Patent Publication Number: US-7589692-B2

Title: Planar inverted F antenna tapered type PIFA with corrugation

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is the National Phase application of International Application No. PCT/KR2004/002654, filed Oct. 15, 2004, which designates the United States and was published in English. This application, in its entirety, is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a radiation patch for a planar inverted F antenna; and, more particularly, to the radiation patch having an asymmetric shape of linearly-tapered rectangle with a plurality of corrugated hollows for a planar inverted F antenna in order to provide wide bandwidth characteristic. 
   DESCRIPTION OF RELATED ARTS 
   A planar inverted F antenna is a modified microstrip antenna having a shape of inverted F. 
     FIG. 1  is a diagram illustrating a conventional planar inverted F antenna in accordance with a prior art. 
   Referring to  FIG. 1 , the conventional planar inverted F antenna  100  includes a rectangular radiation patch  110  having a size of a length L P  and width W P , a shorting plate  120 , a feeding line  130  and a ground plane  140 . 
   The shorting plate  120  is attached between the ground plane  140  and the rectangular radiation patch  110 . The feeding line  130  supplies electric power to the rectangular radiation patch  110 . 
   The planar inverted F antenna has been widely used in a wireless communication field since its advantages such as simple structure, low profile, easy to manufacture and low cost. 
   However, the conventional planar inverted F antenna has a size of ¼ of a wavelength, which is smaller than a general size of conventional microstrip antenna, which is ½ of a wavelength, but the conventional planar inverted F antenna is still large to be implemented into a mobile terminal. Accordingly, there has been demanded a technology reducing the size of the conventional planar inverted F antenna Furthermore, a technology maintaining or widening a bandwidth of the conventional planar inverted F antenna has also been demanded since the bandwidth of the conventional planar inverted F antenna is also reduced in correspondence to the size of the conventional planar inverted F antenna. 
   For overcoming the above mentioned drawback, Terry Kinchun Lo and Yeongming Whang disclose a technology for widening a bandwidth by punching various shapes of slots such as shapes of L or U and uses various feeding methods. The bandwidth is widened according to a length and a width of the slots. However, it is getting more complicated for designing the conventional planar inverted F antenna. 
   Furthermore, Kathleen L. Virga and Yahya Rahmat-Smaii disclose another technology for widening a bandwidth in “Low Profile Enhanced-Bandwidth PIFA antenna for Wireless Communication Packaging”, IEEE TRANSACTION ON MICROWAVE THEORY AND TECHNIQUES, vol. 45, No. 10, pp 1879-1888, October, 1997. For widening the frequency bandwidth, Kathleen and Yahya implement additional patches to an antenna or two patches connected by timing diode as a radiation device. As a result, a frequency bandwidth is getting wider, e.g., 14% of bandwidth is increased than the linear antenna or dipole antenna. However, the antenna introduced by Kathleen and Yahya is complicated and a manufacturing cost is increased. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a planar inverted F antenna for widening a frequency bandwidth by providing a linearly tapered rectangular shape of radiation patch and forming a predetermined number of corrugated hollows having a predetermined length and width on the radiation patch. 
   It is another object of the present invention to provide a planar inverted F antenna for widening a frequency bandwidth and obtaining flexibility of antenna design by providing a radiation patch having an asymmetric shape of linearly tapered rectangular having a plurality of corrugated hollows. 
   In accordance with another aspect of the present invention, there is provided a planar inverted F antenna having a radiation patch, including: a first radiation patch for radiating a signal; a ground plate for grounding the first radiation patch; a feeding line for supplying an electric power to the first radiation patch; a short plate having one side coupled to the first radiation patch and other side coupled to the ground plate for shorting the first radiation patch, wherein the first radiation patch having an asymmetrical shape of linearly tapered rectangle and has one or more corrugated hollows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the present invention will become better understood with regard to the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a diagram illustrating a conventional planar inverted F antenna in accordance with a prior art; 
       FIG. 2  is a diagram illustrating a planar inverted F antenna in accordance with a preferred embodiment of the present invention; and 
       FIG. 3  is a diagram showing a planar inverted F antenna in accordance with another preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, a planar inverted F antenna in accordance with a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings. 
     FIG. 2  is a diagram illustrating a planar inverted F antenna in accordance with a preferred embodiment of the present invention. 
   As shown in  FIG. 2 , the planar inverted F antenna  200  includes a radiation patch  210 , an additional radiation patch  240 , a shorting plate  220 , a feeding line  230  and a ground plate  250 . 
   The shorting plate  220  is equipped in between the ground plate  250  and the radiation patch  210 . One side of the shorting plate  220  is coupled to the radiation patch  210  and other side of the shorting plate  220  is coupled to the ground plate  250 . The shorting plate  220  has a function to short the radiation patch  210 . 
   The feeding line  230  connected to the radiation patch  210  through the ground plate  250  has a function to supply electric power to the radiation patch  210 . 
   The radiation patch  210  of the present invention is an asymmetrical shape of linearly tapered rectangle having a plurality of corrugated hollows along with a tapered line and each of the corrugated hollows has a predetermined length h c  and a predetermined width w c . By providing the asymmetrical shape of linearly tapered rectangle having a plurality of corrugated hollows, a frequency bandwidth of the antenna is widened. 
   Generally, various paths of electric current must be included on the radiation patch for widening the frequency bandwidth of the antenna. That is, various frequencies of electric current must be resonated on the radiation patch. In the present invention, the radiation patch  210 , which is the asymmetrical shape of linearly tapered rectangle, induces various paths of electric current comparing to a square shape of a conventional antenna. Accordingly, the frequency bandwidth of the antenna is widened. 
   In the present invention, a length of A or B of the radiation patch  210  are determined according to desired resonant frequency. Also, a ratio of taper in the radiation patch  210  is determined according to the desired resonant frequency. 
   Furthermore, a plurality of the corrugated hollows makes a length of current path following along the radiation patch  210  longer. That is, it makes electrical length of the radiation patch longer. 
   The number of the corrugated hollows formed on the radiation patch  210 , the length h c  and the width w c  are determined according to the desired resonant frequency. Furthermore, a plurality of the corrugated hollows have different length h c  and the width w c . 
   The additional radiation patch  240  extends the electrical length of the radiation patch  210 . The additional radiation patch  240  is coupled at one side of the radiation patch  210  which is opposite end having the shorting plate  220 . A length h.sub.s of the additional radiation patch  240  must be shorter than the length h of the shorting plate  220 . Also, the length h.sub.s and a width w.sub.s of the additional radiation patch  240  are determined according to the desired resonant frequency. 
   The shorting plate  220  has a predetermined length h and width ω for adjusting the desired resonant frequency and the shorting plate  220  can be coupled either of a length side C and a width side D of the radiation patch  210 . 
   The feeding line  230  can be arranged any side of the radiation patch  210 . In the preferred embodiment of the present invention in  FIG. 2 , the feeding line  230  is directly coupled to the radiation patch  210  which is a probe method of feeding line and however, it can be coupled to the radiation patch according to a coupling method. 
     FIG. 3  is a diagram showing a planar inverted F antenna in accordance with another embodiment of the present invention. 
   As shown in  FIG. 3 , the planar inverted F antenna  300  has a structure identical to the planar inverted F antenna  200  in  FIG. 2  excepting a location of an additional radiation patch  310 . The additional radiation patch  310  is coupled to a length side A of the radiation patch  210  having an asymmetric shape of linearly tapered rectangular having a plurality of corrugated hollows. Since the other structure of the planar inverted F antenna  300  is the same as the planar inverted F antenna  200  in  FIG. 2 , detailed descriptions of the planar inverted F antenna  300  are omitted. 
   As mentioned above, the present invention can widen the frequency bandwidth of the planar inverted F antenna by shaping a radiation patch having an asymmetric shape of a linearly tapered rectangle and forming a plurality of corrugated hollows on the radiation patch. 
   Also, the present invention can provide longer electrical length compared to similar size of conventional antenna by a planar inverted F antenna having a linearly tapered rectangle shape of radiation patch having a plurality of corrugated hollows and additional radiation patch. 
   Furthermore, the present invention can be implemented in various application fields by providing a linearly tapered rectangle shape of radiation patch having a plurality of corrugated hollows in a planar inverted F antenna. 
   The present invention contains subject matter related to Korean patent application No. KR 2003-0072082, filed in the Korean patent office on Oct. 16, 2003, the entire contents of which being incorporated herein by reference. 
   While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.