Abstract:
A low cross talk compensation circuit comprising a first signal pair having a first conductor and a second conductor parallel to the first conductor, and a second signal pair having a third conductor and a fourth conductor parallel to the third conductor, wherein each conductor is attached to a corresponding input signal. A first compensation line attached to the first input signal and a second compensation line attached to the third input signal are intertwined forming a first compensation line assembly with capacitive and inductive coupling parallel to and flanked by the second and third conductors. A third compensation line attached to the fourth input signal and a fourth compensation line attached to the second input signal are intertwined forming a second compensation line assembly with capacitive and inductive coupling parallel to and adjacent to the second conductor.

Description:
RELATED APPLICATION DATA  
       [0001]    This is a continuation application of U.S. Ser. No. 10/020,281, filed Dec. 14, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a transmission medium, and more particularly, to a low cross talk electrical signal transmission medium.  
         BACKGROUND OF THE INVENTION  
         [0003]    The United States Federal Communications Commission (FCC) has adopted standards for electrical connectors used in the telecommunications industry to ensure intermateability. The most commonly utilized electrical connector is a modular plug and jack. The plug is typically terminated to a cable having a plurality of parallel conductors that are paired to form a signal loop, and the jack is commonly mounted to a panel or a printed circuit board connected to a communications network. As the modular plugs are utilized more frequently in high frequency data and communication applications, interference or cross talk that arises in adjacent and parallel contacts of the jack, and to a lesser degree in the plug, has become a problem in the industry. When an electrical signal of a given frequency is applied to a pair of conductors, an unequal portion of signal energy is transmitted to the individual conductors of an adjacent pair by each conductor of the signal pair. This transmission is primarily due to capacitive and inductive couplings between adjacent conductors being substantially higher than couplings of the other conductor of the signal pair, resulting in cross talk. Cross talk is further increased when both conductors of the signal pair are placed adjacent to and outside of opposing conductors of the other signal pair. The magnitude of the cross talk is effected by such factors as the positioning of the conductors, the distance between adjacent conductors and the dielectric material between the conductors.  
           [0004]    It has been found that cross talk coupling induced by the plug and jack interface can be reduced by shifting the placement of the conductors after they exit the jack so as to induce signals of opposite phase to those which were induced inside the plug and jack. To decrease cross talk, the conductors that form both pairs should be routed in a pattern that is opposite in polarity to the pattern that produces cross talk in the jack and plug. One such routing method is disclosed in U.S. Pat. No. 5,299,956 and U.S. Pat. No. 5,310,363 issued to Brownell et al. Brownell et al. teaches a low cross talk transmission assembly comprising an electrical connector having a first and second conductor forming a first signal pair and a third and fourth conductor forming a second signal pair. The first and second conductors are positioned adjacent and parallel to each other. The third conductor is positioned adjacent and parallel to the first conductor, and the fourth conductor is positioned adjacent and parallel to the second conductor. Because this arrangement induces cross talk from one signal pair to another signal pair when signals are applied to either one of the pairs, the third conductor is routed adjacent to and parallel to the second conductor and away from the first conductor, and the fourth conductor is routed adjacent and parallel to the first conductor and away from the second conductor. This new path configuration reduces a substantial amount of cross talk induced in the first configuration.  
           [0005]    An alternative solution to the cross talk problem is disclosed in U.S. Pat. No. 5,488,201 issued to Liu. In Liu a first end of a first conductor and a first end of a third conductor are folded into bends that are mutually inserted into each other and alternately arranged. Also, a first end of a second conductor and a first end of a fourth conductor are folded into bends that are mutually inserted into each other and alternately arranged. The alternating arrangement of the first and third conductors and the second and fourth conductors reduces the amount of cross talk between the conductors by forming a mutually corresponding capacitive arrangement for restoring electrical balance of the conductive pairs. This design, however, is intricate and requires complex configurations of the conductors to decrease the amount of cross talk. Further, the configurations are predisposed and therefore can not be manipulated to change impedance without manufacturing additional products having additional configurations.  
           [0006]    It is therefore desirable to develop a less intricate design that may be easily manipulated to change impedance for partial cancellation of cross talk induced into a signal carrying cable pair by modular jacks and plugs, or other input/output signal connectors, while maintaining proper longitudinal balance and characteristics within the connector system.  
         SUMMARY OF THE INVENTION  
         [0007]    This invention relates to a low cross talk electrical signal transmission assembly comprising a signal transmission medium having a first signal pair and a second signal pair. The first signal pair having a first conductor and a second conductor. The second signal pair having a third conductor and a fourth conductor. Each conductor is attached to a corresponding input signal. A first compensation line is attached to the first input signal, and a second compensation line is attached to the third input signal. The first compensation line and the second compensation line are intertwined to create a first compensation line assembly having capacitive and inductive coupling. A third compensation line is attached to the fourth input signal, and a fourth compensation line is attached to the second input signal. The fourth compensation line and the third compensation line are intertwined to create a second compensation line assembly with capacitive and inductive coupling. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention will now be described by way of example with reference to the accompanying figures in which:  
         [0009]    [0009]FIG. 1 is a top view of a first side of a circuit board showing an embodiment of the low cross talk compensation circuit of the present invention.  
         [0010]    [0010]FIG. 2 is a top view of a second side of the circuit board showing the low cross talk compensation circuit of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]    [0011]FIGS. 1 and 2 show a first side  20  and a second side  30  of a printed circuit board  10 , respectively. The printed circuit board  10  contains a plurality of signal input contacts  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8  and a plurality of signal output contacts  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 . The signal input contacts  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8  are electrically connected to the signal output contacts  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28  by four signal pairs  11 ,  12 ,  13 ,  14 . Each signal pair  11 ,  12 ,  13 ,  14  has a tip (T) conductor and a ring (R) conductor. A first signal pair  11  comprises a ring conductor R 1  and a tip conductor T 1 . A second signal pair  12  comprises a ring conductor R 2  and a tip conductor T 2 . A third signal pair  13  comprises a ring conductor R 3  and a tip conductor T 3 , and a fourth signal pair  14  comprises a ring conductor R 4  and a tip conductor T 4 . The conductors T 1 , R 1 , T 2 , R 2 , T 3 , R 3 , T 4 , and R 4  are represented by circuit trace lines on the printed circuit board  10 .  
         [0012]    The electrical connection of the printed circuit board  10  will now be described in greater detail. As shown in FIG. 1, on the first side  20  of the printed circuit board  10 , the signal input contact  2  is electrically connected to the signal output contact  22  by the conductor R 3 . The signal input contact  5  is electrically connected to the signal output contact  25  by the conductor T 1 . The signal input contact  6  is electrically connected to the signal output contact  26  by the conductor R 2 . The signal input contact  8  is electrically connected to the signal output contact  28  by the conductor R 4 . The conductor R 4  and the conductor R 3  are routed from their corresponding signal input contacts  8 ,  2  to their corresponding signal output contacts  28 ,  22  adjacent and parallel to each other. The conductor T 1  is routed from the signal input contacts  5  to the signal output contact  25  adjacent and parallel to the conductor R 4 . The conductor R 2  is routed from the signal input contacts  6  to the signal output contact  26  adjacent and parallel to the conductor R 3 . The conductors T 1  and R 2  thereby flank the conductors R 4  and R 3 .  
         [0013]    As shown in FIG. 1, the signal input contact  4  and the signal input contact  6  are electrically connected to conductors  34 ,  36 , respectively. The conductor  34  has a first end  61  connected to the signal input contact  4  and a second end  62  connected to a first part  51  of an insulated compensation line  44 . The first part  51  of the insulated compensation line  44  is stripped prior to connection to the second end  62 . The conductor  36  has a first end  63  connected to the signal input contact  6  and a second end  64  connected to a first part  53  of an insulated compensation line  46 . The first part  53  of the insulated compensation line  46  is stripped prior to connection to the second end  64 . The insulated compensation lines  44 ,  46  are twisted to intertwine the compensation line  44  and the compensation line  46  to form a compensation line assembly  40 . The compensation line assembly  40  is positioned substantially parallel to the printed circuit board  10  and substantially parallel to and adjacent to the conductor R 4  and the conductor R 3 . Second parts  52 ,  54  of the compensation lines  44 ,  46 , respectively, remain unattached to the printed circuit board  10 . The second parts  52 ,  54  may alternatively be tacked or otherwise attached to the circuit board  10  for example by soldering them to a non-electrical pad or via on the circuit board  10 . It should be appreciated by those skilled in the art that the first parts  51 ,  53  of the compensation lines  44 ,  46  may be attached directly to the signal input contacts  4 ,  6 , to obtain a substantially similar result. It should also be understood that the length of the compensation line assembly  40  may be varied to achieve various levels of crosstalk compensation.  
         [0014]    The signal input contact  3  and the signal input contact  5  are electrically connected to conductors  33 ,  35 , respectively. The conductor  33  has a first end  65  connected to the signal input contact  3  and a second end  66  connected to a first part  55  of an insulated compensation line  43 . The first part  55  of the insulated compensation line  43  is stripped prior to connection to the second end  66 . The conductor  35  has a first end  67  connected to the signal input contact  5  and a second end  68  connected to a first part  57  of an insulated compensation line  45 . The first part  57  of the insulated compensation line  45  is stripped prior to connection to the second end  68 . The insulated compensation lines  43 ,  43  are twisted to intertwine the compensation line  43  and the compensation line  45  to form a compensation line assembly  50 . The compensation line assembly  50  is positioned substantially parallel to the printed circuit board  10  and substantially parallel to and adjacent to the conductor T 1 . Second parts  56 ,  58  of the compensation lines  43 ,  45 , respectively, remain unattached to the printed circuit board  10 . The second parts  52 ,  54  may alternatively be tacked or otherwise attached to the circuit board  10  for example by soldering them to a non-electrical pad or via on the circuit board  10 . It should be understood by those skilled in the art that the first parts  55 ,  57  of the compensation lines  43 ,  45  may be attached directly to the signal input contacts  3 ,  5 , to obtain a substantially similar result. It should also be understood that the length of the compensation line assemble  40  may be varied to achieve various levels of crosstalk compensation.  
         [0015]    As shown in FIG. 2, on the second side  30  of the printed circuit board  10 , the signal input contact  1  is electrically connected to the signal output contact  21  by the conductor T 3 . The signal input contact  3  is electrically connected to the signal output contact  23  by means of the conductor T 2 . The signal input contact  4  is electrically connected to the signal output contact  24  by means of the conductor R 1 . The signal input contact  7  is electrically connected to the signal output contact  27  by means of the conductor T 4 . The conductor T 3  and the conductor T 4  are routed from their corresponding signal input contacts  1 ,  7  to their corresponding signal output contacts  21 ,  27  adjacent and parallel to each other. The conductor T 2  is routed from the signal input contacts  3  to the signal output contact  23  adjacent and parallel to the conductor T 3 . The conductor R 1  is routed from the signal input contact  4  to the signal output contact  24  adjacent and parallel to the conductor T 4 . The conductors T 2  and R 1  thereby flank the conductors T 3  and T 4 . The conductors T 2 , T 3 , T 4  and R 1 , located on the second side  30  of the printed circuit board  10 , are further positioned substantially parallel to the conductors R 2 , R 4 , R 3  and T 1 , respectively, located on the first side  20  of the printed circuit board  10 .  
         [0016]    As shown in FIG. 2, the signal input contact  4  and the signal input contact  6  are electrically connected to conductors  31 ,  32 , respectively. The conductor  31  has a first end  71  connected to the signal input contact  4  and a second end  72  connected to a first part  61  of an insulated compensation line  41 . The first part  61  of the insulated compensation line  41  is stripped prior to connection to the second end  72 . The conductor  32  has a first end  73  connected to the signal input contact  6  and a second end  74  connected to a first part  63  of an insulated compensation line  42 . The first part  63  of the insulated compensation line  42  is stripped prior to connection to the second end  74 . The insulated compensation lines  41 ,  42  are twisted to intertwine the compensation line  41  and the compensation line  42  to form a compensation line assembly  60 . The compensation line assembly  60  is positioned substantially parallel to the printed circuit board  10  and substantially parallel to and adjacent to the conductor T 3  and the conductor T 4 . Second parts  62 ,  64  of the compensation lines  41 ,  42 , respectively, remain unattached to the printed circuit board  10 . The second parts  52 ,  54  may alternatively be tacked or otherwise attached to the circuit board  10  for example by soldering them to a non-electrical pad or via on the circuit board  10 . The compensation line assembly  60  located on the second side  30  of the printed circuit board  10  is further positioned substantially parallel to the corresponding compensation line assembly  40  located on the first side  20  of the printed circuit board  10 . It should be appreciated by those skilled in the art that the first parts  61 ,  63  of the compensation lines  41 ,  42  may be attached directly to the signal input contacts  4 ,  6 , to achieve a substantially similar result. It should also be understood that the length of the compensation line assembly  40  may be varied to achieve various levels of crosstalk compensation.  
         [0017]    The signal input contact  3  and the signal input contact  5  are electrically connected to conductors  37 ,  38 , respectively. The conductor  37  has a first end  75  connected to the signal input contact  3  and a second end  76  connected to a first part  65  of an insulated compensation line  47 . The first part  65  of the insulated compensation line  47  is stripped prior to connection to the second end  76 . The conductor  38  has a first end  77  connected to the signal input contact  5  and a second end  78  connected to a first part  67  of an insulated compensation line  48 . The first part  67  of the insulated compensation line  48  is stripped prior to connection to the second end  78 . The insulated compensation lines  47 ,  48  are twisted to intertwine the compensation line  47  and the compensation line  48  to form a compensation line assembly  70 . The compensation line assembly  70  is positioned substantially parallel to the printed circuit board  10  and substantially parallel to and adjacent to the conductor R 1 . Second parts  66 ,  68  of the compensation lines  47 ,  48 , respectively, remain unattached to the printed circuit board  10 . The compensation line assembly  70  located on the second side  30  of the printed circuit board  10  is further positioned substantially parallel to the corresponding compensation line assemblies  50  located on the first side  20  of the printed circuit board  10 . It should be understood by those skilled in the art that the first parts  65 ,  67  of the compensation lines  47 ,  48  may be attached directly to the signal input contacts  3 ,  5 , to achieve a substantially similar result. It should also be understood that the length of the compensation line assembly  40  may be varied to achieve various levels of crosstalk compensation.  
         [0018]    Advantageously, the impedance of the compensation assemblies  40 ,  50 ,  60 ,  70  may be varied by increasing or decreasing the number of twists in the pairs of compensation lines  44  and  46 ,  43  and  45 ,  41  and  42 ,  47  and  48 . While the present invention has been described in connection with the illustrated embodiments, it will be appreciated and understood that modifications may be made without departing from the true spirit and scope of the invention. For example, it should be appreciated by one skilled in the art that the number and location of the signal pairs, the number and location of the conductors, as well as the number and location of the compensation assemblies, may be increased or decreased to obtain substantially similar results.