Patent Publication Number: US-2016248153-A1

Title: Pcb board, terminal and method for improving anti-interference capability of pcb board

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to the field of PCB design, especially to a PCB board, a terminal and a method for improving an anti-interference capability of the PCB board. 
     BACKGROUND 
     At present, PCB boards are more and more widely used. Since functional application chips on the PCB become more and more, various base-band radio frequency (RF) chips are integrated into a same PCB mainboard, which causes a prominent electromagnetic perturbation problem on the PCB mainboard. Interference signals having different frequency spectrums are generally measured at a common ground terminal of the PCB board. Such interference signals radiate out by using the mainboard ground as an antenna, and some frequencies fall into a frequency band of a working antenna, which brings out a great interference to signals of the working antenna. This is the reason why a power sensitivity of cable test is normal in items, but the index by the coupling OTA test is poor. During the development of the PCB board of the terminal, in many terminal items, the interference signals may be measured at the common ground terminal of the mainboard, and some of these interference signals are within the RF working frequency band, such interference signals radiate out via ground, which reflects the coupling performance of the terminal, and the radiating area is near to the location of the antenna, once the radiated in-band signals are relatively strong, they would affect the wireless performance of the terminal. The RF debugging means can only slightly solve this problem, such fault is a recurrent fault of the current smart terminal, and when the fault is serious, the success of the item may be even affected. The interference to the working antenna of the PCB brings out many troubles to the terminal items, and it is very difficult to deal with it. 
     SUMMARY 
     From above, the system of the embodiments of the present disclosure provides a PCB board, a terminal and a method for improving an anti-interference capability of the PCB board, which solve the interference problem to the working antenna by the interference signals on the common ground terminal of the PCB board. 
     The embodiments of the present disclosure provide a PCB board including a working antenna and an anti-interference antenna, wherein impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board is greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board. 
     In an embodiment of the present disclosure, the working antenna is a monopole antenna. 
     In an embodiment of the present disclosure, the signal input terminal of the anti-interference antenna is connected to the common ground terminal. 
     In an embodiment of the present disclosure, a resonant frequency of the anti-interference antenna falls into a receiving frequency band of the working antenna. 
     In an embodiment of the present disclosure, the anti-interference antenna is provided with a resonant frequency control circuit. 
     In an embodiment of the present disclosure, polarization orientations of the working antenna and the anti-interference antenna are perpendicular to one another. 
     In an embodiment of the present disclosure, the working antenna and the anti-interference antenna are located at edges on different sides of the PCB board. 
     The present disclosure also provides a mobile terminal of an anti-interference PCB board, wherein the mobile terminal includes the above-mentioned PCB board. 
     The present disclosure also provides a method for enhancing an anti-interference capability of a PCB board, the PCB board having a working antenna, wherein the method includes: providing an anti-interference antenna on the PCB board; and setting impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board to be greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board. 
     In an embodiment of the present disclosure, a monopole antenna is set as the working antenna. 
     In an embodiment of the present disclosure, the signal input terminal of the anti-interference antenna is set to be connected to the common ground terminal. 
     The advantageous effects of the embodiments of the present disclosure are as follows. 
     In the PCB board, the terminal and the method for improving an anti-interference capability of the PCB board provided by the embodiments of the present disclosure, by providing an anti-interference antenna on the PCB board and setting impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board to be greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board, according to the impedance matching principle, the interference signals would be guided to the signal input terminal of the anti-interference antenna. Further, the radiated interference to the working antenna by the anti-interference antenna may be reduced by making the anti-interference antenna be away from the working antenna, and making the polarization orientations of the working antenna and the anti-interference antenna be perpendicular to one another to have different polarizations. Further, the anti-interference antenna is provided with the resonant frequency control circuit, thereby the resonant frequency of the anti-interference antenna may be fine-tuned. In this way, it is ensured that the signals entered into the working antenna are relatively pure, thereby power conversion may be carried out by utilizing the antenna to the most extent, and the anti-interference capability of the working antenna is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of principle of an anti-interference PCB board according to embodiments of the present disclosure; 
         FIG. 2  is a structural schematic diagram of a mode of setting the anti-interference antenna according to an embodiment of the present disclosure; 
         FIG. 3  is a structural schematic diagram of a mode of setting the anti-interference antenna according to another embodiment of the present disclosure; 
         FIG. 4  is a structural schematic diagram of a mode of setting the anti-interference antenna according to another embodiment of the present disclosure; and 
         FIG. 5  is a flow chart of a method for enhancing an anti-interference capability of a PCB board according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, further detailed description of the present disclosure would be given by the specific embodiments in combination with the drawings. 
     As shown in  FIG. 1 , the embodiments of the present disclosure provides an anti-interference PCB board including a working antenna, the anti-interference PCB board is further provided with an anti-interference antenna, and impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board is greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board. 
     In the present embodiment, a common ground terminal  2  of a mainboard is proposed to be used as a radiating antenna of interference signals. Various interference signals are generated at the common ground terminal  2  of the mainboard due to the operations of various components on the mainboard, all the interference signals with different frequencies would flow to the common ground terminal  2 , and the common ground terminal  2  would radiate a large amount of interference signals. When the working antenna  1  is relatively near to the common ground terminal  2 , the radiated interference signals (especially the interference signals with the frequency falling within a working frequency band of the working antenna, and especially when the signals are relatively strong) generated at the common ground terminal  2  would enter into the working antenna  1  via the signal input terminal of the working antenna  1  to disturb the working antenna. By providing an anti-interference antenna  3  on the PCB board, and making impedance existing between a signal input terminal of the working antenna  1  and the common ground terminal  2  be greater than impedance between the signal input terminal of the anti-interference antenna  3  and the common ground terminal  2 , according to the impedance matching principle, the interference signals existing at the common ground terminal  2  would be guided to the anti-interference antenna  3 , rather than flowing to the working antenna  1  from the common ground terminal  2 . In this way, the interference signals enter into the anti-interference antenna  3 , thereby reducing the interference from the interference signals to the working antenna  1 . 
     Further, in order to make the impedance between the signal input terminal of the working antenna  1  and the common ground terminal be as large as possible, the ground of the working antenna and the signal input terminal of the working antenna are not conducted (that is, there is a relatively large impedance between the signal input terminal of the working antenna and the common ground terminal, thereby the interference signals at the common ground terminal of the mainboard would not flow to the working antenna from the common ground terminal). In this way, the interference signals at the common ground terminal may flow to the anti-interference antenna better, thereby reducing the impact on the working antenna. For example, when the working antenna is a monopole antenna, since the monopole antenna has no ground pin, i.e., the working antenna is not conducted with the common ground terminal, the impedance of the working antenna is relatively large. Other antennas not conducted with the common ground terminal may obtain a relatively large impedance, and thus the interference signals at the common ground terminal flow to the anti-interference antenna. 
     Further, in order to make the impedance between the signal input terminal of the anti-interference antenna  1  and the common ground terminal be as small as possible, in the embodiments of the present disclosure, the impedance between the signal input terminal of the working antenna and the common ground terminal of the PCB board is made be greater than the impedance between the signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board, then the interference signals may be led to the anti-interference antenna. Thereby, when satisfying the above condition, since the interference signals at the common ground terminal of the mainboard would flow to the anti-interference antenna connected with the ground of the mainboard, the anti-interference antenna is equivalent to a resonant frequency load of the common ground terminal of the mainboard. And the interference signals on the common ground terminal of the mainboard are leaked out via the anti-interference antenna, thereby a proper load resistor may be added at a matching terminal of the anti-interference antenna for consuming the energy of the interference signals and reducing the radiating strength of the interference signals on the premise that the flowing direction of the interference signals is ensured. Especially, it is possible to make the ground of the working antenna be connected and conducted with the signal input terminal of the working antenna (that is, there is a relatively small impedance between the signal input terminal of the anti-interference antenna and the common ground terminal, thereby the interference signals at the common ground terminal of the mainboard would flow to the anti-interference antenna from the common ground terminal), thus the interference signals at the common ground terminal may be properly enabled to flow to the anti-interference antenna, so as to reduce the impact on the working antenna. 
     Further, since the main interference to the working antenna is the interference signal having a frequency falling within a working frequency band of the working antenna, by leading the interference signals having the frequencies falling within the working frequency band of the working antenna to the anti-interference antenna as much as possible to radiate out the interference signals, and making the resonance frequency of the anti-interference signal falling into the frequency band of the working antenna, the interference signals whose frequencies fall within the frequency band of the working antenna at the common ground terminal can be guided to the anti-interference antenna as far as possible, and such interference signals having relatively great influence to the working antenna may be radiated out as much as possible via the anti-interference antenna, thereby reducing the impact on the working antenna. In order to better control the resonant frequency of the anti-interference antenna, a resonant frequency control circuit is provided at the anti-interference antenna, thereby the resonant frequency of the anti-interference antenna may be fine-tuned, and the interference signals greatly affecting the working antenna enter into the anti-interference antenna to be radiated out better. For example, a it-type matching circuit is provided at the anti-interference antenna, thereby the resonant frequency and the impedance of the anti-interference antenna may be fine-tuned. Also, other different types of circuits may be provided for adjusting the resonant frequency of the antenna. 
     Further, since the interference signals are radiated out via the anti-interference antenna, the radiated out interference signals may also enter into the signal input terminal of the working antenna. In order to better avoid the interference to the working antenna by the interference signals, by utilizing the effect of different polarizations, an isolation between the interference signals and the working antenna may be improved, and the anti-interference capability of the working antenna is improved. For example, the polarization orientation of the working antenna is a horizontal polarization, and the polarization orientation of the anti-interference antenna is a vertical polarization, then the polarization orientations of them are mutually perpendicular, and a space isolation therebetween is relatively large, thereby the radiation influence occurred therebetween is relatively small. Similarly, when the polarization orientation of the working antenna is the vertical polarization, the polarization orientation of the anti-interference antenna may be set to be the horizontal polarization. Other manners of setting the polarization orientations of the working antenna and the anti-interference antenna to be different may also increase separation between the interference signals and the main antenna, and improve the anti-interference capability of the main antenna. 
     Further, the anti-interference antenna is made be far from the working antenna, and the anti-interference antenna and the working antenna are located at edges on different sides of the PCB board, for example, the anti-interference antennal is located at an adjacent side or an opposite side of the working antenna. In the present embodiment, a rectangle PCB board is used as an example for detailed explanations. As shown in  FIG. 2 , the working antenna is provided at a lower side of the PCB board, and the anti-interference antenna is provided at a left side of the PCB board. As shown in  FIG. 3 , the working antenna is provided at the lower side of the PCB board, and the anti-interference antenna is provided at an upper side of the PCB board. As shown in  FIG. 4 , the working antenna is provided at the lower side of the PCB board, and the anti-interference antenna is provided at a right side of the PCB board. There may be other settings, as long as the working antenna is away from the anti-interference antenna to reduce the radiation influence to the working antenna by the anti-interference antenna. 
     The embodiments of the present disclosure also provide a terminal including the above-mentioned PCB board. For example, the working antenna is an antenna for a 2G network, an antenna for a 3G network, an antenna for a WIFI network, an antenna for Bluetooth, or an antenna for GPS network. In various mobile terminals, such as a mobile TV, a vehicle-mounted device, a tablet computer and the like, especially in a phone terminal, the working antenna of the phone terminal is provided at a bottom of the phone, and generally components, such as mic, speaker and the like, are laid at the bottom of the phone, such components in the original antenna design would couple the signals including other various high speed signals into the working antenna, and such signals may enter into the working antenna via the signal input terminal of the working antenna to interfere the operation of the working antenna. After setting the anti-interference antenna, since the impedance between the signal input terminal of the anti-interference antenna and the common ground terminal is less than the impedance between the working antenna and the common ground terminal, such interference signals would be diverted to the anti-interference antenna to ensure that the signals entering into the working antenna is relatively pure, such that the power conversion may be carried out by utilizing the antenna to the maximum extent. 
     The embodiments of the present disclosure also provide a method for enhancing an anti-interference capability of a PCB board, wherein a working antenna and an anti-interference antenna are provided on the PCB board, and impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board is set to be greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board. 
     With reference to  FIG. 5 , the method for enhancing an anti-interference capability of a PCB board provided by the present embodiment includes the following steps. 
     In step  501 , an anti-interference antenna is provided on the PCB board. 
     In step  502 , impedance is set. 
     In the above step  501 , the anti-interference antenna on the PCB board may specifically be provided by: designing an anti-interference antenna, the type of the anti-interference antenna being determined according to particular requirements, and then installing the anti-interference antenna on the PCB board. It should be noted that the position of the antenna may be determined according to specific actual conditions, including a resonant frequency of the antenna, impedance circuit of the antenna, a polarization orientation of the antenna, a load of the antenna, and the like. 
     In the above step  502 , the impedance may specifically be set by: setting impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board to be greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board. 
     When the above conditions are satisfied, it is preferable to make the impedance between the working antenna and the common ground terminal be as large as possible, that is, to make the working antenna and the common ground terminal not conducted. For example, a monopole antenna is set as the working antenna, and other antennas which are not conducted with the common ground terminal may also be used as the working antenna. 
     Similarly, it is possible to make the impedance between the anti-interference antenna and the common ground terminal be as small as possible, that is, to make the anti-interference antenna and the common ground terminal be connected and conducted, then it can be ensured that the impedance between the anti-interference antenna and the common ground terminal besides the load and the impedance of the circuit per se is minimum. As long as the above condition that the impedance between the signal input terminal of the working antenna and the common ground terminal of the PCB board is greater than the impedance between the signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board is satisfied, any other settings are feasible. 
     The embodiments of the present disclosure improve the anti-interference capability of the working antenna on the PCB board, make the interference signals on the PCB board to be radiated out via the anti-interference antenna, reduce the radiation influence to the working antenna by the interference signals, and improve the anti-interference capability of the working antenna. 
     The above-mentioned contents are only preferable embodiments of the present disclosure, which do not tend to limit the protection scope of the present disclosure. 
     INDUSTRY APPLICABILITY 
     In the PCB board, the terminal and the method for improving an anti-interference capability of the PCB board provided by the embodiments of the present disclosure, by providing an anti-interference antenna on the PCB board and setting impedance between a signal input terminal of the working antenna and a common ground terminal of the PCB board to be greater than impedance between a signal input terminal of the anti-interference antenna and the common ground terminal of the PCB board, according to the impedance matching principle, the interference signals would be guided to the signal input terminal of the anti-interference antenna. Further, the radiated interference to the working antenna by the anti-interference antenna may be reduced by making the anti-interference antenna be away from the working antenna, and making the polarization orientations of the working antenna and the anti-interference antenna be perpendicular to one another to have different polarizations. Further, the anti-interference antenna is provided with the resonant frequency control circuit, thereby the resonant frequency of the anti-interference antenna may be fine-tuned. In this way, it is ensured that the signals entered into the working antenna are relatively pure, thereby power conversion may be carried out by utilizing the antenna to the most extent, and the anti-interference capability of the working antenna is improved.