Abstract:
A broadband antenna for wireless communication system, the broadband antenna includes a radiating element, a grounding element and a connecting element for connecting the radiating element and the grounding element. The radiating element has a U-shaped structure, a V-shaped structure or an L-shaped structure. The broadband antenna of the present invention has wider frequency bandwidth and higher antenna efficiency.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an antenna, and more particularly, to a dual-band broadband antenna.  
         [0003]     2. Description of the Related Art  
         [0004]     With the developments in wireless communications technology, many electronic devices, such as notebooks and mobile phones, now incorporate wireless communications abilities. In order to receive and transmit signals, these electronic devices need to have an antenna for detecting electromagnetic wave.  
         [0005]     Since both mobile phones and notebooks have became important in the daily lives of many people, if it were possible to combine these two devices, such a combined-function device would offer significantly more convenience for users. However, the prior art antennas for typical mobile phones usually have a frequency bandwidth of about 70 MHz at a low frequency range (900 MHz), and a frequency bandwidth of about 120 MHz at a high frequency range (1800 MHz) when a VSWR (Voltage Standing Wave Ratio) is less than 4. Additionally, the antenna efficiency of the typical mobile phones is typically around 20-30%; therefore, if the prior art mobile phone antenna is installed in a notebook, the antenna will not provide very satisfactory results.  
         [0006]     A prior art technology has disclosed a dual-band antenna that can provide a wider frequency bandwidth than earlier mobile phone antennas. Please refer to  FIG. 1 .  FIG. 1  shows a prior art antenna  90 , as disclosed in U.S. Pat. No. 6,861,986. The antenna  90  can be used for WWAN, WLAN 802.11a or 802.11b, Bluetooth or GSM communications systems. Compared to the typical mobile phone antenna, the antenna  90  has a wider frequency bandwidth, usually having a frequency bandwidth of about 120 MHz at the low frequency range (900 MHz) and a frequency bandwidth of about 480 MHz at the high frequency range (1800 MHz) when the VSWR is less than 3.  
         [0007]     Although the prior art technology already provides a broadband antenna, the frequency bandwidth still can be improved. Furthermore, if a new antenna can provide a wider frequency bandwidth with a smaller size, such a new antenna would have better platform compatibility characteristics, and would have lower manufacturing costs.  
         [0008]     Therefore, it is desirable to provide a dual-band broadband antenna to mitigate and/or obviate the aforementioned problems.  
       SUMMARY OF THE INVENTION  
       [0009]     An objective of the present invention is to provide a broadband antenna with wider frequency bandwidth. The broadband antenna with a U-shaped structure of the present invention has a radiating element with a U-shaped structure, a grounding element and a connecting element. The radiating element has a first metal plane, a second metal plane and a third metal plane to form the U-shaped structure. When the VSWR is less than 3, this broadband antenna with the U-shaped structure has a frequency bandwidth of about 300 MHz at a low frequency range (900 MHz), a frequency bandwidth of about 550 MHz at a high frequency range (1800 MHz), and its antenna efficiency is about 40˜50%.  
         [0010]     The present invention also provides a broadband antenna with a V-shaped structure. The broadband antenna with the V-shaped structure of the present invention has a radiating element with a V-shaped structure, a grounding element and a connecting element. The radiating element has a first metal plane and a second metal plane to form the V-shaped structure.  
         [0011]     The present invention also provides a broadband antenna with an L-shaped structure. The broadband antenna with the L-shaped structure of the present invention has a radiating element with an L-shaped structure, a grounding element and a connecting element. The radiating element has a first metal plane and a second metal plane to form the L-shaped structure.  
         [0012]     The above-mentioned broadband antenna with the V-shaped structure and the broadband antenna with the L-shaped structure both can provide wider frequency bandwidth.  
         [0013]     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a schematic drawing of a prior art broadband antenna.  
         [0015]      FIG. 2  is a schematic drawing of a broadband antenna according to a first embodiment of the present invention.  
         [0016]      FIG. 3  shows different frequency bandwidths of different antennas.  
         [0017]      FIG. 4  is a schematic drawing of a broadband antenna according to a second embodiment of the present invention.  
         [0018]      FIG. 5  is a schematic drawing of a broadband antenna according to a third embodiment of the present invention.  
         [0019]      FIG. 6  is a schematic drawing of a broadband antenna according to a fourth embodiment of the present invention.  
         [0020]      FIG. 7  is a schematic drawing of a broadband antenna according to a fifth embodiment of the present invention.  
         [0021]      FIG. 8  is a schematic drawing of a broadband antenna according to a sixth embodiment of the present invention.  
         [0022]      FIG. 9  is a schematic drawing of a broadband antenna according to a seventh embodiment of the present invention.  
         [0023]      FIG. 10  is a schematic drawing of a broadband antenna according to an eighth embodiment of the present invention.  
         [0024]      FIG. 11  is a schematic drawing of a broadband antenna according to a ninth embodiment of the present invention.  
         [0025]      FIG. 12  is a schematic drawing of a broadband antenna according to a tenth embodiment of the present invention.  
         [0026]      FIG. 13  is a schematic drawing of a broadband antenna according to an eleventh embodiment of the present invention.  
         [0027]      FIG. 14  is a schematic drawing of a broadband antenna according to a twelfth embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     Please refer to  FIG. 2 .  FIG. 2  is a schematic drawing of a broadband antenna according to a first embodiment of the present invention. As shown in the drawing, in the first embodiment, the broadband antenna  100  comprises a radiating element  11 , a connecting element  12 , a grounding element  13 , a feed line  14  and a PCB (printed circuit board)  15 .  
         [0029]     The connecting element  12  has a first end  121  and a second end  122 . The first end  121  is electrically connected between the two ends of the radiating element  11 , which has a U-shaped structure, and the second end  122  is electrically connected to grounding element  13 . The connecting element  12  and the grounding element  13  are both mounted on the PCB  15 . One end of the feed line  14  is electrically connected to the first end  121  of the connecting element  12  and the other end of the feed line  14  is electrically connected to a radio receiving/transmitting device (not shown) to electrically connect the radiating element  11  to the radio receiving/transmitting device, and to use the radiating element  11  to receive or transmit electromagnetic wave. Since the connecting element  12 , the grounding element  13 , the feed line  14  and the PCB  15  are all very well-known elements, they require no further description.  
         [0030]     As shown in  FIG. 2 , one main difference between the broadband antenna  100  of the present invention and the prior art antenna  90  is the replacement of the radiating element  91 , which has a straight line-shaped structure (as shown in  FIG. 1 ), by the radiating element  11  that has a U-shaped structure.  
         [0031]     As shown in  FIG. 2 , the radiating element  11  comprises a quadrilateral first metal plane  111 , a second metal plane  112  and a third metal plane  113 . The first metal plane  111  and the second metal plane  112  are connected to each other, and the second metal plane  112  and the third metal plane  113  are also connected to each other to form a U-shaped structure. The first metal plane  11   1  and the third metal plane  113  are parallel with the surface that the grounding element  13  and the PCB  15  are positioned onto; the second metal plane  112  is perpendicular with the surface that the grounding element  13  and the PCB  15  are positioned onto, and so an opening of the U-shaped structure of the radiating element  11  is parallel with the grounding element  13  and the PCB  15 .  
         [0032]     Compared to the prior art, the broadband antenna  100  has not only a dual-band but also a wider frequency bandwidth. Please refer to  FIG. 3 .  FIG. 3  shows the frequency response of a typical mobile phone, the prior art antenna  90 , and the broadband antenna  100  of the present invention with respect to the VSWR.  
         [0033]     In  FIG. 3 , when the VSWR is less than  3 , the typical mobile phone has the most narrow frequency bandwidth; its frequency bandwidth in the low frequency range (900 MHz) is about 10 MHz, and the frequency bandwidth in the high frequency range (1800 MHz) is about 100 MHz. The prior art antenna  90  has a wider frequency bandwidth, with a frequency bandwidth in the low frequency range (900 MHz) of about 120 MHz, and a frequency bandwidth in the high frequency range (1800 MHz) of about 480 MHz. The broadband antenna  100  of the present invention has the widest frequency bandwidth, with a frequency bandwidth in the low frequency range (900 MHz) of about 300 MHz, and a frequency bandwidth in the high frequency range (1800 MHz) of about 550 MHz. It is clear that the broadband antenna  100  of the present invention has a wider frequency bandwidth, and a better efficiency, than the typical mobile phone and the prior art antenna  90 .  
         [0034]     Please refer to  FIG. 4 .  FIG. 4  is a schematic drawing of a broadband antenna according to a second embodiment of the present invention. As shown in the drawing, the main difference between the broadband antenna  200  in the second embodiment and the broadband antenna  100  in the first embodiment is that, in the second embodiment, the first metal plane  111  and the third metal plane  113  are perpendicular to the grounding element  13 , and the second metal plane  112  is parallel with the grounding element  13  so that the opening of the U-shaped structure of the radiating element  11  faces toward the grounding element  13 .  
         [0035]     Please refer to  FIG. 5 .  FIG. 5  is a schematic drawing of a broadband antenna according to a third embodiment of the present invention. As shown in the drawing, in the third embodiment, the main difference between the broadband antenna  300  in the third embodiment and the broadband antenna  100  in the first embodiment is that, in the third embodiment, the first end  121  of the connecting element  12  is electrically connected to one side of the radiating element  11  and not between the two ends of the radiating element  11 . Therefore, the third embodiment of the present invention is capable of inducing a second resonance of 1800 MHz from 900 MHz, thus as to provide dual bands and broad bandwidth responses. Since induce dual bands technology is a well-known technology there will be no more description.  
         [0036]     Please refer to  FIG. 6 .  FIG. 6  is a schematic drawing of a broadband antenna according to a fourth embodiment of the present invention. As shown in the drawing, in the fourth embodiment, the feed line  14  in the broadband antenna  400  is directly connected to the radiating element  11  with the U-shaped structure and not to the first end  121  of the connecting element  12 , as shown in  FIG. 2 . The broadband antenna  400  in the fourth embodiment of the present invention still provides a wide bandwidth, dual frequency response.  
         [0037]     Please refer to  FIG. 7 .  FIG. 7  is a schematic drawing of a broadband antenna according to a fifth embodiment of the present invention. As shown in the drawing, the feed line  14  of the broadband antenna  500  in the fifth embodiment of the present invention is directly connected to the radiating element  11  with the U-shaped structure, and not to the first end  121  of the connecting element  12 , as shown in  FIG. 5 . In this way, the broadband antenna  500  of the fifth embodiment of the present invention still provides a wide bandwidth, dual frequency response.  
         [0038]     In the above-mentioned five embodiments, all three metal planes  111 ,  112 ,  113  of the radiating element  11  are quadrilateral, but this should not be construed as a limitation of the present invention. For example, as shown in  FIG. 8 , in a broadband antenna  600  of the sixth embodiment of the present invention, the broadband antenna  600  has a radiating element  11 ′ having a second metal plane  112  with a quadrilateral shape, a first metal plane  111 ′ and a third metal plane  113 ′ both with a pentagonal shape; or as shown in  FIG. 9 , in a broadband antenna  700  of the seventh embodiment of the present invention, the broadband antenna  700  comprises radiating element  11 ″ having a second metal plane  112 ″ with a quadrilateral shape, a first metal plane  111 ″ and a third metal plane  113 ″ both with a triangular shape. In this manner, the present invention antennas still respectively provide a wide bandwidth, dual frequency response.  
         [0039]     To reduce the size of the antenna, the radiating element  11  with the U-shaped structure can be altered to different shapes, such as a V-shaped structure or an L-shaped structure.  
         [0040]     Please refer to  FIG. 10 .  FIG. 10  is a schematic drawing of a broadband antenna according to an eighth embodiment of the present invention. As shown in  FIG. 10 , in a broadband antenna  800  of the eighth embodiment of the present invention, the radiating element  11  with the U-shaped structure in each of the first to seventh embodiments is replaced by a radiating element  81  with a V-shaped structure to reduce the size of the antenna. As shown in  FIG. 10 , the broadband antenna  800  comprises a radiating element  81  having a first metal plane  811  and a second metal plane  812  which form a V-shaped structure; and the opening of the radiating element  81 ′ of the broadband antenna  800  faces toward the grounding element  13 .  
         [0041]     Please refer to  FIG. 11 .  FIG. 11  is a schematic drawing of a broadband antenna according to a ninth embodiment of the present invention. As shown in the drawing, in a broadband antenna  900  of the ninth embodiment of the present invention, and the opening of the radiating element  81  with the V-shaped structure faces backward the grounding element  13 . In this way, the present invention can still provide a wide bandwidth, dual frequency response.  
         [0042]     Please refer to  FIG. 12 .  FIG. 12  is a schematic drawing of a broadband antenna according to a tenth embodiment of the present invention. As shown in the drawing, in a broadband antenna  1000  of the tenth embodiment of the present invention, the radiating element  11  with the U-shaped structure in the other embodiments is replaced by a radiating element  81 ′ with an L-shaped structure to reduce the size of the antenna. As shown in  FIG. 12 , the broadband antenna  1000  comprises a radiating element  81 ′ having a first metal plane  811 ′ and a second metal plane  812 ′ which form an L-shaped structure; and the opening of the radiating element  81  of the broadband antenna  1000  faces toward the grounding element  13 .  
         [0043]     Please refer to  FIG. 13 .  FIG. 13  is a schematic drawing of a broadband antenna according to an eleventh embodiment of the present invention. As shown in the drawing, in a broadband antenna  1100  of the eleventh embodiment of the present invention, the opening of the radiating element  81 ′ with the L-shaped structure faces backward the grounding element  13 . In this way, the present invention can still provide a wide bandwidth, dual frequency response.  
         [0044]     In the above-mentioned embodiments, each radiating element  11 ,  11 ′,  11 ″,  81 ,  81 ′ can either be disposed separately from or combined with the connecting element  12  as an integrated form to omit the PCB  15 . For example, as shown in  FIG. 14 , in a broadband antenna  1200  of a twelfth embodiment of the present invention, the radiating element  11  with the U-shaped structure and the connecting element  12  in the first embodiment are disposed as a single identity. Similarly, radiating elements with other shapes can also be disposed with the connecting element as a single identity (not shown). In this way, the present invention can still provide a wide bandwidth, dual frequency response.  
         [0045]     Although the present invention has been explained in relation to its preferred embodiment, 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.