 MHz with a gain of 3 dBi. The multiband antenna assembly  490  may be mounted on a flat or contoured surface of a thin metallic material, such as with a standard NMO mount on the center of a vehicle with sufficient metallic ground of two feet by two feet square or more. 
       FIGS. 20 through 22  provide analysis results measured for an antenna assembly having features and dimensions as shown in  FIG. 19 . These analysis results shown in  FIGS. 20 through 22  are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIG. 20  is an exemplary line graph illustrating voltage standing wave ratio (VSWR) versus frequency in megahertz (MHZ) measured for the antenna assembly shown in  FIG. 19 . Generally,  FIG. 20  shows that this antenna assembly has a relatively good VSWR of less than 2.5 for frequencies falling within the very high frequency (VHF) band from 136 MHz to 174 MHz, the ultra high frequency (UHF) band from 380 MHz to 520 MHz, and the cell/LTE 700/800 MHz band from 760 MHz to 870 MHz. These frequency bands are examples only as other exemplary embodiments of an antenna assembly may be configured to be operable and resonant at other frequencies and/or frequency bands. 
       FIGS. 21A ,  21 B, and  21 C illustrate radiation azimuth field radiation patterns measured for the antenna assembly shown in  FIG. 19  at frequencies of 156 MHz, 450 MHz, and 810 MHz.  FIGS. 22A and 22B  illustrate elevation field radiation patterns measured for the antenna assembly shown in  FIG. 19  at frequencies of 450 MHz and 810 MHz. Generally,  FIGS. 21A through 22B  show that the antenna assembly has good omnidirectional radiation patterns at these frequencies. 
     The multiband antenna  490  may include one or more spring contact assemblies  100  ( FIGS. 1-8 ) and/or a sealed base assembly  250  ( FIGS. 9-11 ). Accordingly, an exemplary embodiment of the multiband antenna assembly  490  includes one or more elements or features of the spring contact assembly  100  and/or sealed antenna base assembly  250 . In other embodiments, a multiband antenna assembly may include matching network structure of the base assembly  450  without having any spring contact assemblies or a sealed base assembly. 
     Accordingly, the inventors have disclosed exemplary embodiments of multiband antenna assemblies having matching networks that may provide one or more (but not necessarily any or all) of the following advantages. For example, disclosed exemplary embodiments make it possible to achieve high gain and broad bandwidth coverage in a relatively small and sleek overall package. In contrast, conventional multiband antenna matching networks restrict the achievement of both broad bandwidth and high gain due to a tradeoff of losing gain on some parts of the band coverage. Traditionally, much larger aerial structures and larger matching network assemblies have been used to attempt to obtain a fair combination of broad bandwidth and high gain. 
     In exemplary embodiments, the inventors have struck a balance of antenna aesthetic look and performance with a single full spectrum antenna operable across all of the most popular U.S. public safety frequencies such as the VHF frequencies from 136-174 MHz, the UHF frequencies from 380-520 MHz, and frequencies within the Cell/LTE 700/800 MHz in a package less than 20 inches in height and with a small base as a mechanical support on a standard vehicle for public safety wireless applications. In an exemplary embodiment, a unique impedance matching network is operable simultaneously with a wide band frequency spectrum including VHF 136-174 MHz, UHF 380-520 MHz, and Cell/LTE 700/800 MHz, which may supplement a single aerial structure for broadband coverage. 
     Exemplary embodiments may be operable on a four feet by four feet ground plane and/or with continuous power handling at 100 Watts for all frequency bands. Exemplary embodiments may provide multiple radio frequency broadband matching networks combined with no discrete components. Exemplary embodiments may include a low visible and stylish enclosed phasing coil and rod length with overall length maximum of 20 inches high. Exemplary embodiments may be omnidirectional, vertically polarized, and have simultaneous standard electrical lengths of ¼ wavelength for VHF, ⅝ wavelength for UHF, and ⅝ over ⅝ wavelength for Cell/LTE 700/800 MHz band. Exemplary embodiments may be operable with unity gain for VHF 136-174 MHz and with 3 dBi gain for UHF 380-520 MHz and Cell/LTE 700/800 MHz. Exemplary embodiments may provide multiple radio frequency broadband matching networks using open stub matching technique and in conjunction with a 0.125 inch thick Printed Circuit Board (PCB) with both approximately 3 inches in length and overall length of the antenna is approximately 20 inches tall. Exemplary embodiments may be configured to mount on a 4 feet by 4 feet ground plane and be attached with 17 feet of RG58A/U coaxial cable to achieve what a radio will see VSWR&lt;2.5:1 on all frequency bands of VHF 136-174 MHz, UHF 380-520 MHz, and Cell/LTE 700/800 MHz. 
     Exemplary spring contact assemblies disclosed herein were developed by the inventors in an effort to an effective pressure electrical/mechanical connection point that deploys a minimal (or at least reduced) surface area variation, ease of manufacturing, electrical stability, and/or better (or at least satisfactory) structural strength as compared to some conventional contact assemblies. The inventors hereof recognized that some conventional contact assemblies were associated with one or more of the following drawbacks, such as an inability to handle high electrical current and power requirements, non-uniform contact area and path produced instable repeatability for electrical current flow, operator skill dependent, insufficient structural strength, production reproducibility issues eliminated the fixed tune options on higher frequency antenna models, time consuming assembly process, and/or very difficult to automate at a mass production level. 
     Accordingly, the inventors have disclosed exemplary embodiments of spring contact assemblies that may provide one or more (but not necessarily any) of the following advantages. For example, an exemplary embodiment of the inventors&#39; spring contact assembly may provide good electrical contact via a rivet, may provide a strong connection to the PCB board material (e.g., FR4, etc.) without concern for cracking of non-existent solder, and/or may provide good repeatability in manufacture and a fixed tune design such that the antenna assemblies do not need to be tuned on the assembly floor during manufacture. By way of further example, an exemplary embodiment of the inventors&#39; spring contact assembly may have a fixed shape that minimizes or reduces electrical RF current flow through the body of the conductive spring contact assembly and surface current flow variation/transformation when repeated in mass production levels. An exemplary embodiment of the inventors&#39; spring contact assembly may provide a solderless interconnection that helps eliminate (or at least reduce) workmanship related variations. An exemplary embodiment of the inventors&#39; spring contact assembly may have a stronger structure to minimize or reduce the possibility of disengagement from the PCB. An exemplary embodiment of the inventors&#39; spring contact assembly may provide a two sided sandwich lock to minimize or reduce copper trace peeling effects due to vibrations. An exemplary embodiment of the inventors&#39; spring contact assembly may be configured with a rivet fastened lock that constrains the structure to a stronger FR4 material of the board of the PCB and not to the copper trace. An exemplary embodiment of the inventors&#39; spring contact assembly may be configured with a spring contact feature that can handle up to five hundred percent more impact and loading forces than a conventional soldered type pushpin. An exemplary embodiment of the inventors&#39; spring contact assembly may contain a heavier section of materials allowing higher electrical current to run through, which, in turn would allow higher power handling. An exemplary embodiment of the inventors&#39; spring contact assembly may not require any additional mechanical support from the hull body of the containing unit. An exemplary embodiment of the inventors&#39; spring contact assembly may allow for a faster assembly and easier automation possibilities. It should be noted that the advantages disclosed herein are exemplary only and not limiting, as exemplary embodiments of the present disclosure may achieve all, some, or none of the advantages disclosed herein. 
     The inventors hereof have also recognized conventional antenna base assemblies provide electrical grounding but suffered many problems associated with poor seals and/or breached seals, which made the antenna prone to failure. For example, some conventional antenna base assemblies are associated with a shorter life span on shelf or in the field, a degraded performance by time caused by internal component corrosion, an open antenna hull allowing moisture condensation inside the antenna associated with temperature variation, imminent failure if mounted high or poorly, allow water migration from rain hydro pressure to seep into the antenna, imminent failure if the base gasket fails, and/or allowed only one grounding tap to feed the PCB. 
     Accordingly, the inventors have disclosed exemplary embodiments of sealed antenna base assemblies that may provide one or more (but not necessarily any) of the following advantages. For example, an exemplary embodiment of the inventors&#39; sealed antenna base assembly may provide more than one grounding tap, may maintain long term performance with minimized (or at least reduced) corrosion of internal components of an antenna unit, may provide a stronger uphold against moisture and water migration into the inside the antenna unit, may minimize or reduce moisture condensation due to thermal variation, may significantly reduce the chance for failures if mounted high or poorly, may double the sealing defense to insure no failures if the base gasket fails, may significantly increase storage shelf life and infield life span, and/or enabled the antenna structure to meet higher standards such as Ingress Protection ratings. It should be noted that the advantages disclosed herein are exemplary only and not limiting, as exemplary embodiments of the present disclosure may achieve all, some, or none of the advantages disclosed herein. 
     Numerical dimensions and values are provided herein for illustrative purposes only. The particular dimensions and values provided are not intended to limit the scope of the present disclosure. 
     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 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. 
     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. 
     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 (e.g., different materials may be used, etc.) 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. 
     The disclosure herein of particular values and particular ranges of values for given parameters (e.g., frequencies, bandwidths, etc.) 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. 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. 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. 
     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 invention. Individual elements 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 invention, and all such modifications are intended to be included within the scope of the invention.