Abstract:
An antenna including a first monopole radiating element having a galvanic connection to an antenna feed and second and third monopole radiating elements having a capacitive connection to the antenna feed.

Description:
REFERENCE TO RELATED APPLICATIONS 
   The present application is related to U.S. Provisional Patent Application Ser. No. 60/654,013 filed Feb. 17, 2005, and entitled CERAMIC FED MULTI-POLE ANTENNA and to U.S. Provisional Patent Application Ser. No. 60/673,588 filed Apr. 21, 2005, and entitled ANTENNAS, the disclosures of which are hereby incorporated by reference and priority of which is hereby claimed pursuant to 37 CFR 1.78(a) (4) and (5)(i). 

   FIELD OF THE INVENTION 
   The present invention relates to antennas generally and more particularly to capacitive feed antennas. 
   BACKGROUND OF THE INVENTION 
   The following patent documents are believed to represent the current state of the art: 
   U.S. Pat. Nos. 6,680,705 and 5,764,190. 
   SUMMARY OF THE INVENTION 
   The present invention seeks to provide an improved capacitive antenna. 
   There is thus provided in accordance with a preferred embodiment of the present invention an antenna including a first monopole radiating element having a galvanic connection to an antenna feed and second and third monopole radiating elements having a capacitive connection to the antenna feed. 
   In accordance with a preferred embodiment of the present invention the antenna also includes a capacitor providing the capacitive connection, the capacitor including a dielectric cylinder supporting the second and third monopole radiating elements and a conductive connection assembly extending interiorly of the dielectric cylinder and having a galvanic connection with the antenna feed. 
   In accordance with another preferred embodiment of the present invention the second and third monopole radiating elements are defined by a single bent wire having first and second portions having differing lengths. Preferably, the first and second portions having differing lengths have respective first and second ends which lie in mutually spaced coplanar overlapping relationship. Additionally or alternatively, the antenna feed is integrally formed with the first monopole radiating element. 
   There is also provided in accordance with a further preferred embodiment of the present invention an antenna including first and second monopole radiating elements having a galvanic connection to an antenna feed and a third monopole radiating element having a capacitive connection to the antenna feed. 
   In accordance with a further preferred embodiment of the present invention the antenna also includes a capacitor providing the capacitive connection, the capacitor including a dielectric cylinder supported on the second and third monopole radiating elements and supporting the third monopole radiating element. 
   In accordance with yet a further preferred embodiment of the present invention the first and second monopole radiating elements are defined by a single bent wire having first and second portions having differing lengths. Preferably, the first and second portions having differing lengths have respective first and second ends which lie in mutually spaced coplanar overlapping relationship. 
   In accordance with an additional preferred embodiment of the present invention the antenna feed engages an electrically conductive surface of a printed circuit board. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
       FIGS. 1A ,  1 B,  1 C and  1 D are respective simplified exploded view, pictorial, top view and sectional view illustrations of a preferred embodiment of an antenna constructed and operative in accordance with the present invention, the sectional illustration being taken along respective section lines ID-ID in  FIG. 1C ; and 
       FIGS. 2A ,  2 B,  2 C and  2 D are respective simplified exploded view, pictorial, top view and sectional view illustrations of another preferred embodiment of an antenna constructed and operative in accordance with the present invention, the sectional illustration being taken along respective section lines IID-IID in  FIG. 2C . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference is now made to  FIGS. 1A-1D , which illustrate an antenna constructed and operative in accordance with a preferred embodiment of the present invention. 
   As seen in  FIGS. 1A-1D , the antenna comprises an antenna feed  100 , which is typically integrally formed with a first monopole radiating element  102 . The antenna feed  100  is preferably formed as a bent spring and is arranged to engage an electrically conductive surface  104  of a printed circuit board  106 . 
   A fastener  110 , preferably formed of an electrically conductive material, retains the antenna feed  100  and the monopole radiating element  102  in mechanical and electrical engagement with an electrically conductive element  112 , preferably by being press-fit in a bore  114  formed therein. 
   Electrically conductive element  112  preferably includes a generally cylindrical portion  116  and a top flange  118 . A dielectric sleeve  120  is preferably press fit about cylindrical portion  116 . Second and third monopole radiating elements  122  and  124  are preferably defined by a single bent metal wire or other element  126  having respective first and second portions of differing lengths. Element  126  is preferably retained onto an outer surface of dielectric sleeve  120  and is preferably mechanically seated in a suitable recess  128  formed on the outer surface of dielectric sleeve  120 . Element  126  is electrically insulated from top flange  118  by an insulative ring  130 . 
   Preferably, the second and third radiating elements  122  and  124  have respective first and second ends  132  and  134  which lie in mutually spaced coplanar overlapping relationship. 
   It is appreciated that in an alternative embodiment, additional monopole radiating elements, in addition to elements  122  &amp;  124 , may be provided by suitable configuration of element  126 . 
   Reference is now made to  FIGS. 2A-2D , which illustrate an antenna constructed and operative in accordance with another preferred embodiment of the present invention. 
   As seen in  FIGS. 2A-2D , the antenna comprises an antenna feed  200 , which is preferably formed as a bent spring and is arranged to engage an electrically conductive surface  204  of a printed circuit board  206 . 
   A fastener  210 , preferably formed of an electrically conductive material, retains the antenna feed  200  in mechanical and electrical engagement with an electrically conductive element  212 , preferably by being press-fit in a bore  214  formed therein. 
   Electrically conductive element  212  preferably includes a generally cylindrical portion  216  and a top flange  218 . A conductive sleeve  220  is preferably press fit about cylindrical portion  216 . First and second monopole radiating elements  222  and  224 , are preferably defined by a single bent metal wire or other element  226  having respective first and second portions of differing lengths. Element  226  is preferably retained onto an outer surface of conductive sleeve  220  and is preferably mechanically seated in a suitable recess  228  formed on the outer surface of conductive sleeve  220 . 
   Preferably, the first and second radiating elements  222  and  224  have respective first and second ends  232  and  234  which lie in mutually spaced coplanar overlapping relationship. 
   A third monopole radiating element  240  is preferably capacitively fed by being insulatively mounted onto element  226 . 
   An electrically insulative element  242 , which preferably includes a generally cylindrical portion  246  and a top flange  248 , is mounted at a bend  249  in element  226 . An electrically insulative sleeve  250  is preferably press fit about cylindrical portion  246 . Third monopole radiating element  240  is preferably retained onto an outer surface of insulative sleeve  250  and is preferably mechanically seated in a suitable recess  258  formed on the outer surface of insulative sleeve  250  and retained therein by an insulative retaining ring  260 . 
   It is appreciated that in an alternative embodiment, additional monopole radiating elements, in addition to elements  222  &amp;  224 , may be provided by suitable configuration of element  226 . 
   It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.