Abstract:
A dual slot radiator is provided. The dual slot radiator comprises two slot radiating elements of different lengths having a single power feed. The power feed generally comprises a microstrip feed line connected at a first end to a power source and each of the slot radiators at a second end.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Applications 60/552,933, filed Mar. 12, 2004, and 60/566,911, filed Apr. 30, 2004, titled the same, and incorporated herein as if set out in full. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to antennas and, more particularly, dual frequency printed circuit board antennas.  
       BACKGROUND OF THE INVENTION  
       [0003]     Printed circuit board antennas are generally known in the art.  FIG. 1  shows a prior art style printed circuit board antenna  100 . This antenna has a substrate  102 , a ground plane  104 , a microstrip line  106 , a radiating slot  108 , and a shorting strip  110 . While antenna  100  functions well enough it has several drawbacks. Some of the drawbacks include single frequency operation and the microstrip line  106  for a power feed at the slot center.  
         [0004]     Thus, it would be desirous to provide an improved printed circuit board antenna having dual frequency operation and improved power feed.  
       SUMMARY OF THE INVENTION  
       [0005]     To attain the advantages and in accordance with the present invention, a multiband antenna is provided. The multiband antenna comprises a ground plane with a first slot radiator of a first length and a second slot radiator of a second length, the first and second slot radiators have first and second feed ends, and first and second terminating ends, respectively. A single power feed extends from a source end attached to a power source to a radiator end. The radiator end has a first branch connected the radiator and a second branch connected to the second radiator. The two radiators may be of different lengths to facilitate multi-frequencies of operation.  
         [0006]     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 DRAWINGS  
       [0007]      FIG. 1  is a simplified diagram of a prior art antenna;  
         [0008]      FIG. 2  is a simplified diagram of an antenna consistent with an embodiment of the present invention;  
         [0009]      FIG. 3  is a frequency plot of an antenna constructed in accordance with an embodiment of the present invention;  
         [0010]      FIG. 4  is a simplified diagram of another antenna consistent with an embodiment of the present invention; and  
         [0011]      FIG. 5  is a simplified diagram of another antenna consistent with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]     The present invention will now be explained with reference to  FIGS. 2-5 . While  FIGS. 2-5  show embodiments of the present invention, one of ordinary skill in the art on reading the disclosure will understand different arrangements, configurations, and dimensions are possible and the configuration shown in  FIGS. 2-5  should be considered exemplary and not limiting.  
         [0013]      FIG. 2  shows a printed circuit board antenna  200  consistent with an embodiment of the present invention. Antenna  200  is shown on a substrate  202 , but substrate  202  is not necessary for the present invention. When included, substrate  202  is a dielectric material. Antenna  200  comprises a ground plane  204 , a first radiating element  206 , and a second radiating element  208 . First radiating element has a feed end  206   f  and a terminating end  206   t.  Second radiating element has a feed end  208   f  and a terminating end  208   t.    
         [0014]     First radiating element  206  and second radiating element  208  may be straight radiating elements or have zigzag, meanderline, curved, or the like geometries.  
         [0015]     Second radiating element  208  has a L shaped portion  210  at terminating end  208   t.  L shaped portion  210  could have other configurations, such as a C shape, a curve, a straight or I shape, a step shape or the like. Radiating portion  206  could have an alternative configuration at terminating end  206   t  if desired.  
         [0016]     A feed connection  212  is coupled to each first radiating element  206  and second radiating element  208  proximate or at feed end  206   f  and  208   f.  Feed connection  212  comprises a microstrip feed line  214  and a tee connection  216 . Tee connection  216  has a first branch  218  terminating in a short  218   s  that shorts the tee connection to ground plane  204  and a second branch  220  terminating in a short  220   s  that shorts the tee connection to ground plane  204 . Short  218   s  and short  220   s  reside proximate by a short distance d away from first radiating element  206  and second radiating element  208 . Tee connection  216  could take other shapes, such as, a Y shape or the like.  
         [0017]     A power feed  220  connects to the microstrip feed line  214 . If power feed  220  was a coaxial cable power feed, a conductor  222  of coaxial cable would attach to microstrip feed line  214  and a jacket  224  or ground of coaxial cable would attach to ground plane  204 . Placement of tee connection  216  allows for impedance matching. Further, while explained using a coaxial cable as the power feed  220 , any conventional power feed is possible.  
         [0018]     In operation, first radiating element  206  (the shorter element) would operate at a higher frequency and second radiating element  208  (the longer element) would operate at a lower frequency. The elements could be tuned by varying the configuration, dimensions, and the like of each element.  FIG. 3  shows a possible frequency response of an antenna that was constructed in accordance with the present invention. While two radiating elements are shown to provide two bands of operation, additional radiating elements would allow antenna  200  to operate at still additional frequencies.  
         [0019]     While antenna  200  is a satisfactory antenna and an improvement over prior art designs, the size of antenna  200  could be reduced. In particular,  FIG. 4  shows a half slot antenna  400 . Half slot antenna  400  is shown on a substrate  402  (but substrate  402  is not necessary for the present invention). Further, while antenna  400  is referred to as half slot antenna  400 , one of ordinary skill in the art will recognize on reading the disclosure that half slot is used generically and the present invention should not be limited by the term half. Antenna  400  comprises a ground plane  404 , a first radiating element  406 , and a second radiating element  408 . First radiating element  406  has a feed end  406   f  and a terminating end  406   t.  Second radiating element  408  has a feed end  408   f  and a terminating end  408   t.    
         [0020]     A feed connection  410  is coupled to each of first radiating element  406  and second radiating element  408  proximate or at feed ends  406   f  and  408   f,  respectively. Feed connection  410  comprises a microstrip feed line  412  and a tee connection  414  originating from a feed edge  416  of ground plane  404 . Feed line  412  and tee connection  414  are similar to the devices described in connection with  FIG. 2  and will not be re-explained in conjunction with  FIG. 4 . Ground plane  404  has a radiating edge  420  opposite feed edge  416 . As shown, radiating elements  406  and  408  terminate at radiating edge  420  of ground plane  404 . Thus, ground plane  404  can be of a reduced size. Further, assuming antenna  200  and half slot antenna  400  are designed to function at the same operating frequencies, the overall length of radiating element  406  is about ½ the overall length of radiating element  206  and the overall length of radiating element  408  is about ½ the overall length of radiating element  408  (hence the phrase half slot antenna). Thus, the overall size of antenna  400  is reduced as compared to antenna  200 .  
         [0021]     Referring now to  FIG. 5 , an antenna  500  is shown. Antenna  500  as a first radiating element  506  and a second radiating element  508 . First radiating element  506  has a terminating end  508   t  that terminates at a radiating edge of ground plane  502 . Thus, first radiating element functions similar to radiating element  406 . Second radiating element  508  is situated on ground plane  502  and functions similar to radiating element  208 . In other words, antenna  500  is a hybrid between antenna  200  and antenna  400 . While radiating element  508  could be the half slot element, it makes more design sense to have the lower frequency element as the half slot because the lower frequency element requires a greater length than the higher frequency element.  
         [0022]     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.