Patent Publication Number: US-11652325-B2

Title: Cable connector system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit to U.S. Patent Application No. 62/697,014, filed on Jul. 12, 2018; U.S. Patent Application No. 62/728,278, filed on Sep. 7, 2018; U.S. Patent Application No. 62/704,025, filed on Oct. 9, 2018; U.S. Patent Application No. 62/704,052, filed on Jan. 28, 2019; U.S. Patent Application No. 62/813,102, filed on Mar. 3, 2019; and U.S. Patent Application No. 62/840,731, filed Apr. 30, 2019, all of which are incorporated by reference in their entirety for all purposes as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to connector systems. More specifically, the present invention relates to connector systems that facilitate data throughput through a 1 rack unit (RU) panel, where 1 RU is equal to 1.75 inches or 44.45 mm by 19 inches or 482.6 mm, of at least 15 TB/sec. 
     2. Description of the Related Art 
     Up to seventy-two SFP+ ports can fit within a 1 RU faceplate area of about 352.75 mm by 41 mm (or 144.6 cm 2 ). Corresponding throughput is 720 Gb/sec. Up to seventy-two zSFP+ ports can fit within the 1 RU faceplate area. Corresponding throughput is 1.8 Tb/sec. Up to thirty-six QSFP28 ports can fit within the 1 RU faceplate area. Corresponding throughput is 3.6 Tb/sec. Up to thirty-six QSFP56 ports can fit within the 1 RU faceplate area. Corresponding throughput is 7.2 Tb/sec. Up to seventy-two microQSFP ports can fit within the 1 RU faceplate area. Corresponding throughput is 14.4 Tb/sec. Up to seventy-two SFP-DD ports can fit within the 1 RU faceplate area. Corresponding throughput is 7.2 Tb/sec. Up to thirty-six QSFP-DD ports can fit within the 1 RU faceplate area. Corresponding throughput is 14.4 Tb/sec. 
     SUMMARY OF THE INVENTION 
     The embodiments of the present invention facilitate throughput of at least 15 Tb/sec, at least 20 Tb/sec, at least 25 Tb/sec, at least 30 Tb/sec, at least 35 Tb/sec, at least 37.5 Tb/sec, at least 40 Tb/sec, at least 45 Tb/sec, and at least 50 Tb/sec through various 1 RU faceplate areas. Throughput of 37.5 Tb/sec or 50 Tb/sec is more than double the 14.4 Tb/sec throughput of the prior art. 
     Various independent embodiments of the present invention can include cable connectors that can connect orthogonally to a mating connector, such as a board connector; board connectors with compression spring ground blades that connect electrically with connector shields of a respective cable connector; connector systems that can each include a board connector and a mating cable connector positioned on both sides of a die package; and first electrical panel connectors that can carry up to or at least thirty-two differential signal pairs but still operate with 0 dB to −0.5 dB of insertion loss through frequencies up to and including 28 GHz, 56G NRZ, and 112G PAM4; operate with return loss under −15 dB through frequencies up to and including 30 GHz, 56G NRZ, and 112G PAM4; or operate with frequency domain near end crosstalk of under −50 dB through frequencies up to and including 30 GHz, 56G NRZ, and 112G PAM 4. 
     Embodiments of the present invention provide cable connector systems that allow cable connectors to be connected to a board connector in a stacked or nested configuration, while reducing the footprint and stack height required by the board connector. For example, embodiments of the present invention can be used in groups of connectors positioned on one or both opposed surfaces of a die package substrate. Embodiments of the present invention can be used to collectively transmit at least 37.5 terabytes of data per second with frequency domain crosstalk of −40 dB or better on a standard 70-mm-by-70-mm die package. On larger die packages, such as 120-mm-by-120 mm die package, a 145-mm-by-145-mm die package, a 150-mm-by-150-mm die package, or other sized die packages larger than 70-mm-by-70-mm, data throughput can be at least 50 Tb/sec. Embodiments of the present invention can have a height, measured from a mounting surface of the PCB to a top surface of any one of the board connectors described herein of about 1.5 mm to about 6 mm. 
     According to an embodiment of the present invention, a cable includes a first cable conductor that defines a first mating end, a second cable conductor that defines a second mating end, and an insert that carries the first cable conductor and the second cable conductor. The first mating end defines a first contact surface, the second mating end defines a second contact surface, the first contact surface is configured to electrically connect to a first electrical contact, and the second contact surface is configured to electrically connect to a second electrical contact. The first contact surface and the second contact surface can face in opposite directions. 
     The first cable conductor and the cable second conductor can define a differential signal pair. The cable connector can further include a dielectric layer that at least partially surrounds the first cable conductor and the second cable conductor. The cable connector can further include a cable shield that at least partially surrounds the dielectric layer. 
     A first centerline can divide a cross-section of the first mating end of the first cable conductor into a first semicircle and a second semicircle, and the first semicircle can be devoid of plastic and defines the first contact surface. A second centerline can divide a cross-section of the second mating end of the second cable conductor into a third semicircle and a fourth semicircle, and the fourth semicircle can be devoid of plastic and defines the second contact surface. 
     A first centerline line can divide a cross-section of the first mating end of the first cable conductor into a first semicircle and a second semicircle; a second centerline can divide a cross-section of the second mating end of the second cable conductor into a third semicircle and a fourth semicircle; and the first semicircle can be devoid of plastic, the fourth semicircle can be devoid of plastic, and the second and third semicircles can be positioned between the first semicircle and the fourth semicircle. 
     A centerline line can divide a cross-section of the first mating end of the first cable conductor into a first semicircle and a second semicircle and a cross-section of the second mating end of the second cable conductor into a third semicircle and a fourth semicircle; and the first semicircle can be devoid of plastic, the third semicircle can be devoid of plastic, the first contact surface can face away from the second semicircle, and the second contact surface can face away from the third semicircle. 
     The first mating end can be devoid of a cable shield. The second mating end can be devoid of a cable shield. The first contact surface can be only a single contact surface. The second contact surface can be only a single contact surface. 
     The cable connector can further include a connector shield carried by the insert. The connector shield can define a groove, and the groove can be configured to receive a cable shield. The connector shield can define a slot, and the slot can be configured to receive a ground blade of a mating connector. 
     The insert can define a tooth. The insert can define a first hole and a second hole adjacent to the base. The tooth can define a base and a cross member positioned perpendicular to the base. The base can define a first base recess adjacent to the first hole, and the first hole and the first base recess can receive the first mating end of the first cable conductor. The base can define a second base recess adjacent to the second hole, and the second hole and the second base recess can receive the second mating end of the second cable conductor. 
     The first conductor and the second conductor can be part of a shielded, coextruded twin axial cable that can have a gauge of 34 AWG to 36 AWG. The first conductor and the second conductor can be part of a shielded, co-extruded twin axial cable that can have a gauge of 28 AWG to 30 AWG. 
     The cable connector can be arranged to be nested within a mating connector when mated with the mating connector. 
     According to an embodiment of the present invention, a cable connector includes a cable; an insert including an insert body that defines holes and a tooth adjacent to the holes, wherein the tooth extends away from the insert body; and a connector shield connected to the insert. A first mating end of a first cable conductor and a second mating end of a second cable conductor extend through respective holes such that the first and second mating ends of the respective first and second cable conductors are supported by the tooth. 
     The cable can include a cable shield; the connector shield can include grooves; and the cable shield can be connected to a corresponding one of the grooves. 
     According to an embodiment of the present invention, a board connector includes a board connector housing, a ground plane carried by the board connector housing, and electrical contacts carried by the board connector housing, wherein the electrical contacts electrically contact only one semicircular side of a respective mating cable conductor. 
     The ground plane can include at least one ground plane arm that extends into a hole in the board connector housing. The ground plane can include at least one slot. The ground plane can include at least one hole. 
     The board connector can further include a ground blade that electrically connects with the ground plane. The ground blade can include a tail, a leg, and a spring; and the tail can extend through the board connector housing, and the spring can be configured to electrically connect to a cable shield of a mating cable connector. 
     The ground plane can include ground arms that extend beneath heads of the electrical contacts. The ground plane and the board connector housing can each define a right angle shape. The electrical contacts can be configured to be surface mounted to a substrate. 
     According to an embodiment of the present invention, a board connector includes a board connector housing including a second connector mating interface that receives a second cable connector and a first connector mating interface that receives a first cable connector that is stacked on top of second cable connector; ground blades that extend into both the first and second connector mating interfaces; and between two of the ground blades that are adjacent to each other, a first pair of electrical contacts that directly contact a respective one of a first cable conductor and a second cable conductor of the first cable connector; and a second pair of electrical contacts that directly contact a respective one of a first cable conductor and a second cable conductor of the second cable connector. 
     The board connector can further include a first ground plane positioned in the second connector mating interface and a second ground plane positioned in the first connector mating interface. 
     According to an embodiment of the present invention, a cable connector system includes a board connector, a first cable connector including a first insert connected to first cables, and a second cable connector including a second insert connected to second cables. The first and the second cable connectors are connected to the board connector with the first cable connector stacked on top of the second cable connector. 
     When the board connector is connected to a substrate, a portion of each of the first cables adjacent to the first insert can extend parallel or substantially parallel to a major surface of the substrate, and a portion of each of the second cables adjacent to the second insert can extend parallel or substantially parallel to the major surface of the substrate. 
     The first insert can include holes in which corresponding first and second cable conductors of the first cables are located and teeth that support corresponding first and second mating ends of the first and second cable conductors of the first cables, and the second insert can includes holes in which corresponding first and second cable conductors of the second cables are located and teeth that support corresponding first and second mating ends of the first and second cable conductors of the second cables. 
     The board connector can include electrical contacts that are directly connected to corresponding first and second mating ends of first and second cable conductors of the first and second cables. The electrical contacts can be directly connected to only one side of the corresponding first and second mating ends along a length of the first and second cable conductors of the first and the second cables. 
     The board connector can include ground blades that extend between and along the first and second cables so that a corresponding ground blade is on each side of each of the first and second cables. The board connector can includes a first ground plane that extends under the first cable connector and a second ground plane that extends under the second cable connector. 
     According to an embodiment of the present invention, a die package includes a substrate that defines a first package surface and a second package surface opposed to the first package surface; a die positioned on the first package surface; first electrical connectors positioned on the first package surface; and second electrical connectors positioned on the second package surface. The first and second electrical connectors each carry differential signal pairs and each is in electrical communication with the die. 
     The die package can further include a pad field on the second package surface. 
     The first electrical connectors can be connector systems each comprising a board connector and a cable connector; the cable connector can include a first conductor that defines a first mating end, a second conductor that defines a second mating end, and an insert that carries the first conductor and the second conductor; and the first mating end can define a first contact surface, the second mating end can define a second contact surface, the first contact surface can be configured to electrically connect to a first electrical contact, and the second contact surface can be configured to electrically connect to a second electrical contact. 
     The first and second electrical connectors can each be a board connector that each receive at least one respective cable connector, where the at least one respective cable connector can be attached to one end of cables, and a first electrical panel connector can be attached to opposite ends of the cables. The first and second electrical connectors can include a total of at least 513 differential signal pairs, a total of at least 600 differential signal pairs, at least 700 differential signal pairs, at least 800 differential signal pairs, at least 900 differential signal pairs, at least 1000 differential signal pairs, or at least 1024 differential signal pairs. 
     According to an embodiment of the present invention, a cable assembly includes at least thirty-two twin axial cables, each of the at least thirty-two twin axial cables includes a first conductor and a second conductor, defines a first end and a second end opposed to the first end, and has a gauge of 34-36 AWG; at least four rows of electrical contact pairs connected to respective first ends of the at least thirty-two twin axial cables, each of the at least four rows of electrical contact pairs includes at least eight differential signal pairs; and a first electrical panel connector connected to respective second ends of the at least thirty-two twin axial cables, the first electrical panel connector includes thirty-two differential signal pairs. The cable assembly is sized and shaped such that the cable assembly will fit within a 1.75 inch height of a 1 RU panel when vertically stacked with another cable assembly. 
     The cable assembly can be devoid of a printed circuit board. The first electrical panel connector does not have to receive a printed circuit board. 
     A cable assembly system according to embodiments of the present invention includes thirty-two cable assemblies that can fit within 212 cm 2 , 206 cm 2 , 200 cm 2 , and 194 cm 2 . Thirty-two cable assemblies can carry at least 1024 cables. 
     According to an embodiment of the present invention, a method includes passing at least 15 terabytes/sec through an approximate 143 cm 2  area of a 1 RU panel using copper cables. 
     According to an embodiment of the present invention, a method includes passing at least 16 to 37.5 terabytes/sec through an approximate 168 cm 2  area of a 1 RU panel using copper cables. 
     According to an embodiment of the present invention, a method includes passing at least 38 terabytes/sec through an approximate 192 cm 2  area of a 1 RU panel using copper cables. 
     According to an embodiment of the present invention, a method includes passing at least 50 terabytes/sec through an approximate 192 cm 2  area of a 1 RU panel using copper cables. 
     The above and other features, elements, characteristics, steps, and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1  and  2    show a connector system including a board connector and two cable connectors according to a first embodiment. 
         FIGS.  3  and  4    show the board connector of  FIG.  1   . 
         FIG.  5    shows the board connector housing of the board connector of  FIG.  3   . 
         FIGS.  6  and  7    show partially assembled board connectors of  FIG.  3   . 
         FIG.  8    is a close-up view of the connector system of  FIG.  1   . 
         FIG.  9    shows a ground blade that can be used with the board connector housing of  FIG.  5   . 
         FIG.  10    shows a ground plane that can be used with the board connector housing of  FIG.  5   . 
         FIGS.  11  and  12    show contacts that can be used with the board connector housing of  FIG.  5   . 
         FIGS.  13  and  14    show an end of the cable connector with the insert. 
         FIGS.  15  and  16    show a partially assembled cable connector of  FIG.  13   . 
         FIGS.  17  and  18    show an insert that can be used with the cable connector of  FIG.  13   . 
         FIG.  19    shows a connector shield that can be used with the cable connector of  FIG.  13   . 
         FIG.  20    shows a cable that can be used with the cable connector of  FIG.  13   . 
         FIG.  21    shows a close-up view of a tooth and contacts of the cable connector system shown in  FIG.  1   . 
         FIG.  22    shows a cross-section of the cable shown in  FIG.  20    with a cable shield and jacket removed for clarity. 
         FIG.  23    is a perspective, side view of a connector system according to a second embodiment. 
         FIG.  24    is a side view of the connector system shown in  FIG.  23   . 
         FIG.  25    shows the cable connector shown in  FIGS.  23  and  24   . 
         FIG.  26    shows the insert used in the cable connector shown in  FIGS.  23 - 25   . 
         FIG.  27    shows the wafer shown in  FIG.  23   . 
         FIG.  28    is a cross-section of the cable shown in  FIG.  20    and  FIG.  25    with a cable shield and jacket removed for clarity. 
         FIG.  29    is a top view of a die package. 
         FIG.  30    is a bottom perspective view of the die package shown in  FIG.  29   . 
         FIG.  31    is a perspective side view of a die package and connector systems according to a third embodiment. 
         FIG.  32    is a perspective side view of a first electrical panel connector. 
         FIG.  33    is a front view of a 1 RU panel. 
         FIG.  34    is a perspective side view of a second electrical panel connector. 
     
    
    
     DETAILED DESCRIPTION 
     Connector systems described herein can include a first connector and a mating second connector. Board connectors can be a first connector; and first, second, and third cable connectors can be mating second connectors. Alternatively, board connectors can be a second mating connector; and first, second, and third cable connectors can be respective first connectors. First, second, and third cable connectors can include a cable that includes a first cable conductor and a second cable conductor. Cable assemblies can include a cable with a first, second, or third cable connector attached to one end of the cable, and a first electrical panel connector attached to an opposed end of the cable. 
       FIG.  1    shows a connector system  100  that includes a board connector  110 , a first cable connector  120 , a second cable connector  130 , and a plurality of cables  140 . The board connector  110  is attached to a suitable substrate (not shown), including, for example, a printed circuit board. The board connector  110  can define a stair step shape, with a first connector mating interface  150  offset from and elevated from a second connector mating interface  160 . First board connector  110  can also be a right angle connector. 
     The second cable connector  130  is connected to the board connector  110  first, and then the first cable connector  120  is connected to the board connector  110 . The first and second cable connectors  120 ,  130  are connected to the board connector  110  by inserting the first and second cable connectors  120 ,  130  from an insertion/unmate direction that is orthogonal or substantially orthogonal, within manufacturing tolerances, to a major surface of the substrate on which the board connector  110  is mounted. Alternatively, the second cable connector  130  can also be rotated into position in the second connector mating interface  160 , and the first cable connector  120  can be rotated into position in the first connector mating interface  150 . The first cable connector  130  can at least partially overlap the second cable connector  130  when the first and second cable connectors  120 ,  130  are both electrically connected to the board connector  110 . Each of the first and second cable connectors  120 ,  130  can have respective electrical cables  140  attached thereto. Cable  140  can be twin axial cables, coaxial cables, extruded twin axial cables, shielded cables, or any other suitable cables. In differential signal applications, cable  140  could be twin axial cable or individual coaxial cables. Cable  140  can be 26-36 AWG differential signal cables, such as 32, 33, 34, 35 or 36 AWG. Individual coaxial cables can each have smaller cross-sectional diameters/larger AWGs. 
     Any cable  140  described herein can include an electrical insulator  142  that at least partially surrounds a first conductor or a first cable conductor  190 , an electrically conductive cable shield  144  that at least partially surrounds the electrical insulator  142 , and an outer electrically non-conductive jacket  146  that at least partially surrounds the electrically conductive cable shield  144 . 
     With the stacked arrangement of first and second cable connectors  120 ,  130 , it is possible to achieve a mated stack height of the cable connector system, determined by the height H of a board connector housing of the board connector  110 , which can be about 1.5 mm in length for a one row board connector and about 3 mm in length for a two row board connector. Cable  140  portions adjacent to the first and second cable connectors  120 ,  130  can each extend parallel or substantially parallel within manufacturing tolerances to the substrate to which the board connector  110  is mounted. Although  FIG.  1    shows first and second cable connectors  120 ,  130  connected to the board connector  110 , it is possible that more than two cable connectors can be connected to the board connector, which would increase both the footprint and stack height of the board connector. For example, as shown in  FIG.  1   , height H of a board connector housing of the board connector  110  can be about 4.5 mm for a three row board connector and about 6 mm for a four row board connector. 
       FIG.  2    is a bottom view of the connector system  100  shown in  FIG.  1   . Second cable connector  130 , cables  140 , a board connector mounting interface  170  are shown. Mount ends of ground blade  320 , ground plane  330 , and mount ends of electrical contact  340  are shown. 
       FIG.  3    is a top perspective view of the board connector  110 . The board connector  110  can include a board connector housing  310 , ground blades  320 , ground planes  330 , and electrical contacts  340 . The board connector housing  310  can be made of any suitable dielectric material. The ground blades  320 , ground planes  330 , and electrical contacts  340  can be made from any suitable electrically conductive material. The ground blades  320 , ground planes  330 , and electrical contacts  340  can be made by stamping or any other suitable method. 
     The board connector  110  can include four or more ground blades  320 . As shown in  FIG.  1   , two ground blades can flank or be positioned on opposed sides of cable  140 . As shown in  FIG.  3   , board connector  110  can include two ground planes  330 , with one ground plane  330  for each respective first and second cable connector  120 ,  130 . Board connector  110  can include two electrical contacts  340  for each cable connected to the board connector  110 . The board connector  110  can include any number of ground blades  320 , any number ground planes  330 , and any number of electrical contacts  340 , depending on the number of cables  140  per first and second cable connectors  120 ,  130 , and depending on the number of first and second cable connectors  120 ,  130 . If there are M cables  140  per first or second cable connector  120 ,  130 , then the board connector  110  can include M+1 ground blades  320  to ensure that each cable  140  is surrounded or flanked by two ground blades  320  oriented parallel to the cables  140 . 
     The ground blades  320  can be used with both of the first and second cable connectors  120 ,  130 , but it is possible to use two separate ground blades  320  for the first and second cable connectors so that the board connector  110  includes 2*(M+1) ground blades  320 . If there are N first and second cable connectors  120 ,  130 , then the board connector  110  can include N ground planes  330 . If there are P total cables  140  in both the first and second cable connectors  120 ,  130 , then the board connector  110  can include 2*P electrical contacts  340 , assuming each cable  140  is a twin axial cable with two center conductors. If the cables  140  are coaxial cables with a single center conductor, then the board connector  110  can include P electrical contacts  340 . 
       FIG.  4    is a bottom perspective view of board connector  110 . Board connector housing  310  defines openings  350  and the ground blades  320 , ground planes  330 , and electrical contacts protrude into or through the openings  350 . 
       FIG.  5    shows the board connector housing  310  of the board connector  110 , with electrically conductive parts removed for clarity. 
     As discussed above, the board connector housing  310  can define openings  350  that receive the ground blades, the ground planes, and the electrical contacts. The board connector housing  310  can further define protrusions  360  that engage with corresponding holes defined by the ground plane. The height H1 of the protrusions  360  in the board connector housing  310  can also be chosen such that the protrusion  360  engages with a respective one of the first cable connector  120  and second cable connector  130  when the first and second cable connectors  120 ,  130  are connected to the board connector  110 . 
     The board connector housing  310  can define an open end  314  and a floor  316 . First and second cable connectors  120 ,  130  (shown in  FIG.  1   ) can be inserted into the board connector housing  310  in a direction orthogonal to both the open end  314  and the floor  316  or can be rotated in a direction toward the floor. The open end  314  and the floor  316  can both extend parallel to a mounting substrate, and perpendicular or substantially perpendicular to the height H1 of the protrusions  360 . The second connector mating interface  160  can be offset from the first connector mating interface  150  and can be elevated farther from the floor  316  than the first connector mating interface  150 . The open end  314  permits the second cable connector  130  (as shown in  FIG.  8   ) or the electrical contacts  340  to remain exposed after the first cable connector  120  (as shown in  FIG.  8   ) is mated to the board connector housing  310 . Stated another way, the electrical contacts  340  are bounded by only four walls, such as floor  316 , first and second parallel sidewalls  318   a ,  318   b  that each extend perpendicular to the floor  316 , and rear wall  319  that extends perpendicular to the floor  316  and perpendicularly intersects each of the first and second parallel sidewalls  318   a ,  318   b . Each of the first and second parallel sidewalls  318   a ,  318   b  can define a stepped or L-shape. 
       FIG.  6    shows a partially assembled board connector  110 , populated with only two ground blades  320  and only four pairs of electrical contacts  340 . As shown, the ground blades  320  act as interstitial shields between immediately adjacent pairs of electrical contacts  340  in a respective one of the first connector mating interface  150  and the second connector mating interface  160 . The ground blades  320  and ground planes  330 , such as first and second ground planes  330   a ,  330   b , can be arranged to surround the electrical contacts  340  and the first and second cable conductors  390 ,  392  (shown in  FIG.  8   ) on three sides, partially extending the arrangement from the cable  380  (shown in  FIG.  8   ) in which the first and second cable conductors  390 ,  392  (shown  FIG.  8   ) are completely surrounded by the cable shield  382  (shown in  FIG.  7   ) in the cable  380  (shown in  FIG.  7   ). The ground blades  320 , ground planes  330 , connector shields  375 , and cable shields  383  can all be electrically connected together and can all be connected to ground or reference. The interaction of the ground blades  320  and the connector shields  375  also provides retention of the first and second cable conductors on the board connector  110  without an additional active or passive latch. 
       FIG.  7    shows a partially assembled connector system  100  with only the second cable connector  130  connected to the board connector housing  310  of the board connector  110 . Ground blades  320  are electrically connected to cable shield  382  of the cable  380 . Ground plane  330  is positioned underneath differential signal pairs or other pairs of electrical contacts  340  in the first connector mating interface  150 . Connector shield  375  is carried by the second cable connector  130 . The second cable connector  130  may further include an insert  370  that may define a tooth  372 . 
       FIG.  8    shows first and second cable connectors  120 ,  130  connected to the board connector  110 . The board connector  110  can carry electrical contacts  340 , such as differential signal pairs; ground blades  320 ; and a ground plane  330  (not shown in  FIG.  8   ). The first cable connector  120  can be flush with a first surface  315  of the board connector housing  310  of the board connector  110 , be recessed into the first surface  315 , or extend beyond the first surface  315 . Ground blades  320 , carried by the board connector housing  310 , are positioned in spaces  322  defined by immediately adjacent protruding walls  332  of respective connector shields  375  of the first and second cable connectors. Cables  380  are positioned in grooves  334  defined by immediately adjacent protruding walls  332  of the respective connector shields  375 , such that cable shield  382  is in electrical contact with grooves  334  of the respective connector shields  375 . The pattern of protruding wall  332 , ground blade  320 , protruding wall  332 , cable  380 , protruding wall  332 , and ground blade  320  can be repeating. 
     Insert  370  of a respective first or second cable connector  120 ,  130  can be made from an electrically non-conductive material and can define a tooth or one or more teeth  372 . Insert  370  can carry the connector shield  375 , cables  380 , respective cable shields  382 , respective first and second cable conductors  390 ,  392  of the respective cables  380 , and electrically non-conductive material positioned between the respective first and second cable conductors  390 ,  392  and the respective cable shields  382 . First and second cable conductors  390 ,  392  are stripped bare and may both extend through the insert  370  and through a respective tooth  372  so that one tooth carries both the first and second cable conductors  390 ,  393 . The first cable conductor  390  electrically connects with a respective electrical contact  340 , but only one side of the first cable conductor  390 . The second cable conductor  392  electrically connects with a respective electrical contact  340 , but only one side of the second cable conductor  392 . When a first or second cable connector  120 ,  130  is connected to the board connector  110 , the first and second cable conductors  390 ,  392  are already exposed, and the electrical contacts  340  do not cut the jacket, cable shield  382 , or dielectric layer of a respective cable  380 . The electrical contacts  340  can electrically connect to respective first and second cable conductors  390 ,  392  by a spring force exerted on a respective first or second cable conductor  390 ,  392 . First and second cable connectors  120 ,  130  can be identical or substantially identical in construction. Tooth or teeth  372  can have a larger cross-sectional area than the first cable conductor  390  or the second cable conductor  392 . 
       FIG.  9    shows a ground blade  900  that can be inserted into the holes in the board connector housing  310 ,  FIG.  3   . The ground blade  900  can include tails  910  that can be soldered to a substrate using surface-mount technology (SMT). Instead of including SMT tails to mount the ground blade  900  to the substrate, the ground blade  900  can include press-fit tails, through-hole tails, or any other suitable structure to mount the ground blade  900  to the substrate. The ground blade  900  also includes legs  920  that may be inserted into holes  1010  (shown in  FIG.  10   ) in the ground planes  1000  (shown in  FIG.  10   ). The ground blades  900  can also include two springs, such as first spring  930   a  and second spring  930   b . Each of the first and second springs  930   a ,  930   b  can be inserted into spaces  322  (shown in  FIG.  8   ) in the connector shield  375  of the first or second cable connector  120 ,  130  (shown in  FIG.  1   ) to help secure the first and second cable connectors  120 ,  230  to the board connector  110  (shown in  FIG.  1   ). 
     Referring again to  FIG.  9   , the number of springs can depend on the number of cable connectors. For example, as seen in  FIG.  8   , each ground plane  330  can include two springs, with one spring engaging the second cable connector  130  and with the other spring engaging the first cable connector  120 , but it is possible to use a different number of springs. As shown in  FIG.  9   , the first spring  930   a  can include bosses  940  on opposite sides of the first spring  930   a . The bosses  940  help keep the second cable connector  130  mated with the board connector  110 . 
       FIG.  10    shows a ground plane  1000  similar to the ground plane  330  (shown in  FIG.  6   ) that can be used within the first connector mating interface  150  (shown in  FIG.  1   ), the second mating interface  160  (shown in  FIG.  1   ), or both. The ground plane  1000  can include holes  1010  that engage with the protrusions  360  (shown in  FIG.  5   ) in the board connector housing  310  (shown in  FIG.  5   ). The ground plane  1000  can include ground plane arms  1020 . Respective ground plane arms  1020  can extend into openings  350  (shown in  FIG.  4   ) in the board connector housing  310  (shown in  FIG.  3   ) and can engage with a connector shield  375  (shown in  FIG.  7   ) of corresponding first or second cable connectors  120 ,  130  (shown in  FIG.  1   ). Slots  1030  can receive corresponding legs  920  (shown in  FIG.  9   ) of the ground blades  900  (shown in  FIG.  9   ). 
       FIG.  11    shows a contact pair of electrical contacts  1100  that can be used in the second connector mating interface  160  (shown in  FIG.  1   ) of the board connector  110  (shown in  FIG.  1   ). Instead of contact pairs, a single electrical contact  1100  can be used if the cables  380  (shown in  FIG.  8   ) include a single first cable conductor  390  (shown in  FIG.  8   ). Each electrical contact  340  can be cantilevered, including a head  1110  and tail  1120  that are connected at 90° or approximately 90° within manufacturing tolerances. Respective opposing surfaces  1112  of the heads  1110  of the contact pair of electrical contacts  1100  can contact or electrically contact only a single exterior portion of the first and second cable conductors  390 ,  392  (shown in  FIG.  8   ) of the cable  380  (shown in  FIG.  8   ). The heads  1110  can include a lead-in  1130  and a bend  1140  to assist with mating with a corresponding first or second cable conductor  390 ,  392  (shown in  FIG.  8   ) of the cable  380  (shown in  FIG.  8   ). The lead-ins  1130  can assist in guiding a tooth or the teeth  372  (shown in  FIG.  8   ) of a respective first and second cable connector  120 ,  130  (shown in  FIG.  8   ) when the first and second cable connectors  120 ,  130  (shown in  FIG.  8   ) are mated with the board connector  110  (shown in  FIG.  8   ). The bend  1140  can be shaped to accommodate the end of a corresponding tooth  372  (shown in  FIG.  8   ). The tail  1120  can be surface mounted to a substrate. Alternatively, the tail  1120  can include a press-fit tail, a through-hole tail, or any other suitable structure to attach the electrical contacts  1100  to the substrate. The electrical contacts  1100  that can be used with the second connector mating interface  160  (shown in  FIG.  1   ) of the board connector  110  (shown in  FIG.  1   ) can each include a retention wedge  1150  to help secure the respective electrical contact  1100  in the board connector housing  310  (shown in  FIG.  7   ) of board connector  110  (shown in  FIG.  7   ). 
       FIG.  12    shows a contact pair of electrical contacts  1200  that can be used in the first connector mating interface  150  (shown in  FIG.  1   ) of the board connector  110  (shown in  FIG.  1   ). Instead of contact pairs, a single electrical contact  1200  can be used if the cables  380  (shown in  FIG.  8   ) include a single first or second cable conductor  390  (shown in  FIG.  8   ). Each electrical contact  1200  can be cantilevered, including a head  1210  and tail  1220  that are connected at 90° or approximately 90° within manufacturing tolerances. Respective opposing contact surfaces  1212  of the heads  1210  of the contact pair of electrical contacts  1200  can contact or electrically contact only a single exterior portion of a corresponding first and second cable conductor  390 ,  392  (shown in  FIG.  8   ), such as a first contact surface  1397  (shown in  FIG.  22   ) and a second contact surface  1398  (shown in  FIG.  22   ). The heads  1210  can include a lead-in  1230  and a bend  1240  to assist with mating with the first and second cable conductors  390 ,  392  (shown in  FIG.  8   ) of the cable  380  (shown in  FIG.  8   ). The lead-ins  1230  can assist in guiding a tooth or the teeth  372  (shown in  FIG.  8   ) of a respective first and second cable connector  120 ,  130  (shown in  FIG.  8   ) when the first and second cable connectors  120 ,  130  (shown in  FIG.  8   ) are mated with the board connector  110  (shown in  FIG.  8   ). The bend  1240  can be shaped to accommodate the end of a corresponding tooth  372  (shown in  FIG.  8   ). The tail  1220  can be surface mounted to a substrate. Alternatively, the tail  1220  can include a press-fit tail, a through-hole tail, or any other suitable structure to attach the electrical contacts  1200  to the substrate. The electrical contacts  1200  that can be used with the first connector mating interface  150  (shown in  FIG.  1   ) of the board connector  110  (shown in  FIG.  1   ) can each include a retention wedge similar to retention wedge  1150  (shown in  FIG.  11   ) to help secure the respective electrical contact  1200  in the board connector housing  310  (shown in  FIG.  7   ) of board connector  110  (shown in  FIG.  7   ). 
       FIGS.  13 - 15    show a first or second cable connector  1300  that can be used with the board connector  110  of  FIG.  3   . The same type of first or second cable connector  1300  shown in  FIGS.  13 - 15    can be used for either or both of the first and second cable connectors  120 ,  130  (shown in  FIG.  1   ). The first or second cable connector  1300  can include at least one cable  1340 , an insert  1310 , and a connector shield  1320 . Although  FIGS.  13  and  14    show three cables  1340 , any number of cables can be used. 
     The cable or cables  1340  can be similar to the cables  2040  shown in  FIG.  20   , but it is possible to use other suitable cables, including, for example, a coaxial cable with a single center conductor. The cable  2040  in  FIG.  20    can be a twin axial, co-extruded, shielded differential signal pair cable that can include first and second cable conductors  2047 ,  2048  surround by a dielectric layer  2049 , a cable shield  2045  surrounding the dielectric layer  2049 , and a jacket  2043  surrounding the cable shield  2045 . The respective first and second cable conductors  2047 ,  2048  and the cable shield  2045  of each cable  2040  can be exposed before being connected to the first or second cable connector  1300 . Although not shown, the cable  2040  can include a drain wire in place of or in combination with the cable shield  2045 . 
     The insert  1310  can be made from an electrically insulative material and can define at least one tooth or a plurality of teeth  1330 . Each tooth  1330  can define a T-shape, with a cross-member  1372  and a base  1374 . The cross-member  1372  can extend perpendicular or substantially perpendicular to the base  1374 , can extend perpendicular or substantially perpendicular to the first and second cable conductors  1347   a ,  1347   b , and lie substantially in a common plane with the base  1374 . The base  1374  can be oriented perpendicular or substantially perpendicular to the cross-member  1372 . The base  1374  can also be oriented parallel or substantially parallel to the first and second cable conductors  1347   a ,  1347   b.    
     The insert  1310  can define at least one or a plurality of holes  1370  that each receive a respective one of the first and second cable conductors  1347   a ,  1347   b . A hole  1370  can transition into a base recess  1376 , such as a semi-circular recess in cross section, such that the hole  1370  and the base recess  1376  can receive a respective first or second cable conductor  1347   a ,  1347   b . In turn, the base recess  1376  can transition into a cross-member recess  1378  that can also receive a respective one of a first or second cable conductor  1347   a ,  1347   b.    
     The connector shield  1320  can define at least one or a plurality of grooves that can each receive a respective cable shield  1382  of a respective cable  1340 . The cable shields  1382  can be electrically connected by the connector shield  1320 . The connector shield  1320  can also define at least one or a plurality of slots  1360 . Each slot  1360  can receive a respective ground blade  320  (shown in  FIG.  1   ) of a board connector  110  (shown in  FIG.  1   ), such that the connector shield  1320  can be electrically connected to a ground blade  320  (shown in  FIG.  1   ). 
       FIG.  15    shows a first cable conductor  1347   a  and a second cable conductor  1347   b . The first cable conductor  1347   a  can include a first mating end  1390 , and the second cable conductor  1347   b  can include a second mating end  1392 . The insert  1310  can carry the first mating end  1390  of the first cable conductor  1347   a  and the second mating end  1392  of the second cable conductor  1347   b . A first centerline CL1 can divide the first mating end  1390  into a first semicircle and a second semicircle. A second centerline CL2 can divide the second mating end  1392  into a third semicircle  1395  and a fourth semicircle  1396 . The first mating end  1390  and the second mating end  1392  can be a respective exposed first or second cable conductor  1347   a ,  1347   b . The first semicircle  1393  of the first mating end  1390  can define a respective first contact surface  1397 , and the fourth semicircle  1396  of the second mating end  1392  can define a respective second contact surface  1398 . First and second contact surfaces  1397 ,  1398  can oppose each other. The first and fourth semicircles  1393 ,  1396  can each define flat surfaces, and are not strictly limited to arced or curved cross-sectional shapes. 
       FIG.  16    shows an insert  1310  with teeth  1330 . Countersunk recesses  1312  can each receive a respective cable  1340 . A first or second cable conductor  1347   a ,  1347   b  can be inserted into a respective hole  1370  and extend into a respective tooth  1330 . Cable shield  1382  can sit in a groove  1350  of connector shield  1320 . 
     The insert  1710  is shown as separate from the connector shield in  FIGS.  17  and  18   . The insert  1710  can be made by insert molding an insert body  1715  around arms  1970  (shown in  FIG.  19   ) of the connector shield  1900  (shown in  FIG.  19   ) so that insert  1710  is integrally formed with the connector shield  1900  (shown in  FIG.  19   ). The insert body  1715  can define through holes  1770  and with teeth  1730  aligned with the through holes  1770 . As shown in  FIGS.  17  and  18   , the insert  1710  can include a counter-sunk hole  1775  into which the first and second cable conductors  1347   a ,  1347   b  (shown in  FIG.  15   ), dielectric layer, and cable shield  1382  (shown in  FIG.  15   ) can be inserted, and two additional counter-sunk holes  1780  (shown in  FIG.  18   ) that receive only the first and second cable conductors  1347   a ,  1347   b  can be located in the counter-sunk hole  1775 . 
     Once inserted into the through holes  1770  of the insert  1710 , the first and second cable conductors  1347   a ,  1347   b  (shown in  FIG.  15   ) can be secured to the end of the teeth  1730  by any suitable method. For example, the first and second cable conductors  1347   a ,  1347   b  (shown in  FIG.  15   ) can be held in place by securing the dielectric layer to the insert  1710  by adhesive or holding the cable in place using an interference fit or securing medium between the groove  1350  (shown in  FIG.  16   ) and the cable shield  1382  (shown in  FIG.  16   ) of the cable  1340  (shown in  FIG.  16   ). The teeth  1730  of the insert  1710  can secure the first and second cable conductors  1347   a ,  1347   b  (shown in  FIG.  15   ) such that when the first cable connector  120  (shown in  FIG.  1   ) and the second cable connector  130  (shown in  FIG.  1   ) is attached to the board connector  110  (shown in  FIG.  1   ), a respective head  1110 ,  1210  (shown in  FIGS.  11  and  12   ) or opposing contact surfaces  1212  of a respective electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ) of the board connector  110  (shown in  FIG.  1   ) engage only one side of a corresponding first cable conductor  1347   a , such as first contact surface  1397  on the first semicircle  1393 , and only engage on one side of a corresponding second cable conductor  1347   b  on the fourth semicircle  1396  (shown in  FIG.  15   . 
     As shown in  FIG.  19   , the connector shield  1900  can include grooves  1950  that can receive the cable shield  1382  (shown in  FIG.  13   ) of a corresponding cable  1340  (shown in  FIG.  13   ). Slots  1960  can receive the first and second springs  930   a ,  930   b  (shown in  FIG.  9   ) of the ground blade  900  in the board connector  110  (shown in  FIG.  1   ), and arms  1970  about which the insert  1310  (shown in  FIG.  13   ) can be made, for example, by insert molding. The cable shield  1382  (shown in  FIG.  13   ) of the cable  1340  (shown in  FIG.  13   ) can be attached to the groove  1950  by any suitable method, including, for example, by soldering the cable shield  1382  (shown in  FIG.  13   ) of the cable  1340  (shown in  FIG.  13   ) to the groove  1950 . The connector shield  1900  can be made, for example, by stamping a flat metal sheet. 
       FIG.  20    is perspective view of a co-extruded twin axial cable  2040 . The cable  2040  can include an electrically insulative jacket  2043 ; a cable shield  245  that can be wrapped copper, a braid, or other electrically conductive material; a first cable conductor  2047 ; a second cable conductor  2048 ; and a dielectric layer  2049  positioned between the first cable conductor  2047  and the cable shield  245 . First centerline CL1 extends perpendicular or substantially perpendicular to third longitudinal centerline CL3, with the first cable conductor  2047  extending along the third longitudinal centerline CL3. Second centerline CL2 extends perpendicular or substantially perpendicular to fourth longitudinal centerline CL4. The second cable conductor  2048  extends along the fourth longitudinal centerline CL4. The first and second centerlines CL1, CL2 can be parallel to each other. Third and fourth longitudinal centerlines CL3, CL4 can be parallel to each other. 
       FIG.  21    is a close-up view of a tooth  2010  of first and second cable connector  120 ,  130  (shown in  FIG.  1   ) and the electrical contacts  1100 ,  1200  of the board connector  110  (shown in  FIG.  1   ). Each respective first and second cable conductor  2047 ,  2048  can direct and physically contact a corresponding electrical contact  1100 ,  1200 . Only one side, such as first semicircle  2093  or fourth semicircle  2096  of the respective first mating end  2090  or second mating end  2092  of the respective first cable conductor  2047  or second cable conductor  2048  is contacted by a respective opposing surface of a corresponding electrical contact. For example, one opposing surface of a pair of opposing surfaces, such as first contact surface  2012   a , can be electrically connected to only a first semicircle  2093  surface of the first mating end  2090  of the first cable conductor  2047 . Another opposing surface of a pair of opposing surfaces, such as second contact surface  2012   b , can be electrically connected to only a fourth semicircle  2096  surface of the second mating end  2092  of the respective second cable conductor  2048 . 
     The electrical contacts  1100 ,  1200  can each define a respective contact recess  2100 , such that the contact recesses  2100  are mirror images of each other about fifth longitudinal centerline CL5. The combined respective contact recesses  2100  can define a tooth recess  2098  that can receive a corresponding tooth  2010  or a cross-member  2072  of a tooth  2010 . Electrical contacts  1100 ,  1200  can connect electrically with a corresponding first mating end  2090  or second mating end  2092  of a respective first cable conductor  2047  or a second cable conductor  2048 , only at a position along the base  2074  of the tooth  2010 , such as between a body of the insert  2011  and the cross member  2072 . The cross member  2072  can be sized and shaped to extend over the first and fourth semicircles  2093 ,  2096  to physically prevent the electrical contacts  1100 ,  1200  for physically or electrically contacting respective first and second cable conductors  2047 ,  2048  positioned in a corresponding cross member recess  2078 . Each tooth  2010  can be inserted between two opposed, immediately adjacent, facing, corresponding electrical contacts  1100 ,  1200  in direction A, which is perpendicular or substantially perpendicular to the fifth longitudinal centerline CL5. Alternatively, each tooth  2010  can be inserted between two opposed, immediately adjacent, facing corresponding electrical contacts  1100 ,  1200  in direction B, which is parallel to the fifth longitudinal centerline CL5 and perpendicular or substantially perpendicular to direction A. 
     As shown in  FIG.  22   , if an imaginary line such as centerline CL1 or centerline CL2 divides the cross-section of a center conductor such as first cable conductor  1347   a  or second cable conductor  1347   b  into four semicircles, such as first semicircle  1393 , second semicircle  1394 , third semicircle  1395 , and fourth semicircle  1396 , then only one of the semicircles is contacted by a corresponding electrical contact. First semicircle  1393  can define a first contact surface  1397  that electrically contacts a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). Fourth semicircle  1396  can define a second contact surface  1398  that electrically contacts a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). The first and second cable conductors  1347   a ,  1347   b  can be partially or completely surrounded by electrical insulator  142 . A cable shield and jacket are not shown, for clarity. Second and third semicircles  1394 ,  1395  can be configured not to physically touch a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). 
       FIG.  23    shows another embodiment of a third cable connector  2310  connected to a wafer  2300 . The cable connector of  FIG.  23    is similar to the first or second cable connector  1300  of  FIG.  13   . One difference is that insert  2312  of the third cable connector  2310  of  FIG.  23    includes different teeth  2314 . Another difference is that the connector shield  2316  of the third cable connector  2310  of  FIG.  23    extends under the teeth  2314  of the insert  2312 . Electrical contacts  2320  do not have mating surfaces that oppose each other. A web  2340  of dielectric material may be positioned between two electrical contacts  2320  of a differential signal pair. A ground plane  2330  of the board connector wafer  2300  can extend from a mounting interface of the wafer to a mating interface of the wafer  2300 . 
     As shown in  FIG.  24   , a first cable conductor  2347  of the cable  2350  can be held by a tooth  2314  such that a top portion  2321  of first cable conductor  2347  is exposed, i.e. the insulation layer, cable shield, and jacket are removed or the cable is devoid of an insulation layer, cable shield, and jacket adjacent to the exposed first cable conductor  2347 . The same is true for a second cable conductor (not shown). The wafer  2300  can include contact pairs, such a differential signal pairs. The ground plane  2330  of the wafer  2300  can include ground arms  2335  that engage with the connector shield  2316  of the third cable connector  2310 . Any number of ground arms  2335  can be used. The electrical contacts  2320  of the wafer  2300  contact the top portion  2321  of the first cable conductor  2347  (and the second cable conductor) of the third cable connector  2310 . Although not shown, two or more wafers  2300  can be included in or define a board connector, similar to the board connector  310  of  FIG.  4   . Each wafer  2300  can be right angled, which allows the ground plane  2330  to extend the entire or almost the entire length of the electrical contacts  2320 . 
     Each electrical contact  2320  can be cantilevered, including a head  2323  and tail (not shown) that are connected at 90° or approximately 90° within manufacturing tolerances. The heads  2323  in pairs of electrical contacts  2320  can only electrically connect, physically touch, or both, the top portion  2321  of a respective first cable conductor  2347  (and second cable conductor) of the cable  2350 . The heads  2323  can include a lead-in  2325  and a bend  2327  to assist with mating with the first cable conductor  2347  (and the second cable conductor) of the cables  2350  with the corresponding electrical contacts  2320  of the wafer  2300 . The lead-ins  2325  can assist in guiding the teeth  2314  of the third cable connector  2310  when the third cable connectors  2310  are mated with corresponding wafers  2300 . The bend  2327  can be shaped to accommodate an end  2342  of a corresponding tooth  2314 . The third cable connector  2310  can be mated with a corresponding wafer  2300  by pushing the third cable connector  2310  toward the wafer  2300  parallel to direction C. The tail (not shown) can be surface mounted to a substrate. Alternatively, the tail can include a press-fit tail, a through-hole tail, or any other suitable structure to attach the electrical contacts  2320  to the substrate. 
       FIG.  25    shows the third cable connector  2310  shown in  FIGS.  23  and  24   . The third cable connector  2310  is essentially the same as the cable connectors described above, but the teeth  2430  are different. Third cable connector  2310  can include cables  2440 , an insert  2410 , and a connector shield  2420 . Although  FIG.  25    shows three differential signal cables, any number of cables  2440  can be used. The cable  2440  can be a twin axial cable as shown in  FIG.  20   , but it is possible to use other suitable cables, including, for example, a coaxial cable with a single center conductor.  FIG.  24    only shows a portion of the cables  2440  with the exposed cable shield  2445 , but the cables  2440  in  FIG.  25    would typically also include a jacket on the portions not shown in  FIG.  24   . First and second cable conductors  2447   a ,  2447   b  are shown, with respective exposed top portions  2321 . The connector shield  2420  can include grooves  2422  that receive respective cable shields  2445  of the cables  2440 , at least one or a plurality of slots  2460 , and arms (not shown) about which the insert  2410  can be made, for example, by insert molding. The cable shield  2445  can be attached to a respective groove  2422  by any suitable method, including, for example, by soldering the cable shield  2445  to the groove  2422 . The connector shield  2420  can be made, for example, by stamping a flat metal sheet. 
     Once inserted into the insert  2410 , first cable conductor  2447   a  and second cable conductor  2447   b  can be secured to the end of the teeth  2430  by any suitable method. For example, first and second cable conductors  2447   a ,  2447   b  can be held in place by securing the dielectric layer  2480  to the insert  2410  by adhesive or holding the cable  2440  in place using an interference fit or securing medium. The teeth  2430  of the insert  2410  can secure the first and second cable conductors  2447   a ,  2447   b  such that when the third cable connector  2310  is attached to a wafer of a board connector (not shown), the corresponding heads of the electrical contacts of the board connector engage only one side or only the respective top portions  2321  of the first and second cable conductors  2447   a ,  2447   b.    
     Although the insert  2410  of the third cable connector  2310  is shown without a connector shield in  FIG.  26   , the insert  2410  can be made by insert molding the insert  2410  around ground plane arms of a connector shield, similar to  FIG.  19   , so that insert  2410  is integrally formed with the connector shield. The insert  2410  can include a body that defines holes  2470  and with teeth  2430  aligned with the holes  2470 . As with the insert shown in  FIG.  18   , the insert  2410  shown in  FIG.  26    can include a countersunk hole (not shown) into which center conductors, dielectric layer, and shield can be inserted, and two additional countersunk holes that each receive only a respective one of the center conductors. 
       FIG.  27    shows a wafer  2300  shown in  FIGS.  22  and  23   . The wafer  2300  can include electrical contacts  2320  embedded in a wafer body  2302  and a ground plane  2330  attached to a bottom surface of the wafer body  2302 , or the right angle surface of the wafer body  2302  with the shorter mating-to-mounting interface length. The wafer body  2302  can be made from an electrically dielectric material. A web  2340  can extend from the wafer body  2302  in between the pairs of electrical contacts  2320 . The wafer  2300  can be made by insert molding the wafer body  2302  around the electrical contacts  2320  so that wafer body  2302  is integrally formed with the electrical contacts  2320 . The wafer  2300  can include three or more pairs of differential signal electrical contacts  2320 , but any number of contact pairs can be used. The ground arms  2335  of the ground plane  2330  can extend from the ground plane  2330  underneath the pairs of electrical contacts  2320 . The ground plane  2330  can include three ground arms  2335 , but any number of ground arms  2335  can be used. Different height wafers  2300  can be used to connect to first and second cable connectors, with the wafer  2300  connecting to the first cable connector being taller than a wafer connecting to the second cable connector. Wafers  2300  can be stepped in a mating direction. 
     As shown in  FIG.  28   , fifth centerline CL5 passes through midpoints of two adjacent, cross-sectioned center conductors, such as first cable conductor  2447   a  or second cable conductor  2447   b . The fifth centerline CL5 divides the first and second cable conductors  2447   a ,  2447   b  into four semicircles, such as first semicircle  2493 , second semicircle  2494 , third semicircle  2496  and fourth semicircle  2496 . First semicircle  2493  can define a first contact surface  2497  that electrically contacts a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). Fourth semicircle  2496  can define a second contact surface  2498  that electrically contacts a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). The first and second cable conductors  2447   a ,  2447   b  can be partially or completely surrounded by electrical insulator  142 . A cable shield and jacket are not shown for clarity. Second and fourth semicircles  2494 ,  2496  can be configured not to electrically or physically contact a corresponding electrical contact  1100 ,  1200  (shown in  FIGS.  11  and  12   ). 
       FIG.  29    shows a first substrate  2600 , a die  2610 , and a first group of a plurality of connector systems  100 , a first group of a plurality of board connectors  110 , or a first group of first and second cable connectors  120 ,  130 . The die  2610  can also be a chip and can be carried on a first package surface  2620  of the first substrate  2600 . The combination of the first substrate  2600  and the die  2610  can be referred to as a die package  2630 . The first package surface  2620  may carry optional SERDES (serializer/deserializer) chips (not shown), and a plurality of board connectors  110  or a plurality of connector systems  100  that are each a combination of a board connector  110  and a first cable connector  120 , second cable connector  130 , or any of the cable connector embodiments shown in any one of  FIGS.  1 - 28   . The SERDES chips can include 16-by-16-lanes each, or any suitable number of lanes. The board connectors  110  or first or second cable connector  120 ,  130  are in electrical contact with the die. Placing the board connectors  110 , the connector systems  100 , or the first cable connector  120  directly on the die package  2630  helps to eliminate trace losses from the die package  2630  to a host substrate (not shown). 
     The first substrate  2600  can be approximately 145-mm-by-145-mm, such as a printed circuit board, measured along two intersecting first and second die edges  2640 ,  2650  of the first substrate  2600 . The first substrate  2600  can be other sizes too, such as a 70-mm-by-70-mm, an 85-mm-by-85-mm die package, a 120-mm-by-120-mm die package, a 145-mm-by-145-mm die package, a 150-mm-by-150-mm die package, a 230-mm-by-230-mm die package, or other sized die package. The die package is preferably square, but does not have to have sides of equal lengths and can have other shapes. The larger the area of the first substrate  2600 , the more connector systems  100  can be added to the first package surface  2620  or the second package surface  2660 . 
       FIG.  30    shows a second package surface  2660  of the die package  2630 . The second package surface  2660  can include a second group of a plurality of board connectors  110  or a plurality of connector systems  100  that are each a combination of a board connector  110  and a first cable connector  120 , second cable connector  130 , or any of the cable connector embodiments shown in any one of  FIGS.  1 - 28   . At least one of the board connector  110  or the first or second cable connectors  120 ,  130  are electrically connected to the die  2610 . The second package surface  2660  can also define a pin or pad field  2680  that is electrically connected to the die  2610  and can mate electrically with a power source, compression connector, pin connector, interposer, etc. (not shown). The compression or pin connector can exclusively carry power, control, or other sideband signals to the die  2610  or can carry high-speed signals as well. The second package surface  2660  of the die package  2630  can include SERDES (serializer/deserializer) chips, such as 16-by-16 lane SERDES chips. First and second die edges  2640 ,  2650  can have the same respective lengths or can have different lengths. 
     The die package  2630  can therefore include a first substrate  2600  that defines a first package surface  2620 ; a second, opposed package surface  2660 ; a die  2610  carried by the first package surface  2620 ; differential signal connector systems  100  carried by the first package surface  2620 ; and differential signal connector systems  100  carried by the second package surface  2660 . Each differential signal connector system  100  can include a board connector  110  carried by the first package surface  2620 , a board connector  110  carried by the second package surface  2660 , and a first cable connector  120  or a second cable connector  130  releasably attached to each of the board connectors  110 . 
     The electrical connectors can each include one, two, three, or four rows of four differential signal pairs, or any other number of rows, contacts, or differential pairs.  FIG.  29    shows a 145-mm-by-145-mm die package, with the first package surface  2620  populated with die  2610  and thirty-two of the two-row connector systems  100  shown in  FIGS.  1 - 22   . Each first cable connector  120  can include eight differential signal cables  140 , and each second cable connector  130  can include eight differential signal cables  140 , or a total of sixteen differential signal cables per each two-row connector system  100 . As shown on a 145-mm-by-145-mm die package  2630 , thirty-two of the two-row connector systems  100  provide 512 differential signal pairs on the first package surface  2620  of the die package  2630 .  FIG.  30    shows an additional 512 differential signal pairs can be positioned on a second package surface  2660  of the die package  2630 , which provides a total of 1024 differential pairs or 2048 individual cables  140  or 512 lanes per die package  2630 . At a 56 GHz NRZ or 112 GHz PAM4 compliant signal, 1024 differential pairs will facilitate transmission of approximately 50 terabytes of data per second. Two row connector systems  100 , as shown in  FIGS.  29  and  30   , can have a simulated insertion loss of approximately 0 dB to −0.5 dB for frequencies from 0 GHz to 28 GHz. Return loss can be under −15 dB through frequencies up to and including approximately 30 GHz. Near end crosstalk can be under −50 dB through frequencies up to and including approximately 30 GHz. 
     Four row connector systems  100   a  are shown in  FIG.  31   . Each connector system  100   a  can include a board connector  110   a , two first cable connectors  120   a , and two second cable connectors  130   a . Since first and second cable connectors  120   a ,  130   a  are interchangeable, the board connector  100   a  can be populated with only first cable connectors  120   a , only second cable connectors  130   a , or any mixture of the two. The connector systems  100   a  are positioned around a die  2610   a  on a first substrate  2600   a.    
     With four rows of eight differential signal pairs per electrical connector system  100   a , thirty-two twin axial cables or sixty-four single conductor cables  140   a  can be connected to a corresponding one of the board connectors  110   a  carried by any one of the first package surface  2620  of the die package or the second package surface  2660  of the die package  2630 .  FIG.  31    shows four connector systems  100   a  on each of the first and second package surfaces  2620 ,  2660 , but other numbers of connector systems  100   a  can be used. For example, if the die package  2630  shown in  FIG.  31    is 145-mm-by-145-mm, four of the thirty-two pair connector systems  100   a  can fit along each side of the first package surface  2620  and along each side of the second package surface  2660 . This yields the same number of differential signal pairs and channels as the embodiments described and shown with respect to  FIGS.  29  and  30   . The first package surface  2620  of the die package  2630  can include at least 1025 twin axial pairs or approximately 2048 individual cable conductors. If the die package  2630  shown in  FIG.  31    is a 70-mm-by-70-mm die package  2630 , three of the thirty-two pair connector systems  100   a  can fit along each side of the first package surface  2620  and along each side of the second package surface  2660 . This configuration yields at least 768 differential, twin axial pairs or at least 1536 individual cables. With thirty two differential cables per connector system, a 70-mm-by-70-mm die package can support an approximate 37.5 terabyte/sec transmission rate at a 56 GHz NRZ or 112 GHz PAM4 compliant data or signal rate. For 50 Tb/sec throughput, a first substrate  2600  larger than 70-mm-by-70-mm may be needed. 
     One row connector system (not shown) can be approximately 1.5 mm in height. A two row connector system  100  can be approximately 3 mm in height. A three row connector system (not shown) can be approximately 4.5 mm in height. A four row connector system can be approximately 6 mm in height. Height can be measured orthogonally from a mounting interface of a board connector  110  to the highest point on the board connector that is parallel to the mounting interface. 
     In total, on both the first and second surfaces of the die package, a die package in the range of approximately 140 mm by 140 mm to approximately 280 mm by 280 mm can carry at least 1024 twin axial pairs or 2048 individual cable conductors which are routed to respective first electrical panel connectors  2700 , examples of which are shown in  FIG.  32   . 
     With combined reference to  FIGS.  1 ,  23 , and  32   , cable  140  (shown in  FIG.  1   ) can be attached at one end to a respective one of a first, second or third cable connector  120  (shown in  FIG.  1   ),  130  (shown in  FIG.  1   ),  2310  (shown in  FIG.  23   ) and at an opposite end to a respective first electrical panel connector  2700  to form an electrical cable assembly. More specifically, differential signal pairs on an approximate 0.635±0.005 mm pitch carried by the cable can be attached at one end of respective differential signal pairs of one of the first, second, or third cable connectors and at an opposite end of differential signal pairs on an approximate 0.635±0.005 mm pitch carried by a first electrical panel connector. 
     As shown in  FIG.  32   , cable  140  can be shielded twin axial cables or individually shielded coaxial cables (not shown). Cable shields  144  (shown in  FIG.  1   ) are optional. For example, each cable  140  can have a maximum outer diameter of 26-gauge, 27-gauge 28-gauge, 29-gauge, 30-gauge, 31-gauge, 32-gauge, 33-gauge, 34-gauge, 35-gauge, or 36-gauge. Each cable  140  can have a maximum diameter of about 2 mm to about 2.8 mm, within manufacturing tolerances. In one exemplary, non-limiting example, a cable assembly may include a first, a second, and/or a third cable connector  120  (shown in  FIG.  1   ), 130 (shown in  FIG.  1   ), 2310 (shown in  FIG.  23   ) having a height approximately equal to 1.0±0.5 mm, a first electrical panel connector  2700 , and a cable  140  electrically connected to both the first electrical panel connector  2700  and the first, the second, and/or the third cable connector  120  (shown in  FIG.  1   ),  130  (shown in  FIG.  1   ),  2310  (shown in  FIG.  23   ). The cable  140  can have a maximum diameter of 34 or 35 or 36 gauge. Frequency domain NEXT crosstalk of the cable assembly can be between −40 dB to −60 dB through frequencies up to and including 30 GHz, 35 GHz, or 40 GHz or under −40 dB through frequencies up to and including approximately 30 GHz. Data rate is approximately equal to two times the frequency, so the cable assembly can pass approximately 60 Gbits/sec with under −40 dB of NEXT crosstalk. The first electrical panel connector  2700  can be configured not to receive an edge card. 
     As shown in  FIG.  32   , the first electrical panel connector  2700  can be a modified ACCELERATE I/O connector. Standard ACCELERATE connectors are commercially available from SAMTEC, Inc. A modified ACCELERATEC I/O can carry 34 AWG, 35 AWG, or 36 AWG cables. Cables with other gauges are also possible, including, for example, 26 AWG, 27 AWG, 28 AWG, 29 AWG, 30 AWG, 31 AWG, 32 AWG, and 33 AWG. A further modification is the addition of third and fourth rows  2740 ,  2750  of electrical conductors  2710 . Instead of only a first row  2720  of electrical conductors  2710  and a second row  2730  of electrical conductors  2710 , a third row  2740  and a fourth row  2750  of electrical conductors  2710  are added. Each of the first, second, third, and fourth row  2720 ,  2730 ,  2740 ,  2750  can include eight differential signal pairs  2760  and grounds  2770  arranged in a S-S-G or S-S-G-G configuration. A S-S-G-G configuration can reduce signal density. Additional modifications include spacing the first, second, third, and fourth rows  2720 ,  2730 ,  2740 ,  2750  of electrical conductors  2710  on 2.2 mm, 3 mm, and 2.2 mm pitches P1, P2, P3, with an approximate 3 mm space between the second and third rows  2730 ,  2740 . First and second rows  2720 ,  2730  can be spaced apart by an approximate 2.2 mm first row pitch P1. Second and third rows  2730 ,  2740  can be spaced apart by an approximate 3 mm second row pitch P2. Third and fourth rows  2740 ,  2750  can be spaced apart by an approximate 2.2 mm third row pitch P3. Electrical conductors can be on a 0.635±0.05 mm pitch. One or more panel fastener receptacles  2780  can receive panel fasteners 2790 to affix the first electrical panel connector  2700  to a panel, such as the 1 RU panel shown in  FIG.  33   . 
       FIG.  33    shows a face of a 1 RU panel populated with first electrical panel connectors  2700 . Panel fastener receptacles  2780  are reversed compared to  FIG.  32   . Thirty-two of the first electrical panel connectors  2700  can fit within the area of a 1 RU panel, which is approximately 1.75 inches by 19 inches, or approximately 29.75 inches 2 , or approximately 214 cm 2 . First electrical panel connectors  2700  can be vertically stacked such that two first electrical panel connectors  2700 , which may have the same number of differential signal pairs, both fit between two spaced apart, parallel lines L1, L2 that both extend in the 1.75 inch direction of the 1 RU panel, with only two first electrical panel connectors  2700  positioned between the two spaced apart, parallel lines. 
     Worst case embodiments of the present invention can pass or fit at least 768 differential signal pairs through a 1 RU panel area of 42-mm-by-325-mm (approximately 143 cm 2 ), using approximately twenty-four first electrical panel connectors  2700  each carrying thirty-two differential signal pairs and at least 34 AWG cable  140 , with a corresponding throughput of approximately at least 37 Tb/sec. Throughput is more than double the prior art throughput. The number of differential pairs attached to a 1 RU panel, via first electrical panel connectors  2700 , is approximately 256 greater than compared to the prior art. At least 2048 individual cable conductors or 1024 differential twinax of at least 34 AWG cables can terminate to thirty-two or thirty-three of the first electrical panel connectors  2700 , all within an area defined by approximately 1.75 inches by approximately 17 inches, or approximately 29.75 inches 2 , or approximately 192 cm 2 . Corresponding throughput is approximately 50 Tb/sec. t least 1536 individual cable conductors, or 768 twin axial cables, or 384 channels, can fit within a panel area of approximately 21 inches 2  to approximately 26 inches 2 , or approximately 143 cm 2  to approximately 196 centimeters 2 . 
     At least 513 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 143 cm 2 . At least 600 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 143 cm 2 . At least 700 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 143 cm 2 . At least 800 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 149 cm 2 . At least 900 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 168 cm 2 . At least 1000 differential signal pairs can fit within a panel area of 12.8 inches by 1.73 inches, or approximately 186 cm 2 . Each of the first electrical or front panel connectors, alone or in combination, carry differential signals with a frequency domain crosstalk between −40 dB to −60 dB through frequencies up to and including 30 GHz, 35 GHz, or 40 GHz. 
     The number of cables or differential signal pairs that can fit within a 1 RU panel can be independent of the number of first electrical panel connectors  2700 . 1024 differential signal pairs can fit within the area of a 1 RU panel, which is approximately 1.75 inches by 17 inches, or approximately 29.75 inches 2 , or approximately 192 cm 2 . At least 2048 individual cable conductors or 1024 differential twinax cables can terminate to or pass through an area defined by approximately 1.75 inches by approximately 17 inches, or approximately 29.75 inches 2 , or approximately 192 cm 2 . If the cable is reduced in diameter, thirty-two of the first electrical panel connectors  2700  can fit within a panel area of 14.75 inches by 1.75 inches, or approximately 25.8 inches 2 , or approximately 166 cm 2 . Thirty-two of the first electrical panel connectors  2700  can fit within a panel area of 14.75 inches by 1.5 inches, or approximately 22 inches 2 , or approximately 142 cm 2 . 
     At least 513 differential signal cable pairs can attach to respective first electrical panel connectors that take up no more than one half of 1 RU panel area, such as one half of approximately 19 inches by 1.75 inches, or one half of approximately 33 inches 2 , or approximately one half of 213 cm 2 . 
     Any area described herein is not limited to a single 1 RU panel. A panel area can be distributed among two or more 1 RU panels, as long as the combined area taken up by the at least 1024 twin axial, at least 2048 coaxial cables, or the connectors is equal to or less than the area of a single 1 RU panel. The 1 RU panel can define a plurality of panel through holes, like a screen, to permit airflow through the 1 RU panel. 
     As shown in  FIG.  34   , an external cable connector  3200  can mate with a corresponding first electrical panel connector  2700 . Like the first electrical panel connector  2700  (shown in  FIG.  32   ), the external cable connector  3200  can be a modified ACCELERATE connector, commercially available from SAMTEC, Inc., and can carry 26 AWG, 27 AWG, 28 AWG, 29 AWG, or 30 AWG cables. Cables with other gauges can also be used, including, for example, 31 AWG, 32 AWG, 33 AWG, 34 AWG, 35 AWG, or 36 AWG. The external cable connector  3220  can have a first row  3220  of electrical conductors  3210 , a second row of electrical conductors  3210 , a third row of electrical conductors  3210 , and a fourth row of electrical conductors  3250 . The first and second rows can be on an approximate 2.2-mm first row pitch P1. The second and third rows can be on an approximate 3-mm second row pitch P2. The third and fourth rows  3240 ,  3250  can be on an approximate 2.2-mm third row pitch P3. The external cable connector  3200  can define an external cable mating interface that can include electrical conductors  3210 , such as differential signal pairs  3260  and ground conductors  3270 . The electrical conductors  3210  and the ground conductors  3270  can be overmolded and can be carried by individual overmolds. The electrical conductors  3210  can be arranged in a repeating S-S-G configuration, a repeating S-G-S configuration or a repeating S-S-G-G configuration. In a repeating S-S-G configuration, a conductor pitch between adjacent electrical conductors  3210  can be approximately 0.6 mm or 0.635±0.005 mm. A cable pitch between adjacent twin axial cables  140  can be approximately 2.4 mm. 
     It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.