Patent Publication Number: US-6342868-B1

Title: Stripline PCB dipole antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a stripline PCB dipole antenna, and more particularly to a dual-fed co-planar stripline PCB dipole antenna used in an electronic device for receiving and/or transmitting electromagnetic signals. 
     2. Related Art 
     In the communications field, dipole antennas have been widely used for a long time for effectively receiving and transmitting electromagnetic signals. Most electronic devices use single dipole antennas. Conventionally, a single dipole antenna has three radiation planes, namely an XY-plane, an XZ-plane and a YZ-plane. Generally, only one of these radiation planes has preferred radiation efficiency, and the other radiation planes are disregarded. Moreover, a feeding device of a conventional single dipole antenna is complex and occupies a lot of space. 
     An antenna disclosed in U.S. Pat. No. 4,605,931 utilizes a crossover feeding system. The system comprises pairs of a first feeder apparatus and a second feeder apparatus, one feeder apparatus crossing over the other. Each pair of the crossed first and second feeder apparatuses has a first port and a second port for transmitting a first signal therebetween, and a third port and a fourth port for transmitting a second signal therebetween. The system reduces interaction between signals, and eliminates back feeding of signals. However, the system is too complex to be practically implemented. 
     Taiwan Patent Application No. 87112281 discloses a circular polarized microstrip antenna that has a short adjustable metal microchip on an edge of a fixed metal microchip. A feed point of the microstrip antenna is on the short adjustable metal microchip or a cross-line thereof which is oriented at 45°. The metal microchip is installed on a grounding plane. The microstrip antenna has preferred radiation efficiency in the XZ-plane and the YZ-plane. However, the microstrip antenna is also very complex. It requires a large space, and cannot be easily integrated into communications equipment. 
     Other antennas are disclosed in U.S. Pats. Nos. 4,069,483 and 6,091,366. They all utilize only one of the three radiation planes to provide radiation efficiency. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a stripline PCB dipole antenna capable of switching between two of the three radiation planes, namely the XY-plane, the XZ-plane and the YZ-plane, to achieve optimum diversity reception efficiency. 
     Another object of the present invention is to provide a stripline PCB dipole antenna which reduces any adverse influences that wiring paths of feeder RF cables may have on the characteristics of the antenna. 
     A further object of the present invention is to provide a feeding method whereby two dipole antennas are fed through feed patches to make full use of two of the three radiation planes and thereby provide optimum diversity reception efficiency. 
     To achieve the above-mentioned objects, a stripline PCB dipole antenna in accordance with the present invention for placing in an electronic device includes a substrate, a T-shaped first dipole antenna disposed on a surface of the substrate, a T-shaped second dipole antenna disposed on an opposite surface of the substrate and perpendicular to the first dipole antenna, and first and second feeder apparatuses feeding the antennas near respective edges of the substrate. The positioning of the feeder apparatuses reduces any adverse influences that the wiring paths of the feeder apparatuses may have on the characteristics of the stripline PCB dipole antenna. 
     The stripline PCB dipole antenna utilizes a switch mechanism of dual polarized radiation to switch between two of the three radiation planes, namely the XY-plane, the XZ-plane and the YZ-plane. The stripline PCB dipole antenna thus achieves optimum diversity reception efficiency under the control of an external device. 
     These and additional objects, features and advantages of the present invention will become apparent after reading the following detailed description of a preferred embodiment of the invention taken in conjunction with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a stripline PCB dipole antenna in accordance with the present invention. 
     FIG. 2 is a perspective view of the stripline PCB dipole antenna of FIG.  1 . 
     FIG. 3 is a graph of experimental results for the stripline PCB dipole antenna of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a stripline PCB dipole antenna in accordance with the present invention includes a substrate  3 , a first dipole antenna  1 , a second dipole antenna  2 , a first feeder apparatus  41  and a second feeder apparatus  42 . 
     The first and second dipole antennas  1 ,  2  are generally T-shaped, and have substantially the same structure, shape and size. The first dipole antenna  1  is disposed on a first surface  31  of the substrate  3 , and the second dipole antenna  2  is disposed on a second surface  32  of the substrate  3  which is opposite to the first surface  31 . The first and second dipole antennas  1 ,  2  are generally perpendicular to each other. Each first and second dipole antenna  1 ,  2  includes a first dipole cell  10  and a second dipole cell  20 . 
     In the preferred embodiment of the invention, the first dipole cell  10  is an integrated patch including a first feed patch  11 , a first arm  12  and a second arm  13 . As shown in FIG. 1, the first feed patch  11  is generally shaped as a right-angled trapezoid. The first feed patch  11  has a first lower edge  111 , a first upper edge  112 , a first facing edge  113 , and a first bevel edge  114 . The first arm  12  is rectangular, and has a first long edge  121  and a first short edge  122 . The first long edge  121  is parallel with the first facing edge  113  of the first feed patch  11 . The first short edge  122  is parallel with the first upper and lower edges  112 ,  111  of the first feed patch  11 . The second arm  13  is shaped as an isosceles trapezoid, and has an upper side  132  and a lower side  131 . The lower side  131  is connected with the first long edge  121  of the first arm  12 . The upper side  132  is connected with an edge (not labeled) of the first feed patch  11  which is between the first bevel edge  114  and the first lower edge  111 . 
     The second dipole cell  20  is an integrated patch including a second feed patch  21 , a third arm  23  and a fourth arm  24 . The second feed patch  21  is substantially the same size as the first feed patch  11  of the first dipole cell  10 , and is disposed symmetrically opposite to the first feed patch  11 . A space (not labeled) exists between the first and second feed patches  11 ,  21 . The second feed patch  21  has a second lower edge  211 , a second upper edge  212 , a second facing edge  213 , and a second bevel edge  214 . The second lower edge  211  is collinear with the first lower edge  111  of the first dipole cell  10 . The third and fourth arms  23 ,  24  are both rectangular. The third arm  23  has a third long edge  231 , a third short edge  232 , and a fourth short edge  233 . The fourth arm  24  has a second long edge  241 , and a second short edge  232 . The second long edge  241  of the fourth arm  24  is parallel with the first long edge  121  of the first arm  11 . The second short edge  242  of the fourth arm  24  is parallel with the first lower edge  111  of the first arm  11 . The third long edge  231  of the third arm  23  and the second lower edge  211  of the second feed patch  21  are collinear. The fourth short edge  233  of the third arm  23  is connected with the second long edge  241  of the fourth arm  24 . The third short edge  232  of the third arm  23  is connected with an edge (not labeled) of the second feed patch  21  which is between the second bevel edge  214  and the second lower edge  211 . 
     As shown in FIG. 2, each first and second feed patch  11 ,  21  respectively has a feed point  51 ,  52  defined thereon. 
     The first and the second dipole antennas  1 ,  2  are respectively fed through the first and second feeder apparatuses  41 ,  42 . In the preferred embodiment of the invention, the first and second feeder apparatuses  41 ,  42  are coaxial RF cables which each include a signal line and a ground line. A signal line  411  and a ground line  412  of the first feeder apparatus  41  are respectively connected with the first feed patch  11  and the second feed patch  21  by welding to the feed points  51  and  52  respectively. The second feeder apparatus  42  is also welded on the first surface  31  of the substrate  3 . The second feeder apparatus  42  is connected with feed patches of the second dipole antenna  2  on the second surface  32  of the substrate  3  via through holes  60  (shown in FIG.  1 ). 
     The first and second feed patches  11 ,  21  of the first and the second dipole antennas  1 ,  2  are located near edges of the substrate  3 , so that the first and the second dipole antennas  1 ,  2  can be fed from sides of the substrate  3 . This reduces any adverse influences that the wiring paths of the feeder apparatuses  41 ,  42  may have on the characteristics of the stripline PCB dipole antenna. 
     Voltage Standing Wave Ratio (VSWR) is a standard criterion used in measuring antenna characteristics in a given frequency range. In general, a VSWR greater than 1.0 is considered reasonable in the communications field. In addition, prevailing industry standards of antenna design dictate that for a given frequency range, a VSWR less than 2.0 is required for effective operation. 
     FIG. 3 is a graph of experimental results for the stripline PCB dipole antenna, showing VSWR varying with frequency. The results show that the VSWR of each of the first and second dipole antennas  1 ,  2  is less than 2.0 in the frequency range of 2.4-2.5 GHz. These results comply with industry-standard antenna design specifications. 
     The stripline PCB dipole antenna according to the present invention which includes the first and second dipole antennas  1 ,  2  placed on the same substrate  3  and perpendicular to each other can utilize a switch mechanism of dual polarized radiation to switch between two of the three radiation planes, namely the XY-plane, the XZ-plane and the YZ-plane. The switch mechanism can be controlled by an external device. The stripline PCB dipole antenna thus achieves optimum diversity reception efficiency. 
     In summary, the stripline PCB dipole antenna of the present invention overcomes the problems of conventional technology and achieves better efficiency for receiving and/or transmitting electromagnetic signals. While the present invention has been described with reference to a specific embodiment thereof, the description is illustrative and is not to be construed as limiting the invention. Various modifications to the present invention may be made to the preferred embodiment by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.