Abstract:
The present invention provides an embedded antenna. It is to form meanders on a radiating element of the embedded antenna for dividing the resonant length of the radiating element into several short resonant length to extend the bandwidth of the radiating element. It is also to form meanders on the radiating element to extend the resonant length. This design can minimize the size of the embedded antenna and achieve the same as performance of a larger size antenna.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to designs for antenna structures, and more particularly to embedded antennas. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    Currently, the communication technology in a great development, many information processing systems, in particular to, laptops, personal digital assistants (PDA), cellular mobile phones and portable devices for game/entertainment, typically employs wireless communication peripherals to communicate with external world without the wired connection. 
         [0003]    A conventional personal computer or laptop must has an antenna to transmit or receive a radio frequency (RF) signal for performing wireless communication if it desires to communicate with external devices by wireless network connectivity. 
         [0004]    A wireless communication device generally includes one or more antennas which transmit or receive RF signals. The specific antennas disposed in the device may be customized to adapt various wireless communication applications. Antenna design is primarily determined by some factor, e.g. communication protocol, frequency range, data flux, distance, power level, quality of service (Qos) and other factors. 
         [0005]      FIG. 1  is a diagram illustrating a conventional laptop  10 . The laptop  10  includes a host  12  and a display  14 . An antenna  16  is mounted on the host  12  to transmit or receive RF signal. The disadvantage of this configuration is that the antenna  16  is disposed outside the host  12 , the size is huge and the antenna  16  is likely to be damage by external environment or force. 
         [0006]    In another conventional design, an antenna  18  is embedded within the housing of the laptop  10 , and covered within the laptop  10  to reduce possibility of damage. The space among the components within the laptop is very tight to achieve the purpose of minimizing its size for portability. The performance of an embedded antenna is readily interference by external environment, such as, the electromagnetic field caused by the circuit in a laptop can affect the performance. In addition, each type laptop has different configuration, and an improper configuration can affect the orientation of an embedded antenna within the laptop so that the performance will be downgrade. Moreover, each laptop with different configuration must customize antennas therein to achieve the optimum wireless connectivity performance. 
         [0007]    However, the customized antenna design may cause a high manufacture cost. The current antenna designs must allow for various applications in a different communication protocol, such as AMPS (824-894 MHz), IEEE 802.11b/g (2.4-2.5 GHz), IEEE 802.11a (4.9-5.85 GHz), and other case with specific frequency bands. Therefore, there is a need to improve the operation bandwidth and the efficiency of an antenna for accommodating various devices with different configurations and communication protocols. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention is to provide a multi-band PIFA antenna that has a specific design to extend the low and high band and to improve the performance thereof so that it can be broadly operated in various protocols and configurations 
         [0009]    In one aspect of the present invention, the antenna includes specific grooves (meanders) on a radiating element of the embedded antenna thereby dividing the resonant length of the embedded antenna into multiple resonant lengths for extend the frequency range of the embedded antenna. Additionally, a wide meander is formed on the radiating element to extend the resonant length, which reduces the size of the embedded antenna and achieves a better frequency range and performance than the conventional one with same sizes. 
         [0010]    For the aforementioned, the present invention discloses an embedded antenna, comprising: a grounding element having a first ground plane and a second ground plane; a first radiating element connected to the grounding element, operating at a first frequency band and having a fist resonant length, wherein a first meander is formed on a plane of the first radiating element, wherein the radiating element has a first plane stretched from the second grounding element; a second radiating element connected to the grounding element, operating at a second frequency band and having a second resonant length; and a feeding point connected to the first radiating element and the second radiating element. 
         [0011]    Moreover, the present invention also discloses an embedded antenna, comprising: a grounding element having a first ground plane and a second ground plane; a first radiating element connected to the grounding element, operating at a first frequency band and having a fist resonant length, wherein a meander is formed on a plane of the first radiating element, wherein the radiating element has a first plane stretched from the second grounding element; a second radiating element connected to the grounding element, operating at a second frequency band and having a second resonant length, wherein the second radiating element has a second meander thereby extending a resonant length of the second radiating element; and a feeding point connected to the first radiating element and second radiating element. 
         [0012]    These and other aspects, objects, features and advantages of the present invention will be described or become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The foregoing, features and advantage of the present invention will become fully understanding through the detailed description with the accompany drawing: 
           [0014]      FIG. 1  is a diagram illustrating a conventional embodiment of antennas configuration for a laptop. 
           [0015]      FIG. 2  is a diagram illustrating a perspective view of an embedded antenna according to the present invention. 
           [0016]      FIG. 3  is a diagram illustrating a front view of the embedded antenna according to the present invention, 
           [0017]      FIG. 4  is a diagram illustrating a perspective view of the embedded antenna according to another embodiment of present invention. 
           [0018]      FIG. 5  is a diagram illustrating a front view of the embedded antenna according to another embodiment of the present invention. 
           [0019]      FIG. 6  illustrates the measured SWR (standing wave ratio) of the embedded antenna of  FIG. 2  as a function of frequency in two frequency bands. 
           [0020]      FIG. 7  illustrates the measured SWR (standing wave ratio) of the embedded antenna of  FIG. 4  as a function of frequency in two frequency bands. 
           [0021]      FIG. 8  is graphical diagrams illustrating the measured radiation pattern of the embedded antenna of  FIG. 2  at various frequencies. 
           [0022]      FIG. 9  is graphical diagrams illustrating the measured radiation pattern of the embedded antenna of  FIG. 4  at various frequencies. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The invention will now be described in greater detail with preferred embodiments of the invention and illustrations attached. Nevertheless, it should be recognized that the preferred embodiments of the invention is only for illustrating. Besides the preferred embodiment mentioned here, present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited expect as specified in the accompanying claims. 
         [0024]      FIG. 2  illustrates a perspective view of an embedded antenna in accordance with one embodiment of the present invention. The embedded antenna of the present invention is a planar inverted F antenna (PIFA) that has a specific design to extend the low and high band for improving the performance of the antenna so that the present invention can be broadly operated in various protocols and configurations. As shown in  FIG. 2 , the embedded antenna  200  of the present invention comprises a radiating element  20 , a feeding point  21 , and a grounding element  22 . The radiating element  20  includes a first radiating element  202 , a second radiating element  204 , wherein the two elements may be operated at a different frequency band respectively. The radiating element  20  may emit radiation when current is fed into the embedded antenna  200  through the feeding point  21 . The grounding element  22  includes a first grounding plane  222  and a second grounding plane  224 , wherein the first grounding plane  222  is orthogonal to the second grounding plane as shown in  FIG. 2 . 
         [0025]    Referring to  FIG. 2  and  FIG. 3 , the grounding element  22  extends upwardly to electrically connect with the radiating element  20 . A feeding point  21  also extends upwardly to electrically connect to the radiating element  20 . A feed line (not shown) electrically connects to the feeding point  21  for feeding current into the embedded antenna  200 . By the usage of the feeding point  21 , the current from the feed-line may cause the radiation emitted from the radiating elements, for instant, to receive or transmit the RF signal in IEEE 802.11b/g (2.4-2.5 GHz) or IEEE 802.11a (4.9-5.85 GHz). The table 1 shows the average gains at different corresponding frequencies of the embedded antenna  200 . 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Frequency (Hz) 
                 Average Gain (dBi) 
                 Peak Gain (dBi) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2400 
                 −2.79 
                 2.34 
               
               
                 2450 
                 −2.69 
                 1.57 
               
               
                 2500 
                 −3.46 
                 1.77 
               
               
                 4900 
                 −3.49 
                 1.15 
               
               
                 5150 
                 −4.23 
                 −0.28 
               
               
                 5350 
                 −2.43 
                 2.55 
               
               
                 5470 
                 −3.08 
                 1.48 
               
               
                 5650 
                 −4.40 
                 −1.03 
               
               
                 5730 
                 −3.71 
                 0.51 
               
               
                 5750 
                 −3.72 
                 0.23 
               
               
                 5830 
                 −3.81 
                 0.69 
               
               
                 5900 
                 −3.72 
                 −0.49 
               
               
                   
               
             
          
         
       
     
         [0026]    Preferably, the cross-section of the radiating element  20  shows an inverted U-shaped section having a feeding point  21  that is formed on the upper plane of the inverted U-shaped structure thereby defining or forming the first radiating element  202  and the second radiating element  204 . The first radiating element  202  stands for the high-band radiating element in the embedded antenna  200 , preferably, the frequency band is correspondent to IEEE 802.11a (4.9-5.85 GHz). Accordingly, the second radiating element  204  indicates the low-band radiating element, the band of which is corresponding to IEEE 802.11b/g (2.4-2.5 GHz). The first radiating element  202  and the second radiating element  204  have a first resonant length and a second resonant length respectively, used for determining the band at which the radiating element operates, and the second resonant length is longer than the first resonant length. 
         [0027]    The meander groove  23 , especially to be U-shaped groove, divides the high-band radiating element  202  of the radiating element  20  into two smaller areas  202 A and  202 B, therefore, the resonant length (the first resonant length) of high frequency band is divided into two smaller paths. Additionally, a meander groove  24  is formed on low-band radiating element  204 . The area  202 B is extended upwardly and perpendicular to the second grounding plane  224 . The bandwidth at which embedded antenna  200  operates in high frequency band is respectively divided into two part correspond to the areas  202 A and  202 B because the resonant length of the first radiating element  202  is divided. The bandwidths corresponding to the areas  202 A and  202 B are partially overlapped to generate wider bandwidth of the radiating element  20  compare with the bandwidth of a conventional antenna. 
         [0028]    Preferably, the physical length of the radiating element  204  (the low-band radiating element) of the radiating element  20  is extended by the meander groove  24  to achieve the purpose. When the physical length is increased, the resonant length of the radiating element  204  is increased accordingly so that the bandwidth of the low band is wider. For the foregoing, the design of the embedded antenna  200  could extend high-band and low-band bandwidths, and it has more excellent performance to accommodate with various communication protocols and configurations. Preferably, the embedded antenna of the present invention is mounted on an electronic device through the first grounding plane, wherein the electronic device includes a personal computer, a cellular telephone, a portable computer, a PDA or a similar device.  FIG. 6  illustrates the measured SWR (standing wave ratio) of the embedded antenna  200  as a function of frequency in two frequency bands. 
         [0029]    In another embodiment,  FIG. 4  illustrates a perspective view of the embedded antenna  400  according to the present invention. Referring to  FIG. 4  and  FIG. 5 , the embedded antenna  400  of the present invention comprises a radiating element  40 , a feeding point  41 , and a grounding element  42 . The radiating element  40  includes a first radiating element  202 , a second radiating element  204 , wherein the two elements have a different frequency band respectively. The first radiating element  402  stands for the high-band radiating element in the embedded antenna  400 , preferably, the band is corresponding to IEEE 802.11a (4.9-5.85 GHz). Accordingly, the second radiating element  404  stands for the low-band radiating element the band of which corresponding IEEE 802.11b/g (2.4-2.5 GHz). When current is fed into the embedded antenna  400  through the feeding point  41 , the radiating element  40  may emit radiation due to the EM oscillation. As aforementioned, the first grounding plane  422  is orthogonal with the second grounding plane  424 . 
         [0030]    The structure of the embedded antenna  400  is similar to the structure of the embedded antenna  200 , therefore, the similar portion, such as the description of meander groove  44  is omitted. Table 2 shows the average gains at different frequencies. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Frequency (Hz) 
                 Average Gain (dBi) 
                 Peak Gain (dBi) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2400 
                 −4.65 
                 0.35 
               
               
                 2450 
                 −4.50 
                 −0.33 
               
               
                 2500 
                 −4.98 
                 −0.84 
               
               
                 4900 
                 −4.34 
                 −0.23 
               
               
                 5150 
                 −4.18 
                 1.00 
               
               
                 5350 
                 −4.02 
                 0.57 
               
               
                 5470 
                 −3.82 
                 0.06 
               
               
                 5650 
                 −4.18 
                 0.29 
               
               
                 5730 
                 −4.00 
                 −0.06 
               
               
                 5750 
                 −3.98 
                 −0.29 
               
               
                 5830 
                 −4.30 
                 −0.41 
               
               
                 5900 
                 −5.31 
                 −1.11 
               
               
                   
               
             
          
         
       
     
         [0031]    Preferably, a meander groove  43 , especially to be U-shaped groove, which extends the resonant length of the high-band/low-band radiating element of radiating element  40  is formed at the first/second radiating element  402 / 404 . This decreases the size of the embedded antenna  400  and achieves a broader bandwidth at low band. 
         [0032]    For the above-mentioned, the embedded antenna  400  of the present invention broadens the bandwidths of the high band and the low band, which has more excellent performance and smaller size to accommodate with various communication protocols and configurations. 
         [0033]      FIG. 7  illustrates the measured SWR (standing wave ratio) of the embedded antenna  400  as a function of frequency at two frequency bands. Thus, the embedded antenna has good performance than the conventional antenna. Additionally,  FIG. 8  and  FIG. 9  illustrate respectively the measured radiation patterns of the embedded antennas  200  and  400  at various frequencies. 
         [0034]    Although preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments. Rather, various changes and modifications can be made within the spirit and scope of the present invention, as defined by the following claims.