Abstract:
The present invention provides a broadband antenna that is used in wireless communication systems. The broadband antenna includes a closed looped radiating element having a body section and a hollow section formed by closed compassing by the body section; a grounding element; and a connecting element having a first end electrically connected to the closed looped radiating element and a second end electrically connected to the grounding element. The antenna of the present invention can provide a wider frequency bandwidth and better 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 frequency 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 radiation.  
         [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 narrow frequency bandwidth of about 70 MHz at a low frequency range (900 MHz), and a narrow 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 low as 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 frequency 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. As shown in  FIG. 1 , the antenna  90  has a radiating element  91 , a connecting element  92  and a grounding element  93 . The connecting element  92  has a first end  921  and a second end  922 , wherein the first end  921  is coupled to the radiating element  91 , and the second end  922  is coupled to the grounding element  93 . 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 frequencies 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.  
         [0010]     The broadband antenna of the present invention has a closed looped structure and comprises: a closed looped radiating element, a grounding element and a connecting element. The closed looped radiating element has a body section and a hollow section formed by closed compassing by the body section. The connecting element has a first end electrically connected to the closed looped radiating element and a second end electrically connected to the grounding element.  
         [0011]     In one embodiment of the present invention, the first end of the connecting element is substantially perpendicular to a surface where the grounding element is located, or is substantially parallel to the surface where the grounding element is located.  
         [0012]     In one embodiment of the present invention, the closed looped radiating element can have one hollow section or a plurality of hollow sections; and the closed looped radiating element can be composed by a flat board or a pillar.  
         [0013]     In one embodiment of the present invention, the body section and the hollow section of the closed looped radiating element can be triangular, rectangular or any other shapes.  
         [0014]     Furthermore, the present invention also provides a broadband antenna having a radiating element, a grounding element and a closed looped connecting element. The connecting element has a first end electrically connected to the radiating element and a second end electrically connected to the grounding element, and the first end is a closed looped structure having a body section and a hollow section formed by closed compassing by the body section.  
         [0015]     In one embodiment of the present invention, the closed looped connecting element can have one hollow section or a plurality of hollow sections, and the body section and the hollow section can be triangular, rectangular or any other shapes.  
         [0016]     Moreover, the present invention also provides an electronic device having the above-mentioned broadband antenna such as a notebook computer, a mobile phone or a PDA. Furthermore, in one embodiment of the present invention, the broadband antenna can be placed at different positions according to the layout design of the electronic device.  
         [0017]     When the VSWR is less than 3, the broadband antenna according to the present invention has a frequency bandwidth of about 200 MHz at the low frequency range (900 MHz) and a frequency bandwidth at the high frequency range (1800 MHz) of about 500 MHz, and its antenna efficiency is better than the prior art technology.  
         [0018]     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  
       [0019]      FIG. 1  is a schematic drawing of a prior art broadband antenna.  
         [0020]      FIG. 2  is a schematic drawing of a broadband antenna according to a first embodiment of the present invention.  
         [0021]      FIG. 3  shows different frequency bandwidths of different antennas.  
         [0022]      FIG. 4  is a schematic drawing of a broadband antenna according to a second embodiment of the present invention.  
         [0023]      FIG. 5  is a schematic drawing of a broadband antenna according to a third embodiment of the present invention.  
         [0024]      FIG. 6A  is a schematic drawing of a broadband antenna according to a fourth embodiment of the present invention.  
         [0025]      FIG. 6B  is a schematic drawing of a broadband antenna according to a fifth embodiment of the present invention.  
         [0026]      FIG. 7  is a schematic drawing of a broadband antenna according to a sixth embodiment of the present invention.  
         [0027]      FIG. 8  is a schematic drawing of a broadband antenna according to a seventh embodiment of the present invention.  
         [0028]      FIG. 9  is a schematic drawing of a broadband antenna according to an eighth embodiment of the present invention.  
         [0029]      FIG. 10A  is a schematic drawing of a notebook computer with the broadband antenna according to the present invention.  
         [0030]      FIG. 10B  is a schematic drawing of a mobile phone with the broadband antenna according to the present invention.  
         [0031]      FIG. 10C  is a schematic drawing of a PDA with the broadband antenna according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     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 closed looped radiating element  11 , a connecting element  12 , and a grounding element  13 .  
         [0033]     The connecting element  12  has a first end  121  and a second end  122 . The first end  121  is electrically connected to the closed looped radiating element  11 , and the second end  122  is electrically connected to the grounding element  13 . The broadband antenna  100  of the present invention is electrically connected to a radio receiving/transmitting device (not shown) so that the closed looped radiating element  11  can receive or transmit electromagnetic wave. Since the connecting element  12 , the grounding element  13  and the radio receiving/transmitting device are very well known technology, they require no further description.  
         [0034]     As shown in  FIG. 2 , the main difference between the broadband antenna  100  and the prior art antenna  90  is that the radiating element  91  (as shown in  FIG. 1 ) of the antenna  90  is replaced by the closed looped radiating element  11 .  
         [0035]     As shown in  FIG. 2 , the closed looped radiating element  11  is formed by a conductive plate, which has a body section  111  and a hollow section  112  formed by closed compassing by the body section  111 . In the drawing, the body section  111  and the hollow section  112  are substantially rectangular, but this should not be construed as a limitation. The body section  111  and the hollow section  112  can also be triangular, pentagonal or other shapes.  
         [0036]     Compared to the prior art, the broadband antenna  100  has not only a dual band response, but also has a wider frequency bandwidth. Please refer to  FIG. 3 .  FIG. 3  shows the frequency response of a typical mobile phone antenna, the prior art antenna  90 , and the broadband antenna  100  of the present invention with respect to the VSWR.  
         [0037]     In  FIG. 3 , when the VSWR is less than 3, the typical mobile phone has the most narrow frequency bandwidth; its frequency bandwidth at the low frequency range (900 MHz) is about 10 MHz, and the frequency bandwidth at the high frequency range (1800 MHz) is about 100 MHz. The prior art antenna  90  has a wider frequency bandwidth, with a frequency bandwidth at the low frequency range (900 MHz) of about 120 MHz, and a frequency bandwidth at 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 at the low frequency range (900 MHz) of about 200 MHz, and a frequency bandwidth at the high frequency range (1800 MHz) of about 500 MHz. It is clear that the broadband antenna  100  of the present invention has a wider frequency bandwidth, and a higher efficiency, than the typical mobile phone and the prior art antenna  90 .  
         [0038]     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  FIG. 4 , the main difference between the broadband antenna  200  of the second embodiment of the present invention and the broadband antenna  100  of the first embodiment is that the first end  121  of the connecting element  12  of the broadband antenna  200  is substantially perpendicular to a surface where the grounding element  13  is located to reduce space. Additionally, according to the second embodiment, the angle between the first end  121  of the connecting element  12  and the grounding element  13  can angle other than 90°, such as 80° or 70°.  
         [0039]     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  FIG. 5 , the main difference between the broadband antenna  300  of the third embodiment and the broadband antenna  100  of the first embodiment is that the body section  111  of the broadband antenna  300  forms two closed hollow sections  113  and  114 . In this manner, the broadband antenna  300  still provides a wide bandwidth, dual band response. Moreover, the number of the hollow sections is not limited to two, that is, more than two hollow sections can be provided, such as three or four.  
         [0040]     Please refer to  FIG. 6A  and  FIG. 6B .  FIG. 6A  is a schematic drawing of a broadband antenna according to a fourth embodiment of the present invention.  FIG. 6B  is a schematic drawing of a broadband antenna according to a fifth embodiment of the present invention. As shown in  FIG. 6A  and  FIG. 6B , the main difference between the broadband antennas of the fourth and fifth embodiment of the present invention and the prior art antenna  90  is that the first end  921  of the connecting element  92  of the prior art antenna  90  (as shown in  FIG. 1 ) is replaced by a first end  721  having a closed looped structure. As shown in  FIG. 6A  and  FIG. 6B , each broadband antenna  400  and  500  has a radiating element  71 , a connecting element  72  and a grounding element  73 . The connecting element  72  has a first end  721  and a second end  722 . The first end  721  is electrically connected to the radiating element  71 , and the second end  722  is electrically connected to the grounding element  73 . The first end  721  has a closed looped structure and contains a body section  723  and a hollow section  725  formed by closed compassing by the body section  723 .  
         [0041]     In  FIG. 6A  and  FIG. 6B , the body section  723  and the hollow section  725  are substantially rectangular, but this should not be construed as a limitation. The body section  723  and the hollow section  725  can also be triangular, pentagonal or other shapes.  
         [0042]     Please refer to  FIG. 7 .  FIG. 7  is a schematic drawing of a broadband antenna according to a sixth embodiment of the present invention. As shown in  FIG. 7 , in the sixth embodiment, the closed looped radiating element  11  formed by the conductive plate is replaced by a closed looped radiating element  61  formed by a conductive pillar. The closed looped radiating element  61  is a rectangular pillar and has four surfaces which form a body section  611  and a closed hollow section  612 . The closed looped radiating element  61  can further improve the frequency bandwidth response and antenna efficiency of the broadband antenna  600 .  
         [0043]     As shown in  FIG. 7 , in the broadband antenna  600 , the first end  121  of the connecting element  12  is substantially parallel to the surface where the grounding element  13  is located, and a center axis of the closed looped radiating element  61  is also substantially parallel to the surface where the grounding element  13  is located, but this should not be construed as a limitation. For example, as shown in  FIG. 8 , in a broadband antenna  700  of a seventh embodiment, the first end  121  of the connecting element  12  is substantially perpendicular to the surface where the grounding element  13  is located, and a center axis of the closed looped radiating element  61  is also substantially perpendicular to the surface where the grounding element  13  is located.  
         [0044]     As shown in  FIG. 7 , the closed looped radiating element  61  is a rectangular pillar and has four surfaces that form the body section  611  and the closed hollow section  612 . However, the closed looped radiating element  61  in the present invention can be replaced by other closed looped radiating elements that have different shapes and can still achieve the same goal thereby. For example, as shown in  FIG. 9 , in a broadband antenna  800  of an eighth embodiment, the closed looped radiating element  61  with the rectangular pillar shape can be replaced by a closed looped radiating element  81  with a triangular pillar shape, wherein the closed looped radiating element  81  has three surfaces that form a body section  811  and a closed hollow section  812 .  
         [0045]     The present invention also provides an electronic device having the above-mentioned broadband antennas  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700  or  800 , which can receive and transmit radio signals via the broadband antenna. For example, as shown in  FIG. 10A  to  FIG. 10C , a notebook computer  2 , a mobile phone  3  and a PDA  4  all have the broadband antenna according to the present invention for receiving and transmitting radio signals.  
         [0046]     It should be noted that the broadband antenna  100 , or other broadband antennas  200 ,  300 ,  400 ,  500 ,  600 ,  700  or  800 , can be mounted at positions different from the ones shown in  FIG. 10A  to  FIG. 10C  according to the layout design of the notebook computer  2 , the mobile phone  3  and the PDA  4 .  
         [0047]     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.