Abstract:
The present invention provides a flexible film antenna. The flexible film antenna includes a radiating element comprising a conductive trace on a flexible film. Flexible film is mounted on a core. The core comprises at least two parts that are releasably coupled together in snap or sliding relation. A feed post extends out a base of the core to connect to a power feed. Finally, a protective housing can be molded over the antenna.

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/502,507, titled the same, filed Sep. 12, 2003 and incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to antennas and, more particularly, to overmolded antenna systems. 
   BACKGROUND OF THE INVENTION 
   Cellular telephone, PDA, and other wireless devices send and receive data using radio frequency (“RF”) transmissions. The RF transmissions are sent and received through an antenna. One currently useful antennal is a flex film antenna, which are commonly used in the art. 
   Conventionally, flex film antennas are constructed using one of two ways. The first methodology involves a snap together antenna. The second methodology involves an overmolded single core. Neither of these designs is satisfactory. Using these designs, the following and other problems still exist with flex film antennas:
         A single piece core component is required in existing simplified overmolded flex film antenna designs to facilitate the plastic molding process. This design excludes the internal volume of core component as a possible location for the flex film radiator element.   Existing overmolded flex film antenna radiators antenna systems have a limited usable radiator surface typically limited to the radial surface area of the single piece core component.   The electrical connection of the flex film to the metallic threaded connector (radio interface) on existing designs use solder or axial compression. Soldering is expensive and introduces variation in the amount of solder deposited, thus variation in antenna performance from antenna to antenna. Axial compression interface (used on “snap together” designs) relies on a component of the antenna to apply compressive load to the flex film. This component is typically the outer sheath that is susceptible to the external environment and possible damage from drop. Additionally the sheath is typically a polymer which overtime will lose its material properties as it is under constant tensile load in these designs. As the sheath weakens, the compressive load diminishes thus increasing the likelihood of intermittent flex film to metallic connector electrical connection.   Flex film tears easily when a load is applied to the material. A unique assembly interface is needed to accomplish a consistent interface and a manufacturable design.       

   Thus, it would be desirous to develop a flex film antenna that addressed these and other problems. 
   SUMMARY OF THE INVENTION 
   The present invention provides a flexible film antenna. The flexible film antenna includes a radiating element comprising a conductive trace on a flexible film. The flexible film is mounted on a core. The core comprises at least two parts that are releasably coupled together in snap or sliding relation. A feed post extends out a base of the core to connect to a power feed. Finally, a protective housing can be molded over the antenna. 
   The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, serve to explain the principles thereof. Like items in the drawings are referred to using the same numerical reference. 
       FIG. 1  is a partially exploded, perspective view of an antenna comprising an embodiment of the present invention without the housing; 
       FIG. 2  is a partially exploded, perspective view of the core of  FIG. 1  comprising an embodiment of the present invention without the housing; 
       FIG. 3  is a partially exploded, perspective view of the base of the antenna of  FIG. 1 ; 
       FIG. 4  is a cutaway of the antenna of  FIG. 1 ; and 
       FIG. 5  is a cross-sectional view of the antenna of  FIG. 4 . 
   

   DETAILED DESCRIPTION 
   The present invention will be further explained with reference to the  FIGS. 1–4 . In particular,  FIGS. 1–4  show an overmolded antenna with a multi piece core assembly and flex film radiating element consistent with an embodiment of the invention. The multi piece core increases the usable surface area for the radiating flex film element. This is accomplished by “threading” the flex film in between the core pieces, thus using the internal volume region of the core system. ( FIG. 1 ). The actual placement of the flex film radiation element within the internal volume is dependent, in part, on design choice and, in part, on functional requirements of the antenna. 
     FIG. 1  shows portions of an antenna  100 . Antenna  100  comprises a core  102  or support structure on which a flexible film  104  is wound. A power feed element  106  connects to a base  108  of antenna  100 . 
   Flexible film  104  comprises a non-conductive material  110 , typically a flexible plastic, rubber, or the like, with one or more conductive traces  112 , such as copper or the like, on the non-conductive material  110 . The size, shape, dielectric constant, etc. of the non-conductive material and the size, shape, and placement of the conductive trace(s)  112  are largely a matter of design choice and radiating characteristics of antenna  100 . Flexible film  104  comprises a power connection  114 . Power connection  114  comprises a portion of non-conductive material  106  and conductive trace  108  operatively coupled to power feed element  106 , as will be explained further below. Power connection  114  is shown with a single power feed, but multiple power feeds could be used instead of the single feed line as shown. Further, conductive traces  112  shown could be a single trace or multiple traces as shown. 
   Referring now to  FIG. 2 , core  102  is shown in more detail. Core  102  comprises at least two releasably coupled parts, upper part  202  and lower part  204 . Upper and lower are relative terms and used only in connection with  FIG. 2  for reference. Upper and lower should not be considered limiting. 
   Upper part  202  has an upper support section  206  and a top portion  208 . Upper support section  206  comprises a half cylinder with a convexly shaped outer surface  210  and a substantially flat lower part interface  212 . Top portion  208  comprises a full cylinder with a convexly shaped outer surface  214 . Top portion  208  has at least one upper recess  216  extending below a plane defined by lower part interface  212 . Upper support section  206  has at least one upper protrusion  218  extending from an upper part base  220 , which is opposite top portion  208 . The at least one upper protrusion  218  resides just above lower part interface  212 . At least one alignment recess  222  extends along a length lower part interface  212 . Upper part  202  may have one or more relief troughs  226  as necessary. Top portion  208  has a guide ridge  224  extending about outer surface  214 . Upper part  202  is described with several components, however, one of ordinary skill in the art on reading the disclosure will now understand that upper part could be a single molded piece of plastic or multiple pieces of molded plastic coupled together. 
   Lower part  204  has a lower support section  230  and a bottom portion  232 . Lower support section  230  comprises a half cylinder with a convexly shaped outer surface  234  and a substantially flat upper part interface  236 . Bottom portion  232  comprises a fully cylinder with a convexly shaped outer surface  238 . Bottom portion  232  comprises at least one lower recess  240  above upper part interface  236  that is shaped to slidably couple to the at least one upper protrusion  218 . Lower support section  230  comprises at least one lower protrusion  242  below upper part interface  236  that is shaped to slidably couple the at least one upper recess  216 . An alignment tab  244  resides on upper part interface  236  and is shaped to slidably couple to alignment recess  222 . Alignment tab  244  also engages an alignment cutout  116  (See  FIG. 1 ) in the flexible film to assist in aligning the flexible film  104  on core  102 . 
   Bottom portion  232  has a guide ridge  224 , a power feed recess  246 , a power connection slot  248 , and at least one power feed support post  250 . Power feed support post  250  is shown as two power feed support posts  250  or tabs extending into power feed recess  246 . It has been found using two separated power feed support posts  250  inhibits tearing of flexible film  104 , which can cause a power failure or disconnect. Power connection slot  248  could form a through hole or bore in the at least one power feed support post  250  if desired. 
   As shown, core  102  has a generally cylindrical shape that converges from bottom portion  232  to top portion  208 . The shape of core  102  could be as shown, a straight cylinder, a cubic shape, a conical shape, or other polygonal shapes as a matter of design choice. However, to the extent core  102  has edges, the edges should be beveled or chamfered to reduce damage to flexible film  104 . 
   Referring back to  FIG. 1 , flexible film  104  and core  102  may be assembled by inserting power connection  114  through power connection slot  248  such that power connection  114  extends from bottom portion  232 . Further cutout  116  would be aligned with alignment tab  244  such that flexible film  104  resides one upper part interface  236  and extend beyond outer surface  234 . Upper part  202  would be arranged such that alignment tab  244  aligns with alignment recess  222 . Upper part  202  would be pushed down on lower part  204  until lower part interface  212  substantially abutted flexible film  104 . Upper part  202  would than be slidably moved along lower part  204  until at least one upper protrusion  218  and at least one lower recess  240 , and at least one lower protrusion  242  and at least one upper recess  216  slidably engaged forming a puzzle lock arrangement. 
   Flexible film  104  would than be wrapped or threaded around outer surfaces  210 ,  214 ,  234 , and  238 . Flexible film  104  further comprises an adhesive  118  such that when flexible film  104  is completely wrapped or threaded around core  102 , adhesive  118  would couple flexible film  104  to itself or one of outer surfaces  210 ,  214 ,  234 , and  238  to inhibit unraveling of flexible film  104 . 
   Referring to  FIGS. 3 and 5 , power feed element  106  is described in more detail. Power feed element  106  comprises a plug portion  300  that fits into power feed recess  246 . Plug portion  300  comprises a base  302  having an annular ledge  304 , which could be contiguous as shown or at least one tab, on which bottom portion  232  resides. Extending into power feed recess  246  is an outer plug surface  306 . Outer plug surface  306  defines an inner plug recess  308 . Inner plug recess  308  is shaped to cooperatively engage at least one power feed support post  250 . Power feed support post  250  may not extend fully into inner plug recess  308 , which may leave a small gap G. 
   Generally, core  102  is formed from non-conductive plastic. Power feed element  106  is formed from conductive metal. Referring specifically to  FIG. 3 , power connection  114  is bent over the at least one power feed support post  250 . Power feed element  106  is plugged into power feed recess  246  such that outer plug surface  306  plugs into power feed recess  246  and the at least one power feed support post  250  snuggly fits (i.e., plugs) into inner plug recess  308  such that the conductive trace  112  on power connection  114  engages metal plug portion  300  forming a radial power feed connection. Forming core  102  of plastic and power feed element  106  from metal reduces failures do to plastic fatigue. 
   Once power feed element  106  is plugged into power feed recess  246 , a housing  400  may be applied around core  102  forming antenna  100 . Optionally, housing  400  can be formed by injection molding housing  400  around the device by placing power feed element  106  in a recess in a mold. The device is stabilized by connecting a portion of the top portion  208  to prongs, which may result in an annular void  402  at the peak  404  of housing  400 . 
   Guide ridges  224  are useful in aligning flexible film  104  about core  102 , but also serve to inhibit flexible film  104  from peeling or unraveling from core  102  when housing  400  is molded about core  102 . Further, a portion  120  of flexible film  104  may be cut to remove edges that the molding may cause to peel, unravel, or tear. 
   While the invention has been particularly shown and described with reference to an embodiment thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention.