Patent Publication Number: US-8994595-B2

Title: Multi-frequency antenna

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The application claims the benefit of Taiwan Patent Application No. 100123960, filed on Jul. 6, 2011, at the Taiwan Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a mini multi-frequency antenna, especially to an antenna able to work in a WiFi local area network (LAN) at the frequency of 2.4˜2.5 GHz. 
     BACKGROUND OF THE INVENTION 
     As the wireless communication technologies become mature, plenty of new information products have been developed. Various wireless communication networks have become ones of the most important routes by the public to exchange voices, text messages, data, information, video files, etc. Transmitting and receiving these electronic data, information or files carried by an electromagnetic wave in the wireless communication necessitate the antenna. 
     Therefore, the antenna is one of the most important components to affect the quality of the communication. Broadly reviewing all the products and technologies of the mobile communication up to now, no matter how advanced the technologies, what integrations of components and modules and what changes to the industrial designs, the design of the antenna is still one of the most important key technologies. The antenna designs with excellent performances can effectively raise the quality of the communication. A single antenna with good antenna design should be able to cover various frequency bands required in various wireless communication networks. In addition, for the availability to the portable wireless communication devices, e.g. cellular phones, personal digital assistants, etc., carried by the users, the antennas with mini sizes should be realized. 
     As shown in  FIG. 1 , a planar inverted-F antenna (PIFA) in the prior art is used for the wireless communication network. However, when this kind of antenna is used for as a multi-frequency antenna, its planar radiation portion occupy a large area, and the distance between the radiation plane and the substrate surface is related to the frequency and bandwidth of the antenna and can not be arbitrarily adjusted. 
     This kind of antenna requires large power to accomplish the transmission function and large space as well, and accordingly the volume occupied by this kind of antenna in the prior art can not be effectively reduced. 
     SUMMARY OF THE INVENTION 
     For solving the issue that the volume occupied by the antenna in the prior can not be effective reduced, the present invention provides an excellent antenna with effectively reduced volume and the ability to work as a single mini-sized multi-frequency antenna at various frequency bands in the various wireless communication networks. 
     In accordance with one aspect of the present invention, an antenna for receiving and transmitting a signal is provided. The antenna includes a connection portion receiving and transmitting the signal, a first radiation portion and a second radiation portion. The connection portion includes a first end, a second end and a third end, wherein the first end is configured at a first distance from a ground. The first radiation portion is connected to the second end, and includes at least a folding area forming thereon at least a folding segment, wherein the folding segment and the connection portion have therebetween a shortest distance being a second distance. The second radiation portion is connected to the third end. 
     In accordance with another aspect of the present invention, an antenna for receiving and transmitting a signal is provided. The antenna comprises a signal feeding portion receiving and transmitting the signal, and a first frequency adjusting portion connected to the signal feeding portion. The first frequency adjusting portion includes a first extending portion and a second extending portion extended from the first extending portion and pointing toward the signal feeding portion. 
     In accordance with a further aspect of the present invention, an antenna for receiving and transmitting a signal is provided. The antenna comprises a signal feeding portion and a coupled portion. The signal feeding portion receives and transmits the signal, and includes a feeding end having a first climax. The coupled portion includes a bottom end having a second climax for being coupled to an electronic communication device, wherein the first and the second climaxes have therebetween a distance being one of distances equal to and larger than 1 mm. 
     The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed descriptions and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is the schematic diagram showing a planar inverted-F antenna for the wireless communication network in the prior art; 
         FIG. 2  is the schematic diagram showing an antenna in accordance with some embodiments of the present invention; 
         FIG. 3  is the schematic diagram showing frequency characteristics of an antenna able to generate specific stationery waves at frequencies of 2.4 and 2.5 GHz in accordance with some embodiments of the present invention; 
         FIG. 4  is the schematic diagram showing an antenna installed in a circuit board in accordance with some embodiments of the present invention; 
         FIG. 5A-5C  are the schematic diagrams showing radiation patterns in an X-Y plane, a Y-Z plane and an X-Z plane for a multi-frequency planar antenna at the frequencies of 2.4-2.5 GHz in accordance with the first embodiment of the present invention; and 
         FIG. 6  is the schematic diagram showing another antenna in accordance with some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purposes of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
     First Embodiment 
     Before the manufacture of antennas, the required specifications, e.g. available communication frequency bands, pattern directions, gain, expected size of the antenna, etc., must be ascertained first to determine the antenna structure conforming to these required specification, and to select an appropriate feeding method. Then, the shape, size and other parameters of the antenna are primarily designed. 
     Although the conventional PIFA has advantages of low configuration, simple manufacturing processes and availability of operation at multi frequencies, the conventional PIFA has a drawback that the bandwidth is too narrow. For enlarging the bandwidth, the present invention develops a new design of the antenna in view of the distance between the PIFA metal plane and ground, and the distance between the feeding point and the radiation portion of the PIFA for minimizing the size of the antenna. 
       FIG. 2  shows an antenna of the present invention. As shown in  FIG. 2 , the antenna  2  can be a unipolar antenna formed by the inclusion of a conductive plane with uniform cross sectional thickness and three portions after folding. The antenna  2  has a connection portion  21 , a first radiation portion  22  and a second radiation portion  23 . A feeding point CP is configured in a lower edge of the connection portion  21  for receiving and transmitting a signal. The connection portion  21  has a first end  210  configured at a first distance D 1 , preferably equal to or larger than 1 mm, from the ground. The first radiation portion  22  is connected to the second end  211  of the connection portion  21 . The first radiation portion  22  includes at least one folding area  220  to form at least one folding segment  221 . There is the shortest distance, as a second distance D 2  preferably equal to or larger than 1 mm, between the folding segment  221  and the connection portion  21 . The second radiation portion  23  is connected to the third end  212  of the connection portion  21 . The second radiation portion  23  includes at least one folding area  231  to form at least one folding segment  232 , which is parallel to the connection portion  21 . 
     The folding structures of these radiation portions are described in detail as follows. The folding angle of the folding area  220  of the first radiation portion  22  is a right angle, i.e. 90 degree, and so is that of folding area  231  of the second radiation portion  23 . 
     Through the structure of the antenna  2 , the path length from the feeding point CP of the connection portion  21  to the segment end of the folding segment  221  of the first radiation portion  22 , i.e. the dash line denoted as the path  1 A in  FIG. 2 , forms a resonance structure of a unipolar antenna, where the path length of the path  1 A is designed to be equal to one fourth of the wavelength corresponding the frequency of 2.4 GHz so as to generate the stationery wave at the frequency of 2.4 GHz. Consequently, the antenna of the present embodiment is able to work at dual frequency bands of 2.4 and 2.5 GHz. 
       FIG. 3  shows frequency characteristics of an antenna able to generate specific stationery waves at frequencies of both 2.4 and 2.5 GHz in accordance with some embodiments of the present invention. The abscissa of  FIG. 3  represents frequency; while the ordinate thereof represents the magnitude of the frequency domain characteristics. For instance, the ordinate of  FIG. 3  can be a voltage standing wave ratio (VSWR). As understood by the skilled person in the art, a local minimum of the voltage standing wave ratio in the frequency domain can stand for an available frequency band of the antenna, especially from the view of the radiation of the frequency domain. 
     Due to the minimized size and the availability of large bandwidth, the antennas of the present invention can be widely applied to various portable communication devices, e.g. cellular phones, personal digital assistants (PDAs), lap top computers, etc.  FIG. 4  shows an antenna  2  installed in a circuit board P in accordance with some embodiments of the present invention. As referring to  FIGS. 2 and 4  together, the lower edge of the second radiation portion  23  of the antenna  2  is configured with a hook  24 , which is to be embedded into the circuit board P for installing the antenna  2  onto the circuit board P. 
     In addition, since the radio wave encounters different impedances when transmitting along the different sections of the antenna system, e.g. radio station, feeding line, antenna, free space, etc., a ground end  25  is designed as disposed between the folding segment  232  of the second radiation portion  23  and the hook  24  located at the lower edge of the second radiation portion  23  for matching the impedances. 
     Besides,  FIGS. 5A-5C  show the radiation patterns in an X-Y plane, a Y-Z plane and an X-Z plane of a multi-frequency planar antenna at the frequencies of 2.4-2.5 GHz in accordance with the first embodiments of the present invention, respectively. As shown in the radiation patterns in  FIGS. 5A-5C , the antenna provides omnidirectional radiation. 
     Second Embodiment 
       FIG. 6  shows an antenna in accordance with some embodiments of the present invention. As shown in  FIG. 6 , the antenna  6  includes a signal feeding portion  61  similar to the connection portion  21  in  FIG. 2 . The signal feeding portion  61  includes a first climax  610 , i.e. feeding point CP, for receiving and transmitting a signal. The antenna  6  in  FIG. 6  includes a first frequency adjusting portion  62  similar to the first radiation portion  22  in  FIG. 2 . The first frequency adjusting portion  62  is connected to the signal feeding portion  61  and includes a first extending portion  621  and a second extending portion  622 . The first extending portion  621  is defined as the portion from the second end  611  of the signal feeding portion  61  to the folding area  620  of the first frequency adjusting portion  61 . The second extending portion  622  is extended from the first extending portion  621  at the folding area  620  and points toward the signal feeding portion  61 . There is a shortest distance as a first distance D 1 , equal to or smaller than 1 mm, between the second extending portion  622  and the signal feeding portion  61 . The antenna  6  in  FIG. 6  includes a coupled portion  63  similar to the second radiation portion  23  in  FIG. 2 . The coupled portion  63  can be coupled to an electronic communication device, and includes bottom end  631  having a second climax  632 . The first climax  610  and the second climax  632  have therebetween a second distance D 2  equal to or smaller than 1 mm. 
     Some embodied examples of the present invention are described in the following. 
     1. An antenna for receiving and transmitting a signal is provided. The antenna comprises a connection portion receiving and transmitting the signal, a first radiation portion and a second radiation portion. The connection portion includes a first end, a second end and a third end, wherein the first end is configured at a first distance from a ground. The first radiation portion is connected to the second end, and includes at least a folding area forming thereon at least a folding segment, wherein the folding segment and the connection portion have therebetween a shortest distance being a second distance. The second radiation portion is connected to the third end. 
     2. In an antenna according to Example 1, each of the folding areas of the first radiation portion and the second radiation portion has a folding angle equal to a right angle. 
     3. In an antenna according to any one of the above examples, the second radiation portion includes at least a folding area having at least a folding segment parallel to the connection portion, and the second radiation portion has a lower edge configured with a hook to be embedded into a circuit board for installing the antenna onto the circuit board. 
     4. An antenna according to any one of the above examples further comprises a ground end disposed between the folding area of the second radiation portion and the hook for matching an impedance. 
     5. An antenna according to any one of the above examples has a path and an operating frequency corresponding to an operating wavelength, wherein the folding segment of the first radiation portion has a segment end, and the path between the first end and the segment end of the folding segment of the first radiation portion has a path length equal to one-fourth of the operating wavelength. 
     6. In an antenna according to any one of the above examples, each of the first and the second distances is one of distances equal to and larger than 1 mm. 
     7. In an antenna according to any one of the above examples, the connection portion, the first radiation portion and the second radiation portion are made in one piece. 
     8. In an antenna according to any one of the above examples, the antenna has an operating bandwidth in a range of 2.4 to 2.5 GHz. 
     9. An antenna for receiving and transmitting a signal is provided. The antenna comprises a signal feeding portion receiving and transmitting the signal and a first frequency adjusting portion. The first frequency adjusting portion is connected to the signal feeding portion, and includes a first extending portion and a second extending portion extended from the first extending portion and pointing toward the signal feeding portion. 
     10. An antenna according to any one of the above examples further comprises a second frequency adjusting portion coupled to an electronic communication device, connected to the signal feeding portion, and including a bottom end having a second climax, wherein the signal feeding portion has a first climax, and the first and the second climaxes have therebetween a distance being one of distances equal to and larger than 1 mm. 
     11. In an antenna according to any one of the above examples, the first and the second extending portions have an included angle equal to a right angle, and the second frequency adjusting portion includes at least a folding area having a folding angle equal to the right angle. 
     12. In an antenna according to any one of the above examples, the second frequency adjusting portion has a lower edge configured with a hook to be embedded into a circuit board for installing the antenna onto the circuit board, and the antenna further comprises a ground end disposed between the folding area of the second frequency adjusting portion and the hook for matching an impedance. 
     13. In an antenna according to Claim  10 , the signal feeding portion, the first frequency adjusting portion and the second frequency adjusting portion are made in one piece, and the antenna has an operating bandwidth in a range of 2.4 to 2.5 GHz. 
     14. An antenna according to any one of the above examples has a path and an operating frequency corresponding to an operating wavelength, wherein the signal feeding portion has a first end configured at a first distance from a ground, the second extending portion has an extending end, the path is formed from the first end to the extending end and has a path length equal to one-fourth of the operating wavelength, the signal feeding portion and the second extending portion have therebetween a shortest distance being a second distance, and each of the first and the second distances is one of distances equal to and larger than 1 mm. 
     15. An antenna for receiving and transmitting a signal is provided. The antenna comprises a signal feeding portion and a coupled portion. The signal feeding portion receives and transmits the signal, and includes a feeding end having a first climax. The coupled portion includes a bottom end has a second climax for being coupled to an electronic communication device, wherein the first and the second climaxes have therebetween a distance being one of distances equal to and larger than 1 mm. 
     16. An antenna according to any one of the above examples further comprises a frequency adjusting portion connected to the signal feeding portion and including a first extending portion and a second extending portion extended from the first extending portion and pointing toward the signal feeding portion. 
     17. In an antenna according to any one of the above examples, the first and the second extending portions have an included angle equal to a right angle, and the coupled portion includes at least a folding area having a folding angle equal to the right angle. 
     18. In an antenna according to any one of the above examples, the coupled portion has a lower edge configured with a hook to be embedded into a circuit board for installing the antenna onto the circuit board, and the antenna further comprises a ground end disposed between the folding area of the coupled portion and the hook for matching an impedance. 
     19. In an antenna according to any one of the above examples, the signal feeding portion, the coupled portion and the frequency adjusting portion are made in one piece, and the antenna has an operating bandwidth in a range of 2.4 to 2.5 GHz. 
     20. An antenna according to any one of the above examples has a path and an operating frequency corresponding to an operating wavelength, wherein the signal feeding portion has a first end configured at a first distance from a ground, the second extending portion has an extending end, the path is formed from the first end to the extending end and has a path length equal to one-fourth of the operating wavelength, the signal feeding portion and the second extending portion have therebetween a shortest distance being a second distance, and each of the first and the second distances is one of distances equal to and larger than 1 mm. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.