Abstract:
Patch cords suitable for Category 6 data transmission applications terminated at the two ends by first and second modular plugs that differ from each other in a complementary manner such that relative positioning of wire pairs is maintained at both ends of the patch cord, and without any crossing of any wire of one pair over a wire of another pair within either modular plug.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 09/866,081, now U.S. Pat. No. 6,517,377 filed May 25, 2001, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/207,056, filed May 25, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to electrical connector and cable assemblies and, more particularly, to patch cord assemblies comprising multi-conductor cable terminated by modular plugs at each end, as well as to the modular plugs themselves. 
     Modular plugs are well known and are extensively used in data communication networks, particularly local area networks. A typical patch cord comprises a length of cable including four twisted pair, insulated, multi-colored wires (eight in total) arranged in a bundle within a cable jacket. Category 5 connectors operate at frequencies of order 100 MHz, while maintaining 43 dB isolation between pairs. Category 6 products operate at frequencies of order 200 MHz, while maintaining 46 dB isolation between pairs. 
     Maintaining the performance at high frequencies of such networks employing twisted pair conductors and relatively simple modular plugs is difficult. Crosstalk resulting from capacitive and inductive coupling between the various signal pairs is problematic. In addition, minimizing discontinuities in characteristic impedance at the modular plug terminations is important in order to minimize reflected signals which manifest as wire pair return loss. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention, suitable for category 6 data transmission applications, achieve reduced capacitive coupling between wire pairs within modular plugs. In addition, wire pair return loss is improved, and is more uniform from one wire pair to the next. 
     In an exemplary embodiment of the invention, a patch cord includes a length of multi-conductor cable having first and second ends, and including eight wires organized as four pairs. First and second modular plugs terminate the first and second cable ends respectively. The first and second modular plugs differ from each other in a complementary manner such that relative positioning of the pairs is maintained at both ends of the patch cord. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a patch cord embodying the invention, including two modular plugs designated “A” and “B” differing from each other in a complementary manner; 
     FIG. 2 is a transverse cross sectional view of one of the complementary modular plugs, Plug “A,” taken on line  2 — 2  of FIG. 1; 
     FIG. 3 is a transverse cross sectional view of the other of the complementary modular plugs, Plug “B,” taken on line  3 — 3  of FIG. 1; 
     FIG. 4 is a partially exploded three-dimensional view generally from the rear of Plug “A” of FIGS. 1 and 2; 
     FIG. 5 is a similar partially exploded three-dimensional view generally from the rear of Plug “B” of FIGS. 1 and 3; 
     FIG. 6 is a highly schematic representation of the arrangement of wires within Plug “A” of FIGS. 1,  2  and  4 ; 
     FIG. 7 is a complementary highly schematic representation of the arrangement of wires within Plug “B” of FIGS. 1,  3  and  5 ; 
     FIGS. 8 and 9, which may be contrasted with FIGS. 6 and 7, respectively, represent an arrangement of wires within a pair of prior art modular plugs terminating the ends of a prior art patch cable; and 
     FIGS. 10 and 11, which likewise may be contrasted with FIGS. 6 and 7, respectively, represent an arrangement of wires within another form of prior art modular plugs terminating the ends of another prior art patch cable. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIGS. 1,  2  and  3 , a Category 6 patch cord  20  embodying the invention includes a length of multi-conductor cable  22  having first and second ends  24  and  26 . For convenience of illustration, the ends  24  and  26  are schematically depicted in cross section, with dash lines representing continuation into respective terminating modular plugs  30  and  32 . As is described in detail hereinbelow, the modular plugs  30  and  32  differ from each other in a complementary manner, and for purposes of description are also referred to herein as Plug “A” and Plug “B,” respectively. 
     As is well known, the cable  22  is a twisted pair cable wherein selected pairs of wires  34  are twisted together, the wires  34  having first and second ends  36  and  38  corresponding to the first and second ends  24  and  26  of the cable  22 . The cable  22  has four twisted pairs of insulated wires (eight wires in total) organized as four twisted Pairs P 1 , P 2 , P 3  and P 4  within a cable jacket  39 . A conventional pairing arrangement of wires for termination by the modular plugs  30  and  32  is  1 - 2  (Pair P 2  in the exemplary embodiment);  3 - 6  (Pair P 3  in the exemplary embodiment);  4 - 5  (Pair P 1  in the exemplary embodiment); and  7 - 8  (Pair P 4  in the exemplary embodiment). 
     The modular plugs  30  and  32  (Plug “A” and Plug “B”) are of similar construction, but differ from each other in a complementary manner, in particular in the arrangement of passages receiving the wire ends  36  and  38 . 
     Thus, referring in addition to FIGS. 4 and 5, as well as to FIGS. 1-3, the modular plugs  30  and  32  include respective dielectric housings  40  and  42 , of transparent plastic. The plugs  30  and  32  have respective closed forward ends  44  and  46 , and respective cable-receiving rearward ends  48  and  50 . In addition, the dielectric housings  40  and  42  have respective terminal sides  52  and  54 , as well as respective tab sides  56  and  58  from which conventional retention tabs  60  and  62 , respectively, extend for retaining the respective plugs  30  and  32  in mating sockets (not shown) comprising, for example, part of a patch panel (not shown). 
     Opening on to the terminal side  52  of the dielectric housing  40  of Plug “A” are eight parallel and evenly laterally spaced contact-receiving slots  64 , defining, in sequential order, position numbers  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7  and  8 . Likewise, opening on to the terminal side  54  of the dielectric housing  42  of Plug “B” are a set of eight contact-receiving slots  66  likewise defining, in sequential order, position numbers  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 , and  8 . 
     Conventionally, position numbers  1  and  2  correspond to one pair, such as Pair P 2  or Pair P 4 . Position numbers  7  and  8  correspond to another pair, such as Pair P 4  or Pair P 2 . Position numbers  4  and  5  correspond to yet another pair, such as Pair P 1 . Position numbers  3  and  6  correspond to still another pair, such as Pair P 3 . 
     Within the dielectric housing  40  comprising Plug “A” is a set  72  of eight wire-receiving passages in communication with respective ones of the contact-receiving slots  64 . Likewise, within the dielectric housing  42  comprising Plug “B” is a set  74  of eight wire-receiving passages in communication with respective ones of the contact-receiving slots  66 . 
     As best seen in FIGS. 2 and 3, the first and second ends  36  and  38  of the cable wires  34  are received in respective ones of the wire-receiving passages of the sets  72  and  74  within the respective modular plugs  30  and  32 . The wires  34  comprise conductors  76  surrounded by insulation  78 . 
     The modular plug  30  (Plug “A”) includes a set  80  of eight contacts received within the contact-receiving slots  64 , facing and opening on to the terminal side  52 . The contacts of the set  80  electrically engage respective ones of the cable wire ends  36  in a conventional insulation-displacement contact (IDC) manner upon assembly of the patch cord  20 . Likewise, the modular plug  32  (Plug “B”) includes a set  82  of eight contacts received within the contact-receiving slots  66  facing and opening on to the terminal side  54 . The contacts of the set  82  electrically engage respective ones of the cable wire ends  38  in a conventional insulation-displacement contact (IDC) manner. 
     The manner in which the modular plugs  30  and  32  differ from each other in a complementary manner is shown in FIGS. 2 and 3 (as well as in FIGS.  4  and  5 ). In particular, the arrangements of the sets  72  and  74  of wire-receiving passages differ. With particular reference to FIG. 3, within the modular plug  32  (Plug “B”), two of the wire-receiving passages  74  in communication with the slots  66  defining position numbers  3  and  6  are offset from the remaining wire-receiving passages  74  in a direction relatively farther from the terminal side  54  of the dielectric housing  42 . In a complementary manner, and with particular reference to FIG. 2, within the modular plug  30  (Plug “A”), two of the wire-receiving passages  72  in communication with the slots  64  defining position numbers  3  and  6  are offset from the remaining wire-receiving passages  72  in a direction relatively closer to the terminal side  52  of the dielectric housing  40 . 
     More particularly, in the exemplary embodiment, within each of the modular plugs  30  and  32  (Plug “A” and Plug “B”) six of the wire-receiving passages  72  (Plug “A”) and  74  (Plug “B”) defining position numbers  1 ,  2 ,  4 ,  5 ,  7  and  8  are disposed in a first plane  84 , and two of the wire-receiving passages  72  (Plug “A”) and  74  (Plug “B”) are disposed in a second plane  86  offset from the first plane  84 . The two planes  84  and  86  are spaced one above the other. One of the two planes  84  and  86  is relatively closer to the terminal side  52  or  54  of the dielectric housing  40  or  42 , and the other of the two planes  84  and  86  is relatively farther from the terminal side  52  or  54  of the dielectric housing  40  or  42 . 
     Thus, within the modular plug  32  of FIG. 3 (Plug “B”), the first plane  84  is relatively closer to the terminal side  54  of the dielectric housing  42  and the second plane  86  is relatively farther from the terminal side  54  of the dielectric housing  42 . Within the modular plug  30  of FIG. 2 (Plug “A”), the second plane  86  is relatively closer to the terminal side  52  of the dielectric housing  40 , and the first plane  84  is relatively farther from the terminal side  52  of the dielectric housing  40 . 
     As may be seen in FIGS. 4 and 5, the plugs  30  and  32  have respective wire-guiding inserts  90  and  92  having apertures corresponding to the arrangement of the respective sets of wire-receiving passages  72  and  74 . In the exploded views of FIGS. 4 and 5 the inserts  90  and  92  are positioned adjacent the cable-receiving rearward ends  48  and  50 . However, upon assembly of the patch cord  20 , the inserts  90  and  92  are positioned near the respective forward ends  44  and  46  of the plugs  30  and  32 , leaving spaces near the rearward ends  48  and  50  for a cable-retaining filler (not shown) or a strain-relief insert (not shown). 
     FIGS. 6 and 7 are respective highly schematic depictions, viewed generally from the forward ends  44  and  46 , representing the manner in which the eight individual wires of the multi-conductor cable arranged in Pairs P 1 , P 2 , P 3  and P 4  are routed within the plugs  30  and  32  from the points where the cable jacket  39  is stripped away to the corresponding wire-receiving passages  72  of the modular plug  30  (Plug “A”) and to the corresponding wire-receiving passages  74  of the modular plug  32  (Plug “B”). 
     From FIGS. 6 and 7, it may be seen that the relative positioning of the wire pairs P 1 , P 2 , P 3  and P 4  is maintained at both ends of the patch cord  20 . In particular, the orientation of the wire-receiving passages  72  and  74  is the same relative to the wire positions at the two ends  24  and  26  of the cable  22 . Moreover, no wire of any one pair is required to cross over any wire of another pair within either one of the modular plugs  30  and  32 . The offset of the wire-receiving passages  72  (Plug “A”) and  74  (Plug “B”) allows the conductors of each of the Pairs P 1 , P 2 , P 3  and P 4  to remain paired as much as possible to maintain characteristic impedance so as to improve return loss characteristics. In addition the wires are separated as pairs from other pairs as much as possible to reduce crosstalk couplings. 
     The following TABLE captioned “Category 6 Plug L and C Values” compares de-embedded near-end crosstalk of Plugs A and B for each of the six possible pair combinations. The table is based on measured results from thirty samples of each part; thus, calculated values for the average and standard deviation are given. Magnitude and phase are compared separately. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 
               
               
                   
               
               
                 Category 6 plug L and C values 
               
               
                 Crosstalk Comparison of “Plug A” and “Plug B” for each pair combination 
               
               
                 Data Based on 30 Samples 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Pair Combination: 
               
             
          
           
               
                   
                 P1-P2 
                 P1-P3 
                 P1-P4 
                 P2-P3 
                 P2-P4 
                 P3-P4 
               
             
          
           
               
                   
                 (Position numbers:) 
               
             
          
           
               
                   
                 45-12 
                 45-36 
                 45-78 
                 12-36 
                 12-78 
                 36-78 
               
             
          
           
               
                 Plug A 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Mag, dB: 
                 Average 
                 −58.93 
                 −37.43 
                 −60.07 
                 −48.32 
                 −80.58 
                 −46.24 
               
               
                   
                 Std. Dev. 
                 4.75 
                 0.48 
                 3.92 
                 2.49 
                 6.91 
                 1.71 
               
               
                 Plug B 
               
               
                 Mag, dB: 
                 Average 
                 −64.16 
                 −37.57 
                 60.79 
                 −46.33 
                 −79.65 
                 −47.79 
               
               
                   
                 Std. Dev. 
                 5.73 
                 0.47 
                 6.33 
                 1.28 
                 6.49 
                 2.10 
               
               
                 Plug A: 
               
               
                 Phase: 
                 Average 
                 91.24 
                 −89.58 
                 89.17 
                 −89.09 
                 −56.08 
                 −89.66 
               
               
                   
                 Std. Dev. 
                 2.14 
                 0.13 
                 3.23 
                 1.02 
                 52.43 
                 1.10 
               
               
                 Plug B: 
               
               
                 Phase: 
                 Average 
                 91.61 
                 −89.34 
                 94.50 
                 −88.83 
                 −55.12 
                 −89.33 
               
               
                   
                 Std. Dev. 
                 3.28 
                 0.13 
                 2.15 
                 0.72 
                 69.87 
                 1.06 
               
               
                   
               
             
          
         
       
     
     FIGS. 8 and 9 may be contrasted to FIGS. 6 and 7, and depict in generally the same manner the routing of wires within the modular plugs  100  and  102  of a conventional prior art patch cord. Although the plug  100  of FIG. 8 is oriented with its tab  104  up, and the plug of FIG. 9 is oriented with its tab  100  down, the plugs  100  and  102  themselves are identical. 
     In the plug  100  of FIG. 8, the wires of Pair P 1  must extend between the wires of Pairs P 2  and P 4  to reach the wire-receiving passages corresponding to terminal positions  4  and  5 . At the other end, within the plug  102  of FIG. 9, the wires of Pair P 3  must extend between the wires of Pairs P 2  and P 4  to reach the wire-receiving passages corresponding to positions  3  and  6 . 
     As a result, in the prior art arrangement depicted in FIGS. 8 and 9, the two ends of the cable have different characteristic couplings between Pairs  1 - 2 ,  1 - 4  and  2 - 3 ,  3 - 4 . In addition, having all wires parallel in the same plane in the fixed portion of the plug (wire guide and wire-receiving passages) results in greater than desired coupling magnitude, particularly for a category  6  application requirement. 
     FIGS. 10 and 11 depict modular plugs  110  and  112  of another prior art patch cord. Within the modular plugs  110  and  112 , the wire-receiving passages are arranged in a staggered pattern. Although the plug  110  at end “A” in FIG. 10 is oriented with its tab  114  up and the plug  112  at end “B” of FIG. 11 is oriented with its tab  116  down, the plugs  110  and  112  of FIGS. 10 and 11 are themselves essentially identical. 
     In FIG. 10, at end “A” within plug  110  the wires of Pair P 1  extend between the wires of Pairs P 2  and P 4 . Moreover, one wire of Pair P 1  must cross over a wire of Pair P 3  in order to reach the corresponding wire-receiving passage. 
     As shown in FIG. 11, at end “B”, the wires of Pair P 3  extend between Pairs P 2  and P 4 , and one wire of Pair P 3  crosses over Pair P 1  to reach the corresponding wire-receiving passage. 
     While a specific embodiment of the invention has been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.