Abstract:
A radio-frequency transceiver device capable of reducing a specific absorption rate (SAR) includes an antenna including a radiating element and a grounding element, wherein the radiating element substantially extends along a first direction on a first plane; and a SAR suppression unit, substantially extending along the first direction and an edge of the radiating element of the antenna on the first plane and apart from the edge of the radiating element by a gap, for reducing the SAR of the antenna.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/837,181, filed on Jun. 20, 2013 and entitled “Wireless Communication Device with SAR Suppression Unit”, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a Radio-Frequency transceiver device, and more particularly to a RF transceiver device capable of reducing Specific Absorption Rate and keeping the antenna efficiency or structure. 
         [0004]    2. Description of the Prior Art 
         [0005]    A wireless communication device is equipped with an antenna to emit or receive radio waves, so as to exchange radio-frequency (RF) signals and access a wireless communication system. Radio waves are high-frequency sinusoidal signals, such that every country in the world standardizes the power of radio waves, mainly for preventing from affecting users and/or interfering operations of other wireless communication devices. For example, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) suggests the value of Specific Absorption Rate (SAR) shall not exceed 2.0 W/Kg, while the Federal Communications Commission (FCC) suggests the value of SAR shall not exceed 1.6 W/Kg. SAR represents the absorption rate of a living body unit per the power of electromagnetic waves in a normal electromagnetic radiation environment, taking W/Kg as a unit. Additionally, various communication products are applied to various environments, so that distance factor is further taken into consideration. For example, SAR of handset wireless communication device such as mobile device or smart phones needs to be verified when the distance between the handset wireless communication device and a human body is 20 cm. 
         [0006]    As well known in the art, enhancing antenna efficiency and reducing SAR value are often contradictory, because enhancing antenna efficiency may increase radiating power which increases SAR value. In such a situation, how to keep the antenna efficiency and meanwhile reduce SAR value has become a target of the industry. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore a primary objective of the present invention to provide a radio-frequency transceiver device, capable of reducing a specific absorption rate (SAR). 
         [0008]    An embodiment of the present invention discloses a radio-frequency (RF) transceiver device, capable of reducing a specific absorption rate (SAR), which comprises an antenna, comprising a radiating element and a grounding element, wherein the radiating element substantially extends along a first direction on a first plane; and a SAR suppression unit, substantially extending along the first direction and an edge of the radiating element of the antenna on the first plane and apart from the edge of the radiating element by a gap, for reducing the SAR of the antenna. 
         [0009]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  is a schematic diagram of a wireless communication device according to an embodiment of the present invention. 
           [0011]      FIG. 1B  is a schematic diagram depicting three main body scenarios when a user is operating the wireless communication device shown in  FIG. 1A . 
           [0012]      FIG. 1C  illustrates a schematic diagram of structures of a SAR suppression unit and an antenna shown in  FIG. 1A . 
           [0013]      FIG. 2  is a schematic diagram of an RF transceiver device according to an embodiment of the present invention. 
           [0014]      FIGS. 3A ,  3 B,  4 A and  4 B illustrate schematic diagrams of simulated radiation patterns before and after the RF transceiver device shown in  FIG. 2  is equipped with a SAR suppression unit. 
           [0015]      FIGS. 5A ,  5 B,  6 A and  6 B are schematic diagrams of electric field of an antenna of the RF transceiver device shown in  FIG. 2  without and with a SAR suppression unit. 
           [0016]      FIGS. 7 ,  8  and  9  are schematic diagrams of RF transceiver devices according to embodiments of the present invention. 
           [0017]      FIG. 10  illustrates a 3D schematic diagram of an RF transceiver device according to an embodiment of the present invention. 
           [0018]      FIG. 11  is a schematic diagram of an antenna according to an embodiment of the present invention. 
           [0019]      FIGS. 12 and 13  are schematic diagrams of RF transceiver devices according to embodiments of the present invention. 
           [0020]      FIG. 14  is a schematic diagram of Voltage Standing Wave Ratio of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13 . 
           [0021]      FIGS. 15A-15C  are schematic diagrams of electric fields of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 2.21 GHz. 
           [0022]      FIGS. 16A-16C  are schematic diagrams of SAR fields of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 2.21 GHz. 
           [0023]      FIGS. 17A-17C  are schematic diagrams of surface currents (Jsurf) of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 2.21 GHz. 
           [0024]      FIGS. 18A-18C  are schematic diagrams of electric fields of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 5.51 GHz. 
           [0025]      FIGS. 19A-19C  are schematic diagrams of SAR fields of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 5.51 GHz. 
           [0026]      FIGS. 20A-20C  are schematic diagrams of surface currents (Jsurf) of the antenna shown in  FIG. 11 , the RF transceiver device shown in  FIG. 12  and the RF transceiver device shown in  FIG. 13  at 5.51 GHz. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Please refer to  FIG. 1A  and  FIG. 1B .  FIG. 1A  is a schematic diagram of a wireless communication device  10  according to an embodiment of the present invention, and  FIG. 1B  is a schematic diagram depicting three main body scenarios when a user is operating the wireless communication device  10 . The wireless communication device  10  may be a laptop, tablet PC, smart phone, etc., and comprises a SAR suppression unit  102  and an antenna  104 . The antenna  104  comprises a radiating element  106  and a grounding element  108  (and a feeding unit not shown in  FIG. 1A ), and is utilized for transmitting and receiving radio-frequency (RF) signals. The SAR suppression unit  102  may be a conductive unit, a magnetic unit (e.g. ferrite), and is utilized for reducing SAR value of the wireless communication device  10 . Please further refer to  FIG. 1C , which illustrates a schematic diagram of structures of the SAR suppression unit and the antenna  104 . As can be seen from  FIG. 1C , the SAR suppression unit  102  is disposed around or near the radiating element  106  of the antenna  104 , and extends along an edge of the radiating element  106 . In addition,  FIG. 1C  illustrates a plane coordinate system Y-Z. As can be seen, the radiating element  106  is disposed on the Y-Z plane and extends along the horizontal direction (or first direction) Y of  FIG. 1C , while the SAR suppression unit  102  is also disposed on the Y-Z plane, and extends along the horizontal direction Y and the edge of the radiating element  106 . 
         [0028]    In  FIG. 1C , “d” represents a gap between the SAR suppression unit  102  and the antenna  104 , and is substantially between 0.1 mm. and 10 mm; “W” represents a width of the SAR suppression unit  102 , and is substantially greater than 0.1 mm; and “L” represents a length of the SAR suppression unit  102 , and is substantially equal to ¼ wavelength corresponding to a lowest operating frequency of the antenna  104 . With such a structure, the SAR suppression unit  102  can reduce SAR value for each operating band of the antenna  104  while keeping the antenna efficiency or structure of the antenna  104 . 
         [0029]    For example, please refer to  FIG. 2 , which is a schematic diagram of an RF transceiver device  20  according to an embodiment of the present invention, where an X-Y-Z coordinate system is marked. The RF transceiver device  20  comprises a SAR suppression unit  202  and an antenna  204 , which may implement the SAR suppression unit  102  and the antenna  104  shown in  FIGS. 1A-1C , to apply to the wireless communication device  10 . The SAR suppression unit  202  is designed and configured according to the above rule (i.e. disposing position, length, width, gap to the antenna  204 , etc.), and therefore, can reduce SAR values for each operating band of the antenna  204  while keeping the antenna efficiency or structure of the antenna  204 . Measurement results are shown in Tables I-V: 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Without SAR suppression unit 202 at 2462 MHz 
               
             
          
           
               
                 Test Position 
                 Measured SAR 1 g (W/kg) 
                 Scaled SAR 1 g (W/kg) 
               
               
                   
               
             
          
           
               
                 Position 1 
                 1.22 
                 1.547 
               
               
                 Position 2 
                 0.353 
                 0.447 
               
               
                 Position 3 
                 0.733 
                 0.929 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 With SAR suppression unit 202 at 2462 MHz 
               
             
          
           
               
                 Test Position 
                 Measured SAR 1 g (W/kg) 
                 Scaled SAR 1 g (W/kg) 
               
               
                   
               
               
                 Position 1 
                 0.857 
                 1.086 
               
               
                 Position 2 
                 0.252 
                 0.319 
               
               
                 Position 3 
                 0.575 
                 0.729 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE III 
               
             
             
               
                   
               
               
                 Without SAR suppression unit 202 at 5785 MHz 
               
             
          
           
               
                 Test Position 
                 Measured SAR 1 g (W/kg) 
                 Scaled SAR 1 g (W/kg) 
               
               
                   
               
             
          
           
               
                 Position 1 
                 2.55 
                 3.323 
               
               
                 Position 2 
                 1.3 
                 1.694 
               
               
                 Position 3 
                 0.787 
                 1.026 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE IV 
               
             
             
               
                   
               
               
                 With SAR suppression unit 202 at 5785 MHz 
               
             
          
           
               
                 Test Position 
                 Measured SAR 1 g (W/kg) 
                 Scaled SAR 1 g (W/kg) 
               
               
                   
               
             
          
           
               
                 Position 1 
                 0.404 
                 0.526 
               
               
                 Position 2 
                 0.276 
                 0.36 
               
               
                 Position 3 
                 0.252 
                 0.328 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE V 
               
               
                   
               
               
                   
                   
                   
                 Antenna gain 
                   
               
               
                   
                   
                   
                 without SAR 
                 Antenna gain with 
               
               
                   
                 Frequency 
                 Gain 
                 suppression unit 
                 SAR suppression 
               
               
                 Band 
                 (MHz) 
                 Spec 
                 202 
                 unit 202 
               
               
                   
               
             
             
               
                 802.11g 
                 2400 
                 −4.3 
                 −3.50 
                 −3.65 
               
               
                   
                 2450 
                 −4.3 
                 −3.68 
                 −3.70 
               
               
                   
                 2500 
                 −4.3 
                 −3.25 
                 −3.25 
               
               
                 802.11a 
                 5150 
                 −5.3 
                 −2.57 
                 −2.88 
               
               
                   
                 5250 
                 −5.3 
                 −2.67 
                 −2.91 
               
               
                   
                 5350 
                 −5.3 
                 −2.53 
                 −3.11 
               
               
                   
                 5470 
                 −5.3 
                 −2.88 
                 −3.44 
               
               
                   
                 5600 
                 −5.3 
                 −2.78 
                 −3.06 
               
               
                   
                 5725 
                 −5.3 
                 −3.06 
                 −3.34 
               
               
                   
                 5785 
                 −5.3 
                 −3.33 
                 −3.85 
               
               
                   
                 5850 
                 −5.3 
                 −3.40 
                 −4.08 
               
               
                   
               
             
          
         
       
     
         [0030]    Tables I-IV show SAR values measured at three test positions (e.g. front surface, edge, bottom as shown in  FIG. 1B ), at 2462 MHz and 5785 MHz, for scenarios of the RF transceiver device  20  equipped with or without SAR suppression unit  202 . Table V represent measurement results of passive gains of the antenna  204  in the band 802.11a and 802.11g with and without the SAR suppression unit  202 . As can be seen from Tables I-IV, the SAR suppression unit  202  obviously reduces SAR values, for example, reduces SAR of the test position  1  by 0.46 (W/kg) at 2462 MHz and by 2.8 (W/kg) at 5785 MHz. Therefore, the SAR suppression unit  202  can efficiently reduce the SAR values of the antenna  204  at different operating frequencies. Moreover, as can be seen from Table V, the passive gains of the antenna  204  substantially keep at the same levels no matter whether the SAR suppression unit  202  is added or not. That is, as the SAR suppression unit  202  reduces the SAR values, the antenna efficiency is kept. 
         [0031]    Furthermore, please refer to  FIGS. 3A ,  3 B,  4 A and  4 B, which illustrate schematic diagrams of simulated radiation patterns before and after the RF transceiver device  20  is equipped with the SAR suppression unit.  FIGS. 3A and 3B  are schematic diagrams of X-Z and Y-Z (relationships between X-Z or Y-Z plane and the antenna  204  can refer to  FIG. 2 ) radiation patterns of the antenna  204  simulated by HFSS at 2 GHz without and with the SAR suppression unit  202 , and  FIGS. 4A and 4B  are schematic diagrams of X-Z and Y-Z radiation patterns of the antenna  204  simulated by HFSS at 5 GHz without and with the SAR suppression unit  202 . As can be seen, after the SAR suppression unit  202  is added, the gains of the antenna  204  are reduced by 2-3 dB around 0° at both 2 GHz and 5 GHz and in both X-Z plane and Y-Z plane. Therefore, the patterns are changed to reduce SAR value. 
         [0032]      FIGS. 5A and 5B  are schematic diagrams of electric field (E-field) of the antenna  204  at 2 GHz without and with the SAR suppression unit  202 , and  FIGS. 6A and 6B  are schematic diagrams of electric field of the antenna  204  at 5 GHz without and with the SAR suppression unit  202 . As can be seen from  FIGS. 5A ,  5 B,  6 A,  6 B, after the SAR suppression unit  202  is added, the electric field of the antenna  204  is obviously reduced along the Z+ direction, so as to reduce SAR values. 
         [0033]    Note that, the RF transceiver device  20  is an embodiment of the present invention, and those skilled in the art should readily make modifications according to different requirements. For example, the pattern of the antenna  204  or characteristics of the SAR suppression unit  202 , such as shape, size, material, distance to the antenna  204 , etc., can be altered according to different requirements. Please refer to  FIGS. 7 to 9 , which are schematic diagrams of RF transceiver devices  70 ,  80  and  90  according to embodiments of the present invention. The RF transceiver devices  70 ,  80  and  90  are derived from the RF transceiver device  20  by replacing the SAR suppression unit  202  with SAR suppression units  702 ,  802  and  902  respectively. Thus, the SAR suppression units  702 ,  802  and  902  can also reduce SAR values for each operating band of the antenna  204  while keeping the antenna efficiency or structure of the antenna  204 . The major difference between the SAR suppression units  702 / 802  and the SAR suppression unit  202  is the SAR suppression units  702 / 802  respectively include a bend at one side. And, the major difference between the SAR suppression unit  902  and the SAR suppression unit  202  is the SAR suppression unit  902  includes bends at two sides. 
         [0034]    In the above examples, the SAR suppression unit  202  and the antenna  204  extends on the same plane; however, the present invention is not limited thereto. For example, please refer to  FIG. 10 , which illustrates a 3D schematic diagram of an RF transceiver device  110  according to an embodiment of the present invention. The structure of the RF transceiver device  110  is similar to that of the RF transceiver device  20 , and the difference is that a SAR suppression unit  1102  of the RF transceiver device  110  extends on the X-Y plane, and the antenna  204  extends on Y-Z plane. In other words, the SAR suppression unit  1102  and the antenna  204  extend on different planes, which still conforms to the scope of the present invention. Therefore, the SAR suppression unit  1102  can reduce SAR values for each operating band of the antenna  204  while keeping the antenna efficiency or structure of the antenna  204 . 
         [0035]    In addition, the antenna  204  is an example for illustration. In fact, the SAR suppression unit  202  or its derivatives (e.g. the SAR suppression units  702 ,  802  and  902  shown in  FIGS. 7-9 ) are suitable for different kinds of antennas, and can be appropriately adjusted according to different requirements. For example,  FIG. 11  is a schematic diagram of an antenna  1104  according to an embodiment of the present invention. The antenna  1104  is similar to the antenna  204 , and can operate in dual band (2 GHz, 5 GHz), such that the SAR suppression unit  202  or its derivatives can apply to the antenna  1104 , to reduce SAR values for each operating band of the antenna  1104  while keeping the antenna efficiency or structure of the antenna  1104 . For example,  FIGS. 12 and 13  are schematic diagrams of RF transceiver devices  1200  and  1300  according to embodiments of the present invention. The RF transceiver devices  1200  and  1300  add SAR suppression units  1202  and  1302  around the radiating element of the antenna  1104  respectively, and the difference between the RF transceiver devices  1200  and  1300  is d 1 /d 2 , which are distances between the SAR suppression units  1202 / 1302  and the antenna  1104 . In such a situation, the RF transceiver devices  1200 ,  1300  can reach different SAR suppression effects. 
         [0036]    In detail, please refer to  FIG. 14 ,  15 A- 15 C,  16 A- 16 C,  17 A- 17 C,  18 A- 18 C,  19 A- 19 C and  20 A- 20 C.  FIG. 14  is a schematic diagram of Voltage Standing Wave Ratio (VSWR) of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13 , where the solid curve represents VSWR of the antenna  1104  without the SAR suppression unit  1202  or  1302 , the dashed curve represents VSWR of the RF transceiver device  1200 , and the dotted line represents VSWR of the RF transceiver device  1300 . As can be seen from  FIG. 14 , even if the SAR suppression unit  1202  or  1302  is added, the RF transceiver device  1200  or the RF transceiver device  1300  still operates in dual band accurately, so as to maintain the structure of the antenna  1104 . Moreover,  FIGS. 15A-15C  are schematic diagrams of electric fields of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 2.21 GHz.  FIGS. 16A-16C  are schematic diagrams of SAR fields of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 2.21 GHz.  FIGS. 17A-17C  are schematic diagrams of surface currents (Jsurf) of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 2.21 GHz.  FIGS. 18A-18C  are schematic diagrams of electric fields of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 5.51 GHz.  FIGS. 19A-19C  are schematic diagrams of SAR fields of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 5.51 GHz.  FIGS. 20A-20C  are schematic diagrams of surface currents (Jsurf) of the antenna  1104  shown in  FIG. 11 , the RF transceiver device  1200  shown in  FIG. 12  and the RF transceiver device  1300  shown in  FIG. 13  at 5.51 GHz. As can be seen from  FIGS. 15A-15C ,  16 A- 16 C,  17 A- 17 C,  18 A- 18 C,  19 A- 19 C and  20 A- 20 C, at both 2.21 GHz and 5.51 GHz, the SAR suppression unit  1202  or  1302  indeed reduces vertical electric field of the antenna  1104 , to reduce the SAR value, and causes little influence on the surface current, to maintain the antenna efficiency. 
         [0037]    In the prior art, reducing SAR value inevitably reduces antenna efficiency, such that maintaining antenna efficiency and reducing the SAR value cannot be reached simultaneously. In comparison, the present invention adds the SAR suppression unit around the radiating element of the antenna, which can reduce SAR values for each operating band of the antenna while keeping the antenna efficiency or structure of the antenna. 
         [0038]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.