Abstract:
An antenna module includes an antenna set, a feeding point and a ground plane. The antenna set includes a first antenna, and a second antenna. The first antenna has a first resonant frequency and the second antenna a second resonant frequency.

Description:
BACKGROUND 
       [0001]    1. Field of the Disclosure 
         [0002]    The disclosure relates to an antenna module, and specifically to a dual band antenna module and a portable electronic device using the same. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Radiotelephones typically include an antenna for transmitting and receiving wireless communications signals. Conventionally, external monopole and dipole antennas have been widely used in various radiotelephone applications, due to their simplicity, wideband response, broad radiation pattern, and low cost. However, the external antennas&#39; susceptibility to damage by external force can result in operation deterioration. Furthermore, radiotelephones must meet demands for reduced size and profile. As such demand grows, the design of hidden antennas has become increasingly popular, with equal diligence afforded to retention and promotion of signal strength and stability. 
         [0005]    Additionally, it is becoming desirable for radiotelephones to operate within multiple frequency to utilize more than one communication system. Consequently, high and low frequency antennas are often used together in cellular phones.  FIG. 1  shows a contemporary internal antenna  10  comprising a first meandering portion  11  and a second meander-shaped portion  12 . The first meander-shaped portion  11  has a first resonant frequency and the second meander-shaped portion  12  has a second resonant frequency. Thus, the antenna  10  can utilize two different frequency bands. 
         [0006]    Unfortunately, the disclosed antenna is susceptible to interference from electromagnetic waves. As a consequence, the antennas are normally oriented away from circuit boards of the cellular phones. However, this makes minimizing the volume of radiotelephones difficult. 
         [0007]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Many aspects of the antenna module can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present antenna module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, in which: 
           [0009]      FIG. 1  is an isometric view of a contemporary internal dual band antenna module; 
           [0010]      FIG. 2  is an isometric view of a portable electronic device, utilizing the antenna module according to an exemplary embodiment; 
           [0011]      FIG. 3  is similar to  FIG. 2 , but viewed from another perspective; 
           [0012]      FIG. 4  is a top view of an antenna module according to an exemplary embodiment; 
           [0013]      FIG. 5  is an isometric view of a portable electronic device equipped with an antenna module according to an exemplary embodiment; 
           [0014]      FIG. 6  shows return loss measurement for the antenna module in  FIG. 5  in a closed state, wherein the x-axis indicates frequency and the y-axis indicates decibel (dB); and 
           [0015]      FIG. 7  shows the return loss measurement for the antenna module in  FIG. 5  in an opened state, wherein the x-axis indicates frequency and the y-axis indicates decibel (dB). 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0016]      FIGS. 2 and 3  show a portable electronic device  100  including a flip cover  102  and a main body  103  connected to the flip cover  102  by a hinge. The flip cover  102  includes a display panel  104 . The main body  103  includes a keypad  105 , a circuit board  106  arranged under the keypad  105  and an antenna module  20  arranged on the bottom of the main body  103  electrically connecting to the circuit board  106 . 
         [0017]    Referring to  FIG. 4 , the antenna module  20  includes a holder  21  supporting a first antenna  42 , a second antenna  44 , a feed point  46  and a ground  48  thereon. 
         [0018]    In the exemplary embodiment, the first antenna  42  and the second antenna  44  are microstrip lines mounted on the holder  21 . The second antenna  44  is located below the first antenna  42  and connected to an end of the first antenna  42 . The feed point  46  and ground  48  are arranged on the holder  21  and electrically connected to the other end of the first antenna  42 . 
         [0019]    The first antenna  42  is a low frequency antenna and the second antenna  44  is a high frequency antenna. The first antenna  42  connects to the second antenna  44  so the two antennas form a single route dual-band monopole antenna. 
         [0020]    The first antenna  42  includes a main portion  422 , a first connecting portion  424  and a second connecting portion  426 . The main portion  422  is mainly a long straight conductive strip. The first connecting portion  424  extends from an end of the main portion  422  and is mounted on the holder  21  so that the first connecting portion  424  connects to the feed point  46 . The second connecting portion  426  extends from the first connecting portion  424  and is mounted on the holder  21  in a meandering structure. In addition, the other end of the second connecting portion  426  electrically connects to the ground  48  arranged on the surface of the holder  21 . 
         [0021]    The second antenna  44  includes a front section  442 , a coupling section  444  and a bent section  446 . The front section  442  is arranged parallel to the main portion  422  of the first antenna  42 . The coupling section  444  extends from an end of the front section  442  as a meandering structure. The meandering structure of the coupling section  444  includes periodically spaced undulations. While, in the illustrated embodiment, each of the periodically spaced undulations has an inverted-U configuration, the meandering structure may follow virtually any type of undulation, without limiting the scope of the disclosure. The width W of each inverted-U portion is preferably equal to the distance D between each inverted-U portion. In alternative embodiments, different meandering structures can provide different coupling effect between the inverted-U portions to change the resonant frequency of the second antenna  44 . The bent section  446  of the second antenna  44  extends from the other end of the coupling section  444 . The bent section  446  connects the main portion  422  of the first antenna  42  and the coupling section  444  of the second antenna  44 . 
         [0022]      FIG. 5  shows a portable electronic device  100  equipped with the antenna module  20  according to an exemplary embodiment. To reduce the coupling effect between the first antenna  42  and the second antenna  44 , the distance between the first antenna  42  and the second antenna  44  is substantially equal to the thickness of the main body  103 . 
         [0023]    In use, the feed point  46  connects to the main portion  422  of the first antenna  42  by the first connecting portion  424 . The first antenna  42  is configured to resonate in frequency bands between approximately 824 MHz to 894 MHz. The second antenna  44  is configured to resonate in frequency bands between approximately 1850 MHz to 1991 MHz. The frequency bands of the antenna  20  may be adjusted by changing the configuration and dimensions of the meandering structure of the coupling section  444  as described above, and/or, for example, changing the number, width, and distance between the inverted-U portions and the distance between the main portion  422  and the coupling section  444 . The antenna  20  covers the low frequency band (about 824 to 894 MHz) and high frequency band (about 1850 to 1991 MHz). 
         [0024]    As described in our copending application, Ser. No. 12/185221, filed August, 2008, and incorporated by reference herein, there are frequency shits depending upon whether a flip phone is in its open state or closed state.  FIG. 6  of the current application shows return loss measurement for the antenna module of  FIG. 5  of the current application in a closed state, wherein the x-axis indicates frequency and the y-axis indicates decibel (dB). The curve represents the frequency characteristics of the first and second antennas  20  in −6 dB return loss. As shown in  FIG. 6 , in a closed condition, the bandwidth of the first antenna  42  is 69 MHz (about 826.5 to 895.5 MHz), and the return loss is about −4.865 dB to −3.163 dB. The bandwidth of the second antenna  44  is 138 MHz (about 1.85 to 1.988 GHz), and the return loss is about −5.079 dB to −13.77 dB. The antenna  20  can operate in low frequency bands, such as between 824 and 894 MHz and high frequency bands, such as between 1850 and 1991 MHz. 
         [0025]      FIG. 7  shows return loss measurement for the antenna module in  FIG. 5  in an opened state, wherein the x-axis indicates frequency and the y-axis indicates decibel (dB). The curve represents the frequency characteristics of the first and second antenna  20  in −6 dB return loss. As shown in  FIG. 7 , in an open condition, the return loss of the first antenna  42  is about −2.880 dB to −11.61 dB. The return loss of the second antenna  44  is about −5.627 dB to −12.82 dB. The antenna  20  can operate at low frequency bands, such as between 824 and 894 MHz and high frequency bands, such as between 1850 and 1991 MHz. 
         [0026]    As described above, the antenna module  20  may be used in various operating frequency bands, beyond those of the cellular phone as illustrated, and/or with other devices requiring an antenna module that facilitates the achievement of fully open and fully closed positions. 
         [0027]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.