Patent Publication Number: US-2010123550-A1

Title: Coaxial Antenna Connection

Description:
BACKGROUND  
     Many modern mobile devices use radio-frequency identification (“RFID”) transceivers for wireless communication for various purposes. Like other types of wireless transceivers, RFID transceivers are typically connected to an antenna for transmitting and receiving signals. For optimal performance, the cable used to connect an RFID transceiver to its corresponding antenna should be as short as possible. 
     SUMMARY OF THE INVENTION  
     The present invention relates to a device comprises an RFID transceiver disposed on a first side of a printed circuit board; an antenna disposed on a second side of the printed circuit board; and a cable passing through the printed circuit board, a first end of the cable being connected to the RFID transceiver, a second end of the cable being connected to the antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows an exemplary mobile device according to the present invention. 
         FIG. 2  shows an exemplary cable assembly according to the present invention. 
         FIG. 3  shows an alternate view of the exemplary cable assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION  
     The exemplary embodiments of the present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments describe mobile devices that minimize cable length and improve transceiver performance by routing a cable through a printed circuit board. 
     RFID is used by many mobile devices for various purposes, including identification, short-range communication, security/authentication, tracking/location, etc. An RFID subsystem may include an RFID transceiver (also referred to as a “tag”), an antenna to transmit and receive signals, a power source (e.g., a battery) for providing power to the transceiver, and a cable or series of cables for connecting the transceiver to the antenna. The cable may be, for example, a coaxial cable. 
     Mobile devices that employ RFID communication and include the above components, like most electronic devices, are typically built using one or more printed circuit boards (“PCB”). A PCB is used to support and electrically connect various components using conductive pathways etched into a non-conductive substrate. The PCB may be fixed with respect to a casing of a device, and other components may be fixed with respect to the PCB. 
     Because space is limited in mobile devices, components of a certain size or type may need to be located in a particular position within the device. For example, an antenna may be located near the exterior of a device in order to improve performance. Further, because of these space concerns, components that must be electrically coupled to one another may not necessarily be able to be located in close physical proximity to one another. In some situations, these spatial concerns may lead to electrically connected components being disposed on opposite sides of a PCB from one another. Commonly, these components may be the RFID transceiver and its corresponding antenna, as discussed above. Despite such placement remotely from one another, the cable used to connect a transceiver and its corresponding antenna is preferably as short as possible in order to prevent signal degradation. 
     Previously, such components have been electrically coupled to one another in one of two ways. In the first, a hole may be placed in the PCB and the cable may be routed through the hole. Alternately, the cable may be wrapped around the edge of the PCB. However, both of these methods have disadvantages. First, in either case, the cable must be tied down and contained with precision. If the cable position varies from one product to the next, the performance may vary correspondingly, such as due to interference from nearby components; such variability is undesirable. Second, placing a hole in the PCB adds complexity to the manufacturing process. Third, wrapping the cable around the PCB requires a longer cable, which is undesirable as described above. 
     The exemplary embodiments described herein thus avoid these issues by using a connection to send the signal through the PCB.  FIG. 1  illustrates a schematic view of an exemplary device  100 . Those of skill in the art will understand that the device  100  may include various components other than those shown here in describing the exemplary embodiments. The device  100  includes a PCB  110  that may provide a physical mounting point for various components as well as electrical connections as described above. Mounted to the PCB  110  is an RFID transceiver  120 , which may serve any of the various purposes described above as well as others not listed. The PCB  110  provides a structural location for the RFID transceiver  120  and also serves to connect the RFID transceiver  120  electrically to other components as will be described herein. 
     The device  100  includes a power source  130  (e.g., a disposable or rechargeable battery, line power, etc.) supplying power to the RFID transceiver  120  and other components of the device  100 . The power source  130  may be physically mounted to the PCB  110  or located elsewhere, but electrical connections to the power source  130  are typically accomplished via the PCB  110 . The device  100  further includes a signal source  140  (e.g., a processor, etc.) that may handle data communications with the RFID transceiver  120 ; those of skill in the art will understand that the signal source  140  may also perform other tasks. As for the power source  130 , the signal source  140  may be attached to the PCB  110  or located elsewhere, but its electrical connections are accomplished via the PCB  110 . 
     The RFID transceiver  120  accomplishes its wireless communication by means of an antenna  150 . The antenna  150  may be of any type suitable for performing this communication. The RFID transceiver  120  is connected to the antenna  150  by means of an antenna cable assembly  160 , which will be discussed in more detail below. The antenna cable assembly  160  is typically a coaxial cable including an inner conductor for carrying a signal and an outer conductor for providing electromagnetic shielding, separated from one another by an insulating layer. With the exception of the antenna  150 , all components of the device  100  are typically located within a housing  170 ; the antenna may optionally be located outside the housing, partially within and partially without, or be integrated with the housing. 
       FIG. 2  shows an enlarged cutaway view of an exemplary antenna cable assembly  160  (also referred to herein as “assembly  160 ”). The assembly  160  includes a center lead  161  (e.g., the inner conductor of the coaxial cable) conveying a signal to and from the RFID transceiver  120 . The center lead  161  is typically connected to the RFID transceiver  120  by a soldered connection. The center lead  161  joins a center pin  162 , which runs through the PCB  110  and carries the same signal as the center lead  161 . The center pin  162  then joins the center conductor of a coaxial cable assembly  163  that is disposed on the same side of the PCB  110  as the antenna  150 , which connects to the antenna  150  and completes the signal pathway. The coaxial cable assembly  163  may be, for example, a standard L-shaped coaxial cable terminator attached to a coaxial cable. 
     The center pin  162  is shielded by an outer shell  164  in the manner described above with reference to the outer conductor of a typical coaxial cable. The outer shell  164  is mounted in a plated hole in the PCB  110 , preferably by soldering, and is thus grounded and shields the signal in the center pin  162 . In one exemplary embodiment, the outer shell  164  may be a MIL-STD-348A plug; in another, it may be a 50 ohm U.FL connector. The center lead  161  and the center pin  162  are separated from the outer shell by insulators  165  and  166 , which may be made from plastic or any other suitable insulating material. In other embodiments, insulators  165  and  166  may be formed as a single part. The insulator  166  joins the insulator (not shown) of the coaxial cable assembly  163 , insuring full signal isolation. It should be noted that the illustration of the coaxial cable assembly  163  in  FIG. 2  is truncated for clarity and that the assembly  163  extends sufficiently far to connect to the antenna  150 . 
       FIG. 3  shows an alternate view of the exemplary antenna cable assembly  160 , omitting the PCB  110  for clarity. As can be seen, the signal-carrying center pin  162  is shielded while it passes through the PCB  110  in order to avoid signal interference or unwanted electrical contacts. As stated above, the coaxial cable assembly  163  may extend away from the antenna cable assembly  160  to join antenna  150  (not shown in  FIG. 3 ). The insulator  165  is shown as conforming to the profile of the upper portion of the outer shell  164 ; however, those of skill in the art will understand that the precise shape of the insulator  165  may vary, and that other profiles that are still sufficient to insulate the center lead  161  from the outer shell  164  are also possible. In one such alternative embodiment, the insulator  165  may completely cover the upper portion of the outer shell  164  and contact the PCB  110  on all sides. Further, though the center pin  162  is shown as projecting above the center lead  161 , in other embodiments the top of the center pin  162  may be flush with the center lead  161 ; alternately, the center pin  162  may be formed integrally with the center lead  161 . 
     Thus, in the above-described exemplary embodiments, the antenna cable is restrained in a fixed position in order to achieve constant, predictable performance. Further, the length of cable required to connect a transceiver on one side of a PCB to an antenna on the other side may be minimized. Additionally, the cable may be shielded from interference while it passes through the PCB. 
     It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.