Patent Publication Number: US-10784577-B2

Title: Dual-band antenna module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 107110309 filed in Taiwan, Republic of China on Mar. 26, 2018, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technology Field 
     The present invention relates to a dual-band antenna module and particularly relates to a dual-band antenna module capable of avoiding mutual interference between signals using two frequency bands. 
     Description of the Related Art 
     As the needs of users for network communication increase, electronic products often need to support network transmission protocols of different standards, and therefore, different antenna modules are often required to correspond to different types of network signals. For examples, the electronic products need to support wireless communications such as third-generation mobile telecommunication technology (3G), Bluetooth and wireless fidelity (Wi-Fi); and because the frequency bands of all wireless communications are different, different antennas are required to receive and transmit signals. 
     However, as the users have higher and higher requirements for the portability of the electronic products, the electronic products are also required to be lightweight and thin, so that the electronic products with increasingly complicated functions are difficult to provide a large amount of space for accommodating antennas. Under strict space limitation, the design and arrangement of the antennas become more difficult. In the prior art, although the dual-band antenna can resonate to generate signals of different frequency bands in a smaller space to solve the problem of insufficient space, during practical use, in order to avoid mutual interference of the signals of different frequency bands, it is difficult to willfully control the directivity of the signals of different frequency bands, resulting in inconvenience in use. 
     SUMMARY 
     One embodiment of the present invention provides a dual-band antenna module, and the dual-band antenna module comprises a substrate, a dual-band omnidirectional antenna, a low-frequency reflection module and a high-frequency reflection module. 
     The dual-band omnidirectional antenna has a feed-in end disposed on the substrate, and the dual-band omnidirectional antenna is disposed perpendicular to the substrate and is used for resonating to generate a first radio-frequency signal with a first frequency and a second radio-frequency signal with a second frequency, wherein the second frequency is higher than the first frequency. 
     The low-frequency reflection module is disposed on the substrate and is used for selectively reflecting the first radio-frequency signal with the first frequency when the dual-band omnidirectional antenna operates in a directional mode. The low-frequency reflection module includes a first low-frequency reflection unit, a second low-frequency reflection unit and a third low-frequency reflection unit. The first low-frequency reflection unit is activated according to a first low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. The second low-frequency reflection unit is activated according to a second low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. The third low-frequency reflection unit is activated according to a third low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. 
     The high-frequency reflection module is disposed on the substrate and is used for selectively reflecting the second radio-frequency signal with the second frequency when the dual-band omnidirectional antenna operates in the directional mode. The high-frequency reflection module comprises a first high-frequency reflection unit, a second high-frequency reflection unit and a third high-frequency reflection unit. The first high-frequency reflection unit is activated according to a first high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency. The second high-frequency reflection unit is activated according to a second high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency. The third high-frequency reflection unit is activated according to a third high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency. 
     The first low-frequency reflection unit, the second low-frequency reflection unit, the third low-frequency reflection unit, the first high-frequency reflection unit, the second high-frequency reflection unit and the third high-frequency reflection unit are disposed around the dual-band omnidirectional antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a dual-band antenna module according to one embodiment of the present invention. 
         FIG. 2  is a schematic diagram of a first printed circuit board of the dual-band antenna module in  FIG. 1 . 
         FIG. 3  is a schematic diagram of a second printed circuit board of the dual-band antenna module in  FIG. 1 . 
         FIG. 4  is a schematic diagram of a dual-band antenna module according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of a dual-band antenna module  100  according to one embodiment of the present invention. The dual-band antenna module  100  includes a substrate  110 , a dual-band omnidirectional antenna  120 , a low-frequency reflection module  130  and a high-frequency reflection module  140 . 
     The dual-band omnidirectional antenna  120  is capable of resonating to generate a first radio-frequency signal with a first frequency and a second radio-frequency signal with a second frequency, and transmitting the first and second radio-frequency signals in an omnidirectional mode. The second frequency and the first frequency occupy different radio frequency bands, and for example, the second frequency can be higher than the first frequency. For example, in wireless fidelity (Wi-Fi), the second frequency may be within 5 GHz frequency band, and the first frequency may be within 2.4 GHz frequency band. 
     In  FIG. 1 , the feed-in end  120 A of the dual-band omnidirectional antenna  120  is disposed on the substrate  110 , and the dual-band omnidirectional antenna  120  is disposed perpendicular to the substrate  110  so as to generate resonance in perpendicular polarization. In some embodiments of the present invention, the dual-band omnidirectional antenna  120  may include a T-shaped support arm  122  and a pair of extension support arms  124 . The bottom thin end of the T-shaped support arm  122  is coupled to the feed-in end  120 A, and the T-shaped support arm  122  extends from the bottom thin end towards the normal direction of a plane of the substrate  110  (namely the Z-axis direction in  FIG. 1 ) so as to stand on the substrate  110  and is capable of resonating to generate the first radio-frequency signal with the first frequency. 
     The extension support arms  124  are also coupled to the feed-in end  120 A and symmetrically disposed at two sides of the bottom of the T-shaped support arm  122 . For example, the extension support arms  124  are disposed in the +X direction and the −X direction of the T-shaped support arm  122  and are capable of resonating to generate the second radio-frequency signal with the second frequency. 
     Although the dual-band omnidirectional antenna  120  transmits the signals in an omnidirectional mode, the dual-band antenna module  100  is capable of controlling the directivity of the signals of different frequency bands through the low-frequency reflection module  130  and the high-frequency reflection module  140 . 
     In  FIG. 1 , the low-frequency reflection module  130  may include a first low-frequency reflection unit  132 , a second low-frequency reflection unit  134 , a third low-frequency reflection unit  136  and a fourth low-frequency reflection unit  138 . The first low-frequency reflection unit  132  is activated according to a first low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. The second low-frequency reflection unit  134  is activated according to a second low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. The third low-frequency reflection unit  136  is activated according to a third low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. The fourth low-frequency reflection unit  138  is activated according to a fourth low-frequency directional control signal to reflect the first radio-frequency signal with the first frequency. 
     In addition, the first low-frequency reflection unit  132 , the second low-frequency reflection unit  134 , the third low-frequency reflection unit  136  and the fourth low-frequency reflection unit  138  could be disposed on the substrate  110  around the dual-band omnidirectional antenna  120 . Because the first low-frequency reflection unit  132 , the second low-frequency reflection unit  134 , the third low-frequency reflection unit  136  and the fourth low-frequency reflection unit  138  are positioned in different directions of the dual-band omnidirectional antenna  120 , when the first low-frequency reflection unit  132 , the second low-frequency reflection unit  134 , the third low-frequency reflection unit  136  or the fourth low-frequency reflection unit  138  is activated and reflects the first radio-frequency signal with the first frequency, the intensity of the first radio-frequency signal with the first frequency in that direction could be reduced. Therefore, by activating the specific low-frequency reflection unit according to the low-frequency directional control signal, the directivity of the first radio-frequency signal transmitted by the dual-band antenna module  100  is effectively adjusted. 
     For example, in  FIG. 1 , the first low-frequency reflection unit  132  is disposed at a first side of the dual-band omnidirectional antenna  120 , the second low-frequency reflection unit  134  is disposed at a second side of the dual-band omnidirectional antenna  120 , the third low-frequency reflection unit  136  is disposed at a third side of the dual-band omnidirectional antenna  120 , and the fourth low-frequency reflection unit  138  is disposed at a fourth side of the dual-band omnidirectional antenna  120 . In addition, an included angle between the first side and the second side, an included angle between the second side and the third side, an included angle between the third side and the fourth side and an included angle between the fourth side and the first side are substantially identical, which are 90 degrees, for example. For example, in  FIG. 1 , the first side of the dual-band omnidirectional antenna  120  may be at the 0-degree direction of the dual-band omnidirectional antenna  120 , the second side of the dual-band omnidirectional antenna  120  may be at the 90-degree direction of the dual-band omnidirectional antenna  120 , the third side of the dual-band omnidirectional antenna  120  may be at the 180-degree direction of the dual-band omnidirectional antenna  120 , and the fourth side of the dual-band omnidirectional antenna  120  may be at the 270-degree direction of the dual-band omnidirectional antenna  120 . 
     In such cases, when the first low-frequency reflection unit  132  and the second low-frequency reflection unit  134  are activated to reflect the first radio-frequency signal with the first frequency and the third low-frequency reflection unit  136  but the fourth low-frequency reflection unit  138  are not activated, the first radio-frequency signal transmitted by the dual-band antenna module  100  points to a direction between the third side and the fourth side of the dual-band omnidirectional antenna  120 , that is, at the 225-degree direction, which is between 180 degrees and 270 degrees. In other words, if the first radio-frequency signal transmitted by the dual-band antenna module  100  wants to point to a specific direction, the low-frequency reflection unit in the opposite direction of the specific direction may be activated through the corresponding low-frequency directional control signal, so that the intensity of the radio-frequency signal in the opposite direction may be weakened, and the dual-band antenna module  100  is capable of transmitting the first radio-frequency signal, pointing to the specific direction. 
     Similarly, the high-frequency reflection module  140  may include a first high-frequency reflection unit  142 , a second high-frequency reflection unit  144 , a third high-frequency reflection unit  146  and a fourth high-frequency reflection unit  148 . The first high-frequency reflection unit  142  is activated according to a first high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency, the second high-frequency reflection unit  144  is activated according to a second high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency, the third high-frequency reflection unit  146  is activated according to a third high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency, and the fourth high-frequency reflection unit  148  is activated according to a fourth high-frequency directional control signal to reflect the second radio-frequency signal with the second frequency. In addition, the first high-frequency reflection unit  142 , the second high-frequency reflection unit  144 , the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  could be disposed on the substrate  110  around the dual-band omnidirectional antenna  120 . 
     Because the first high-frequency reflection unit  142 , the second high-frequency reflection unit  144 , the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  are positioned in the respective directions of the dual-band omnidirectional antenna  120 , when the first high-frequency reflection unit  142 , the second high-frequency reflection unit  144 , the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  is activated and reflects the second radio-frequency signal with the second frequency, the intensity of the radio-frequency signal with the second frequency in a certain direction could be reduced. Therefore, by activating the specific high-frequency reflection unit according to the high-frequency directional control signal, the directivity of the second radio-frequency signal transmitted by the dual-band antenna module  100  is effectively adjusted. 
     For example, in  FIG. 1 , the first high-frequency reflection unit  142  is disposed at the first side of the dual-band omnidirectional antenna  120  the same side as the first low-frequency reflection unit  132 ; the second high-frequency reflection unit  144  is disposed at the second side of the dual-band omnidirectional antenna  120  the same side as the second low-frequency reflection unit  134 ; the third high-frequency reflection unit  146  is disposed at the third side of the dual-band omnidirectional antenna  120  the same side as the third low-frequency reflection unit  136 ; and the fourth high-frequency reflection unit  148  is disposed at the fourth side of the dual-band omnidirectional antenna  120  the same side as the fourth low-frequency reflection unit  138 . 
     In such cases, when the first high-frequency reflection unit  142  and the second high-frequency reflection unit  144  are activated to reflect the second radio-frequency signal with the second frequency, but the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  are not activated, the second radio-frequency signal transmitted by the dual-band antenna module  100  points to a direction between the third side and the fourth side of the dual-band omnidirectional antenna  120 . 
     In other words, if it is desired that the second radio-frequency signal transmitted by the dual-band antenna module  100  points to a specific direction, the high-frequency reflection unit in the opposite direction of the specific direction may be activated through the corresponding high-frequency directional control signal, so that the intensity of the second radio-frequency signal in the opposite direction may be weakened, and the dual-band antenna module  100  is capable of transmitting the second radio-frequency signal in a mode of pointing to the specific direction. 
     In addition, because the low-frequency reflection module  130  and the high-frequency reflection module  140  may operate independently, in some embodiments, when the dual-band antenna module  100  operates in the directional mode, the first radio-frequency signal and the second radio-frequency signal which are transmitted by the dual-band antenna module  100  is capable of simultaneously pointing to different directions according to the needs of a user. For example, when the first low-frequency reflection unit  132  and the second low-frequency reflection unit  134  are activated but the third low-frequency reflection unit  136  and the fourth low-frequency reflection unit  138  are not activated, the first radio-frequency signal transmitted by the dual-band antenna module  100  points to the 225-degree direction between the third side and the fourth side of the dual-band omnidirectional antenna  120 . Meanwhile, if the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  are activated but the first high-frequency reflection unit  142  and the second high-frequency reflection unit  144  are not activated, the second radio-frequency signal transmitted by the dual-band antenna module  100  points to the 45-degree direction between the first side and the second side of the dual-band omnidirectional antenna  120 . In other words, the first radio-frequency signal and the second radio-frequency signal point to different directions. In other embodiments of the present invention, the first radio-frequency signal and the second radio-frequency signal which are transmitted by the dual-band antenna module  100  is capable of simultaneously pointing to the identical direction according to the needs of the user. 
     In the embodiment of  FIG. 1 , the dual-band antenna module  100  may include a first printed circuit board  150  and a second printed circuit board  160 . The first printed circuit board  150  and the second printed circuit board  160  are locked by crossing each other and stand on the substrate  110  so that the dual-band omnidirectional antenna  120  could be formed on the first printed circuit board  150 , and is positioned at the cross point of the first printed circuit board  150  and the second printed circuit board  160  and is disposed perpendicular to the substrate  110 . In other words, the T-shaped support arm  122  and the pair of extension support arms  124  of the dual-band omnidirectional antenna  120  both could be disposed on the first printed circuit board  150 . 
     In addition, the first low-frequency reflection unit  132 , the first high-frequency reflection unit  142 , the third low-frequency reflection unit  136  and the third high-frequency reflection unit  146  may be formed on the first printed circuit board  150 , and the second low-frequency reflection unit  134 , the second high-frequency reflection unit  144 , the fourth low-frequency reflection unit  138  and the fourth high-frequency reflection unit  148  may be formed on the second printed circuit board  160 . 
       FIG. 2  is a schematic diagram of the first printed circuit board  150  according to one embodiment of the present invention, and  FIG. 3  is a schematic diagram of the second printed circuit board  160  according to one embodiment of the present invention. In the embodiments of  FIG. 2  and  FIG. 3 , mortise and tenon structures A and B are disposed in the middle positions of the first printed circuit board  150  and the second printed circuit board  160 , so that the first printed circuit board  150  and the second printed circuit board  160  cross and lock each other to form the dual-band antenna module  100  shown in  FIG. 1 . 
     In  FIG. 2 , the first high-frequency reflection unit  142  includes a convex reflection element  142 A, a first bias end  142 B, a first inductor  142 C and a first diode  142 D. The first bias end  142 B is capable of receiving a first high-frequency directional control signal SIG HC1 . The first inductor  142 C has a first end and a second end. The first end of the first inductor  142 C is coupled to the first bias end  142 B to receive the first high-frequency directional control signal SIG HC1 , and the second end of the first inductor  142 C is coupled to the convex reflection element  142 A. The first diode  142 D has an anode and a cathode, the anode of the first diode  142 D is coupled to the convex reflection element  142 A, and the cathode of the first diode  142 D is coupled to a ground terminal GND. 
     When a user intends to activate the first high-frequency reflection unit  142  to reflect the second radio-frequency signal with the second frequency, the corresponding first high-frequency directional control signal SIG HC1  is outputted to turn on the first diode  142 D. At this moment, a voltage loop is formed between the first bias end  142 B and the ground terminal GND, and the convex reflection element  142 A is grounded. Thus, the first high-frequency reflection unit  142  is activated to reflect the second radio-frequency signal with the second frequency. In addition, the first inductor  142 C prevents an external radio-frequency signal from causing circuit damage through the first bias end  142 B, and allows the first high-frequency directional control signal SIG HC1  to pass through to turn on or off the first diode  142 D. 
     The first low-frequency reflection unit  132  may include an L-shaped reflection element  132 A, a second bias end  132 B, a second inductor  132 C and a second diode  132 D. The second bias end  132 B is capable of receiving a first low-frequency directional control signal SIG LC1 . The second inductor  132 C has a first end and a second end, and the first end of the second inductor  132 C is coupled to the second bias end  132 B to receive the first low-frequency directional control signal SIG LC1 . The second diode  132 D has an anode and a cathode, and the cathode of the second diode  132 D is coupled to the ground terminal GND. A short arm  132 A 1  of the L-shaped reflection element  132 A is coupled to the anode of the second diode  132 D and the second end of the second inductor  132 C and is perpendicular to the substrate  110 , and a long arm  132 A 2  of the L-shaped reflection element  132 A is parallel to the substrate  110 . 
     When the user intends to activate the first low-frequency reflection unit  132  to reflect the first radio-frequency signal with the first frequency, the corresponding first low-frequency directional control signal SIG LC1  is outputted to turn on the second diode  132 D. At this moment, a voltage loop is formed between the second bias end  132 B and the ground terminal GND, and the L-shaped reflection element  132 A is grounded. Thus, the first low-frequency reflection unit  132  is activated to reflect the first radio-frequency signal with the first frequency. In addition, the second inductor  132 C prevents the external radio-frequency signal from causing circuit damage through the second bias end  132 B, and allows the first low-frequency directional control signal SIG LC1  to pass through to turn on or off the second diode  132 D. 
     In order to effectively reflect the signals, the low-frequency reflection module  130  and the high-frequency reflection module  140  could be disposed in a position corresponding to a quarter of wavelength of the dual-band omnidirectional antenna  120 . For example, if the first frequency of the first radio-frequency signal has a center frequency of 2.4 GHz, the distance between the first high-frequency reflection unit  142  and the feed-in end  120 A of the dual-band omnidirectional antenna  120  may be between 16 mm and 18 mm, and the distance between the first low-frequency reflection unit  132  and the feed-in end  120 A of the dual-band omnidirectional antenna  120  may be between 36 mm and 38 mm. In other words, the first low-frequency reflection unit  132 , the second low-frequency reflection unit  134 , the third low-frequency reflection unit  136  and the fourth low-frequency reflection unit  138  could be disposed at the outer sides of the first high-frequency reflection unit  142 , the second high-frequency reflection unit  144 , the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148 , respectively. 
     In addition, in order to avoid the influence on the high-frequency signal when the low-frequency reflection module  130  is activated, the height of the low-frequency reflection unit of the low-frequency reflection module  130  may be between 0.09 times and 0.12 times the wavelength of the first radio-frequency signal, thereby preventing the radiation pattern of the high-frequency signal from being blocked when the height is too high, and also avoiding the poor reflection effect when the height is too low. For example, if the first frequency of the first radio-frequency signal has a center frequency of 2.4 GHz, the height of the first low-frequency reflection unit is 10 mm. In other words, the short arm  132 A 1  of the L-shaped reflection element  132 A may extend from the dual-band omnidirectional antenna  120  at a distance of 36 mm towards the Z-axis direction by 10 mm, and the long arm  132 A 2  of the L-shaped reflection element  132 A extends towards the dual-band omnidirectional antenna  120  by 12 mm, along a direction parallel to a plane of the substrate  110 . 
     In embodiments of  FIG. 1  to  FIG. 3 , the first low-frequency reflection unit  132 , the second low-frequency reflection unit  134 , the third low-frequency reflection unit  136  and the fourth low-frequency reflection unit  138  may have the identical structure, and the first high-frequency reflection unit  142 , the second high-frequency reflection unit  144 , the third high-frequency reflection unit  146  and the fourth high-frequency reflection unit  148  also may have the identical structure. 
     In addition, in some embodiments of the present invention, in order to have the dual-band antenna module  100  more accurately adjust the directivity of the transmitted signal, the low-frequency reflection module  130  and the high-frequency reflection module  140  may further include a greater number of low-frequency reflection units and high-frequency reflection units which are disposed around the dual-band omnidirectional antenna  120 . Therefore, when a low-frequency reflection unit or a high-frequency reflection unit of the dual-band omnidirectional antenna  120  disposed in a specific direction is activated to reflect the corresponding radio-frequency signal, the radio-frequency signal in the specific direction is reflected, so that the signal transmitted by the dual-band omnidirectional antenna  120  points to the opposite direction of the specific direction. 
     Furthermore, in some embodiments of the present invention, the number of the low-frequency reflection units and the number of the high-frequency reflection units in the low-frequency reflection module  130  and the high-frequency reflection module  140  may be reduced according to the needs of a system.  FIG. 4  is a schematic diagram of a dual-band antenna module  200  according to another embodiment of the present invention. The dual-band antenna module  200  and the dual-band antenna module  100  have similar structures and operating principles. The main difference between the dual-band antenna module  200  and the dual-band antenna module  100  is that a low-frequency reflection module  230  of the dual-band antenna module  200  only includes a first low-frequency reflection unit  232 , a second low-frequency reflection unit  234  and a third low-frequency reflection unit  236 , and a high-frequency reflection module  240  of the dual-band antenna module  200  only includes a first high-frequency reflection unit  242 , a second high-frequency reflection unit  244  and a third high-frequency reflection unit  246 . 
     The first low-frequency reflection unit  232 , the second low-frequency reflection unit  234 , the third low-frequency reflection unit  236 , the first high-frequency reflection unit  242 , the second high-frequency reflection unit  244  and the third high-frequency reflection unit  246  are disposed on a substrate  210  and are disposed around a dual-band omnidirectional antenna  220 . 
     In  FIG. 4 , the first low-frequency reflection unit  232  and the first high-frequency reflection unit  242  is disposed at the first side of the dual-band omnidirectional antenna  220 , namely the 0-degree direction as shown in  FIG. 4 ; the second low-frequency reflection unit  234  and the second high-frequency reflection unit  244  is disposed at the second side of the dual-band omnidirectional antenna  220 , namely the 120-degree direction as shown in  FIG. 4 ; the third low-frequency reflection unit  236  and the third high-frequency reflection unit  246  are disposed at the third side of the dual-band omnidirectional antenna  220 , namely the 240-degree direction as shown in  FIG. 4 . In other words, an included angle between the first side and the second side of the dual-band omnidirectional antenna  220 , an included angle between the second side and the third side of the dual-band omnidirectional antenna  220  and an included angle between the third side and the first side of the dual-band omnidirectional antenna  220  are 120 degrees. 
     In such cases, when the first high-frequency reflection unit  242  and the second high-frequency reflection unit  244  are activated but the third high-frequency reflection unit  246  is not activated, the second radio-frequency signal transmitted by the dual-band antenna module  200  points to the third side of the dual-band omnidirectional antenna  220 , namely, the 240-degree direction shown in  FIG. 4 . 
     Similarly, when the first low-frequency reflection unit  232  and the second low-frequency reflection unit  234  are activated but the third low-frequency reflection unit  236  is not activated, the first radio-frequency signal transmitted by the dual-band antenna module  200  points to the third side of the dual-band omnidirectional antenna  220 , namely, the 240-degree direction shown in  FIG. 4 . 
     In other words, the dual-band antenna module  200  is still capable of independently controlling the directivity of the signals of different frequency bands through the low-frequency reflection module  230  and the high-frequency reflection module  240 . 
     In conclusion, the dual-band antenna module provided by the embodiments of the present invention includes the low-frequency reflection module and the high-frequency reflection module. The low-frequency reflection module and the high-frequency reflection module could be disposed around the dual-band omnidirectional antenna and activate the low-frequency reflection unit or the high-frequency reflection unit in a specific direction, which allows the radio-frequency signal transmitted to the specific direction to be reflected, thereby controlling the directivity of the transmitted signal. In addition, because the low-frequency reflection module and the high-frequency reflection module is capable of operating independently, the signals of different frequency bands point to different directions, thereby further increasing the flexibility in use. 
     The above embodiments are merely preferred embodiments of the present invention, and all changes and modifications made to the patent scope of the present invention should be within the scope of the present invention.