Patent Publication Number: US-2015084829-A1

Title: Multiple antenna system for a wireless device

Description:
RELATED APPLICATION 
     This application claims priority to, and the benefit of the filing date of, U.S. Provisional Application No. 61/880,397, filed on Sep. 30, 2013, entitled “Multiple Antenna System For A Wireless Device” which is hereby incorporated into this document by reference. 
    
    
     DESCRIPTION OF THE RELATED ART 
     Electronic devices, such as portable communication devices, continue to diminish in size. All such portable communication devices use some type of antenna for transmitting and receiving communication signals. Antennas and antenna systems generally fall into two categories, directional antennas and non-directional (also referred to as omni-directional) antennas. As its name implies, a directional antenna is one that exhibits a radiation pattern that is stronger in one direction than in another. An omni-directional antenna is one that exhibits a radiation pattern that is substantially the same regardless of direction. In some operating circumstances, it may be desirable to employ an omni-directional antenna, while in other operating circumstances, it may be desirable to employ a directional antenna. 
     Integrating a directional antenna and an omni-directional antenna in a single wireless device poses challenges including antenna location, orientation, polarization, and other factors. Further, it is also challenging to integrate into a wireless device switching circuitry that can select between the two antennas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, like reference numerals refer to like parts throughout the various views unless otherwise indicated. For reference numerals with letter character designations such as “ 102   a”  or “ 102   b”,  the letter character designations may differentiate two like parts or elements present in the same figure. Letter character designations for reference numerals may be omitted when it is intended that a reference numeral encompass all parts having the same reference numeral in all figures. 
         FIG. 1  is a block diagram illustrating an embodiment of a multiple antenna system for a wireless device. 
         FIG. 2  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. 
         FIG. 3  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. 
         FIG. 4  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. 
         FIG. 5  is a block diagram showing an omni-directional antenna and a directional antenna located on a printed wiring board. 
         FIG. 6  is a diagram showing a surface of the PWB of  FIG. 5  on which the first antenna is formed. 
         FIG. 7  is a diagram showing a surface of the PWB of  FIG. 5  on which the second antenna is formed. 
         FIG. 8  is a dimensioned schematic diagram showing a surface of the PWB of  FIG. 5  on which the first antenna is formed. 
         FIG. 9  is a dimensioned schematic diagram showing a surface of the PWB of  FIG. 5  on which the second antenna is formed. 
         FIG. 10  is a block diagram illustrating an example of a wireless device in which the multiple antenna system for a wireless device can be implemented. 
         FIG. 11  is a flowchart describing the operation of an exemplary embodiment of the multiple antenna system for a wireless device. 
     
    
    
     DETAILED DESCRIPTION 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. 
     In this description, the term “application” may also include files having executable content, such as: object code, scripts, byte code, markup language files, and patches. In addition, an “application” referred to herein, may also include files that are not executable in nature, such as documents that may need to be opened or other data files that need to be accessed. 
     The term “content” may also include files having executable content, such as: object code, scripts, byte code, markup language files, and patches. In addition, “content” referred to herein, may also include files that are not executable in nature, such as documents that may need to be opened or other data files that need to be accessed. 
     As used in this description, the terms “component,” “database,” “module,” “system,” and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device may be a component. One or more components may reside within a process and/or thread of execution, and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components may execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal). 
     As used herein, the terms “transducer” and “transducer element” refer to an antenna element that can be stimulated with a feed current to radiate electromagnetic energy, and an antenna element that can receive electromagnetic energy and convert the received electromagnetic energy to a receive current that is applied to receive circuitry. 
     As used herein, the term “orthogonal” refers to lines, line segments, or electric fields that are perpendicular at their point of intersection. 
     As used here, the term “orthogonal electric fields” refers to the orientation of two electric fields that are perpendicular to each other. 
     As used herein, the term “dual polarization” refers to an antenna that generates two electric fields and that has two components that are orthogonal to each other. 
     As used herein, the term “linear polarization” refers to an electric field vector or magnetic field vector that travels along a given plane along the direction of propagation. The orientation of a linearly polarized electromagnetic wave is defined by the direction of the electric field vector. For example, if the electric field vector is vertical (alternately up and down as the wave travels) the radiation is said to be vertically polarized. 
     As used herein, the term “circular polarization” refers to an electric field vector that, at a given point in space, describes a circle as time progresses. If the wave is frozen in time, the electric field vector of the wave describes a helix along the direction of propagation. 
     As used herein, the term “directional antenna” is one that exhibits a radiation pattern that is stronger in one direction than in another. 
     As used herein, the term “omni-directional antenna” is one that exhibits a radiation pattern that is substantially the same regardless of direction. 
     The multiple antenna system for a wireless device includes an omni-directional antenna and a directional antenna, and can be incorporated into or used with a communication device, such as, but not limited to, a wireless device referred to as an industrial fixed beacon (iFB), or another wireless device it which it is desirable to have both an omni-directional antenna and a directional antenna. 
       FIG. 1  is a block diagram illustrating an embodiment of a multiple antenna system for a wireless device. The multiple antenna system  100  comprises a first antenna  101 , a second antenna  103 , a switch  102  and a radio frequency (RF) circuit  104 . In this embodiment, the first antenna  101  can be an omni-directional antenna and the second antenna  103  can be a directional antenna. The switch  102  can be a mechanical switch that can be used to manually select between connecting the first antenna  101  to the RF circuit  104 , or connecting the second antenna  103  to the RF circuit  104 . 
       FIG. 2  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. The multiple antenna system  200  comprises a first antenna  201 , a second antenna  203 , a switch  202 , a radio frequency (RF) circuit  204 , and a controller  206 . In this embodiment, the first antenna  201  can be an omni-directional antenna and the second antenna  203  can be a directional antenna. The switch  202  can be a radio frequency (RF) switch that can be controlled by the controller  206  to automatically select between connecting the first antenna  201  to the RF circuit  204 , or connecting the second antenna  203  to the RF circuit  204  based on a number of different parameters or factors. 
       FIG. 3  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. The multiple antenna system  300  comprises a first antenna  301 , a second antenna  303 , a switch  302 , a radio frequency (RF) circuit  304 , a controller  306 , and a metal sensor  310 . In this embodiment, the first antenna  301  can be an omni-directional antenna and the second antenna  303  can be a directional antenna. The switch  302  can be a radio frequency (RF) switch that can be controlled by the controller  306  to automatically select between connecting the first antenna  301  to the RF circuit  304 , or connecting the second antenna  303  to the RF circuit  304  based on a number of different parameters or factors. The metal sensor  310  can determine whether the multiple antenna system  300  is proximate to a metal or a metallic object, and influence the selection of the first antenna  301  or the second antenna  303  accordingly. For example, if the multiple antenna system  300  is not proximate to a metal or metallic object, it may be desirable to employ the first antenna  301 . However, if the metal sensor  310  determines that the multiple antenna system  300  is proximate to a metal or a metallic object, then it may be desirable to employ the second antenna  303 . An example of a metal sensor  310  can be circuitry that senses the antenna impedance between the first antenna  301  and the RF circuit  304 , and/or the antenna impedance between the second antenna  303  and the RF circuit  304 . The antenna impedance between the first antenna  301  and the RF circuit  304 , and/or the antenna impedance between the second antenna  303  and the RF circuit  304  can be an indicator of whether the multiple antenna system  300  is proximate to a metal or a metallic object. When the antenna is close to a metal object, the metal object will introduce more capacitive coupling to the antenna so that the antenna impedance in the presence of the metal object will have more capacitive reactance (e.g., a greater negative of the imaginary part of the impedance). Those skilled in the art will understand that detecting the impedance can be done using a variety of techniques. 
       FIG. 4  is a block diagram illustrating an alternative embodiment of a multiple antenna system for a wireless device. The multiple antenna system  400  comprises a first antenna  401 , a second antenna  403 , a power combiner/splitter  402 , and a radio frequency (RF) circuit  404 . In this embodiment, the first antenna  401  can be an omni-directional antenna and the second antenna  403  can be a directional antenna. The power combiner/splitter  402  can be used to distribute power between both the first antenna  401 , the second antenna  403  and the RF circuit  404  in a way that allows each of the first antenna  401  and the second antenna  403  to operate simultaneously. 
       FIG. 5  is a block diagram showing an omni-directional antenna and a directional antenna located on a printed wiring board (PWB). In  FIG. 5 , a printed wiring board  502  includes a surface  505  having a ground plane  504 . A first antenna  501  is formed on the surface  505  in the form of a dipole antenna having elements  521  and  522 . A second antenna  503  is formed on a surface  507  of the PWB  502  opposite the surface  505  and, in an embodiment, comprises a patch antenna. Both the first antenna  501  and the second antenna  503  can be printed onto one or more surfaces of the PWB  502 . 
     The elements  521  and  522  of the first antenna  501  are located close to the edge of the PWB  502  and form “slots”  510   a  and  510   b  located between the elements  521  and  522  and the ground plane  504 . The slots  510   a  and  510   b  allow the first antenna to operate in what is referred to as a “slot mode.” The first antenna is generally referred to as being “linearly polarized.” However, the “slot mode” operation allowed due to the configuration of the first antenna  501  relative to the ground plane  504  allows the first antenna to exhibit “circular polarization” characteristics, and is considered to be “circularly polarized.” The circular polarization is created when the dipole elements  521  and  522  generate the polarization of the electric field in the axis that is parallel to the orientation of the dipole elements  521  and  522 , in this case, it is in the X axis, illustrated using reference numeral  535 . Then the slot mode generates the polarization of the electric field in the axis that is vertical to the slot orientation, in this case it is on the Y axis, which is the axis on which the centerline  515  lies. As a result, the two components of the electric field are orthogonal to each other, resulting in the circular polarization. A stepped impedance matching feature  524 , which can appear as a “zigzag” feature of the dipole element  522  is also used to control the axial ratio, which is a factor that determines the extent of the circular polarization. The first antenna  501  includes a feed  513  located near the line  515  approximately as shown. 
     The second antenna  503  is “circularly polarized” and includes a feed  512  also located near the line  515  approximately as shown. Locating the feed  513  of the first antenna  501  and the feed  512  of the second antenna  503  close to each other and close to the line  515  minimizes antenna coupling between the first antenna  501  and the second antenna  503 . In an embodiment, the distance between the feed  512  and the feed  513  can be approximately  10  millimeters (mm) to 25 mm. 
     The first antenna  501  and the second antenna  503  are also formed so as to have respective major surfaces that reside in the same plane, which is also the plane having the major surface of the ground plane  504 . 
       FIG. 6  is a diagram showing a surface of the PWB of  FIG. 5  on which the first antenna is formed. In an embodiment, the first antenna  601  is printed on the surface  605  of the PWB  602 . Components that comprise a controller  625  can also be located on the surface  605  of the PWB  602 . 
       FIG. 7  is a diagram showing a surface of the PWB of  FIG. 5  on which the second antenna is formed. In an embodiment, the second antenna  703  is printed on the surface  707  of the PWB  702 . The surface  707  is opposite the surface  605  shown in  FIG. 6 . 
       FIG. 8  is a dimensioned schematic diagram showing a surface of the PWB of  FIG. 5  on which the first antenna is formed. In an embodiment, the first antenna  801  is printed on the surface  805  of the PWB  802 . Components that comprise a controller  825  can also be located in the surface  805  of the PWB  802 . The second antenna  803  is illustrated in dotted line to indicate that it is located on a surface opposite the surface  805 . 
     The elements  821  and  822  of the first antenna  801  are located close to the edge of the PWB  802  and form “slots”  810   a  and  810   b  located between the elements  821  and  822  and the ground plane  804 . The slots  810   a  and  810   b  allow the first antenna  801  to operate in what is referred to as a “slot mode.” The first antenna is referred to as being “circularly polarized.” As mentioned above, the circular polarization of the first antenna  801  results from the combination of the slot mode and the ordinary linear polarization of the dipole mode. The circular polarization of the first antenna  801  results from the ordinary single element dipole antenna combined with the hidden “slot mode” operation resulting from the slots  810   a  and  810   b.  The circular polarization of the first antenna  801  is created by the orthogonality between the electric field from the slots  810   a  and  810   b  and the electric field from the dipole elements  821  and  822 . 
     The first antenna  801  also includes an impedance matching feature  824 . In an embodiment the impedance matching feature  824  comprises a “meander” “stepped” or a “zig-zag” structure, which performs antenna impedance matching by creating capacitive and inductive coupling. Controlling the capacitive and inductive coupling for the first antenna  801  allows effective impedance matching for the first antenna  801 . The meander pattern of the impedance matching feature  824  contributes to impedance matching because the meander pattern behaves as an inductor, while the gap between the impedance matching feature  824  and the other dipole element  822 ; and the gap between the impedance matching feature  824  and the ground plane  804  will behave as a capacitor. 
     Further, the impedance matching feature  824  also influences, to some extent, the axial ratio, which is a factor that determines the degree of circular polarization. The axial ratio depends, at least in part, on the size of the ground plane and the slot gap distance defined between the lower edge of the dipole elements  821  and  822  and the upper edge of the ground plane  804 , which in an exemplary embodiment, can be 2.8 mm In an exemplary embodiment, the impedance matching feature  824  will connect directly to a radio frequency(RF) front end circuit in the controller  825  over, for example, connection  823 , and the dipole element  822  will connect directly to the ground plane  804 . 
     The dimensions shown in  FIG. 8  are all in millimeters (mm) and are exemplary for a particular embodiment. The second antenna  803  is shown in phantom in  FIG. 8  for reference. 
       FIG. 9  is a dimensioned schematic diagram showing a surface of the PWB of  FIG. 5  on which the second antenna is formed. In an embodiment, the second antenna  903  is printed on the surface  907  of the PWB  902 . 
     The second antenna  903  is printed as shown and is configured to be “circularly polarized.” The dimensions shown in  FIG. 9  are all in millimeters (mm) and are exemplary for a particular embodiment. The first antenna  901  is shown in phantom for reference. 
       FIG. 10  is a block diagram illustrating an example of a wireless device  1000  in which the multiple antenna system for a wireless device can be implemented. In an embodiment, the wireless device  1000  can be a “Bluetooth” wireless communication device, a portable cellular telephone, a WiFi enabled communication device, or can be any other communication device. Embodiments of the multiple antenna system for a wireless device can be implemented in any communication device. The wireless device  1000  illustrated in  FIG. 10  is intended to be a simplified example of an iFB device and to illustrate one of many possible applications in which the multiple antenna system for a wireless device can be implemented. One having ordinary skill in the art will understand the operation of a portable wireless device, and, as such, implementation details are omitted. In an embodiment, the wireless device  1000  includes a baseband subsystem  1010  and an RF subsystem  1020  connected together over a system bus  1032 . The system bus  1032  can comprise physical and logical connections that couple the above-described elements together and enable their interoperability. In an embodiment, the RF subsystem  1020  can be a wireless transceiver. Although details are not shown for clarity, the RF subsystem  1020  generally includes a transmit module  1030  having modulation, upconversion and amplification circuitry for preparing and transmitting a baseband information signal, includes a receive module  1040  having amplification, filtering and downconversion circuitry for receiving and downconverting an RF signal to a baseband information signal to recover data, and includes a front end module (FEM)  1050  that includes diplexer circuitry, duplexer circuitry, or any other circuitry that can separate a transmit signal from a receive signal, as known to those skilled in the art. The front end module  1050  also comprises a switch  1055  configured to couple any of a first antenna  1060  and a second antenna  1065  to the FEM  1050 . In an exemplary embodiment, the first antenna  1060  can be an omni-directional antenna and the second antenna  1065  can be a directional antenna. The switch  1055  can comprise any of a mechanical switch, a radio frequency (RF) switch, or any other switch that can select any of the first antenna  1060  and the second antenna  1065 . The first antenna  1060 , the second antenna  1065  and at least a portion of the RF subsystem  1020  can comprise any of the embodiments of the multiple antenna system for a wireless device as described herein. When implemented as shown in  FIG. 10 , the multiple antenna system for a wireless device can be implemented as part of one or more modules that comprise the RF subsystem  1020 . 
     The baseband subsystem  1010  generally includes a processor  1002 , which can be a general purpose or special purpose microprocessor, memory  1014 , application software  1004 , analog circuit elements  1006 , and digital circuit elements  1008 , coupled over a system bus  1012 . The system bus  1012  can comprise the physical and logical connections to couple the above-described elements together and enable their interoperability. 
     An input/output (I/O) element  1016  is connected to the baseband subsystem  1010  over connection  1024  and a memory element  1018  is coupled to the baseband subsystem  1010  over connection  1026 . The I/O element  1016  can include, for example, a microphone, a keypad, a speaker, a pointing device, user interface control elements, and any other devices or system that allow a user to provide input commands and receive outputs from the wireless device  1000 . 
     The memory  1018  can be any type of volatile or non-volatile memory, and in an embodiment, can include flash memory. The memory  1018  can be permanently installed in the wireless device  1000 , or can be a removable memory element, such as a removable memory card. 
     The wireless device  1000  may also include a metal sensor  1022  coupled to the baseband subsystem  1010  over connection  1028 . The metal sensor  1022  can detect the presence of metal or metallic objects in the vicinity of the wireless device  1000  and cause the wireless device  1000  to use one or more of the exemplary embodiments of the directional antenna and the omni-directional antenna described herein. For example, the metal sensor  1022  may provide an impedance measurement that can be interpreted by the processor  1002 , which can then control the front end module  1050  to select any of the first antenna  1060  and the second antenna  1065  in response to the signal from the metal sensor  1022 . The processor  1002 , the memory  1014  and the application software  1004  may comprise a controller  1025 , or perform a controller function to control the switch  1055  to select the appropriate antenna based on location, operating conditions, or other factors. 
     The processor  1002  can be any processor that executes the application software  1004  to control the operation and functionality of the wireless device  1000 . The memory  1014  can be volatile or non-volatile memory, and in an embodiment, can be non-volatile memory that stores the application software  1004 . 
     The analog circuitry  1006  and the digital circuitry  1008  include the signal processing, signal conversion, and logic that convert an input signal provided by the I/O element  1016  to an information signal that is to be transmitted. Similarly, the analog circuitry  1006  and the digital circuitry  1008  include the signal processing elements used to generate an information signal that contains recovered information from a received signal. The digital circuitry  1008  can include, for example, a digital signal processor (DSP), a field programmable gate array (FPGA), or any other processing device. Because the baseband subsystem  1010  includes both analog and digital elements, it can be referred to as a mixed signal device (MSD). 
       FIG. 11  is a flowchart  1100  describing the operation of an exemplary embodiment of the multiple antenna system for a wireless device. The blocks in the flowchart  1100  can be performed in or out of the order shown. 
     In block  1102 , a wireless device  1000  is located in a particular area. In block  1104 , the metal sensor  1022  in the wireless device  1000  determines whether the wireless device  1000  is located in the vicinity of metal or metallic object. 
     If in block  1104  the metal sensor  1022  in the wireless device  1000  determines that the wireless device  1000  is not located in the vicinity of metal or metallic object, then in block  1106 , the controller  1025  causes the switch  1055  to select the first antenna  1060  and operates in an omni-directional mode. 
     If in block  1104  the metal sensor  1022  in the wireless device  1000  determines that the wireless device  1000  is located in the vicinity of metal or metallic object, then in block  1108 , the controller  1025  causes the switch  1055  to select the second antenna  1065  and operates in a directional mode as a result of the wireless device  1000  being located in the presence of metal. 
     Although selected aspects have been illustrated and described in detail, it will be understood that various substitutions and alterations may be made therein without departing from the spirit and scope of the present invention, as defined by the following claims.