Patent Publication Number: US-2015070239-A1

Title: Antenna

Description:
This application claims the benefit of U.S. provisional application Ser. No. 61/875,800, filed Sep. 10, 2013, the subject matter of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an antenna for a wireless device, and more particularly, to an antenna feeding a ground component by noncontact electrical coupling of a feed strip, wherein the ground component includes a portion of a metal part along surface(s) of the wireless device. 
     BACKGROUND OF THE INVENTION 
     Wireless electronic device, such as cellular phone and smart phone for wireless mobile telecommunication, as well as tablet computer, portable computer, handheld computer, digital camera, digital camcorder, media player, radio, television, networking apparatus (e.g., wireless network hub), sensor, surveillance apparatus and wearable gadgets (e.g., glasses or watch) capable of wireless interconnection, along with navigator and positioning apparatus (e.g., apparatus for satellite positioning), etc., has become popular, prevailing and essential in contemporary daily life. 
     For better user experience, mechanical robustness and/or functionality requirement, housing of modern wireless device has at least a portion made of metal. For example, housing of a wireless device may have a metal back cover, and/or a metal ring surrounding a rim of the wireless device. Display module (e.g., liquid crystal display module, LCM) exposed on an opening of wireless device may also be regarded as a metal portion of housing, because display module is packaged in a metal casing to be installed in wireless device. 
     Wireless device includes antenna for transmitting a feed signal as an outgoing wireless signal and/or receiving an incoming wireless signal as a feed signal. However, performance of antenna could be greatly degraded by metal portion of device housing. An antenna which can properly functions against metal portion is therefore demanded. 
     In a prior art, a gapped metal ring enclosing a rim of housing is grounded (tied to a ground voltage) to be utilized as an arm of an inverted F antenna, and is fed (i.e., connected to feed signal of an interior circuit board) via a conductive feed wire physically attached to the gapped metal ring by a conductive spring. However, such electrically conductive contact between feed and the grounded arm is mechanically vulnerable and unreliable, since it is in direct contact with the metal ring which bears mechanical impact, stress, pressure and deformation. When the conductive contact is loose, the antenna malfunctions. 
     SUMMARY OF THE INVENTION 
     To address issues of prior arts, the present invention provides an antenna exploiting conductive interior structures and housing to form a ground component, and feeding the ground component by noncontact electrical coupling, so as to avoid disadvantages of feeding the grounded arm by physical contact. 
     An objective of the invention is providing an antenna for a device (e.g., wireless device); the antenna may include a conductive feed strip and a conductive ground component. The ground component is for connecting a ground voltage, and, a first portion (e.g., an outer portion) of the ground component may include a portion of a metal part along surface(s) (e.g., side surface(s), front surface and/or back surface) of the device. For example, the first portion may include a segment of a metal ring, which surrounds a rim (or partial rim) of the device. The feed strip may have a feed port for relaying (receiving and/or transmitting) a feed signal, and may not physically contact the ground component; e.g., current (flow of electrical charges) on the feed strip can not flow to the ground component, and current on the ground component can not flow to the feed strip. 
     In an embodiment, besides the first portion, the ground component may further include an inner portion extending to a contact of the metal part of the device, while the metal part is gapped by a gap. The first portion may include a segment of the metal part, and may extend from the contact and end at the gap of the metal part. 
     In an embodiment, the gap may be adjacent to an opening of the device; for example, the gap and the opening may be at a same side of the metal part. A part of the inner portion may be formed by a ground plane of a circuit board of the device, and another part of the inner portion may be formed by a conductive interior structure of the device, wherein the conductive interior structure may be connected between the ground plane and the contact of the metal part; for example, the conductive interior structure may be a conductive casing (frame) of an LCM of the device. Accordingly, the inner portion can extend to conductively connect the first portion. In an embodiment, the feed strip may be formed by a conductive layer of the circuit board, and the conductive layer may be insulated from the ground plane. 
     In an embodiment, the gap may be at a first surface of the device, and the inner portion may be formed by the ground plane and a conductive wall extending from the ground plane to an opening of the device, wherein the opening may be at a second surface of the device. For example, the first surface and the second surface may be perpendicular or nonparallel. 
     In an embodiment, the ground component may further include a tuning strip extending from an end of the first portion toward interior of the device. 
     In an embodiment, the feed strip may include a trunk, a first branch and a second branch. The trunk may extend from the feed port to a trunk end along a first direction, the first branch may extend from the trunk end along a second direction, and the second branch may extend from the trunk end along a third direction. The first direction and the second direction may be nonparallel or parallel; e.g., the first direction may be perpendicular to the second direction. The first direction and the third direction may be nonparallel or parallel; e.g., the first direction may be perpendicular to the third direction. The second direction and the third direction may be parallel or not. 
     In an embodiment, the antenna may further include a quantity (one or more) of conductive auxiliary strips. Each auxiliary strip may have an auxiliary ground terminal for connecting the ground voltage (e.g., the ground plane), may have no physical contact with the feed strip, and may extend without intersecting the ground component. For example, each auxiliary strip may extend along an offset contour of the feed strip. 
     The quantity of auxiliary strips may include a first quantity (zero or more) of first auxiliary strips and a second quantity (zero or more) of second auxiliary strips. Each first auxiliary strip may have an auxiliary ground terminal for connecting the ground voltage, may have no physical contact with the feed strip, and may include a division extending along an offset contour of the trunk and the first branch. Each second auxiliary strip may have an first auxiliary ground terminal for connecting the ground voltage, may have no physical contact with the feed strip, and may include a division extending along an offset contour of the trunk and the second branch. 
     In an embodiment, the antenna may further include a first switch and an additional strip. The first switch may be connected to a first node of the ground component. The additional strip may be conductive, and may be connected between the first switch and a second node of the ground component. The first switch is capable of selectively conducting between the additional strip and the first node. 
     In an embodiment, the antenna may further include a second switch connected to the ground component and separating the ground component into a tail section and a head section, and capable of selectively conducting between the tail section and the head section. For example, the head section may include the inner portion and the first portion of the ground component, and the tail section may include the tuning strip extending from the switch toward interior of the device; e.g., the second switch may be connected between the first portion and the tuning strip, and the first node and the second node may both be at the head section. 
     Numerous objects, features and advantages of the present invention will be readily apparent upon a reading of the following detailed description of embodiments of the present invention when taken in conjunction with the accompanying drawings. However, the drawings employed herein are for the purpose of descriptions and should not be regarded as limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
         FIG. 1  illustrates an antenna according to an embodiment of the invention 
         FIG. 2  illustrates portions of the antenna shown in  FIG. 1 ; 
         FIG. 3  illustrates operation of the antenna shown in  FIG. 1 ; 
         FIG. 4  illustrates a conventional antenna; 
         FIG. 5  illustrates an antenna according to an embodiment of the invention; 
         FIG. 6  illustrates an antenna according to an embodiment of the invention; 
         FIG. 7  illustrates an antenna according to an embodiment of the invention; 
         FIG. 8  illustrates operation of the antenna shown in  FIG. 7 ; 
         FIG. 9  illustrates an antenna according to an embodiment of the invention; 
         FIG. 10  illustrates an antenna according to an embodiment of the invention; 
         FIG. 11  to  FIG. 14  illustrate operations of the antenna shown in  FIG. 10 ; 
         FIG. 15  illustrates an antenna according to an embodiment of the invention; 
         FIG. 16  to  FIG. 19  illustrate operations of the antenna shown in  FIG. 15 ; and 
         FIG. 20  illustrates an impalement of the antenna shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     According to an embodiment of the invention, please refer to  FIG. 1  illustrating an antenna  20   a  for a wireless device  10   a.  In addition to the antenna  20   a  embedded inside the device  10   a,  the device  10   a  may also include a circuit board  12   a,  a metal part  14   a,  and elements  11   a,    13   a  and  17   a.  The metal part  14   a  may extend along surface(s) of the device  10 ; for example, the metal part  14   a  may include a portion extending along side surface(s) of the device  10   a,  such as a portion of a metal ring surrounding rim of the device  10   a;  and/or, the metal part  14  may include a portion extending along (flat or curved) front and/or back surface(s) of the device  10   a,  e.g., a portion of a back plate of the device  10   a,  and/or a decorative belt of a front plate of the device  10   a.  The metal part  14   a  may be gapped by a gap  51   a,  and may include an opening  52   a  between two segments  53   a  and  54   a  of the metal part  14   a.  In the embodiment of  FIG. 1 , the gap  51   a  and the opening  52   a  can be at different side surfaces of the device  10   a,  e.g., the gap  51   a  is at the right side surface and the opening  52   a  is at the bottom side surface of the device  10   a.    
     The circuit board  12   a,  e.g., printed circuit board, may include a ground plane  16   a  connecting a ground voltage (not shown). Each of the elements  11   a,    13   a  and  17   a  may be mounted on the circuit board  12   a  and packaged by conductive casing (e.g., conductive side walls) which may be kept at the ground voltage (e.g., by being connected to the ground plane  16   a ), hence the conductive casing can be regarded as a grounded conductive interior structure of the device  10   a.  For example, the element  11   a  may be an LCM exposed to a front surface of the device  10   a,  or a grounded metal back cover (back plate, back surface) of the device  10   a;  the element  13   a  may be a microphone module, a speaker module, a camera module, a flash-light module and/or a sensor module; and the element  17   a  may be an mechanical connection interface extruding to the opening  52   a  from the ground plane  16   a,  e.g., a USB (universal serial bus) connector or an audio jack; the element  17   a  may also be a button (e.g., power switch) for manual control, a sensor module, a stylus pen container and/or a slot for memory card or SIM (subscriber identity module) card. 
     The antenna  20   a  may include a strip (feed strip)  30   a  and a component (ground component)  40   a.  The strip  30   a  may have a feed port  31   a  for relaying a feed signal (not shown). From a position  41   a  in vicinity of the feed port  31   a,  the component  40   a  may extend to positions  42   a,    43   a,    44   a,  and ends at a position  45   a,  and may include three serially connected conductive portions  401   a,    402   a  and  403   a.    
     In the component  40   a,  the portion  401   a  may extend from the position  41   a  to the positions  42   a  and  43   a,  and may be regarded as an inner portion of the component  40   a.  The portion  402   a  may extend from the position  43   a  to the position  44   a,  and may be regarded as a first portion. The portion  403   a  may extend from the position  44   a  (the end of the portion  402   a ) to the position  45   a,  and may function as a tuning strip. 
     As shown in  FIG. 1 , the portion  401   a  may include two serially connected conductive parts  4011   a  and  4012   a.  The part  4011   a  may extend from the position  41   a  to the position  42   a,  and may be formed by the ground plane  16   a;  the part  4012   a  may extend from the position  42   a  to the position  43   a,  and may be formed by conductive interior structure of the element  17   a.  The conductive interior structure of the element  17   a  can be firmly engaged to the segment  53   a  at the position  43   a  to provide a mechanically reliable, durable and robust conductive contact between the portions  401   a  and  402   a.    
     As illustrated in  FIG. 1 , the portion  402   a  may extend along surface(s) of the device  10   a.  The portion  402   a  may include a portion formed by segment(s) of a metal ring which surrounds side surface(s) of the device  10   a,  and/or may include a portion formed by a conductive portion of a back surface of the device  10   a,  and/or formed by a conductive portion of a decorative belt cross a front surface of the device  10   a.  For example, the portion  402   a  may include a segment of the metal part  14   a,  e.g., the segment  53   a  extending from position  43   a,  along two side surfaces (and a rounded corner in-between) of the device  10   a,  and ending at the gap  51   a.  By combining the portions  401   a,    402   a  and  403   a,  the component  40   a  may form a grounded conductive G-shaped path which extends from the positions  41   a,    42   a,    43   a,    44   a  to  45   a,  and surrounds the feed strip  30   a  without physically conductive contact or intersection. 
     There may not be physical contact between the strip  30   a  and the component  40   a,  e.g. current on the strip  30   a  does not flow to the component  40   a,  and current on the ground component  40   a  does not flow to the strip  30   a.  Continuing the embodiment of  FIG. 1 , please refer to  FIG. 2  illustrating an arrangement example of the strip  30   a  and the ground plane  16   a  according to an embodiment of the invention. The strip  30   a  may be formed by a conductive (e.g., metal) layer  130   a  of the circuit board  12   a;  the layer  130   a  and the ground plane  16   a  may be respectively attached to opposite surfaces of an intermediate structure  120   a  which interfaces the layer  130   a  and the ground plane  16   a  by dielectric material. Accordingly, though x-y plane projection of the strip  30   a  and the ground plane  16   a  may look close or even overlapping (e.g., at the feed port  31   a  and the nearby position  41   a,    FIG. 1 ), the strip  30   a  actually does not physically contact the ground plane  16   a  along z-axis, without any physical current conduction path between them. 
     Besides the strip  30   a,  the layer  130   a  may include other conductive routing, such as wires  121   a  and  122   a.  The intermediate structure  120   a  may be a dielectric layer; alternatively, the intermediate structure  120   a  may include other conductive layer(s) (not shown) and dielectric layers (not shown), wherein each conductive layer can be sandwiched between two adjacent dielectric layers. 
     As shown in  FIG. 2 , the strip  30   a  may include a trunk  301   a  and two branches  302   a  and  303   a.  The trunk  301  a may extend from the feed port  31   a  to an end  300   a  (trunk end) along a direction  311   a,  the branch  302   a  may extend from the end  300   a  to another end  322   a  along a direction  312   a,  and the branch  303   a  may extend from the end  300   a  to another end  323   a  along a direction  313   a.  The directions  311   a  and  312   a  may be parallel or nonparallel; e.g., the directions  311   a  and  312   a  may be perpendicular. The directions  311   a  and  313   a  may be parallel or nonparallel; e.g., the directions  311   a  and  313   a  may be perpendicular. The directions  312   a  and  313   a  may be parallel. In an embodiment, the strip  30   a  may include only one of the two branches  302   a  and  303   a.  In an embodiment, each of the branches  302   a  and  303   a  may include other branch (or branches) (not shown); for example, the branch  302   a  may include another branch (not shown) extending from the end  322   a,  or any position between the ends  300   a  and  322   a.  Though the trunk  301   a  may connect to the branch  302   a  by a sharp turn as shown in  FIG. 2 , the trunk  301   a  may connect to the branch  302   a  by a chamfer or a fillet, e.g., the trunk  301   a  may transit to the branch  302   a  by a J-shaped connection. 
     Continuing the embodiment of  FIG. 1  and  FIG. 2 , please refer to  FIG. 3  illustrating operation of the antenna  20   a.  The feed strip  30   a  is capable of providing a current distribution path  201   a  which extends from the feed port  31   a  to the ends  300   a,    322   a  and  323   a,  and therefore providing a high-band (high-frequency band) path for wireless transmission and/or receiving at high-band. The feed strip  30   a  may also work to feed the component  40   a  by noncontact electrical coupling, and the component  40   a  is capable of providing another current distribution path  202   a  extending from the position  41   a  to the positions  42   a,    43   a,    44   a  and  45   a,  so as to provide a low-band (low-frequency band) path for wireless transmission and/or receiving at low-band. For antenna design flexibility, dimensions of the strip  30   a  (e.g., length between the feed port  31   a  to the end  300   a,  length between the ends  300   a  and  322   a,  and/or length between the ends  300   a  and  323   a ) may be adjusted to tune performance and characteristics (e.g., upper/lower frequency bounds, bandwidth and/or central resonance frequency) of the high-band; likewise, dimensions of the component  40   a  (e.g., length of the tuning strip portion  403   a  between the positions  44   a  and  45   a ) may be adjusted to tune performance and/or characteristics of the low-band. In addition, distances between the strip  30   a  and the component  40   a  may also be adjusted to tune performance and/or characteristics of the antenna. 
     Please refer to  FIG. 4  and  FIG. 5 ; schematically,  FIG. 4  illustrates a prior antenna ant 0  and  FIG. 5  illustrates an antenna ant 1  according to an embodiment of the invention. As shown in  FIG. 4 , the antenna ant 0  includes a conductive L-shaped arm m 1  having an end connected to a ground plane, along with a conductive strip m 2  which is fed at a port p 1  against the ground plane, and is connected to the arm m 1  by physical conductive contact, hence the arm m 1  and the strip m 2  combines to form an inverted F antenna. However, while the arm m 1  is formed by metal ring of device, the conductive contact connecting the arm m 1  and the strip m 2  is mechanically weak and unreliable. On the contrary, as shown in  FIG. 5 , the antenna ant 1  may include a conductive component M 1  and a conductive strip M 2  which does not physically contact the component M 1 ; i.e., there is no electrically conductive contact (conductor connection) between the component M 1  and the strip M 2 . Feed signal at the feed port P 1  can be fed to the component M 1  via electrically noncontact feed coupling. Therefore, mechanical unreliable connection between the grounded component and the feed port is avoided. Note that the component M 1  and the strip M 2  of the antenna ant 1  can respectively be implemented by the component  40   a  and the strip  30   a  of the antenna  20   a  (shown in  FIG. 1 ), so the antenna  20   a  can operate by leveraging feed coupling. 
     Please refer to  FIG. 6  illustrating an antenna  20   b  according to an embodiment of the invention. Similar to the antenna  20   a  shown in  FIG. 1 , the antenna  20   b  shown in  FIG. 6  may include a strip  30   b  and a component  40   b  which does not physically contact the strip  30   b.  The strip  30   b  can be made of conductive material, may have a feed port  31   b,  and may include a trunk  301   b  and two branches  302   b  and  303   b.  The trunk  301   b  may extend from the feed port  31  b to an end  300   b,  and the branches  302   b  and  303   b  may respectively branch to two ends  322   b  and  323   b  from the end  300   b.    
     The component  40   b  may be connected to a ground voltage (not shown); from a position  41   b  near the feed port  31   b,  the component  40   b  may extend to positions  42   b,    43   b,    44   b  and  45   b,  and may be formed by conductive portions which are serially connected by electrically conductive contacts, e.g., an inner portion extending from the position  41   b  to the positions  42   b  and  43   b,  a first portion between the positions  43   b  and  44   b,  and a tuning strip portion between the positions  44   b  and  45   b.  The inner portion may be provided by a ground plane  16   b  of a circuit board  12   b,  along with an interior conductive structure of an element  17   b.  The first portion may be a segment of a metal part (e.g., a metal ring)  14   b,  which can be gapped by a gap  51   b.    
     Besides the strip  30   b  and the component  40   b,  the antenna  20   b  may further include one or more auxiliary strips as parasitic strips, such as strips Pa[ 1 ], Pa[ 2 ], P[a 3 ] and Pa[ 4 ]. The strips Pa[ 1 ] to Pa[ 4 ] may respectively have terminals g[ 1 ], g[ 2 ], g[ 3 ] and g[ 4 ] for connecting the ground voltage, may not physically contact the strip  30   b,  and may extend without intersecting the component  40   b;  e.g., each strip Pa[n] of the strips Pa[ 1 ] to Pa[ 4 ] may not have to electrically contact the component  40   b  except at the terminal g[n]. For example, one, some or all of the auxiliary strips Pa[ 1 ] to Pa[ 4 ] may be formed by a first conductive layer where the ground plane  16   b  resides. And/or, while the strip  30   b  may be formed by another second conductive layer (not shown) of the circuit board  12   b  with the second conductive layer insulated from the first conductive layer of the ground plane  16   b,  one, some or all of the auxiliary strips Pa[ 1 ] to Pa[ 4 ] may be formed by the second conductive layer; the strip Pa[n] formed by the second conductive layer may be connected to the ground plane  16   b  by conductive via(s) at the terminal g[n], and there can be no physical contact between the strip  30   b  and each strip Pa[n]. 
     In an embodiment, a strip Pa[n] may extend along an offset contour of the strip  30   b;  alternatively, a strip Pa[n] may at least have a division extending along an offset contour of the strip  30   b.  For example, the strip Pa[ 2 ] may extend from the terminal g[ 2 ] to a position  603  along an offset contour oc[ 2 ] of the trunk  301   b  and the branch  302   b.  Similarly, the strips Pa[ 3 ] and Pa[ 4 ] may respectively extend along offset contours oc[ 3 ] and oc[ 4 ] of the trunk  301   b  and the branch  303   b.  On the other hand, the strip Pa[ 1 ] may include a first division extending from the terminal g[ 1 ] to an intermediate position  601  along an offset contour oc[ 1 ] of the trunk  301   b  and the branch  302   b,  and a second division extending from the position  601  to a position  602  of the strip Pa[ 1 ], wherein the second division does not have to track offset contour of the strip  30   b.  The antenna of the invention may have more or fewer auxiliary strips than the strips Pa[ 1 ] to Pa[ 4 ]; the auxiliary strip(s) can be utilized to tune characteristics and/or performance of the antenna  20   b.    
     Please refer to  FIG. 7  illustrating an antenna  20   c  of a wireless device  10   c,  according to an embodiment of the invention. The device  10   c  may include a circuit board  12   c,  interior elements  11   c,    13   c  and  17   c  mounted on the circuit board  12   c,  a metal part  14   c  along surface(s) of the device  10   c,  with the antenna  20   c  embedded in the device  10   c.  Similar to the metal part  14   a  shown in  FIG. 1 , the metal part  14   c  in  FIG. 7  may include a portion formed by segment(s) of a metal ring which surrounds side surface(s) of the device  10   c,  and/or may include a portion formed by a conductive portion of a back surface of the device  10   c,  and/or formed by a conductive portion of a decorative belt cross a front surface of the device  10   c.  The metal part  14   a  may include two segments  53   c  and  54   c  with an opening  52   c  in-between, and may be gapped by a gap  51   c  adjacent to the opening  52   c;  e.g., the gap  51   c  and the opening  52   c  are at a same side (e.g., bottom or top side) of the device  10   c.    
     The circuit board  12   c,  e.g., printed circuit board, may include a ground plane  16   c  connecting a ground voltage (not shown). Each of the elements  11   c,    13   c  and  17   c  may be packaged by conductive casing (e.g., conductive side walls) which is kept at the ground voltage, e.g., electrically connects the ground plane  16   c  by conductive contact, hence the conductive casing can be regarded as a grounded conductive interior structure. For example, the element  11   c  may be an LCM; the element  13   c  may be a microphone module, a speaker module, a camera module, a flash-light module and/or a sensor module; and the element  17   c  extruding to the opening  52   c  from the ground plane  16   c  may be a USB connector, an audio jack, a button (e.g., power switch) for manual control, an externally exposed sensor module, a stylus pen container and/or a containing slot for memory card or SIM card. 
     The antenna  20   c  may include a strip  30   c  as a feed strip and a component  40   c  as a ground component. The strip  30   c  may have a feed port  31   c  for relaying a feed signal (not shown). The component  40   c  may extend from a position  41   c  to positions  42   c,    43   c,    44   c,  and ends at a position  45   c,  and may include three serially connected conductive portions  401   c,    402   c  and  403   c.  The portion  402   c  may include a portion formed by segment(s) of a metal ring which surrounds side surface(s) of the device  10   c,  and/or may include a portion formed by a conductive portion of a back surface of the device  10   c,  and/or formed by a conductive portion of a decorative belt cross a front surface of the device  10   c.    
     From the position  41   c  in vicinity of feed port  31   c,  the portion  401   c  of the component  40   c  may extend to the positions  42   c  and  43   c,  and may be regarded as an inner portion of the component  40   c.  The portion  402   c  may extend from the position  43   c  to the position  44   c,  and may be regarded as a first portion. The portion  403   c,  may extend from the position  44   c  (the end of the portion  402   c ) to the position  45   c,  and may function as a tuning strip. 
     As shown in  FIG. 7 , the portion  401   c  may include two serially connected parts  4011   c  and  4012   c.  The part  4011   c  may extend from the position  41   c  to the position  42   c,  and may be formed by the ground plane  16   c  along with the conductive interior structure of the element  11   c;  the part  4012   c  may extend from the position  42   c  to the position  43   c  and may be formed by conductive interior structure of the element  11   c.  At the position  43   c,  the conductive interior structure of the element  11   c  may be firmly engaged to the segment  53   c  of the metal part  14   c  to provide a mechanically reliable, durable and robust conductive contact between the portions  401   c  and  402   c.    
     The portion  402   c  may extend along surface(s) (e.g., two side surfaces and a rounded corned in-between) of the device  10   c.  For example, the portion  402   c  may include a segment of the metal part  14   c,  e.g., the segment  53   c  extending from position  43   c  and ending at the gap  51   c.  By combining the portions  401   c,    402   c  and  403   c,  the component  40   c  may form a grounded conductive path which extends from the positions  41   c,    42   c,    43   c,    44   c  to  45   c,  and may surround the feed strip  30   c  without physically conductive contact or intersection. 
     There may be no physical contact between the strip  30   c  and the component  40   c,  e.g. current on the strip  30   c  does not flow to the component  40   c,  and current on the ground component  40   c  does not flow to the strip  30   c.  The strip  30   c  may include a trunk  301   c  and two branches  302   c  and  303   c.  The trunk  301   c  may extend from the feed port  31   c  to an end  300   c  along a direction  311   c,  the branch  302   c  may extend from the end  300   c  to another end  322   c  along a direction  312   c,  and the branch  303   c  may extend from the end  300   c  to another end  323   c  along a direction  313   c.  The directions  311   c  and  312   c  may be perpendicular or not. The directions  311   c  and  313   c  may be perpendicular or not. 
     Continuing the embodiment of  FIG. 7 , please refer to  FIG. 8  illustrating operation of the antenna  20   c.  The feed strip  30   c  is capable of providing a current distribution path  201   c  which extends from the feed port  31   c  to the ends  300   c,    322   c  and  323   c,  and therefore providing a high-band path for wireless transmission and/or receiving at high-band. The feed strip  30   c  may also work to feed the component  40   c  by distant electrical coupling, and the component  40   c  is capable of providing another current distribution path  202   c  extending from the position  41   c  to the positions  42   c,    43   c,    44   c  and  45   c,  so as to provide a low-band path for wireless transmission and/or receiving at low-band. For antenna design flexibility, dimensions of the strip  30   c  (e.g., length between the feed port  31   c  to the end  300   c,  length between the ends  300   c  and  322   c,  and/or length between the ends  300   c  and  323   c ) may be adjusted to tune performance and characteristics of the high-band; likewise, dimensions of the component  40   c  (e.g., length of the tuning strip portion  403   c  between the positions  44   c  and  45   c ) may be adjusted to tune performance and/or characteristics of the low-band. Furthermore, distances between the strip  30   c  and the component  40   c  may also be adjusted to tune performance and/or characteristics of antenna. 
     Please refer to  FIG. 9  illustrating an antenna  20   d  according to an embodiment of the invention. Similar to the antenna  20   c  shown in  FIG. 7 , the antenna  20   d  shown in  FIG. 9  may include a conductive strip  30   d  and a conductive component  40   d  which does not physically contact the strip  30   d.  The strip  30   d  may have a feed port  31   d,  and may include a trunk  301   d  and two branches  302   d  and  303   d.  The trunk  301   d  may extend from the feed port  31   d  to an end  300   d,  and the branches  302   d  and  303   d  may respectively branch to two ends  322   d  and  323   d  from the end  300   d.    
     The component  40   d  may be connected to a ground voltage (not shown); from a position  41   d  near the feed port  31   d,  the component  40   d  may extend to positions  42   d,    43   d,    44   d  and  45   d,  and may be formed by portions which are serially connected by electrically conductive contacts, e.g., an inner portion extending from the position  41   d  to the positions  42   d  and  43   d,  a first portion between the positions  43   d  and  44   d,  and a tuning strip portion between the positions  44   d  and  45   d.  The inner portion may be provided by a ground plane  16   d  of a circuit board  12   d,  along with an interior conductive structure of an element  11   d.  The first portion may be a segment of a metal part  14   d,  which may be gapped by a gap  51   d  adjacent to an element  17   d.    
     Besides the strip  30   d  and the component  40   d,  the antenna  40   d  may further include one or more auxiliary strips as parasitic strips, such as strips Pa[i] and Pa[j]. The strips Pa[i] and Pa[j] may respectively have terminals g[i] and g[j] for connecting the ground voltage, may not physically contact the strip  30   d,  and may extend without intersecting the component  40   d;  e.g., the strips Pa[i] and Pa[j] do not have to conductively contact the component  40   d  except at the terminal g[i] and g[j]. For example, one or both of the auxiliary strips Pa[i] and Pa[j] may be formed by a first conductive layer which also forms the ground plane  16   d.  And/or, while the strip  30   d  may be formed by a second conductive layer (not shown) of the circuit board  12   d  with the second conductive layer insulated from the first conductive layer of the ground plane  16   d,  one or both of the auxiliary strips Pa[i] and Pa[j] may also be formed by the second conductive layer; the strip(s) Pa[i] and/or Pa[j] formed by the second conductive layer may be connected to the ground plane  16   d  by conductive via(s) at the terminal g[i] and/or g[j], and there may be no physical contact between the strip  30   d  and each of the strip Pa[i] and Pa[j]. 
     In an embodiment, each of the strips Pa[i] and Pa[j] may have at least a division extending along an offset contour of the strip  30   d.  For example, the strip Pa[j] may extend from the terminal g[j] to a position  903  along an offset contour oc[i] of the trunk  301   d  and the branch  302   d.  The strip Pa[i] may include a first division and a second division; the first division may extend from the terminal g[i] to an intermediate position  901  along an offset contour oc[i] of the trunk  301   d  and the branch  303   d,  and the second division may extend from the position  901  to a position  902  of the strip Pa[i], wherein the second division does not have to track offset contour of the strip  30   d.  The antenna of the invention may have more or fewer auxiliary strips than the strips Pa[i] and Pa[j]; the auxiliary strip(s) can be utilized to tune characteristics and/or performance of the antenna  20   d.    
     Please refer to  FIG. 10  illustrating an antenna  20   e  according to an embodiment of the invention. Similar to the antenna  20   a  shown in  FIG. 1 , the antenna  20   e  in  FIG. 9  may include a feed strip  30   e  and a ground component  40   e;  moreover, the antenna  20   e  may further include an additional strip  70   e  and two switches S 1  and S 2 . 
     The strip  30   e  may have a feed port  31   e,  and may include a conductive trunk  301   e  and two conductive branches  302   e  and  303   e  electrically connected to the trunk  301   e  by conductive contact. The trunk  301   e  may extend from the feed port  31   e  to an end  300   e,  where the two branches  302   e  and  303   e  may respectively branch to two ends  322   e  and  323   e.  The strip  30   e  may not physically contact the component  40   e,  the strip  70   e  and the switches S 1  and S 2 . 
     The component  40   e  may be connected to a ground voltage (not shown), and may be separated into two sections  90   e  and  92   e  (head and tail sections) by the switch S 2 . From a position  41   e  near the feed port  31   e,  the head section  90   e  may extend via positions  42   e,    43   e,    44   e  to a position  441   e  (a node), and may be formed by portions which are serially connected by conductive contacts; the portions may include an inner portion extending from the position  41   e  to the positions  42   e  and  43   e,  as well as a first portion extending from the positions  43   e  to the positions  44   e  and  441   e.  The inner portion may be provided by a ground plane  16   e  of a circuit board  12   e,  along with an interior conductive structure of an element  17   e.  The first portion may be provided by a segment of a metal part  14   e,  which may be gapped by a gap  51   e  near the positions  44   e  and  441   e.    
     On the other hand, the tail section  92   e  of the component  40   e  may be a tuning strip portion extending from a position  442   e  (a node) to a position  45   e,  i.e., extending from the switch S 2  toward interior of wireless device. The switch S 2  is capable of selectively conducting between the two positions  441   e  and  442   e,  i.e., capable of selectively conducting between the two sections  90   e  and  92   e.    
     The switch S 1  may be connected between a position  700   e  (first node) of the component  40   e  and a position  701   e  of the strip  70   e.  The additional strip  70   e  may extend from position  701  e to a position  702   e  (second node) of the component  40   e;  at the position  702   e,  the conductive strip  70   e  can be electrically connected to the component  40   e  by conductive contact. The switch S 1  is capable of selectively conducting between the strip  70   e  and the position  700   e  of the component  40   e.    
     Continuing the embodiment of  FIG. 10 , please refer to  FIG. 11  to  FIG. 14  illustrating operations of the antenna  20   e  shown in  FIG. 10 . As shown in  FIG. 11  to  FIG. 14 , the strip  30   e  is capable of providing a current distribution path  201   e  for resonation of a wireless high-band. Furthermore, according to whether the switches S 1  and S 2  are on (conducting) or off (not conducting), the antenna  20   e  is capable of providing different bands, e.g., different low-bands. 
     In  FIG. 11 , the switch S 1  is off (not conducting) and the switch S 2  is on (conducting), the strip  70   e  is therefore bypassed by the turned-off switch S 1 , but the position  441   e  can be conducted to the position  442   e  by the turned-on switch S 2 . Accordingly, from the position  41   e  near the feed port  31   e,  the antenna  20   e  can provide a current distribution path  202   e _ 1  extending via the positions  42   e,    43   e,    44   e,    441   e  and  442   e  to the position  45   e  for resonation of a first low-band. 
     In  FIG. 12 , the switch S 1  is off and the switch S 2  is also off, hence the strip  70   e  is bypassed, and the position  441   e  is not conducted to the position  442   e.  Accordingly, the antenna  20   e  can provide a current distribution path  202   e _ 2  extending from the position  41   e  to the positions  42   e,    43   e,    44   e  and  441   e  for resonation of a second low-band. Because the turned-off switch S 2  keeps the section  92   e  electrically disconnected from the position  441   e,  the path  202   e _ 2  is shorter than the path  202   e _ 1  in  FIG. 11 , and frequency of the second low-band can be higher than that of the first low-band. 
     In  FIG. 13 , the switch S 1  is on and the switch S 2  is also on, hence the strip  70   e  is electrically connected to the position  701   e  to form a short cut from the position  700   e  of the ground plane  16   e  to the position  702   e  of the metal part  14   e.  Accordingly, the antenna  20   e  can provide a current distribution path  202   e _ 3  extending from the position  41   e  to the positions  700   e,    701   e,    702   e,    44   e,    441   e,    442   e  and  45   e  for resonation of a third low-band. Because of the short cut provided by the turned-on switch S 1  and the strip  70   e,  length of the path  202   e _ 3  is shorter than the path  202   e _ 1  in  FIG. 11 , and frequency of the third low-band can be higher than that of the first low-band. 
     In  FIG. 14 , the switch S 1  is on but the switch S 2  is off. Accordingly, the antenna  20   e  can provide a current distribution path  202   e _ 4  extending from the position  41   e  to the positions  700   e,    701   e,    702   e,    44   e  and  441   e  for providing a fourth low-band. Comparing to the paths  202   e _ 1  to  202   e _ 3  respectively shown in  FIG. 11  to  FIG. 13 , length of the path  202   e _ 4  is the shortest, so frequency of the fourth low-band can be higher than frequencies of the first to third low-bands. 
     Please refer to  FIG. 15  illustrating an antenna  20   f  according to an embodiment of the invention. Similar to the antenna  20   c  shown in  FIG. 7 , the antenna  20   f  in  FIG. 15  may include a conductive feed strip  30   f  and a conductive ground component  40   f;  in addition, the antenna  20   f  may further include an additional strip  70   f  and two switches S 1  and S 2 . 
     The strip  30   f  may have a feed port  31   f,  and may include a conductive trunk  301   f  and two conductive branches  302   f  and  303   f.  The trunk  301   f  may extend from the feed port  31   f  to an end  300   f,  where the two branches  302   f  and  303   f  may respectively branch to two ends  322   f  and  323   f.  The strip  30   f  may not physically contact the component  40   f,  the strip  70   f  and the switches S 1  and S 2 . 
     The component  40   f  may be connected to a ground voltage (not shown), and may be separated into two sections  90   f  and  92   f  (head and tail sections) by the switch S 2 . From a position  41   f  near the feed port  31   f,  the head section  90   f  may extend via positions  42   f,    43   f,    44   f  to a position  441   f  (a node), and may be formed by portions which are serially connected by conductive contacts; the portions may include an inner portion extending from the position  41   f  to the positions  42   f  and  43   f,  as well as a first portion extending from the positions  43   f  to the positions  44   f  and  441   f.  The inner portion may include a part provided by a ground plane  16   f  of a circuit board  12   f,  along with another part provided by an interior conductive structure of an element  11   f.  The first portion may be provided by a segment of a metal part  14   f,  which may be gapped by a gap  51  f near the positions  44   f  and  441   f.    
     On the other hand, the tail section  92   f  of the component  40   f  may be a tuning strip extending from a position  442   f  (a node) to a position  45   f,  i.e., extending from the switch S 2  toward interior of wireless device. The switch S 2  is capable of selectively conducting between the two positions  441   f  and  442   f,  i.e., between the two sections  90   f  and  92   f.    
     The switch S 1  may be connected between a position  700   f  (first node) of the component  40   f  and a position  701   f  of the strip  70   f.  The additional strip  70   f  may extend from the position  701   f  to a position  702   f  (second node) of the component  40   f;  at the position  702   f,  the conductive strip  70   f  may be connected to the component  40   f  by conductive contact. The switch S 1  is capable of selectively conducting between the strip  70   f  and the position  700   f  of the component  40   f.    
     Continuing the embodiment of  FIG. 15 , please refer to  FIG. 16  to  FIG. 19  illustrating operations of the antenna  20   f  shown in  FIG. 15 . As shown in  FIG. 16  to  FIG. 19 , the strip  30   f  is capable of providing a current distribution path  201   f  for providing a wireless high-band. Furthermore, according to whether the switches S 1  and S 2  are on or off, the antenna  20   f  is capable of providing different bands, e.g., different low-bands. 
     In  FIG. 16 , the switch S 1  is off (not conducting) and the switch S 2  is on (conducting), the strip  70   f  may therefore be bypassed by the turned-off switch S 1 , but the position  441   f  can be conducted to the position  442   f  by the turned-on switch S 2 . Accordingly, from the position  41   f,  the antenna  20   f  can provide a current distribution path  202   f _ 1  extending via the positions  42   f,    43   f,    44   f,    441   f  and  442   f  to the position  45   f  for providing a first low-band. 
     In  FIG. 17 , the switches S 1  and S 2  are both off, so the strip  70   f  may be bypassed, and the position  441   f  is not conducted to the position  442   f.  Accordingly, the antenna  20   f  can provide a current distribution path  202   f _ 2  extending from the position  41   f  to the positions  42   f,    43   f,    44   f  and  441   f  for a second low-band. Because the turned-off switch S 2  may keep the section  92   f  electrically disconnected from the position  441   f,  the path  202   f _ 2  may be shorter than the path  202   f _ 1  in  FIG. 16 , and frequency of the second low-band can be higher than that of the first low-band. 
     In  FIG. 18 , both the switches S 1  and S 2  are turned on, hence the strip  70   f  may be electrically connected to the position  701   f  to form a detour from the position  700   f  to the position  702   f.  Accordingly, the antenna  20   f  can provide a current distribution path  202   f _ 3  extending from the position  41   f  to the positions  700   f,    701   f,    702   f,    44   f,    441   f,    442   f  and  45   f  for providing a third low-band. Because length of the path  202   f _ 3  is shorter than the path  202   f _ 1  in  FIG. 16 , frequency of the third low-band can be higher than that of the first low-band. 
     In  FIG. 19 , the switch S 1  is on but the switch S 2  is off. Accordingly, the antenna  20   f  can provide a current distribution path  202   f _ 4  extending from the position  41   f  to the positions  700   f,    701   f,    702   f,    44   f  and  441   f  for providing a fourth low-band. Comparing to the paths  202   f _ 1  to  202   f _ 3  respectively shown in  FIG. 16  to  FIG. 18 , length of the path  202   f _ 4  is the shortest, so frequency of the fourth low-band can be higher than frequencies of the first to third low-bands. 
     By controlling on and off of the switches S 1  and S 2 , the antenna  20   e  ( FIGS. 10) and 20   f  ( FIG. 15 ) are capable of providing a variety of low-bands, so as to adapt various band requirements. The switch S 1  in  FIG. 10  or  FIG. 15  may be implemented by the circuit board  12   e  ( FIG. 10 ) or  12   f  ( FIG. 15 ), so the switch S 1  can be electrically controlled. The switch S 2  in  FIG. 10  or  FIG. 15  may also be implemented by the circuit board  12   e  ( FIG. 10 ) or  12   f  ( FIG. 15 ). Alternatively, the switch S 2  may also be implemented by an additional flexible circuit board. For example, along with  FIG. 10 , please refer to  FIG. 20  illustrating an embodiment to implement the switch S 2  of the antenna  20   e  in  FIG. 10 . As shown in  FIG. 20 , the switch S 2  may be formed by a flexible circuit board  46 , which may also include a pad  481 , the conductive section  92   e  and a pad  482 . The pad  481  may be conductively attached to the metal part  14   e  at the position  44   e,  and may be connected to a first terminal of the switch S 2  at the position  441   e  of the flexible circuit board  46 . The section  92   e  may extend from a second terminal of the switch S 2  (at the position  442   e  of the flexible circuit board  46 ) to the position  45   e  of the flexible circuit board  46 . The pad  482  may be conductively attached to the circuit board  12   e  for receiving a control signal (not shown) issued from the circuit board  12   e;  according to the control signal, the switch S 2  can turn on and off to selectively conduct between its first and second terminals at positions  441   e  and  442   e.  The flexible circuit board  46  may be supported by a dielectric interior structure  141  which may isolate the flexible circuit board  46  from the metal part  14   e  except at the pad  481 . Likewise, the switch S 2  of the antenna  20   f  ( FIG. 15 ) may be arranged in a manner similar to  FIG. 20 . Any of he feed strips  30   a  to  30   f  respectively shown in  FIG. 1 ,  FIG. 6 ,  FIG. 7 ,  FIG. 9 ,  FIG. 10  and  FIG. 15  may also be formed by a flexible circuit board. 
     In the embodiment of  FIG. 10 , though the additional strip  70   e  linearly extends along y-direction, the strip  70   e  may also combine x-directional segment(s), y-directional segment(s), tilt segment(s) and/or curved segment(s) to extend from the position  701   e  to the position  702   e.  Similarly, the strip  70   f  in the embodiment of  FIG. 15  does not have to be shaped along a straight line from the position  701   f  to the position  702   f.    
     Similar to the embodiments shown in  FIG. 6  and  FIG. 9 , the antennas  20   e  and  20   f  in  FIGS. 10 and 15  may also include auxiliary strip(s) to tune antenna characteristics and performance. 
     To sum up, rather than feeding a grounded arm by physical contact, antenna according to the invention feeds the ground component by noncontact couple feed, so as to effectively avoid mechanical robustness issues of conductive contact, enhance reliability and durability, and maintain proper operation of antenna. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.