Patent Publication Number: US-10312591-B2

Title: Wireless communication device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 106106781, filed on Mar. 2, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a wireless communication device and, in particular, to a wireless communication device including multiple antennas. 
     2. Description of the Prior Art 
     In a conventional wireless communication device including multiple antennas, transmission lines are commonly used to connect a plurality of wireless communication components to the antennas to transmit electric signals therebetween. Therefore, a larger space is needed to accommodate multiple transmission lines, which is difficult for applications with compact form factors. Furthermore, the use of multiple transmission lines results in complicated wirings, larger power losses, lower heat dissipating capability and more electromagnetic interferences. To reduce the interference of the wireless signals in the same communication frequency band transmitted by adjacent antennas, conventionally co-existence and time-sharing techniques are used to share the CPU time slots among multiple wireless communication components and multiple antennas when transmitting wireless signals by multiple antennas. However, such techniques reduce the performance of the antennas transmitting wireless signals. 
     Therefore, for a wireless communication device including multiple antennas, how to improve the isolation between antennas and heat dissipating capability is an important issue. 
     SUMMARY OF THE INVENTION 
     The invention provides a wireless communication device, including a metallic housing, a circuit board, a metallic heat sink, a first antenna, a second antenna and a third antenna. The metallic housing includes a chamber. The circuit board is disposed in the chamber and is for providing a feed signal and a ground. The metallic heat sink is disposed on the circuit board and divides the chamber into a first region and a second region. The first antenna is disposed at the first region along a first direction. The second antenna is disposed at the second region along a second direction, wherein the second direction is perpendicular to the first direction. The third antenna is disposed at the second region along the first direction and located between the metallic heat sink and the second antenna. The first antenna, the second antenna and the third antenna are coupled with the circuit board, wherein the first antenna, the second antenna and the third antenna receive the feed signal and at least are capable of generating signals at the same frequency band. 
     In one embodiment of the invention, the circuit board includes a first ground point and a second ground point. The first ground point and the second ground point are located at a central region of the circuit board, and the circuit board is connected with the metallic housing via the first ground point and the second ground point. 
     In one embodiment of the invention, the circuit board further includes a third ground point and a fourth ground point. The third ground point and the fourth ground point are located between the first antenna and the metallic heat sink, and the circuit board is connected with the metallic housing via the third ground point and the fourth ground point. 
     In one embodiment of the invention, the first antenna includes a first feed terminal and a first ground terminal, the direction of the line connecting the first feed terminal and the first ground terminal is parallel to the first direction, and the first feed terminal is coupled with the circuit board to receive the feed signal. The second antenna includes a second feed terminal and a second ground terminal, the direction of the line connecting the second feed terminal and the second ground terminal is parallel to the second direction, and the second feed terminal is coupled with the circuit board to receive the feed signal. The third antenna includes a third feed terminal and a third ground terminal, the direction of the line connecting the third feed terminal and the third ground terminal is parallel to the first direction, and the third feed terminal is coupled with the circuit board to receive the feed signal. 
     In one embodiment of the invention, the circuit board further includes a coaxial transmission line. The coaxial transmission line includes a positive terminal and a negative terminal. The first feed terminal, the second feed terminal and the third feed terminal are electrically connected with the positive terminal of the coaxial transmission to receive the feed signal. The first ground terminal, the second ground terminal and the third ground terminal are connected with the negative terminal of the coaxial transmission line to ground. 
     In one embodiment of the invention, the first antenna is a quarter-wavelength planar inverted-F antenna, the second antenna is a quarter-wavelength planar inverted-F antenna, and the third antenna is a half-wavelength loop antenna. 
     In one embodiment of the invention, the first antenna receives the feed signal to provide a signal at a low frequency band and a signal at a high frequency band, the second antenna receives the feed signal to provide a signal at the low frequency band and a signal at the high frequency band, and the third antenna receives the feed signal to provide a signal at the low frequency band. 
     In one embodiment of the invention, the low frequency band provided by the first antenna is a Bluetooth frequency band at 2.4 GHz and a Wi-Fi frequency band at 2.4 GHz, and the high frequency band provided by the first antenna is a Wi-Fi frequency band at 5 GHz. The low frequency band provided by the second antenna is a Wi-Fi frequency band at 2.4 GHz, and the high frequency band provided by the second antenna is a Wi-Fi frequency band at 5 GHz. The low frequency band provided by the third antenna is a Zigbee frequency band at 2.4 GHz. 
     To sum up, regarding the wireless communication device including multiple antennas, the invention can improve the isolations between multiple antennas and the heat dissipating capability effectively. 
     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 
         FIG. 1  is a top view of the wireless communication device according to an embodiment of the invention. 
         FIG. 2  is a side view of the wireless communication device according to an embodiment of the invention. 
         FIG. 3  is a schematic diagram showing the antenna isolation of the wireless communication device not including a metallic heat sink and ground points. 
         FIG. 4  is a schematic diagram showing the antenna isolation of the wireless communication device according to an embodiment of the invention. 
         FIG. 5  is a schematic diagram showing the VSWR (voltage standing wave ratio) of the wireless communication device according to an embodiment of the invention. 
         FIG. 6  is a schematic diagram showing the antenna efficiency of the wireless communication device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of the wireless communication device  100  according to an embodiment of the invention.  FIG. 2  is a side view of the wireless communication device  100  according to an embodiment of the invention. The wireless communication device  100  includes a first antenna  10 , a second antenna  20 , a third antenna  30 , a metallic heat sink  40 , a control button  50 , a battery  55 , a camera  60 , a circuit board  70 , a power adaptor board  80 , and a metallic housing  90 . The metallic housing  90  includes a chamber  901 . The first antenna  10 , the second antenna  20 , the third antenna  30 , the metallic heat sink  40 , the control button  50 , the battery  55 , the camera  60 , the circuit board  70 , and the power adaptor board  80  are all disposed in the chamber  901 . 
     The circuit board  70  is for providing a feed signal and a ground. The metallic heat sink  40  is disposed on the circuit board  70 , and divides the chamber  901  of the metallic housing  90  into two regions. In the present embodiment, the two regions can be a first region  9011  located on the right side of the metallic housing  90  and a second region  9012  on the left side of the metallic housing  90 . The first antenna  10  and the camera  60  are disposed at the first region  9011 , while the second antenna  20 , the third antenna  30 , the control button  50 , the battery  55  and the power adaptor board  80  are disposed at the second region  9012 . 
     The wireless communication device  100  of the embodiment includes a plurality of antennas. The first antenna  10  is disposed at the first region  9011  of the metallic housing  90  along a first direction D 1  and is coupled with the circuit board  70 . The second antenna  20  is disposed at the second region  9012  of the metallic housing  90  along a second direction D 2  and is coupled with the circuit board  70 , wherein the second direction D 2  is perpendicular to the first direction D 1 . The third antenna  30  is disposed at the second region  2012  of the metallic housing  90  along the first direction D 1  between the metallic heat sink  40  and the second antenna  20 , and is coupled with the circuit board  70 . The first antenna  10 , the second antenna  20  and the third antenna  30  receive the feed signal, and at least are capable of generating signals at the same frequency band. 
     The circuit board  70  includes four ground points C 1  to C 4 , and is connected to the metallic housing  90  via the ground points C 1  to C 4 . The ground points C 1  and C 2  are located at the central region of the circuit board  70 , and the ground points C 3  and C 4  are located on the circuit board  70  between the first antenna  10  and the metallic heat sink  40 , wherein the central region is located in the middle of the long side of the circuit board  70 . 
     The first antenna  10  includes a first feed terminal A 1  and a first ground terminal B 1 . The direction of the line connecting the first feed terminal A 1  and the first ground terminal B 1  is parallel to the first direction D 1 , and the first feed terminal A 1  is coupled with the circuit board  70  to receive the feed signal. The first antenna  10  receives the feed signal to provide a signal within a low frequency band and a signal within a high frequency band. In the present embodiment, the low frequency band provided by the first antenna  10  is a Bluetooth frequency band of 2.4 GHz and a Wi-Fi frequency band of 2.4 GHz, while the high frequency band provided by the first antenna  10  is a Wi-Fi frequency band of 5 GHz. This allows the first antenna  10  to transmit and receive signals of Bluetooth and Wi-Fi communication systems. In the present embodiment, the first antenna  10  is a Quarter-wavelength PIFA (Planar Inverted-F Antenna), which is the main antenna of the wireless communication device of the present embodiment. 
     The second antenna  20  includes a second feed terminal A 2  and a second ground terminal B 2 . The direction of the line connecting the second feed terminal A 2  and the second ground terminal B 2  is parallel to the second direction D 2 , and the second feed terminal A 2  is coupled with the circuit board  70  to receive the feed signal. The second antenna  20  receives the feed signal to provide a signal within a low frequency band and a signal within a high frequency band. In the present embodiment, the low frequency band provided by the second antenna  20  is a Wi-Fi frequency band of 2.4 GHz, while the high frequency band provided by the second antenna  20  is a Wi-Fi frequency band of 5 GHz. This allows the second antenna  20  to transmit and receive signals of the Wi-Fi communication system. In the present embodiment, the second antenna  20  is a Quarter-wavelength PIFA, which is an auxiliary antenna of the wireless communication device of the present embodiment. 
     The third antenna  30  includes a third feed terminal A 3  and a third ground terminal B 3 . The direction of the line connecting the third feed terminal A 3  and the third ground terminal B 3  is parallel to the first direction D 1 . Since the first direction D 1  is perpendicular to the second direction D 2 , the direction of the line connecting the third feed terminal A 3  and the third ground terminal B 3  is perpendicular to the direction of the line connecting the second feed terminal A 2  and the second ground terminal B 2 . 
     The third feed terminal A 3  is coupled with the circuit board  70  to receive the feed signal. The third antenna  30  receives the feed signal to provide a signal within a low frequency band. In the present embodiment, the low frequency band provided by the second antenna  20  is a Zigbee frequency band of 2.4 GHz, which allows the third antenna  30  to transmit and receive signals of the Zigbee wireless communication system. In the present embodiment, the first antenna  10  and the second antenna  20  are of the same antenna type, that is, the first antenna  10  and the second antenna  20  are both Quarter-wavelength PIFAs. The third antenna  30  is a half-wavelength loop antenna, and therefore the type of the third antenna  30  is different from the type of the first antenna  10  and the second antenna  20 . 
     The circuit board  70  further includes a coaxial transmission line (not shown in the drawing). The coaxial transmission line includes a positive terminal and a negative terminal. The first feed terminal A 1 , the second feed terminal A 2  and the third feed terminal A 3  are electrically connected with the positive terminal of the coaxial transmission line to receive the feed signal. The first ground terminal B 1 , the second ground terminal B 2  and the third ground terminal B 3  are electrically connected with the negative terminal of the coaxial transmission line to be connected with the circuit board  70  and a ground. 
     As shown in  FIG. 2 , the distance Xd from the first antenna  10 , the second antenna  20  and the third antenna  30  to the circuit board  70  is about 5.7 mm, and the first antenna  10  can be disposed at a location away from noise sources such as the battery  55  and the power adaptor board  80 . 
     In the present embodiment, since the size of the wireless communication device  100  is small, the heat dissipation capability can be improved by using the metallic heat sink  40  and the metallic housing  90  to dissipating heat and lowering the temperature. 
       FIG. 3  and  FIG. 4  show the isolations between the antennas of the wireless communication devices both having three antennas (that is, the first antenna  10 , the second antenna  20  and the third antenna  30 ) with and without the metallic heat sink  40  and the ground points C 1  to C 4 .  FIG. 3  is a schematic diagram showing the measured isolation of the wireless communication device including the first antenna  10 , the second antenna  20  and the third antenna  30  but not including the metallic heat sink  40  and the ground points C 1  to C 4 .  FIG. 4  is a schematic diagram showing the measured isolation of the wireless communication device  100  according to the embodiment of the invention including the first antenna  10 , the second antenna  20 , the third antenna  30 , the metallic heat sink  40  and the ground points C 1  to C 4 . In  FIG. 3  and  FIG. 4 , the vertical axis represents the isolation (in dB), and the horizontal axis represents the frequency (in MHz). 
     Please refer to  FIG. 3 , the curve X 1  represents the isolation between the first antenna  10  and the second antenna  20  under different frequencies, the curve X 2  represents the isolation between the first antenna  10  and the third antenna  30  under different frequencies, and the curve X 3  represents the isolation between the second antenna  20  and the third antenna  30  under different frequencies.  FIG. 3  shows that the isolations between the three antennas are all higher than −10 dB at the low frequency of 2.4 GHz, which means that the isolations between the three antennas are relatively poor. 
     Please refer to  FIG. 4 , the curve Yl represents the isolation between the first antenna  10  and the second antenna  20  in the wireless communication device  100  according to the embodiment of the invention under different frequencies, the curve Y 2  represents the isolation between the first antenna  10  and the third antenna  30  in the wireless communication device  100  according to the embodiment of the invention under different frequencies, and the curve Y 3  represents the isolation between the second antenna  20  and the third antenna  30  in the wireless communication device  100  according to the embodiment of the invention under different frequencies.  FIG. 4  shows that by disposing the metallic heat sink  40  and the ground points C 1  to C 4 , the isolations between the three antennas are all lower than −10 dB at the same frequency (that is, 2.4 GHz), which means that the isolations between the three antennas are good. 
       FIG. 5  is a schematic diagram showing the VSWR (voltage standing wave ratio) of the wireless communication device including three antennas (that is, the first antenna  10 , the second antenna  20  and the third antenna  30 ) with and without the metallic heat sink  40  and the ground points C 1  to C 4 . The curve VSWR 1  represents the measured VSWR of the wireless communication device including the first antenna  10 , the second antenna  20  and the third antenna  30  but not including the metallic heat sink  40  and the ground points C 1  to C 4 . The curve VSWR 2  represents the measured VSWR of the wireless communication device  100  according to the embodiment of the invention including the first antenna  10 , the second antenna  20 , the third antenna  30 , the metallic heat sink  40  and the ground points C 1  to C 4 . In  FIG. 5 , the vertical axis represents the VSWR, and the horizontal axis represents the frequency (in MHz). As shown in  FIG. 5 , by disposing the metallic heat sink  40  and the ground points C 1  to C 4 , the VSWR of the wireless communication device  100  according to the embodiment of the invention in the same frequency band is closer to the ideal value of 1, such that good matches between the three antennas can be achieved. 
       FIG. 6  is a schematic showing the antenna efficiency of the three antennas of the wireless communication device  100  according to the embodiment of the invention. The curve G 1  represents the antenna efficiency of the first antenna  10  at the Bluetooth/Wi-Fi frequency band of 2.4 GHz. The curve G 2  represents the antenna efficiency of the second antenna  20  at the Wi-Fi frequency band of 2.4 GHz. The curve G 3  represents the antenna efficiency of the third antenna  30  at the Zigbee frequency band of 2.4 GHz. The curve G 4  represents the antenna efficiency of the first antenna  10  at the Bluetooth/Wi-Fi frequency band of 5 GHz. The curve G 5  represents the antenna efficiency of the second antenna  20  at the Wi-Fi frequency band of 5 GHz. In  FIG. 6 , the vertical axis represents the antenna efficiency (in dB), and the horizontal axis represents the frequency (in MHz). 
     To sum up, in the wireless communication device including multiple antennas, disposing the metallic heat sink between the first antenna  10  and the third antenna  30  can effectively improve the isolation between the first antenna  10  and the third antenna  30 . Although the second antenna  20  and the third antenna  30  are both disposed at the second region  9012 , the interference between the two antennas can be avoided and the isolation between them can be improved by using different antenna types and disposing them perpendicularly to each other. Moreover, disposing the ground points C 1  to C 4  can eliminate the frequency band generated by resonance between the circuit board  70  and the metallic housing  90 . Therefore, the isolations between the three antennas can be improved. Furthermore, by disposing the metallic heat sink  40  and the metallic housing  90 , the heat dissipating capability of the wireless communication device  100  can also be improved to dissipate heat and reduce the temperature. Therefore, the invention can improve the isolations between multiple antennas and the heat dissipating capability effectively. 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention. 
     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.