Patent Publication Number: US-9847613-B2

Title: Connector and contact

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional application of U.S. patent application Ser. No. 14/693,237 filed on Apr. 22, 2015 and is based upon and claims the benefit of priority of Japanese Patent Application No. 2014-090558, filed on Apr. 24, 2014, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     An aspect of this disclosure relates to a connector and a contact. 
     2. Description of the Related Art 
     Japanese Laid-Open Patent Publication No. 2009-129863, for example, discloses a multipolar coaxial connector including a plug where multiple coaxial cables are bound together and a receptacle that is mounted on a board. The plug is connected to the receptacle by removably inserting the plug into the receptacle. 
     The plug includes a housing made of a resin and having an oblong fit hole in its front face in an insertion direction, and multiple pairs of signal terminal plates and GND terminal plates that are electrically connected to inner conductors and outer conductors of the corresponding coaxial cables. Each pair of the signal terminal plate and the GND terminal plate are disposed to face each other across the fit hole, and the multiple pairs of the signal terminal plates and the GND terminal plates are arranged in the length direction of the fit hole. 
     The receptacle includes an oblong columnar part that protrudes toward the plug and is to be inserted into the fit hole of the housing, and multiple pairs of signal spring terminals and GND spring terminals held on the columnar part. The pairs of the signal spring terminals and the GND spring terminals elastically contact the corresponding pairs of the signal terminal plates and the GND terminal plates from the side of the columnar part. 
     However, in the disclosed multipolar coaxial connector, the impedance of the signal terminal plates is not matched sufficiently with the impedance of the GND terminal plates. Therefore, with the disclosed multipolar coaxial connector, it may be difficult to transmit a signal in an impedance matched state. 
     SUMMARY OF THE INVENTION 
     In an aspect of this disclosure, there is provided a connector for connecting a signal line and a ground line formed on a board with a coaxial cable. The connector includes a housing to be attached to the board; a ground terminal including a ground base that is disposed in the housing, and a first ground connection part that extends from the ground base toward a first end of the housing and is to be connected to a ground line of the coaxial cable; and a signal terminal including a signal base that is held in the housing and is surrounded by the ground base while being insulated from the ground base, and a first signal connection part that extends from the signal base toward the first end of the housing and is to be connected to a signal line of the coaxial cable. The ground terminal and the signal terminal are configured to elastically bend at a second end of the housing when the housing is attached to the board and the ground terminal and the signal terminal are connected, respectively, to the ground line and the signal line of the board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are drawings illustrating connectors according to a first embodiment; 
         FIGS. 2A through 2D  are drawings illustrating a connector according to the first embodiment; 
         FIGS. 3A through 3E  are drawings illustrating a connector according to the first embodiment; 
         FIGS. 4A through 4E  are drawings illustrating a connector of an FPC assembly; 
         FIGS. 5A through 5D  are drawings illustrating a connector of an FPC assembly; 
         FIGS. 6A and 6B  are drawings illustrating a contact according to the first embodiment; 
         FIG. 7  is a perspective cut-away side view of a connector and a connector of an FPC assembly that are connected to each other; 
         FIGS. 8A and 8B  are drawings illustrating a contact according to the first embodiment; 
         FIG. 9  is a perspective cut-away side view of a connector and a connector of an FPC assembly that are connected to each other; 
         FIG. 10  is a drawing illustrating a coaxial pin of a connector; 
         FIG. 11  is a drawing illustrating a coaxial pin of a connector; 
         FIG. 12  is a drawing illustrating a variation of an FPC; 
         FIGS. 13A and 13B  are drawings illustrating connectors and a coaxial cable assembly; 
         FIG. 14  is a drawing illustrating a coaxial pin; 
         FIGS. 15A and 15B  are drawings illustrating a connector of a second embodiment disposed between a board and another connector; 
         FIGS. 16A through 16C  are drawings illustrating a connector according to the second embodiment; 
         FIGS. 17A through 17C  are drawings illustrating a contact according to the second embodiment; 
         FIG. 18  is a drawing illustrating a mechanism for pressing a contact against a board; and 
         FIG. 19  is a drawing illustrating a surface of a board. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention are described below with reference to the accompanying drawings. 
     First Embodiment 
       FIGS. 1A and 1B  are drawings illustrating connectors  100 A and  100 B according to a first embodiment. As illustrated by  FIG. 1A , the connector  100 A is attached to a board  300 A, and the connector  100 B is attached to a board  300 B. 
     Each of the boards  300 A and  300 B includes signal lines and ground lines. The characteristic impedance of the signal lines and the ground lines of the boards  300 A and  300 B is set at a predetermined value (e.g., 50Ω) to enable high-speed signal transmission at, for example, about 2.0 Gbps. 
     The signal lines and the ground lines of the boards  300 A and  300 B with such characteristic impedance may be implemented by microstrip lines or coplanar lines. The connector  100 A is connected to the signal lines and the ground lines of the board  300 A, and the connector  100 B is connected to the signal lines and the ground lines of the board  300 B. 
     A flexible printed circuit (FPC) assembly  400  includes connectors  410 A and  410 B and a pair of FPCs  420 . Each of the FPCs  420  includes signal lines and ground lines. 
     The characteristic impedance of the signal lines and the ground lines of each FPC  420  is set at a predetermined value (e.g., 50Ω) to enable high-speed signal transmission at, for example, about 2.0 Gbps. The connector  410 A is connected to first ends of the FPCs  420 , and the connector  410 B is connected to second ends of the FPCs  420 . 
     In  FIG. 1B , the connectors  410 A and  410 B of the FPC assembly  400  are connected to the corresponding connectors  100 A and  100 B. 
       FIG. 2A  is a perspective view,  FIG. 2B  is a front view,  FIG. 2C  is a side view, and  FIG. 2D  is a plan view of the connector  100 A. 
     The connector  100 A is formed by fitting forty-four contacts  120 A into the corresponding through holes of a housing  110 A. The connector  100 A also includes guide pins  111 A used when the housing  110 A is attached to the board  300 A (see  FIG. 1 ). The guide pins  111 A are screwed into nuts  112 A embedded in the housing  110 A. 
     Through holes corresponding to the guide pins  111 A are formed in the board  300 A. The guide pins  111 A of the housing  110 A are aligned with the through holes of the board  300 A, and the connector  100 A is attached to a surface of the board  300 A by screwing the guide pins  111 A into the through holes as illustrated in  FIG. 1A . For example, the guide pins  111 A may be comprised of a metal such as copper or nickel, or a resin. 
     The housing  110 A may be comprised of an insulating material such as an epoxy resin. The housing  110 A has a cuboid shape. Forty-four through holes for inserting forty-four contacts  120 A are formed in the housing  110 A. 
     Each contact  120 A includes a first end and a second end, and extends in a direction that is substantially perpendicular to a surface of the board  300 A (see  FIGS. 1A and 1B ). The contacts  120 A may be comprised of, for example, a metal such as copper or nickel. 
     The first ends of the contacts  120 A are illustrated in  FIGS. 2A and 2B , and the second ends of the contacts  120 A are illustrated in  FIG. 2D . The first ends of the contacts  120 A face a direction that is perpendicular to and away from a surface of the board  300 A, and the second ends of the contacts  120 A face an opposite direction, i.e., face the surface of the board  300 A. The first ends of the contacts  120 A are connected to the connector  410 A of the FPC assembly  400 , and the second ends of the contacts  120 A are connected to the signal lines and the ground lines of the board  300 A. In  FIGS. 1A and 1B , the signal lines and the ground lines of the board  300 A are omitted. 
       FIG. 3A  is a perspective view illustrating two (a pair of) connectors  100 B attached to the board  300 B.  FIG. 3B  is a perspective view of one of the two connectors  100 B.  FIG. 3C  is a front view,  FIG. 3D  is a side view, and  FIG. 3E  is a plan view of the connectors  100 B. 
     As illustrated by  FIG. 3A , the pair of connectors  100 B are attached to the corresponding surfaces of the board  300 B along an edge of the board  300 B. The pair of connectors  100 B are disposed along an edge of the board  300 B and fixed to the corresponding surfaces of the board  300 B with a pair of screws  502  such that the board  300 B is sandwiched by the connectors  100 B. Through holes corresponding to the screws  502  are formed in the board  300 B. The screws  502  are screwed into the through holes in opposite directions from each other. 
     As illustrated by  FIGS. 3A, 3B, and 3C , each connector  100 B is formed by fitting forty-four contacts  120 B into the corresponding forty-four through holes of a housing  110 B. Each contact  120 B includes a first end and a second end, and extends along the corresponding surface of the board  300 B. The contacts  120 B may be comprised of, for example, a metal such as copper or nickel. 
     The housing  110 B may be comprised of an insulating material such as an epoxy resin. The housing  110 B has a cuboid shape. Forty-four through holes for inserting forty-four contacts  120 B are formed in the housing  110 B. 
     The first ends of the contacts  120 B are illustrated in  FIGS. 3A through 3C , and the second ends of the contacts  120 B are illustrated in  FIG. 3E . The first ends of the contacts  120 B face outside of the board  300 B in plan view, and the second ends of the contacts  120 B face an opposite direction i.e., face a central portion of the board  300 B in plan view. The first ends of the contact  120 B are connected to the connector  410 B of the FPC assembly  400 , and the second ends of the contact  120 B are connected to the signal lines and the ground lines of the board  300 B. In  FIGS. 1A, 1B, 3A, and 3E , the signal lines and the ground lines of the board  300 B are omitted. 
     The housing  110 B includes a pair of guide pins  111 B. The guide pins  111 B protrude from the housing  110 B in the same direction that the first ends of the contacts  120 B face, and guide the connector  410 B of the FPC assembly  400  when the connector  410 B is connected to the connector  100 B. For example, the guide pins  111 B may be comprised of a metal such as copper or nickel, or a resin. 
       FIG. 4A  is a front view,  FIG. 4B  is a side view, and  FIG. 4C  is a plan view of the connector  410 A of the FPC assembly  400  to which the connector  100 A is to be connected.  FIG. 4D  is a perspective view illustrating the connector  410 A attached to a metal plate  503 .  FIG. 4E  illustrates the metal plate  503 . 
     The connector  410 A includes a housing  411 A, coaxial pins  412 A, and guide pins  413 A. The coaxial pins  412 A are used for the connector  410 A to reduce reflection and transmission loss of a signal transmitted between the FPCs  420  and the board  300 A and to improve signal transmission characteristics. 
     The coaxial pins  412 A are fitted into the corresponding forty-four through holes of the housing  411 A. First ends of the coaxial pins  412 A are illustrated in  FIGS. 4A and 4D , and are to be connected to the first ends of the contacts  120 A of the connector  100 A. Second ends of the coaxial pins  412 A are illustrated in  FIG. 4C , and are to be connected to the signal lines and the ground lines of the FPCs  420  (see  FIGS. 1A and 1B ). The coaxial pins  412 A may be comprised of, for example, a metal such as copper or nickel. 
     The guide pins  413 A are screwed into the housing  411 A. The housing  411 A is fixed to the metal plate  503  by inserting the housing  411 A into an opening  503 A of the metal plate  503  illustrated in  FIG. 4E , and by screwing the guide pins  413 A into the housing  411 A from above as illustrated in  FIG. 4D . 
     The guide pins  111 A of the connector  100 A are inserted into the guide pins  413 A to align the connector  100 A with the connector  410 A. For example, the guide pins  413 A may be comprised of a metal such as copper or nickel, or a resin. 
     A recessed part is formed at the bottom of each guide pin  413 A to accept the thickness of the metal plate  503  when the guide pin  413 A is screwed into the housing  411 A. The recessed part has a diameter that is smaller than the diameter of other parts of the guide pin  413 A. 
     The metal plate  503  is used when connecting the connector  100 A to the connector  410 A. For example, multiple connectors  410 A may be arranged on one metal plate  503  so that multiple connectors  100 A can be easily connected to the corresponding connectors  410 A. The metal plate  503  may be implemented by any plate-shaped part. For example, a plate made of a resin instead of a metal may be used in place of the metal plate  503 . 
       FIG. 5A  is a perspective view,  FIG. 5B  is a front view,  FIG. 5C  is a side view, and  FIG. 5D  is a plan view of the connector  410 B of the FPC assembly  400  to which the connector  100 B is to be connected. 
     The connector  410 B includes a housing  411 B, coaxial pins  412 B, and guide pins  413 B. The coaxial pins  412 B are used for the connector  410 B to reduce reflection and transmission loss of a signal transmitted between the FPCs  420  and the board  300 B and to improve signal transmission characteristics. 
     Twenty-two coaxial pins  412 B are fitted into the corresponding twenty-two through holes of the housing  411 B. Two connectors  410 B are used as a pair and connected to the FPCs  420 . 
     First ends of the coaxial pins  412 B are illustrated in  FIGS. 5A and 5B , and are to be connected to the first ends of the contacts  120 B of the connectors  100 B. Second ends of the coaxial pins  412 B are illustrated in  FIG. 5D , and are to be connected to the signal lines and the ground lines of the FPCs  420  (see  FIGS. 1A and 1B ). The coaxial pins  412 B may be comprised of, for example, a metal such as copper or nickel. 
     The guide pins  413 B are screwed into the housing  411 B. The guide pins  111 B of the connectors  100 B are inserted into the guide pins  413 B to align the connectors  100 B with the connectors  410 B. For example, the guide pins  413 B may be comprised of a metal such as copper or nickel, or a resin. 
     The pair of connectors  410 B are fixed to each other with two pairs of screws  504  and nuts  505 . The screws  504  are screwed into the connectors  410 B in opposite directions from each other. The screws  504  and the nuts  505  also fix holders  500  to the connectors  410 B. The holders  500  are used to fix the FPCs  420  to the connectors  410 B. 
     A recessed part similar to the recessed part of the guide pin  413 A of the connector  410 A is formed at the bottom of each guide pin  413 B. The recessed parts of the guide pins  413 B make it possible to fix multiple connectors  410 B to a metal plate similar to the metal plate  503  and to easily connect multiple connectors  100 B to the connectors  410 B. 
       FIG. 6A  is a perspective view and  FIG. 6B  is a side view of the contact  120 A of the first embodiment. 
     The contact  120 A includes a ground terminal  130 A and a signal terminal  140 A. The ground terminal  130 A includes a base  131 A, connection parts  132 A, and connection parts  133 A. 
     The base  131 A has a cylindrical shape, and the connection parts  132 A and  133 A are connected to the corresponding ends of the cylindrical base  131 A. A pair of slits  131 A 1  are formed in the base  131 A along the central axis of the cylindrical shape from the end to which the connection parts  132 A are connected. The slits  131 A 1  are formed to position the base  131 A relative to the housing  110 A, and to allow a part of the housing  110 A to enter the base  131 A and hold the signal terminal  140 A. 
     The connection parts  132 A are conductive parts extending from a first end of the base  131 A along the central axis of the cylindrical shape, and are connected to a ground terminal of the coaxial pin  412 A of the connector  410 A. The connection parts  132 A have a leaf spring structure configured such that a spring elastic force acts in a direction to reduce the distance between the connection parts  132 A when a ground terminal of the coaxial pin  412 A is inserted between the connection parts  132 A. 
     The connection parts  133 A are conductive parts extending from a second end of the base  131 A, and form a coplanar line together with a connection part  143 A of the signal terminal  140 A. That is, the connection parts  133 A implement ground lines of a coplanar line that are located on the sides of a signal line. For this reason, the connection parts  133 A curve along the connection part  143 A. 
     The connection parts  133 A have a leaf spring structure having spring elasticity. When the connection parts  133 A are pressed in a direction of the central axis of the base  131 A, ends of the connection parts  133 A are pressed against the corresponding ground lines of the board  300 A (see  FIGS. 1A and 1B ) by an elastic force. This leaf spring structure enables reliable electrical connection between the ends of the connection parts  133 A and the ground lines of the board  300 A. 
     The signal terminal  140 A includes a base  141 A and connection parts  142 A and  143 A. 
     The base  141 A is a narrow plate-like part disposed between the connection parts  142 A and the connection part  143 A. The connection parts  142 A and  143 A are connected to the corresponding ends of the base  141 A. The width and thickness of the base  141 A are set such that the base  141 A can be housed in the base  131 A. The base  141 A and the base  131 A are held by the housing  110 A such that the central axis of the base  141 A coincides with the central axis of the base  131 A. 
     The connection parts  142 A are conductive parts extending from a first end of the base  141 A along the central axis of the cylindrical shape, and are to be connected to a signal terminal of the coaxial pin  412 A of the connector  410 A. The connection parts  142 A are disposed inside of the connection parts  132 A of the ground terminal  130 A. The connection parts  142 A have a leaf spring structure configured such that a spring elastic force acts in a direction to reduce the distance between the connection parts  142 A when a signal terminal of the coaxial pin  412 A is inserted between the connection parts  142 A. 
     The connection part  143 A is a conductive part extending from a second end of the base  141 A. The connection part  143 A is disposed between the connection parts  133 A of the ground terminal  130 A, and forms a coplanar line together with the connection parts  133 A. That is, the connection part  143 A implements a signal line of a coplanar line that is located between ground lines of the coplanar line. For this reason, the connection part  143 A curves along the connection parts  133 A. 
     The connection part  143 A has a leaf spring structure having spring elasticity. When the connection part  143 A is pressed in a direction of the central axis of the base  131 A, an end of the connection part  143 A is pressed against the corresponding signal line of the board  300 A (see  FIGS. 1A and 1B ) by an elastic force. This leaf spring structure enables reliable electrical connection between the end of the connection part  143 A and the signal line of the board  300 A. 
     As described above, the contact  120 A includes the ground terminal  130 A and the signal terminal  140 A, and the base  141 A and the connection parts  142 A of the signal terminal  140 A are disposed inside of the base  131 A and the connection parts  132 A of the ground terminal  130 A, respectively. This configuration makes it possible to sufficiently match the impedance of the base  141 A and the connection parts  142 A with the impedance of the base  131 A and the connection parts  132 A, and makes it possible to reduce reflection and transmission loss of a signal and improve signal transmission characteristics. 
     Also, the connection part  143 A of the signal terminal  140 A and the connection parts  133 A of the ground terminal  130 A constitute a coplanar line. This configuration also makes it possible to reduce reflection and transmission loss of a signal and improve signal transmission characteristics. 
     Thus, the contact  120 A is configured to improve signal transmission characteristics between the board  300 A and the connector  410 A and achieve predetermined characteristic impedance (e.g., 50Ω). 
       FIG. 7  is a perspective cut-away side view of the connector  100 A and the connector  410 A of the FPC assembly  400  that are connected to each other. 
     As illustrated by  FIG. 7 , the base  131 A and the connection parts  132 A of the ground terminal  130 A are housed in a through hole  113 A of the housing  110 A, and the base  131 A is fixed by walls  114 A formed inside of the through hole  113 A. The walls  114 A are formed in the through hole  113 A to fix the base  131 A. 
     The base  141 A of the signal terminal  140 A is disposed inside of the walls  114 A and fixed to the housing  110 A by walls (not shown) similar to the walls  114 A. 
     A first end  412 AS 1  of a signal line  412 AS of the coaxial pin  412 A is fitted between the connection parts  142 A of the signal terminal  140 A. Also, a first end  412 AG 1  of a ground line  412 AG of the coaxial pin  412 A is fitted between the connection parts  132 A of the ground terminal  130 A. With this configuration, the connector  100 A and the connector  410 A are electrically connected to each other. The signal line  412 AS and the ground line  412 AG are insulated from each other with an insulator  412 AZ. The insulator  412 AZ also determines the relative positions of the signal line  412 AS and the ground line  412 AG. 
     The connection parts  133 A of the ground terminal  130 A and the connection part  143 A of the signal terminal  140 A are elastically bent (or biased) while they are connected, respectively, to the ground lines and the signal line of the board  300 A. This configuration makes it possible to electrically connect the connection parts  133 A and the connection part  143 A with the ground lines and the signal line of the board  300 A. 
     A second end  412 AS 2  of the signal line  412 AS and a second end  412 AG 2  of the ground line  412 AG of the coaxial pin  412 A are connected, respectively, to a signal line and ground lines of the FPC  420  of the FPC assembly  400 . 
     Connecting the connector  100 A and the connector  410 A with good characteristic impedance as illustrated in  FIG. 7  makes it possible to improve signal transmission characteristics between the board  300 A and the FPCs  420 . 
       FIG. 8A  is a perspective view and  FIG. 8B  is a side view of the contact  120 B of the first embodiment. 
     The contact  120 B includes a ground terminal  130 B and a signal terminal  140 B. The ground terminal  130 B includes a base  131 B and connection parts  132 B and  133 B. 
     The base  131 B has a cylindrical shape, and the connection parts  132 A and  133 A are connected to the corresponding ends of the base  131 B. Slits  131 B 1  are formed in the base  131 B along the central axis of the cylindrical shape from the end to which the connection parts  132 B are connected. The slits  131 B 1  are formed to position the base  131 B relative to the housing  110 B, and to allow a part of the housing  110 B to enter the base  131 B and hold the signal terminal  140 B. 
     The connection parts  132 B are conductive parts extending from a first end of the base  131 B along the central axis of the cylindrical shape, and are connected to a ground terminal of the coaxial pin  412 B of the connector  410 B. The connection parts  132 B have a leaf spring structure configured such that a spring elastic force acts in a direction to reduce the distance between the connection parts  132 B when a ground terminal of the coaxial pin  412 B is inserted between the connection parts  132 B. 
     The connection parts  133 A are conductive parts extending from a second end of the base  131 B, and form a coplanar line together with a connection part  143 B of the signal terminal  140 B. That is, the connection parts  133 B implement ground lines of a coplanar line that are located on the sides of a signal line. For this reason, the connection parts  133 B curve along the connection part  143 B. 
     The connection parts  133 B have a leaf spring structure having spring elasticity. When the connection parts  133 B are pressed in a direction that is substantially perpendicular to the central axis of the base  131 B, ends of the connection parts  133 B are pressed against the corresponding ground lines of the board  300 B (see  FIGS. 1A and 12 ) by an elastic force. This leaf spring structure enables reliable electrical connection between the connection parts  133 B and the ground lines of the board  300 B. The direction in which the connection parts  133 B are pressed is not limited to the direction that is substantially perpendicular to the central axis of the base  131 B, as long as the direction intersects with the central axis of the base  131 B. 
     The signal terminal  140 B includes a base  141 B and connection parts  142 B and  143 B. 
     The base  141 B is a narrow plate-like part disposed between the connection parts  142 B and the connection part  143 B. The connection parts  142 B and  143 B are connected to the corresponding ends of the base  141 B. The width and thickness of the base  141 B are set such that the base  141 B can be housed in the base  131 B. The base  141 B and the base  131 B are held by the housing  110 B such that the central axis of the base  141 B coincides with the central axis of the base  131 B. 
     The connection parts  142 B are conductive parts extending from a first end of the base  141 B along the central axis of the cylindrical shape, and are connected to a signal terminal of the coaxial pin  412 B of the connector  410 B. The connection parts  142 B are disposed inside of the connection parts  132 B of the ground terminal  130 B. The connection parts  142 B have a leaf spring structure configured such that a spring elastic force acts in a direction to reduce the distance between the connection parts  142 B when a signal terminal of the coaxial pin  412 B is inserted between the connection parts  142 B. 
     The connection part  143 B is a conductive part extending from a second end of the base  141 B. The connection part  143 B is disposed between the connection parts  133 B of the ground terminal  130 B, and forms a coplanar line together with the connection parts  133 B. That is, the connection part  143 B implements a signal line of a coplanar line that is located between ground lines the coplanar line. For this reason, the connection part  143 B curves along the connection parts  133 B. 
     The connection part  143 B has a leaf spring structure having spring elasticity. When the connection part  143 B is pressed in a direction that is substantially perpendicular to the central axis of the base  141 B, an end of the connection part  143 B is pressed against the corresponding signal line of the board  300 B (see  FIGS. 1A and 1B ) by an elastic force. This leaf spring structure enables reliable electrical connection between the connection part  143 B and the signal line of the board  300 B. The direction in which the connection part  143 B is pressed is not limited to the direction that is substantially perpendicular to the central axis of the base  141 B, as long as the direction intersects with the central axis of the base  141 B. 
     As described above, the contact  120 B includes the ground terminal  130 B and the signal terminal  140 B and has a configuration similar to the configuration of the contact  120 A. 
     Accordingly, the contact  120 B is configured to improve signal transmission characteristics between the board  300 B and the connector  410 B and achieve predetermined characteristic impedance (e.g., 50Ω). 
       FIG. 9  is a perspective cut-away side view of the connector  100 B and the connector  410 B of the FPC assembly  400  that are connected to each other. Although two connectors  100 B are fixed to an end of the board  300 B in  FIG. 9 , one of the connector  100 B is used for descriptions below because the two connectors  100 B have the same configuration. 
     As illustrated by  FIG. 9 , the base  131 B and the connection parts  132 B of the ground terminal  130 B are housed in a through hole  113 B of the housing  110 B, and the base  131 B is fixed by walls  114 B formed inside of the through hole  113 B. 
     The base  141 B of the signal terminal  140 B is disposed inside of the walls  114 B and fixed to the housing  110 B by walls (not shown) similar to the walls  114 B. 
     An end  412 BS 1  of a signal line  412 BS of the coaxial pin  412 B is fitted between the connection parts  142 B of the signal terminal  140 B. Also, an end  412 BG 1  of a ground line  412 BG of the coaxial pin  412 B is fitted between the connection parts  132 B of the ground terminal  130 B. With this configuration, the connector  100 B and the connector  410 B are electrically connected to each other. The signal line  412 BS and the ground line  412 BG are insulated from each other with an insulator  412 BZ. The insulator  412 BZ also determines the relative positions of the signal line  412 BS and the ground line  412 BG. 
     The connection parts  133 B of the ground terminal  130 B and the connection part  143 B of the signal terminal  140 B are elastically bent while they are connected, respectively, to the ground lines and the signal line of the board  300 B. This configuration makes it possible to electrically connect the connection parts  133 B and the connection part  143 B with the ground lines and the signal line of the board  300 B. 
     Another end  412 BS 2  of the signal line  412 BS and another end  412 BG 2  of the ground line  412 BG of the coaxial pin  412 B are connected, respectively, to a signal line and ground lines of the FPC  420  of the FPC assembly  400 . 
       FIGS. 10 and 11  are drawings illustrating the coaxial pin  412 A of the connector  410 A to be connected to the connector  100 A of the first embodiment. The coaxial pin  412 B of the connector  410 B to be connected to the connector  100 B has substantially the same configuration as the coaxial pin  412 A of the connector  410 A. Therefore, the following descriptions of the coaxial pin  412 A may also be applied to the coaxial pin  412 B. 
     The coaxial pin  412 A includes the signal line  412 AS, the ground line  412 AG, and the insulator  412 AZ. 
     The signal line  412 AS is disposed inside of the cylindrical ground line  412 AG and is held by the insulator  412 AZ coaxially with the ground line  412 AG. With this configuration, the first end  412 AS 1  of the signal line  412 AS and the first end  412 AG 1  of the ground line  412 AG are disposed coaxially with each other. Also, the second end  412 A 52  of the signal line  412 AS and the second end  412 AG 2  of the ground line  412 AG are also disposed coaxially with each other. 
     Slits are formed in the first end  412 AG 1  of the ground line  412 AG to implement a leaf spring structure. This leaf spring structure makes it easier to fit the connection parts  132 A of the connector  100 A into the ground line  412 AG. 
     Slits are also formed in the second end  412 AS 2  of the signal line  412 AS and the second end  412 AG 2  of the ground line  412 AG to provide them with leaf spring structures. The slits of the second end  412 AS 2  and the second end  412 AG 2  are formed at corresponding positions so that the FPC  420  can be inserted into the slits. 
     The second end  412 AS 2  of the signal line  412 AS is connected to a signal terminal  421  of the FPC  420 , and the second end  412 AG 2  of the ground line  412 AG is connected to ground lines  422  of the FPC  420 . 
     The reliability of electrical connection of the second end  412 AS 2  of the signal line  412 AS and the second end  412 AG 2  of the ground line  412 AG with the signal terminal  421  and the ground lines  422  of the FPC  420  can be improved by crimping or soldering them together after positioning and inserting the FPC  420  into the slits of the second end  412 AS 2  and the second end  412 AG 2 . For example, using pulse-heated solder for the soldering makes it possible to reduce assembly costs. 
     With the connector  100 A including the contacts  120 A and the connector  100 B including the contacts  120 B of the first embodiment, it is possible to connect the connector  100 A and the connector  410 A and connect the connector  100 B and the connector  410 B while achieving the impedance matching. 
     That is, the first embodiment makes it possible to connect the board  300 A and the FPCs  420  and connect the board  300 B and the FPCs  420  while achieving the impedance matching. 
     Thus, the first embodiment provides the connectors  100 A and  100 B and the contacts  120 A and  120 B that make it possible to transmit a signal in an impedance matched state. 
     In the above embodiment, each of the housings  110 A and  110 B has forty-four through holes  113 A or  113 B, and the contacts  120 A and  120 B are guided and held by the through holes  113 A and  113 B. 
     However, the housings  110 A and  110 B may have guide grooves instead of the through holes  113 A and  113 B, and the contacts  120 A and  120 B may be guided and held by the guide grooves of the housings  110 A and  110 B. The through holes  113 A and  113 B can be construed as covered grooves, and are therefore examples of guide grooves. 
     The FPC  420  may be modified as described below.  FIG. 12  is a drawing illustrating a variation of the FPC  420 . In  FIG. 12 , slits  420 A are formed in the FPC  420  such that multiple strips are joined at an end  420 B. In this case, signal lines and ground lines may be formed on the strips separated by the slits  420 A to form structures similar to microstrip lines or coplanar lines having predetermined characteristic impedance (e.g., 50Ω). 
     The first embodiment may also be modified to use a coaxial cable assembly instead of the FPC assembly  400 . 
       FIGS. 13A and 13B  are drawings illustrating a coaxial cable assembly  600  connected between the connectors  100 A and  100 A. 
     The coaxial cable assembly  600  includes connectors  410 A and  410 B and two coaxial cable bundles  620 . Each of the coaxial cable bundles  620  includes twenty-two sets of a signal line and a ground line, and the characteristic impedance of the signal line is set at a predetermined value (e.g., 50Ω). The connector  410 A is connected to first ends of the coaxial cable bundles  620 , and the connector  410 B is connected to second ends of the coaxial cable bundles  620 . 
     Thus, the coaxial cable assembly  600  is obtained by replacing the FPC  420  of the FPC assembly  400  of  FIGS. 1A and 1B  with the coaxial cable bundles  620 . Each of the coaxial cable bundles  620  is formed by binding twenty-two coaxial cables. 
     In  FIG. 13A , the connectors  410 A and  410 B of the coaxial cable assembly  600  are connected to the corresponding connectors  100 A and  100 B. 
     When the coaxial cable assembly  600  is used, each coaxial connector of the coaxial cable bundles  620  may be connected to the second end  412 AS 2  and the second end  412 AG 2  of the coaxial pin  412 A. Also, a coaxial pin  412 C illustrated by  FIG. 14  may instead be used for the connection. 
       FIG. 14  is a drawing illustrating the coaxial pin  412 C. The coaxial pin  412 C has a configuration that is obtained by replacing the second end  412 AS 2  and the second end  412 AG 2  of the coaxial pin  412 A with a second end  412 CS 2  and a second end  4120 G 2 . Accordingly, except for the second end  4120 S 2  and the second end  412 CG 2 , the configuration of the coaxial pin  412 C is substantially the same as the configuration of the coaxial pin  412 A of  FIG. 10 . 
     Unlike the second end  412 AS 2  and the second end  412 AG 2 , no slit is formed in the second end  412 CS 2  and the second end  412 CG 2 . The second end  4120 S 2  has a tubular shape so that a core wire  620 S of one of coaxial cables  620 A (see  FIG. 13 ) can be inserted into the second end  412 CS 2 . The second end  412 CG 2  also has a tubular shape such that a shielded line  620 G of the coaxial cable  620 A can be inserted into the second end  412 CG 2 . 
     Second Embodiment 
       FIG. 15A  illustrates a connector  200  of a second embodiment that is connected between the board  300 A and the connector  410 A.  FIG. 15B  illustrates the connector  200 , the board  300 A, and the connector  410 A that are separated from each other. 
     In  FIG. 15 , the connector  200  is used in place of the connector  100 A illustrated in  FIGS. 1A and 1B , and is connected between the board  300 A and the connector  410 A. However, the connector  200  may also be used in place of the connector  100 B and may be connected between the board  300 B and the connector  410 B. 
       FIG. 16A  is a perspective view and  FIG. 16B  is a perspective exploded view of the connector  200  of the second embodiment.  FIG. 16C  is an inverted view of  FIG. 16A . 
     The connector  200  includes a housing  210 , contacts  220 , and a bracket  230 . 
     The connector  200  is formed by fitting forty-four contacts  220  into the corresponding forty-four through holes of the housing  210  and the bracket  230 . 
     The housing  210  may be comprised of an insulating material such as an epoxy resin. The housing  210  has a cuboid shape. Forty-four through holes  210 A for inserting the forty-four contacts  220  are formed in the housing  210 . 
     The bracket  230  may be comprised of an insulating material such as an epoxy resin. The bracket  230  is a plate-like part having a rectangular shape in plan view. Forty-four through holes  230 A corresponding to the through holes  210 A of the housing  210  are formed in the bracket  230 . After the contacts  220  are inserted into the through holes  210 A of the housing  210 , the bracket  230  is attached to one side of the housing  210  to hold the contacts  220  in the through holes  210 A. 
       FIG. 17A  is a perspective view,  FIG. 17B  is a perspective exploded view, and  FIG. 17C  is a side view of the contact  220  of the second embodiment. 
     The contact  220  includes a ground terminal  221 , a signal terminal  222 , a spring  223 , and an insulator  224 . 
     The ground terminal  221  includes a base  221 A, a connection part  221 B, and a connection part  221 C. 
     The base  221 A has a cylindrical shape, and the connection parts  221 B and  221 C are connected to the corresponding ends of the base  221 A. A protrusion(s)  221 E is formed in an outer wall of the base  221 A by folding a part of the outer wall in a radial direction. Each of the connection parts  221 B and  221 C has a cylindrical shape, and has a configuration that looks like an extension of the base  221 A. 
     The connection part  221 B is a cylindrical conductive part extending from a first end of the base  221 A along the central axis of the cylindrical shape, and is connected to the ground terminal of the coaxial pin  412 A of the connector  410 A. 
     The connection part  221 C is a cylindrical conductive part extending from a second end of the base  221 A. Three protrusions  221 D are formed at an end of the connection part  221 C. The protrusions  221 D protrude in a direction of the central axis of the connection part  221 C, and are arranged at regular intervals along the circumference of the connection part  221 C in plan view. 
     The signal terminal  222  includes a base  222 A and connection parts  222 B and  222 C. 
     The base  222 A is a narrow plate-like part disposed between the connection parts  222 B and  222 C. The connection parts  222 B and  222 C are connected to the corresponding ends of the base  222 A. The width and thickness of the base  222 A are set such that the base  222 A can be placed in a through hole of the insulator  224  housed in the base  221 A. The base  222 A is held by the insulator  224  relative to the ground terminal  221  such that the central axis of the base  222 A coincides with the central axis of the base  221 A. 
     The connection parts  222 B are conductive parts extending from a first end of the base  222 A, and are to be connected to a signal terminal of the coaxial pin  412 A. The connection parts  222 B have a configuration similar to the configuration of the connection parts  142 A of the contact  120 A of the first embodiment. The connection parts  222 B have a leaf spring structure configured such that a spring elastic force acts in a direction to reduce the distance between the connection parts  222 B when the signal terminal of the coaxial pin  412 A is inserted between the connection parts  222 B. 
     The connection part  222 C is a narrow plate-like conductive part extending from a second end of the base  222 A. The connection part  222 C has a configuration that looks like an extension of the base  222 B. 
     The spring  223  has a helical shape and is disposed around the outer surface of the ground terminal  221 . The spring  223  engages with the protrusion  221 B formed in the outer wall of the ground terminal  221  that is inserted into the spring  223 . An upper end of the spring  223  in  FIG. 17C  engages with a step formed in the through hole  210 A of the housing  210 . With this configuration, the spring  223  presses the ground terminal  221  and the signal terminal  222  against the board  300 A. 
     The insulator  224  is housed in the base  221 A and holds the signal terminal  222  relative to the ground terminal  221 . By being held by the insulator  224  that engages with the inner wall of the base  221 A, the signal terminal  222  is positioned in the direction of the central axis of the ground terminal  221  and disposed such that the central axis of the signal terminal  222  coincides with the central axis of the ground terminal  221 . 
       FIG. 18  is a drawing illustrating a mechanism for pressing the contact  220  disposed in the through hole  210 A of the housing  210  against the board  300 A. In  FIG. 18 , only a part of the housing  210  including one through hole  210 A necessary to describe the operation of the contact  220  is illustrated. 
     A step  210 B is formed in the through hole  210 A. The step  210 B is formed by increasing the inner diameter of a middle part of the through hole  210 A in the axial direction, and prevents the spring  223  from moving upward. The lower end of the spring  223  engages with an inner edge of the through hole  230 A of the bracket  230 , and the spring  223  is thereby prevented from moving downward. With this configuration, the spring  223  is held in a recess formed between the step  210 B and the inner edge of the through hole  230 A of the bracket  230 . 
     With the contact  220  housed inside of the through hole  210 A, the housing  210  is pressed toward the board  300 A and fixed to connect the connection part  222 C and the protrusions  221 D to the signal line and the ground line of the board  300 A. 
       FIG. 19  is a drawing illustrating a surface of the board  300 A to which the contact  220  of the second embodiment is to be connected. An annular conductive part  301 A and a circular conductive part  302 A positioned in the center of the conductive part  301 A in plan view are formed on the board  300 A, and are connected to a ground line and a signal line, respectively. 
     The protrusions  221 D and the connection part  222 C are brought into contact with the conductive part  301 A and the conductive part  302 A, respectively, to connect the contact  220  to the ground line and the signal line of the board  300 A. 
     By using the connector  200  of the second embodiment including the contacts  220  as each of the connectors  100 A and  100 B, it is possible to connect the connector  100 A and the connector  410 A and connect the connector  100 B and the connector  410 B while achieving the impedance matching. 
     That is, the second embodiment makes it possible to connect the board  300 A and the FPCs  420  and connect the board  300 B and the FPCs  420  while achieving the impedance matching. 
     Thus, the second embodiment provides the connector  200  and the contacts  220  that make it possible to transmit a signal in an impedance matched state. 
     Connectors and contacts according to embodiments of the present invention are described above. However, the present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.