Abstract:
An antenna system comprises an antenna that integrates a separate fed through coaxial cable as part of its resonant structure. The fed through coaxial cable is used to feed a second antenna. This design allows for the antenna and the fed through cable to be accommodated in a very limited space at the edge of a handheld electronic device.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application is based in part on provisional patent application 61/542,371, filed Oct. 3, 2011, and entitled “Compact Multi-Band Antenna With Integrating Fed Through Co-Axial Cable”. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to antenna systems for handheld electronics. 
       BACKGROUND 
       [0003]    Modern handheld electronic devices such as smart phones and tablet computers are designed to contain electronics circuit boards and components at a very high density in a confined space. Furthermore in order to provide wireless connectivity through multiple standards such as cellular telephony standards and wireless Local Area Network (LAN) standards, or to support antenna diversity within a single standard, it is often desirable to accommodate multiple antennas in a single hand held electronic device. Space within the handheld device being very limited it is difficult to prevent one antenna or a feed conduit for an antenna which is capable of resonating radio waves from disrupting the operation of a second proximate antenna. Thus there is a need for antennas system that includes multiple antenna elements and can be accommodated within a limited space without causing mutual interference between the antennas and the feed systems for the antennas. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0004]    The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
           [0005]      FIG. 1  is a partial x-ray front view of a handheld electronic device according to an embodiment of the invention; 
           [0006]      FIG. 2  is a front view of an antenna used in the handheld electronic device shown in  FIG. 1  according to an embodiment of the invention; 
           [0007]      FIG. 3  is a back view of the antenna shown in  FIG. 2 ; 
           [0008]      FIG. 4  is a return loss plot for the antenna shown in  FIGS. 2-3 ; and 
           [0009]      FIG. 5  is a block diagram of the handheld electronic device shown in  FIG. 1 . 
       
    
    
       [0010]    Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
       DETAILED DESCRIPTION 
       [0011]    Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to antenna systems. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. 
         [0012]    In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
         [0013]    It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of hand held electronic devices described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform hand held electronic device functions. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. 
         [0014]      FIG. 1  shows a handheld electronic device  100  that is capable of wireless communication. The communication may for example comprise voice communication, image communication, video communication, text communication or other forms of communication. The device  100  includes a housing  102  which supports a single physical button  104  and a touch screen display  106 . The housing  102  also encloses a first antenna  108  and a second antenna  110 . The second antenna  110  is fed via a second antenna coaxial feed cable  112  that runs through the first antenna  108 . Although the device  100  as shown in  FIG. 1  takes the form of a Personal Digital Assistant PDA, which when equipped for cellular telephony is sometimes more recently referred to as a smart phone, alternatively the device may take other forms, such as for example a tablet computer, clam shell style cellular handset or a laptop computer. 
         [0015]      FIGS. 2-3  show front and back views of the first antenna  108 . The device  100  includes a main ground structure  302 . The main ground structure  302  may for example comprise a printed circuit board (PCB) with one or more ground plane layers and/or a stamped metal frame. The main ground structure  302  may serve as a ballast (or ‘counterpoise’) for the first antenna  108  and the second antenna  110 . The first antenna  108  and the second antenna  110  are disposed proximate to the edges of the main ground structure  302 . A channel  202  extends along a peripheral edge  204  of the main ground structure  302 . The second antenna coaxial feed cable  112  and a first antenna coaxial feed cable  206  are routed through the channel  202 . 
         [0016]    The first antenna coaxial feed cable  206  is supported in a hooked end  208  of a clip  210  that is affixed by soldering or rivets or other device or method to the main ground structure  302 . The outer conductor of the first antenna coaxial feed cable  206  connects to a metal feed strip  212 . The inner conductor of the first antenna coaxial feed cable  206  is connected to the feed point  236  of the first antenna  108 . 
         [0017]    The first antenna  108  includes a first planar portion  214  that lies in a plane that is perpendicular to a plane aligned with the main ground structure  302 . The first planar portion  214  includes a impedance matching stub  216  that extends toward the feed strip  212 . An opposite end of the first planar portion  214  includes a high frequency tuning stub  218  that extends in a direction away from the feed strip  212 . 
         [0018]    A grounding conductor  220  extends from the first planar portion  214  at a right angle to the plane containing the first planar portion  214  (in a plane parallel to the plane of the ground structure  302 ) toward the main ground structure  302 . The grounding conductor  220  follows a rectilinear zigzag path that includes a first short segment  222  extending toward the main ground structure  302 , a second longer segment  224  extending in the direction away from the feed strip  212 , and a third short segment  226  which again extends toward the main ground structure  302 . Adapting the zigzag shape attains a longer electrical length to tune the antenna  108  without increasing the space requirement for the antenna. A hooked clip  228  extends from the far end of the third short segment  226  (opposite end from connection to second longer segment  224 ). The second antenna coaxial feed cable  112  runs from the channel  202  under the length of the first antenna  108  and is engaged in the hooked clip  228  so that a conductive connection is formed between the grounding conductor  220  and an outer conductor of the second antenna coaxial feed cable  112 . In this design rather than contend with the issue of a nearby cable disturbing the performance of the first antenna  108 , the cable  112  being routed through is actually electromagnetically integrated into the functioning of the first antenna  108 . 
         [0019]    The first antenna  108  also includes a depending tab  230  which extends perpendicular from the first planar portion  214  (in a direction parallel to the plane of the main ground structure  302 ). Both the grounding conductor  220  and the depending tab  230  extend from a common edge (foreground edge in  FIG. 2 ) of the first planar portion  214 . A dotted line  232  schematically illustrates current flow in the antenna which as shown includes an electrical length increasing bend through the depending tab  230 . 
         [0020]    A signal feed tab  234  extends from the depending tab  230 . Except for an end portion  236 , the signal feed tab  234  lies in a plane that is perpendicular to a plane occupied by the first planar potion  214 , but angled relative to a plane occupied by the depending tab  230 . The end portion  236  is bent so as to lie in a plane parallel to the plane occupied by the depending tab  230 . In this way the end portion  236  of the signal feed tab  234  is located proximate an end of the metal strip  212  used to support the first coaxial feed cable  206  that is used to feed the first antenna  108 . Additionally the end portion  236  of the signal feed tab  234  aligns with an edge of the first planar portion  214  opposite to the edge of the first planar portion  214  from which the depending tab  230  extends. 
         [0021]      FIG. 4  is a graph  400  that includes a plot  402  of signal return loss for the antenna  108  shown in  FIGS. 1-3 . The abscissa of the graph denotes frequency in gigahertz (GHz), and the ordinate denotes magnitude of the reflection coefficient in decibels (dB). As shown in the graph  400  the reflection coefficient includes a first operating band centered at 2.562 GHz which is attributable to a first resonance of the antenna  108 , and a second operating band that extends between 5.03 GHz and 5.8 GHz and is attributable to two resonances of the antenna  108 . These frequency bands are appropriate for IEEE 802.11 communications. It will be apparent to persons of skill in the art that the antenna can be redimensioned and tuned to support communications in alternative frequency bands. 
         [0022]      FIG. 5  is a functional block diagram of the hand held electronic device  100  shown in  FIG. 1 . As shown in  FIG. 5  the device  100  comprises a microprocessor  504 , a program memory  506 , a workspace memory  508 , a display driver  510 , a touch screen controller  514  and a transceiver  512  coupled together through a signal bus  516 . The display driver  510  and the touch screen controller are coupled to the display  106 . And the transceiver  512  is coupled to the first antenna  108  and the second antenna  110 . 
         [0023]    In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.