Patent Publication Number: US-9425508-B2

Title: Antenna structure and wireless communication device using same

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to antenna structures and wireless communication devices, and particularly to an antenna structure for multiband radio signals and a wireless communication device using the same. 
     2. Description of Related Art 
     Wireless communication devices, such as mobile phones, are typically compact, so it is important to configure antennas to make full use of an inner space of the wireless communication devices. However, due to limited space inside the wireless communication devices, it is difficult to match an impetus of signals received or transmitted by the antennas, thereby making it difficult to increase a bandwidth of the antennas. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present antenna structure for multiband radio signals and wireless communication device can be better understood with reference to the following drawings. The components in the various drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present antenna structure for multiband radio signals and wireless communication device. 
         FIG. 1  is a partial schematic view of an antenna structure used in a wireless communication device, according to an exemplary embodiment. 
         FIG. 2  is similar to  FIG. 1 , but shown from another angle. 
         FIG. 3  is a circuit diagram of a first matching module of the wireless communication device. 
         FIG. 4  is a circuit diagram of a second matching module of the wireless communication device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an antenna structure  100  used in a wireless communication device  200 , such as a mobile phone or a tablet computer. The wireless communication device  200  further includes a circuit board  210  and a matching circuit  230  (shown in  FIG. 3 ). The circuit board  210  includes a feed portion  211 . 
     In this embodiment, the antenna structure  100  is a monopole antenna. The antenna structure  100  includes a feed terminal  10 , a first antenna  30 , and a second antenna  50 . The feed terminal  10  is electronically connected to the feed portion  211 . 
     Referring to  FIG. 2 , the first antenna  30  includes a first antenna portion  31  and a second antenna portion  32  connected to the first antenna portion  31 . The first antenna portion  31  includes a first segment  311 , a second segment  312 , and a third segment  313 . A width of the first segment  311  gradually decreases from a distal end of the first antenna portion  31  to a joint portion between the first antenna portion  31  and the second antenna portion  32 . The feed terminal  10  is electronically connected to the first segment  311  and is located adjacent to the joint portion between the first antenna portion  31  and the second antenna portion  32 . An edge of the second segment  312  is connected to an edge of the first segment  311 , and an angle is formed between the connected edges of the first segment  311  and the second segment  312 . In this embodiment, the angle is an obtuse angle. An edge of the third segment  313  is connected to an edge of the second segment  312 , and the third segment  313  is substantially perpendicular to the second segment  312 . The second segment  312  is connected substantially perpendicularly to the second antenna portion  32 , and a joint  33  between the second segment  312  and the second antenna portion  32  is substantially arc-shaped. 
     Both the first antenna  30  and the second antenna  50  are located at a periphery of the circuit board  210 . The second antenna  50  is an arced plate and is located on an outer frame (not shown) of the wireless communication device  200 , such that the second antenna  50  is substantially parallel to and cooperatively defines a space (not labeled) with the antenna portion  32 . In this embodiment, the space defined between the second antenna  50  and the second antenna portion  32  is about 1 millimeter (mm) thick. 
       FIG. 3  and  FIG. 4  show a circuit diagram of the matching circuit  230 . The matching circuit  230  includes a first matching module  231  and a second matching module  232 . Each of the first matching module  231  and the second matching module  232  is electronically connected between the feed portion  211  and the antenna structure  100 . In this embodiment, the first matching module  231  is a high frequency matching circuit, and the second matching module  232  is a low frequency matching circuit. The first matching module  231  includes a first capacitor C 1 , a second capacitor C 2 , a third capacitor C 3 , a fourth capacitor C 4 , a fifth capacitor C 5 , a first inductor L 1 , and a first switch  2310 . The feed portion  211  is electronically connected to the first capacitor C 1 , and the first capacitor C 1  is grounded by the first inductor L 1 . The first switch  2310  includes a first end  2311  and a second end  2312 . The first end  2311  is connected to a joint between the first capacitor C 1  and the first inductor L 1 . The second capacitor C 2 , the third capacitor C 3 , the fourth capacitor C 4 , and the fifth capacitor C 5  are connected in parallel and are electronically connected to the antenna structure  100 . The second end  2312  is selectively connected to the second capacitor C 2 , the third capacitor C 3 , the fourth capacitor C 4 , or the fifth capacitor C 5 . 
     In this embodiment, a capacitance value of the first capacitor C 1  is about 2.5 picofarads (pF), and an inductance value of the first inductor L 1  is about 1.7 nanohenries (nH). A capacitance value of the second capacitor C 2  is about 4.6 pF, and the second capacitor C 2  is configured for performing impedance matching for signals within a Long Term Evolution (LTE) band 3, which has a frequency range from about 1805 megahertz (MHz) to about 1880 MHz. A capacitance value of the third capacitor C 3  is about 2.2 pF, and the third capacitor C 2  is configured for performing impedance matching for signals within a Wideband Code Division Multiple Access (WCDMA) band 2, which has a frequency range from about 1930 MHz to about 1990 MHz. A capacitance value of the fourth capacitor C 4  is about 1.35 pF, and the fourth capacitor C 4  is configured for performing impedance matching for signals within an LTE band 4, which has a frequency range from about 2110 MHz to about 2155 MHz. A capacitance value of the fifth capacitor C 5  is about 0.6 pF, and the fifth capacitor C 5  is configured for performing impedance matching for signals within an LTE band 7, which has a frequency range from about 2620 MHz to about 2690 MHz. 
     The second matching module  232  includes a sixth capacitor C 6 , a seventh capacitor C 7 , a second inductor L 2 , a third inductor L 3 , a fourth inductor L 4 , and a second switch  2320 . The second switch  2320  is substantially similar to the first switch  2310  and includes a first end  2321  and a second end  2322 . The sixth capacitor C 6  and the seventh capacitor C 7  are connected in series between the feed portion  211  and the antenna structure  100 . The second inductor L 2 , the third inductor L 3 , and the fourth inductor L 4  are connected in parallel and are directly grounded. The first end  2321  is electronically connected between the sixth capacitor C 6  and the seventh capacitor C 7 . The second end  2322  is selectively connected to the second inductor L 2 , the third inductor L 3 , or the fourth inductor L 4 . 
     In this embodiment, a capacitance value of the sixth capacitor C 6  is about 1 pF, and a capacitance value of the seventh capacitor C 7  is about 10 pF. An inductance value of the second inductor L 2  is about 14.7 nH, and the second inductor L 2  is configured for performing impedance matching for signals within an LTE band 17, which has a frequency band from about 734 MHz to about 746 MHz. An inductance value of the third inductor L 3  is about 9.6 nH, and the third inductor L 3  is configured for performing impedance matching for signals within a global system for mobile communications (GSM) band 850, which has a frequency from about 869 MHz to about 894 MHz. An inductance value of the fourth inductor L 4  is about 8 nH, and the fourth inductor L 4  is configured for performing impedance matching for signals within a GSM band 900, which has a frequency band from about 925 MHz to about 960 MHz. 
     A working process of the wireless communication device  200  includes the following steps: a current from the circuit board  210  is fed into the feed terminal  10  of the antenna structure  100 . A portion of the current flows to the first antenna portion  31  to form a high-frequency current path, and another portion of the current flows to the second antenna portion  32 . The portion of current that flows to the second antenna portion  32  is electrically coupled to the second antenna  50  to form a low-frequency current path. When the wireless communication device  200  operates in the high frequency band, the first matching module  231  performs impedance matching for signals transmitted or received by the antenna structure  100 . Depending on the frequency of signals transmitted or received by the antenna structure  100 , the first switch  2310  is selectively connected to the second capacitor C 2 , the third capacitor C 3 , the fourth capacitor C 4 , or the fifth capacitor C 5 . For example, if the frequency of the signals transmitted or received by the antenna structure  100  is within the LTE band 3 (1805 MHz-1880 MHz), the first switch  2310  is electronically connected to the second capacitor C 2 . 
     When the wireless communication device  200  operates in the low frequency band, the second matching module  232  performs impedance matching for signals transmitted or received by the antenna structure  100 . Depending on the frequency of signals transmitted or received by the antenna structure  100 , the second switch  2320  is selectively connected to the second inductor L 2 , the third inductor L 3 , or the fourth inductor L 4 . For example, if the frequency of the signals received by the antenna structure  100  is within the LTE band 17 (734 MHz-746 MHz), the second switch  2320  is electronically connected to the second inductor L 2 . 
     The first antenna  30  and the second antenna  50  make full use of an inner space of the wireless communication device  200 . The matching circuit  230  performs impedance matching for signals transmitted or received by the antenna structure  100  to increase a bandwidth of the antenna structure  100 . 
     It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of structures and functions of various embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.