Patent Publication Number: US-8115685-B2

Title: Flat antenna structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a flat antenna structure and an electronic device having the flat antenna structure, and more particularly, the present invention relates to a flat antenna structure capable of adjusting antenna characteristics and an electronic device having the flat antenna structure. 
     2. Description of the Related Art 
     Wireless communication products are increasingly ubiquitous in everyday life. The antenna plays an important role in a wireless communication system for receiving and transmitting electromagnetic waves. There are several types of antenna. A flat antenna is both cheap and easy to connect to a circuit. 
     Currently, a flat antenna of the prior art is a circular plate made of Teflon compound with two parallel copper layers printed on opposite sides. Teflon is one kind of polytetrafluoroethylene resin. Because Teflon consists of carbon and fluorine without hydrogen, it will not react with oxygen. Teflon, which is heat-resistant, cold-resistant, corrosion-resistant, non-adhesive, and self-lubricative, has a low friction coefficient and a low dielectric constant. Teflon is usually used as the base material of the flat antenna due to this low dielectric constant. 
     Teflon is expensive and difficult to recycle, and the manufacturing processes may cause waste of materials. Therefore, a new antenna structure is required to solve problems of the prior art. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a flat antenna structure using another material to replace Teflon. 
     It is another object of the present invention to provide a flat antenna structure capable of adjusting antenna characteristics. 
     To achieve the object mentioned above, the invention provides a flat antenna structure and an electronic device having the flat antenna structure. The flat antenna structure comprises a first metal plate, an intermediate layer, a metal ring, and a second metal plate. The intermediate layer has a first hole, and the intermediate layer is installed above and connected to the first metal plate. The metal ring is connected to the first metal plate through the first hole. The second metal plate has a second hole. The second metal plate is connected to the metal ring and the first metal plate. The intermediate layer and the metal ring are covered by the first metal plate and the second metal plate, wherein the second metal plate can be electrically connected to the first metal plate via the metal ring, and a resonator is formed between the first metal plate and the second metal plate. A characteristic of the flat antenna structure can be adjusted by changing the diameters of the first hole and the metal ring. In one embodiment of the invention, the intermediate layer is made of plastic instead of Teflon. 
     Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and advantages of the present invention will become apparent from the following description of the accompanying drawings, which disclose several embodiments of the present invention. It is to be understood that the drawings are to be used for purposes of illustration only, and not as a definition of the invention. 
       In the drawings, wherein similar reference numerals denote similar elements throughout the several views: 
         FIG. 1  is an exploded view of a flat antenna structure according to an embodiment of the invention. 
         FIG. 2  is an illustration of the flat antenna structure according to an embodiment of the invention. 
         FIG. 3  is a cross-section view of the flat antenna structure according to an embodiment of the invention. 
         FIG. 4  is an illustration of the deformed flat antenna structure due to the lack of a metal ring. 
         FIG. 5A  is an illustration of an electronic device having the flat antenna structure according to an embodiment of the invention. 
         FIG. 5B  is an illustration of another electronic device having the flat antenna structure according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to  FIG. 1  to  FIG. 3 .  FIG. 1  is an exploded view of a flat antenna structure according to an embodiment of the invention.  FIG. 2  is an illustration of the flat antenna structure according to an embodiment of the invention.  FIG. 3  is a cross-section view of the flat antenna structure according to an embodiment of the invention. 
     As shown in  FIG. 1  to  FIG. 3 , the flat antenna structure  1  comprises a first metal plate  20 , an intermediate layer  30 , a metal ring  40 , and a second metal plate  50 . The intermediate layer  30  has a first hole  31 , and the intermediate layer  30  is installed above and connected to the first metal plate  20 . The metal ring  40  is connected to the first metal plate  20  through the first hole  31 . The second metal plate  50  has a second hole  51 . The second metal plate  50  is connected to the metal ring  40 . The second metal plate  50  is also connected to the first metal plate  20  by riveting in order to sandwich the intermediate layer  30  and the metal ring  40  between the first metal plate  20  and the second metal plate  50 . The second metal plate  50  is electrically connected to the first metal plate  20  by riveting. The second metal plate  50  also can be electrically connected to the first metal plate  20  via the metal ring, 
     As shown in  FIG. 3 , a resonator  11  is formed between the first metal plate  20  and the second metal plate  50 . The characteristics of the flat antenna structure  1  can be adjusted by changing the diameters of the first hole  31  and the metal ring  40 . Because changing the diameter of the metal ring  40  will change the size of the resonator  11 , the antenna characteristics will change as well. 
     In one embodiment of the invention, the intermediate layer  30  is a plastic plate. The plastic material has a low dielectric constant; therefore, it can replace Teflon as the base material of the flat antenna structure  1 . As shown in  FIG. 3 , in order to fasten the flat antenna structure  1 , the first metal plate  20  is connected to the second metal plate  50  by riveting, but the invention is not limited to this connection method. In one embodiment of the invention, the intermediate layer  30  is made of high density polyethylene (HDPE), but the invention is not limited to this material. 
     As mentioned above, in addition to electrically connecting the first metal plate  20  and the second metal plate  50 , changing the diameter of the metal ring  40  can adjust the antenna characteristics of the flat antenna structure  1 . The metal ring  40  also can prevent deformation of the first metal plate  20  and the second metal plate  50  when the first metal plate  20  and the second metal plate  50  are riveted together. For example, as shown in  FIG. 4 , when riveting the first metal plate  20  and the second metal plate  50  together without the metal ring  40 , the second metal plate  50  will be deformed due to the pressure of riveting. 
     As shown in  FIG. 3 , in one embodiment of the invention, the first metal plate  20  comprises a fixing part  201  corresponding to the metal ring  40  in order to connect the first metal plate  20  and the metal ring  40  by screwing. The intermediate layer  30  is connected to the first metal plate  20  and the second metal plate  50  by adhesion. For example, the first metal plate  20 , the intermediate layer  30 , and the second metal plate  50  can be stuck together with the double-sided tape, but the invention is not limited to this method of adhesion. 
     In one embodiment of the invention, the first metal plate  20 , the second metal plate  50 , and the metal ring  40  are made of copper or copper alloys, but the invention is not limited to these materials. For example, the first metal plate  20 , the second metal plate  50 , and the metal ring  40  can also be made of silver or silver alloys. As long as the material is a metal with good conductivity, it can be used as the material of the first metal plate  20 , the second metal plate  50 , and the metal ring  40 . 
     Please refer to  FIG. 5A  and  FIG. 5B  showing electronic devices having the flat antenna structure  1  according to an embodiment of the invention. 
       FIG. 5A  is an illustration of an electronic device  7 A having the flat antenna structure  1  according to an embodiment of the invention. The electronic device  7 A comprises a main body  70 A and the flat antenna structure  1 . In one embodiment of the invention, the main body  70 A is a global positioning system (GPS), but the invention is not limited to that application. 
       FIG. 5B  is an illustration of an electronic device  7 B having the flat antenna structure  1  according to an embodiment of the invention. The electronic device  7 B comprises a main body  70 B and the flat antenna structure  1 . In one embodiment of the invention, the main body  70 B is a satellite radio, but the invention is not limited to this application. 
     Although the present invention has been explained in relation to its preferred embodiments, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.