Abstract:
The invention discloses an electrical signal cable assembly ( 10, 110, 210, 710 ) with a plurality of subcable assemblies ( 20, 120, 220, 320, 620, 720 ) stacked on each other. Each subcable assembly ( 20, 120, 220, 320, 630, 720 ) includes a plurality of coplanar electrical signal conductors ( 30, 130, 230, 330, 730 ) encased within an insulator ( 40   a,    40   b ) and which are separated from each other by a first pitch distance (a), whereby the first pitch distance (a) is between 0.1 mm and 10 mm. The characteristic impedance of the electrical signal cable assembly ( 10, 110, 210, 710 ) is in the range of 50 Ω to 200 Ω. I the preferred embodiment of the electrical signal cable assembly ( 10, 110, 210, 710 ) the insulator ( 40   a,    340   a,    640   a,    740   a,    40   b,    640   b,    740   b ) comprises an upper insulator ( 40   a,    340   a,    640   a,    740   a ) laminated to a lower insulator ( 40   b,    340   b,    640   b,    740   b ) and is made from expanded polytetrafluoroethylene.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation in part of U.S. application Ser. No. 10/891,639 (pending) which is a continuation of U.S. patent application Ser. No. 09/570,773, (abandoned) which is a Continuation in part of application Ser. No. 09/148,653 filed Sep. 4, 1998. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to an electrical signal line cable assembly.  
       PRIOR ART  
       [0003]     Electrical signal lines are known, for example, from European Patent Application EP-A-0 735 544 (Cartier et al.) assigned to Hewlett-Packard Company. This patent application describes an ultrasound system with a transducer cable for providing an electrical connection between a transducer and a display processor. The third embodiment of the transducer cable in this application uses three layers of extruded ribbon assemblies separated from each other by shield conductors comprising thin strips of bare copper. The stack of ribbon assemblies and shield conductors are extruded with a ribbon jacket to form a desired length of the transducer cable.  
         [0004]     U.S. Pat. No. 4,847,443 (Basconi) assigned to the Amphenol Corporation teaches another example of an electrical signal line cable formed from a plurality of generally flat electrical signal line segments stacked together in an interlocking relationship. Each electrical signal line segment of this prior art cable contains at least one signal conductor surrounded on either side by ground conductors. The plurality of ground conductors effectively form a ground plane which inhibit the cross-talk between the adjacent signal conductors. The insulating materials in which the conductors are disposed is extruded over the individual signal conductors.  
         [0005]     European Patent EP-B-0 605 600 (Springer et al.) assigned to the Minnesota Mining and Manufacturing Company teaches a ribbon cable and a lamination method for manufacturing the same. The ribbon cable manufactured comprises a plurality of evenly spaced flexible conductors surrounded by an insulator which is a microporous polypropylene.  
         [0006]     U.S. Pat. No. 4,847,443 (Crawley et al.) assigned to W.L.Gore &amp; Associates teaches a multi-conductor flat ribbon cable having a plurality of electrical conductors disposed within an insulator consisting of expanded polytetrafluoroethylene (ePTFE).  
         [0007]     PCT patent application WO-A-91/09406 (Ritchie et al) teaches an electrical wiring composed of elongated electrically conductive metal foil strips laminated between opposing layers of insulating films by means of adhesive securing the foil strips between the laminating films.  
         [0008]     German patent application DE-A-24 24 442 assigned to Siemens teaches a cable assembly which comprises a plurality of flat cables laminated between insulating films.  
         [0009]     PCT patent application WO-A-80/00389 (Clarke) assigned to Square D company of Palatine, Ill., teaches an input/output data cable for use with programmable controllers. The cable has a ground conductor, a logic level voltage conductor and a number of signal tracks. The conductors are disposed on two or three layers of flexible plastics material in specified ways to give high immunity to interference and low inductive losses. The layers are glued together to form a laminate structure.  
         [0010]     W. L. Gore &amp; Associates, Inc., Newark, Del. sell a round cable under the part number 02-07605 which comprises 132 miniature co-axial cables enclosed within a braided shield of tin-plated copper and a jacket tube of PVC.  
         [0011]     There remains a need in the art to develop an electrical signal cable assembly having a plurality of ribbon cables which is light in weight, offers adequate performance characteristics and reduces the complexity of termination.  
       SUMMARY OF THE INVENTION  
       [0012]     It is therefore an object of this invention to develop an improved signal cable assembly.  
         [0013]     It is furthermore an object of the invention to develop a signal cable assembly having a plurality of ribbon cables which have a high impedance and low capacitance  
         [0014]     It is furthermore an object of this invention to simplify the termination of a signal cable assembly.  
         [0015]     It is furthermore an object of this invention to develop a signal cable assembly having a plurality of ribbon cables which is light in weight compared to a comparable assembly of miniature coaxial cables.  
         [0016]     These and other objects of the invention are achieved by providing an electrical signal cable assembly comprising at least one ribbon cable arranged in at least one first concentric array around a cylindrical spacer. A separating concentric element disposed about the first concentric array and at least one further ribbon cable is arranged in at least one further concentric array about the separating concentric element.  
         [0017]     The separating concentric element can be either formed from a dielectric spacer, a conducting plane or a combination of the two. Its role is many-fold. It is used to improve the signal isolation and reduce cross-talk between the concentric arrays. The dielectric spacer is used to increase the impedance and thus reduce the capacitance. The conducting plane is used as a ground plane to further reduce the cross-talk between the ribbon cables in different concentric arrays.  
         [0018]     One embodiment of the invention uses a ribbon cable as a separating concentric element in which all of the electrical conductors within the ribbon cable are connected to AC ground potential. This construction has the advantage compared to the use of a metal ground plane in that during flexing of the cable the generation of tribostatic charge between the separating concentric element and the ribbon cable is eliminated. As is known, tribostatic charges are generated when conducting metal material rubs against a dielectric insulator. The tribostatic charges generate signal noise within the electrical signal cable assembly which degrade the quality of the signals carried on the assembly. Since the use of a ribbon cable as a separating concentric element ensures that the dielectric insulating material of the separate concentric element rubs against the same or similar dielectric insulating material of the ribbon cable in one of the concentric arrays, there are no tribostatic charges generated in this embodiment of the cable and consequently the signal carrying capability of the electrical signal cable assembly is enhanced.  
         [0019]     In one embodiment of the invention, at least some of the ribbon cables of the concentric arrays are made up of a plurality of electrical conductors, some of which are connectable to AC ground potential and others to signals. The connection of at least some of the electrical conductors to AC ground potential within the same ribbon cable as those signal-carrying conductors is that the AC ground-carrying conductors shield the signal-carrying conductors from each other and thus reduce the cross-talk between the signal-carrying conductors within the same ribbon cable. The term AC ground means that the AC ground carrying conductors do not carry an alternating signal but rather an invariable voltage level which may or may not be at zero volts.  
         [0020]     In some of the concentric arrays, two or more ribbon cables are placed adjacent to each other. This improves the flexibility of the electrical signal cable assembly since narrower ribbon cables can be used which move within the same concentric array relative to each other and thus contribute to the flexibility of the cable.  
         [0021]     The ribbon cables in the electrical signal cable assembly are served about the cylindrical spacer and in the first as well as in the subsequent further concentric arrays. It is also conceivable to braid the cables or wrap them in other manners. The ribbon cables can be served in the same direction in all of the concentric arrays or they can be opposedly served in adjacent concentric arrays.  
         [0022]     It is advantageous to serve the separating concentric element in an opposed manner to the ribbon cables in the adjacent concentric arrays since this will enhance the ability of the separating concentric element to maintain the stability of the ribbon cables.  
         [0023]     In the electrical signal cable assembly an outer shield is preferentially disposed about the further concentric array to act as an electromagnetic shield for shielding the electrical conductors within the electrical signal cable assembly from extraneous signals. Furthermore an outer binder can be disposed between the further concentric array and the outer shield to hold the ribbon cables within the electrical signal cable assembly in place.  
         [0024]     A jacket is disposed about the outside of electrical signal cable assembly to protect the electrical signal cable assembly from mechanical damage.  
         [0025]     The electrical signal cable assembly can have more than two concentric arrays. Each of the concentric arrays is separated from each other by further concentric separating elements.  
         [0026]     The electrical signal cable assembly can incorporate within the first concentric array a strain relief or a strength member to improve the longitudinal strength of the assembly. Furthermore, an insulated wire signal or signal coaxial cables can be incorporated within cylindrical spacer which can carry, for example, power or further signals along the assembly. In such cases it is advantageous to incorporate an inner cylindrical shield between said insulated wire and said at least one first concentric array to shield the signal-carrying conductors within the first concentric array from any electromagnetic field generated by the insulated wire. Alternatively, the cylindrical spacer forms a hollow tube.  
         [0027]     The insulator material of the ribbon cable can be made from the group of insulating materials consisting of perfluoralkoxy, fluoroethylene-propylene, polyester, polyolefin including polyethylene and polypropylene, polymethylpentene, full density polytetrafluoroethylene and is most preferably made from expanded polytetrafluorethylene. Foamed or extruded polymers can be used.  
         [0028]     The ribbon cable is preferably made from an upper and lower insulator which are both made from an upper and lower insulator which are both made of expanded PTFE and which are sintered to each other. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0029]      FIG. 1  shows the electrical signal line cable according to a first embodiment of the invention.  
         [0030]      FIG. 2  shows a device for the manufacture of the ribbon cables in the electrical signal line cable.  
         [0031]      FIG. 3  shows a sintering device used in the manufacture of the ribbon cables.  
         [0032]      FIG. 4  shows the electrical signal cable according to a second embodiment of the invention.  
         [0033]      FIG. 5  shows an end view of the electrical signal cable of the second embodiment of the invention.  
         [0034]      FIG. 6  shows the electrical signal cable according to a third embodiment of the invention.  
         [0035]      FIG. 7  shows the electrical signal cable according to a fourth embodiment of the invention.  
         [0036]      FIG. 8  shows the electrical signal cable according to a fifth embodiment of the invention.  
         [0037]      FIG. 9  shows the electrical signal cable according to a sixth embodiment of the invention.  
         [0038]      FIG. 10  shows the electrical signal cable according to a seventh embodiment of the invention.  
         [0039]      FIG. 11  shows the electrical signal cable according to a eighth embodiment of the invention.  
         [0040]      FIG. 12  is a perspective view of a cable assembly according to another exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]      FIG. 1  shows a first embodiment of the invention. It shows an electrical signal line  10  comprising a plurality of ribbon cables  20  helically wrapped about a cylindrical spacer  90 . Each layer or valence of ribbon cables  20  is separated by a separating spacer  50 . In  FIG. 1  four valences of sub cable assemblies  20  are shown. However, it is merely illustrative of the invention and not intended to be limiting.  
         [0042]     Each ribbon cable  20  comprises a plurality of individual signal conductors  30  arranged in a plane and surrounded by an upper insulating layer  40   a  and a lower insulating layer  40   b.  The upper insulating layer  40   a  and the lower insulating layer  40   b  are laminated together as will be explained later. The individual signal conductors  30  can be made from any conducting material such as copper, nickel-plated copper, tin-plated copper, silver-plated copper, tin-plated alloys, silver-plated alloys or copper alloys. Preferably the individual signal conductors  30  are made of round copper wire. It would also be possible to use flat conductors.  
         [0043]     The number of individual signal conductors  30  depicted in  FIG. 1  is not intended to limiting of the invention. The axes of the individual signal conductors  30  are separated in the plane by a first pitch distance a which is in the range of 0.1 to 1 mm. The upper insulating layer  40   a  and the lower insulating layer  40   b  can be made of any insulating dielectric material such as polyethylene, polyester, perfluoralkoxy, fluoroethylene-propylene, polypropylene, polymethylpentene, polytetrafluoroethylene or expanded polytetrafluorethylene. Preferably expanded polytetrafluoroethylene such as that described in U.S. Pat. Nos. 3,953,556, 4,187,390 or 4,443,657 is used.  
         [0044]     The separating spacer  50  is made, for example, from a metal foil, metal braid, conductive tape, a metallized textile or a dielectric spacer. The following metals can be used: copper, tin, silver, aluminum or alloys thereof. The dielectric spacer can be made from dielectric materials such as polyethylene, perfluoralkoxy, fluoroethylene-propylene, polypropylene, polymethylpentene, polytetrafluoroethylene or expanded polytetrafluorethylene (ePTFE).  
         [0045]     In one embodiment of the invention the separating spacer  50  was made from copper-coated polyamide fabric of the Kassel type supplied by the Statex company in Hamburg, Germany, and had a thickness of approximately 0.1 mm and a width of around 9 mm. In another embodiment of the invention, the separating spacer  50  was made from ePTFE. Separating spacers  50  which comprise a layer of dielectric material and a layer of conducting material are also conceivable.  
         [0046]     A first shielding means  60  is wrapped about the arrays of the ribbon cables  20 . An insulating layer  65  was then wrapped around the first shielding means  60  using known wire wrapping techniques. The insulating layer  65  may be made, for example, from PTFE, FEP, ePTFE or polyester. Preferably the insulating layer  65  is made from sintered GORE-TEX® tape which is obtainable from W. L. Gore &amp; Associates.  
         [0047]     A second shielding means  70  surrounds the insulating layer  65 . The first shielding means  60  and second shielding means  70  are a braid, foil or wire shield made from a metal or metallized polymer, such as copper, aluminum, tin-plated copper, silver-plated copper, nickel-plated copper or aluminized polyester.  
         [0048]     A jacket  80  is placed over the second shielding means  70 . The jacket  80  is made from silicone or polyolefins such as polyethylene, polypropylene or polyethylpentene; fluorinated polymers such as fluorinated ethylene/propylene (FEP); fluorinated alkoxypolymer such perfluoro(alkoxy)alkylanes, e.g. a co-polymer of TFE and perfluoropropylvinyl ether (PFA); polyurethane, polyvinyl chloride (PVC) or polytetrafluoroethylene (PTFE) or expanded PTFE. In one embodiment of the invention the jacket  80  was made from PVC.  
         [0049]     The cylindrical spacer  90  is made from ePTFE, PTFE, polyamide, polyurethane, persion or any other suitable material. The cylindrical spacer  90  may be solid or have a hollow interior to carry cooling fluids, electrical control or power lines, gases, etc. The cylindrical spacer  90  may be made from a braided or stranded material. The cylindrical spacer  90  can incorporate a strain relief and/or strength member. The term “cylindrical” does not imply that the cylindrical spacer  90  needs to be exactly cylindrical, rather it only needs to be substantially cylindrical to the extent that it acts as a support for the ribbon cables  20 .  
         [0050]     Manufacture of the ribbon cables  20  is illustrated in  FIG. 2  for the embodiment in which the upper insulating layer  140   a  and the lower insulating layer  140   b  are made from expanded PTFE. This method is essentially the same as that taught in U.S. Pat. No. 3,082,292 (Gore). The same reference numerals are used to denote the components of the ribbon cable  20  ( 120 ) as those used for the components of the ribbon cable  20  in the first embodiment of the invention ( FIG. 1 ) except that they are increased by  100 . A plurality of individual signal conductors  130 , an upper insulator  140   a  located above the plurality of individual signal conductors  130 , and a lower insulator  140   b  located below the plurality of individual signal conductors  130  were communally passed between two contra-rotating pressure rollers  200   a  and  200   b  at a lamination temperature sufficient to achieve bonding between the lower insulator  140   b  and the upper insulator  140   a,  e.g. between 327° C. and 410° C. A ribbon cable  120  was thereby formed. For this purpose, the upper pressure rollers  200   a  is provided with a number of upper peripheral grooves  210   a,  each separated by an upper peripheral rib  200   a  which are lined up at a distance from one another along the circumference of the pressure rollers  200   a.  Similarly, the lower pressure rollers  200   b  is provided with a number of lower peripheral grooves  210   b  each separated by a lower peripheral rib  200   b  which is lined up at a distance from one another along the circumference of the pressure roller  200   b.  Each upper peripheral groove  210   a  of the upper pressure roller  200   a  together with the adjacent upper peripheral ribs  200   a  lines up with one of the lower peripheral grooves  210   b  with the adjacent lower peripheral ribs  220   b  of the lower pressure roller  200   b  to form a passageway channel for one of the individual signal conductors  130 . The distance between the two pressure rollers  200   a,    200   b  and the peripheral grooves  210   a,    210   b  are designed in terms of their dimensions in such a way that a single conductor  130  and the upper insulator  140   a  and the lower insulator  140   b  pass continuously between a pair consisting of one of the upper peripheral grooves  210   a  and one of the lower peripheral grooves  210   b.  The upper peripheral ribs  220   a  and the lower peripheral ribs  220   b  have such a small separation from one other that the upper insulator  140   a  and the lower insulator  140   b  are firmly pressed together at these positions to form an intermediate zone  240  in the ribbon cable  120 .  
         [0051]     In order to improve their adhesion of the upper insulator  140   a  to the lower insulator  140   b  to the individual signal conductors  130  and with each other within the ribbon cable  120 , the ribbon cable  120  was led through a sintering device in which the ribbon cable  120  is heated such that one achieves intimate joining in the intermediate zones  240  of the ribbon cable  120 . If using an upper insulator  140   a  and a lower insulator  140   b  made of PTFE, use is made of a sintering temperature in the range from 327° to 410° C.  
         [0052]     An example of an embodiment of a sintering device in the form of a sintering oven  250  comprising a salt bath is illustrated in a schematic and simplified form in  FIG. 3 . In this example, the ribbon cable  120  is continually passed through the sintering oven  250 .  
         [0000]     Tests  
         [0053]     Tests were carried out on electrical signal cable assemblies of 2.0 m or 2.5 m length.  
         [0054]     To check the electrical characteristics of the assemblies, all ribbon cables within the cables were terminated to printed circuit boards. All of the ground conductors within the cable were connected together at a common AC ground.  
         [0055]     The measurement for impedance, capacitance and attenuation were carried out on a single signal conductor. All other signal conductors were open. For the other tests, the signal conductors were terminated by a resistor.  
         [0056]     The torsion test was carried out by gripping one end of a cable assembly firmly and measuring the torque required to turn the cable both clockwise and anti-clockwise at the other end of the cable assembly.  
       EXAMPLES  
       [0057]     The examples below illustrate cable constructions that can be made using the invention. The ribbon cables used had either 16, 24 or 32 individual conductors which were made from PD 135 alloy obtainable from Phelps Dodge in Irvine, Calif., USA. In Examples 1 to 4 and 6, conductors of AWG 4201 were used and the conductors were spaced 0.254 mm apart. In Example 5, conductors of AWG 4001 were used spaced 0.3556 mm apart. The ribbon cables were served at angles between 30° and 35°.  
         [0058]     The individual conductors were laminated using the method described between a first insulation layer and a second insulation layer made of ePTFE. In Examples 1 to 4 and 6, the insulation layers were each 0.0762 mm thick. In Example 5, the insulation layers were each 0.1016 mm thick.  
         [0059]     The binders used were made of ePTFE and were made from a tape of 0.08 mm thickness. These were wrapped over each other to give an average total thickness of the layer of 0.12 mm. The binders were wrapped at angles between 30° and 38° in a direction opposite to that of the flat cables.  
         [0060]     The outer shields used in examples 1 to 7 were made from tin plated copper wire of AWG 4401. In example 8, silver-plated copper wire of AWG 4401 was used.  
         [0061]     The outer jacket was made from extruded PVC and had a thickness of 0.76 mm.  
       Example 1  
       [0062]     A 48 element cable  10  made in accordance with the invention is depicted in  FIGS. 4 and 5 . The spacer  400  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 1.5±0.1 mm. A first flat cable  410  was wrapped in a first direction about the spacer  400 . A second flat cable  420  was wrapped about the first ribbon cable  410 . A first binder  430  made of eTPFE and having a thickness of 0.12 mm was wrapped in an opposite direction about the second flat cable  420 . A third flat cable  440  was wrapped about the first binder  430  as the second flat cable  420 . A fourth flat cable  450  was wrapped about the third flat cable  440 . A second binder  460  was wrapped about the fourth flat cable  450  in the opposite direction to the fourth flat cable  450 . A fifth flat cable  470  was wrapped about the second binder  460  in the opposite direction to the second binder  460  and thus as the first flat cable  410  and the second flat cable  420 . A third binder  480  was wrapped about the fifth flat cable  470 . An outer shield  485  was placed over the fifth flat cable  480  and a jacket  490  extruded over the outer shield  485 . The outer shield  485  was made by braiding wire at a braiding angle of 19° using 16 bobbins and 13 ends at 6 picks per inch (2.54 cm).  
         [0063]     In this example, the first flat cable  410 , the second flat cable  420 , the third flat cable  440 , the fourth flat cable  450  were made with 16 individual conductors. The fifth flat cable  470  was made with 32 individual conductors.  
         [0064]     The cable had a nominal outside diameter of 5.5 mm.  
       Example 2  
       [0065]     A 96 element cable  10  made in accordance with the invention is depicted in  FIG. 6 . The spacer  500  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 1.5±0.1 mm. A first flat cable  510  was wrapped about the spacer  500 . A second flat cable  520  was wrapped in the same direction about the first ribbon cable  510 . A first binder  530  was wrapped in an opposite direction about the second flat cable  520 . A third flat cable  540  was wrapped in the opposite direction about the first binder  530 . A fourth flat cable  545  was wrapped in the same direction about the third flat cable  540 . A fifth flat cable  550  was wrapped in the same direction about the fourth flat cable  545 . A second binder  560  was wrapped in the opposite direction about the fifth flat cable  550 . A sixth flat cable  565  was wrapped in the opposite direction about the second binder  560 . A third binder  567  was wrapped in the opposite direction about the sixth flat cable  565 . A seventh flat cable  570  was wrapped in the opposite direction about the third binder  567 . An eighth flat cable  573  was wrapped in the same direction about the seventh flat cable  570 . A ninth flat cable  576  was wrapped in the same direction about the eight flat cable  573 . A fourth binder  580  was wrapped in the opposite direction about the ninth flat cable  576 . The outer shield  585  was placed over the fourth binder  580  and a jacket  590  extruded over the outer shield  585 . The outer shield  585  was made by braiding wire at a braiding angle of 19.5° using 16 bobbins and 26 ends at 4.5 picks per inch (2.54 cm).  
         [0066]     In this example, the first flat cable  510 , the second flat cable  520 , the third flat cable  540  were made with 16 individual conductors. The fourth flat cable  545  and the fifth flat cable  550  were made with 24 individual conductors. The sixth flat cable  565 , the seventh flat cable  570 , the eighth flat cable  573  and the ninth flat cable  576  were made with 32 individual conductors.  
         [0067]     The cable  40  had a nominal outside diameter of 6.9 mm.  
       Example 3  
       [0068]     A 128 element cable  10  made in accordance with the invention is depicted in  FIG. 7 . The spacer  600  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 1.5±0.1 mm. A first flat cable  610  was wrapped about the spacer  600 . A second flat cable  620  was wrapped in the same direction about the first ribbon cable  610 . A first binder  630  made of ePTFE was wrapped in the opposite direction about the second flat cable  620 . A third flat cable  640  was wrapped in the opposite direction about the first binder  630 . A fourth flat cable  650  was wrapped in the same direction about the third flat cable  640 . A second binder  660  was wrapped about the fourth flat cable  650 . A fifth flat cable  670  was wrapped in the opposite direction about the second binder  660 . A sixth flat cable  675  was wrapped about the fifth flat cable  670 . A third binder  677  was wrapped in the opposite direction about the sixth flat cable  675 . A seventh flat cable  680  was wrapped about the third binder  677 . A fourth binder  682  was wrapped in the opposite direction about the seventh flat cable  680 . An eighth flat cable  684  and a ninth flat cable  686  were wrapped adjacent to each other side by side in the same cylindrical plan about the fourth binder  682 . A tenth flat cable  688  and an eleventh flat cable  690  were wrapped in the same direction adjacent to each other about the eighth flat cable  684  and the ninth flat cable  686 . A twelfth flat cable  692  and a thirteenth flat cable  694  were wrapped in the same direction about the tenth flat cable  688  and the eleventh flat cable  690 . A fifth binder  696  was wrapped in the opposite direction about the twelfth flat cable  692  and the thirteenth flat cable  694 .  
         [0069]     An outer shield  697  was placed over the fifth binder  696  and a jacket  698  extruded over the outer shield  697 . The outer shield  697  was made by braiding wire at a braiding angle of 20° using 16 bobbins and 26 ends at 4 picks per inch (2.54 cm).  
         [0070]     In this example, the first flat cable  610 , the second flat cable  620 , the eighth flat cable  684 , the tenth flat cable  688  and the twelfth flat cable  692  were made of 16 individual conductors. The third flat cable  640 , the fourth flat cable  650 , the fifth flat cable  670 , the sixth flat cable  675  and the eleventh flat cable  690  were made with 24 individual conductors. The seventh flat cable  680  and the thirteenth flat cable  694  were made with 32 individual conductors.  
         [0071]     In operation the seventh flat cable  680  was designed such that the individual conductors are placed at ground.  
       Example 4  
       [0072]     A 196 element cable  10  made in accordance with the invention is depicted in  FIG. 8 . The spacer  700  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 1.5±0.1 mm. A first flat cable  710  was wrapped about the spacer  700 . A second flat cable  720  was wrapped in the same direction about the first ribbon cable  710 . A first binder  730  was wrapped in the opposite direction about the second flat cable  720 . A third flat cable  740  was wrapped in the opposite direction about the first binder  730 . A fourth flat cable  750  was wrapped about the third flat cable  740 . A second binder  770  was wrapped in the opposite direction about the fourth flat cable  750 . A fifth flat cable  780  was wrapped in the opposite direction about the second binder  770 . A sixth flat cable  790  was wrapped in the same direction about the fifth flat cable  780 . A third binder  800  was wrapped in the opposite direction about the sixth flat cable  790 . A seventh flat cable  810  was wrapped in the opposite direction about the third binder  800 . An eighth flat cable  820  was wrapped about the seventh flat cable  810 . In the next layer, two flat cables, a ninth flat cable  830  and a tenth flat cable  835  were wrapped in the same direction adjacent to each other. Subsequently an eleventh flat cable  840  and a twelfth flat cable  845  were wrapped in the same direction in the same layer adjacent to each other. A fourth binder  850  was wrapped in the opposite direction about the eleventh flat cable  840  and the twelfth flat cable  845 . A thirteenth flat cable  860  and a fourteenth flat cable  865  were subsequently wrapped in the opposite direction about the fourth binder  850  adjacent to each other. A fifteenth flat cable  870  and a sixteenth flat cable  875  were wrapped in the same direction adjacent to each other about the thirteenth flat cable  860  and the fourteenth flat cable  865 . A fifth binder  880  was wrapped in the opposite direction about the fifteenth flat cable  870  and the sixteenth flat cable  875 .  
         [0073]     The outer shield  885  was placed over the fifth binder  880  and a jacket  890  extruded over the outer shield  885 . The outer shield  885  was made by braiding wire at a braid angle 22.5° using 16 bobbins and 26 ends at 4 picks per inch (2.54 cm).  
         [0074]     In this example, the first flat cable  710 , the second flat cable  720 , the third flat cable  740 , the fourth flat cable  750 , the ninth flat cable  830 , the eleventh flat cable  840 , the thirteenth flat cable  860  and the fifteenth flat cable  870  were made of 16 individual conductors. The fifth flat cable  780 , the sixth flat cable  790 , the seventh flat cable  810 , the eighth flat cable  820 , the tenth flat cable  835 , the twelfth flat cable  845 , the fourteenth flat cable  865  and the sixteenth flat cable  875  were made with 32 individual conductors.  
       Example 5  
       [0075]     A 196 element cable  10  made in accordance with the invention is depicted in  FIG. 9 . The spacer  1000  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 2.1±1 mm. A first flat cable  1010  was wrapped about the spacer  1000 . A second flat cable  1020  was wrapped in the same direction about the first flat cable  1010 . A first binder  1030  was wrapped in the opposite direction about the second flat cable  1020 . A third flat cable  1040  was wrapped in the opposite direction about the first binder  1030 . A fourth flat cable  1050  was wrapped in the same direction about the third flat cable  1040 . A second binder  1060  was wrapped in the opposite direction about the fourth flat cable  1050 . A fifth flat cable  1070  was wrapped in the opposite direction about the second binder  1060  and thus as the first flat cable  1010  and the second flat cable  1020 . A sixth flat cable  1080  was wrapped about the fifth flat cable  1070 . A seventh flat cable  1090  was wrapped in the same direction about the sixth flat cable  1080 . A third binder  1100  was wrapped in the opposite directions about the seventh flat cable  1090 . An eighth flat cable  1110  was wrapped in the opposite direction about the third binder  1100 . A ninth flat cable  1120  was wrapped in the same direction about the eight flat cable  1110 . A tenth flat cable  1130  was wrapped in the same direction about the ninth flat cable  1120 . A fourth binder  1140  was wrapped in the opposite direction about the tenth flat cable  1130 . In the next layer, two flat cables, an eleventh flat cable  1150  and a twelfth flat cable  1155  were wrapped in the opposite direction adjacent to each other. Subsequently a thirteenth flat cable  1160  and a fourteenth flat cable  1165  were wrapped in the same direction in the same layer adjacent to each other. A fifteenth flat cable  1170  adjacent to a sixteenth flat cable  1175  were then wrapped in the same direction about the layer containing the thirteenth flat cable  1160  and the fourteenth flat cable  1165 . A fifth binder  1180  was wrapped in the opposite direction about the fifteenth flat cable  1170  and the sixteenth flat cable  1175 .  
         [0076]     The outer shield  1185  was placed over the fifth binder  1180  and a jacket  1190  extruded over the outer shield  1185 . The outer shield  1185  was made by braiding wire at a braiding angle of 21.5″ using 24 bobbins and 26 ends at 4.5 picks per inch (2.54 cm).  
         [0077]     In this example, the first flat cable  1010 , the second flat cable  1020 , the third flat cable  1040 , the fourth flat cable  1050 , the fifth flat cable  1070 , the eleventh flat cable  1150 , the thirteenth flat cable  1160  and the fifteenth flat cable  1170  were made of 16 individual conductors. The sixth flat cable  1080 , the seventh flat cable  1090 , the eighth flat cable  1110 , the ninth flat cable  1120 , the tenth flat cable  1130 , the twelfth flat cable  1155 , the fourteenth flat cable  1165  and the sixteenth flat cable  1175  were made with 32 individual conductors.  
       Example 6  
       [0078]     A further example of a cable  10  containing 192 elements according to this construction is shown in  FIG. 10 .  
         [0079]     The spacer  1200  was made of woven Kevlar yarn and had a nominal outside diameter of 0.6±0.1 mm. Eight leads  1203  were placed about the spacer  1200 . The leads were made of tin-plated copper conductors of AWG 3601 and had a polyester insulation. A first binder  1205  was placed about the leads. A first flat cable  1210  was wrapped in the opposite direction about the first binder  1205 . A second flat cable  1220  was wrapped in the same direction about the first flat cable  1210 . A second binder  1230  was wrapped in the opposite direction about the second flat cable  1220 . A third flat cable  1240  was wrapped in the opposite direction about the second binder  1230 . A fourth flat cable  1250  was wrapped in the same direction about the third flat cable  1240 . A fifth flat cable  1260  was wrapped in the same direction about the fourth flat cable  1250 . A third binder  1270  was wrapped in the opposite direction about the fifth flat cable  1260 . A sixth flat cable  1280  was wrapped in the opposite direction about the third binder  1270 . A seventh flat cable  1290  was wrapped in the same direction about the sixth flat cable  1280 . An eighth flat cable  1300  was wrapped about the seventh flat cable  1290 . A fourth binder  1310  was wrapped in the opposite direction about the eighth flat cable  1300 . A ninth flat cable  1320  was wrapped in the opposite direction about the fourth binder  1310 . A fifth binder  1330  was wrapped in the opposite direction about the ninth flat cable  1320 . In the next layer, two flat cables, a tenth flat cable  1340  and an eleventh flat cable  1345  were wrapped in the opposite direction adjacent to each other. Subsequently a twelfth flat cable  1350  and a thirteenth flat cable  1355  were wrapped in the same direction in the same layer adjacent to each other. A sixth binder  1360  was wrapped in the opposite direction about the twelfth flat cable  1350  and the thirteen flat cable  1355 . A fourteenth flat cable  1370  and a fifteenth flat cable  1375  were subsequently wrapped in the opposite direction about the sixth binder  1360  adjacent to each other. A sixteenth flat cable  1380  and a seventeenth flat cable  1385  were wrapped in the same direction adjacent to each other about the fourteenth flat cable  1370  and the fifteenth flat cable  1375 . A seventh binder  1390  was wrapped in the opposite direction about the sixteenth flat cable  1380  and the seventeenth flat cable  1385 .  
         [0080]     The outer shield  1395  was placed over the seventh binder  1390  and a jacket  1397  extruded over the outer shield  1395 . The outer shield  1395  was made by braiding wire at a raiding angle of 29.5° using 16 bobbins and 26 ends at 5 picks per inch (2.54 cm).  
         [0081]     In this example, the first flat cable  1210 , the second flat cable  1220 , the tenth flat cable  1340 , the twelfth flat cable  1350 , the fourteenth flat cable  1370  and the sixteenth flat cable  1380  were made of 16 individual conductors. The third flat cable  1240 , the fourth flat cable  1250 , the fifth flat cable  1260  and the sixth flat cable  1280  were made of 24 individual conductors. The seventh flat cable  1290 , the eighth flat cable  1300 , the ninth flat cable  1320 , the eleventh flat cable  1345 , the thirteenth flat cable  1355 , the fifteenth flat cable  1375  and the seventeenth flat cable  1385  were made with 32 individual conductors.  
       Example 7  
       [0082]     A 600 element cable  10  made in accordance with the invention is depicted in  FIG. 11 .  
         [0083]     The space  1400  was made of woven Kevlar yarn over which was extruded a PVC layer. It had a nominal outside diameter of 1.5±0.1 mm. In a first layer  1410 , a sixteen conductor flat cable was wrapped about the spacer and in a second layer  1420 , a further sixteen conductor flat cable was wrapped in the same direction about the first flat cable. The third layer  1430  has a binder wrapped in the opposite direction about the flat cable in the second layer  1420 . The fourth layer  1440 , the fifth layer  1450  and the sixth layer  1460  consisted respectively of twenty-four conductor flat cables wrapped in the same direction one layer above each other but in the opposite direction to the third layer  1430 . The seventh layer  1470  comprises a binder wrapped in the opposite direction about the sixth layer  1460 . The eighth layer  1480 , the ninth layer  1490 , the tenth layer  1500  and the eleventh layer  1510  comprises thirty-two conductor flat cables wrapped in the same direction one layer on another layer but in the opposite direction to the binder in the seventh layer  1470 . The twelfth layer  1520  comprised a binder wrapped in the opposite direction about the eleventh layer  1510 . The thirteenth layer  1530  comprises a sixteen conductor flat cable and a twenty-four conductor flat cable wrapped in the opposite direction adjacent to each other about the twelfth layer  1520 . The fourteenth layer  1540  and the fifteenth layer  1550  each comprises a sixteen conductor flat cable and a thirty-two conductor flat cable wrapped in the same direction adjacent to each other one layer on another layer. The sixteenth layer  1560  was a binder wrapped in the opposite direction about the fifteenth layer  1550 . The seventeenth layer  1570  and the eighteenth layer  1580  each comprises a twenty-four conductor flat cable and a thirty-two conductor flat cable wrapped in the same direction adjacent to each other one layer on the other layer but in the opposite direction to the binder in the sixteenth layer. The nineteenth layer  1590  comprises two thirty-two conductor flat cables wrapped adjacent to each other about the eighteenth layer  1580 . About the nineteenth layer  1590 , a binder in the twentieth layer  1600  was wrapped in the opposite direction. Each of the twenty-first layer  1610 , the twenty-second layer  1620  and the twenty-third lay  1630  comprised two thirty-two conductor flat cables wrapped in the same direction adjacent to each other one on top of each other but in the opposite direction to the binder in the twentieth layer  1600 . The twenty-fourth layer  1640  comprises a binder wrapped in the opposite direction about the twenty-third layer  1630 . The twenty-fifth layer  1650  and the twenty-sixth layer  1660  each comprised three thirty-two conductor flat cables wrapped in the same direction adjacent to each other one layer on the other but in the opposite direction to the binder in the twenty-fourth layer  1640 . The twenty-seventh layer  1670  had a binder wrapped in the opposite direction about the twenty-sixth layer  1660 . The twenty-eighth layer  1680  and the twenty-ninth layer  1690  each had two twenty-four conductor flat cables and a thirty-two conductor flat cable wrapped in the same direction adjacent to each other one layer on another layer but in the opposite direction to the binder in the twenty-sixth layer  1660 . The thirtieth layer  1700  comprised a binder wrapped in the opposite direction about the twenty-ninth layer  1690 . The thirty-first layer  1710  and the thirty-second layer  1720  each had two twenty-four conductor flat cables and a single thirty-two conductor flat cable wrapped in the same direction adjacent to each other one layer on top of another layer but in the opposite direction to the binder in the thirtieth layer  1700 . The thirty-third layer  1730  was a binder wrapped in the opposite direction about the thirty-second layer  1720 .  
         [0084]     An outer shield  1740  was placed over the thirty-third layer and a jacket  1750  extruded over the outer shield  1740 . The outer shield  1740  was made by braiding the wire at an angle of 21.8° using 24 bobbins and 39 ends at 3.5 picks per inch (2.54 cm).  
       Comparative Example  
       [0085]     Comparative results were obtained from a micro-coaxial cable having conductors made of PD135 alloy of AWG 4001. This cable is obtainable form W. L. Gore &amp; Associates GmbH under the designation J14B0596-A.  
                                                 TABLE 1                           Results                        Insertion Loss   Conductor                       Impedance   Capacitance   @ 10 MHz   Resistance   Weight   Torsion   Time Delay       Example No.   (Ω)   (pF/ft)   (dB/Assembly)   (Ω/m)   (g/m)   (mNm)   (ns/2.5 m)               Comparative   49   32.0       4.3   99.2   +10/−10           Example       3   120-128   11.6-13.9   −1.5   7.2-8.0   57.4   +50/−10   12.0-13.3       4   113-124   11.0-13.7   −1.5   7.6-8.2   68.3                  
 
         [0086]     The range of results in Table 1 indicate that the measurements were made on different layers within the cable.  
         [0087]     In a preferred embodiment, shown in  FIG. 12 , a plurality of electrical signal lines  10  having the construction described above are grouped together in a single cable around center line  2000 . In the preferred embodiment illustrated, for signal lines  10  are grouped around center line  2000 . Each signal line  10  may be individually shielded with a semiconductive material. This is effective for reducing crosstalk between signal lines  10  CW Doppler applications, for example. Alternatively, semiconductive material  2001  may be wrapped around the multi-core construction. Semiconductive layer  2001  can be constructed alternatively of carbonized ePTFE or hybrid of ePTFE and aluminum or PTFE and aluminum. A braided shield  2002  is preferably disposed around the plurality of signal lines  10 . A jacket, preferably made of PVC  2003 , is preferably disposed around the braided shield  2002 . Using a plurality of signal lines  10  to form a cable, rather than one, larger signal line  10 , provides distinct advantages in application of the present invention. Specifically, providing the plurality of smaller signal lines  10  as opposed to one large signal line provides high flexibility and conformability of the cable. Such a cable also demonstrates superior flex life due to the single cord freely moving against each other. Furthermore, because of the use of semiconductive layer  2001 , there is no triboelectric noise generated within the cable.  
         [0088]     Further Examples  
         [0089]     A further embodiment of the invention is conceivable which consists of alternate layers of binder and ribbon cables in concentric arrays. The binders and ribbon cables are wrapped in opposite directions. The ribbon cables are wrapped at slightly different angles in each concentric array so that the electrical conductors do not run parallel to each other over the whole of the electrical signal cable assembly.  
         [0090]     Although a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages which are described herein. Accordingly, all such modifications are intended to be included within the scope of the present invention, as defined by the following claims.