Abstract:
An electrical connector system with an electrical connector having signal contacts exhibiting unwanted cross-talk; and a circuit substrate engaging the connector. The substrate has a plurality of layers and at least first, second and third traces, each corresponding to a respective signal contact. The first trace includes: a first portion on at least one of the layers and adjacent a portion of the second trace in order to produce a first compensating cross-talk; a second portion on at least another of the plurality of layers and adjacent a portion of the third trace in order to produce a second compensating cross-talk. The substrate could also comprise a board having a first layer, a second layer, a plurality of inner layers between said first and second layers, and a ground plane on at least a lower surface of said board. The inner layers have at least first, second and third traces, with the first trace having portions adjacent the second and third traces in order to produce a first and a second compensating cross-talk, respectively. The system reduces unwanted cross-talk by introducing a first compensating cross-talk by inductively and capacitively coupling a first conductor and a second conductor adjacent the first conductor; and introducing a second compensating cross-talk by capacitively coupling the first conductor and a third conductor once removed from the first conductor. The compensating cross-talks offset the unwanted cross-talk to produce an acceptable cross-talk.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical connector systems. More specifically, the present invention relates to electrical connector systems that minimize cross-talk. 
     2. Brief Description of Earlier Developments 
     The continuous increase in the operating speeds of electronic systems and the miniaturization of electrical connectors demand greater control of cross-talk. Cross-talk occurs when electromagnetic energy transmitted through a conductor in the connector causes electrical currents in the another conductor in the electrical connector. Near-end cross-talk (NEXT) travels in a direction opposite to the signal in the conductor. As an example, ANSI/EIA/TIA/568A Category 5 requirements limit pair-to-pair NEXT to −40 dB at 100 MHz. Some applications require such cross-talk performance, but measured on a power sum basis. 
     Various attempts have been made to control cross-talk within the connector. U.S. Pat. No. 5,562,479 describes an electrical connector in which a mating portion of the connector produces a “positive” cross-talk. Another portion of the connector arranges the conductors side-by-side in a plane to produce a “negative” cross-talk. The “negative” cross-talk cancels out the “positive” cross-talk. 
     U.S. Pat. No. 5,647,770 describes a modular jack in which adjacent conductor wires are crossed over for a portion of a length along an insert. The cross-talk produced in the cross-over portion cancels out the cross-talk produced in the portions of the conductor wire that are not crossed-over. 
     Various attempts have also been made to control cross-talk outside of the connector. British Patent Application GB 2 314 466 describes a compensation pattern on a multi-layer board (MLB) to which contacts from an electrical connector secure. The pattern uses vertically aligned arrays of conductive paths. Capacitive coupling between adjacent unlike paths produces a cross-talk that reduces the cross-talk produced by the connector. The pattern also staggers adjacent paths on a layer in order to allow coupling between non-adjacent paths. 
     European Patent Application number EP 0 854 664 also describes a compensation pattern on an MLB to which the electrical connector contacts connect. A portion of the conductive paths extend along one layer, while the remainder extends along another layer vertically spaced therefrom. The arrangement of the paths ensures that one path of a pair overlies at least two paths, each from a different pair. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electrical connector system that exhibits suitable cross-talk characteristics. 
     It is a further object of the present invention to provide a compensation pattern on a multi-layer circuit substrate that reduces cross-talk in the connector to a desired level. 
     It is a further object of the present invention to provide a compensation pattern on a multi-layer circuit substrate that inductively and capacitively couples various differential signal pairs in order to reduce cross-talk to a desired level. 
     It is a further object of the present invention to provide a multi-layer circuit substrate with a compensation pattern having relatively small dimensions. 
     It is a further object of the present invention to provide a multi-layer circuit substrate with a compensation pattern sized to fit within a shield that surrounds the electrical connector secured to the circuit substrate. 
     It is a further object of the present invention to provide a multi-layer circuit substrate with a trace pattern that compensates for adjacent and non-adjacent conductors. 
     These and other objects of the present invention are achieved in one aspect of the present invention by an electrical connector system, comprising: an electrical connector having a plurality of signal contacts and in which the signal contacts exhibit unwanted cross-talk; and a circuit substrate engaging said connector. The substrate has a plurality of layers; and at least first, second and third traces on the circuit substrate, each corresponding to a respective signal contact. The first trace includes: a first portion on at least one of the plurality of layers and adjacent a portion of the second trace in order to produce a first compensating cross-talk; a second portion on at least one other of the plurality of layers and adjacent a portion of the third trace in order to produce a second compensating cross-talk. The first and second compensating cross-talks offset the unwanted cross-talk to provide an acceptable cross-talk. 
     These and other objects of the present invention are achieved in another aspect of the present invention by a circuit substrate for creating compensating cross-talk that minimizes unwanted cross-talk in signal contacts of an electrical connector. The substrate comprises a board having a first layer, a second layer, a plurality of inner layers between said first and second layers, and a ground plane on at least a lower surface of said board; at least first, second and third traces on the inner layers, the first trace having portions adjacent the second and third traces in order to produce a first and a second compensating cross-talk, respectively. The first and second compensating cross-talks offset the unwanted cross-talk to produce an acceptable cross-talk. 
     These and other objects of the present invention are achieved in another aspect of the present invention by a method of reducing unwanted cross-talk in an array of at least three conductors, comprising the steps of: introducing a first compensating cross-talk by inductively and capacitively coupling a first conductor and a second conductor adjacent the first conductor; and introducing a second compensating cross-talk by capacitively coupling the first conductor and a third conductor once removed from the first conductor. The compensating cross-talks offset the unwanted cross-talk to produce an acceptable crosstalk. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which: 
     FIGS. 1A and 1B are front and side perspective views, respectively, of an electrical connector of the present invention; 
     FIGS. 2A and 2B are front and side elevational views, respectively, of the electrical connector in FIGS. 1A and 1B with an exterior shield; 
     FIG. 3A is a top view of an electrical cable assembly mateable with the electrical connector in FIGS. 1A and 1B; 
     FIG. 3B is a front view of the electrical cable assembly in FIG. 3A; 
     FIG. 4 is a partial cross-sectional view of one alternative embodiment of a multi-layer circuit substrate of the present invention taken along line IV—IV of FIG. 5; 
     FIG. 5 is a plan view of the multi-layer circuit substrate shown in FIG. 4; 
     FIG. 6A is a plan view of one layer of the multi-layer circuit substrate shown in FIG. 4; 
     FIG. 6B is a detailed view of a part of the layer in FIG. 6A with conductors from an adjacent layer shown in phantom; 
     FIG. 7 is a plan view of another layer of the multi-layer circuit substrate shown in FIG. 4; 
     FIG. 8A is a plan view of another layer of the multi-layer circuit substrate shown in FIG. 4; 
     FIG. 8B is a detailed view of a part of the layer in FIG. 8A with conductors from an adjacent layer shown in phantom; 
     FIG. 9 is a plan view of another layer of the multi-layer circuit substrate shown in FIG. 4; 
     FIG. 10 is a cross-sectional view of another alternative embodiment of a multi-layer circuit substrate of the present invention taken along lines X—X in FIG. 11A; 
     FIG. 11A is a plan view of a layer of the multi-layer circuit substrate shown in FIG. 10; 
     FIG. 11B is the layer shown in FIG. 11 with the conductors from an adjacent layer shown in phantom; 
     FIG. 12 is a plan view of another layer of the multi-layer circuit substrate shown in FIG. 10; 
     FIG. 13 is a cross-sectional view of another alternative embodiment of a multi-layer circuit substrate of the present invention taken along lines XIII—XIII of FIG. 14; 
     FIG. 14 is a plan view of one layer of the multi-layer circuit substrate shown in FIG. 13; and 
     FIG. 15 is a plan view of another layer of the multi-layer circuit substrate shown in FIG.  13 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A and 1B display an electrical connector  101 , which could be a Category 5, 25 pair PCB receptacle connector such as part number 92509 available from FCI. Since a detailed recitation of the features of receptacle  101  is unnecessary for an understanding of the present invention, only a brief summary follows. 
     Receptacle  101  has an insulative housing  103  made from a suitable material such as 40% glass fiber reinforced polyphenylene sulfide (PPS). A series of contacts  105  extend through housing  103 . Contacts  105  can be made from any suitable conductive material, including phosphorbronze, with a suitable plating finish, such as gold over nickel. 
     Receptacle  101  includes a mating portion  107  extending from a front face  109 . A metal shell  111  covers front face  109  and surrounds the perimeter of mating portion  107 . Mating portion  107  has a central opening  113  that accepts a mating electrical connector therein. 
     The mating ends of contacts  105  reside within mating portion  107  in two opposed rows. The mating ends of contacts  105  could be cantilever beams or propped cantilever beams which engage contacts in the mating electrical connector. As seen in FIG. 2A, superimposed contacts  105   a ,  105   b  within mating portion  107  define the differential pairs. 
     Contacts  105  extend past a mounting portion  115  of receptacle  101 , for example, to engage through holes in a circuit substrate. The tails of contacts  105  extend from receptacle  101  in two rows. Mounting portion  113  could also include hold downs  117  that engage through holes in the circuit substrate to secure receptacle  101  temporarily to the circuit substrate before soldering. 
     As shown in FIGS. 2A and 2B, receptacle  101  could also have an outer shield  119  to shield any electrical components surrounding receptacle  101  from electromagnetic interference (EMI) which could induce common mode noise in the cable. Shield  119  is preferably formed from a sheet of conductive material, such as phosphor bronze with a hot dip tin finish. Aside from an opening  121  through which mating portion  107  and shell  111  extend and the side abuts the circuit substrate, shield  119  surrounds receptacle  101 . Shield  119  can include terminals  123  that enter through holes in the circuit substrate. 
     Receptacle  101  mates with a suitable electrical connector, such as a Category 5, 25 pair cable plug  201  shown in FIGS. 3A and 3B. Plug  201  could, for example, be part number 86005 available from FCI. As with receptacle  101 , a detailed recitation of the features of plug  201  is unnecessary for an understanding of the present invention. Thus, only a brief summary follows. 
     Plug  201  includes a cable  203  that terminates within a housing  205  made from a suitable insulative material, such as a thermoplastic. Housing  205  has a plate  207  extending from a mating face  209 . Plate  209  enters opening  113  in mating portion  107  of receptacle  101  during mating. 
     A plurality contacts  211 , such as insulation displacement contacts or any other suitable type of contact, extend through housing  205 . Contacts  211  are preferably phosphor bronze with a gold over nickel finish in the contact area and a tin-lead over nickel finish in the terminal area. 
     One end of each contact  211  terminates to a respective wire  213  in the cable  203 . The mating ends of each contact  213  extends along plate  207 . As with receptacle  101 , the mating ends of contacts  213  are arranged in two rows, each on an opposite side of plate  207 . As seen in FIG. 3B, superimposed contacts  211   a ,  211   b  extending from housing  205  define the differential pairs. Upon mating of receptacle  101  and plug  201 , contacts  211  engage contacts  105 . 
     As with any connector system, cross-talk occurs between conductors in receptacle  101  and plug  201  (hereinafter referred to as unwanted cross-talk). The present invention introduces a cross-talk (hereinafter referred to as a compensating cross-talk) to each differential pair of the electrical connector system in order to reduce, or even cancel, the unwanted cross-talk. The present invention uses a predetermined pattern of traces on a portion of a multi-layer circuit substrate to introduce the compensating cross-talk. The compensating cross-talk described throughout may be in addition to any compensating cross-talk introducing within the connectors (not shown). 
     FIGS. 4-9 demonstrate a first alternative embodiment of a circuit substrate to which receptacle  101  mounts. The circuit substrate is made from a suitable dielectric material, such as a glass reinforced epoxy resin like FR 4 . The substrate comprises a plurality of layers formed by conventional techniques and sandwiched together by, for example, adhesive. In the particular arrangement shown in FIG. 4, multi-layer board (MLB)  301  should include at least  6  conductor layers. 
     FIG. 5 displays an upper surface  303  of MLB  301 , which is a part of an upper layer  305 . Receptacle  101  mounts to upper surface  303  of MLB  301 . In order to receive receptacle  101 , upper layer  305  has plated through holes  307 ,  309  which correspond to and receive terminals  123  of shield  119  and hold downs  117  of receptacle  101 , respectively, and which connect terminals  123  and hold downs  117  to the ground planes of MLB  301 . Upper layer  303  also includes plated through holes  311  that receive the tails of contacts  105  of receptacle  101  and vias  313  to which the other circuitry (not shown) on MLB  301  are routed. In one possible arrangement and as shown in FIG. 5, through holes  311  could be arranged in two rows, while vias  313  are arranged in a single row. Other arrangements, however, are possible. 
     Most of the remainder of upper layer  303  could be a ground plane as illustrated in FIG.  5 . In other words, the additional areas shown in FIG. 5, except where a clearance is needed at a plated through hole carrying a signal, could have a ground plane. If, however, receptacle  101  uses shield  119 , then the ground plane in the area under shield  119  may be unnecessary (as seen in FIG.  5 ). 
     Similarly, a sixth layer  317  also preferably has a ground plane at locations other than those locations necessary for creating a clearance with a plated through hole carrying a signal. Sixth layer  317  is preferably a lower surface  315  of MLB  301 . If more than six layers were necessary, then the additional areas would reside between upper first and sixth layers  305 ,  317 . In a preferred embodiment, a 0.030″ spacing exists between the ground plane on sixth layer  317  and the conductors on the fifth layer. As discussed above, should MLB  301  require more than six layers, the spacing between the conductors on the fifth layer and the ground plane on sixth layer  317  would be greater. 
     As discussed in more detail below, a predetermined arrangement of conductive paths extending between through holes  311  and vias  313  and on the various layers of MLB  301  to form the compensation pattern used to offset the unwanted cross-talk. The conductive paths are formed on the layers using conventional techniques such as photolithography. Generally speaking, each differential pair of traces or conductors DP n  comprises two conductors C n,a  and C n,b . As an example, differential pair DP 1  has a first conductor C 1,a  and a second conductor C 1,b . 
     A second layer  319  and an adjacent third layer  321  are preferably used to create a compensating cross-talk that offsets unwanted cross-talk between adjacent conductors. Preferably, upper first layer  303  maintains a distance of approximately 0.030″ from the conductors on second layer  319 . 
     Second and third layers  319 ,  321  preferably utilize inductive and capacitive coupling between adjacent differential pairs DP n , DP n+1  to create the compensating cross-talk. Inductive coupling occurs because the conductors carry current between through holes  311  and vias  313 . To achieve the capacitive coupling, conductors from adjacent differential pairs reside on alternating layers. For example, FIG. 6A displays second layer  319  having conductors thereon from a first differential pair DP 1 , a third differential pair DP 3  and a fifth differential pair DP 5 . 
     FIG. 7 displays third layer  321  having conductors thereon from a second differential pair DP 2  and a fourth differential pair DP 4 . In a preferred embodiment, conductors on second and third layer  319 ,  321  are vertically spaced approximately 0.005″. 
     Referring to FIG. 6A, each conductor of alternating differential pairs extend from through hole  311  to via  313  on second layer  319 . Referring to the detailed view of FIG. 6B, conductor C 3,a  includes a longitudinally extending portion  323  flanked by laterally extending portions  325 ,  327 . Lateral portions  325 ,  327  ensure that longitudinal portion  323  generally extends to via  313  from a location generally between adjacent through holes  311 . 
     Conductor C 3,b  includes a laterally extending portion  329  and a longitudinally extending portion  331 . Lateral portion  329  ensures that longitudinal portion  331  generally extends to via  313  from a location generally between adjacent through holes, but on an opposite side of through hole  311  from conductor C 3,a . 
     Third layer  321  has the same conductor pattern as second layer  319 . The only difference between third layer  321  and second layer  319  is that each layer accommodates different differential pairs. FIG. 7 shows, for example, that conductors C 2,a  and C 2,b  on third layer  321  follow the same pattern as conductors C 3,a  and C 3,b  on second layer  319 . 
     In addition to positioning longitudinal portions  323 ,  331  relative to through holes  311 , lateral portions  325 ,  327 ,  329  also position longitudinal portions  323 ,  331  relative to the longitudinal portions of the conductors on third layer  321 . As seen in FIG. 6B, an overlap O occurs between certain conductors on second layer  319  and third layer  321 . This overlap  0  creates the compensating cross-talk to offset unwanted cross-talk between adjacent pairs (e.g. DP n , DP n+1 ). 
     The geometry of the conductors and the spacing between second layer  319  and third layer  321  determines the amount of compensating cross-talk. Each conductor on second and third layer  319 ,  321  has a narrow interconnection portion and a wide compensation portion. The compensation discussed herein generally occurs in the wide portion of the conductors. 
     FIG. 6B demonstrates that lateral portion  325  of conductor C 3,a  forms the narrow portion and longitudinal portion  323  and lateral portion  327  form the wide portions. FIG. 6B also demonstrates that lateral portion  329  and a portion of longitudinal portion  331  of conductor C 3,b  form the narrow portion and the remainder of longitudinal portion  331  forms the wide portion. 
     Therefore, as clearly shown in FIG. 6B, the wide portions of the conductors occupy the overlaps  0  with the conductors on the adjacent layer of MLB  301 . Width W of the wide portions of the conductors is selected to produce the desired amount of compensating cross-talk. In fact, the width W suitable to form the desired amount of compensating cross-talk depends upon a length L between through holes  311  and vias  313 . Generally speaking, for wider widths W, the optimum length L is shorter, but the resulting power sum cross-talk is larger. 
     For example, with a length L of 0.282″ between a 0.052″ diameter pad at through hole  311  and a 0.0290″ diameter pad at via  313 , a 0.001″ thick conductor should have a wide portion width of 0.016″. The narrow portion width could be approximately 0.008″. 
     Subsequent layers of MLB  301  are preferably used to create a compensating cross-talk that offsets unwanted cross-talk between non-adjacent conductors. The remaining layers preferably use capacitive coupling between non-adjacent differential pairs to create the compensating cross-talk. Preferably, the conductors of the subsequent layers are spaced approximately 0.011″ from the conductors in third layer  321 . 
     In order to clarify the terminology used below, FIG. 6A shows that third differential pair DP 3  is “once removed” from first differential pair DP 1 . In other words, second differential pair DP 2  resides between first differential pair DP 1  and third differential pair DP 3 . Furthermore, fourth differential pair DP 4  is “twice removed” from differential pair DP 1 . In other words, second and third differential pairs DP 2 , DP 3  reside between first differential pair DP 1  and fourth differential pair DP 4 . 
     In this alternative embodiment, a fourth layer  333  and an adjacent fifth layer  335  create a compensating cross-talk to offset unwanted crosstalk between once removed conductors. To achieve this goal, each conductor C n,a , C n,b  from a differential pair DP n  reside on alternating layers. For example, FIG. 8A displays fourth layer  333  having conductor C 3,a  from differential pair DP 3 . The other conductor C 3,b  from differential pair DP 3  resides on fifth layer  335 . In a preferred embodiment, conductors on fourth and fifth layer  333 ,  335  are vertically spaced approximately 0.005″. 
     Referring to the detailed view of FIG. 8B, conductor C 3,a  is a stub, not fully extending between through hole  311  and via  313 . Conductor C 3,a  has a laterally extending portion  337  and a longitudinally extending portion  339 . Laterally extending portion  337  aligns longitudinal portion  339  with an adjacent via  313 . 
     Fifth layer  335  has a somewhat similar arrangement. Referring to FIG. 9, conductor C 2,b  is a stub, not fully extending between through hole  311  and via  313 . Conductor C 2,b  has a laterally extending portion  341  and a longitudinally extending portion  343 . Laterally extending portion  341  aligns longitudinal portion  343  with an adjacent via  313 . In particular, and as shown in FIG. 8B, lateral portions  337 ,  341  position their respective longitudinal portions  339 ,  343  so as to overlap O. This overlap creates the compensating cross-talk to offset unwanted cross-talk between once removed pairs (e.g. DP n , DP n+2 ). 
     The geometry of the conductors and the spacing between fourth and fifth layers  333 ,  335  determines the amount of compensating cross-talk. Each conductor on fourth and fifth layers  333 ,  335  has a narrow portion and a wide portion. For example, FIGS. 8A and 9 demonstrate that lateral portions  337 ,  341  of conductors C 3,a , C 2,b  form the narrow portions and longitudinal portions  339 ,  343  form the wide portions. 
     Therefore, as clearly shown in FIG. 8B, the wide portions of the conductors occupy the overlaps O with the conductors on the adjacent layer of MLB  301 . Width WS of the wide portions of the conductors is selected to form the desired amount of compensating cross-talk. In fact, the width W. suitable to form the desired amount of compensating cross-talk depends upon a stub length L s . Generally speaking, for longer stub lengths L s , width W should be smaller. 
     For example, with a length L of 0.282″ between a 0.052″ diameter pad at through hole  311  and a 0.0290″ diameter pad at via  313 , a 0.001″ thick conductor with a stub length L. of 0.249″ should have a wide portion width of 0.016″. The narrow portion width could be approximately 0.008″. 
     FIGS. 10-12 display a second alternative embodiment of a circuit substrate to which receptacle  101  mounts. As with the first alternative embodiment, the substrate comprises a plurality of layers. Different than MLB  301 , a multi-layer board (MLB)  401  of the second alternative embodiment has at least two more layers. 
     Features of MLB  401  that are similar to MLB  301  will now be briefly discussed. MLB  401  has a upper layer  405 , second layer  419 , third layer  421 , fourth layer  433  and fifth layer  435 . Upper layer  405  includes an upper surface of MLB  401  and interacts with receptacle  101 . Second and third layers  419 ,  421  create a compensating cross-talk between adjacent conductors (such as second and third differential pairs DP 2 , DP 3 ). Fourth and fifth layers  433 ,  435  create a compensating cross-talk between once removed conductors (such as second and fourth differential pairs DP 2 , DP 4 ). 
     Differently than MLB  301 , MLB  401  includes at least two additional layers that create compensating cross-talk in the conductors. MLB  401  includes a sixth layer  445  and an adjacent seventh layer  447 . Preferably, conductors on sixth and seventh layers  445 ,  447  are vertically spaced approximately 0.005″. 
     First layer  405  and an eighth layer  449  flank second, third, fourth, fifth, sixth and seventh layers  419 ,  421 ,  433 ,  435 ,  445 ,  447 . Preferably, first and eighth layers  405 ,  449  comprise ground planes. As with the first alternative embodiment, no ground plane may be necessary on upper layer  405  in the region of the compensation pattern should receptacle  101  include shield  119 . 
     Sixth and seventh layers  445 ,  447  preferably create a compensating cross-talk that offsets unwanted cross-talk between twice removed conductors. To achieve this goal, each conductor C n,a , C n,b  from a differential pair DP n  resides on alternating layers. For example, FIG. 11A displays sixth layer  445  having conductor C 13,b  from thirteenth differential pair DP 13 . The other conductor C 13,a  from thirteenth differential pair DP 13  resides on seventh layer  447 . 
     Referring to FIG. 11A, conductor C 13,b  is a stub, not fully extending between the rows of through holes  411 . Conductor C 13,b  extends diagonally from through hole  411  associated with thirteenth differential pair DP 13  towards through hole  411  associated with a sixteenth differential pair DP 16 . 
     Seventh layer  447  has a similar arrangement. Referring to FIG. 12, conductor C 16,a  is a stub, not fully extending between the rows of through holes  411 . Conductor C 16,a  extends diagonally from through hole  411  associated with sixteenth differential pair DP 16  towards through hole  411  associated with a thirteenth differential pair DP 13 . The positioning of the conductors provides an overlap O between twice removed conductors as seen in FIG.  11 B. This overlap O creates the compensating cross-talk to offset the unwanted cross-talk between twice removed pairs (e.g. DP n , DP n+3 ). 
     The geometry of the conductors and the spacing between the sixth and seventh layers  445 ,  447  determines the amount of compensating cross-talk. Each conductor on sixth and seventh layers  445 ,  447  preferably has a generally uniform width. The width of the conductors is selected to form the desired amount of compensating cross-talk. In fact, the width suitable to form the desired amount of compensating cross-talk depends on the length of overlap O. Generally speaking, for longer lengths of overlap O, the smaller the width of the conductor can be. For shorter lengths of overlap O, the greater the width of the conductor can be. 
     For example, it is estimated that with an overlap O of approximately 0.100″, a 0.0011″ thick conductor should have a width of approximately 0.016″. 
     FIGS. 13-15 display a third alternative embodiment of a circuit substrate to which receptacle  101  mounts. In this alternative embodiment, the substrate comprises a multi-layer board (MLB)  501 . MLB  501  closely resembles MLB  401 , save the sixth and seventh layers. 
     As seen in FIG. 13, a sixth layer  545  and an adjacent seventh layer  547  have conductors thereon. As with the second alternative embodiment, sixth and seventh layers  445 ,  447  preferably create a compensating cross-talk that offsets unwanted cross-talk between twice removed conductors. FIGS. 14 and 15 demonstrate the particular arrangement of conductors on the sixth and seventh layers  445 ,  447 . 
     As seen in FIG. 14, sixth layer  545  displays conductor C 16,b  from sixteenth differential pair DP 16  extending forwardly to a position adjacent conductor C 13,a  from thirteenth differential pair DP 13 . Conductors C 16,b , C 13,a  extend adjacently at an area A to create the necessary compensating cross-talk between twice removed conductors. 
     The other conductor C 16,a  from sixteenth differential pair DP 16  extends forwardly to a position adjacent conductor C 19,b  from nineteenth differential pair DP 19 . Conductors C 16,a , C 19,b  extend adjacently at an area A to create the necessary compensating cross-talk between twice removed conductors. 
     The conductors from an adjacent differential pair extend rearwardly to overlap with their corresponding twice removed conductors. As seen in FIG. 14, conductor C 17,b  from seventeenth differential pair DP 17  extends rearwardly to a position adjacent conductor C 14,a  from fourteenth differential pair DP 14 . The other conductor C 17,a  from seventeenth differential pair DP 17  extends rearwardly to a position adjacent conductor C 20,b  from twentieth differential pair DP 20 . 
     As seen in FIG. 15, seventh layer  547  displays conductor C 15,b  from fifteenth differential pair DP 15  extending forwardly to a position adjacent conductor C 12,a  from twelfth differential pair DP 12 . An overlap O between conductors C 15,b , C 12,a  extend adjacently at area A to create the necessary compensating cross-talk between twice removed conductors. 
     The other conductor C 15,a  from fifteenth differential pair DP 15  extends forwardly to a position adjacent conductor C 18,b  from eighteenth differential pair DP 18 . Conductors C 15,a , C 18,b  c extend adjacently at area A to create the necessary compensating cross-talk between twice removed conductors. Comparing FIGS. 14 and 15, the conductors on seventh layer  547  extend further from through holes  511  than the conductors on sixth layer  545 . This prevents any adverse cross-talk between the conductors on the adjacent sixth and seventh layers  545 ,  547 . Alternatively, however, the conductors on seventh layer  547  could extend to a position medial the rows of through holes  511  (not shown). This location would also prevent adverse cross-talk between conductors on the adjacent sixth and seventh layers  545 ,  547 . 
     Referring to FIGS. 14 and 15, the conductors are stubs, not electrically connecting through holes  411 . The geometry of the conductors and the spacing between the sixth and seventh layers  545 ,  547  and between adjacent conductors determines the amount of compensating cross-talk. Each conductor on sixth and seventh layers  545 ,  547  preferably has a generally uniform width. The width of the conductors and a gap G between the conductors is selected to form the desired amount of compensating cross-talk. 
     In fact, the width suitable to form the desired amount of compensating cross-talk depends on the length of an overlap A. Generally speaking, for smaller gaps G, the smaller the length of overlap A can be. For greater lengths of gaps G, the greater the length of overlap A can be. 
     For example, with a gap G of 0.006″ and a width W of 0.008″, it is estimated that a 0.001″ thick conductor should have a length of overlap A of approximately 0.150″. 
     While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.