Patent Publication Number: US-11050142-B2

Title: Coupled antenna structure

Description:
PRIORITY 
     This application is a continuation-in-part of and claims priority to co-owned and co-pending U.S. patent application Ser. No. 13/794,468 filed Mar. 11, 2013 of the same title, which is incorporated herein by reference in its entirety. 
    
    
     COPYRIGHT 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     1. Technological Field 
     The present disclosure relates generally to an antenna apparatus for use in electronic devices such as wireless or portable radio devices, and more particularly in one exemplary aspect to an antenna apparatus for use within a metal device or a device with a metallic surface, and methods of utilizing the same. 
     2. Description of Related Technology 
     Antennas are commonly found in most modern radio devices, such as mobile computers, portable navigation devices, mobile phones, smartphones, personal digital assistants (PDAs), or other personal communication devices (PCD). Typically, these antennas comprise a planar radiating element with a ground plane that is generally parallel to the planar radiating element. The planar radiating element and the ground plane are typically connected to one another via a short-circuit conductor in order to achieve the desired impedance matching for the antenna. The structure is configured so that it functions as a resonator at the desired operating frequency. Typically, these internal antennas are located on a printed circuit board (PCB) of the radio device inside a plastic enclosure that permits propagation of radio frequency waves to and from the antenna(s). 
     More recently, it has been desirable for these radio devices to include a metal body or an external metallic surface. A metal body or an external metallic surface may be used for any number of reasons including, for example, providing aesthetic benefits such as producing a pleasing look and feel for the underlying radio device. However, the use of a metallic enclosure creates new challenges for radio frequency (RF) antenna implementations. Typical prior art antenna solutions are often inadequate for use with metallic housings and/or external metallic surfaces. This is due to the fact that the metal housing and/or external metallic surface of the radio device acts as an RF shield which degrades antenna performance, particularly when the antenna is required to operate in several frequency bands. 
     Accordingly, there is a salient need for an antenna solution for use with, for example, a portable radio device having a small form factor metal body and/or external metallic surface that provides for improved antenna performance. 
     SUMMARY 
     The present disclosure satisfies the foregoing needs by providing, inter alia, a space-efficient antenna apparatus for use within a metal housing, and methods of tuning and use thereof. 
     In a first aspect, a coupled antenna apparatus is disclosed. In one embodiment, the coupled antenna apparatus includes a first radiator element having a conductive ring-like structure. The conductive ring-like structure includes one or more protruding conductive portions that are configured to optimize one or more operating parameters of the coupled antenna apparatus. 
     In an alternative embodiments, the coupled antenna apparatus includes a first radiator element having a closed structure; one or more second radiator elements that are disposed proximate to the first radiator element; and one or more third radiator elements that are disposed proximate to the one or more second radiator elements. The closed structure includes one or more protruding conductive portions that are configured to optimize one or more operating parameters of the coupled antenna apparatus. 
     In a second aspect, a satellite positioning-enabled wrist-wearable electronic wireless is disclosed. In one embodiment, the satellite positioning-enabled wireless apparatus includes a wireless receiver configured to at least receive satellite positioning signals and an antenna apparatus in signal communication with the receiver. The antenna apparatus includes an outer radiator element having a closed loop structure with one or more protruding conductive portions that are configured to optimize one or more operating parameters of the antenna apparatus. 
     Further features of the present disclosure, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, objectives, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein: 
         FIG. 1  is a schematic diagram detailing the antenna apparatus according to one embodiment of the disclosure; 
         FIG. 2A  is a perspective view of the underside of one embodiment of the coupled antenna apparatus of a radio device in accordance with the principles of the present disclosure; 
         FIG. 2B  is a perspective of the coupled antenna apparatus of  FIG. 2A  configured according to one embodiment of the present disclosure; 
         FIG. 2C  is an exploded view of the coupled antenna apparatus of  FIGS. 2A-2B  detailing various components of the coupled antenna apparatus in accordance with the principles of the present disclosure; 
         FIG. 3A  is a perspective view of the underside of a second embodiment of a coupled antenna apparatus of a radio device in accordance with the principles of the present disclosure; 
         FIG. 3B  is a perspective of the coupled antenna apparatus of  FIG. 3A  configured according to a second embodiment of the present disclosure; 
         FIG. 3C  is an exploded view of the coupled antenna apparatus of  FIGS. 3A-3B  detailing various components of a coupled antenna apparatus in accordance with the principles of the present disclosure; 
         FIG. 4A  is a perspective view of the underside of a third embodiment of a coupled antenna apparatus of a radio device in accordance with the principles of the present disclosure; 
         FIG. 4B  is a perspective of the coupled antenna apparatus of  FIG. 4A  configured according to a third embodiment of the present disclosure; 
         FIG. 4C  is an exploded view of the coupled antenna apparatus of  FIGS. 4A-4B  detailing various components of a coupled antenna apparatus in accordance with the principles of the present disclosure; 
         FIG. 5A  is a perspective view of the underside of a fourth embodiment of a coupled antenna apparatus of a radio device in accordance with the principles of the present disclosure; 
         FIG. 5B  is a perspective of the coupled antenna apparatus of  FIG. 5A  configured according to a fourth embodiment of the present disclosure; 
         FIG. 5C  is an exploded view of the coupled antenna apparatus of  FIGS. 5A-5B  detailing various components of a coupled antenna apparatus in accordance with the principles of the present disclosure; 
         FIG. 6A  is a top side view of an asymmetrical outer ring element useful in the coupled antenna apparatus of  FIGS. 2A-5C  in accordance with the principles of the present disclosure; 
         FIG. 6B  is a top side view of a symmetrical outer ring element useful in the coupled antenna apparatus of  FIGS. 2A-5C  in accordance with the principles of the present disclosure; 
         FIG. 7  is a plot of return loss as a function of frequency utilizing an exemplary coupled antenna apparatus embodiment constructed in accordance with the principles of the present disclosure; 
         FIG. 8  is a plot illustrating (i) efficiency (dB); (ii) axis ratio (dB); (iii) right hand circular polarized (RHCP) signal gain; (iv) left hand circular polarized (LHCP) signal gain; and (v) efficiency (%) as a function of frequency for an exemplary coupled antenna apparatus constructed in accordance with the principles of the present disclosure; 
         FIG. 9  is a plot illustrating measured SNR (signal to noise ratio) for an exemplary coupled antenna apparatus constructed in accordance with the principles of the present disclosure; 
         FIG. 10  is a plot illustrating RHCP signal gain as a function of frequency for the asymmetrical outer ring element of  FIG. 6A  utilized in conjunction with the coupled antenna apparatus of  FIGS. 2A-5C  manufactured in accordance with the principles of the present disclosure; 
         FIG. 11  is a plot illustrating LHCP signal gain as a function of frequency for the asymmetrical outer ring element of  FIG. 6A  utilized in conjunction with the coupled antenna apparatus of  FIGS. 2A-5C  manufactured in accordance with the principles of the present disclosure; 
         FIG. 12  is a plot illustrating axial ratio (AR) gain as a function of frequency for the asymmetrical outer ring element of  FIG. 6A  utilized in conjunction with the coupled antenna apparatus of  FIGS. 2A-5C  manufactured in accordance with the principles of the present disclosure; 
         FIG. 13  is a plot of return loss as a function of frequency for the symmetrical outer ring element of  FIG. 6B  utilized in conjunction with the coupled antenna apparatus of  FIGS. 2A-5C  manufactured in accordance with the principles of the present disclosure; 
         FIG. 14  shows an embodiment of a coupled antenna apparatus; 
         FIG. 15A  is a perspective view of the underside of a coupled antenna apparatus of a wrist-wearable electronic device according to the invention; 
         FIG. 15B  is a perspective of the coupled antenna apparatus of  FIG. 15A ; 
         FIG. 15C  is an exploded view of the coupled antenna apparatus of  FIGS. 15A-15B  detailing various components of a coupled antenna apparatus; 
         FIGS. 16A and 16B  show embodiments of a coupled antenna apparatus according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference is now made to the drawings wherein like numerals refer to like parts throughout. 
     As used herein, the terms “antenna”, and “antenna assembly” refer without limitation to any system that incorporates a single element, multiple elements, or one or more arrays of elements that receive/transmit and/or propagate one or more frequency bands of electromagnetic radiation. The radiation may be of numerous types, e.g., microwave, millimeter wave, radio frequency, digital modulated, analog, analog/digital encoded, digitally encoded millimeter wave energy, or the like. The energy may be transmitted from location to another location, using, or more repeater links, and one or more locations may be mobile, stationary, or fixed to a location on earth such as a base station. 
     As used herein, the terms “board” and “substrate” refer generally and without limitation to any substantially planar or curved surface or component upon which other components can be disposed. For example, a substrate may comprise a single or multi-layered printed circuit board (e.g., FR4), a semi-conductive die or wafer, or even a surface of a housing or other device component, and may be substantially rigid or alternatively at least somewhat flexible. 
     The terms “frequency range”, and “frequency band” refer without limitation to any frequency range for communicating signals. Such signals may be communicated pursuant to one or more standards or wireless air interfaces. 
     As used herein, the terms “portable device”, “mobile device”, “client device”, and “computing device”, include, but are not limited to, personal computers (PCs) and minicomputers, whether desktop, laptop, or otherwise, set-top boxes, personal digital assistants (PDAs), handheld computers, personal communicators, tablet computers, portable navigation aids, J2ME equipped devices, cellular telephones, smartphones, tablet computers, personal integrated communication or entertainment devices, portable navigation devices, or literally any other device capable of processing data. 
     Furthermore, as used herein, the terms “radiator,” “radiating plane,” and “radiating element” refer without limitation to an element that can function as part of a system that receives and/or transmits radio-frequency electromagnetic radiation; e.g., an antenna. Hence, an exemplary radiator may receive electromagnetic radiation, transmit electromagnetic radiation, or both. 
     The terms “feed”, and “RF feed” refer without limitation to any energy conductor and coupling element(s) that can transfer energy, transform impedance, enhance performance characteristics, and conform impedance properties between an incoming/outgoing RF energy signals to that of one or more connective elements, such as for example a radiator. 
     As used herein, the terms “top”, “bottom”, “side”, “up”, “down”, “left”, “right”, and the like merely connote a relative position or geometry of one component to another, and in no way connote an absolute frame of reference or any required orientation. For example, a “top” portion of a component may actually reside below a “bottom” portion when the component is mounted to another device (e.g., to the underside of a PCB). 
     As used herein, the term “wireless” means any wireless signal, data, communication, or other interface including without limitation Wi-Fi, Bluetooth, 3G (e.g., 3GPP, 3GPP2, and UMTS), HSDPA/HSUPA, TDMA, CDMA (e.g., IS-95A, WCDMA, etc.), FHSS, DSSS, GSM, PAN/802.15, WiMAX (802.16), 802.20, narrowband/FDMA, OFDM, PCS/DCS, Long Term Evolution (LTE) or LTE-Advanced (LTE-A), analog cellular, CDPD, satellite systems such as GPS and GLONASS, and millimeter wave or microwave systems. 
     Overview 
     In one salient aspect, the present disclosure provides improved antenna apparatus and methods of use and tuning. In one exemplary embodiment, the solution of the present disclosure is particularly adapted for small form-factor, metal-encased applications that utilize satellite wireless links (e g, GPS), and uses an electromagnetic (e.g., capacitive, in one embodiment) feeding method that includes one or more separate feed elements that are not galvanically connected to a radiating element of the antenna. In addition, certain implementations of the antenna apparatus offer the capability to carry more than one operating band for the antenna. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Detailed descriptions of the various embodiments and variants of the apparatus and methods of the disclosure are now provided. While primarily discussed in the context of portable radio devices, such as wristwatches, the various apparatus and methodologies discussed herein are not so limited. In fact, many of the apparatus and methodologies described herein are useful in any number of devices, including both mobile and fixed devices that can benefit from the coupled antenna apparatus and methodologies described herein. 
     Furthermore, while the embodiments of the coupled antenna apparatus of  FIGS. 1-6B  are discussed primarily in the context of operation within the GPS wireless spectrum, the present disclosure is not so limited. In fact, the antenna apparatus of  FIGS. 1-6B  are useful in any number of operating bands including, without limitation, the operating bands for: GLONASS, Wi-Fi, Bluetooth, 3G (e.g., 3GPP, 3GPP2, and UMTS), HSDPA/HSUPA, TDMA, CDMA (e.g., IS-95A, WCDMA, etc.), FESS, DSSS, GSM, PAN/802.15, WiMAX (802.16), 802.20, narrowband/FDMA, OFDM, PCS/DCS, Long Term Evolution (LTE) or LTE-Advanced (LTE-A), analog cellular, and CDPD. 
     Exemplary Antenna Apparatus 
     Referring now to  FIG. 1 , one exemplary embodiment of a coupled antenna apparatus  100  is shown and described in detail. As shown in  FIG. 1 , the coupled antenna apparatus  100  includes three (3) main antenna elements, including an outer element  102  that is disposed adjacent to a middle radiator element  104  and an inside feed element  106 . The radiator element  104 , feed element  106 , and the outer element  102  are not in galvanic connection with one another, and instead are capacitively coupled as discussed below. The outer element  102  is further configured to act as the primary radiator element for the antenna apparatus  100 . The width of the outer element and the distance of the outer element from the middle element are selected based on specific antenna design requirements, including (i) the frequency operating band of interest, and (ii) the operating bandwidth, exemplary values of which can be readily implemented by one of ordinary skill given the present disclosure. 
     As shown in  FIG. 1 , the middle radiator element of the coupled antenna apparatus is disposed adjacent the outer element, and is separated from the outer element by a gap distance  120 . For example, in one implementation, a distance of 0.2-1 mm is used, but it will be appreciated that this value may vary depending on implementation and operating frequency. Moreover, the coupling strength can be adjusted by adjusting the gap distance and by adjusting the overlapping area of the outer and middle radiator elements and by the total area of both the outer and middle radiator elements. The gap  120  enables the tuning of, inter alia, the antenna resonant frequency, bandwidth, and radiation efficiency. The middle radiator element further comprises two parts  104 ( a ) and  104 ( b ). The first part  104  a is the main coupling element, and the second part  104   b  is left floating and not otherwise connected to the antenna structure. The second part  104   b  can, for example, be left in the structure if for some mechanical reason the middle element is formed as a larger part, and only a shorter portion of it is needed as a coupling element. Disposed at one end of the middle radiator element part  104 ( a ) is a short circuit point  110  for connecting the middle radiator element  104  to ground. The short circuit point  110  is in the illustrated embodiment located at a predefined distance  122  (typically 1-5 mm in the exemplary implementations, but may vary depending on implementation and operating frequency) from the inside feed element  106 . The placement of the short circuit point  110  determines in part the resonant frequency of the coupled antenna apparatus  100 . Part  104 ( a ) is connected to part  104 ( b ), wherein part  104 ( b ) forms the complete middle radiator (ring). 
       FIG. 1  also illustrates an inner feed element  106  comprised of a ground point  114 , as well as a galvanically connected feed point  116 . The inner feed element  106  is disposed at a distance  124  from the middle radiator element  104 . Furthermore, the placement and positioning of the ground point  114  with respect to the feed point  116  determines in part the resonant frequency of the coupled antenna apparatus  100 . It is noted that the ground point of the feed element is primarily used for feed point impedance matching. In one implementation, the feed element forms and IFA-type (Inverted F Antenna) structure of the type known in the art, and impedance adjustment of such an element is well known by ordinary antenna designers, and accordingly not described further herein. A typical distance between the feed and ground points is on the order of 1-5 mm, but this may vary depending on frequency and application. 
     Moreover, it will be appreciated that the ground point may be eliminated if desired, such as by placing a shunt inductor onto the feed line. The placement of the feed point  116  and ground points  110  and  114  greatly affect the right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) isolation gains, as discussed below. As a brief aside, GPS and most satellite navigation transmissions are RHCP; satellites transmit the RHCP signal since it is found to be less affected by atmospheric signal deformation and loss than for example linearly polarized signals. Thus, any receiving antenna should have the same polarization as the transmitting satellite. Significant signal loss will occur (on the order of tens of dB) if the receiving device antenna is dominantly LHCP polarized. In addition the satellite signal will change polarization from RHCP to LHCP each time when it is reflected from an object, for example the earth&#39;s surface or a building. Signals that are reflected once near the receiving unit have almost the same amplitude but a small time delay and LHCP, as compared to directly received RHCP signals. These reflected signals are especially harmful to GPS receiver sensitivity, and thus it is preferred to use antennas in which LHCP gain is at minimum 5 dB to 10 dB lower than the RHCP gain. 
     For example, in the exemplary illustration, the feed and ground line placements are chosen for the RCHP gain to dominate and the LHCP gain to be suppressed (so as to enhance sensitivity to GPS circularly polarized signals). However, if the feed and ground lines placements were reversed, the “handedness” of the antenna apparatus  100  would be reversed, thereby creating a dominant LHCP gain, while suppressing RHCP gain. To this end, the present disclosure also contemplates in certain implementations the ability to switch or reconfigure the antenna e.g., on the fly, such as via a hardware or software switch, or manually, so as to switch the aforementioned “handedness” as desired for the particular use or application. It may for example be desired to operate in conjunction with a LHCP source, or receive the aforementioned reflected signals. 
     Accordingly, while not illustrated, the present disclosure contemplates: (i) portable or other devices having both RHCP-dominant and LHCP dominant antennas that can operate substantially independent of one another, and (ii) variants wherein the receiver can switch between the two, depending on the polarization of the signals being received. 
     The coupled antenna apparatus  100  of  FIG. 1  thus comprises a stacked configuration comprising an outer element  102 , a middle radiator element  104  disposed internal to the outer element, and an inside feed element  106 . It is noted that one middle radiator element is enough to excite on the desired operating frequency. However, for multiband operation, additional middle elements and feed elements can be added. If, as one example, a 2.4 GHz ISM band is needed, then the same outer radiator can be fed by another set of middle element and feed elements. The inside feed element is further configured to be galvanically coupled with a feed point  116 , and the middle radiator element is configured to be capacitively coupled to the inside feed element. The outer element  102  is configured to act as the final antenna radiator and is further configured to be capacitively coupled to the middle radiator element. In the present embodiment, the dimensions of the outer element  102 , and the feed elements  104  and  106  are selected to achieve a desired performance. Specifically, if the elements (outer, middle, inner) are measured as separated from each other, none of them would be independently tuned to a value close to the desired operating frequency. When the three elements are coupled together, however, they form a single radiator package that creates resonances in the desired operating frequency (or frequencies). A relatively wide bandwidth of a single resonance is achieved due to the physical size of the antenna, and use of low dielectric mediums like plastic. One salient benefit of this structure in the exemplary context of satellite navigation applications is that there is a typical interest in covering both GPS and GLONASS navigation systems with same antenna, i.e., 1575-1610 MHz at minimum, which the exemplary implementation allows. 
     It will be appreciated by those skilled in the art given the present disclosure that the above dimensions correspond to one particular antenna/device embodiment, and are configured based on a specific implementation and are hence merely illustrative of the broader principles of the present disclosure. The distances  120 ,  122  and  124  are further selected to achieve desired impedance matching for the coupled antenna apparatus  100 . For example, due to multiple elements that may be adjusted, it is possible to tune the resulting antenna to a desired operating frequency even if unit size (antenna size) varies largely. For instance, the top (outer) element size can be expanded to say 100 by 60 mm, and by adjusting the couplings between the elements, the correct tuning and matching can advantageously be achieved. 
     Portable Radio Device Configurations 
     Referring now to  FIGS. 2A-5C , four (4) exemplary embodiments of a portable radio device comprising a coupled antenna apparatus configured in accordance with the principles of the present disclosure is shown and described. In addition, various implementations of the outer element are shown with respect to  FIGS. 6A-6B  that can be utilized in conjunction with the coupled antenna apparatus embodiments illustrated in  FIGS. 2A-5C  in order to further enable optimization of the various antenna operating characteristics. In some embodiments, one or more components of the antenna apparatus  100  of  FIG. 1  are formed using a metal covered plastic body, fabricated by any suitable manufacturing method (such as, for example an exemplary laser direct structuring (“LDS”) manufacturing process, or even a printing process such as that referenced below). 
     Recent advances in LDS antenna manufacturing processes have enabled the construction of antennas directly onto an otherwise non-conductive surface (e.g., onto thermoplastic material that is doped with a metal additive). The doped metal additive is subsequently activated by means of a laser. LDS enables the construction of antennas onto more complex three-dimensional (3D) geometries. For example, in various typical smartphones, wristwatch and other mobile device applications, the underlying device housing and/or other antenna components on which the antenna may be disposed, is manufactured using an LDS polymer using standard injection molding processes. A laser is then used to activate areas of the (thermoplastic) material that are then subsequently plated. Typically an electrolytic copper bath followed by successive additive layers such as nickel or gold are then added to complete the construction of the antenna. 
     Additionally, pad printing, conductive ink printing, FPC, sheet metal, PCB processes may be used consistent with the disclosure. It will be appreciated that various features of the present disclosure are advantageously not tied to any particular manufacturing technology, and hence can be broadly used with any number of the foregoing. While some technologies inherently have limitations on making e.g., 3D-formed radiators, and adjusting gaps between elements, the inventive antenna structure can be formed by using any sort of conductive materials and processes. 
     However, while the use of LDS is exemplary, other implementations may be used to manufacture the coupled antenna apparatus such as via the use of a flexible printed circuit board (PCB), sheet metal, printed radiators, etc. as noted above. However, the various design considerations above may be chosen consistent with, for example, maintaining a desired small form factor and/or other design requirements and attributes. For example, in one variant, the printing-based methods and apparatus described in co-owned and co-pending U.S. patent application Ser. No. 13/782,993 and entitled “DEPOSITION ANTENNA APPARATUS AND METHODS”, filed Mar. 1, 2013, which claims the benefit of priority to U.S. Provisional Patent application Ser. No. 61/606,320 filed Mar. 2, 2012, 61/609,868 filed Mar. 12, 2012, and 61/750,207 filed Jan. 8, 2013, each of the same title, and each of the foregoing incorporated herein by reference in its entirety, are used for deposition of the antenna radiator on the substrate. In one such variant, the antenna radiator includes a quarter-wave loop or wire-like structure printed onto the substrate using the printing process discussed therein. 
     The portable device illustrated in  FIGS. 2A-5C  (i.e. a wrist mountable watch, asset tracker, sports computer, etc. with GPS functionality) is placed in an enclosure  200 ,  300 ,  400 ,  500 , configured to have a generally circular form. However, it is appreciated that while this device shown has a generally circular form factor, the present disclosure may be practiced with devices that possess other desirable form factors including, without limitation, square (such as that illustrated with respect to  FIGS. 6A and 6B ), rectangular, other polygonal, oval, irregular, etc. In addition, the enclosure is configured to receive a display cover (not shown) formed at least partly with a transparent material such as a transparent polymer, glass or other suitable transparent material. The enclosure is also configured to receive a coupled antenna apparatus, similar to that shown in  FIG. 1 . In the exemplary embodiments, the enclosure is formed from an injection molded polymer, such as polyethylene or ABS-PC. In one variant, the plastic material further has a metalized conductive layer (e.g., copper alloy) disposed on its surface. The metalized conductor layers generally form a coupled antenna apparatus as illustrated in  FIG. 1 . 
     Referring now to  FIGS. 2A-2C , one embodiment of a coupled antenna apparatus  200  for use in a portable radio device in accordance with the principles of the present disclosure is shown.  FIG. 2A  illustrates the underside of the coupled antenna apparatus  200  illustrating the various connections made to a printed circuit board ( 219 ,  FIGS. 2B and 2C ). Specifically,  FIG. 2A  illustrates short circuit point  210  for the middle ring radiator element  204  as well as the short circuit point  216  and galvanic feed point  214  for the inner feed trace element  206 . Both the inner feed trace element and middle ring radiator element are disposed internal to the front cover  203  of the illustrated embodiment for the coupled antenna apparatus for use with a portable radio device. The front cover  203  (see  FIGS. 2A and 2C ) is manufactured, according to a first embodiment of the disclosure, using a laser direct structuring (“LDS”) polymer material that is subsequently doped and plated with an outer ring radiating element  202  (see  FIGS. 2B-2C ). The use of LDS technology is exemplary in that it allows complex (e.g. curved) metallic structures to be formed directly onto the underlying polymer material. 
     In addition, the middle ring radiator element  204  is disposed on the inside of the doped front cover  203  using LDS technology as well in an exemplary embodiment. The middle ring radiator element  204  is constructed into two (2) parts  204 ( a ) and  204 ( b ). In an exemplary implementation, element  204 ( a ) is used to provide a favorable place for the ground contact (short circuit point)  210  to mate. The short circuit point  210  is disposed on one end of the first part  204 ( a ) of middle ring radiator. Coupled antenna apparatus  200  further includes an LDS polymer feed frame  218  onto which an inside feed element  206  is subsequently constructed. The inside feed element comprises a galvanic feed point  216  as well as a short circuit point  214 , both of which are configured to be coupled to a printed circuit board  219  at points  216 ′ and  214 ′, respectively (see  FIG. 2C ). The inside feed frame element is disposed adjacent to the middle radiator ring element part  204  such that coaxial feed point is at a distance  222  from the middle radiator element short circuit point  210 . Short circuit points  210  of the middle radiator element and  214  of the inside feed element are configured to interface with the PCB  219  at points  210 ′ and  214 ′, respectively. A back cover  220  is positioned on the underside of the printed circuit board and forms the closed structure of the coupled antenna apparatus. 
     Referring now to  FIGS. 3A-3C , an alternative embodiment of a coupled antenna apparatus  300  for use in a portable radio device, in accordance with the principles of the present disclosure, is shown.  FIG. 3A  illustrates the underside of the coupled antenna apparatus  300  showing the various connections made to a printed circuit board ( 319 ,  FIG. 3C ). Specifically,  FIG. 3A  illustrates a short circuit point  310  for the middle ring radiator element  304  as well as the short circuit point  316 , and a galvanic feed point  314  for the inner feed trace element  306 . Both the inner feed trace element and middle ring radiator element are disposed internal to the front cover  303  of the illustrated embodiment for the coupled antenna apparatus for use with a portable radio device. The front cover  303  (see  FIGS. 3A and 3C ), is in an exemplary embodiment, manufactured using a laser direct structuring (“LDS”) polymer material that is subsequently doped and plated with an outer ring radiating element  302  (see  FIGS. 3B-3C ). In addition, the middle ring radiator element  404  is disposed on the inside of the doped front cover  303  using LDS technology as well in an exemplary embodiment. The middle ring radiator element  304  is constructed into two (2) parts  304 ( a ) and  304 ( b ), and incorporates a short circuit point  310  that is disposed on one end of the first part  304 ( a ) of middle ring radiator. The outer ring radiating element  302  and middle ring radiator  304  are similar in construction to the embodiment illustrated in  FIGS. 2A-2C . However, the coupled antenna apparatus  300  differs from the embodiment of  FIGS. 2A-2C  in that an inside feed element  306  is subsequently constructed directly onto the inside of front cover  303 , rather than being formed on a separate feed frame. The inside feed element comprises a galvanic feed point  316  as well as a short circuit point  314 , both of which are configured to be coupled to a printed circuit board  319  at points  316 ′ and  314 ′, respectively (see  FIG. 3C ). A back cover  320  is positioned on the underside of the printed circuit board and forms the closed structure of the coupled antenna apparatus. 
     Referring now to  FIGS. 4A-4C , yet another alternative embodiment of a coupled antenna apparatus  400  for use in a portable radio device, in accordance with the principles of the present disclosure, is shown. In the illustrated embodiment of  FIGS. 4A-4C , the front cover  403  is manufactured from a non-LDS polymer, such as ABS-PC, or Polycarbonate. Rather, a middle ring frame  405  is separately provided such that the middle ring radiator element  404  and the inside feed element  406  are constructed onto the middle ring frame  405 . The middle ring frame is advantageously comprised of an LDS polymer, with the middle ring radiator element and inside feed element being plated onto the surface of the middle ring frame. In addition, the outer ring radiating element  402  comprises a stamped metallic ring formed from e.g., stainless steel, aluminum or other corrosion resistant material (if exposed environmental stress without any additional protective coating). The selected material ideally should have adequate RF conductivity. Plated metals can be also used, for example nickel-gold plating, etc. or other well-known RF materials that are disposed onto the front cover  403 . The middle ring frame includes three (3) terminals that are configured to be coupled electrically to the printed circuit board  419 . These include a short circuit point  410  for the middle ring radiator element  404 , as well as the short circuit point  416  and galvanic feed point  414  for the inner feed trace element  406 . The short circuit point  410  for the middle ring radiator is configured to couple with the printed circuit board  419  at pad  410 ′, while the short circuit point  416  and galvanic feed point  414  are configured to couple with the printed circuit board  419  at pads  416 ′ and  414 ′, respectively. The middle ring radiator element  404  is constructed into two (2) parts  404 ( a ) and  404 ( b ), and incorporates a short circuit point  410  that is disposed on one end of the first part  404 ( a ) of middle ring radiator. The part which has the ground contact  410  is in the exemplary embodiment used as a coupling element, and rest of the middle ring element  404  is left “floating” (i.e., no RF contacts) and does not contribute to the radiation or coupling. A back cover  420  is subsequently positioned on the underside of the printed circuit board and forms the closed structure of the coupled antenna apparatus  400 . 
     While the aforementioned embodiments generally comprise a single coupled antenna apparatus disposed within a host device enclosure, it will also be appreciated that in some embodiments, additional antenna elements in addition to, for example, the exemplary coupled antenna apparatus  100  of  FIG. 1  can be disposed within the host device. These other antenna elements can designed to receive other types of wireless signals, such as and without limitation e.g., Bluetooth®, Bluetooth Low Energy (BLE), 802.11 (Wi-Fi), wireless Universal Serial Bus (USB), AM/FM radio, International, Scientific, Medical (ISM) band (e.g., ISM-868, ISM-915, etc.), ZigBee®, etc., so as to expand the functionality of the portable device, yet maintain a spatially compact form factor. An exemplary embodiment comprising more than one coupled antenna assembly is shown in  FIGS. 5A-5C . 
     In the illustrated embodiment of  FIGS. 5A-5C , similar to that shown in  FIGS. 4A-4C , the front cover  503  is manufactured from a non-LDS polymer, such as for example ABS-PC, or Polycarbonate. Two middle ring frame elements  505  are separately provided such that the middle ring radiator element  504  and the inside feed element  506  are constructed onto the pair of middle ring frames  505 . The exemplary middle ring frames are advantageously comprised of an LDS polymer, with the middle ring radiator element and inside feed element being plated onto the surface of the middle ring frame elements. In addition, the outer ring radiating element  502  comprises a stamped metallic ring that is disposed onto the front cover  503 . The middle ring frame includes five (5) terminals that are configured to be coupled electrically to the printed circuit board  519 . These include short circuit points  510 ,  513 ,  515  for the middle ring radiator elements  504  as well as the short circuit point  516  and galvanic feed point  514  for the inner feed trace element  506 . The short circuit points  510 ,  513 ,  515  for the middle ring radiator is configured to couple with the printed circuit board  519  at pad locations  510 ′,  513 ′,  515 ′, respectively, while the short circuit point  516  and galvanic feed point  514  are configured to couple with the printed circuit board  519  at pads  516 ′ and  514 ′, respectively. The middle ring radiator element  504  is constructed into two (2) parts  504 ( a ) and  504 ( b ) and incorporates a short circuit point  510  that is disposed on one end of the first part  504 ( a ) of middle ring radiator. In the exemplary embodiment, part  504   b  provides the middle ring for GPS frequency excitation, and part  504   a  provides the middle ring excitation for another frequency (e.g., 2.4 GHz). Both middle ring elements are coupled to the same top (outer) ring radiator, making the complete structure operate in a dual-band mode. A back cover  520  is subsequently positioned on the underside of the printed circuit board and forms the closed structure of the coupled antenna apparatus  500 . 
     The coupled antenna apparatus  500  illustrated comprises two antenna assemblies “a” and “b” such that “a” comprises middle radiator element  504 ( 1 ) and inside feed element  506 ( 1 ), and “b” comprises middle radiator element  504 ( 2 ) and inside feed element  506 ( 2 ), both “a” and “b” having a common outer ring element  502 . The two antenna assemblies may operate in the same frequency band, or alternatively, in different frequency bands. For example, antenna assembly “a” may be configured to operate in a Wi-Fi frequency band around 2.4 GHz, while antenna assembly may be configured to operate in the GNSS frequency range to provide GPS functionality. The operating frequency selection is exemplary and may be changed for different applications according to the principles of the present disclosure. 
     Moreover, the axial ratio (AR) of the antenna apparatus of the present disclosure can be affected when antenna feed impedance is tuned in conjunction with user body tissue loading (see prior discussion of impedance tuning based on ground and feed trace locations). Axial ratio (AR) is an important parameter to define performance of circularly polarized antennas; an optimal axial ratio is one (1), which correlates to a condition where the amplitude of a rotating signal is equal in all phases. A fully linearly polarized antenna would have infinite axial ratio, meaning that its signal amplitude is reduced to zero when phase is rotated 90 degrees. If an optimal circular polarized signal is received with a fully linearly polarized antenna, 3 dB signal loss occurs due to polarization mismatch. In other words, 50% of the incident signal is lost. In practice, it is very difficult to achieve optimal circular polarization (AR=1) due to asymmetries on mechanical constructions, etc. Conventionally used ceramic GPS patch antennas typically have an axial ratio of 1 to 3 dB when used in actual implementations. This is considered to be “industry standard”, and has a sufficient performance level. 
     Furthermore, it will also be appreciated that the device  200  can further comprise a display device, e.g., liquid crystal display (LCD), light emitting diodes (LED) or organic LED (OLED), TFT (thin film transistor), etc., that is used to display desired information to the user. Moreover, the host device can further comprise a touch screen input and display device (e.g., capacitive or resistive) or the type well known in the electronic arts, thereby providing user touch input capability as well as traditional display functionality. 
     Referring now to  FIGS. 6A and 6B  an alternative configuration of an outer ring element  600  useful in combination with the coupled antenna apparatus  100 ,  200 ,  300 ,  400 ,  500  illustrated in, for example,  FIGS. 2A-5C  is shown and described in detail. In one embodiment, a quarter-wave antenna is used for the feed element which is coupled to the upper cover which includes the outer ring element  600 . This upper cover can be made from an LDS polymer with the outer ring element  600  deposited thereon, or alternatively, can be made from a fully metallic bezel with or without an underlying polymer base material. The illustrated outer ring element  600  includes a generally rectangular profile with the addition of one or more extra conductive portions  602  useful in optimizing frequency and RHCP and LHCP gain. However, it is appreciated that other outer ring element shapes (such as circular or other polygonal shapes) could readily be substituted if desired. Moreover, while the outer ring element  600  structure of  FIGS. 6A and 6B  are illustrated using relatively simple geometries, it is appreciated that more complex three-dimensional (3D) structures can be quite easily achieved using the various methodologies described previously herein. 
     As illustrated in  FIGS. 2A-5C , antenna optimization is typically performed by varying the parameters of the inside antenna elements; however, such an optimization makes it difficult to, for example, optimize all of the GPS/GLONASS antenna parameters such as AR/RHCP/LHCP. By varying the outer ring element  600  structure, various electrical parameters can now be optimized. Specifically, by varying the geometry of the outer ring element  600 , the coupled antenna apparatus can now optimize circular polarization including, for example, increasing RHCP gain, decreasing LHCP gain and having a good axial ratio. For example, if the outer ring element  600  is made asymmetrical (such as that shown in  FIG. 6A ), the coupled antenna apparatus electrical parameters can be adjusted so as to optimize RHCP/LHCP/AR gain. Moreover, in both asymmetrical and symmetrical designs (such as that shown in  FIGS. 6A and 6B ), the extra metal length, width, thickness and shape of the outer ring element  600  can also be manipulated in order to optimize the RHCP/LHCP/AR and resonant parameters as discussed below with regards to  FIGS. 10-13 . By varying the geometrical structure of the outer ring element, various antenna performance parameters can be optimized resulting in, for example, a stronger satellite signal receiver. 
     Performance 
     Referring now to  FIGS. 7-9 , performance results obtained during testing by the Assignee hereof of an exemplary coupled antenna apparatus constructed according to the present disclosure, such as that illustrated in  FIGS. 2A-2C , are presented. 
       FIG. 7  illustrates an exemplary plot of return loss S 11  (in dB) as a function of frequency, measured, while connected to a simulated wrist, utilizing an exemplary antenna apparatus constructed in accordance with the embodiment depicted in  FIGS. 2A-2C . Exemplary data for the frequency band show a characteristic resonance structure at 1.575 GHz, with an intermediate frequency bandwidth (IFBW) of 70 kHz, thus producing an approximate frequency operating range of 1540-1610 MHz. More specifically, the return loss at 1.575 GHz is approximately −20.2 dB (decibels). 
       FIG. 8  presents data anecdotal performance (measured at the wrist) produced by a test setup emulating the exemplary antenna embodiment of  FIGS. 2A-2C . More specifically, the data at  FIG. 8 , line (i) demonstrates that the current antenna apparatus positioned within the portable device and on the wrist of the user achieves an efficiency of approximately −7 dB to −6 dB. Furthermore,  FIG. 8 , line (v) demonstrates that the current antenna apparatus positioned within the portable device and on the wrist of the user achieves an efficiency of greater than 20% over the exemplary frequency range between 1550 and 1605 MHz with the highest efficiency (about 27%) occurring at approximately 1617 MHz. The antenna efficiency (in percent) is defined as the percentage of a ratio of radiated and input power:
 
AntennaEfficiency %=(Radiated Power/Input Power)×100%  Eqn. (1)
 
     An efficiency of zero (0) dB corresponds to an ideal theoretical radiator, wherein all of the input power is radiated in the form of electromagnetic energy. Furthermore, according to reciprocity, the efficiency when used as a receive antenna is identical to the efficiency described in Equation 1. Thus, the transmit antenna efficiency is indicative of the expected sensitivity of the antenna operating in a receive mode. 
     The exemplary antenna of  FIGS. 2A-2C  is configured to operate in an exemplary frequency band from 1550 MHz to 1650 MHz. This capability advantageously allows operation of a portable computing device with a single antenna over several mobile frequency bands such as the GPS and GLONASS frequency bands. However, as persons skilled in the art will appreciate, the frequency band composition given above may be modified as required by the particular application(s) desired, and additional bands may be supported/used as well. 
       FIG. 8  illustrates exemplary LHCP (iii) and RHCP (iv) gain data for the test setup emulating the exemplary antenna of  FIGS. 2A-2C , as shown herein. As illustrated, the RHCP gain (line iv) is appreciably higher than the LHCP gain (line iii). Accordingly, in satellite navigation system applications where signals would be transmitted downward to a user from orbiting satellites, the LHCP gain is suppressed while still allowing for dominating RHCP gain. Thus, by suppressing the LHCP gain compared to the RHCP gain, the receiver sensitivity to RHCP signals does not suffer from a high LHCP gain, thereby increasing positional accuracy in the exemplary case of satellite navigation applications. 
       FIG. 8 , line (ii) illustrates the free-space test data of axial ratio (to zenith) in dB. The antenna apparatus  100  of device  200  has AR of 2 dB-7 dB in 1550-165 MHz. On the band of interest (1575-1610), AR is 2-3 dB, which is not perfect (perfect is 0 dB) circular polarization, but a typical value that is commonly accepted by industry in the context of real-world implementations on actual host units. Other implementations of the exemplary antenna of the disclosure have achieved a 1 db level during testing by the Assignee hereof. 
       FIG. 9  illustrate active test data relating to measured SNR (signal to noise ratio) for a prior art patch antenna, and an embodiment of the coupled antenna apparatus measured from an actual satellite (constellation). As illustrated, the data obtained from the inventive antenna apparatus is generally better than the reference (patch) antenna in SNR level. 
       FIGS. 10 and 11  illustrate exemplary RHCP and LHCP gain data for the test setup emulating the exemplary antenna of, for example,  FIGS. 2A-2C  utilized in conjunction with the asymmetrical outer ring element of  FIG. 6A , as shown herein. As illustrated, the RHCP gain ( FIG. 10 ) is appreciably higher than the LHCP gain ( FIG. 11 ) for the asymmetrical outer ring element of  FIG. 6A  as compared with an outer ring element that does not have additional conductive portions added to the structure. Accordingly, in satellite navigation system applications where signals would be transmitted downward to a user from orbiting satellites, the LHCP gain is suppressed while still allowing for dominating RHCP gain. Thus, by suppressing the LHCP gain compared to the RHCP gain, the receiver sensitivity to RHCP signals does not suffer from a high LHCP gain, thereby increasing positional accuracy in the exemplary case of satellite navigation applications. 
       FIG. 12  illustrates the free-space test data of axial ratio (to zenith) in dB of the exemplary antenna of, for example,  FIGS. 2A-2C  utilized in conjunction with the asymmetrical outer ring element of  FIG. 6A . The coupled antenna apparatus utilizing the asymmetrical outer ring element has an AR of 10 dB-12 dB in the 1500-1650 MHz frequency range while the coupled antenna apparatus that does not utilize the asymmetrical outer ring element has an AR of 13 dB-16 dB in the 1500-1650 MHz frequency range. 
       FIG. 13  illustrates an exemplary plot of return loss S 11  (in dB) as a function of frequency, measured, while connected to a simulated wrist, utilizing a symmetrical outer ring element ( FIG. 6B ) in conjunction with the coupled antenna apparatus embodiment depicted in, for example,  FIGS. 2A-2C . Exemplary data for the frequency band show that the characteristic resonance structure can be manipulated through the addition of additional conductive portions to the outer ring element. For example, the characteristic resonance structure utilizing the symmetrical outer ring element is present at approximately 1.600 GHz while characteristic resonance structure for a coupled antenna apparatus without the additional conductive portions is present at approximately 1.650 GHz. While the results shown is exemplary, it is appreciated that characteristic resonance frequency can be manipulated via the addition of conductive portions in any of the X, Y, and Z directions depending upon what electrical parameters want to be tuned. 
       FIG. 14  shows an additional embodiment of a coupled antenna apparatus including a transient voltage suppressor (TVS).  FIG. 14  is similar to  FIG. 1  described above. In certain situations it is desirable to have the outer radiator element  132  as a portion of the antenna. The outer radiator element  132  can share some or all of the properties as the outer element  102  as discussed above. However, as the outer radiator element  132  is a portion of the antenna it cannot readily be grounded in the antenna configuration of  FIG. 1 . Therefore, a TVS diode  130  is electrically connected to the outer radiator element  132 . An example schematic thereof is shown in  FIG. 14 . The TVS  130  therefore connects the outer radiator element  132  to a ground when there is a big enough potential or voltage in the outer radiator element  132 . As such, the TVS diode protects the electronics within a device from being harmed from, for example, an electric spark outside of the device. 
     In the example of  FIG. 14 , the first part  104 ( a ) of the middle radiator element, and the inner feed element  106  are connected to the ground. Additionally, they are inside the electrostatic discharge (ESD) protection provided by the outer radiator element  132  connected to the TVS diode. Without TVS grounding a large enough potential will in practice find its way through the outermost conductive portion of a device and damage internal electronics. One particular problem in smart watches and mobile devices is that large potentials will pass through display lines and connections in and damage display drivers. 
       FIGS. 15A-15C  shows an example, similar to that of  FIG. 2 , of a wrist-wearable electronic device wherein the bezel includes an outer radiator element  232  which is electrically coupled to an ESD circuit  230 . As shown in  FIG. 15C , the ESD circuit  230  can be located on the printed circuit board  219 . However, the ESD circuit  230  could be located in or on another portion of the electronic device. Furthermore, the ESD circuit  230  can be electrically coupled to the outer radiator element  232  by, for example, a pogo pin. The ESD circuit  230  may consist of a low capacitance TVS diode according to  FIG. 14 , or of a LC circuit according to  FIG. 16A , which is discussed below. 
     The outer radiator element can typically be ungrounded. The coupled antenna apparatus can have an ESD circuit consisting of an LC circuit which is electrically coupled to the outer radiator element. The LC circuit can be, for example, a coil L which is designed to resonate with its own parasitic capacitance at the same or approximately the same frequency as the received antenna signal. In such an embodiment, no external capacitor C is needed. 
       FIG. 16A  shows an embodiment of an inventive coupled antenna apparatus including a transient voltage suppressor circuit  134 .  FIG. 16A  is similar to  FIGS. 1 and 14  described above. In certain situations it is desirable to have the outer radiator element  132  as a portion of the antenna. The outer radiator element  132  can share some or all of the properties as the outer element  102  as discussed above. However, as the outer radiator element  132  is a portion of the antenna it cannot readily be grounded in the antenna configuration of  FIG. 1 . Therefore, an LC circuit  134  is electrically connected to the outer radiator element  132 . An example thereof is shown in  FIG. 16A . The LC circuit  134  is closed, i.e. connects the outer radiator element  132  to ground at low frequencies and DC. The value of the impedance of the LC the circuit is thus selected to allow electrostatic discharges to flow through it. The LC circuit  134  protects the electronics within a device from being harmed from, for example, an electric spark outside of the device. 
     At its resonant frequency, the LC  134  circuit makes a stopband and acts like an open circuit. The values of the L and C components are chosen for the circuit to resonate at the antenna&#39;s working frequency. 
     In the example of  FIG. 16A , the first part  104 ( a ) of the middle radiator element, and the inner feed element  106  are connected to the ground. Additionally electrostatic discharge (ESD) protection is provided by the outer radiator element  132  connected to the LC circuit  134 . Without such a high-impedance grounding a large enough potential will in practice find its way through the outermost conductive portion of a device and damage internal electronics. One particular problem in smart watches and mobile devices is that large potentials will pass through display lines and connections in and damage display drivers. 
     According to certain examples, a fixed or variable capacitor C, or one or more switchable capacitors C 1 , C 2  (see  FIG. 16B ) may be added in parallel to the coil L, in order to make the LC circuit  134  tunable. By tuning a variable capacitor C, and/or by switching capacitors C 1  and C 2  with suitably selected capacitances on and/or off, the LC circuit  134  or  134   a  can be tuned to different frequencies received by the antenna, such as to the frequencies of GPS, Glonass and Galileo navigation systems. Also other wireless systems may be interfaced with the inventive device, such as Bluetooth or WiFi, which frequencies may be received and the LC circuit  134  or  134   a  tuned to resonate on such frequencies as well, thus providing optimization of the antenna performance in a variety of systems. Surprisingly, LC circuits  134  or  134   a  provides ESD protection with a very small negative impact on antenna performance. 
     A bezel, for example for a wrist-wearable electronic device, can have an inner and an outer surface. All or a portion of the outer surface of the bezel can be an outer radiator element. Furthermore, one or more additional radiator elements can be located, housed and/or supported by the inner surface of the bezel. According to certain examples, one or more of the additional radiator elements are electrically isolated from, but mechanically connected to the inner surface of the bezel. 
     As described above, a coupled antenna apparatus can comprise a bezel which includes an outer radiator element. The outer radiator element forms a part of the antenna structure. The outer radiator element can be, for example, a section and/or sector of the bezel. The outer radiator element can have a closed loop structure and can even be the entire bezel. In examples where the bezel is metallic, the outer radiator element can be an integral portion of the bezel. The outer radiator element can also be a separate portion of the bezel which is combined with one or more other portions to form a bezel. 
     Numerous types of electronic devices can include a coupled antenna apparatus as described herein. One example is a wrist-wearable electronic device having an outer housing which includes one or more portions. At least one of the portions of the housing can be a bezel. According to certain examples the outer housing of the device includes a bezel, in accordance with any bezel discussed above, and a body. The body and/or the bezel can contain a plurality of electrical components. An outer portion of the bezel can contain a metallic portion which is, or acts as an outer radiator element. Said outer radiator element can be generally ungrounded. However, said outer radiator element can be electrically coupled, for example by a pogo pin, to a TVS device housed within the outer housing, to protect at least some of the plurality of internal electrical components from large potentials which the outer radiator element may be thereby exposed to. 
     Furthermore, according to certain examples, an electronic device may further include at least one screw. The screw may be primarily for mechanically coupling the bezel to the body of the outer housing, and/or to one or more other portions of the device. The screw may be electrically conductive, e.g. metallic, and therefore in electrical contact with a portion of the bezel and/or outer radiator element. Thus, the screw can form an additional conductive portion of the outer radiator element. In certain embodiments the screw may electrically ground at least a portion of the bezel. Furthermore, other connection means besides a screw but having similar electro-mechanical properties may be used in place of an actual screw. 
     It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. 
     As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention. 
     Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
     While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.