Patent Publication Number: US-8988293-B2

Title: Multiband antenna assemblies including helical and linear radiating elements

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/MY2012/000078 filed Apr. 12, 2012, which, in turn, claims the benefit and priority of International Application No. PCT/MY2011/000194 filed Aug. 24, 2011. The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to multiband antenna assemblies including helical and linear radiating elements. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     The users of portable wireless devices are putting increasing demands to provide more functionality in smaller and smaller portable wireless devices without degrading reception or connectivity. Thus, although the space available in a wireless device for an antenna continually decreases, the performance needs of the antenna continually increase. Moreover, many wireless devices today require the ability to operate over multiple frequency ranges that frequently require the use of multiple antennas to cover the functionality of the device, exasperating the problem. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to various aspects, exemplary embodiments are disclosed of antenna assemblies that include helical and linear radiating elements. For example, an exemplary embodiment of a multiband antenna assembly may generally include at least one helical radiator having a longitudinal axis. At least one linear radiator is aligned with and/or disposed at least partially along the longitudinal axis of the at least one helical radiator. The antenna assembly is resonant in at least three frequency bands. 
     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 embodiment of a multiband antenna assembly including helical and top loaded linear radiating elements and a matching network; 
         FIG. 2  is a perspective view illustrating the exemplary manner by which the antenna assembly shown in  FIG. 1  may be externally mounted to a wireless device housing according to an exemplary embodiment; 
         FIG. 3A  illustrates the antenna assembly shown in  FIG. 1 , and also illustrating the A/ 4  electrical length of the dual pitch helical radiator for the VHF band and the A/ 4  electrical length of the wider pitch, lower portion of the helical radiator for the UHF band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 3B  illustrates the antenna assembly shown in  FIG. 1 , where the helical radiator is not shown to better illustrate the λ/4 electrical length of the linear radiator&#39;s inner, center conductor for the UHF band and the λ/4 electrical length of the linear radiator&#39;s top loaded conductor for the GPS band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 4  illustrates an example of a linear radiator that may be used in the antenna assembly shown in  FIG. 1 , where the helical radiator is not shown to better illustrate the linear radiator&#39;s inner, center electrically conducting member and top loaded conductor, which are configured as radiating elements for respective low band operation and high band operation according to this example embodiment; 
         FIGS. 5 through 7  illustrate further examples of a linear radiator that may be used in the antenna assembly shown in  FIG. 1 , where the helical radiator is not shown to better illustrate the linear radiator&#39;s inner, center electrically conducting member and top loaded conductor according to alternative example embodiments; 
         FIGS. 8A and 8B  illustrate an example matching network topology of a printed circuit board assembly with lumped components of the antenna assembly shown in  FIG. 1  according to an exemplary embodiment; 
         FIG. 9  is an exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly shown in  FIG. 1  and illustrating the antenna&#39;s resonance for the VHF, UHF, and GPS bands when the antenna assembly was measured in free space condition; 
         FIG. 10  is another exemplary line graph illustrating return loss in decibels versus frequency in megahertz (MHz) measured for the antenna assembly shown in  FIG. 1  in a hand held position; 
         FIG. 11  is a table with performance summary data of measured efficiency and gain performance of the antenna assembly shown in  FIG. 1  for the VHF band (in a hand held position) and for the UHF and GPS bands (in free space); 
         FIGS. 12 through 15  illustrate radiation patterns (azimuth plane) measured for the antenna assembly shown in  FIG. 1  in a hand held position at a frequency of 155 MHz and in free space at frequencies of 400 MHz, 450 MHz, 512 MHz, and 1574 MHz, respectively; 
         FIG. 16  illustrates a radiation pattern (phi zero degree plane) measured for the antenna assembly shown in  FIG. 1  in free space at a frequency of 1575 MHz; 
         FIG. 17  is a perspective view of another exemplary embodiment of a multiband antenna assembly including helical and top loaded linear radiating elements and a matching network, where the linear radiating element is between a bottom helical radiating element and a top suspended helical radiating element; 
         FIG. 18  is a perspective view illustrating the exemplary manner by which the antenna assembly shown in  FIG. 17  may be externally mounted to a wireless device housing according to an exemplary embodiment; 
         FIG. 19  illustrates an example sheath for the antenna assembly shown in  FIG. 1  and/or  FIG. 17  according to an exemplary embodiment; 
         FIG. 20A  is an exploded perspective view illustrating components of the antenna assembly shown in  FIG. 17  and sheath shown in  FIG. 19  according to an exemplary embodiment; 
         FIG. 20B  is a cross sectional view taken along the line  20 B- 20 B in  FIG. 19  and illustrating the exemplary manner by which the components shown in  FIG. 20A  may be assembled; 
         FIG. 21A  illustrates the antenna assembly shown in  FIG. 17 , and also illustrating the λ/2 electrical length of the antenna assembly for the UHF band and the λ/4 and λ/2 electrical length of the bottom helical radiating element for the 7-800 MHz frequencies band and GPS band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 21B  illustrates the antenna assembly shown in  FIG. 17 , where the helical radiators are not shown to better illustrate the λ/4 electrical length of the linear radiator&#39;s inner, center conductor for the 7-800 MHz frequency band and the λ/4 combined electrical length of the linear radiator&#39;s center conductor and top loaded conductor for the UHF band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 22  illustrates an example of a linear radiator that may be used in the antenna assembly shown in  FIG. 17 , where the helical radiator is not shown to better illustrate the linear radiator&#39;s inner, center electrically conducting member and top loaded conductor; 
         FIGS. 23A and 23B  illustrate an example matching network topology of a printed circuit board assembly with lumped components of the antenna assembly shown in  FIG. 17  according to an exemplary embodiment; 
         FIG. 24  is an exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly shown in  FIG. 17  and illustrating the coupling effect from the top suspended helical radiating element and the antenna&#39;s resonance for the GPS band; 
         FIG. 25  is an exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly shown in  FIG. 17  when covered by the sheath shown in  FIG. 19  and illustrating the GPS resonance shift to lower frequency due to load by sheath; 
         FIG. 26  is another exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly shown in  FIG. 17  in a hand held position; 
         FIG. 27  is a table with performance summary data of measured efficiency and gain performance of the antenna assembly shown in  FIG. 17  (in free space) for the UHF, 7-800, and GPS bands; 
         FIGS. 28 through 33  illustrate radiation patterns (azimuth plane) measured for the antenna assembly shown in  FIG. 17  in free space at frequencies of 400 MHz, 470 MHz, 520 MHz, 764 MHz, 830 MHz, and 870 MHz, respectively; 
         FIGS. 34 and 35  illustrate respective radiation patterns (phi zero degree plane and phi ninety degree plane) measured for the antenna assembly shown in  FIG. 17  in free space at a frequency of 1575 MHz; 
         FIG. 36A  illustrates a multiband antenna assembly including upper and lower suspended linear radiating elements and helical radiating elements according to another exemplary embodiment; 
         FIG. 36B  illustrates the antenna assembly shown in  FIG. 36A  with the spacers and pre-mold removed to show additional features; 
         FIG. 37A  illustrates the antenna assembly shown in  FIG. 36B , and also illustrating the λ/4 total electrical length of the upper helical radiator and the adaptor for the VHF band and the 3λ/4 combined electrical length of the lower linear radiator and the narrower pitch coils of the lower helical radiator for the 7-800 MHz band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 37B  illustrates the antenna assembly shown in  FIG. 36B , and also illustrating the λ/4 electrical length of the upper helical radiator for the UHF band, the λ/4 and λ/2 electrical length of the narrow pitch coils of the lower helical radiating element for the UHF band and the 7-800 MHz band, and the λ/4 and λ/2 electrical length of the wider pitch coils of the lower helical radiating element for the 7-800 MHz band and the GPS band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 38  is an exemplary line graph illustrating measure return loss in decibels (dB) at hand held position versus frequency in megahertz (MHz) for the antenna assembly shown in  FIG. 36A ; 
         FIG. 39  are tables with measured efficiency and gain in decibels (dB) for the antenna assembly shown in  FIG. 36A  for the VHF band (azimuth plane—hand held position) and for the UHF, 7-800, and GPS bands (in free space and hand held position); 
         FIGS. 40 through 42  illustrate radiation patterns (azimuth plane) measured for the antenna assembly shown in  FIG. 36A  in a hand held position at a VHF frequency of 155 MHz and in a hand held position and in free space at a UHF frequency of 470 MHz and at a 7-800 MHz band frequency of 806 MHz, respectively; 
         FIG. 43  illustrates a radiation pattern (phi zero degree plane) measured for the antenna assembly shown in  FIG. 36A  in free space and hand held position at a GPS frequency of 1575 MHz; 
         FIG. 44  is a perspective view of a multiband antenna assembly including a helical radiating element, a top loaded linear radiating element, and a bottom suspended helical radiating element according to another exemplary embodiment; 
         FIG. 45  is an exploded perspective view illustrating components of the antenna assembly shown in  FIG. 44  and a sheath according to an exemplary embodiment; 
         FIG. 46A  illustrates the antenna assembly shown in  FIG. 45  after the components have been assembled; 
         FIG. 46B  is a cross sectional view taken along the line  46 B- 46 B in  FIG. 46A ; 
         FIG. 47A  illustrates the antenna assembly shown in  FIG. 44 , where the bottom suspended helical radiator and the top loaded linear radiator are not shown to better illustrate the 3λ/4 electrical length of the helical radiator for the VHF band and the λ/4 electrical length of the wider pitch coils of the helical radiator for the UHF band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 47B  illustrates the antenna assembly shown in  FIG. 44 , and also illustrating the λ/4 electrical length of the bottom suspended helical radiator for the 7-800 MHz band, the λ/4 combined electrical length of the bottom suspended helical radiator and linear radiator&#39;s inner, center conductor for the UHF band, and the 3λ/4 combined electrical length of the bottom suspended helical radiator and linear radiator&#39;s top loaded conductor for the 7-800 MHz band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 47C  illustrates the antenna assembly shown in  FIG. 44 , where the helical radiators are not shown to better illustrate the λ/4 electrical length of the linear radiator&#39;s inner, center conductor for the 7-800 MHz band and the λ/4 combined electrical length of the linear radiator&#39;s center conductor and top loaded conductor for the UHF band, where these electrical lengths and frequencies are provided for purposes of illustration only according to exemplary embodiments; 
         FIG. 48  illustrates examples of flat pattern profiles for suspended helical radiators before being wrapped or coiled and which may be used in the antenna assembly shown in  FIG. 44  according to exemplary embodiments; 
         FIGS. 49 through 51  illustrate examples of a linear radiator that may be used in the antenna assembly shown in  FIG. 44  according to exemplary embodiments; 
         FIG. 52  is an exemplary line graph illustrating measured return loss in decibels (dB) at hand held position versus frequency in megahertz (MHz) for the antenna assembly shown in  FIG. 44 ; 
         FIG. 53  are tables with measured efficiency and gain in decibels (dB) for the antenna assembly shown in  FIG. 44  for the VHF band (azimuth plane—hand held position) and for the UHF, 7-800, and GPS bands (in free space); 
         FIGS. 54 through 60  illustrate radiation patterns (azimuth plane) measured for the antenna assembly shown in  FIG. 44  in a hand held position at a VHF frequency of 155 MHz and in free space at UHF frequencies of 400 MHz, 470 MHz and 520 MHz and at 7-800 MHz band frequencies of 764 MHz, 830 MHz, and 870 MHz, respectively; and 
         FIGS. 61 and 62  illustrate radiation patterns (phi zero degree plane and phi ninety degree plane) measured for the antenna assembly shown in  FIG. 44  in free space at a GPS frequency of 1575 MHz. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     The inventor hereof has recognized that there is a demand for portable two way radios having interoperability capability, which leads to multiband and multimode two way radios. But with such multiband and multimode radios, the inventor hereof has recognized that it is a great challenge to provide a suitable antenna with various band capabilities. For example, the inventor hereof has recognized that conventional helical antennas tend to have narrow bandwidths, especially for Very High Frequency (VHF) band (e.g., 136 MHz to 174 MHz) and/or Ultra High Frequency (UHF) band (e.g., 380 MHz to 527 MHz). The inventor has also recognized that the complexity of some existing multiband antennas only perform well at a limited portion of the entire UHF band. The inventor has further recognized that some existing multiband antennas also have poor manufacturability due to the complexity of integration of multiple radiating elements and having to also meet mechanical structural integrity requirements. 
     Accordingly, the inventor has disclosed herein multiband antenna assemblies that do not suffer from very narrow bandwidths especially in the UHF and VHF bands. Exemplary embodiments disclosed herein may be configured with the ability to achieve multiband application with an antenna assembly or unit having a suitably compact size in terms of diameter and length. An exemplary embodiment of an antenna assembly disclosed herein is configured to achieve multiband operation for frequencies associated with VHF (e.g., 136 MHz to 174 MHz), UHF (e.g., 380 MHz to 527 MHz), and GPS (e.g., 1575 MHz). Another exemplary embodiment of an antenna assembly disclosed herein is configured to achieve multiband operation for frequencies associated with UHF (e.g., 380 MHz to 527 MHz), 7-800 MHz frequency band (e.g., 764 MHz to 870 MHz) and GPS (e.g., 1575 MHz). In additional exemplary embodiments disclosed herein, an antenna assembly is configured to achieve multiband operation for frequencies associated with VHF, UHF, 7-800, and GPS bands. In such exemplary embodiments, the multiband operation may be achieved even though the antenna assembly has a relatively limited diameter and length (e.g., length less than 23 centimeters, etc.) and relatively thin profile. These frequency bands are examples only as other exemplary embodiments of an antenna assembly may be configured to be resonant at other frequencies and/or frequency bands, such as one or more of a VHF frequency bandwidth from 163 MHz to 174 MHz, a UHF frequency bandwidth from 403 MHz to 470 MHz, and GPS frequency of 1575 MHz. 
     As disclosed herein, exemplary embodiments of the multiband antenna assemblies may be configured so as to provide GPS radiation patterns that tilt up and have open sky efficiency better than 25%, to provide radiation patterns in the 7-800 MHz frequency band that tilt up and have near horizontal efficiency better than 30%; and/or also be associated with good manufacturability. 
     Accordingly, the inventor hereof has disclosed herein various exemplary embodiments of antenna assemblies that include helical and linear radiating elements. For example, a multiband antenna assembly may generally include one or more helical radiators and one or more linear radiators. The one or more linear radiators may be aligned with and/or disposed at least partially along a longitudinal axis (e.g., a longitudinal centerline or centrally located axis, axis along the length, etc.) of at least one of the one or more helical radiators. The antenna assembly may be resonant in at least three frequency bands. 
     With reference now to the figures,  FIG. 1  illustrates an exemplary embodiment of a multiband antenna assembly  100  embodying one or more aspects of the present disclosure. This exemplary embodiment has a design generally based on a monopole concept with multiple radiating elements. 
     As shown in  FIG. 1 , the antenna assembly  100  generally includes linear and helical radiators or radiating elements  104  and  112  coupled to a matching network  120  via an adapter  116  and contact spring  132 . As disclosed herein, the linear radiator  104  in this example is a top loaded conducting wire located generally inside the helical radiator  112 , such that the linear radiator  104  extends along or is aligned generally with the central longitudinal axis of the helix of the helical radiators  112 . The antenna assembly  100  terminates with a connector  124  (e.g., 50 Ohm connector, etc.) for connecting the antenna assembly  100  to a device (e.g., device housing  128  in  FIG. 2 , etc.), whereby the antenna assembly  100  depends to a ground plane of the device to excite. 
     As disclosed herein, this exemplary antenna assembly  100  is configured to be operable or to cover multiple frequency ranges or bands, including the VHF frequency band from about 136 MHz to about 174 MHz, the UHF frequency band from about 380 MHz to about 527 MHz, and the GPS frequency of about 1575 MHz. This particular antenna assembly  100  is configured so as to have an electrical length of one quarter wavelength (λ/4) for the VHF, UHF, and GPS bands as shown in  FIGS. 3A and 3B . The outer helical radiating element  112  corresponds to VHF and UHF bands. The total electrical length of the helical radiating element  112  is approximately equivalent to one quarter wavelength (λ/4) of the VHF band. The matching network  120  is operable to help broaden the bandwidth of the VHF band for resonance from 136 MHz to 174 MHz. 
     With continued reference to  FIG. 1 , the helical radiator  112  in this exemplary embodiment is a dual pitch helical coil radiator or spring having narrower and wider pitch coils  113 ,  114 , respectively, along the respective bottom and top portions of the helical radiator  112 . In operation, the lower coils  114  having the wider pitch are more responsive and resonant at the UHF band and are approximately equivalent to one quarter wavelength (λ/4) for the UHF band frequencies as shown in  FIG. 3A . The upper coils  113  having the narrower or closer pitch are operable for introducing another resonance at the VHF band. A third harmonic of the UHF band is also resonant at the GPS band. Accordingly, multiple resonant frequencies may be introduced by the dual pitch helical radiator  112  without a whip or linear radiating element. 
     A wide range of electrically conducting materials, preferably highly conductive materials, may be used for the helical radiator  112 . By way of example, the helical radiator  112  may be formed from copper wire, spring wire, copper/tin/nickel plating wire, enameled wire, among other materials that may be configured to have the helical/spring configuration shown in  FIG. 1 . In addition, the coils of the helical radiator  112  are configured (e.g., dual pitch, spacing, size, shape, etc.) in this example for specific frequency bands. Alternative embodiments may be configured for use with additional and/or different frequencies such as by varying the windings of the helical radiator coils. For example, other embodiments may include one or more helical radiators having coils with a constant pitch or with more than two different pitches and/or with a tapering pitch such that the coil has an upper or lower section wider than the other section. 
     As shown in  FIG. 4 , the linear radiator  104  includes electrically conductive wire  106  (broadly, a first conductor) and a top loaded element  108  (broadly, a second conductor) at or along the end portion of the electrically conductive wire  106 . The electrically conducting wire  106  and top loaded element  108  are positioned relative to the helical radiating element  112  such that they extend through at least some of the coils of the helical radiating element  112  along a central longitudinal axis of the helix of the helical radiating element  112  as shown in  FIG. 1 . The coils of the outer helical radiating element  112  coil or wind counterclockwise generally about the length of the inner linear radiating element  104 , which is thus located generally inside the helical radiator  112 . 
     By way of example, the first conductor  106  of the linear radiator  104  may be formed from the electrically conducting wire at the center core of a coaxial cable as shown in  FIG. 4 . The top loaded element or second conductor  108  of the linear radiator  104  may comprise the braid soldered at the end of the coaxial cable. Accordingly, the braid of the coaxial cable may work as the second conductor  108 , while the center core of the coaxial cable works as the first conductor  106 . The coaxial cable&#39;s dielectric insulator  105  between the core and braid will operate to prevent direct contact therebetween. The first and second conductors  106 ,  108  are configured as radiating elements for respective low band operation (e.g., UHF band, etc.) and high band operation (e.g., GPS band, etc.) according to this example embodiment. 
     The first and second conductors  106 ,  108  are galvanically coupled or connected to each other at the top or end  109  of the linear radiator  104 . This electrical connection between the first and second conductors  106 ,  108  allows the antenna assembly  100  to be operable simultaneously at the UHF and GPS bands in this example. As shown in  FIG. 3B , the first conductor  106  has an electrical length of about one quarter wavelength (λ/4) for the UHF band, while the second conductor  108  has an electrical length of about one quarter wavelength (λ/4) for the GPS frequency of 1575 MHz. 
     In operation, coupling (e.g., parasitic coupling in this example, etc.) between the linear radiator  104  (top loaded conducting wire in this example) and the lower coils  114  of the helical radiating element  112  allows the antenna assembly  100  to maintain the bandwidth for the UHF band with antenna resonance from 380 MHz to 527 MHz as can be seen in  FIG. 10 . The linear radiator  104  and the additional closer pitch coils  113  at the top of the helical radiator  112  allow the antenna assembly  100  to operate at VHF, UHF and GPS at the same time. Overall, the outer helical radiating element  112  is more dominant when the antenna assembly  100  is operating at VHF band frequencies. But when the antenna assembly  100  is operating within the UHF and GPS bands, the H-field or E-field of the top loaded conducting wire  104  will couple to the outer helical radiating element  112  to radiate. 
     Also, with the combination of the top loaded linear and helical radiating elements  104 ,  112 , the antenna assembly  100  is excited in omnidirectional radiation patterns for the VHF and UHF bands as shown in  FIGS. 12 through 15 . In operation, the antenna assembly is able to achieve total efficiency and near horizon efficiency of more than 58% and 45% respectively for the UHF band as shown in  FIG. 11 . The top loaded electrically conducting wire also tilts up the GPS radiation pattern ( FIGS. 11 and 16 ) such that the antenna assembly  100  achieves more than 30% of open sky efficiency for the GPS frequency band in this example embodiment. 
     Alternative embodiments may include linear radiators having first and second conductors configured differently, including conductors formed from different materials other than coaxial cables and/or soldered braids at the end of the coaxial cables. Other exemplary embodiments may include a flexible electrically conducting wire or cable as the first conductor with a metal tube as the second conductor, which is crimped or soldered to the end of the wire or cable. In these example embodiments, an insulator jacket may be disposed or sandwiched between the metal tube and electrically conductive wire or cable. Examples of electrically conductive wires or cables that may be used include a speedometer cable, nickel titanium (NiTi) wire, among other suitable cables, wires, rods, and/or elongate generally straight conducting members. 
     In addition, other electrically conductive materials and/or configurations may be used for the first and/or second conductors of the linear radiator. For example, the second conductor may be formed from a spring or single wire instead of a soldered coaxial cable braid or metal tube. To this end,  FIGS. 5 through 7  illustrate further examples of linear radiators  204 ,  304 ,  404 , respectively, that may be used with the antenna assembly  100  with similar results in antenna performance. 
     As shown in  FIG. 5 , the linear radiator  204  includes a first conductor  206  and a second conductor  208  connected to each other at the top or end  209  of the first conductor  206 . In this example, the second conductor  208  is a spring or helical conductor suspended from the end  209  of the first conductor  206 , such that the spring  208  extends outwardly away from the first conductor  206 . 
     The linear radiator  304  shown in  FIG. 6  also includes a first conductor  306  and a second conductor  308  connected to each other at the top or end  309  of the first conductor  306 . But in this example, the second conductor  308  is a spring or helical conductor that extends in the opposite direction than did the spring  208  in  FIG. 5 . As shown in  FIG. 6 , the spring  308  extends back along the first conductor  306  such that the coils of the spring  308  coil or wind generally about the length of the first conductor  306 . 
       FIG. 7  illustrates another example of a linear radiator  404 , which includes a first conductor  406  and a second conductor  408  connected to each other at the top or end  409  of the first conductor  406 . But in this example, the second conductor  408  is a single straight portion of electrically conductive wire that extends parallel to and back along the first conductor  406 . 
       FIGS. 8A and 8B  illustrate an example matching network topology of a printed circuit board assembly that may be used in the antenna assembly  100 . In this example, the matching network  120  comprises lumped components  136  residing on front and back oppositely facing surfaces of the printed circuit board  138 . As shown in  FIGS. 1 and 2 , the matching network  120  is part of the antenna assembly  100  rather than the device to which the antenna assembly  100  will be connected. Accordingly, the antenna assembly  100  does not have to rely upon a matching network that is part of or internal to the device as the antenna assembly  100  instead includes its own (e.g., embedded, etc.) matching network  120 . 
     The matching network  120  may comprise one or more shunt or series capacitors and/or one or more shunt or series inductors depending on the matching network topology. Additionally, or alternatively, the circuit board  138  may also include other capacitors, inductors, resistors, or the like, as well as conductive traces. In operation, the matching network  120  helps to pull the antenna resonance to lower frequency(ies) compared to the structure capability to the low band. This means that the helical coil structure by itself may not have sufficient electrical length to achieve the full bandwidth of the low band. The impedance matching of the matching network  120  helps the antenna assembly to be tuned to lower frequency(ies). In this particular illustrated example, the matching network  120  is operable to help broaden the bandwidth of the VHF band for resonance from 136 MHz to 174 MHz. 
     Moreover, the printed circuit board  138  and lumped components  136  thereon that provide the impedance matching of the matching network  120  may be configured such that they will be contained within or under a sheath or radome (e.g., sheath  540  shown in  FIGS. 19 ,  20 A and  20 B, etc.) of the antenna assembly  100 . As shown in  FIG. 2 , the matching network  120  will be external to the device housing  128  when the antenna assembly  100  is coupled thereto. 
     In this particular example, the connector  124  of the antenna assembly  100  is a 50 ohm connector and is illustrated as a threaded connection. Alternative connectors may be used in other embodiments including a snap fit connection, etc. As shown in  FIG. 2 , the antenna assembly  100  may be threadedly connected to the device housing  128  such that the bulk of the antenna assembly or unit  100  is external to the device housing  128 . That is, the radiating elements  104 ,  112  and circuit board  138  having the matching network  120  of the antenna assembly  100  are able to be entirely contained within or under the sheath (e.g., sheath  540  shown in  FIG. 19 , etc.) and remain external to the wireless device housing  128 . Thus, the antenna assembly  100  is able to provide multiband operation in the VHF, UHF, and GPS frequency bands without having to significantly increase the overall size or volume of the wireless device housing  128 . By way of example only, the sheath may have a length of about 180 millimeters and a diameter of about 14.5 millimeters along the portion disposed over the connector  124 . 
     The radiating elements  104 ,  112  may be mechanically and electrically coupled to the circuit board  138  by the adapter  116  and contact spring  132 . The contact spring  132  may include a hook portion  134  (e.g., J-shaped or L-shaped hook portion, etc.) that extends through a hole in the circuit board  138  as shown in  FIGS. 8A and 8B . The circuit board  138  and radiating elements  104 ,  112  of the antenna assembly  100  may be coupled in a similar manner as that described below for the antenna assembly  500 , although this is not required. 
       FIGS. 9 through 16  provide analysis results measured for a prototype of the antenna assembly  100  shown in  FIG. 1 . These analysis results shown in  FIGS. 9 through 16  are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIGS. 9 and 10  are exemplary line graphs illustrating return loss in decibels versus frequency measured for the antenna assembly  100 . In  FIG. 9 , the antenna&#39;s resonance for the VHF, UHF, and GPS bands can be seen when the antenna assembly  100  was measured in free space condition. The data shown in  FIG. 10  was measured when the antenna assembly  100  was in the hand held position. Generally,  FIGS. 9 and 10  show that the antenna assembly  100  is operable with relatively good/acceptable return loss and bandwidths for the VHF, UHF, and GPS bands. 
       FIG. 11  is a table with performance summary data of measured efficiency and gain performance of the antenna assembly  100  for the VHF band (in a hand held position) and for the UHF and GPS bands (in free space). Generally, this performance summary data shows that the antenna assembly  100  has relatively good gain/efficiency for the VHF, UHF, and GPS bands, including good open sky efficiency of more than 30% for the GPS band. 
       FIGS. 12 through 16  illustrate radiation patterns measured for the antenna assembly  100 . The image at the center of each graph represents a device (e.g., two way radio, etc.) having the antenna assembly  100  mounted on top thereof. More specifically,  FIG. 12  illustrates radiation patterns (azimuth plane) measured for the antenna assembly  100  in a hand held position at a VHF frequency of 155 MHz where the image below the device represents the head of the person holding the device. The VHF band is measured in a hand held position where the device is held in the user&#39;s hands with the distance from the head about two inches to represent a real world application.  FIGS. 13 through 15  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  100  in free space at UHF frequencies of 400 MHz, 450 MHz, and 512 MHz, respectively.  FIG. 16  illustrates a radiation pattern (phi zero degree plane) measured for the antenna assembly  100  in free space at a GPS frequency of 1575 MHz. 
     Generally,  FIGS. 12 through 16  show the radiation patterns for the antenna assembly at these various frequencies within the VHF, UHF, and GPS bands and the good efficiency of the antenna assembly  100 . The antenna assembly  100  has relatively broad bandwidths for the VHF, UHF, and GPS bands and allows multiple operating bands for wireless communications devices. 
       FIG. 17  illustrates another exemplary embodiment of an antenna assembly  500  embodying one or more aspects of the present disclosure. This exemplary embodiment has a design generally based on a monopole concept with multiple radiating elements. 
     As shown in  FIG. 17 , the antenna assembly  500  generally includes linear and helical radiators or radiating elements  504 ,  508 , and  512  coupled to a matching network  520  via an adapter  516  and contact spring  532 . In this example, the linear radiator  504  is a top loaded conducting wire located generally between and inside two spaced-apart helical radiators  508 ,  512 . The helical radiators  508 ,  512  are at or along opposite end portions of the linear radiator  504 . The linear radiator  504  extends along and/or is aligned generally with the central longitudinal axes of the helixes of the helical radiators  508 ,  512 . The top suspended helical radiator  508  may be coupled (e.g., via the coil form  544  ( FIGS. 20A and 20B ), etc.) such that the top suspended helical radiator  508  does not make direct galvanic contact with the linear radiator  504 . In operation, the top suspended helical radiator  508  parasitically couples to the linear radiator  504 . The antenna assembly  500  terminates with a connector  524  (e.g.,  50  Ohm connector, etc.) for connecting the antenna assembly  500  to a device (e.g., device housing  528  in  FIG. 18 , etc.), whereby the antenna assembly  500  depends to a ground plane of the device to excite. 
     As disclosed herein, this exemplary antenna assembly  500  is configured to be operable or to cover multiple frequency ranges or bands, including the UHF frequency band from about 380 MHz to about 527 MHz, the 7-800 MHz frequency band from about 764 MHz to about 870 MHz, and the GPS frequency of 1575 MHz. This particular antenna assembly  500  is configured to have the electrical lengths shown in  FIGS. 21A and 21B . 
     As shown in  FIG. 22 , the linear radiator  504  includes electrically conductive wire  506  (broadly, a first conductor) and a top loaded element  511  (broadly, a second conductor) at the end of the electrically conductive wire  506 . By way of example, the first conductor  506  of the linear radiator  504  may be formed from the electrically conducting wire at the center core of a coaxial cable. The top loaded element or second conductor  511  of the linear radiator  504  may comprise the braid soldered at the end of the coaxial cable. Accordingly, the braid of the coaxial cable may work as the second conductor  511 , while the center core of the coaxial cable works as the first conductor  506 . The coaxial cable&#39;s dielectric insulator  505  between the core and braid will operate to prevent direct contact therebetween. 
     In this example, the first conductor  506  is the center conductor of a conducting wire formed as a radiating element for the 7-800 MHz frequency band. The first and second conductors  506 ,  511  are galvanically coupled or connected (e.g., soldered, etc.) to each other at the top or end  509  of the linear radiator  504  as shown in  FIG. 22 . This configuration of the first and second conductors  506 ,  511  introduces a capacitance coupling to the antenna assembly  500  and creates another resonance for the antenna assembly  500  at the UHF band. The two conductor elements  506  and  511  also couple to each other such that the antenna assembly  500  is capable of simultaneously operating at the UHF and 7-800 MHz frequency bands at the same time. 
     As shown in  FIG. 21B , the electrical length of the first conductor  506  is about one quarter wavelength (λ/4) for the 7-800 MHz band. The electrical length is about one quarter wavelength (λ/4) for the UHF band when the first and second conductors  506 ,  511  are connected. In operation, the first conductor  506  introduces a single band resonance frequency for the 7-800 MHz frequency band, while the combination of the first and second conductors  506 ,  511  and matching network  520  introduce dual frequency resonance for the UHF and 7-800 MHz frequency bands. A loading gap  507  ( FIG. 22 ) between the first and second conductors  506 ,  511  changes the frequency ratio for the UHF and 7-800 MHz frequency bands and/or helps fine tune the frequency ratio between the UHF and 7-800 MHz frequency bands. 
     Alternative embodiments may include linear radiators having first and second conductors configured differently, including conductors formed from different materials other than coaxial cables and/or soldered braids at the end of the coaxial cables. Other exemplary embodiments may include a flexible electrically conducting wire or cable as the first conductor with a metal tube as the second conductor, which is crimped or soldered to the end of the wire or cable. In these example embodiments, an insulator jacket may be disposed or sandwiched between the metal tube and electrically conductive wire or cable. Examples of electrically conductive wires or cables that may be used include a speedometer cable, nickel titanium (NiTi) wire, among other suitable cables or wires. 
     With continued reference to  FIG. 17 , the coils of the top suspended helical radiating element  508  have a constant pitch such that the same distance is between the turns in the helical radiator  508 . Likewise, the coils of the bottom helical radiating element  512  include coils having a constant pitch, which, however, is less than the coils&#39; pitch of the top suspended helical radiating element. 
     A wide range of electrically conducting materials, preferably highly conductive materials, may be used for the helical radiators  508 ,  512 . By way of example, the helical radiators  508 ,  512  may be formed from copper wire, spring wire, copper/tin/nickel plating wire, enameled wire, among other suitable materials that may be configured to have a helical/spring configuration shown in  FIG. 17 . In addition, the coils of the helical radiators  508 ,  512  are configured (e.g., dual pitch, spacing, size, shape, etc.) in this example for specific frequency bands. Alternative embodiments may be configured for use with additional and/or different frequencies such as by varying the windings of the helical radiator coils. For example, other embodiments may include one or more helical radiators having coils with a non-constant pitch, etc. 
     In operation, the bottom helical radiating element  512  is responsive and resonant at the 7-800 MHz frequency band. As shown in  FIG. 21A , the electrical length of the bottom helical radiating element  512  is approximately equivalent to one quarter wavelength (λ/4) for 7-800 MHz band frequencies. The bottom helical radiating element  512  also introduces a second harmonic frequency for the GPS band. And, the electrical length of the bottom helical radiating element  512  is approximately equivalent to one half wavelength (λ/2) for GPS band frequencies. 
     In operation, the bottom helical radiating element  512  couples parasitically to the gap  507  of the top loaded conducting wire  504 . This coupling shifts the resonance of 7-800 MHz to a lower frequency while the UHF band resonance is maintained, such that the UHF and GPS bands resonate at the same time. The bottom helical radiating element  512  helps to fine tune the 7-800 MHz band. 
     In regard to the top suspended helical radiator  508 , parasitic coupling between the top loaded conducting wire  504  and the top suspended helical radiator  508  will shift the UHF band bandwidth so as to be resonant from 380 MHz to 527 MHz. But the top loaded conducting wire  504  is dominant when the antenna assembly  500  is operating within the UHF frequency bandwidth. The coupling between the top suspended helical radiator  508  and top loaded conducting wire  504  also increases the UHF electrical length such that electrical length of the entire antenna is approximately equivalent to one half wavelength (λ/2) for the UHF frequencies as shown in  FIG. 21A . 
     The coupling also improves 7-800 MHz bandwidths. For example, in this example embodiment, parasitic coupling of the top loaded conducting wire  504  and top suspended parasitic helical radiating element  508  broadens the bandwidth of the 7-800 MHz by introducing proximity resonance to the dominant resonance near 800 MHz as shown in  FIG. 24 . 
     The additional top suspended helical coil  508  helps to tilt up the 7-800 MHz frequency band and GPS band radiation patterns as shown in  FIGS. 31-33  (7-800 MHz frequency band) and  FIGS. 34-35  (GPS band), respectively. This improved the near horizon efficiency to at least 45% for the 7-800 MHz frequency band as shown in  FIG. 27 . In addition, the coupling of the top loaded conductor  504  and top suspended helical radiating element  508  also helps to tilt up the GPS radiation pattern ( FIGS. 34 and 35 ) to achieve more than 35% of open sky efficiency ( FIG. 27 ) for the GPS band in this example embodiment. 
     Multiple wavelengths are thus introduced by the bottom helical radiating element  512 , top suspended helical radiating element  508 , and the top loaded conducting wire  504 , including the UHF, 7-800 MHz, and GPS bands. Also, with the combination of the bottom helical radiating element  512 , top suspended helical radiating element  508 , and the top loaded conducting wire  504 , the antenna assembly  500  radiates in omnidirectional radiation patterns for the UHF and 7-800 MHz frequency bands as shown in  FIGS. 28-30  (UHF band) and  FIGS. 31-33  (7-800 MHz frequency band), respectively. Overall the average total efficiency and near horizon efficiency for the UHF and 7-800 MHz frequency band is more than 55% and 40% respectively (see  FIG. 27 ). 
       FIGS. 23A and 23B  illustrate an example matching network topology of a printed circuit board assembly that may be used in the antenna assembly  500 . In this example, the matching network  520  comprises lumped components  536  residing on front and back oppositely facing surfaces of the printed circuit board  538 . As shown in  FIGS. 17 and 18 , the matching network  520  is part of the antenna assembly  500  rather than the device to which the antenna assembly  500  will be connected. Accordingly, the antenna assembly  500  does not have to rely upon a matching network that is part of or internal to the device as the antenna assembly  500  instead includes its own (e.g., embedded, etc.) matching network  520 . Placing circuit board  538  and matching network  520  in the antenna assembly  500  allows more volume in the wireless device for other components, such as for increased circuitry to further enhance performance of the wireless device. 
     The matching network  520  may comprise one or more shunt or series capacitors and/or one or more shunt or series inductors depending on the matching network topology. For example, the circuit board  538  may comprise, for example, a two-element L shaped network of a capacitor and shunt inductor. Additionally, or alternatively, the circuit board  538  may also include other capacitors, inductors, resistors, or the like, as well as conductive traces. In operation, the matching network  520  helps to improve impedance matching for the 7-800 MHz frequency and GPS bands. For example, the matching network  520  may provide broadband impedance matching by generally providing a 50 ohm load across the operating frequencies of interest. 
     Moreover, the printed circuit board  538  and lumped components  536  thereon that provide the impedance matching of the matching network  520  may be configured such that they will be contained within or under a sheath or radome  540  as shown in  FIG. 20B . As shown in  FIG. 18 , the matching network  520  will be external to the device housing  528  when the antenna assembly  500  is coupled thereto. 
     In this particular example, the connector  524  of the antenna assembly  500  is a 50 ohm connector and is illustrated as a threaded connection. Alternative connectors may be used in other embodiments including a snap fit connection, etc. As shown in  FIG. 18 , the antenna assembly  500  may be threadedly connected to the device housing  528  such that the bulk of the antenna assembly or unit  500  is external to the device housing  528 . That is, the radiating elements  504 ,  508 ,  512  and circuit board  538  having the matching network  520  of the antenna assembly  500  are able to be entirely contained within or under the sheath  540  ( FIG. 20B ) and remain external to the wireless device housing  528 . Thus, the antenna assembly  500  is able to provide multiband operation in the UHF, 7-800, and GPS frequency bands without having to significantly increase the overall size or volume of the wireless device housing  528 . 
     By way of example only, the sheath  540  may have a length of about 180 millimeters and a diameter of about 14.5 millimeters along the portion disposed over the connector  524 . The numerical dimensions in this paragraph (as are all dimensions herein) are provided for illustrative purposes only, as the sheath and antenna components may be sized differently than disclosed herein depending on the particular frequencies desired or intended end use of the antenna assembly. 
     The sheath  540  may be overmolded or constructed via other suitable processes. For space considerations, the sheath  540  generally conforms to the outermost shape of the coils of the helical radiators  508 ,  512 . 
       FIGS. 20A and 20B  illustrate an exemplary manner by which the antenna assembly  500  and its various components may be assembled together. As shown in  FIG. 20A and 20B , the radiating elements  504 ,  508 ,  512 , connector  524 , and circuit board  538  may be coupled and assembled under the sheath  540  using the adapter  516 , spring contact or contact spring  532 , coil form  544  (e.g., insert molded coil form, etc.), sleeve  552  (e.g., tubular premold, etc.), contact  556  (e.g., contact pin, etc.), and insulator  560 . 
     As shown in  FIG. 20B , the helical radiators  508 ,  512  may be wound or disposed around the coil form  544  such that the coils of the helical radiators  508 ,  512  are positioned in grooves along the outer or exterior surface shown in  FIG. 20A . The coils of the bottom helical radiator  512  are also wound or disposed around a portion  517  of the adapter  516 . The coil form  544  is disposed over the top loaded conducting wire  504  as shown in  FIG. 20B . In this assembled state, the top suspended helical radiator  508  does not make direct galvanic contact with the top loaded conducting wire  504 . 
     The contact spring  532  includes a hook portion  534  (e.g., J-shaped or L-shaped hook portion, etc.) that extends through an opening or hole in the circuit board  538  as shown in  FIGS. 23A and 23B . The hook portion may terminate in a protrusion to provide additional resistance to pull through force tending to cause hook portion to pull out of the hole in the circuit board  538 . The hook portion is sized to fit in and through the hole in the circuit board  538  to provide a mechanical connection between the circuit board and the adapter  516 . For example, the coils of the spring contact  532  may be wrapped or wound about a portion of the adapter  516 . 
     Electrical connection may be made by various means to connect conductive traces on the circuit board  538  with the spring contact  532 , such as by soldering, a press fit connection, a stamped metal connection, etc. In this example embodiment, the contact spring  532  is shown as a separate component, but in other embodiments the contact spring  532  may comprise an integral piece or extension of the bottom helical radiating element  512 . 
     With continued reference to  FIGS. 20A and 20B , the insulator  560  electrically insulates the contact  556  (e.g., contact pin, etc.) from the connector  524 . The contact  556  is connected to the circuit board  538 , which is coupled to the adapter  516  within the tubular sleeve  552 . 
     Radio frequency power from a wireless device (e.g., two-way radio, etc.) may be provided to the antenna assembly  500  by the contact  556  through the circuit board  538  when the antenna assembly  500  is threaded connected to the device housing  528  (as shown in  FIG. 18 ). The connector or contact  556  is coupled to the circuit board  538 , such as by a soldered connection, a press fit connection, a snap fit connection, a crimp connection, etc. The circuit board  538  is coupled to the adapter  516  via the contact spring  532 . Accordingly, the contact  506  provides radio frequency power to the top loaded linear radiator  504  through circuit board  538 , spring contact  532 , and adapter  516 . 
     With continued reference to  FIGS. 20A and 20B , the sleeve  552  fits over the circuit board  538  and extends from connector  524  to the adapter  516  as shown in  FIG. 20B . In this example, the sleeve  552  may be coupled to the adapter  516  via a threaded connection via the threaded protruding portion of the adapter  516  and a threaded interior portion of the sleeve  552 . But this threading arrangement may be reversed and/or replaced by other means (e.g., friction fit, etc.) 
     In this exemplary embodiment, the use of the adapter  516  and sleeve  552  helps to reduce the impact to the circuit board  538  when the antenna assembly  500  is dropped as the adapter  516  helps loads/force to the sleeve  552 . In this exemplary way, the circuit board  538  can be protected from damage that might otherwise occur when the antenna assembly  500  is dropped. 
     In alternative embodiments, an antenna assembly may include a sheath  540 , antenna coil form  544 , and sleeve  552  made from a wide range of insulators/plastic materials for supporting the whole antenna structure. For example, an antenna assembly may be configured so as to be within a sheath where the interior of the antenna assembly is filled with air. In such example embodiment, the antenna&#39;s helical and linear radiators may be separated by a dielectric tubular member (e.g., straw, etc.) to prevent or at least inhibit direct electrical or galvanic contact between the helical and linear radiators. In such example, the antenna assembly may include at least one linear radiator aligned with or disposed at least partially along a longitudinal axis of at least one helical radiator. A dielectric tubular member may be disposed over the at least linear radiator. The at least one helical radiator may be external to the dielectric tubular member such that the dielectric tubular member prevents or at least inhibits direct electrical contact between the helical and linear radiators. A sheath may be disposed of the helical and linear radiators and dielectric tubular member. An interior of the sheath may be filled with air or other dielectric material. In alternative embodiments, an antenna assembly may not include any sheath. 
       FIGS. 24 through 35  provide analysis results measured for a prototype of the antenna assembly  500  shown in  FIG. 17 . These analysis results shown in  FIGS. 24 through 35  are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIGS. 24 through 26  are exemplary line graphs illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly  500 . In  FIG. 24 , the coupling effect from the top suspended helical radiating element  508  and the antenna&#39;s resonance for the GPS band can be seen. The data shown in  FIG. 25  was measured when the antenna assembly  500  was covered by the sheath  540  shown in  FIG. 19  and illustrates the GPS resonance shift to lower frequency due to load by sheath  540 . The data shown in  FIG. 26  was measured when the antenna assembly  500  was in the hand held position. Generally,  FIGS. 24 through 26  shows that the antenna assembly  500  is operable with relatively good/acceptable return loss and bandwidths for the UHF, 7-800, and GPS bands. 
       FIG. 27  is a table with performance summary data of measured efficiency and gain performance of the antenna assembly  500  shown in  FIG. 17  (in free space) for the UHF, 7-800, and GPS bands. Generally, this performance summary data shows that the antenna assembly  500  has relatively good gain/efficiency for the UHF, 7-800, and GPS bands, including good open sky efficiency of 36% for the GPS band. 
       FIGS. 28 through 35  illustrate radiation patterns measured for the antenna assembly  500 . The image at the center of each graph represents a device (e.g., two way radio, etc.) having the antenna assembly  500  mounted on top thereof. More specifically,  FIGS. 28 ,  29 , and  30  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  500  in free space at UHF frequencies of 400 MHz, 470 MHz, and 520 MHz, respectively.  FIGS. 31 ,  32 , and  33  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  500  in free space at frequencies of 764 MHz, 830 MHz, and 870 MHz, respectively, which are within the 7-800 MHz frequency band.  FIGS. 34 and 35  illustrate radiation patterns (phi zero degree plane and phi ninety degree plane, respectively) measured for the antenna assembly  500  in free space at the GPS frequency of 1575 MHz. Generally,  FIGS. 28 through 35  show the radiation patterns for the antenna assembly  500  at these various frequencies within the UHF, 7-800, and GPS bands and the good efficiency of the antenna assembly  500 . Accordingly, the antenna assembly  500  has relatively broad bandwidths for the UHF, 7-800, and GPS bands and allows multiple operating bands for wireless communications devices. 
       FIGS. 36A and 36B  illustrate another exemplary embodiment of an antenna assembly  600  embodying one or more aspects of the present disclosure. This exemplary embodiment has a design generally based on a monopole concept with multiple radiating elements. 
     As shown by  FIGS. 36A and 36B , the antenna assembly  600  generally includes linear and helical radiators or radiating elements  604 ,  606 ,  608 , and  612  coupled to a matching network  620  via an adapter  616  and contact spring  632 . In this example, the linear radiators  604 ,  606  are located or suspended generally inside the helical radiators  608 ,  612 . The linear radiators  604 ,  606  extend along and/or are aligned generally with the central longitudinal axes of the helixes of the helical radiators  608 ,  612 . 
       FIG. 36A  illustrates first and second spacers or insulators  607 ,  609  for mechanically coupling (e.g., affixes, attaches, etc.) the first and second linear radiators  604 ,  606  to the adapter  616  and each other. The first spacer  607  mechanically couples the first linear radiator  604  to the adapter  616 . The second spacer  609  mechanically couples end portions of the first and second linear radiators  604 ,  606  together. In addition, the spacers  607 ,  609  are configured to prevent the first and second linear radiators  604 ,  606  from making direct galvanic contact with each other and from making direct galvanic contact with the helical radiators  608 ,  612 . The use of the first and second linear radiators  604 ,  606  and spacers  607 ,  609  may allow the antenna assembly  600  to use a relatively small diameter helical radiator  608 , which, in turn, may allow the antenna assembly  600  to be more flexible with a relatively thin profile. 
     The linear radiators  604 ,  606  may be disposed within a coil form similar to what is disclosed for other exemplary embodiments, such as coil form  744  ( FIG. 45 ). The helical radiators  608 ,  612  may be disposed about the exterior of the coil form such that the linear radiators  604 ,  606  do not make direct galvanic contact with the helical radiators  608 ,  612 . In operation, the helical radiators  608 ,  612  parasitically couple to the linear radiators  604 ,  606 . The antenna assembly  600  terminates with a connector  624  (e.g., 50 Ohm connector, etc.) for connecting the antenna assembly  600  to a device similar to the manner in which the connector  524  connects to the device housing  528  in  FIG. 18 . When connected to a device, the antenna assembly  600  may depend to a ground plane of the device to excite. 
     As disclosed herein, this exemplary antenna assembly  600  is configured to be operable or to cover multiple frequency ranges or bands, including the VHF frequency band from about 136 MHz to about 174 MHz, the UHF frequency band from about 380 MHz to about 527 MHz, the 7-800 MHz frequency band from about 764 MHz to about 870 MHz, and the GPS frequency of 1575 MHz. The matching network  620  is operable to help broaden the bandwidth of the VHF band for resonance from 136 MHz to 174 MHz. Accordingly, the antenna assembly  600  is configured for at least quad band operation in this example. 
     With continued reference to  FIGS. 36A and 36B , the helical radiators  608 ,  612  are dual pitch helical coil radiators or springs having narrower and wider pitch coils along their respective lower and upper portions. The helical radiator  608  has narrower and wider pitch coils  613 ,  614 , respectively, along its respective upper and lower portions. The helical radiator  612  has narrower and wider pitch coils  615 ,  619 , respectively, along its respective upper and lower portions. 
     The dual pitch helical radiating element  608  corresponds to the VHF band. The narrower or closer pitch of the upper coils  613  of the helical radiator  608  helps to increase the gain at lower frequency(ies), such as at 136 MHz. As shown in  FIG. 37A , the total electrical length of the upper helical radiator  608  and the adaptor  616  is about one quarter wavelength (λ/4) for the VHF band. 
     Adding the dual pitch helical radiating element  612  at the bottom of the antenna assembly  600  allows the antenna assembly  600  to operate at UHF, 7-800 MHz, and GPS bands. The dual pitch helical radiator  612  is wound or disposed around a portion  617  of the adapter  616 , and makes metal contact to the adaptor  616 , such as, for example, by means of soldering. The narrow or close pitch coils  615  of the helical radiator  612  correspond to the UHF and 7-800 MHz bands. As shown in  FIG. 37B , the electrical length of the narrow pitch helical radiator coils  615  is about one quarter wavelength (λ/4) for the UHF band and about one half wavelength (λ/2) for the 7-800 MHz band. The wide or loose pitch coils  619  of the bottom helical radiator  612  correspond to the 7-800 MHz and GPS bands. As also shown in  FIG. 37B , the electrical length of the wide pitch helical radiator coils  619  is about one quarter wavelength (λ/4) for the 7-800 MHz band and about one half wavelength (λ/2) for the GPS band. Proper tuning at/of the close pitch coils  615  of the bottom helical radiating element  612  will help to broaden the bandwidth of the 7-800 MHz band with its second harmonic resonance at 7-800 MHz. The wide or loose pitch coils  619  of the bottom helical radiating element  612  creates another resonance at the GPS band with its second harmonic resonance frequency. The coils  615  and  619  of the bottom helical radiator  612  may be configured in various ways to obtain the same or similar results stated above. By way of example, the bottom helical radiating element  612  may comprise a helical spring in which the wire turning orientation of the coils  615  and  619  are both clockwise or both counterclockwise. Or, for example, the wire turning orientation of the coils  615  may be counterclockwise, while the wire turning orientation of the coil  619  may be clockwise. As a further example, the wire turning orientation of the coils  615  may be clockwise, while the wire turning orientation of the coil  619  may be counterclockwise. 
     In this example, the first linear radiator  604  (e.g., bottom suspended wire, etc.) is inside the helical radiating elements  608 . The spacer/insulator  607  is between and separates the adaptor  616  and first linear radiator  604 . With this configuration, the bottom helical radiating element  612  parasitically couples to the linear radiator  604 . Indirectly, this coupling helps to shift the UHF and 7-800 MHz bands to lower frequencies and broadens the bandwidth for the 7-800 MHz band. The electrical length of the linear radiator  604  is about one quarters wavelength (λ/4) for the 7-800 MHz band. With the parasitic coupling, the combined electrical length of the linear radiator  604  and the narrow pitch coils  615  of the bottom helical radiating element  612  is about three quarter wavelength (3λ/4) for the 7-800 MHz frequency band as shown in  FIG. 37A . 
     The second linear radiator  606  (e.g., top suspended wire, etc.) is above the first linear radiator  604  (e.g., bottom suspended wire, etc.). The spacer/insulator  609  is between and separates the first and second linear radiators  604 ,  606 . This configuration indirectly creates a parasitic coupling between the first and second linear radiators  604 ,  606 . Indirectly, this coupling increase the electrical length of the first or bottom linear radiator  604  to one quarter wavelength (λ/4) for the UHF band. The increased wavelength helps to improve the bandwidth of the UHF band of the antenna assembly (see  FIG. 38 ). 
     With continued reference to  FIGS. 36A and 36B , the helical radiator  608  in this exemplary embodiment is a dual pitch helical coil radiator or spring having narrower and wider pitch coils  613 ,  614 , respectively, along the respective bottom and top portions of the helical radiator  612 . In operation, the helical radiator  608  in this exemplary embodiment is more responsive at VHF band. Accordingly, multiple resonant frequencies are excited by the interaction of the dual pitch helical radiator  608  and parasitic linear radiators  604 ,  606 . Indirectly, this coupling helps to maintain the resonant frequencies of UHF band. As shown in  FIG. 37B , the overall electrical length of the helical radiator  608  is about one quarter wavelength (λ/4) for the UHF band. 
     Multiple wavelengths are introduced by the linear and helical radiators  604 ,  606 ,  608 , and  612 , including the VHF, UHF, 7-800 MHz, and GPS bands. Also, the coupling of these radiators  604 ,  606 ,  608 , and  612  allows the antenna assembly  600  to have an omnidirectional radiation pattern across the VHF, UHF, and 7-800 MHz frequency bands as can be seen in  FIGS. 40 through 42 . 
     In exemplary embodiments, the linear radiators  604 ,  606  may comprise flexible electrically conducting wires or cables. Examples of electrically conductive wires or cables that may be used as the linear radiators  604 ,  608  include a speedometer cable, nickel titanium (NiTi) wire, among other suitable cables or wires. Other electrically conductive materials and/or configurations may also be used for the linear radiators  604 ,  608 . 
     A wide range of electrically conducting materials, preferably highly conductive materials, may be used for the helical radiators  608 ,  612 . By way of example, the helical radiators  608 ,  612  may be formed from copper wire, spring wire, copper/tin/nickel plating wire, enameled wire, among other materials that may be configured to have the helical/spring configuration shown in  FIG. 36A . In addition, the coils of the helical radiators  608 ,  612  are configured (e.g., dual pitch, spacing, size, shape, etc.) in this example embodiment for the specific frequency bands disclosed herein. Alternative embodiments may be configured for use with additional and/or different frequencies such as by varying the windings of the helical radiator coils. For example, other embodiments may include one or more helical radiators having coils with a constant pitch or with more than two different pitches and/or with a tapering pitch such that the coil has an upper or lower section wider than the other section. 
     The matching network  620  of the antenna assembly  600  may be identical or substantially similar to the matching network  120  shown in  FIGS. 8A and 8B  and described above. Or, for example, the matching network  620  of the antenna assembly  600  may be identical or substantially similar to the matching network  520  shown in  FIGS. 23A and 23B  and described above. Alternative matching networks may also be used besides those shown in  FIGS. 8A ,  8 B,  23 A, and  23 B. 
     In this exemplary embodiment, the matching network  620  comprises lumped components residing on front and back oppositely facing surfaces of a printed circuit board  638 . As shown in  FIG. 36B , the matching network  620  is part of the antenna assembly  600  rather than the device to which the antenna assembly  600  will be connected. Accordingly, the antenna assembly  600  does not have to rely upon a matching network that is part of or internal to the device as the antenna assembly  600  instead includes its own (e.g., embedded, etc.) matching network  620 . Placing circuit board  638  and matching network  620  in the antenna assembly  600  and external to the device housing allows more volume in the wireless device for other components, such as for increased circuitry to further enhance performance of the wireless device. 
     The matching network  620  may comprise one or more shunt or series capacitors and/or one or more shunt or series inductors depending on the matching network topology. For example, the matching network circuit board may comprise, for example, a two-element L shaped network of a capacitor and shunt inductor. Additionally, or alternatively, the circuit board may also include other capacitors, inductors, resistors, or the like, as well as conductive traces. In operation, the matching network  620  may provide broadband impedance matching by generally providing a  50  ohm load across the operating frequencies of interest. The printed circuit board  638  and lumped components thereon that provide the impedance matching of the matching network  620  may be configured such that they will be contained within or under a sheath or radome such as the sheet  740  as shown in  FIG. 46B . 
     In this particular example, the connector  624  of the antenna assembly  600  is a  50  ohm connector and is illustrated as a threaded connection. Alternative connectors may be used in other embodiments including a snap fit connection, etc. The antenna assembly  600  may be threadedly connected to a device housing such that the bulk of the antenna assembly or unit  600  is external to the device housing. That is, the radiating elements  604 ,  606 ,  608 ,  612  and circuit board  638  having the matching network  620  of the antenna assembly  600  are able to be entirely contained within or under the sheath and remain external to the wireless device housing. Thus, the antenna assembly  600  is able to provide multiband operation in the VHF, UHF, 7-800, and GPS frequency bands without having to significantly increase the overall size or volume of the wireless device housing. 
       FIGS. 36A and 36B  illustrates an exemplary manner by which the antenna assembly  600  and its various components may be assembled together. By way of example only, the antenna assembly  600  may have some components similar or identical to the corresponding components of another antenna assembly, such as the sheath  740 , coil form  744  (e.g., insert molded coil form, etc.), contact  756  (e.g., contact pin, etc.), and insulator  760  of antenna assembly  700 . 
     As shown in  FIGS. 36A and 36B , the helical radiator  612  is wound or disposed around the portion  617  of the adapter  616 , and makes metal contact to the adaptor  616 , such as, for example, by means of soldering. And also, the helical radiator  612  may be wound or disposed around the sleeve  652  (e.g., tubular premold, etc.). The lower wider pitch coils  619  of the helical radiator  612  are positioned in grooves along the exterior or outer surface of the sleeve  652  (e.g., tubular premold, etc.). The upper narrower pitch coils  615  of the helical radiator  612  are wound or disposed around the portion  617  of the adapter  616 . In some exemplary embodiments, a coil form (e.g., coil form  744 , etc.) may be disposed over the linear radiators  604 ,  606 . In such embodiments, the coils  613 ,  614  of the helical radiator  608  may be positioned in grooves along the exterior or outer surface of the coil form. In the assembled state, the helical radiators  608 ,  612  do not make direct galvanic contact with the linear radiators  604 ,  606 , which contact is prevented or inhibited by the spacers  607 ,  609  and coil form. 
     The contact spring  632  includes a hook portion (e.g., J-shaped or L-shaped hook portion, etc.) that extends through an opening or hole in the circuit board  638 , see for example  FIGS. 8A and 8B  or  FIGS. 23A and 23B . The hook portion may terminate in a protrusion to provide additional resistance to pull through force tending to cause hook portion to pull out of the hole in the circuit board  638 . The hook portion is sized to fit in and through the hole in the circuit board  638  to provide a mechanical connection between the circuit board  638  and the adapter  616 . For example, the coils of the spring contact  632  may be wrapped or wound about a portion of the adapter  616 . 
     Electrical connection may be made by various means to connect conductive traces on the circuit board  638  with the spring contact  632 , such as by soldering, a press fit connection, a stamped metal connection, etc. In this example embodiment, the contact spring  632  is shown as a separate component, but in other embodiments the contact spring  632  may comprise an integral piece or extension of the bottom helical radiating element  612 . 
     An insulator may electrically insulates a contact (e.g., contact pin, etc.) from the connector  624 . The contact may be connected to the circuit board  638 , which is coupled to the adapter  616  within the tubular sleeve  652 . Radio frequency power from a wireless device (e.g., two-way radio, etc.) may be provided to the antenna assembly  600  by the contact through the circuit board  638  when the antenna assembly  600  is threadedly connected to the device housing (see, e.g.,  FIG. 18 ). The connector or contact is coupled to the circuit board  638 , such as by a soldered connection, a press fit connection, a snap fit connection, a crimp connection, etc. The circuit board  638  is coupled to the adapter  616  via the contact spring  632 . Accordingly, the contact may thus provide radio frequency power to the linear radiator through circuit board  638 , spring contact  632 , and adapter  616 . 
     With continued reference to  FIGS. 36A and 36B , the sleeve  652  fits over the circuit board  638  and extends from connector  624  to the adapter  616 . In this example, the sleeve  652  may be coupled to the adapter  616  via a threaded connection via the threaded protruding portion of the adapter  616  and a threaded interior portion of the sleeve  652 . But this threading arrangement may be reversed and/or replaced by other means (e.g., friction fit, etc.) 
     In this exemplary embodiment, the use of the adapter  616  and sleeve  652  helps to reduce the impact to the circuit board  638  of the matching network  620  if the antenna assembly  600  is dropped, as the adapter  616  helps loads/force to the sleeve  652 . In this exemplary way, the circuit board  638  can be protected from damage that might otherwise occur when the antenna assembly  600  is dropped. 
     In alternative embodiments, an antenna assembly may include a sheath, antenna coil form, and sleeve  652  made from a wide range of insulators/plastic materials for supporting the whole antenna structure. For example, an antenna assembly may be configured so as to be within a sheath where the interior of the antenna assembly is filled with air. In such example embodiment, the antenna&#39;s helical and linear radiators may be separated by a dielectric tubular member (e.g., straw, etc.) to prevent or at least inhibit direct electrical or galvanic contact between the helical and linear radiators. In such example, the antenna assembly may include at least one linear radiator aligned with or disposed at least partially along a longitudinal axis of at least one helical radiator. A dielectric tubular member may be disposed over the at least linear radiator. The at least one helical radiator may be external to the dielectric tubular member such that the dielectric tubular member prevents or at least inhibits direct electrical contact between the helical and linear radiators. A sheath may be disposed of the helical and linear radiators and dielectric tubular member. An interior of the sheath may be filled with air or other dielectric material. In alternative embodiments, an antenna assembly may not include any sheath. 
       FIGS. 38 through 43  provide analysis results measured for a prototype of the antenna assembly  600  shown in  FIG. 36A . These analysis results shown in  FIGS. 38 through 43  are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIG. 38  is an exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly  600  in a hand held position. Generally,  FIG. 38  shows that the antenna assembly  600  is operable with relatively good/acceptable return loss and bandwidths for the VHF, UHF, 7-800, and GPS bands. 
       FIG. 39  includes tables with measured efficiency and gain in decibels (dB) for the antenna assembly  600  for the VHF band (azimuth plane—hand held position) and for the UHF, 7-800, and GPS bands (in free space and hand held position). Generally, this performance summary data shows that the antenna assembly  600  has relatively good gain/efficiency for the UHF, 7-800, and GPS bands. 
       FIGS. 40 through 43  illustrate radiation patterns measured for the antenna assembly  600 . The image at the center of each graph represents a device (e.g., two way radio, etc.) having the antenna assembly  600  mounted on top thereof. More specifically,  FIG. 40  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  600  in a hand held position at a VHF frequency of 155 MHz.  FIG. 41  illustrates a radiation patterns (azimuth plane) measured for the antenna assembly  600  in free space and handheld at a UHF frequency of 470 MHz.  FIG. 42  illustrate a radiation pattern (azimuth plane) measured for the antenna assembly  600  in free space and hand held at a frequency of 806 MHz, which is within the 7-800 MHz frequency band.  FIG. 43  illustrates a radiation patterns (phi zero degree plane) measured for the antenna assembly  600  in free space and hand held at the GPS frequency of 1575 MHz. Generally,  FIGS. 40 through 43  show the radiation patterns for the antenna assembly  600  at these various frequencies within the VHF, UHF, 7-800, and GPS bands and the good efficiency of the antenna assembly  600 . Accordingly, the antenna assembly  600  has relatively broad bandwidths for the VHF, UHF, 7-800, and GPS bands and allows multiple operating bands for wireless communications devices. 
     In this exemplary embodiment, the antenna assembly  600  may thus be configured to achieve multiband operation for frequencies associated with or falling within the VHF band from 136 MHz to 174 MHz, the entire UHF band from 380 MHz to 527 MHz, 7-800 MHz frequency band from 764 MHz to 870 MHz), and a GPS frequency of 1575 MHz. The antenna assembly  600  may be configured to achieve this multiband operation with a voltage standing wave ratio (VSWR) less than three, relatively good gain and efficiency for wireless applications while having a relatively thin profile. 
       FIG. 44  illustrates another exemplary embodiment of an antenna assembly  700  embodying one or more aspects of the present disclosure. This exemplary embodiment has a design generally based on a monopole concept with multiple radiating elements. 
     As shown in  FIG. 44 , the antenna assembly  700  generally includes linear and helical radiators or radiating elements  704 ,  708 , and  712  coupled to a matching network  720  via an adapter  716  and contact spring  732 . In this example, the linear radiator  704  is a top loaded conducting wire located generally inside the helical radiators  708 ,  712 . The linear radiator  704  extends along and/or is aligned generally with the central longitudinal axes of the helixes of the helical radiators  708 ,  712 . As shown in  FIGS. 45 and 46B , the linear radiator  704  is disposed within a coil form  744 . As shown in  FIG. 46B , the helical radiator  712  is disposed about the exterior of the coil form  744  and within the antenna sheath or radome  740 , such that the helical radiator  712  does not make direct contact with the linear radiator  704 , helical radiator  708 , and adaptor  716 . In operation, the helical radiators  708 ,  712  parasitically couple to the linear radiator  704 . The antenna assembly  700  terminates with a connector  724  (e.g.,  50  Ohm connector, etc.) for connecting the antenna assembly  700  to a device similar to the manner in which the connector  524  connects to the device housing  528  in  FIG. 18 . When connected to a device, the antenna assembly  700  may depend to a ground plane of the device to excite. 
     As disclosed herein, this exemplary antenna assembly  700  is configured to be operable or to cover multiple frequency ranges or bands, including the VHF frequency band from about 136 MHz to about 174 MHz, the UHF frequency band from about 380 MHz to about 527 MHz, the 7-800 MHz frequency band from about 764 MHz to about 870 MHz, and the GPS frequency of 1575 MHz. Accordingly, the antenna assembly  700  is configured for at least quad band operation in this example. 
     As shown in  FIGS. 45 and 49 , the linear radiator  704  includes electrically conductive wire  706  (broadly, a first conductor) and a top loaded element  711  (broadly, a second conductor) at or towards the end of the electrically conductive wire  706 . By way of example, the first conductor  706  of the linear radiator  704  may be formed from the electrically conducting wire at the center core of a coaxial cable. The top loaded element or second conductor  711  of the linear radiator  704  may comprise the braid soldered at the end of the coaxial cable  709 . Accordingly, the braid of the coaxial cable may work as the second conductor  711 , while the center core of the coaxial cable works as the first conductor  706 . The coaxial cable&#39;s dielectric insulator  705  between the core and braid will operate to prevent direct contact therebetween. 
     In this example, the antenna design is based on a quarter-wave length for low band and high band. The linear radiator  704  corresponds to the UHF and 7-800 MHz frequency bands. As shown in  FIG. 47C , the electrical length of the first conductor  706  of the linear radiator  704  is about one quarter wavelength (λ/4) for the 7-800 MHz band. With the parasitic coupling, the combined electrical length of the first conductor  706  and the second conductor  711  is about one quarter wavelength (λ/4) for the UHF band as also shown in  FIG. 47C . The helical radiating element  708  (e.g., dual pitch spring coil, etc.) corresponds to the VHF and UHF bands. As shown in  FIG. 47A , the electrical length of the helical radiator  708  is about one quarter wavelength (λ/4) for the VHF band, and the electrical length of the wider pitch coils  714  of the helical radiator  708  is about one quarter wavelength (λ/4) for the UHF band. 
     The bottom helical radiating element  712  (e.g., bottom suspended coil, etc.) corresponds to the 7-800 MHz band and is resonant from about 764 MHz to about 870 MHz when parasitically coupled to the linear radiator  704 . In operation (see  FIG. 52 ), the bottom helical radiating element  712  parasitically couples to the first conductor  706  (e.g., inner electrically conducting wire, etc.) of linear radiator  704  to maintain and/or broaden the bandwidth for the UHF band to be resonant from about 380 MHz to about 527 MHz (see  FIG. 52 ). Indirectly, the parasitic coupling of the bottom helical radiating element  712  and the first conductor  706  has a combined electrical length of about one quarter wavelength (λ/4) for the UHF band as shown in  FIG. 47B . Parasitic coupling of the bottom helical radiating element  712  and the second conductor  711  of the linear radiator  704  broadens the bandwidth of the 7-800 MHz band by introducing proximity resonance to the dominant resonance near 800 MHz. Accordingly, the parasitic coupling of the bottom helical radiating element  712  and the second conductor  711  has a combined electrical length of about three quarters wavelength (3λ/4) for the 7-800 MHz band as shown in  FIG. 47B . 
     The matching network  720  is operable to help broaden the bandwidth of the VHF band for resonance from 136 MHz to 174 MHz. The matching network  740  also introduces resonance at a GPS frequency of about 1575 MHz when it loads with an adaptor on the top. Multiple wavelengths are introduced by the linear and helical radiators  704 ,  708 ,  712 . In this exemplary embodiment, the matching network  720  couples with the bottom helical radiating element  712 , helical radiator  708 , and the linear radiator  704  to maintain the GPS frequency. 
     In this example, the first conductor  706  is the center conductor of a conducting wire formed as a radiating element for high band (7-800 MHz in this example). The first and second conductors  706 ,  711  are galvanically coupled or connected (e.g., soldered, etc.) to each other at the top or end  709  of the linear radiator  704  as shown in  FIG. 49 . This configuration of the first and second conductors  706 ,  711  introduces a capacitance coupling to the antenna assembly  700  and creates another resonance for high band for the antenna assembly  700  at the UHF frequency band. The two conductor elements  706  and  711  also couple to each other such that the antenna assembly  700  is capable of simultaneously operating at the UHF band and 7-800 MHz frequency band at the same time. 
     With reference to  FIG. 47B , the electrical length of the first conductor  706  is about one quarter wavelength (λ/4) for the 7-800 MHz frequency band. The electrical length is about one quarter wavelength (λ/4) for the UHF band when the first and second conductors  706 ,  711  are connected. In operation, the first conductor  706  introduces a single band resonance frequency for the 7-800 MHz frequency band, while the combination of the first and second conductors  706 ,  711  and matching network  720  introduce dual frequency resonance for the UHF and 7-800 MHz frequency bands. A loading gap  707  ( FIG. 49 ) between the first and second conductors  706 ,  711  changes the frequency ratio for the UHF band and 7-800 MHz frequency band and/or helps fine tune the frequency ratio between the UHF band and 7-800 MHz frequency band. 
     Alternative embodiments may include linear radiators having first and second conductors configured differently, including conductors formed from different materials other than coaxial cables and/or soldered braids at the end of the coaxial cables. Other exemplary embodiments may include a flexible electrically conducting wire or cable as the first conductor with a metal tube as the second conductor, which is crimped or soldered to the end of the wire or cable. In these example embodiments, an insulator jacket may be disposed or sandwiched between the metal tube and electrically conductive wire or cable. Examples of electrically conductive wires or cables that may be used include a speedometer cable, nickel titanium (NiTi) wire, among other suitable cables or wires. 
     In addition, other electrically conductive materials and/or configurations may be used for the first and/or second conductors of the linear radiator. For example, the second conductor may be formed from a spring or single wire instead of a soldered coaxial cable braid or metal tube. To this end,  FIGS. 50 and 51  illustrate further examples of linear radiators  804  and  904 , respectively, that may be used with the antenna assembly  700  with similar results in antenna performance. 
     As shown in  FIG. 50 , the linear radiator  804  includes a first conductor  806  and a second conductor  811  connected to each other at or towards the top or end  809  of the first conductor  806 . In this example, the second conductor  811  is a single straight portion of electrically conductive wire that extends parallel to and back along the first conductor  806 . 
     As shown in  FIG. 51 , the linear radiator  904  includes a first conductor  906  and a second conductor  911  connected to each other at or towards the top or end  909  of the first conductor  906 . In this example, the second conductor  911  is a spring or helical conductor that extends back along the first conductor  906  such that the coils of the spring  911  coil or wind generally about the length of the first conductor  906 . 
     With continued reference to  FIGS. 44 and 45 , the helical radiator  708  in this exemplary embodiment is a dual pitch helical coil radiator or spring having narrower and wider pitch coils  713 ,  714 , respectively, along the respective bottom and top portions of the helical radiator  712 . In operation, the lower coils  714  having the wider pitch are more responsive and resonant at the UHF band and are approximately equivalent to one quarter wavelength (λ/4) for the UHF band frequencies. The upper coils  713  having the narrower or closer pitch are operable for introducing another resonance at the VHF band. 
     A wide range of electrically conducting materials, preferably highly conductive materials, may be used for the helical radiators  708  and  712 . By way of example, the helical radiators  708  and/or  712  may be formed from copper wire, spring wire, copper/tin/nickel plating wire, enameled wire, among other materials that may be configured to have the helical/spring configuration shown in  FIG. 44 . In addition, the coils of the helical radiators  708  and  712  are configured (e.g., dual pitch, spacing, size, shape, etc.) in this example for specific frequency bands. Alternative embodiments may be configured for use with additional and/or different frequencies such as by varying the windings of the helical radiator coils. For example, other embodiments may include one or more helical radiators having coils with a constant pitch or with more than two different pitches and/or with a tapering pitch such that the coil has an upper or lower section wider than the other section. In addition,  FIG. 48  illustrates examples of flat pattern profiles that may be used for the helical radiating element  712  before it is wrapped or coiled. 
     In operation, the bottom helical radiating element  712  is responsive and resonant at the 7-800 MHz frequency band. The electrical length of the bottom helical radiating element  712  is approximately equivalent to one quarter wavelength (λ/4) for the 7-800 MHz band frequencies ( FIG. 47B ). The bottom helical radiating element  712  may also introduce a second harmonic frequency for the GPS band. And, the electrical length of the bottom helical radiating element  712  may be approximately equivalent to one half wavelength (λ/2) for GPS band frequencies. In operation, the bottom helical radiating element  712  couples parasitically to the gap  707  of the top loaded conducting wire  704 . This coupling shifts the resonance of 7-800 MHz to a lower frequency while the UHF band resonance is maintained, such that the UHF and GPS bands resonate at the same time. The bottom helical radiating element  712  helps to fine tune the 7-800 MHz band. Also, coupling between the bottom helical radiator  712  and second linear radiator  711  of the top loaded conducting wire  704  also increases the UHF electrical length such that electrical length of the entire antenna is approximately equivalent to one quarter wavelength (λ/4) for the UHF frequencies. 
     Multiple wavelengths are introduced by the linear and helical radiators  704 ,  708 , and  712 , including the VHF, UHF, 7-800, and GPS bands. Also, the coupling of these radiators  704 ,  708 , and  712  allows the antenna assembly  700  to have an omnidirectional radiation pattern across the VHF, UHF, and 7-800 MHz frequency bands as can be seen in  FIGS. 54 through 60 . Also, the linear radiator&#39;s first conductor  706  and second conductor  711  also helps to tilt up the GPS radiation pattern ( FIGS. 61 and 62 ) such that the antenna assembly  700  achieves more than 35% of open sky efficiency ( FIG. 53 ) for the GPS band in this example embodiment. 
     The matching network  720  of the antenna assembly  700  may be identical or substantially similar to the matching network  120  shown in  FIGS. 8A and 8B  and described above. Or, for example, the matching network  720  of the antenna assembly  700  may be identical or substantially similar to the matching network  520  shown in  FIGS. 23A and 23B  and described above. Alternative matching networks may also be used besides those shown in  FIGS. 8A ,  8 B,  23 A, and  23 B. 
     In this exemplary embodiment, the matching network  720  comprises lumped components residing on front and back oppositely facing surfaces of a printed circuit board  738 . As shown in  FIGS. 44 and 46B , the matching network  720  and circuit board  738  are part of the antenna assembly  700  rather than the device to which the antenna assembly  700  will be connected. Accordingly, the antenna assembly  700  does not have to rely upon a matching network that is part of or internal to the device as the antenna assembly  700  instead includes its own (e.g., embedded, etc.) matching network  720 . Placing circuit board  738  and matching network  720  in the antenna assembly  700  and external to the device housing allows more volume in the wireless device for other components, such as for increased circuitry to further enhance performance of the wireless device. 
     The matching network  720  may comprise one or more shunt or series capacitors and/or one or more shunt or series inductors depending on the matching network topology. For example, the matching network circuit board may comprise, for example, a two-element L shaped network of a capacitor and shunt inductor. Additionally, or alternatively, the circuit board may also include other capacitors, inductors, resistors, or the like, as well as conductive traces. In operation, the matching network  720  may provide broadband impedance matching by generally providing a  70  ohm load across the operating frequencies of interest. The printed circuit board  738  and lumped components thereon that provide the impedance matching of the matching network  720  may be configured such that they will be contained within or under a sheath or radome  740  as shown in  FIGS. 46A and 46B . 
     In this particular example, the connector  724  of the antenna assembly  700  is a 50 ohm connector and is illustrated as a threaded connection. Alternative connectors may be used in other embodiments including a snap fit connection, etc. The antenna assembly  700  may be threadedly connected to a device housing such that the bulk of the antenna assembly or unit  700  is external to the device housing. That is, the radiating elements  704 ,  708 ,  712  and circuit board  738  having the matching network  720  of the antenna assembly  700  are able to be entirely contained within or under the sheath  740  ( FIGS. 46A and 46B ) and remain external to the wireless device housing. Thus, the antenna assembly  700  is able to provide multiband operation in the VHF, UHF, 7-800, and GPS frequency bands without having to significantly increase the overall size or volume of the wireless device housing. 
     By way of example only, the sheath  740  may have a length of about 200 millimeters and a diameter of about 14.5 millimeters along the portion disposed over the connector  724 . The numerical dimensions in this paragraph (as are all dimensions herein) are provided for illustrative purposes only, as the sheath and antenna components may be sized differently than disclosed herein depending on the particular frequencies desired or intended end use of the antenna assembly. 
     The sheath  740  may be overmolded or constructed via other suitable processes. For space considerations, the sheath  740  generally conforms to the outermost shape of the coils of the helical radiators  708 ,  712 . 
       FIGS. 45 ,  46 A, and  46 B illustrate an exemplary manner by which the antenna assembly  700  and its various components may be assembled together. As shown in  FIG. 46B , the radiating elements  704 ,  708 ,  712 , connector  724 , and the circuit board  738  may be coupled and assembled under the sheath  740  using the adapter  716 , spring contact or contact spring  732 , coil form  744  (e.g., insert molded coil form, etc.), sleeve  752  (e.g., tubular premold, etc.), contact  756  (e.g., contact pin, etc.), and insulator  760 . 
     The helical radiator  708 ,  712  may be wound or disposed around the coil form  744 . The coils of the helical radiator  708  are positioned in grooves ( FIG. 45 ) along the outer or exterior surface of the coil form  744  shown in  FIG. 46B . The coils of the bottom helical radiator  712  are also wound or disposed around a portion of the adapter  716  without direct galvanic contact to the adapter  716 . The coil form  744  is disposed over the top loaded conducting wire  704  as shown in  FIG. 46B . In this assembled state, the helical radiators  708 ,  712  do not make direct galvanic contact with the top loaded conducting wire  704 . 
     The contact spring  732  includes a hook portion (e.g., J-shaped or L-shaped hook portion, etc.) that extends through an opening or hole in the circuit board  738 , see for example  FIGS. 8A and 8B  or  FIGS. 23A and 23B . The hook portion may terminate in a protrusion to provide additional resistance to pull through force tending to cause hook portion to pull out of the hole in the circuit board  738 . The hook portion is sized to fit in and through the hole in the circuit board  738  to provide a mechanical connection between the circuit board  738  and the adapter  716 . For example, the coils of the spring contact or contact spring  732  may be wrapped or wound about a portion of the adapter  716 . 
     Electrical connections may be made by various means to connect conductive traces on the circuit board  738  with the contact spring  732 , such as by soldering, a press fit connection, a stamped metal connection, etc. In this example embodiment, the contact spring  732  is shown as a separate component, but in other embodiments the contact spring  732  may comprise an integral piece. 
     With continued reference to  FIGS. 45 and 46B , the insulator  760  electrically insulates the contact  756  (e.g., contact pin, etc.) from the connector  724 . The contact  756  is connected to the circuit board  738 , which is coupled to the adapter  716  within the tubular sleeve  752 . 
     Radio frequency power from a wireless device (e.g., two-way radio, etc.) may be provided to the antenna assembly  700  by the contact  756  through the circuit board  738  when the antenna assembly  700  is threadedly connected to the device housing (see, e.g.,  FIG. 18 ). The connector or contact  756  is coupled to the circuit board  738 , such as by a soldered connection, a press fit connection, a snap fit connection, a crimp connection, etc. The circuit board  738  is coupled to the adapter  716  via the contact spring  732 . Accordingly, the contact  756  provides radio frequency power to the radiators  704 ,  708  through the circuit board  738 , contact spring  732 , and adapter  716 . 
     The sleeve  752  fits over the circuit board  738  and extends from connector  724  to the adapter  716  as shown in  FIG. 46B . In this example, the sleeve  752  may be coupled to the adapter  716  via a threaded connection via the threaded protruding portion of the adapter  716  and a threaded interior portion of the sleeve  752 . But this threading arrangement may be reversed and/or replaced by other means (e.g., friction fit, etc.) 
     In this exemplary embodiment, the use of the adapter  716  and sleeve  752  helps to reduce the impact to the circuit board  738  when the antenna assembly  700  is dropped, as the adapter  716  helps loads/force to the sleeve  752 . In this exemplary way, the circuit board  738  can be protected from damage that might otherwise occur when the antenna assembly  700  is dropped. 
     In alternative embodiments, an antenna assembly may include a sheath  740 , antenna coil form  744 , and sleeve  752  made from a wide range of insulators/plastic materials for supporting the whole antenna structure. For example, an antenna assembly may be configured so as to be within a sheath where the interior of the antenna assembly is filled with air. In such example embodiment, the antenna&#39;s helical and linear radiators may be separated by a dielectric tubular member (e.g., straw, etc.) to prevent or at least inhibit direct electrical or galvanic contact between the helical and linear radiators. In such example, the antenna assembly may include at least one linear radiator aligned with or disposed at least partially along a longitudinal axis of at least one helical radiator. A dielectric tubular member may be disposed over the at least linear radiator. The at least one helical radiator may be external to the dielectric tubular member such that the dielectric tubular member prevents or at least inhibits direct electrical contact between the helical and linear radiators. A sheath may be disposed of the helical and linear radiators and dielectric tubular member. An interior of the sheath may be filled with air or other dielectric material. In alternative embodiments, an antenna assembly may not include any sheath. 
       FIGS. 52 through 62  provide analysis results measured for a prototype of the antenna assembly  700  shown in  FIG. 44 . These analysis results shown in  FIGS. 52 through 62  are provided only for purposes of illustration and not for purposes of limitation. 
     More specifically,  FIG. 52  is an exemplary line graph illustrating return loss in decibels (dB) versus frequency in megahertz (MHz) measured for the antenna assembly  700  in a hand held position. Generally,  FIG. 52  shows that the antenna assembly  700  is operable with relatively good/acceptable return loss and bandwidths for the VHF, UHF, 7-800, and GPS bands. 
       FIG. 53  includes tables with measured efficiency and gain in decibels (dB) for the antenna assembly  700  for the VHF band (azimuth plane—hand held position) and for the UHF, 7-800, and GPS bands (in free space). Generally, this performance summary data shows that the antenna assembly  700  has relatively good gain/efficiency for the VHF, UHF, 7-800, and GPS bands, including good open sky efficiency of 37% for the GPS band, average total efficiency of more than 50% and near horizontal efficiency of 35% and higher. 
       FIGS. 54 through 62  illustrate radiation patterns measured for the antenna assembly  700 . The image at the center of each graph represents a device (e.g., two way radio, etc.) having the antenna assembly  700  mounted on top thereof. More specifically,  FIG. 54  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  700  in a hand held position at a VHF frequency of 155 MHz.  FIGS. 55 through 57  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  700  in free space at UHF frequencies of 400 MHz, 470 MHz, and 520 MHz.  FIGS. 58 through 60  illustrate radiation patterns (azimuth plane) measured for the antenna assembly  700  in free space at frequencies of 764 MHz, 830 MHz, and 870 MHz, respectively, which are within the 7-800 MHz frequency band.  FIGS. 61 and 62  illustrate radiation patterns (phi zero degree plane and phi ninety degree plane, respectively) measured for the antenna assembly  700  in free space at the GPS frequency of 1575 MHz. Generally,  FIGS. 54 through 62  show the radiation patterns for the antenna assembly  700  at these various frequencies within the VHF, UHF, 7-800, and GPS bands and the good efficiency of the antenna assembly  700 . Accordingly, the antenna assembly  700  has relatively broad bandwidths for the VHF, UHF, 7-800, and GPS bands and allows multiple operating bands for wireless communications devices. 
     In this exemplary embodiment, the antenna assembly  700  may thus be configured to achieve multiband operation for frequencies associated with or falling within the VHF band from 136 MHz to 174 MHz, the entire UHF band from 380 MHz to 527 MHz, 7-800 MHz frequency band from 764 MHz to 870 MHz), and a GPS frequency of 1575 MHz. The antenna assembly  700  may be configured to achieve this multiband operation with a voltage standing wave ratio (VSWR) less than three, relatively good gain and efficiency for wireless applications. 
     The various antenna assemblies (e.g.,  100 ,  500 ,  600 ,  700 , etc.) disclosed herein may be used with various wireless devices within the scope of the present disclosure. By way of example, the antenna assemblies disclosed herein may be mounted externally to the housing of a two way radio by means of the threaded portions as shown in the figures. The antenna assembly may be mounted in its own sheath or housing and have a connector (e.g., 50 ohm connector, etc.) for connecting to a connector within the housing of the two way radio, so as to depend to the device ground plane to excite. While described in connection with a two way radio, embodiments of the antenna assemblies disclosed herein should not be limited to use with only two way radios and/or to externally mounting via threaded connections as antenna assemblies disclosed herein may be used in conjunction with various electronic devices. 
     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. In addition, advantages, and improvements that may be achieved with one or more exemplary embodiments of the present disclosure are provided for purpose of illustration only and do not limit the scope of the present disclosure, as exemplary embodiments disclosed herein may provide all or none of the above mentioned advantages and improvements and still fall within the scope of the present disclosure. 
     Specific dimensions, specific materials, and/or specific shapes disclosed herein are example in nature and do not limit the scope of the present disclosure. The disclosure herein of particular values and particular ranges of values (e.g., frequency ranges, etc.) for given parameters are not exclusive of other values and ranges of values that may be useful in one or more of the examples disclosed herein. Moreover, it is envisioned that any two particular values for a specific parameter stated herein may define the endpoints of a range of values that may be suitable for the given parameter (i.e., the disclosure of a first value and a second value for a given parameter can be interpreted as disclosing that any value between the first and second values could also be employed for the given parameter). 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 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. 
     Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.