Patent Publication Number: US-11024964-B2

Title: Antenna system and mobile terminal

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of antenna technologies, and in particular, to an antenna system and a mobile terminal. 
     BACKGROUND 
     In wireless communication devices, there is always a device that radiates electromagnetic energy into space and receives electromagnetic energy from space, and this device is an antenna. The role of the antenna is to transmit a digital or analog signal modulated onto a radio frequency (RF) frequency to a spatial wireless channel, or to receive a digital or analog signal modulated onto a RF frequency from a spatial wireless channel. 
     Metal frame architectures are mainstream solutions in the mobile phone structure design, which can provide the better protection, aesthetics, thermal diffusion and user experience. However, due to the shielding effect of metal on electromagnetic waves, radiation performance of an antenna will be seriously affected and the gain of the antenna will be reduced. 
     Therefore, it is necessary to provide a new antenna system to solve the above problems. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Many aspects of the exemplary embodiment can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a structural schematic diagram of an antenna system according to the present disclosure; 
         FIG. 2  schematically illustrates a circuit structure of an antenna system according to the present disclosure; 
         FIG. 3  illustrates a passive efficiency of an antenna system according to the present disclosure; 
         FIG. 4  is a return loss graph of an antenna system according to the present disclosure in state 1; 
         FIG. 5  is a return loss graph of an antenna system according to the present disclosure in state 2; 
         FIG. 6  is a return loss graph of an antenna system according to the present disclosure in state 3; 
         FIG. 7  is a return loss graph of an antenna system according to the present disclosure in state 4; 
         FIG. 8  is a return loss graph of an antenna system according to the present disclosure in state 5; 
         FIG. 9  is a return loss graph of an antenna system according to the present disclosure in state 6; and 
         FIG. 10  is a return loss graph of an antenna system according to the present disclosure in state 7. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be further illustrated with reference to the accompanying drawings and the embodiments. 
     Referring to  FIG. 1  and  FIG. 2 , an embodiment of the present disclosure provides an antenna system  100  which includes a metal housing  1 , a circuit board  2  and an antenna unit  3 . The circuit board  2  is located in the metal housing  1 . The circuit board  2  includes a radio frequency feeding source  21  and a tunable capacitor  22 . The metal housing  1  includes a radiation frame  10  and a grounded back shell  11  spaced apart from the radiation frame  10 . A fracture  12  is formed between each of two ends of the radiation frame  10  and the grounded back shell  11 . The radiation frame  10  and the grounded back shell  11  are connected by a connecting rib  13 . The radiation frame  10  is a primary radiator of low frequency. 
     The antenna unit  3  is connected to the radio frequency feeding source  21  and arranged to be coupled to the radiation frame  10  to serve as a primary radiator of medium-high frequency. 
     The tunable capacitor  22  is connected to the radiation frame  10 . Specifically, the tunable capacitor  22  is connected in series between the radiation frame  10  and the system ground, and the metal back shell  1  can be used as the system ground, such that an electrical length of the antenna system  100  can be changed by switching to different capacitances of the tunable capacitor  22 , thereby achieving that the radiation frequency of the antenna system  100  covers 790-960 MHz and 1710-2690 MHz. In a preferred embodiment of the present disclosure, the tunable capacitor  22  has a capacitance ranging from 0.75 pF to 3.1 pF. Depending on different capacitances, the antenna system  100  will operate in different bands, i.e., the antenna system  100  operates in different states. 
     A case where the antenna system  100  operates in seven different states is taken as an example for detailed description. Refer to Table 1 below for details. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Capacitance 
                   
               
               
                 State 
                 (pF) 
                 Frequency Band 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 State 1 
                 0.75 
                 GSM900-TIS/LTE-B7/38/40/41 
               
               
                 State 2 
                 0.9 
                 GSM900-TRP/WCDMA-8/LTE-B8 
               
               
                 State 3 
                 1.05 
                 G5M850-TIS 
               
               
                 State 4 
                 1.28 
                 GSM850-TRP/CDMABC0/WCDMA-5/LTE-B5/ 
               
               
                   
                   
                 WCDMA-1/LTE-B1/TD-A 
               
               
                 State 5 
                 1.74 
                 GSM1900-TIS/TD-F/LTE-B20/LTE-B39 
               
               
                 State 6 
                 1.96 
                 GSM1900-TRP/WCDMA-2/LTE-B2 
               
               
                 State 7 
                 3.1 
                 GSM1800/WCDMA-4/LTE-B3/4 
               
               
                   
               
            
           
         
       
     
     As can be seen from the above Table 1, operating bands of the antenna system  100  can be switched simply by tuning the capacitance of the tunable capacitor  22 . That is, the antenna system  100  can operate in different bands by selecting different states. Refer to  FIGS. 4-10  for return loss of the antenna system  100  in states 1-7 and refer to  FIG. 3  for efficiency. 
     In fact, the tunable capacitor  22  has various states, and the antenna system  100  provided by the present disclosure may have 32 different states, as shown in Table 2. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Capacitance 
               
               
                   
                 DVC Value 
                 State 
                 (pF) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 0x00 
                 0 
                 0.75 
               
               
                   
                 0x01 
                 1 
                 0.83 
               
               
                   
                 0x02 
                 2 
                 0.9 
               
               
                   
                 0x03 
                 3 
                 0.98 
               
               
                   
                 0x04 
                 4 
                 1.05 
               
               
                   
                 0x05 
                 5 
                 1.13 
               
               
                   
                 0x06 
                 6 
                 1.2 
               
               
                   
                 0x07 
                 7 
                 1.28 
               
               
                   
                 0x08 
                 8 
                 1.36 
               
               
                   
                 0x09 
                 9 
                 1.43 
               
               
                   
                 0x0A 
                 10 
                 1.51 
               
               
                   
                 0x0B 
                 11 
                 1.58 
               
               
                   
                 0x0C 
                 12 
                 1.66 
               
               
                   
                 0x0D 
                 13 
                 1.74 
               
               
                   
                 0x0E 
                 14 
                 1.81 
               
               
                   
                 0x0F 
                 15 
                 1.89 
               
               
                   
                 0x10 
                 16 
                 1.96 
               
               
                   
                 0x11 
                 17 
                 2.04 
               
               
                   
                 0x12 
                 18 
                 2.11 
               
               
                   
                 0x13 
                 19 
                 2.19 
               
               
                   
                 0x14 
                 20 
                 2.27 
               
               
                   
                 0x15 
                 21 
                 2.34 
               
               
                   
                 0x16 
                 22 
                 2.42 
               
               
                   
                 0x17 
                 23 
                 2.49 
               
               
                   
                 0x18 
                 24 
                 2.57 
               
               
                   
                 0x19 
                 25 
                 2.65 
               
               
                   
                 0x1A 
                 26 
                 2.72 
               
               
                   
                 0x1B 
                 27 
                 2.8 
               
               
                   
                 0x1C 
                 28 
                 2.87 
               
               
                   
                 0x1D 
                 29 
                 2.95 
               
               
                   
                 0x1E 
                 30 
                 3.02 
               
               
                   
                 0x1F 
                 31 
                 3.1 
               
               
                   
                   
               
            
           
         
       
     
     As can be seen from Table 2, the tunable capacitor  22  can select the operating state of the antenna system  100  simply by changing the capacitance. Without doubt, the number of the states of the antenna system  100  is not limited to 7 in the present disclosure, and in other embodiments, different capacitances and different numbers of states may be selected. 
     The present disclosure also provides a mobile terminal, and the mobile terminal includes the antenna system  100  described above. 
     Compared with the related art, the antenna system  100  provided by present disclosure, by providing the tunable capacitor  22  as a tuner of the antenna system  100 , not only can achieve that the radiation frequency of the antenna system  100  covers 790-960 MHz and 1710-2690 MHz, but also has good radiation performance. 
     What has been described above is only an embodiment of the present disclosure, and it should be noted herein that one ordinary person skilled in the art can make improvements without departing from the inventive concept of the present disclosure, but these are all within the scope of the present disclosure.