Abstract:
An electrical cable includes a cable jacket defining a central longitudinal axis and a plurality of twisted pairs of insulated conductors oriented longitudinally within the cable jacket. Each of the twisted pairs of insulated conductors has a width. A filler element is disposed in the cable jacket and is located adjacent to at least one of the twisted pairs of insulated conductors. The filler element defines a width that is substantially larger than the width of each the twisted pairs of insulated conductors. The filler element has a central axis laterally offset from the central longitudinal axis of the cable jacket. The filler element reduces alien crosstalk from an adjacent cable.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an electrical cable that reduces alien crosstalk between cables. More specifically, a filler element disposed in the electrical cable reduces alien crosstalk between adjacent cables.  
       BACKGROUND OF THE INVENTION  
       [0002]     Interference between electrical cables bundled together in a cabling system decreases the efficiency of data transmission by the cabling system. Alien near-end crosstalk (ANEXT) and alien far-end crosstalk (AFEXT) noise is caused by the electrical unbalance between the twisted pairs of insulated conductors of adjacent cables. ANEXT and AFEXT are transmission noises that can increase the signal to noise ratio (SNR) and bit error rate (BER) in a cable transmission system, such as for a local area network.  
         [0003]     Specifically, ANEXT and AFEXT occur when some of the signal current in a twisted pair of one cable couples with another twisted pair of another cable external to the signal path and along the path of a circuit between the two pairs. That noise corrupts the signal in the twisted pair external to the original signal path. When the circuit between the noise emitting and receiving twisted pairs egresses one cable boundary and crosses another cable boundary, the noise becomes alien crosstalk.  
       SUMMARY OF THE INVENTION  
       [0004]     According to the present invention, there is provided an electrical cable that includes a cable jacket defining a central longitudinal axis and a plurality of twisted pairs of insulated conductors oriented longitudinally within the cable jacket. Each of the twisted pairs of insulated conductors has a width. A filler element is disposed in the cable jacket and is located adjacent to at least one of the twisted pairs of insulated conductors. The filler element defines a width that is substantially larger than the width of each the twisted pairs of insulated conductors. The filler element has a central axis laterally offset from the central longitudinal axis of the cable jacket. The filler element reduces alien crosstalk from an adjacent cable.  
         [0005]     The present invention also provides an electrical cable that includes a cable jacket that defines a central longitudinal axis and a substantially non-circular outer perimeter. A plurality of twisted pairs of insulated conductors are oriented longitudinally within the cable jacket. Each of the twisted pairs of insulated conductors has a width. A filler element is disposed in the cable jacket and located adjacent to at least one of the twisted pairs of insulated conductors. The filler element has a central axis laterally offset from the central longitudinal axis of the cable jacket. The filler element is substantially circular in section transverse to the central axis and defines a diameter that is substantially larger than the width of each the twisted pairs of insulated conductors. The filler element reduces alien crosstalk from an adjacent cable.  
         [0006]     Advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0008]      FIG. 1  is a drawing of a perspective view of an electrical cable according to a first embodiment of the present invention;  
         [0009]      FIG. 2  is a drawing of an elevational view in section of the electrical cable illustrated in  FIG. 1 , showing a plurality of twisted pairs of insulated conductors and a filler element enclosed by a cable jacket;  
         [0010]      FIG. 3  is a drawing of an elevational view in section of an electrical cable according to a second embodiment of the present invention; and  
         [0011]      FIG. 4  is a drawing of an elevational view in section of an electrical cable according to a third embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     Referring to  FIGS. 1 and 2 , an electrical cable  100  according to a first embodiment of the present invention includes a plurality of twisted pairs of insulated conductors  102  and a filler element  104  for reducing alien crosstalk between adjacent cables. More specifically, the filler element  104  increases the cable diameter along one axis  106  of the cable  100  cross-section, effectively increasing the net distance between the pairs of insulated conductors  102  in the cable  100  from twisted pairs of insulated conductors of an adjacent cable (not shown).  
         [0013]     As seen in  FIG. 2 , the electrical cable  100  has a cable jacket  202  that encloses the filler element  104  and the plurality of twisted pairs of insulated conductors  102  in an inner area  204  defined by the inner perimeter  206  of the cable jacket  202 . Although the plurality of twisted pairs of insulated conductors  102  preferably include four pairs of insulated conductors  208 ,  210 ,  212 , and  214 , the electrical cable  100  can include any number of twisted pairs of insulated conductors. The cable jacket  202  can be formed of a dielectric material, such as PVC, TA-910, or polyolefin low smoke zero halogen.  
         [0014]     Each twisted pair of insulated conductors  208 ,  210 ,  212 , and  214  defines a width  216  and is supported in a first region  218  of the cablejacket  202 . The cable jacket  202  defines a generally central longitudinal axis  220 . The cable  100  can be twisted about the central longitudinal axis  220 , as seen in  FIG. 1 . A second region  222  supports the filler element  104 . The filler element  104  has a generally cylindrical rod shape, with a substantially circular cross-sectional shape, and defines a width or diameter  224  and has a central axis  226 . The first and second regions  218  and  222  are generally continuous.  
         [0015]     The width  228  of the first region  218  is substantially larger than the width  230  of the second region  222 , thereby creating an uneven or lopsided outer perimeter  232  of the cable jacket  202 , such that the shape of the electrical connector  100  in section transverse to the longitudinal axis  220  is substantially non-circular, as seen in  FIG. 2 . Preferably, the width  228  of the first region  218  is about twice the width  230  of the second region  222 . However, the width  228  of the first region  218  can be any size with respect to width  230  of the second region  222 , such as the same as or slightly larger than the width  230  of the second region  222 , between the pairs  102  of the cable  100  and the pairs of an adjacent cable, thereby reducing alien crosstalk between the cables.  
         [0016]     As seen in  FIGS. 1-4 , the cable  100  is preferably twisted about its central longitudinal axis  230  so that the raised areas  106  rotate substantially 360° around the cable  100 .  FIGS. 2-4  show the orientations of the raised areas  106  along the length of the cable  100  after the cable  100  has been twisted. By twisting the cable  100 , the raised areas  106  of the cable jacket  104  rotate all the way around the cable  100  and therefore the spacing between the pairs of adjacent cables is maintained on all sides of the cables.  
         [0017]     The raised areas  106  and the cable jacket  104  are preferably formed as a unitary one-piece member. Alternatively, the raised areas  106  can be formed separately from the cable jacket  104  and attached to the cable jacket  104 . The cable jacket  104  and the raised areas  106  can be formed of a dielectric material, such as PVC or polyolefin low smoke zero halogen.  
         [0018]     Although it is preferable to include more than one raised area  106  with the cable jacket  104 , a single raised area or more than two raised areas can be employed. Also, the thickness of the entire cable jacket  104  can be increased to reduce alien crosstalk.  
         [0019]     Referring to  FIG. 5 , an electrical cable  500  in accordance with a second embodiment of the present invention, is the same as the cable  100  of the first embodiment, except that the dielectric separator  502  of the cable  500  includes three separate tapes  506 ,  508  and  510 . The three tapes  506 ,  508 , and  510  separate the inner area  504  of the cable  500  into four quadrants with each quadrant supporting one of the twisted pairs of insulated conductors  208 ,  210 ,  212  and  214 . More specifically, the first tape  506  is substantially straight and divides the inner area  204  into first and second hemispheres  512  and  514  with two of the twisted pairs of insulated conductors  208  and  214  being disposed in the first hemisphere  512  and the remaining two pairs  210  and  212  being disposed in the second hemisphere  514 . The second and third tapes  508  and  510  are each disposed in the first and second hemispheres  512  and  514 , respectively. The second tape  508  divides twisted pairs  208  and  214  and the third tape  510  divides twisted pairs  210  and  212 . The three separate tapes  506 ,  508  and  510  are preferably formed of a polymer material. embodiment, except a second filler element  304  is disposed in a third region  336  of the cable jacket  302 . The third region  336  is substantially the same size as the second region  222  and the second filler element  304  is substantially the same size as the first filler element  104 . The outer perimeter  332  of the cable jacket  302  is uneven with a non-circular cross-section; however, unlike the first embodiment, the outer perimeter is substantially symmetrical about a vertical axis of  FIG. 3 . Like the filler element  104 , the second filler element  304  has a central axis  326  that is offset from the central longitudinal axis  320  of the cable  300 . The second filler element  304  further increases the distance between neighboring cables along axis  106  to reduce alien crosstalk caused by an adjacent cable.  
         [0020]     Referring to  FIG. 4 , an electrical cable  400  in accordance with a fourth embodiment of the present invention includes a filler element  404  and the plurality of twisted pairs of insulated conductors  202  supported in a cable jacket  405 . The filler element  404  is similar to the filler element  104 , except that it is larger, preferably about twice the width  216  of each twisted pair of insulated conductors  208 ,  210 ,  212  and  214 . Unlike the cables  100  and  300  of the first and second embodiments, the cable jacket  405  of the cable  400  includes a single region  418  for supporting the filler element  404  and the plurality of twisted pairs  202 . The filler element  404  also includes a conductive core  408 .  
         [0021]     Like the cables  100  and  300  of the first and second embodiments, the cross-sectional shape of the cable  400  is non-circular, such as an elliptical shape. The non-circular shape of the cable  400  defines an even outer perimeter  432  of the cable jacket  406 . The non-circular cross-sectional shape of the cable jacket  406  increases the diameter of the cable  400  along one axis  406  of the cable  400 . A central axis  426  of the filler element  404  is offset from the central longitudinal axis  420  of the cable  400 . Since the width or diameter  424  of the filler element  404  is about twice the width  216  of each twisted pair of insulated conductors  208 ,  210 ,  212 , and  214 , the pairs  208 ,  210 ,  212 , and  214  are prevented from encircling the filler element  404 , so that the filler element  404  remains offset from the central longitudinal axis  420  of the cable  400 . Similar to the first and second embodiments, by fashioning the cable  400  in this manner, the distance between twisted pairs of insulated conductors of adjacent cables is increased, thereby reducing alien crosstalk.  
         [0022]     While particular embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims. For example, any number of filler elements can be employed with the cable including one, two, or more than two filler elements.