Abstract:
In accordance with a non-limiting example, a connector mates to a circuit board at a connector interface. The connector often introduces an undesirable level of crosstalk between pairs. Traces are formed on the circuit board in a “compensation region” that also introduces crosstalk between pairs. The “compensation region” is created in a geometrically controlled fashion such that the crosstalk in the compensation region is of equal magnitude, but opposing phase to the crosstalk introduced by the connector. Thus, the overall crosstalk is minimized.

Description:
BACKGROUND 
     Miniature ribbon connectors such as the Champ™ ribbon connector introduce an undesirable level of crosstalk between connector pairs for some applications. As always, this crosstalk results from the specific geometry of the ribbon connector. As applications are pushing to ever higher bandwidths, a number of proposals have been made to reduce the resulting connector crosstalk. Some proposals have attempted to twist components or wires inside the ribbon connector in a unique geometric arrangement to reduce the crosstalk. This solution adds extensively to the manufacturing costs of the ribbon connector, however. Another proposal that has been commercialized is to deviate from the historical pin assignments. The historical pin assignment of tip/ring pairs in the connector, which is referred to as a “standard pinout,” is not optimal from a crosstalk perspective as it creates a large amount of inductive coupling. By re-assigning the pins, the coupling can be made predominantly capacitive. Counter-balancing capacitive coupling is then built into the connector. In addition to adding significant cost, this method creates compatibility problems with a huge base of installed equipment utilizing the historical pin assignments. 
     SUMMARY 
     In accordance with a non-limiting example, a connector mates to a circuit board at a connector interface. The connector often introduces an undesirable level of crosstalk between pairs. Traces are formed on the circuit board in a “compensation region” that also introduces crosstalk between pairs. The “compensation region” is created in a geometrically controlled fashion such that the crosstalk in the compensation region is of equal magnitude but opposing phase to the crosstalk introduced by the connector. Thus, the overall crosstalk is minimized. 
     In one example, the compensation region is optimized geometrically to minimize the crosstalk to the nearest neighbor pairs (for example, T3/R3 to T4/R4 and T2/R2). In another example, the geometry is configured to minimize the total crosstalk from all aggressors, resulting in an effective CAT-5 compliant connector from a standard ribbon connector. 
     A method of forming the circuit board is also set forth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will become apparent from the detailed description of the invention which follows, when considered in light of the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a circuit board and conventional connector system for coupling electronic modules on a circuit board to a connector. 
         FIG. 2  is a sectional view taken along tip and ring conductors and showing the connector interface and flux lines. 
         FIG. 3  is a plan view of the conventional circuit board shown in  FIG. 1 . 
         FIG. 4  is a plan view of a circuit board and showing a connector system for coupling electronic modules to the connector in accordance with a non-limiting example and showing a compensator trace pattern. 
         FIG. 5  is an enlarged sectional view of the conventional trace pattern shown in  FIG. 3 . 
         FIG. 6  is an enlarged sectional view of the compensator trace pattern shown in  FIG. 4 . 
         FIG. 7  is a graph of connector characteristics in accordance with a non-limiting example and showing the signal level of an aggressor on the vertical axis and frequency in hertz for the connector only on the horizontal axis. 
         FIG. 8  is a graph similar to that shown in  FIG. 7  and showing compensator improvements and showing the signal level of the aggressor on the vertical axis and the frequency in hertz on the horizontal axis. 
         FIG. 8A  is a graph showing tradeoffs between NEXT and FEXT cancellation versus compensation region length. 
         FIG. 9  is another graph similar to those shown in  FIGS. 7 and 8  and showing the next-nearest neighbor (for example, T7/R7 to T9/R9) crosstalk characteristics in accordance with a non-limiting example. 
         FIG. 10A  is a plan view of a trace arrangement of a CAT5 compensator and configured to satisfy the CAT5 requirements. 
         FIG. 10B  is a perspective view of an example compensation region. 
         FIG. 10C  is another perspective view of the example compensation region showing configuration details at each end of the compensation region. 
         FIG. 11  is another graph similar to those shown in  FIGS. 7-9  and showing the performance of a CAT 5 compensator in accordance with a non-limiting example. 
         FIG. 12  is a flow chart of an example process for cancelling crosstalk. 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of this document will now be described more fully hereinafter with reference to the accompanying drawings. This subject matter may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth herein. Rather, examples are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout. 
       FIG. 1  is a fragmentary side elevation view of a printed circuit board  20  and showing a conventional system  10  for coupling electronic modules  70  to a connector  22  and showing the unshielded twisted wire pair  18  with tip and ring conductors. The connector  22 , a connector interface  28 , and various pins to which the twisted pair tip and ring conductors connect are illustrated. A large conductor loop  24  is formed inside the connector. The printed circuit board  20  is formed from a substrate  52  and a first opposing side  54  and second opposing side  56 , including a top trace  57  and bottom trace  58 . The connector  22  in one example is formed as a right-angle connector such as the Champ™ ribbon connector. 
       FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1  and showing a number of pins  30  and how the historical pinout geometry results in both inductive and capacitive coupling and showing example dimensions. A Tip and a Ring (e.g., T2/R2) constitute a wire pair, which is also referred to as a conductor pair or pair of conductors. The flux lines  32  from one wire pair readily penetrate other wire pair loops, creating inductive crosstalk. In addition, the pin spacing creates a capacitive imbalance where C1≠C2, resulting in capacitive crosstalk in a differential system. 
       FIG. 3  is a plan view of the conventional prior art connector system  10  such as shown in the sectional view of  FIG. 1  and showing the connector  22  and the unshielded twisted pairs  18  that are associated with the connector  22 . The conventional connector system  10  includes a conventional trace arrangement or fanout pattern  42  that connects to different electronic modules or components, such as transmitter/receiver or other such devices  70 . In the conventional fanout pattern  42 , pair-to-pair coupling is considered undesirable and is avoided as much as possible. 
       FIG. 5  is a sectional view of the trace arrangement or pattern  42  on the circuit board as shown in  FIG. 3  and showing the gap  36  between traces, with the top traces corresponding to the tip conductors  44  and the bottom traces corresponding to the ring conductors  46 . 
       FIG. 4  is a plan view of the connector system  100  for coupling electronic modules  70  to a connector  22  in accordance with a non-limiting example, and showing a compensator  110  that includes compensator traces in which the length of the traces for the compensator are illustrated at  118 . The conventional fanout pattern  42  begins after the compensator  110 . 
       FIG. 6  is a sectional view of the compensator region showing the substrate  52 , compensator conductors (also referred to as traces)  114 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  132 ,  134 , and  136 . As illustrated by  FIG. 6 , conductors  114  and  116  form a first pair of conductors (“first pair”), while the conductors  118  and  120  form a nearest neighbor pair of conductors (“NNP” or “nearest neighbor”) relative to the first pair (e.g.,  114  and  116 ). As used throughout this document, an NNP is a pair of conductors that are formed adjacent to another pair of conductors. For example, conductors  118  and  120  are formed adjacent to conductors  114  and  116 , such that conductors  118  and  120  are an NNP relative to the conductors  114  and  116 . Similarly, conductors  114  and  116  are also considered an NNP relative to conductors  118  and  120 . 
     Conductors  122  and  124  form a next nearest neighbor pair of conductors (“NNN” or “next nearest neighbor”) relative to the first pair (e.g., conductors  114  and  116 ). As used throughout this document, a next nearest neighbor pair of conductors are a pair of conductors that are separated from a given pair of conductors by another pair of conductors. For example, conductors  122  and  124  are considered an NNN relative to the first pair (e.g., conductors  114  and  116 ) because the conductors  118  and  120  are located between the first pair and the conductors  122  and  124 . Similarly, conductors  122  and  124  are an NNN relative to conductors  130  and  132  because the pair of conductors  126  and  128  are located between the pair of conductors  122 / 124  and the pair of conductors  130 / 132 . 
     As shown in  FIG. 6 , the pair of conductors  118  and  120  are twisted relative to the conductors  114  and  116 . That is, the tip “T1” (i.e., conductor  114 ) is located on one side of the substrate  52 , while the tip “T2” (i.e., conductor  120 ) is located on a different side of the substrate  52 . The conductors  122  and  124  are similarly twisted relative to the conductors  114  and  116 . As discussed in more detail below, this twisting of the conductors, in conjunction with other twists in the compensation region and a layout of the conductors in the compensation region facilitate cancellation of crosstalk between the pairs of conductors caused by a connector (e.g., connector  22  of  FIG. 1 ). 
     As illustrated by  FIG. 6 , each pair of conductors is separated from its NNP by a gap or spacing. For example, the first pair (e.g.,  114  and  116 ) are separated from the conductors  118  and  120  by a 10 mil spacing  138 . Similarly, the conductors  118  and  120  are separated from the conductors  122  and  124  by a 90 mil spacing  140 . 
     Generally, two pairs of conductors that are closer to each other will experience a higher magnitude of crosstalk than conductors that are farther away from each other. Therefore, with reference to a given conductor pair (e.g., the first pair  114  and  116 ), the magnitude of crosstalk between an NNP (e.g.,  118  and  120 ) and the given conductor pair will generally be higher than the magnitude of the crosstalk between an NNN (e.g.,  122  and  124 ) and the given conductor pair. Accordingly, the relative relationship (e.g., NNP or NNN) of the given conductor pair to another conductor pair as well as the spacings between the pairs will be a consideration for selecting compensation coupling lengths for the various conductor pairs and/or whether any of the pairs are twisted at a point in the compensation region. As discussed in detail below, it is possible to cancel both near end crosstalk and far end crosstalk using a compensation region similar to that discussed throughout this document. 
     In accordance with a non-limiting example as shown in the board structures in  FIGS. 4 and 6 , it is possible to build trace structures  112  into the PCB and cancel the connector crosstalk. Traces on the PCB are intentionally coupled together in the “compensation” region  110  specifically designed to counter-balance the connector crosstalk. At the end of the compensation region  110  there is a reduced crosstalk interface  119 , followed by the conventional fanout pattern  42  on the PCB such as shown in the plan view of  FIG. 4 . 
     The cost of this scheme is limited to the PCB real estate required to implement the compensation region trace structures in the PCB board. These trace structures can be optimized towards Near End Crosstalk (NEXT) cancellation, Far End Crosstalk (FEXT) cancellation, or a compromise between the two. Compensated CAT5-rated ribbon connectors are available at a high relative cost, though they require a non-standard pinout. In accordance with a non-limiting example, the system described herein achieves equivalent performance from a cheaper part while preserving the traditional pair assignments, if desired. It should be understood that the description is not limited to the ribbon connectors, but it can be applied to many different PCB-mounted connectors where the connector itself plus the PCB compensation region is electrically small. Also, in some embodiments, the electrical conduction can be by other than a circuit board trace, for example, by use of wire conductors, as long as the proper geometry is established. 
     A regular ribbon connector can be mounted on the circuit board and the geometry of the traces in the PCB are arranged to cancel the crosstalk in the ribbon connector. In an example, the traces are geometrically arranged by twisting some pairs at the connector to PCB interface. The twisting action may cause the flux lines in the PCB compensation region to be 180 degrees out of phase with the flux lines from the nearest neighbor pair in the connector. If the magnitudes of the inductive coupling are made the same, the inductive coupling is cancelled. The twisting action also allows the capacitive coupling to be balanced as well if the pair-to-pair spacing and the coupling distance are configured correctly. If the capacitance is balanced between each of the wires in the coupled pairs, capacitive coupling will be limited to the common mode, which is ignored by differential communication systems (this presumes good longitudinal balance—a hallmark of differential systems). Cancelling the flux and balancing the capacitance is controlled via the vertical and horizontal separations of the trace structures along with the length of the compensation region. The combination of the horizontal and vertical separation optimizes the induction and capacitance for crosstalk cancellation, creating a reduced crosstalk interface at the end of the compensation region on the PCB. No special manufacturing of a ribbon connector or other connector is required with this technique. Any off-the-shelf (OTS) components that are electrically small can be compensated for using this technique, and it is possible to have 20 dB improvement using special geometries. Example geometric configurations are discussed in more detail with reference to the figures that follow. 
       FIG. 7  is a graph showing the crosstalk in a typical CHAMP connector that the disclosed technology is attempting to ameliorate.  FIG. 7  shows the NEXT from the nearest neighbor (connector only) at  310 , and the FEXT from the nearest neighbor (connector only) at  312 . The NEXT from the next-nearest neighbor (connector only) is shown at  314  and the FEXT from the next-nearest neighbor for the connector only is shown at  316 . 
       FIG. 8  overlays the connector-only results with the results for the connector plus compensator structure when optimized for both NEXT  322  and FEXT  324  cancellation between nearest neighbors. In particular, each spacing (e.g.,  138  and  140 ) of  FIG. 6  is set to 40 mils, the length  118  is set to 4.5 inches, the trace widths are 25 mils using 2 oz copper, and the substrate thickness is 0.062 inches. The addition of the compensator drops the crosstalk by roughly 20 dB. 
     While the results of  FIG. 8  are excellent, they require a significant amount of PCB real estate. If the system does not require simultaneous NEXT and FEXT cancellation, a smaller compensation region is possible. For instance, it is possible to reduce the spacing  138  and  140  between pairs in the compensation region  110  to 10 mils.  FIG. 8A  is a graph that shows the tradeoffs that can be made between NEXT  150  and FEXT  152  cancellation verses compensation region length  118  ( FIG. 4 ). In some implementations, the structure of the compensation region (e.g., length of compensation region, spacings between conductor pairs, and location of twist points) can be selected to cancel at least a threshold amount of near end and/or far end crosstalk. For example, using graphs like that of  FIG. 8A , the structure can be selected to optimize (e.g., minimize) near end crosstalk, optimize far end crosstalk, optimize both near end and far end crosstalk, or optimize cancellation of crosstalk to the next nearest pairs of a given conductor pair. 
     When the compensation region is designed to effectively cancel the crosstalk between nearest neighbors, other couplings may become dominant. For example, the coupling to the NNN may become stronger than the cancelled NNP coupling. This is demonstrated in  FIG. 9 , where connector plus compensation region has driven the NNP NEXT  322  and NNP FEXT  324  far below the level of the NNN NEXT  332  and NNN FEXT  334  In many applications, the lowest aggregate coupling from all aggressors should be achieved, not just the nearest neighbors. Thus, in some implementations, compensation region design may be a structure that trades off some of the rejection to the nearest neighbor for purposes of achieving a given aggregate rejection over the compensation region. 
       FIG. 10A  is a top view of a compensator region  400  that can be used to cancel crosstalk to satisfy CAT5 requirements for the entire connector. The conductor pairs shown at  410 ,  420 ,  430 ,  440 ,  450 ,  460 , and  470  (“ 410 - 470 ” collectively) are conductors formed on a PCB. As indicated in the legend of  FIG. 10A , the portions of conductor pairs  410 - 470  that have a top right to bottom left diagonal fill pattern (e.g.,  410  and  450 ), referred to as the first fill pattern, represent portions of the compensation region where a tip trace is formed on a top surface of the substrate and a ring trace is formed on a bottom surface of the substrate. 
     For example, conductor pair  410  has the first fill pattern along an entire length (e.g., 3.2 inches) of the compensation region. Thus, for the entire length of the compensation region, the conductor pair marked  410  is a pair of conductors having a tip conductor on the top surface of the substrate and a ring conductor on the bottom surface of the substrate. 
     Meanwhile, conductor pair  430  has a top left to bottom right fill pattern, referred to as a second fill pattern, indicating that the conductor pair  430 , which is an NNN relative to the conductor pair  410 , visually represents a pair of conductors having a ring conductor on the top surface of the substrate and a tip conductor on the bottom surface of the substrate. As such, the crosstalk coupling between the conductor pair  410  and the conductor pair  430  is inverted (e.g., 180 degrees out of phase or in antiphase) relative to the crosstalk between these conductor pairs that is caused by the connector (“connector crosstalk”). Accordingly, the connector crosstalk between the conductor pair  410  and the conductor pair  430  is reduced and/or cancelled over the entire length of the compensation region. 
     Similar crosstalk cancellation occurs between the conductor pair  430  and the conductor pair  450  because the crosstalk coupling between the conductor pairs  430  and  450 , which are next nearest neighbors, is similarly inverted relative to the connector crosstalk between conductor pair  430  and conductor pair  450 . Connector crosstalk between other sets of next nearest neighbors can similarly be reduced and/or cancelled by using a similar layout. 
     As noted above, the distance between pairs of conductors affects the magnitude of crosstalk coupling between the pairs. Therefore, in  FIG. 10A , the magnitude of crosstalk coupling between the conductor pairs represented by conductor pairs  410  and  420  will be greater than the magnitude of the crosstalk coupling between conductor pairs represented by conductor pairs  410  and  430 . As such, the connector crosstalk between conductor pairs  410  and  420  can generally be reduced and/or cancelled by inverting the crosstalk coupling between the conductor pairs  410  and  420  (e.g., relative to the connector crosstalk coupling between the conductor pairs) over less than the entire length of the compensation region. 
     In some implementations, the spacing between the conductor pair  410  and a first portion of conductor pair  420  (e.g., the portion of conductor pair  420  formed over a first portion of the compensation region  402  that extends 1.6 inches) can be selected so that the connector crosstalk between the conductor pairs  410  and  420  can be reduced and/or cancelled based on the crosstalk coupling between the first portion of the conductor pair  420  and the conductor pair  410 . For example, as illustrated by  FIG. 10A , the first portion of the conductor pair  420  can be formed 10 mils (or another selected distance) away from the conductor pair  410  to cancel the connector crosstalk between the conductor pairs  410  and  420  over the 1.6 inch portion of the compensation region  402 . 
     A twist point (shown in more detail with reference to  FIG. 10B ) is located approximately half way along the length of the compensation region. The twist point is a location at which a pair of conductors are twisted. For example, as shown by  FIG. 10A , the conductor pair  420  are each routed to the other side of the substrate. That is, the ring trace of the conductor pair  420 , which is on top of the substrate over the portion of the compensation region  402 , is routed to the bottom of the substrate at the twist point and along a second portion of the compensation region. 
     Meanwhile, the tip conductor of the conductor pair  420  is located on the bottom of the substrate in the first portion of the compensation region, and is routed to the top of the substrate at the twist point. In some implementations, the conductors are routed through the substrate using vias (e.g., a separate via for each of the tip conductor and the trace conductor). After the twist of the conductors at the twist point, the tip conductor of conductor pair  420  remains on top over the second portion of the compensation region (e.g., the 1.6 inch portion following the twist point). 
     After the twist, the crosstalk coupling between the conductor pair  420  and the conductor pair  430  is inverted relative to the connector crosstalk between the conductor pair  420  and the conductor pair  430 . Therefore, over the second portion of the compensation region  404 , the crosstalk coupling between the conductor pair  420  and the conductor pair  430  can reduce the connector crosstalk coupling between these conductor pairs in a similar manner to that discussed above with reference to the reduction of connector crosstalk between the conductor pairs  410  and  420 . 
     A similar conductor pair pattern can be repeated as shown in  FIG. 10A  to reduce connector crosstalk between multiple pairs of nearest neighbors as well as multiple pairs of next nearest neighbors. Each pair of next nearest neighbors will have an inverted crosstalk coupling relative to the connector crosstalk coupling between that pair of next nearest neighbors. 
       FIG. 10B  is a perspective view of an example compensation region  500 . Note that for purposes of illustration and clarity,  FIG. 10B  is not drawn to scale. The compensation region  500  includes conductors  502 ,  504 ,  506 ,  508 ,  510 ,  512 ,  514 , and  516  that are formed on a substrate  518 . The substrate  518  can be, for example, a multi-layered PCB, and the conductors can either be formed on outer surfaces of the PCB (as shown) or on various layers of the PCB. 
     Conductors  502  and  504  are a single pair of conductors (also referred to as a conductor pair), as are each of conductors  506  and  508 ,  510  and  512 , and  514  and  516 . The conductor pair  506  and  508  are a nearest neighbor pair relative to the conductor pair  502  and  504 , and the conductor pair  510  and  512  are a next nearest neighbor relative to the conductor pair  502  and  504 . 
     The conductor pair  502  and  504  has a tip conductor on a top surface of the substrate  518  and a ring trace on a bottom surface of the substrate  518 . The conductor pair  510  and  512 , which is a next nearest neighbor of the conductor pair  502  and  504 , has a ring conductor on the top surface of the substrate  518  and a tip conductor on the bottom surface of the substrate  518 . As such, the conductor pair  510  and  512  is twisted relative to an orientation of the corresponding tip conductor and ring conductor of the connector interface. 
     For example, as illustrated by  FIG. 2  the tip conductors (e.g., T1, T2, T3, . . . TN) of each conductor pair is located on one side of the connector interface, while the ring conductors (e.g., R1, R2, R3, . . . RN) of each conductor pair is located on the other side of the connector interface. Meanwhile, as illustrated by  FIG. 10B , the conductor pair  510  and  512  have a different (e.g., twisted) tip and ring orientation than the conductor pair  502  and  504  and/or the tip/ring orientation of the connector interface. Therefore, the conductor pair  510  and  512  are considered to be twisted at a first end of the compensation region (e.g., relative to the conductor pair  502  and  504  and/or the tip/ring orientation of the connector interface), while the conductor pair  502  and  504  is considered to be untwisted relative to the tip/ring orientation of the connector interface. The conductor pair  506  and  508  are also twisted at the first end of the compensation region (e.g., relative to the conductor pair  502  and  504  and/or the tip/ring orientation of the connector interface), while the conductor pair  514  and  516  is not twisted at the first end of the compensation region. 
     The conductor pair  502  and  504  remain untwisted over the entire length of the compensation region, while the conductor pair  510  and  512 , which is a next nearest neighbor pair relative to the conductor pair  502  and  504 , maintains its twisted configuration over the length of the compensation region. As discussed above, the untwisted/twisted configuration between the conductor pair  502  and  504  and its next nearest neighbor pair  510  and  512  results in an antiphase crosstalk coupling (e.g., 180 degree crosstalk phase shift) between the conductor pairs  502 / 504  and  510 / 512  relative to the crosstalk between these pairs caused by the connector. The antiphase crosstalk coupling destructively interferes with the crosstalk caused by the connector, such that the crosstalk caused by the connector between these next nearest neighbor pairs is reduced and/or cancelled over the length of the compensation region. 
     As noted above, the conductor pair  506  and  508  are twisted at the first end of the compensation region. The orientation of the conductors  506  and  508  is maintained between the first end of the compensation region to the twist point  520 . At the twist point, the conductor pair  506  and  508  are again twisted (e.g., through vias) so that the orientation of the tip conductor and ring conductor are swapped. That is, at the twist point  520 , the ring conductor  506  is routed through a via from the top side of the substrate  518  to the bottom side of the substrate  518 , while the tip conductor  508  is routed through another via from the bottom side of the substrate  518  to the top side of the substrate  518 . This orientation of the ring conductor  506  and tip conductor  508  is then maintained over a second portion of the compensation region that extends from the twist point  520  to a second end  522  of the compensation region. 
     As illustrated by  FIG. 10B , when the conductor pair  506  and  508  are twisted, these conductor are also formed closer to the conductor pair  510  and  512 . That is, over the first portion of the compensation region (e.g., between the first end of the compensation region and the twist point  520 ), the spacing between the conductor pair  506 / 508  and the conductor pair  502 / 504  is smaller than the spacing between the conductor pair  510 / 512  and the conductor pair  506 / 508 . After the twist point, the conductor pair  506 / 508  is shifted over closer to the conductor pair  510 / 512 , such that the spacing between the conductor pair  510 / 512  and the conductor pair  506 / 508  is smaller than the spacing between the conductor pair  502 / 504  and the conductor pair  506 / 508 . These relative spacings between the conductor pairs results in the connector crosstalk between the conductor pair  502 / 504  and the conductor pair  506 / 508  to be reduced over the first portion of the compensation region, while the connector crosstalk between the conductor pair  506 / 508  and the conductor pair  510 / 512  to be reduced over the second portion of the compensation region. 
     The conductor pair  514 / 516  has a similar configuration as the conductor pair  506 / 508 , but the tip/ring orientation of the conductor pair  514 / 516  is inverted relative to the tip/ring orientation of the conductor pair  506 / 508 . For example, in the first portion of the compensation region, the tip conductor  514  on the top of the substrate  518 , while the tip conductor  508  is located on the bottom of the substrate, and the ring conductor  516  is located on the bottom of the substrate  518 , while the ring conductor  506  is located on the top of the substrate. In the second portion of the compensation region (e.g., from the twist points  520  and  524  to the second end  522  of the compensation region), the tip conductor  514  is located on the bottom of the substrate  518 , while the tip conductor  508  is located on the top of the substrate  518 , and the ring conductor  516  is located on the top of the substrate  518 , while the ring conductor  506  is located on the bottom of the substrate  518 . In this way, pair  506 / 508  is inverted relative to next nearest neighbor pair  514 / 516  over the entire length of the compensation region. 
       FIG. 10C  is another perspective view of the example compensation region  500 .  FIG. 10C  shows configuration details at each end of the compensation region  500 . Enlarged views  602  and  604  of the ends of the compensation region  500  show the relative orientations of, and spacings between, the conductors. For example, the enlarged view  602  shows that, at the first end of the compensation region, the conductor pair  502 / 504  is located 10 mils away from the conductor pair  506 / 508 . Meanwhile, the enlarged view  604  shows that, at the second end of the compensation region, the conductor pair  502 / 504  is located 90 mils away from the conductor pair  506 / 508 . The difference in spacing between the conductor pairs  502 / 504  and  506 / 508  is due to the shift of the conductors discussed above with reference to  FIG. 10B . The enlarged views  602  and  604  also show other spacing differences between other conductor pairs from the first end of the compensation region to the second end of the compensation region. 
     The enlarged view  604  also shows that the orientation of the conductors  506  and  508  at the second end of the compensation region is inverted relative to the orientation of these same conductors at the first end of the compensation region. This inverted orientation is due to the twist of the conductors  506  and  508  at the twist point  520  of  FIG. 10B . The orientation of conductors  514  and  516  at the second end of the compensation region are similarly inverted relative to the orientation of the conductors  514  and  516  at the first end of the compensation region. This inverted orientation is similarly a result of twisting the conductors  514  and  516  at the twist point  524  of  FIG. 10B . 
     Note that the spacings shown in  FIG. 10C  are for purposes of illustration, and other spacings can be used depending on the amount and type (e.g., near end and/or far end) crosstalk that are to be cancelled. The spacings may also vary depending on the length of the compensation region that will be used or the type of connector inducing the initial crosstalk. 
       FIG. 11  is a graph showing the performance of a CAT5 compensator with the CAT5 NEXT mask shown at  481  and the CAT5 FEXT mask shown at  482 . The FEXT from the nearest neighbor is shown at  484  and the FEXT from the next-nearest neighbor is shown at  485 . The NEXT from the nearest neighbor is shown at  486  and the NEXT from the next-nearest neighbor is shown at  487 . 
       FIG. 12  is a flow chart of an example process  1200  for cancelling connector crosstalk. The process  1200  can be initiated by receiving signals over multiple conductor pairs ( 1202 ). The signals can be received, for example, from a connector that is connected to a PCB. The received signals may be distorted by crosstalk among the conductor pairs that is caused by the configuration of the connector. 
     The conductor pairs over which the signals are received can include three or more different conductor pairs. For example, first signals can be received over a first conductor pair, while second signals and third signals can be respectively received over a second conductor pair and a third conductor pair. For example, the first conductor pair (“first pair”) can be the conductor pair  502 / 504  of  FIG. 10B , the second conductor pair can be a nearest neighbor pair (“NNP”) (e.g., conductor pair  506 / 508  of  FIG. 10B ) relative to the first conductor pair, and the third conductor pair can be a next nearest neighbor pair (“NNN”) (e.g., conductor pair  510 / 512  of  FIG. 10B ) relative to the first conductor pair. As discussed above, with reference to the first pair, the NNP is adjacent to the first pair and is located between the first pair and the NNN. 
     Crosstalk coupling between the first pair and the NNN are inverted over a given length of a compensation region ( 1204 ). In some implementations, the crosstalk coupling between the first pair and the NNN is inverted over an entire length of the compensation region. The crosstalk coupling between the first pair and the NNN can be inverted, for example, by twisting the NNN pair (e.g., relative to the first pair) at a first end of the compensation region. 
     Twisting the NNN relative to the first pair can be achieved by inverting the tip/ring orientation of the NNN relative to the tip/ring orientation of the first pair. For example, as illustrated in  FIG. 10B , the NNN (e.g., conductor pair  510 / 512 ) of the conductor pair  502 / 504  has an opposite tip/ring orientation relative to the conductor pair  502 / 504 . In particular, over the length of the compensation region, the tip  502  is on the top of the substrate  518 , while the tip  512  is on the bottom of the substrate  518 . Similarly, the ring  504  is on the bottom of the substrate  518 , while the ring  510  is on the top of the substrate  518 . 
     Twisting the NNN pair relative to the first pair changes the polarity of the crosstalk coupling between the NNN and the first pair, which results in inverted crosstalk coupling between the NNN and the first pair (e.g., relative to the connector induced crosstalk distortion). The inverted crosstalk coupling has an antiphase relative to the connector induced crosstalk distortion, and can be maintained over the entire length of the compensation region so that the connector induced crosstalk distortion can be cancelled. 
     Crosstalk coupling between the first pair and an NNP is inverted ( 1206 ). In some implementations, the crosstalk coupling between the first pair and the NNP is inverted over a first portion of the compensation region. The first portion of the compensation region can be, for example, a length of the compensation region that is less than the entire length of the compensation region. For example, in  FIG. 10B , the first portion of the compensation region can extend from the first end of the substrate  518  (e.g., front end in the perspective view) to the twist point  506 . 
     In some implementations, the crosstalk coupling between the first pair and the NNP can be inverted by twisting the NNP relative to the first pair. Twisting the NNP relative to the first pair can be achieved, for example, by inverting the tip/ring orientation of the NNP relative to the tip/ring orientation of the first pair. For example, as illustrated in  FIG. 10B , in the first portion of the compensation region, the ring  506  is on the top of the substrate  518 , while the ring  504  is on the bottom of the substrate  518 , and the tip  508  is on the bottom of the substrate  518 , while the tip  502  is on the top of the substrate. 
     Twisting the NNP relative to the first pair changes the polarity of the crosstalk coupling between the NNP and the first pair, which results in inverted crosstalk coupling between the NNP and the first pair (e.g., relative to the connector induced crosstalk distortion). The inverted crosstalk coupling may cancel the connector induced crosstalk distortion over the first portion of the compensation region. 
     Crosstalk coupling between the NNP and the NNN is inverted ( 1208 ). In some implementations, the crosstalk coupling between the NNP and the NNN is inverted over a second portion of the compensation region. The second portion of the compensation region can be, for example, a length of the compensation region that is less than the entire length of the compensation region. For example, in  FIG. 10B , the second portion of the compensation region can extend from the twist point  520  to the second end  522  of the compensation region. 
     In some implementations, the crosstalk coupling between the NNP and the NNN can be inverted by twisting the NNP relative to the NNN. Twisting the NNP relative to the NNN can be achieved, for example, by inverting the tip/ring orientation of the NNP relative to the tip/ring orientation of the NNN. For example, as illustrated in  FIG. 10B , in the second portion of the compensation region, the ring  506  is on the bottom of the substrate  518 , while the ring  510  is on the top of the substrate  518 , and the tip  508  is on the top of the substrate  518 , while the tip  512  is on the bottom of the substrate  518 . 
     Twisting the NNP relative to the NNN changes the polarity of the crosstalk coupling between the NNP and the NNN, which results in inverted crosstalk coupling between the NNP and the NNN (e.g., relative to the connector induced crosstalk distortion). The inverted crosstalk coupling has an antiphase relative to the connector induced crosstalk distortion, and therefore, may cancel the connector induced crosstalk distortion over the second portion of the compensation region. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.