Patent Publication Number: US-11664628-B2

Title: Electrical connector with shielding between low and high frequency terminals and electrical connector device using the same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a connector including a shield, and to a connector device including the connector. 
     DESCRIPTION OF RELATED ART 
     Japanese Patent Laid-Open Publication No. 2013-182808 discloses a connector and a shield cover covering the connector. The connector electrically connects a first circuit board to a second circuit board by engaging a socket installed on the first circuit board with a header installed on the second circuit board. The shield cover is engaged with an engagement portion formed on the first circuit board or the second circuit board. The connector includes plural contacts arranged in a single direction. 
     SUMMARY 
     A connector includes plural terminals, a housing holding the terminals, and an inner shield. The connector is configured to be connected to a mating connector by moving toward the mating connector in a first direction relatively with respect to the mating connector. The terminals include two terminals arranged on both sides of the inner shield in a second direction perpendicular to the first direction. The inner shield includes a base extending in a third direction perpendicular to the first direction and the second direction, and an extension protruding from the base. The housing includes a shield holder holding the extension. 
     This connector reduces noise propagation between the terminals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an exploded perspective view of a socket (connector) according to an exemplary embodiment. 
         FIG.  2    is a bottom view of the socket. 
         FIG.  3    is a plan view of the socket. 
         FIG.  4    is a perspective view of an outer shield of the socket. 
         FIG.  5    is an exploded perspective view of a header (connector) according to the exemplary embodiment. 
         FIG.  6    is a plan view of the header. 
         FIG.  7    is a bottom view of the header. 
         FIG.  8    is a perspective view of an outer shield of the header. 
         FIG.  9    is a sectional view of the connector where the socket is separated the header, illustrating including respective inner shields of the socket and the header. 
         FIG.  10    is a sectional view of the connector where the socket is connected to the header, illustrating the inner shields of the socket and the header. 
         FIG.  11    is a sectional view of the connector where the socket is separated from the header, illustrating two terminals of each of the socket and the header. 
         FIG.  12    is a sectional view of the connector where the socket is connected to the header, illustrating the two terminals of each of the socket and the header. 
         FIG.  13    is a bottom view of the connector schematically illustrating the socket. 
         FIG.  14    is a graph illustrating a noise level of the socket and the header and a noise level of a comparative example of a socket and a header. 
         FIG.  15    is a bottom view of modification example 1 of the socket. 
         FIG.  16    is a plan view of modification example 1 of the socket; 
         FIG.  17    is a plan view of modification example 1 of the header. 
         FIG.  18    is a bottom view of modification example 1 of the header. 
         FIG.  19    is a perspective view of modification example 2 of the connector for illustrating two terminals of each of a socket and a header where the socket is separated from the header. 
         FIG.  20    is a perspective view of modification example 2 of the connector for illustrating two terminals of each of the socket and the header where the socket is connected to the header. 
         FIG.  21    is a bottom view of another modification example of the socket. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     (1) Overview 
     A connector and a connector device according to an exemplary embodiment will be described below with reference to drawings. The following exemplary embodiment is just one of various exemplary embodiments of the present disclosure. The following exemplary embodiment can be variously modified in accordance with the design and the like as long as the object of the present disclosure can be achieved. The drawings described in the following exemplary embodiment are schematic diagrams, and the ratio of the size and the thickness of each component in the drawings does not necessarily reflect the actual dimensional ratio. 
     As illustrated in  FIG.  11   , connector device  100  includes a first connector (socket S 1 ) and a second connector (header H 1 ). In the following description, the first connector is also referred to as a “socket S 1 ”, and the second connector is also referred to as a “header H 1 ”. Socket S 1  is connected to header H 1 . At this moment, terminal  4  of socket S 1  is electrically connected to a terminal  8  of header H 1 . When viewed from socket S 1 , header H 1  is a “mating connector” connected to socket S 1 . On the contrary, when viewed from header H 1 , socket S 1  is a “mating connector” connected to header H 1 . That is, connector device  100  includes the connector (socket S 1  or header H 1 ) and the mating connector. When viewed from socket S 1 , terminal  8  of header H 1  is a “mating terminal” electrically connected to terminal  4  of socket S 1 . On the contrary, when viewed from header H 1 , terminal  4  of socket S 1  is a “mating terminal” electrically connected to terminal  8  of header H 1 . 
     (1.1) Configuration 1 
     As illustrated in  FIGS.  1 ,  5 ,  9 , and  13   , in the exemplary embodiment, the connector (socket S 1  or header H 1 ) includes outer shield  1  (or  5 ), terminal  4  (or  8 ), housing  2  (or  6 ), and inner shield  3  (or  7 ). Terminal  4  (or  8 ) is surrounded by outer shield  1  (or  5 ). Terminal  4  (or  8 ) is electrically connected to the mating terminal of the mating connector. Outer shield  1  (or  5 ) is fixed to housing  2  (or  6 ). Housing  2  (or  6 ) holds terminal  4  (or  8 ). Inner shield  3  (or  7 ) is surrounded by outer shield  1  (or  5 ). Inner shield  3  (or  7 ) includes two tip regions r 1  (or r 7 ). Two tip regions r 1  (or r 7 ) includes tip region r 1  (or r 7 ) that faces or is directly coupled to outer shield  1  (or  5 ) and tip region r 1  (or r 7 ) that faces or is directly coupled to outer shield  1  (or  5 ). The longest loop length of electrically-closed loops LO 1 , LO 2 , and LO 3  that do not surround other electrically-closed loops among plural electrically-closed loops described below is shorter than the wavelength of a maximum frequency of a transmission signal flowing through terminal  4  (or  8 ). Each of tip regions r 1  (or r 7 ) of inner shield  7  is connected to outer shield  1  (or  5 ) by respective one of shortest distance L 1  (or L 7 ) via respective one of virtual paths W 7  and W 8  (or W 9  and W 10 ). Each of the plural electrically-closed loops includes outer shield  1  (or  5 ), inner shield  3  (or  7 ), and two virtual paths W 7  and W 8  (or W 9  and W 10 ), and surrounds terminal  4  (or  8 ). When viewed from socket S 1 , inner shield  7  of header H 1  is a mating inner shield. On the contrary, when viewed from header H 1 , inner shield  3  of socket S 1  is a mating inner shield. When viewed from socket S 1 , outer shield  5  of header H 1  is a mating outer shield. On the contrary, when viewed from header H 1 , outer shield  1  of socket S 1  is a mating outer shield. 
     The above configuration reduces resonance of a transmission signal in the electrically-closed loop. 
     In the present disclosure, the “maximum frequency of the transmission signal flowing through the terminal” means, in a case that the signal is transmitted through the terminal, the maximum frequency of a carrier wave of a signal, for example, when a radio frequency (RF) signal is transmitted, and means the frequency being harmonics of three to five times a clock frequency when a digital signal is transmitted. The maximum frequency has, for example, a value determined by a manufacturer or the like of a connector in accordance with the specifications of the connector, or a value determined by the standard or the like of the connector. The maximum frequency is described, for example, as the value of the maximum frequency of which the operation is guaranteed, in the specifications provided by the manufacturer. 
     (1.2) Configuration 2 
     As illustrated in  FIGS.  1 ,  4 ,  5 ,  8 , and  9   , in the exemplary embodiment, the connector (socket S 1  or header H 1 ) includes outer shield  1  (or  5 ), terminal  4  (or  8 ), and housing  2  (or  6 ). Outer shield  1  (or  5 ) includes tubular portion  10  (or  50 ). Both ends of tubular portion  10  (or  50 ) in a predetermined direction are open. Terminal  4  (or  8 ) is surrounded by outer shield  1  (or  5 ). Terminal  4  (or  8 ) is electrically connected to the mating terminal of the mating connector. Outer shield  1  (or  5 ) is fixed to housing  2  (or  6 ). Housing  2  (or  6 ) holds terminal  4  (or  8 ). Outer shield  1  (or  5 ) has distal end surface  102  (or  502 ) of tubular portion  10  (or  50 ), outer circumferential surface  101  (or  501 ) of tubular portion  10  (or  50 ), and inner circumferential surface  103  (or  503 ) of tubular portion  10  (or  50 ). Distal end surface  102  (or  502 ) is provided along the inner edge of tubular portion  10  (or  50 ) at one (which will be described next) of both ends of tubular portion  10  (or  50 ). One end is the end that is on the mating connector side when the connector and the mating connector are transitioned from the disconnected state to the connected state. At least one of distal end surface  102  (or  502 ), outer circumferential surface  101  (or  501 ), and inner circumferential surface  103  (or  503 ) is seamless over the entire circumference of tubular portion  10  (or  50 ) in circumferential direction D 10  (or D 50 ). 
     In the present disclosure, “seamless” means that there are no seams or breaks. 
     The above configuration reduces noise radiated from outer shield  1  (or  5 ) in comparison to a case where each of distal end surface  102  (or  502 ), outer circumferential surface  101  (or  501 ), and inner circumferential surface  103  (or  503 ) has seams or breaks. 
     In the connector as disclosed in Japanese Patent Laid-Open Publication No. 2013-182808, radiation noise may be generated even though the shield cover is attached. 
     On the other hand, the connector in the exemplary embodiment, as described above, reduces noise radiated from outer shield  1  (or  5 ). 
     (1.3) Configuration 3 
     As illustrated in  FIGS.  1 ,  5 , and  10   , in the exemplary embodiment, the connector (socket S 1  or header H 1 ) includes plural terminals  4  (or  8 ). Terminals  4  (or  8 ) are electrically connected to the mating terminals of the mating connector, respectively. The connector further includes housing  2  (or  6 ) and inner shield  3  (or  7 ). Housing  2  (or  6 ) holds terminals  4  (or  8 ). The connector is connected to the mating connector by moving at least one toward the other in up-down direction Dud relatively. Terminals  4  (or  8 ) include two terminals  4  (or  8 ). Two terminals  4  (or  8 ) are arranged on both sides of inner shield  3  (or  7 ) in front-back direction Dfb perpendicular to up-down direction Dud. Inner shield  3  (or  7 ) includes base  31  (or  71 ) and extension  32  (or  72 ). Base  31  (or  71 ) extends in left-right direction Dlr perpendicular to up-down direction Dud and front-back direction Dfb. Extension  32  (or  72 ) protrudes from base  31  (or  71 ) in up-down direction Dud. Housing  2  (or  6 ) includes a shield holder (accommodation portion  28  or  68 ). The shield holder holds extension  32  (or  72 ). 
     Since two terminals  4  (or  8 ) are arranged on both sides of inner shield  3  (or  7 ), the above configuration reduces noise propagation between two terminals  4  (or  8 ) more than a connector where inner shield  3  (or  7 ) is not provided. Since extension  32  (or  72 ) of the connector is positioned by the shield holder (accommodation portion  28  or  68 ), the accuracy of alignment between extension  32  (or  72 ) of the connector and the mating connector is improved. In the exemplary embodiment, extension  32  (or  72 ) of the connector is electrically connected to the inner shield of the mating connector. This configuration improves the accuracy of the electrical connection between extension  32  (or  72 ) of the connector and the inner shield of the mating connector. 
     In the connector disclosed in Japanese Patent Laid-Open Publication No. 2013-182808, radiation noise may be generated by the noise propagating between plural contacts (terminals). 
     On the other hand, the connector in the exemplary embodiment, as described above, reduces noise propagation between two terminals  4  (or  8 ). 
     (1.4) Configuration 4 
     As illustrated in  FIGS.  1 ,  2 ,  5 , and  6   , in the exemplary embodiment, the connector (socket S 1  or header H 1 ) includes plural terminals  4  (or  8 ), housing  2  (or  6 ), and inner shield  3  (or  7 ). Terminals  4  (or  8 ) are electrically connected to the mating terminals of the mating connector, respectively. Housing  2  (or  6 ) holds terminals  4  (or  8 ). The connector is connected to the mating connector by moving at least one toward the other in up-down direction Dud relatively. In the exemplary embodiment, socket S 1  being the connector is connected to header H 1  by moving toward header H 1  to header H 1  being the mating socket in an upward direction Du being a predetermined direction relatively with respect to header H 1 . Terminals  4  (or  8 ) include two terminals  4  (or  8 ). Two terminals  4  (or  8 ) are arranged on both sides of inner shield  3  (or  7 ) in front-back direction Dfb perpendicular to up-down direction Dud. 
     The above configuration reduces noise propagation between two terminals  4  (or  8 ) more than a connector where inner shield  3  (or  7 ) is not provided. 
     In the above configuration, the connector preferably further include outer shield  1  (or  5 ). Outer shield  1  (or  5 ) surrounds terminals  4  (or  8 ) and inner shield  3  (or  7 ). 
     The connector including outer shield  1  (or  5 ) reduces the propagation or the radiation of noise between the inside and the outside of outer shield  1  (or  5 ). 
     (2) Details 
     The connectors (socket S 1  and header H 1 ) according to the exemplary embodiment will be detailed below with reference to  FIGS.  1  to  14   . 
     Unless otherwise specified, description will be made on the assumption that a direction in which socket S 1  and header H 1  are connected or separated to or from each other is up-down direction Dud, and header H 1  side when viewed from socket S 1  is upward direction Du. The description will be made on the assumption that the longitudinal direction of housing  2  of socket S 1 , which is perpendicular to up-down direction Dud, is front-back direction Dfb. The description will be made on the assumption that a direction perpendicular to up-down direction Dud and front-back direction Dfb, that is, the lateral direction of housing  2  is left-right direction Dlr. That is, in  FIG.  1    and the like, as indicated by the arrows of “up”, “down”, “front”, “back”, “left”, and “right”, upward direction Du, downward direction Dd, forward direction Df, backward direction Db, leftward direction Dl, and rightward direction Dr are defined. The above directions are not intended to define the directions in which socket S 1  and header H 1  are used. The arrows indicating the directions in the drawing are shown only for the explanation, and are not accompanied by actual ones. 
     As described above, the connector and the mating connector are connected to each other by moving at least one toward the other in up-down direction Dud. In the exemplary embodiment, socket S 1  and header H 1  are connected to each other by at least one of a method in which socket S 1  is disposed below header H 1 , and socket S 1  moves in upward direction Du, and a method in which the socket is disposed below the header, and header H 1  moves in downward direction Dd. Therefore, “the mating connector side when the connector and the mating connector are transitioned from the disconnected state to the connected state” means the upper side when socket S 1  is used as the connector, and means the lower side when header H 1  is used as the connector. 
     In the exemplary embodiment, socket S 1  and header H 1  are attached to circuit boards  150  and  550  (see  FIG.  10   ) such as printed wiring boards or flexible printed wiring boards, respectively. Socket S 1  and header H 1  are used for electrically connecting plural circuit boards mounted into a portable terminal, such as a smartphone, for example. This description does not intend to limit the use of socket S 1  and header H 1 , and socket S 1  and header H 1  may be used in an electronic device, such as a camera module, other than a portable terminal. The use of socket S 1  and header H 1  is not limited to the use of electrically connecting plural circuit boards to each other. The socket and the header may be used for electrically connecting plural components, for example, electrically connecting a circuit board and a display or electrically connecting a circuit board and a battery, to each other. 
     Socket S 1  and header H 1  may be provided in a state of not being connected to circuit boards  150  and  550 , respectively, or may be provided in a state of being connected. 
     (2.1) Configuration of Socket 
     Firstly, a configuration of socket S 1  according to the exemplary embodiment will be described. 
     Socket S 1  is two-fold symmetrical with respect to an axis passing through the center of socket S 1  along up-down direction Dud, as a symmetric axis. As illustrated in  FIG.  1   , socket S 1  includes outer shield  1 , housing  2 , plural (two) inner shields  3 , and plural (eight) terminals  4 . Each of outer shield  1  and inner shields  3  is an electrostatic shield. Outer shield  1  surrounds terminals  4 . That is, outer shield  1  is disposed outside terminals  4 . Inner shields  3  are arranged inside outer shield  1  Inner shields  3  are arranged inside housing  2 . 
     Circuit board  150  (see  FIG.  9   ) is mechanically and electrically connected to socket S 1 . In the exemplary embodiment, circuit board  150  is a double-sided board, but circuit board  150  may be a multi-layered board. Circuit board  150  includes substrate  160  (see  FIG.  9   ) and conductors  170  and  180  (see  FIG.  9   ). Substrate  160  is, for example, a semiconductor substrate or a glass substrate. Conductor  170  is a pattern of, for example, a copper foil provided on a surface of substrate  160 . For example, conductor  170  is provided substantially on the entire surface of substrate  160  to which socket S 1  is connected. Conductor  180  is, for example, solder. Conductor  180  is provided in a predetermined region (land) of conductor  170 . Conductor  170  is electrically connected to outer shield  1 , inner shields  3 , and terminals  4  through conductor (solder)  180 . Outer shield  1  and inner shields  3  are electrically connected to, e.g. a ground provided on circuit board  150 . In  FIG.  2   , a region in which conductor (solder)  180  is provided is illustrated by a two-dot chain line. 
     (2.1.1) Housing of Socket 
     Housing  2  is made of a molded resin. Housing  2  has electrical insulating properties. As illustrated in  FIGS.  1  to  3   , housing  2  has bottom wall  21  and peripheral wall  22 . Bottom wall  21  has a rectangular shape in which the length thereof in front-back direction Dfb is longer than the length thereof in left-right direction Dlr in a plan view. Peripheral wall  22  protrudes from the entire circumference of the outer circumferential portion of one surface (upper surface) of bottom wall  21  in a thickness direction of the bottom wall, i.e., in upward direction Du. Housing  2  has a rectangular parallelepiped shape which is flat to extend perpendicularly to up-down direction Dud, and has recess  24  (see  FIG.  3   ) in the center of the upper surface which is a surface facing header H 1  among both sides of the housing in up-down direction Dud. The recess is surrounded by peripheral wall  22 . 
     Peripheral wall  22  has a tubular shape. Peripheral wall  22  surrounds plural terminals  4 . Peripheral wall  22  extends continuously over the entire circumference of peripheral wall  22  in circumferential direction D 22  (see  FIG.  1   ). In other words, peripheral wall  22  has no break over the entire circumference of peripheral wall  22  in circumferential direction D 22 . As illustrated in  FIG.  1   , peripheral wall  22  includes two peripheral walls  221  and two peripheral walls  222 . Two peripheral walls  221  are portions of peripheral wall  22 , and extend substantially parallel to front-back direction Dfb. Two peripheral walls  221  face each other in left-right direction Dlr across recess  24 . Two peripheral walls  222  are portions of peripheral wall  22 , and extend substantially parallel to left-right direction Dlr. Two peripheral walls  222  face each other in front-back direction Dfb across recess  24 . Each of two peripheral walls  222  connects the ends of two peripheral walls  221  to each other. That is, housing  2  has a shape in which one opening surface (lower surface) of peripheral wall  22  having a rectangular tubular shape with a quadrangular cross section is closed by bottom wall  21 . 
     As illustrated in  FIG.  3   , housing  2  further includes wall portion  25 , wall portion  26 , and wall portion  27 . Wall portion  25 , wall portion  26 , and wall portion  27  protrude from bottom wall  21  in upward direction Du. Wall portion  25 , wall portion  26 , and wall portion  27  are arranged in recess  24 . That is, wall portion  25 , wall portion  26 , and wall portion  27  are surrounded by peripheral wall  22 . Wall portion  25 , wall portion  26 , and wall portion  27  have rectangular parallelepiped shapes. When viewed in up-down direction Dud, each of wall portion  25 , wall portion  26 , and wall portion  27  is longer in front-back direction Dfb than in left-right direction Dlr. That is, wall portion  25 , wall portion  26 , and wall portion  27  are wall portions having a thickness in the direction along left-right direction Dlr. Wall portion  25 , wall portion  26 , and wall portion  27  are arranged in this order from the left to the right, that is, in rightward direction Dr. 
     Each of the wall portions (wall portion  25 , wall portion  26 , and wall portion  27 ) includes plural (two) accommodation portions  28 . Extension  32  of inner shield  3  is accommodated in each of accommodation portions  28 . Each of accommodation portions  28  is a through-hole provided in the wall portion. Accommodation portion  28  passes through the wall portion in up-down direction Dud. Accommodation portion  28  also passes through bottom wall  21  in up-down direction Dud. When viewed in up-down direction Dud, accommodation portions  28  provided in wall portion  25  and the wall portions  27  are recesses penetrating from the side surface (surface intersecting in left-right direction Dlr) of wall portion  25  (wall portion  27 ). 
     Each of the wall portions (wall portion  25 , wall portion  26 , and wall portion  27 ) includes plural terminal holders  29 . Each of terminal holders  29  holds terminal  4 . Each of terminal holders  29  is a through-hole provided in the wall portion. This through-hole passes through terminal holder  29  in up-down direction Dud. When viewed in up-down direction Dud, terminal holder  29  is a recess penetrating from the side surface (surface intersecting in left-right direction Dlr) of the wall portion. Two of terminal holders  29  correspond to one set. One set of two terminal holders  29  corresponding to each other are arranged in left-right direction Dlr. A portion of bottom wall  21  between two terminal holders  29  corresponding to each other is through-hole  211  into which terminal  4  is inserted. 
     Plural terminals  4  are fixed to housing  2  by press fitting. That is, Terminals  4  are held in housing  2  by being pushed into housing  2  in one direction (upward). In the exemplary embodiment, eight terminals  4  are fixed to housing  2 . Eight terminals  4  are arranged in two rows. That is, four terminals  4  among eight terminals  4  form a first row, and the remaining four terminals  4  form a second row. Four terminals  4  in each row are arranged in front-back direction Dfb. Each of four terminals  4  forming the first row is held by terminal holder  29  of wall portion  25  and terminal holder  29  of wall portion  26 . Each of four terminals  4  forming the second row is held by terminal holder  29  of wall portion  26  and terminal holder  29  of wall portion  27 . That is, each of terminals  4  is disposed between the two wall portions and is supported from both sides of the each terminal by the two wall portions. 
     As illustrated in  FIG.  2   , bottom wall  21  has plural notches  212  provided therein. Notches  212  are provided at positions facing board connection portions  45  (described later) of terminals  4  when viewed in up-down direction Dud. Bottom wall  21  has plural (two) accommodation grooves  213  provided therein. Each of accommodation grooves  213  is a groove provided in the lower surface of bottom wall  21 . Accommodation groove  213  is longer in left-right direction Dlr than in front-back direction Dfb. Accommodation groove  213  accommodates base  31  of inner shield  3  therein. 
     Peripheral wall  22  includes plural (four) insertion portions  223 . Plural (four) insertion portions  223  are recesses penetrating from the side surfaces (inner surfaces) of two peripheral walls  221  and two peripheral walls  222 . As described later, shield protrusion  14  which is a portion of outer shield  1  is inserted into each of plural (four) insertion portions  223 . 
     (2.1.2) Outer Shield of Socket 
     Outer shield  1  surrounds terminals  4  and inner shields  3 . Outer shield  1  contains metal as a main material or a material forming the surface, such as plating. Here, as an example, outer shield  1  is made of metal as main material. As illustrated in  FIGS.  1  and  4   , outer shield  1  includes tubular portion  10  and plural (four) shield protrusions  14 . Tubular portion  10  includes outer peripheral wall  11 , top wall  12 , and inner peripheral wall  13 . 
     Outer peripheral wall  11  has a rectangular tubular shape with a rectangular cross section. Outer peripheral wall  11  includes two outer peripheral walls  111  and two outer peripheral walls  112 . Two outer peripheral walls  111  are portions of outer peripheral wall  11 , and extend substantially in front-back direction Dfb. Two outer peripheral walls  111  face each other in left-right direction Dlr. Two outer peripheral walls  112  are portions of outer peripheral wall  11 , and extend substantially in left-right direction Dlr. Two outer peripheral walls  112  face each other in front-back direction Dfb. Each of two outer peripheral walls  112  connects the ends of two outer peripheral walls  111  to each other. The lower end portions (lower surfaces) of outer peripheral wall  111  and outer peripheral wall  112  are parallel to a plane extending in left-right direction Dlr and front-back direction Dfb. 
     Top wall  12  has a rectangular frame shape when viewed in up-down direction Dud. Top wall  12  is connected to the upper end of outer peripheral wall  11  and extends toward inside outer peripheral wall  11  when viewed in up-down direction Dud. 
     Inner peripheral wall  13  is provided inside outer peripheral wall  11 . Inner peripheral wall  13  has a rectangular tubular shape with a rectangular cross section. The upper end of outer peripheral wall  11  and the upper end of inner peripheral wall  13  are joined to each other by top wall  12 . 
     Inner peripheral wall  13  includes two inner peripheral walls  131  and two inner peripheral walls  132 . Two inner peripheral walls  131  are portions of inner peripheral wall  13 , and extend substantially in front-back direction Dfb. Two inner peripheral walls  131  face each other in left-right direction Dlr. Two inner peripheral walls  132  are portions of inner peripheral wall  13 , and extend substantially parallel to left-right direction Dlr. Two inner peripheral walls  132  face each other in front-back direction Dfb. Each of two inner peripheral walls  132  connects the ends of two inner peripheral walls  131  to each other. 
     Outer peripheral wall  11 , top wall  12 , and inner peripheral wall  13  constitute tubular portion  10  having both ends which open in up-down direction Dud. The outer circumferential surface of outer peripheral wall  11  corresponds to outer circumferential surface  101  of tubular portion  10 . The inner circumferential surface of inner peripheral wall  13  corresponds to inner circumferential surface  103  of tubular portion  10 . Outer shield  1  has distal end surface  102 . Distal end surface  102  is provided at one end (upper end) among both the ends of tubular portion  10  in up-down direction Dud. The one end is on the mating connector side when the connector (socket S 1 ) and the mating connector (header H 1 ) are transitioned from the disconnected state to the connected state. Distal end surface  102  has a loop shape extending along the inner edge of tubular portion  10 . The upper surface of top wall  12  corresponds to distal end surface  102 . The inner edge of distal end surface  102  corresponds to the inner edge of tubular portion  10  at the upper end of tubular portion  10 . 
     Boundary b 1  between distal end surface  102  and outer circumferential surface  101  is a surface arcuate when viewed in front-back direction Dfb (see  FIG.  9   ). Boundary b 2  between distal end surface  102  and inner circumferential surface  103  is a surface arcuate when viewed in front-back direction Dfb (see  FIG.  9   ). Distal end surface  102  is defined as a region of the outer surface of tubular portion  10  forming an acute angle with respect to up-down direction Dud is equal to or larger than 0 degrees and smaller than 45 degrees. The outer surface forming an acute angle equal to or larger than 45 degrees is defined as outer circumferential surface  101 . The inner surface having an acute angle which is equal to or larger than 45 degrees is defined as inner circumferential surface  103 . Tubular portion  10  surrounds hollow space  10 S. Boundary b 1  includes a portion of distal end surface  102  and a portion of outer circumferential surface  101  over the entire circumference in circumferential direction D 10  (see  FIG.  4   ) surrounding hollow space  10 S of tubular portion  10 . Boundary b 2  includes a portion of distal end surface  102  and a portion of inner circumferential surface  103  over the entire circumference of tubular portion  10  in circumferential direction D 10 . 
     Plural (four) shield protrusions  14  are provided corresponding to two inner peripheral walls  131  and two inner peripheral walls  132 , respectively. Each of the shield protrusions  14  protrudes downward from corresponding inner peripheral wall  131  or inner peripheral wall  132 . Each of plural (four) shield protrusions  14  corresponds to respective one of plural (four) insertion portions  223  (see  FIG.  2   ) provided in housing  2 . Each of shield protrusions  14  is inserted into corresponding one of insertion portions  223 . 
     Outer shield  1  is insert-molded with housing  2 . More specifically, outer shield  1  is insert-molded with housing  2  so that peripheral wall  22  of housing  2  is inserted between outer peripheral wall  11  and inner peripheral wall  13  of outer shield  1 . 
     The entire surface of outer shield  1  is seamlessly formed. Outer shield  1  is formed, for example, by drawing. Thus, the entire surface of outer shield  1  is seamlessly formed. In the exemplary embodiment, at least outer circumferential surface  101  and inner circumferential surface  103  among the surfaces of outer shield  1  are seamless over the entirety of tubular portion  10  in circumferential direction D 10  (that is, there are no seams or breaks). In the exemplary embodiment, distal end surface  102  is seamless over the entirety of tubular portion  10  in circumferential direction D 10 . 
     For example, regarding outer circumferential surface  101 , as illustrated in  FIG.  4   , outer circumferential surface  101  includes outer surface  1110  of each of two outer peripheral walls  111  and outer surface  1120  of each of two outer peripheral walls  112 . Each of outer surface  1110  and outer surface  1120  is seamless. Outer surface  1110  and outer surface  1120  which have different normal directions are seamlessly connected to each other. Outer circumferential surface  101  is thus seamless over the entirety of tubular portion  10  in circumferential direction D 10 . 
     For example, regarding inner circumferential surface  103 , as illustrated in  FIG.  4   , inner circumferential surface  103  includes outer surface  1310  of each of two inner peripheral walls  131  and outer surface  1320  of each of two inner peripheral walls  132 . Each of outer surface  1310  and outer surface  1320  is seamless. Outer surface  1310  and outer surface  1320  which have different normal directions are seamlessly connected to each other. Inner circumferential surface  103  is thus seamless over the entirety of tubular portion  10  in circumferential direction D 10 . 
     At least one (both in the exemplary embodiment) of boundary b 1  between distal end surface  102  and outer circumferential surface  101  and boundary b 2  between distal end surface  102  and inner circumferential surface  103  is seamless over the entire circumference of tubular portion  10  in circumferential direction D 10 . 
     For example, at the upper right (corner portion of outer shield  1 ) in  FIG.  4   , outer surface  1110  of outer peripheral wall  111 , outer surface  1120  of outer peripheral wall  112 , and distal end surface  102  are seamlessly connected. That is, outer surface  1110 , outer surface  1120 , and distal end surface  102  which have different normal directions are seamlessly connected to one another. On the right in  FIG.  4   , outer surface  1110  and distal end surface  102  which have different normal directions are seamlessly connected to each other. At the upper portion in  FIG.  4   , outer surface  1120  and distal end surface  102  which have different normal directions are seamlessly connected to each other. Boundary b 1  is thus seamless over the entirety of tubular portion  10  in circumferential direction D 10 . 
     For example, at the lower left (corner portion of outer shield  1 ) in FIG.  4 , outer surface  1310  of inner peripheral wall  131 , outer surface  1320  of inner peripheral wall  132 , and distal end surface  102  are seamlessly connected to one another. That is, outer surface  1310 , outer surface  1320 , and distal end surface  102  which have different normal directions are seamlessly connected to one another. On the left in  FIG.  4   , outer surface  1310  and distal end surface  102  which have different normal directions are seamlessly connected to each other. At the lower portion in  FIG.  4   , outer surface  1320  and distal end surface  102  which have different normal directions are seamlessly connected to each other. Boundary b 2  is thus seamless over the entirety of tubular portion  10  in circumferential direction D 10 . 
     (2.1.3) Inner Shield of Socket 
     In the exemplary embodiment, two inner shields  3  have the same shape. Inner shield  3  contains metal as a main material or a material forming the surface, such as plating. Here, inner shield  3  is made of metal as main material. As illustrated in  FIGS.  1  and  9   , inner shield  3  includes base  31  and plural (three) extensions  32  (two extensions  33  and one extension  34 ). 
     Base  31  has a length in along left-right direction Dlr. Base  31  has a plate shape. When viewed in a thickness direction (front-back direction Dfb) of base  31 , base  31  is longer in left-right direction Dlr than in up-down direction Dud. Base  31  is accommodated in accommodation groove  213  provided in bottom wall  21  of housing  2 . 
     As illustrated in  FIG.  9   , plural extensions  32  protrude upward from base  31 . That is, extensions  32  protrude in up-down direction Dud to be directed to the mating connector side when the connector (socket S 1 ) and the mating connector (here, header H 1 ) are transitioned from the disconnected state to the connected state. Extensions  32  have plate shapes. When viewed in a thickness direction (front-back direction Dfb) of each of extensions  32 , each of extensions  32  is longer in up-down direction Dud than in left-right direction Dlr. The thickness direction of extension  32  may be left-right direction Dlr. 
     Extension  33  includes extension body  331  and contacting portion  332 . Extension body  331  protrudes from base  31 . Contacting portion  332  is configured to contact the mating inner shield (inner shield  7 ) of the mating connector (header H 1 ). Contacting portion  332  protrudes from extension body  331  in a longitudinal direction (direction Dl or direction Dr). Contacting portion  332  is provided on surface  332 S (here, left surface or right surface) of extension  33  (extension body  331 ) in the longitudinal direction of extension  33 . That is, contacting portion  332  protrudes from extension body  331  in left-right direction Dlr. 
     Contacting portions  332  of two extensions  33  face each other in left-right direction Dlr. Contacting portion  332  is configured to contact contacting portion  720  of inner shield  7  of header H 1  while socket S 1  is connected to header H 1  (see  FIG.  10   ). Thus, each of two inner shields  3  is electrically connected to corresponding one of inner shields  7  of two inner shields  7  of header H 1 . Specifically, two extensions  72  of inner shield  7  are inserted between two extensions  33  of inner shield  3 . At this moment, two extensions  72  are pressed against two extensions  33  due to elasticity of two extensions  72  and two extensions  33 . 
     Extension  34  includes extension body  341  and plural (two) holding protrusions  342 . Extension body  341  protrudes from base  31 . Two holding protrusions  342  protrude from extension body  341 . Two holding protrusions  342  are provided on the left end and the right end of extension body  341 . That is, one of two holding protrusions  342  protrudes from extension body  341  in the left direction Dl, and the other protrudes from extension body  341  in the right direction Dr. 
     Socket S 1  includes three extensions  32  on each of two inner shields  3 . That is, socket S 1  includes six extensions  32  in total. Each of six accommodation portions  28  (see  FIG.  3   ) provided in housing  2  corresponds to respective one of six extensions  32 . Each of extensions  32  is accommodated in corresponding accommodation portion  28 . More specifically, extension  33  is accommodated in accommodation portion  28  of wall portion  25  and wall portion  27 . Extension  34  is accommodated in accommodation portion  28  of wall portion  26 . In extension  34 , the width including two holding protrusions  342  in left-right direction Dlr is slightly larger than the width of accommodation portion  28  in left-right direction Dlr. Inner shield  3  is fixed to housing  2  by press fitting. That is, inner shield  3  is held in housing  2  by being pushed into housing  2  in one direction (upward). Inner shield  3  is held in housing  2  while two holding protrusions  342  are sandwiched by the inner surfaces of accommodation portion  28  in between. 
     The accommodation space of each of two extensions  33  in the shield holder (accommodation portion  28 ) is larger than each of two extensions  33 . That is, a margin is provided in the alignment between each of two extensions  33  and the inner surface of accommodation portion  28 . This function of holding inner shield  3  in housing  2  is realized by at least extension  34 . That is, inner shield  3  is held in housing  2  by press fitting at least extension  34  into accommodation portion  28 . Plural extensions  32  include extension  33  including contacting portion  332  contacting inner shield  7  of the mating connector (here, header H 1 ) and extension  34  held in the shield holder (accommodation portion  28 ). Extension  34  may also include a contacting portion configured to contact inner shield  7  of the mating connector (here, header H 1 ). 
     As illustrated in  FIG.  9   , base  31  of inner shield  3  is located at the lower end of socket S 1 . Inner shield  3  is surrounded by outer shield  1 . Inner shield  3  includes two tip regions r 1  facing outer shield  1 . Two tip regions r 1  are provided at both ends (left end and right end) of base  31  in a longitudinal direction of the base. 
     Outer shield  1  has end e 1  and end e 2 . End e 1  is an end (upper end) that is on the mating connector side when the connector (here, socket S 1 ) and the mating connector (here, header H 1 ) are transitioned from the disconnected state to the connected state. End e 2  is an end (lower end) opposite to end e 1 . End e 2  is a region of outer shield  1  extending over the entire circumference of tubular portion  10  in circumferential direction D 10 . Outer shield  1  faces two tip regions r 1  in the region of outer shield  1  including end e 2 . 
     Outer shield  1  faces at least one of two tip regions r 1  with gap g 1  in between in the region of outer shield  1  including end e 2 . As illustrated in  FIG.  9   , conductors  170  and  180  of circuit board  150  are electrically connected to outer shield  1 . Conductors  170  and  180  are provided to bridge end e 2  of outer shield  1  to two tip regions r 1  of inner shield  3 , respectively. That is, outer shield  1  is electrically connected to inner shield  3  through conductors  170  and  180 . In a state where circuit board  150  is not provided, outer shield  1  is electrically insulated from at least one (both in the exemplary embodiment) of two tip regions r 1  via gap g 1 . Shortest distance L 1  between outer shield  1  and at least one of two tip regions r 1  in gap g 1  is equal to or greater than 0.01 mm and equal to or less than 0.1 mm. 
     Inner shield  3  has end e 3  and end e 4 . End e 3  is an end (upper end) that is on the mating connector side when the connector (here, socket S 1 ) and the mating connector (here, header H 1 ) are transitioned from the disconnected state to the connected state. End e 4  is an end (lower end) opposite to end e 3 . Inner shield  3  has connection surface  310  (lower surface) at end e 4 . Connection surface  310  is configured to be electrically connected to circuit board  150 . Connection surface  310  is flat and continuously extends over two tip regions r 1 . More specifically, connection surface  310  is a rectangular flat surface connecting two tip regions r 1  to each other. 
     (2.1.4) Terminal of Socket 
     (2.1.4.1) Arrangement 
     As illustrated in  FIGS.  2  and  3   , plural (eight) terminals  4  include plural (six) low-frequency terminals  4 P and plural (two) high-frequency terminals  4 T. Each of terminals  4  is inserted into through-hole  211  of bottom wall  21  of housing  2  and is held by terminal holder  29 . 
     Two high-frequency terminals  4 T are arranged on both sides of at least one inner shield  3 . In other words, at least one inner shield  3  is disposed between two high-frequency terminals  4 T. This configuration reduces noise propagation between two high-frequency terminals  4 T. 
     More specifically, two high-frequency terminals  4 T are arranged on both sides of at least one inner shield  3  in front-back direction Dfb, that is, arranged on the front side and the back side of inner shield  3 . Focusing on one of two inner shields  3  in  FIG.  2   , one high-frequency terminal  4 T is disposed in front of inner shield  3 , that is, in forward direction Df from inner shield  3 . In addition, the remaining one high-frequency terminal  4 T is disposed behind inner shield  3 , that is, in backward direction Db from inner shield  3 . Two inner shields  3  are arranged between two high-frequency terminals  4 T. A longitudinal direction (left-right direction Dlr) of inner shield  3  is a direction intersecting with a direction (substantially front-back direction Dfb) in which two high-frequency terminals  4 T are arranged. 
     Six low-frequency terminals  4 P are arranged between two inner shields  3 . That is, one of two inner shields  3  separates a space in which one of two high-frequency terminals  4 T is disposed from a space in which six low-frequency terminals  4 P are arranged. The other of two inner shields  3  separates a space in which the other of two high-frequency terminals  4 T is disposed from the space in which six low-frequency terminals  4 P are arranged. Six low-frequency terminals  4 P are arranged in two rows each containing three thereof in front-back direction Dfb. 
     Three low-frequency terminals  4 P in each row are arranged at equal pitches in front-back direction Dfb. High-frequency terminals  4 T are arranged in front of or behind low-frequency terminal  4 P at the end of each row, that is, in forward direction Df or backward direction Db from low-frequency terminal  4 P at the end of each row. The pitch between low-frequency terminal  4 P and high-frequency terminal  4 T is an integer multiple (twice in the exemplary embodiment) of the pitch between three low-frequency terminals  4 P. This arrangement allows six low-frequency terminals  4 P and two high-frequency terminals  4 T to be easily assembled into housing  2 . 
     In the exemplary embodiment, the pitch between low-frequency terminal  4 P and high-frequency terminal  4 T is longer than the pitch between three low-frequency terminals  4 P. This arrangement secures a space for arranging inner shield  3  between low-frequency terminal  4 P and high-frequency terminal  4 T. 
     A space in which plural low-frequency terminals  4 P are arranged is provided between two high-frequency terminals  4 T. This configuration secures the distance between two high-frequency terminals  4 T, and accordingly reduces noise propagation between two high-frequency terminals  4 T. Two high-frequency terminals  4 T are arranged at diagonal positions inside peripheral wall  22  of housing  2 , accordingly increasing the distance between two high-frequency terminals  4 T. 
     Two high-frequency terminals  4 T are electrically connected to a signal line made of conductor  170  patterned on circuit board  150 . At least one of six low-frequency terminals  4 P is electrically connected to a power line made of conductor  170  patterned on circuit board  150 . A signal having a higher frequency is transmitted through two high-frequency terminals  4 T than the frequency in six low-frequency terminals  4 P. The frequency of the signal transmitted by two high-frequency terminals  4 T ranges, for example, from about 5 to 50 GHz. 
     At least one of six low-frequency terminals  4 P may be electrically connected to inner shield  3 , thus having a potential equal to the potential of inner shield  3 . Specifically, the potential of the at least one of six low-frequency terminals  4 P and the potential of inner shield  3  are a ground potential. At least one of six low-frequency terminals  4 P may be electrically connected to inner shield  3 , for example, through conductors  170  and  180  of circuit board  150 . At least one of six low-frequency terminals  4 P may be electrically connected to inner shield  3  not through circuit board  150 . 
     (2.1.4.2) Shape 
     Terminals  4  have the same shape. Terminals  4  are formed, for example, by punching and bending a metal plate. As illustrated in  FIG.  11   , each of terminals  4  includes contact portion  41 , base  42 , joining portion  43 , protruding portion  44 , board connection portion  45 , and contact portion  46 . 
     Board connection portion  45  is electrically connected to, for example, conductor  180  (solder) of circuit board  150 . That is, board connection portion  45  is bonded to circuit board  150  by a connecting method, such as soldering. Thus, terminal  4  is electrically and mechanically connected to circuit board  150 . As illustrated in  FIG.  2   , board connection portion  45  is surrounded by outer shield  1  when viewed in up-down direction Dud. At least a portion of board connection portion  45  and at least a portion of outer shield  1  are located on one plane perpendicular to up-down direction Dud. 
     Joining portion  43  has a U-shape opening in downward direction Dd. Joining portion  43  joins the upper end portion of base  42  to the upper end portion of contact portion  41 . The lower end portion of base  42  is connected to board connection portion  45 . 
     Protruding portion  44  has a U-shape opening in upward direction Du. Protruding portion  44  connects the lower end portion of contact portion  41  to contact portion  46 . Contact portion  41  faces contact portion  46  in left-right direction Dlr. In the exemplary embodiment, at least joining portion  43  and protruding portion  44  of terminal  4  have elasticity. 
     While terminal  4  is held in housing  2 , at least respective portions of contact portion  41  and contact portion  46  is exposed when viewed from above. Contact portion  41  and contact portion  46  contact corresponding terminals  8  among plurality of terminals  8  (mating terminals) of header H 1  (mating connector) to be electrically connected to terminal  8  (see  FIG.  12   ). Specifically, contact portion  81  and contact portion  84  of terminal  8  are inserted between contact portion  41  and contact portion  46 . At this moment, contact portion  41  and contact portion  46  are pressed against terminal  8  by the elasticity of protruding portion  44 . 
     Terminal  4  further includes force-sensing portion  47 . Force-sensing portion  47  generates a click feeling when terminal  4  contacts terminal  8  (mating terminal). Force-sensing portion  47  is a protrusion that protrudes from contact portion  41 . When force-sensing portion  85  (protrusion) of terminal  8  moves over force-sensing portion  47 , the click feeling is generated. Specifically, if force-sensing portion  85  moves downward and over force-sensing portion  47 , the magnitude of a force acting between terminal  4  and terminal  8  decreases. Therefore, a worker who connects terminal  4  to terminal  8  senses the decrease in the magnitude of the force by the click feeling. The worker recognizes the progress of the connection between socket S 1  and header H 1  by sensing the click feeling. The connection between socket S 1  and header H 1  and the connection between terminal  4  and terminal  8  which accompanies the connection between socket S 1  and header H 1  are not necessarily performed manually, but by a machine. 
     When terminal  4  is connected to terminal  8 , contact portion  46  is inserted into dent  840  of terminal  8 . When terminal  4  and terminal  8  are transitioned from the connected state to the disconnected state, a certain amount or larger of force is required to cause force-sensing portion  85  to move upward and over force-sensing portion  47  and to remove contact portion  46  from dent  840 . As described above, a combination of force-sensing portion  85  and force-sensing portion  47  and a combination of contact portion  46  and dent  840  constitute lock mechanisms maintaining the connected state between socket S 1  and header H 1 . 
     As illustrated in  FIG.  3   , contacting portion  332  of inner shield  3  and contact portion  41  of at least one of terminals  4  are arranged in front-back direction Dfb. 
     (2.1.5) Circuit Board on Socket Side 
     Socket S 1  is electrically connected to conductor  180  (solder) on circuit board  150 . In  FIG.  2   , a region in which conductor  180  is provided on the lower surface of socket S 1  is indicated by a two-dot chain line. Some of conductors  180  are provided on the lower surface of outer shield  1  along circumferential direction D 10  of outer shield  1 . Here, conductors  180  are provided on the lower surface of outer shield  1  in each of plural regions spaced from each other along circumferential direction D 10  of outer shield  1 . Conductors  180  may continuously extend on the lower surface of outer shield  1  over the entire circumference of outer shield  1  along circumferential direction D 10 . That is, outer shield  1  may continuously contact conductors  180  over the entire circumference of circumferential direction D 10 . 
     Some of conductors  180  are provided to bridge outer shield  1  to each of inner shields  3 . Some of conductors  180  are provided on the lower surface of each of inner shields  3  in the longitudinal direction of inner shield  3 . Here, conductors  180  are provided on the lower surface of each of inner shields  3  in each of plural (three) regions spaced from each other along the longitudinal direction of inner shield  3 . Conductors  180  may continuously extend on the lower surface of each of inner shields  3  over the entire longitudinal direction of inner shield  3 . That is, inner shield  3  may continuously contact conductors  180  over the entire longitudinal direction of the inner shield. 
     Some of conductors  180  are electrically connected to outer shield  1  and each of inner shields  3  as described above, and are electrically connected to conductor  170  having a ground potential among conductors  170  of circuit board  150 . That is, outer shield  1  and inner shields  3  have the ground potential. Most of the surface of substrate  160  on the side to which socket S 1  is connected is preferably occupied by conductor  170  having the ground potential. That is, a so-called ground plane is preferably provided on circuit board  150 , thereby improving a shielding effect. 
     Some of conductors  180  are electrically connected to board connection portions  45  of terminals  4 . Terminal  4  is electrically connected to a circuit through conductor  170  (wiring pattern) of circuit board  150 . For example, plural high-frequency terminals  4 T are electrically connected to a circuit that processes a signal. For example, at least some of low-frequency terminals  4 P are electrically connected to wirings for transmitting a signal having a frequency lower than the frequency of a signal transmitted by high-frequency terminal  4 T, or to a power supply circuit or the ground. 
     (2.1.6) Electrically-closed Loop of Socket 
       FIG.  13    schematically illustrates the arrangement of outer shield  1 , plural (two) inner shields  3 , and plural (eight) terminals  4  when viewed from below. 
     In socket S 1 , at least plural (three) electrically-closed loops LO 1 , LO 2 , and LO 3  described below are formed. Each of electrically-closed loops LO 1 , LO 2 , and LO 3  includes at least outer shield  1  and one or two inner shields  3  among outer shield  1 , two inner shields  3 , and virtual paths W 7 , W 8 , W 9 , and W 10 . That is, each of electrically-closed loops LO 1 , LO 2 , and LO 3  necessarily includes a path completed in outer shield  1  and a path completed in one inner shield  3  or each of two inner shields  3 , and optionally includes at least one of virtual paths W 7 , W 8 , W 9 , and W 10 . Each of two virtual paths W 7  and W 8  (or W 9  and W 10 ) connects outer shield  1  to respective one of two tip regions r 1  of inner shield  3  by shortest distance L 1 . Each of electrically-closed loops LO 1 , LO 2 , and LO 3  surrounds at least one terminal  4 . Each of electrically-closed loops LO 1 , LO 2 , and LO 3  does not surround other electrically-closed loops. The other electrically-closed loops include at least outer shield  1  and one or two inner shields  3  among the outer shield  1 , two inner shields  3 , and virtual paths W 7 , W 8 , W 9 , and W 10 . Electrically-closed loop LO 1  does not surround electrically-closed loops LO 2  and LO 3 . Electrically-closed loop LO 2  does not surround electrically-closed loops LO 1  and LO 3 . Electrically-closed loop LO 3  does not surround electrically-closed loops LO 1  and LO 2 . 
     In the present disclosure, when one electrically-closed loop (referred to as a first closed loop below) surrounds another electrically-closed loop (referred to as a second closed loop below), a portion of the first closed loop may overlap a portion of the second closed loop. 
     The longest loop length among the loop lengths of electrically-closed loops LO 1 , LO 2 , and LO 3  is shorter than the wavelength of the maximum frequency of a transmission signal flowing through terminal  4 . This configuration reduces resonance of a transmission signal. Here, the maximum frequency refers to the maximum frequency of the transmission signal flowing through high-frequency terminal  4 T. That is, in the exemplary embodiment, the maximum frequency is determined in accordance with the specifications of high-frequency terminal  4 T. 
     Paths W 7  and W 8 , inner shield  3 , and paths W 2 , W 3 , and W 3  along outer shield  1  constitute electrically-closed loop LO 5 . Paths W 9  and W 10 , inner shield  3 , and paths W 2 , W 1 , and W 4  along outer shield  1  constitute electrically-closed loop LO 6 . Thus, outer shield  1 , inner shield  3 , and two of virtual paths W 7  to W 10  constitute plural electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  each passing through outer shield  1 , inner shield  3 , and two of virtual paths W 7  to W 10  and include outer shield  1  and inner shield  3 . Each of electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  surrounds terminal  4 . Electrically-closed loop LO 5  out of plural electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  surrounds electrically-closed loops LO 2  and LO 2  other than electrically-closed loop LO 5  per se. Electrically-closed loop LO 6  out of plural electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  surrounds electrically-closed loops LO 1  and LO 2  other than electrically-closed loop LO 6  per se. Each of one or more particular electrically-closed loops LO 1 , LO 2 , and LO 3  out of plural electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  does not surround any electrically-closed loop out of plural electrically-closed loops LO 1 , LO 2 , LO 3 , LO 5 , and LO 6  other than the each of one or more particular electrically-closed loops LO 1 , LO 2 , and LO 3  per se. The longest loop length of one or more particular electrically-closed loops LO 1 , LO 2 , and LO 3  is shorter than the wavelength of the maximum frequency of a transmission signal flowing through terminal  4 . 
     In the case that the connector includes a single inner shield, two virtual paths are formed at both ends of the single inner shield in total. The two virtual paths, the inner shield, and the outer shield constitute plural electrically-closed loops. 
     In the connector as disclosed in Japanese Patent Laid-Open Publication No. 2013-182808, resonance of the transmission signal transmitted by the connector may occur. 
     In contrast, the connector in the exemplary embodiment reduces the resonance of the transmission signal flowing through terminal  4 . 
     Upon not limiting to a plane perpendicular to up-down direction Dud, electrically-closed loops other than electrically-closed loops LO 1 , LO 2 , and LO 3  are also formed in socket S 1 . However, any of these electrically-closed loops has a loop length which is shorter than the loop lengths of electrically-closed loops LO 1 , LO 2 , and LO 3 , hence not being described here. 
     Paths W 1  to W 10  constituting electrically-closed loops LO 1 , LO 2 , and LO 3  will be described below. 
     Two inner shields  3  are arranged on the front and back parts in socket S 1 . Region r 2  and region r 3  are provided on the left side surface of outer shield  1 . Region r 2  faces tip region r 1  on the left side of the front inner shield  3 . Region r 3  faces tip region r 1  on the left side of back inner shield  3 . Region r 4  and region r 5  are provided on the right side surface of outer shield  1 . Region r 4  faces tip region r 1  on the right side of the front inner shield  3 . Region r 5  faces tip region r 1  on the right side of the back inner shield  3 . 
     Path W 1  is included in the front region of outer shield  1  and connects region r 4  to region r 2  along outer shield  1 . Path W 2  connects region r 2  to region r 3  along the left side surface of outer shield  1 . 
     Path W 3  is included in the back region of outer shield  1  and connects region r 3  to region r 5  along outer shield  1 . Path W 4  connects region r 5  to region r 4  along the right side surface of outer shield  1 . 
     Path W 5  connects two tip regions r 1  of upper inner shield  3  to each other. Path W 6  connects two tip regions r 1  of lower inner shield  3  to each other. 
     Path W 7  connects region r 2  of outer shield  1  to tip region r 1  on the left side of front inner shield  3  by shortest distance L 1 . Path W 8  connects region r 4  of outer shield  1  to tip region r 1  on the right side of front inner shield  3  by shortest distance L 1 . 
     Path W 9  connects region r 3  of outer shield  1  to tip region r 1  on the left side of back inner shield  3  by shortest distance L 1 . Path W 10  connects region r 5  of outer shield  1  to tip region r 1  on the right side of back inner shield  3  by shortest distance L 1 . 
     Electrically-closed loop LO 1  is constituted by paths W 1 , W 7 , W 5 , and W 8 . Electrically-closed loop LO 2  is constituted by paths W 2 , W 9 , W 6 , W 10 , W 4 , W 8 , W 5 , and W 7 . Electrically-closed loop LO 3  is constituted by paths W 3 , W 10 , W 6 , and W 9 . 
     As described above, in the present disclosure, in the case that an electrically-closed loop (first closed loop) surrounds another electrically-closed loop (second closed loop), the portion of the first closed loop may overlap the portion of the second closed loops. For example, in  FIG.  13   , a first closed loop constituted by paths W 4 , W 1 , W 2 , W 9 , W 6 , and W 10  overlaps electrically-closed loop LO 1  as a second closed loop in path W 1 . The first closed loop surrounds the second closed loop. 
     In the exemplary embodiment, the loop length of electrically-closed loop LO 2  is the longest among the loop lengths of electrically-closed loops LO 1 , LO 2 , and LO 3 . The longest loop length ranges, e.g. from about 6 mm to 7 mm. 
     In the case that maximum frequency fMAX of a transmission signal flowing through terminal  4  is 10 GHz (1010 Hz), wavelength λ of maximum frequency fMAX of the transmission signal is expressed as λ=3×10 8 /fMAX=0.03 [m]=30 [mm]. The longest loop length ranging from 6 to 7 [mm] satisfies the condition that the longest loop length is shorter than wavelength λ of maximum frequency fMAX. 
     Outer shield  1  constitutes electrically-closed loop LO 4  surrounding terminal  4  without inner shield  3 . Electrically-closed loop LO 4  is constituted by paths W 1 , W 2 , W 3 , and W 4 . That is, tubular portion  10  (see  FIG.  4   ) of outer shield  1  continuously extending along circumferential direction D 10  constitutes electrically-closed loop LO 4 . Electrically-closed loop LO 4  surrounds electrically-closed loops LO 1 , LO 2 , and LO 3 . 
     Since outer shield  1  has no gap therein along circumferential direction D 10  of tubular portion  10 , outer shield  1  solely constitutes electrically-closed loop LO 4 . Outer shield  1  may constitute electrically-closed loop LO 4  together with conductor  170  and/or  180  of circuit board  150 . That is, in the case that a gap is provided in outer shield  1 , conductor  170  and/or  180  may constitute a path connecting both ends of the gap to each other, and electrically-closed loop LO 4  may include this path. Here, conductor  170  and/or  180  may not necessarily be included in the configuration of socket S 1 . 
     (2.2) Configuration of Header 
     A configuration of header H 1  according to the exemplary embodiment will be described below. Description of components of header H 1  that are similar to those of socket S 1  will be appropriately omitted. 
     Header H 1  is two-fold symmetric with respect to a symmetric axis passing through the center of header H 1  along up-down direction Dud. As illustrated in  FIG.  5   , header H 1  includes outer shield  5 , housing  6 , plural (two) inner shields  7 , and plural (eight) terminals  8 . Each of outer shield  5  and inner shields  7  is an electrostatic shield. Outer shield  5  surrounds plural terminals  8 . That is, outer shield  5  is disposed outside plural terminals  8 . Inner shields  7  are arranged inside outer shield  5 . Inner shields  7  are arranged inside housing  6 . 
     Circuit board  550  (see  FIG.  9   ) is mechanically and electrically connected to header H 1 . Circuit board  550  includes substrate  560  (see  FIG.  9   ) and conductors  570  and  580  (see  FIG.  9   ) as components similar to substrate  160  and conductors  170  and  180  of circuit board  150  connected to socket S 1 . For example, conductor  570  is provided on substantially the entire surface of substrate  560  on the side on which header H 1  is connected. In  FIG.  6   , a region in which conductor (solder)  580  is provided is denoted by a two-dot chain line. 
     (2.2.1) Housing of Header 
     Housing  6  is made of a molded resin. Housing  6  has electrical insulating properties. Housing  6  includes bottom wall  61  and peripheral wall  62 . Bottom wall  61  has a rectangular shape in which the length thereof in front-back direction Dfb is longer than the length thereof in left-right direction Dlr in a plan view. Peripheral wall  62  protrudes from the outer circumferential portion of one surface (lower surface) of bottom wall  61  in downward direction Dd, i.e., a thickness direction of the bottom wall. The left side surface and the right side surface of housing  6  have plural notches  601  (two on the left side surface and two on the right side surface in  FIG.  5   ) penetrating bottom wall  61  and peripheral wall  62  in up-down direction Dud. Plural notches  601  are provided at positions facing board connection portions  83  of terminals  8  when viewed in up-down direction Dud (see  FIG.  6   ). 
     As illustrated in  FIG.  7   , housing  6  further includes two wall portions  65 . Each of wall portions  65  protrudes from bottom wall  61  in downward direction Dd. Wall portion  65  has a rectangular parallelepiped shape having a cylindrical lower surface (see  FIG.  10   ). The front end and the back end of wall portion  65  are connected to peripheral wall  62 . When viewed in up-down direction Dud, wall portion  65  is longer in front-back direction Dfb than in left-right direction Dlr. That is, wall portion  65  has a thickness in the direction along left-right direction Dlr. Two wall portions  65  are arranged in left-right direction Dlr. 
     Each of wall portions  65  includes plural (two) accommodation portions  68 . Each of extensions  72  of inner shield  7  is accommodated in respective one of plural accommodation portions  68 . Each of accommodation portions  68  is a through-hole provided in wall portion  65 . Accommodation portion  68  passes through wall portion  65  in up-down direction Dud. Accommodation portion  68  also penetrates bottom wall  61  in up-down direction Dud. When viewed in up-down direction Dud, accommodation portions  68  provided in wall portion  65  are recesses penetrating from the side surface (surface intersecting in left-right direction Dlr) of wall portion  65 . 
     Each of wall portions  65  includes plural (four) terminal holders  69 . Each of terminal  8  is held by respective one of terminal holders  69 . Each terminal holder  69  is a dent provided in wall portion  65 . 
     Plural terminals  8  are insert-molded with housing  6 . In the exemplary embodiment, eight terminals  8  are fixed to housing  6 . Each of eight terminals  8  of header H 1  corresponds to respective one of eight terminals  4  of socket S 1 . Each of terminals  8  is disposed at a position to be connected to corresponding one of terminals  4 . 
     As illustrated in  FIGS.  5  and  6   , bottom wall  61  has plural (two) accommodation grooves  613  provided therein. Each of accommodation grooves  613  is a groove provided in the upper surface of bottom wall  61 . Accommodation groove  613  is longer in left-right direction Dlr than in front-back direction Dfb. Accommodation groove  613  accommodates base  71  of inner shield  7  therein. 
     As illustrated in  FIG.  7   , peripheral wall  62  includes plural (two) insertion portions  623 . Each of plural (two) insertion portions  623  is a recess provided in the bottom surface (lower surface) of peripheral wall  62 . As described later, shield protrusion  54  which is a portion of outer shield  5  is inserted into each of plural (two) of insertion portions  623 . 
     (2.2.2) Outer Shield of Header 
     Outer shield  5  surrounds plural terminals  8  and plural inner shields  7 . Outer shield  5  contains metal as a main material or a material forming the surface, such as plating. Here, outer shield  5  is made of metal as the main material. As illustrated in  FIGS.  5  and  8   , outer shield  5  includes outer peripheral wall  51 , plural (four) top walls  52 , plural (two) shield protrusions  54 , and bottom wall  55 . 
     Outer peripheral wall  51  has a rectangular tubular shape with a rectangular cross section. Outer peripheral wall  51  includes two outer peripheral walls  511  and two outer peripheral walls  512 . Two outer peripheral walls  511  are portions of outer peripheral wall  51 , and extend substantially in front-back direction Dfb. Two outer peripheral walls  511  face each other in left-right direction Dlr. Two outer peripheral walls  512  are portions of outer peripheral wall  51 , and extend substantially in left-right direction Dlr. Two outer peripheral walls  512  face each other in front-back direction Dfb. Each of two outer peripheral walls  512  connects the ends of two outer peripheral walls  511  to each other. 
     Outer shield  5  further includes plural protrusions  56  that protrude from outer peripheral wall  51 . Protrusions  56  function as contact portions configured to contact outer shield  1  of the mating connector (here, socket S 1 ). Outer peripheral wall  51 , top wall  52 , and protrusions  56  constitute tubular portion  50  having both ends which are open in up-down direction Dud. That is, tubular portion  50  includes outer peripheral wall  51 , top wall  52 , and plural protrusions  56 . Outer circumferential surface  501  of tubular portion  50  includes a portion of the outer circumferential surface of outer peripheral wall  51  and surfaces of protrusions  56 . Tubular portion  50  surrounds hollow space  50 S. 
     Outer shield  5  of the connector (here, header H 1 ) has a side surface (outer circumferential surface  501 ) in up-down direction Dud. The side surface (outer circumferential surface  501 ) has a protruding structure. That is, a structure formed by plural protrusions  56  corresponds to the protruding structure. Outer shield  5  of the connector (here, header H 1 ) contacts outer shield  1  of the mating connector (here, socket S 1 ) at the protruding structure (plural protrusions  56 ). More specifically, protrusions  56  contact inner circumferential surface  103  of tubular portion  10  of outer shield  1  (see  FIG.  10   ). 
     In comparison to a connector where outer circumferential surface  501  is flat without protrusions  56 , outer shield  1  of the connector according to the embodiment may be pushed into outer shield  5  even though the dimensions of outer shields  1  and  5  have variations. This configuration reduces poor contact occurring such that outer shields  1  and  5  contact each other in one direction in left-right direction Dlr or one direction in front-back direction Dfb and are separated from each other in the other directions. 
     Each of two outer peripheral walls  511  includes three protrusions  56 . One protrusion  56  is provided on two outer peripheral walls  512 . Plural protrusions  56  are spaced from each other along circumferential direction D 50  (see  FIG.  8   ) surrounding hollow space  50 S of tubular portion  50 . The maximum value of creepage distances L 2  and L 3  between plural protrusions  56  is equal to or less than ¼ of wavelength λ of the maximum frequency of a transmission signal flowing through terminal  8 . This configuration reduces noise leaking from a region between plural protrusions  56  (region of outer shield  5  that is not electrically connected to outer shield  1 ). Here, creepage distance L 2  between protrusion  56  provided on outer peripheral wall  511  and protrusion  56  provided on outer peripheral wall  512  is larger than creepage distance L 3  between plural protrusions  56  provided on outer peripheral wall  511 . That is, the maximum value of the creepage distance between plural protrusions  56  is creepage distance L 2 . Here, the maximum frequency refers to the maximum frequency of the transmission signal flowing through high-frequency terminal  8 T among plural terminals  8 . That is, in the exemplary embodiment, the maximum frequency is determined in accordance with the specifications of the high-frequency terminal  8 T. 
     Each of plural (four) top walls  52  has an L-shape when viewed in up-down direction Dud. Plural (four) top walls  52  are connected to the lower ends of the four corners of outer peripheral wall  51 , and extend toward the inside of outer peripheral wall  51  when viewed in up-down direction Dud. 
     Bottom wall  55  has a rectangular frame shape when viewed in up-down direction Dud. Bottom wall  55  is connected to the upper end of outer peripheral wall  51  and extends toward the outside of outer peripheral wall  51  when viewed in up-down direction Dud. The lower surface of bottom wall  55  extends in front-back direction Dfb and left-right direction Dlr, that is, parallel to a plane perpendicular to up-down direction Dud. 
     The inner circumferential surface of outer peripheral wall  51  corresponds to inner circumferential surface  503  of tubular portion  50 . Outer shield  5  has distal end surface  502 . Distal end surface  502  is provided at one end (lower end) of tubular portion  50  among both the ends of tubular portion  50  in up-down direction Dud. The one end is on the mating connector side when the connector (here, header H 1 ) and the mating connector (here, socket S 1 ) are transitioned from the disconnected state to the connected state. Distal end surface  502  extends along the inner edge of tubular portion  50 . Here, the upper surface of top wall  52  corresponds to distal end surface  502 . The inner edge of distal end surface  502  corresponds to a portion of the inner edge of tubular portion  50  at the lower end of tubular portion  50 . 
     Boundary b 3  between distal end surface  502  and outer circumferential surface  501  is an arcuate surface when viewed from front-back direction Dfb (see  FIG.  9   ). Here, distal end surface  502  is defined as a region of the outer surface of tubular portion  50 , and forms an acute angle with respect to up-down direction Dud which is equal to or larger than 0 degrees and smaller than 45 degrees. An outer surface of tubular portion  50  forming an acute angle of 45 degrees or larger is defined as outer circumferential surface  501 . Boundary b 3  has a predetermined length along circumferential direction D 50  of tubular portion  50 . 
     Each of plural (two) shield protrusions  54  corresponds to respective one of two of plural (four) top walls  52 . Each of shield protrusions  54  protrudes upward from the corresponding top wall  52 . Each of plural (two) of shield protrusions  54  corresponds to respective one of plural (two) of insertion portions  623  (see  FIG.  7   ) provided in housing  6 . Each of shield protrusions  54  is inserted into corresponding one of insertion portions  623 . 
     Outer shield  5  is fixed to housing  6  by press fitting. That is, outer shield  5  is held in housing  6  by being pushed into housing  6  in one direction (upward). At this moment, plural top walls  52  of outer shield  5  cover at least a portion of peripheral wall  62  of housing  6 . At this moment, each of shield protrusions  54  is inserted into corresponding insertion portion  623 . 
     The entire surface of outer shield  5  is seamlessly formed. In the exemplary embodiment, at least outer circumferential surface  501  and inner circumferential surface  503  among the surfaces of outer shield  5  are seamless over the entirety of tubular portion  50  along circumferential direction D 50  (that is, there are no seams or breaks). 
     As illustrated in  FIG.  8   , outer circumferential surface  501  includes outer surface  5110  and outer surface  5120 . Outer surface  5110  includes the surface of outer peripheral wall  511  and the surface of protrusion  56 , and corresponds to each of two outer peripheral walls  511 . Outer surface  5120  includes the surface of outer peripheral wall  512  and the surface of protrusion  56 , and corresponds to each of two outer peripheral walls  512 . Each of outer surface  5110  and outer surface  5120  is seamless. Outer surface  5110  and outer surface  5120  having different normal directions are seamlessly connected to each other. Outer circumferential surface  501  is thus seamless over the entirety of tubular portion  50  along circumferential direction D 50 . 
     As illustrated in  FIG.  8   , inner circumferential surface  503  includes inner surface  5111  of each of two outer peripheral walls  511  and inner surface  5121  of each of two outer peripheral walls  512 . Each of inner surface  5111  and inner surface  5121  is seamless. Inner surface  5111  and inner surface  5121  having different normal directions, re seamlessly connected to each other. Inner circumferential surface  503  is thus seamless over the entirety of tubular portion  50  along circumferential direction D 50 . 
     Boundary b 3  between outer circumferential surface  501  and distal end surface  502  is seamless. For example, at the upper right (corner portion of outer shield  5 ) of the surface of paper in  FIG.  8   , outer surface  5110 , outer surface  5120 , and distal end surface  502  having different normal directions are seamlessly connected. 
     (2.2.3) Inner Shield of Header 
     In the exemplary embodiment, two inner shields  7  have the same shape. Inner shield  7  contains metal as a main material or a material forming the surface, such as plating. Here, inner shield  7  is made of metal as main material. As illustrated in  FIG.  9   , inner shield  7  includes base  71  and plural (two) extensions  72 . 
     Base  71  has a length in left-right direction Dlr. Base  71  has a plate shape. When viewed in the thickness direction (front-back direction Dfb) of base  71 , base  71  is longer in left-right direction Dlr than in up-down direction Dud. Base  71  is accommodated in accommodation groove  613  provided in bottom wall  61  of housing  6 . 
     Plural extensions  72  protrude downward from base  71 . That is, plural extensions  72  protrude in up-down direction Dud to be directed to the mating connector side when the connector (here, header H 1 ) and the mating connector (here, socket S 1 ) are transitioned from the disconnected state to the connected state. Each of extensions  72  has a rectangular plate shape. When viewed in the thickness direction (front-back direction Dfb) of each of extensions  72 , each of extensions  72  is longer in up-down direction Dud than in left-right direction Dlr. The thickness direction of extension  72  may be left-right direction Dlr. 
     Extension  72  includes contacting portion  720  (contact surface) configured to contact inner shield  3  of the mating connector (socket S 1 ). Contacting portion  720  is provided on a surface (here, left surface or right surface) of extension  72  in the longitudinal direction of extension  72 . Contacting portions  720  of two extensions  72  are directed in opposite directions (rightward direction Dr and leftward direction D 1 ). 
     Header H 1  includes two extensions  72  on each of two inner shields  7 . That is, header H 1  includes four extensions  72  in total. Each of four accommodation portions  68  (see  FIG.  7   ) provided in housing  6  corresponds to respective one of four extensions  72 . Each of extensions  72  is accommodated in corresponding accommodation portion  68 . 
     Inner shield  7  is fixed to housing  6  by press fitting. That is, inner shield  7  is held in housing  6  by being pushed into housing  6  in one direction (downward). At this moment, each of extensions  72  is accommodated in corresponding accommodation portion  68 . Here, the accommodation space of each of two extensions  72  in the shield holder (accommodation portion  68 ) is larger than each of two extensions  72 . 
     As illustrated in  FIG.  9   , base  71  of inner shield  7  is located at the upper end of header H 1 . Here, outer shield  5  has end e 5  and end e 6 . End e 5  is an end (lower end) that is on the mating connector side when the connector (here, header H 1 ) and the mating connector (here, socket S 1 ) are transitioned from the disconnected state to the connected state. End e 6  is an end (upper end) opposite to end e 5 . Here, end e 6  covers the entire circumference along circumferential direction D 50  that surrounds hollow space  50 S of bottom wall  55  of outer shield  5 . Outer shield  5  faces two tip regions r 7  of inner shield  7  in a region including end e 6 . 
     Outer shield  5  faces at least one of two tip regions r 7  with gap g 7 , in the region including end e 6 . As illustrated in  FIG.  9   , conductors  570  and  580  of circuit board  550  are electrically connected to outer shield  5 . Conductors  570  and  580  are provided to bridge end e 6  of outer shield  5  over two tip regions r 7  of inner shield  7 , respectively. That is, outer shield  5  is electrically connected to inner shield  7  through conductors  570  and  580 . While circuit board  550  is not provided, outer shield  5  is electrically insulated from at least one (both in the exemplary embodiment) of two tip regions r 7  via gap g 7 . Shortest distance L 7  between outer shield  5  and at least one of two tip regions r 7  in gap g 7  is equal to or greater than 0.01 mm and equal to or less than 0.1 mm. 
     Inner shield  7  has end e 7  and end e 8 . End e 7  is an end (lower end) that is on the mating connector side when the connector (here, header H 1 ) and the mating connector (here, socket S 1 ) are transitioned from the disconnected state to the connected state. End e 8  is an end (upper end) opposite to end e 7 . Inner shield  7  has connection surface  710  (upper surface) at end e 8 . Connection surface  710  is configured to be electrically connected to circuit board  550 . Connection surface  710  is flat and continuously extends over two tip regions r 7 . More specifically, connection surface  710  has a rectangular flat surface connecting two tip regions r 7  to each other. 
     (2.2.4) Terminal of Header 
     As illustrated in  FIGS.  6  and  7   , plural (eight) terminals  8  include plural (six) low-frequency terminals  8 P and plural (two) high-frequency terminals  8 T. The arrangement of plurality of terminals  8  is similar to the arrangement of plurality of terminals  4  of socket S 1 . That is, the content described in the section of “(2.1.4.1) Arrangement” is also applied to plural terminals  8 . 
     Terminals  8  have the same shape. Terminals  8  are formed by, for example, punching and bending a metal plate. As illustrated in  FIG.  11   , each of terminals  8  includes contact portion  81 , winding tongue  82 , board connection portion  83 , and contact portion  84 . 
     Board connection portion  83  is configured to be electrically connected to, for example, conductor  580  (solder) of circuit board  550 . That is, board connection portion  83  is bonded to circuit board  550  by, e.g. soldering. Thus, circuit board  550  is electrically and mechanically connected to terminals  8 . As illustrated in  FIG.  6   , board connection portion  83  is surrounded by outer shield  5  when viewed in up-down direction Dud. At least a portion of board connection portion  83  and at least a portion of outer shield  5  are flush on one plane perpendicular to up-down direction Dud. 
     Contact portion  81  and contact portion  84  have lengths in up-down direction Dud. Contact portion  81  is configured to contact contact portion  41  of terminal  4  of socket S 1 . Contact portion  84  is configured to contact contact portion  46  of terminal  4  of socket S 1 . Winding tongue  82  has a U-shape opening in upward direction Du. Winding tongue  82  joins the lower end portion of contact portion  81  to the lower end portion of contact portion  84 . Board connection portion  83  protrudes from the upper end portion of contact portion  81 . 
     While terminal  8  is held in housing  6 , at least a portion of contact portion  81  and contact portion  84  is exposed when viewed from below. Contact portion  81  and contact portion  84  contact corresponding terminals  4  among plural terminals  4  (mating terminals) of socket S 1  (mating connector) to be electrically connected to terminal  4  (see  FIG.  12   ). 
     Terminal  8  further includes force-sensing portion  85 . Force-sensing portion  85  generates a click feeling when terminal  8  contacts terminal  4  (mating terminal). Force-sensing portion  85  is a protrusion that protrudes from contact portion  81 . Upon moving over force-sensing portion  47  of terminal  4 , force-sensing portion (protrusion)  85  generates a click feeling. 
     Contact portion  84  has dent  840  in a contact surface of contact portion  84  contacting contact portion  46 . That is, contact portion  46  is inserted into dent  840 . Here, contact portion  46  contacts a side surface of dent  840 . 
     As illustrated in  FIG.  7   , contacting portion  720  of inner shield  7  and contact portion  81  of at least one of plural terminals  8  are arranged in front-back direction Dfb. 
     (2.2.5) Circuit Board on Header Side 
     Header H 1  is configured to be electrically connected to conductor  580  (solder) on circuit board  550 . In  FIG.  6   , a region in which conductor  580  is provided on the upper surface of header H 1  is denoted by a two-dot chain line. The arrangement and the electrical connection relation of conductors  570  and  580  of circuit board  550 , outer shield  5 , plural inner shields  7 , and plural terminals  8  are similar to the arrangement and the electrical connection relation of conductors  170  and  180  of circuit board  150 , outer shield  1 , plural inner shields  3 , and plural terminals  4  of socket S 1 . 
     (2.2.6) Electrically-Closed Loop of Header 
     The arrangement of outer shield  5 , plural (two) inner shields  7 , and plural (eight) terminals  8  of header H 1  is similar to the arrangement of outer shield  1 , plural (two) inner shields  3 , and plural (eight) terminals  4  of socket S 1  which is illustrated in  FIG.  13   . Therefore, in header H 1 , similar to socket S 1 , at least plural (three) electrically-closed loops LO 1 , LO 2 , and LO 3  are formed. The details regarding electrically-closed loops LO 1 , LO 2 , and LO 3  of header H 1  are similar to the details regarding electrically-closed loops LO 1 , LO 2 , and LO 3  of socket S 1 . Outer shield  5  constitutes electrically-closed loop LO 4  surrounding terminal  8  without inner shield  7 , similar to outer shield  1 . 
     Here, since outer shield  5  has no gap along circumferential direction D 50  of tubular portion  50 , outer shield  5  solely constitutes electrically-closed loop LO 4 . Outer shield  5  may constitute electrically-closed loop LO 4  together with conductor  570  and/or  580  of circuit board  550 . That is, in the case that a gap is formed in outer shield  5 , conductor  570  and/or  580  may constitutes a path connecting both ends of the gap to each other, and electrically-closed loop LO 4  may include this path. Here, conductor  570  and/or  580  may not necessarily be included in the configuration of header H 1 . 
     (3) Assembling Process 
     Processes of connecting socket S 1  to header H 1  so as to assemble connector device  100  will be described below with reference to  FIGS.  9  to  12   . 
     Circuit board  150  is mechanically and electrically connected to socket S 1 . Circuit board  550  is mechanically and electrically connected to header H 1 . In this state, as illustrated in  FIGS.  9  and  11   , socket S 1  is disposed below header H 1 . At least one of the upward movement of socket S 1  and the downward movement of header H 1  is performed. Thus, as illustrated in  FIGS.  10  and  12   , socket S 1  and header H 1  are mechanically connected. As illustrated in  FIG.  10   , inner shield  3  of socket S 1  and inner shield  7  of header H 1  contact each other and are electrically connected to each other. As illustrated in  FIG.  12   , plural terminals  4  of socket S 1  and plurality of terminals  8  of header H 1  contact each other and are electrically connected to each other. As illustrated in  FIGS.  10  and  12   , outer shield  1  of socket S 1  and outer shield  5  of header H 1  contact each other and are electrically connected to each other. As illustrated in  FIG.  10   , two wall portions  65  of housing  6  of header H 1  are inserted into a space between wall portion  25  and wall portion  26  of housing  2  of socket S 1  and a space between wall portion  26  and wall portion  27 . 
     Here, when socket S 1  and header H 1  (connector and the mating connector) are transitioned from the disconnected state to the connected state, the components of socket S 1  and the components of header H 1  contact each other in the following order. 
     First, socket S 1  contacts header H 1  at outer shields  1  and  5 . That is, a region of socket S 1  near the upper end of inner circumferential surface  103  of tubular portion  10  of outer shield  1  contacts a region of header H 1  near the lower end of outer circumferential surface  501  of tubular portion  50  of outer shield  5 . 
     Then, socket S 1  contacts header H 1  at terminals  4  and  8 . That is, at least one of a case where contact portion  41  contacts contact portion  81  and a case where contact portion  46  contacts contact portion  84  is performed. 
     Then, socket S 1  contacts header H 1  at inner shields  3  and  7 . That is, contacting portion  332  of inner shield  3  contacts contacting portion  720  of inner shield  7 . 
     Then, force-sensing portion  47  (or  85 ) of the connector (socket S 1  or header H 1 ) contacts the mating terminal (terminal  8  or  4 ). That is, at least one of a case where force-sensing portion  47  contacts contact portion  81  of terminal  8  and a case where force-sensing portion  85  contacts contact portion  41  of terminal  4  is performed. The force-sensing portions  47  and  85  generate a click feeling. 
     Then, outer shield  5  of the connector (here, header H 1 ) contact outer shield  1  of the mating connector (here, socket S 1 ) at the protruding structure (plural protrusions  56  also referred to as contact portions). That is, plural protrusions  56  contact inner circumferential surface  103  of tubular portion  10  of outer shield  1  (see  FIG.  10   ). More specifically, firstly, plural protrusions  56  contact the region near the upper end of inner circumferential surface  103 . Then, contact pressure between each protrusion  56  and inner circumferential surface  103  further moves plural protrusions  56  down while outer shield  1  elastically deforms so that inner peripheral wall  13  of outer shield  1  is directed toward the outer side (outer peripheral wall  11  side). Finally, as illustrated in  FIG.  10   , plural protrusions  56  contact a region of inner circumferential surface  103  along up-down direction Dud. Socket S 1  is thus connected to header H 1 . 
     As described above, a click feeling is generated at terminals  4  and  8  before the contact pressure and a frictional force between outer shields  1  and  5  increases by plural protrusions  56  contacting outer shield  1 . Therefore, the worker can perceive the click feeling more easily than a connector where the click feeling is generated after plural protrusions  56  contact outer shield  1 , thus preventing the click feeling by the frictional force from being perceived. The positional relation between outer shields  1  and  5  fixed by plural protrusions  56  contacting outer shield  1  is not changed in the subsequent processes, and thus, improves the positioning accuracy, accordingly, securing the contact area between outer shields  1  and  5 . 
     (4) Noise Level 
     The solid line in  FIG.  14    represents the analysis result of radiation noise of connector device  100  in the exemplary embodiment. The broken line in  FIG.  14    represents the analysis result of the radiation noise of a comparative example of a connector device. The horizontal axis represents a frequency [GHz]. The vertical axis represents the noise level ([dBμV/m]). 
     The comparative example of the connector device is different from connector device  100  in the exemplary embodiment in that each of outer shields  1  and  5  is formed by bending a metal plate. Other components of the connector device in the comparative example are the same as those in connector device  100  in the exemplary embodiment. Therefore, there are seams or breaks in circumferential direction D 10  (D 50 ) of tubular portion  10  ( 50 ), for example, on the outer circumferential surface and the inner circumferential surface of tubular portion  10  ( 50 ) of each of outer shields  1  and  5  of the connector device in the comparative example. On the other hand, in connector device  100  in the exemplary embodiment, each of outer shields  1  and  5  is formed by drawing a metal. Therefore, the outer circumferential surface and the inner circumferential surface of tubular portion  10  ( 50 ) of each of outer shields  1  and  5  are seamlessly formed over the entire circumference of tubular portion  10  ( 50 ) along circumferential direction D 10  (D 50 ), so that there are no seams or breaks therein. 
     As illustrated in  FIG.  14   , the noise level of connector device  100  in the exemplary embodiment is lower than that of the comparative example of the connector device at each frequency. That is, in comparison to the comparative example, in the exemplary embodiment, since the seams of outer shields  1  and  5  are removed, not only an effect of suppressing the influence of resonance, but also an effect of reducing the noise radiated from the seams are obtained. 
     Modification Example 1 
     Socket S 2  and header H 2  according to modification example 1 will be described below with reference to  FIGS.  15  to  18   . Components similar to those in the exemplary embodiment are denoted by the same reference numerals, and the description thereof will be omitted. In  FIGS.  15  and  17   , regions in which the conductors (solder)  180  and  580  are provided are indicated by two-dot chain lines. 
     As illustrated in  FIGS.  15  and  16   , socket S 2  includes only one inner shield  3 . Socket S 2  includes only two terminals  4 . Thus, the shapes of outer shield  1 A and housing  2 A are different from the shapes of outer shield  1  and housing  2  in the exemplary embodiment. These configurations will be detailed below. 
     Housing  2 A schematically has a shape in which the region in which six low-frequency terminals  4 P are provided is omitted from housing  2  in the exemplary embodiment. Outer shield  1 A schematically has a shape in which the region in which six low-frequency terminals  4 P are provided is omitted from outer shield  1  in the exemplary embodiment. 
     Each of wall portion  25 , wall portion  26 , and wall portion  27  of housing  2  includes one accommodation portion  28 . Three extensions  32  of inner shield  3  are accommodated in three accommodation portions  28 , respectively. 
     Each of wall portion  25  and wall portion  27  includes one terminal holder  29 . Wall portion  26  includes two terminal holders  29 . One of two terminals  4  is held by terminal holder  29  of wall portion  25  and one terminal holder  29  of wall portion  26 . The other of two terminals  4  is held by terminal holder  29  of wall portion  27  and the other terminal holder  29  of wall portion  26 . 
     Two terminals  4  are high-frequency terminals  4 T, but the present disclosure is not limited to this. At least one of two terminals  4  may be low-frequency terminal  4 P. 
     Two high-frequency terminals  4 T are arranged on both sides (front side and back side) of inner shield  3 . Therefore, similarly to the exemplary embodiment, it is possible to reduce noise propagation between two high-frequency terminals  4 T. 
     As illustrated in  FIGS.  17  and  18   , header H 2  includes only one inner shield  7 . Header H 2  includes only two terminals  8 . Thus, the shapes of outer shield  5 A and housing  6 A are different from the shapes of outer shield  5  and housing  6  in the exemplary embodiment. These configurations will be detailed below. 
     Housing  6 A schematically has a shape in which the region in which six low-frequency terminals  8 P are provided is omitted from housing  6  in the exemplary embodiment. Outer shield  5 A schematically has a shape in which the region in which six low-frequency terminals  8 P are provided is omitted from outer shield  5  in the exemplary embodiment. 
     Each of two wall portions  65  of housing  6  includes one accommodation portion  68 . Two extensions  72  of inner shield  7  are accommodated in two accommodation portions  68 , respectively. 
     Each of two wall portions  65  includes one terminal holder  69 . Terminal  8  is held by terminal holder  69 . 
     Two terminals  8  are high-frequency terminals  8 T, but the present disclosure is not limited to this. At least one of two terminals  8  may be low-frequency terminal  8 P. 
     Two high-frequency terminals  8 T are arranged on both sides (front side and back side) of inner shield  7 . Therefore, similarly to the exemplary embodiment, it is possible to reduce the possibility of the noise propagation between the two high-frequency terminals  8 T. 
     Modification Example 2 
     Socket S 1  and header H 1  according to modification example 2 will be described below with reference to  FIGS.  19  and  20   . Components similar to those in the exemplary embodiment are denoted by the same reference numerals, and their description thereof will be omitted. In  FIGS.  19  and  20   , only two high-frequency terminals  4 T and two high-frequency terminals  8 T in socket S 1  and header H 1  are extracted and illustrated. 
     In socket S 1  of modification example 2, low-frequency terminal  4 P has a different shape from high-frequency terminal  4 T. In header H 1 , low-frequency terminal  8 P has a different shape from high-frequency terminal  8 T. 
     That is, socket S 1  of modification example 2 includes plural terminals  4 . Header H 1  includes plural terminals  8 . Plural terminals  4  (or  8 ) include a first terminal (low-frequency terminal  4 P or  8 P) and a second terminal (high-frequency terminal  4 T or  8 T). The second terminal has a shape different from the first terminal. Inner shield  3  (or  7 ) is disposed between the first terminal and the second terminal (see  FIG.  13   ). 
     For example, low-frequency terminal  4 P has a shape similar to the shape of low-frequency terminal  4 P in the exemplary embodiment. For example, low-frequency terminal  8 P has a shape similar to the shape of the low-frequency terminal  8 P in the exemplary embodiment. 
     For example, high-frequency terminal  4 T of modification example 2 includes two contact portions  41 , base  42 , and board connection portion  45 , as illustrated in  FIG.  19   . High-frequency terminal  4 T is formed by, for example, punching and bending a metal plate. 
     Base  42  is has a U-shape opening in upward direction Du. Board connection portion  45  is connected to the lower end portion of base  42 . One contact portion  41  protrudes from the left end of base  42  in front-back direction Dfb. The other contact portion  41  protrudes from the right end of base  42  in front-back direction Dfb. 
     For example, high-frequency terminal  8 T includes two contact portions  81 , base  86 , and board connection portion  83 , as illustrated in  FIG.  19   . High-frequency terminal  8 T is formed by, for example, punching and bending a metal plate. 
     Base  86  has a U-shape opening in downward direction Dd. Board connection portion  83  is connected to the upper end portion of the base  86 . One contact portion  81  protrudes from the left end of the base  86  in leftward direction D 1 . The other contact portion  81  protrudes from the right end of the base  86  in rightward direction Dr. 
     In a process for connecting socket S 1  to header H 1 , as illustrated in  FIG.  20   , each high-frequency terminal  4 T is connected to corresponding high-frequency terminal  8 T. That is, high-frequency terminal  8 T is inserted between two contact portions  41  of high-frequency terminal  4 T. Thus, each of the two contact portions  41  contacts corresponding contact portion  81 . At this moment, the distance between two contact portions  41  in left-right direction Dlr increase. 
     Terminals  4  and  8  may have shapes described below. Since low-frequency terminal  4 P ( 8 P) may be connected to a power supply wiring and the ground, low-frequency terminal may have a width larger than the width of high-frequency terminal  4 T ( 8 T) so as to have low resistance. The contact area between low-frequency terminal  4 P and low-frequency terminal  8 P may be larger than the contact area between high-frequency terminal  4 T and high-frequency terminal  8 T so that low-frequency terminals  4 P and  8 P have low resistance. In order to allow a high-speed signal to pass, high-frequency terminal  4 T ( 8 T) may have a shape providing high-frequency terminal with a characteristic impedance matching with the characteristic impedance of a signal line formed on circuit board  150  ( 550 ). 
     Only one of socket S 1  and header H 1  may include low-frequency terminal  4 P ( 8 P) and high-frequency terminal  4 T ( 8 T) having shapes different form each other. 
     Other Modification Examples of Exemplary Embodiment 
     Other modification examples of the exemplary embodiment will be described below. The following modification examples may be realized in appropriate combinations. The following modification examples may be realized in appropriate combination with the above-described first modification example. 
     Outer shield  1  ( 5 ) and inner shield  3  ( 7 ) are not necessarily connected electrically to each other through conductor  180  ( 580 ) of circuit board  150  ( 550 ). Outer shield  1  ( 5 ) and inner shield  3  ( 7 ) may be electrically connected to each other through another conductive member. 
     At least one of outer shield  1  ( 5 ), plural inner shields  3  ( 7 ), and plural of terminals  4  ( 8 ) may contact conductor  170  ( 570 ), thereby being electrically connected to conductor  170  ( 570 ). 
     As illustrated in  FIG.  21   , in socket S 1 , at least one (both in  FIG.  21   ) of two tip regions r 1  of inner shield  3  may be directly connected to outer shield  1 . Similarly, in header H 1 , at least one of two tip regions r 7  of inner shield  7  may be directly connected to outer shield  5 . For example, the length of inner shield  3  ( 7 ) may be larger in comparison to that in the exemplary embodiment, and thus inner shield  3  ( 7 ) may be connected to outer shield  1  ( 5 ) by, e.g. welding, press fitting or caulking. Alternatively, a portion of inner shield  3  ( 7 ) including tip region r 1  (r 7 ) and at least a portion of outer shield  1  ( 5 ) may be made of one member. Inner shield  3  ( 7 ) may be seamlessly connected to outer shield  1  ( 5 ). 
     Extension  32  (or  72 ) does not necessarily protrude from base  31  (or  71 ) in up-down direction Dud. For example, extension  32  (or  72 ) may protrude from base  31  (or  71 ) in front-back direction Dfb. 
     The number of the components of the connector in the exemplary embodiment is just an example, and is not limited to the number described in the exemplary embodiment. For example, the number of extensions  32  ( 72 ) of inner shield  3  ( 7 ) may be appropriately changed. The number of terminals  4  ( 8 ) of each of the connectors (socket S 1  and header H 1 ) may be appropriately changed. Each of the connector may include only low-frequency terminal  4 P ( 8 P) out of terminal  4  ( 8 ), or may include only high-frequency terminal  4 T ( 8 T) out of terminal  4  ( 8 ). 
     The portion formed as the recess or the dent in the exemplary embodiment may be appropriately replaced with a through-hole. On the contrary, the portion formed as a through-hole in the exemplary embodiment may be appropriately replaced with a recess or a dent. 
     In the exemplary embodiment, the portions coupled by press fitting may be coupled by insert molding. On the contrary, in the exemplary embodiment, the portions coupled by insert molding may be coupled by press fitting. Instead of press fitting or insert molding, another bonding method, such as bonding, welding, or caulking may be adopted. 
     Outer shields  1  and  5  are formed by, for example, molding instead of drawing. Thus, at least a portion (for example, entirety of the outer circumferential surfaces  101  and  501 ) of the surfaces of outer shields  1  and  5  may be seamlessly formed. For example, at least a portion of the surfaces of outer shields  1  and  5  may be seamlessly formed by welding. 
     Plural protrusions  56  of outer shield  5  may be provided on inner circumferential surface  503  instead of outer circumferential surface  501  of tubular portion  50 . 
     A portion of the configuration of socket S 1  in the exemplary embodiment may be appropriately applied to header H 1 . On the contrary, a portion of the configuration of header H 1  in the exemplary embodiment may be appropriately applied to socket S 1 . For example, plural protrusions  56  may be provided on both outer shields  1  and  5 , or may be provided only on outer shield  1  among outer shields  1  and  5 . 
     In the exemplary embodiment, terms, such as the up-down direction, the front-back direction, and the left-right direction, indicating directions indicate relative directions determined only by the relative positional relation between constituent members of the connector and the mating connector, and do not indicate absolute directions such as a vertical direction. 
     Overview 
     The following aspects are disclosed from the exemplary embodiment described above. 
     According to a first aspect, the connector (socket S 1  or S 2 , or header H 1  or H 2 ) includes plural terminals ( 4  or  8 ). Each of the terminals ( 4  or  8 ) are electrically connected to respective one of mating terminals of a mating connector. The connector further includes a housing ( 2  or  2 A, or  6  or  6 A) and inner shield ( 3  or  7 ). The housing ( 2  or  2 A, or  6  or  6 A) holds the terminals ( 4  or  8 ). The connector and the mating connector are connected to each other by moving at least one toward the other in a first direction (up-down direction Dud). The terminals ( 4  or  8 ) includes two terminals ( 4  or  8 ). The two terminals ( 4  or  8 ) are arranged on both sides of the inner shield ( 3  or  7 ) in a second direction (front-back direction Dfb) perpendicular to the first direction. The inner shield ( 3  or  7 ) includes the base ( 31  or  71 ) and the extension ( 32  or  72 ). The base ( 31  or  71 ) has a length in a third direction (left-right direction Dlr) perpendicular to the first and second directions. The extension ( 32  or  72 ) protrudes from the base ( 31  or  71 ). The housing ( 2  or  2 A, or  6  or  6 A) includes a shield holder (accommodation portion  28  or  68 ). The shield holder (accommodation portion  28  or  68 ) holds the extension ( 32  or  72 ). 
     The above configuration allowing the two terminals ( 4  or  8 ) to be arranged on both sides of the inner shield ( 3  or  7 ) reduces noise propagation between the two terminals ( 4  or  8 ) in comparison to a connector where the inner shield ( 3  or  7 ) is not provided. The extension ( 32  or  72 ) of the connector is positioned by the shield holder (accommodation portion  28  or  68 ), thereby improving the accuracy of alignment between the extension ( 32  or  72 ) of the connector and the mating connector. 
     According to a second aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to the first aspect, the extension ( 32  or  72 ) protrudes in the first direction toward the mating connector side when the connector and the mating connector are transitioned from the disconnected state to the connected state. 
     The above configuration reduces a space occupied by the extension ( 32  or  72 ) when viewed from the first direction in comparison to a connector where the extension ( 32  or  72 ) protrudes in, e.g. the second direction. 
     According to a third aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to the second aspect, the housing ( 2  or  2 A, or  6  or  6 A) includes a wall portion ( 25 ,  26 , and  27 , or  65 ). The wall portion ( 25 ,  26 , and  27 , or  65 ) has a thickness in the third direction. The wall portion ( 25 ,  26 , and  27 , or  65 ) includes an accommodation portion ( 28  or  68 ) as the shield holder. The extension ( 32  or  72 ) is accommodated in the accommodation portion ( 28  or  68 ). 
     The above configuration secures an insulation distance of the extension ( 32  or  72 ) by the housing ( 2  or  2 A, or  6  or  6 A). 
     According to a fourth aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to any one of the first to third aspects, the extension ( 32  or  72 ) includes a contacting portion ( 332  or  720 ). The contacting portion ( 332  or  720 ) is configured to contact an inner shield of the mating connector. 
     The above configuration is adopted, and the extension ( 32  or  72 ) of the connector is positioned by the shield holder (accommodation portion  28  or  68 ), and thereby it is possible to improve the accuracy of the electrical connection between the inner shield ( 3  or  7 ) of the connector and the inner shield of the mating connector. 
     According to a fifth aspect, in the connector (socket S 1  or S 2 ) according to the fourth aspect, the extension (first extension  33 ) further includes an extension body ( 331 ). The extension body ( 331 ) protrudes from the base ( 31 ). The contacting portion ( 332 ) protrudes from the extension body ( 331 ). 
     The above configuration including the contacting portion ( 332 ) of the connector protruding from the extension body ( 331 ) prevents the extension (first extension  33 ) of the connector from contacting the inner shield of the mating connector at a position other than the contacting portion ( 332 ). 
     According to a sixth aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to the fourth or fifth aspect, the extension ( 32  or  72 ) has a plate shape. The contacting portion ( 332  or  720 ) is provided on the surface of the extension ( 32  or  72 ) along the longitudinal direction of the extension ( 32  or  72 ). 
     The above configuration secures the contact area between the contacting portion ( 332  or  720 ) of the connector and the inner shield of the mating connector. 
     According to a seventh aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to any one of the fourth to sixth aspects, each of the terminals ( 4  or  8 ) includes a contact portion ( 41  or  46 , or  81  or  84 ). The contact portion ( 41  or  46 , or  81  or  84 ) is configured to contact the mating terminal. The contacting portion ( 332  or  720 ) and the contact portion ( 41  or  46 , or  81  or  84 ) of at least one of the terminals ( 4  or  8 ) are arranged in the second direction. 
     The above configuration simplifies the structure of the connector. 
     According to an eighth aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to any one of the first to seventh aspects, the inner shield ( 3  or  7 ) includes plural extensions ( 32  or  72 ). 
     The above configuration further improve the accuracy of alignment between the extension ( 32  or  72 ) of the connector and the mating connector. 
     According to a ninth aspect, in the connector (socket S 1  or S 2 ) according to the eighth aspect, the plural extensions ( 32 ) include a first extension ( 33 ) and a second extension ( 34 ). The first extension ( 33 ) includes a contacting portion ( 332 ). The contacting portion ( 332 ) is configured to contact an inner shield of the mating connector. The second extension ( 34 ) is held by the shield holder (accommodation portion  28 ). 
     The above configuration increases the number of extensions ( 32 ) in comparison to a connector where the extensions ( 32 ) includes only the first extension ( 33 ). Thus, it is possible to further improve the accuracy of alignment between the extension ( 32 ) of the connector and the mating connector. 
     According to a tenth aspect, in the connector (socket S 1  or S 2 ) according to the ninth aspect, the accommodation space of the first extension ( 33 ) in the shield holder (accommodation portion  28 ) is larger than the first extension ( 33 ). 
     The above configuration increases a tolerable error in the alignment between the first extension ( 33 ) of the connector and the mating connector. 
     According to an eleventh aspect, according to any one of the first to tenth aspects, the connector (socket S 1  or S 2 , or header H 1  or H 2 ) further includes the outer shield ( 1  or  1 A, or  5  or  5 A). The outer shield ( 1  or  1 A, or  5  or  5 A) surrounds the terminals ( 4  or  8 ) and the inner shield ( 3  or  7 ). 
     The above configuration reduces noise propagation between the inside and the outside of the outer shield ( 1  or  1 A, or  5  or  5 A). 
     According to a twelfth aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to the eleventh aspect, the inner shield ( 3  or  7 ) includes two tip regions (r 1  or r 7 ). The outer shield ( 1  or  1 A, or  5  or  5 A) includes a first end (e 1  or e 5 ) and a second end (e 2  or e 6 ) opposite to the first end (e 1  or e 5 ). The first end (e 1  or e 5 ) is the end that is on the mating connector side when the connector and the mating connector are transitioned from the disconnected state to the connected state. The outer shield ( 1  or  1 A, or  5  or  5 A) faces at least one of the two tip regions (r 1  or r 7 ) in a region including the second end (e 2  or e 6 ) with the gap (g 1  or g 7 ). 
     The above configuration including at least a portion of the inner shield ( 3  or  7 ) provided on the second end (e 2  or e 6 ) side reduces noise propagation on the second end (e 2  or e 6 ) side. 
     According to a thirteenth aspect, in the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to the twelfth aspect, while a circuit board ( 150  or  550 ) is not provided, the outer shield ( 1  or  1 A, or  5  or  5 A) is electrically insulated from at least one of the two tip regions (r 1  or r 7 ) via the gap (g 1  or g 7 ). The circuit board ( 150  or  550 ) is configured to be electrically connected to the outer shield ( 1  or  1 A, or  5  or  5 A). 
     The above configuration improves a dimensional tolerance of each of the outer shield ( 1  or  1 A, or  5  or  5 A) and the inner shield ( 3  or  7 ) in comparison to a connector where the outer shield ( 1  or  1 A, or  5  or  5 A) contacts the two tip regions (r 1  or r 7 ). 
     The configuration other than the first aspect is not an essential configuration for the connector (socket S 1  or S 2 , or header H 1  or H 2 ) and may be appropriately omitted. 
     According to a fourteenth aspect, the connector device ( 100 ) includes the connector (socket S 1  or S 2 , or header H 1  or H 2 ) according to any one of the first to the thirteenth aspects, and the mating connector. 
     The above configuration including the two terminals ( 4  or  8 ) arranged on both sides of the inner shield ( 3  or  7 ) reduces noise propagation between the two terminals ( 4  or  8 ) in comparison to a connector where the inner shield ( 3  or  7 ) is not provided. Since the extension ( 32  or  72 ) of the connector is positioned by the shield holder (accommodation portion  28  or  68 ), the accuracy of alignment between the extension ( 32  or  72 ) of the connector and the mating connector is improved.