Patent Publication Number: US-6340795-B1

Title: Electrical cable

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to the field of cables, and particularly to electrical cables. 
     BACKGROUND OF THE INVENTION 
     Data transmission is one of the most important aspects in modem life. With the increase in processor speeds and devices that are able to perform their functions in an increasingly faster manner, the transmission of the resulting information must be transmitted even faster to realize these advances. For example, currently, round wire conductor (RWC) is used which does not allow the density needed for very high-density cable interconnect (VHDCI) and other very high density connects on cabling for I/O data applications. This is because center to center spacing and wire size plus impedance controls are currently being utilized at the limit of practical usage in a commercial environment. Thus, there exists a need for an electrical cable suitable for increased data transmission. For instance, there is a need for an easy to use differential vertically paired flat conductor cable (FCC) and a high density controlled impedance differential paired cable suitable for use with low voltage differential signals (LVDS) in I/O data applications. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an improved electrical cable. In a first aspect of the present invention, an electrical cable includes a first flat conductor surrounded by an insulator and a second flat conductor surrounded by an insulator, wherein the first flat conductor and the second flat conductor are spaced so as to form an electrical differential pair. 
     In a second aspect of the present invention, an electrical cable includes a first pair of electrical conductors. The first pair of electrical conductors includes a first flat conductor surrounded by an insulator and a second flat conductor surrounded by an insulator. The first flat conductor and the second flat conductor are spaced so as to form an electrical differential pair. The electrical cable also includes a second pair of electrical conductors including a third flat conductor surrounded by an insulator and a fourth flat conductor surrounded by an insulator. The third flat conductor and the fourth flat conductor are spaced so as to form an electrical differential pair. A spacer is disposed between the first pair of electrical conductors and the second pair of electrical conductors. The spacer is formed so as to isolate an electromagnetic field from the first pair of electrical conductors from an electromagnetic field from the second pair of electrical conductors so as to reduce cross talk and between the pairs. 
     In a third aspect of the present invention, an electrical cable includes a first pair of electrical conductors. The first pair of electrical conductors includes a first flat conductor surrounded by an insulator and a second flat conductor surrounded by an insulator. The first flat conductor and the second flat conductor are spaced so as to form an electrical differential pair. The electrical cable also includes a second pair of electrical conductors including a third flat conductor surrounded by an insulator and a fourth flat conductor surrounded by an insulator. The third flat conductor and the fourth flat conductor are spaced so as to form an electrical differential pair. A spacer is disposed between the first pair of electrical conductors and the second pair of electrical conductors. The spacer is formed so as to control an electromagnetic envelope of the first pair of electrical conductors with respect to the second pair of electrical conductors. 
     It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
     FIG. 1 is an illustration of an exemplary embodiment wherein two conductors are paired together to create an electrical pair of flat conductors; 
     FIG. 2 is an illustration of an exemplary embodiment of the present invention wherein a first pair of conductors and a second pair of conductors are constructed utilizing a spacer so that the first pair of conductors and the second pair of conductors are at an isolated electromagnetic distance; 
     FIG. 3 is an illustration of an exemplary embodiment of the present invention wherein multiple pairs of electrical conductors are utilized to form a ribbon cable; and 
     FIG. 4 is an illustration of an exemplary embodiment of the present invention wherein a cable includes staggered pairs of electrical conductors. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
     Referring now to FIG. 1, an exemplary embodiment of the present invention is shown wherein two conductors are paired together to create an electrical pair of flat conductors. A cable  100  includes a first vertical flat conductor  102  and a second vertical flat conductor  104 . Preferably, the first vertical flat conductor  102  and the second vertical flat conductor  104  are formed out of copper or another metal that is electrically conductive. An insulator  106  is formed so as to surround the first vertical flat conductor  102  and the second flat conduct  104 . 
     Preferable, the first vertical flat conductor  102  and the second vertical flat conductor  104  are paired together to create an electrical pair of vertical flat conductors with a spacing geometry  108  to create an effective electrical differential pair. For example, a signal may be carried on both the first vertical flat conductor  102  and the second vertical flat conductor  104 . The voltage on these two conductors may then be utilized to determine whether the signal is a logical one, or a logical zero. By using both the first vertical flat conductor  102  and the second vertical flat conductor  104  to carry a differential signal, interference may be greatly reduced by spacing the first vertical flat conductor  102  and the second vertical flat conductor  104  so that interference signals are common to both conductors, and therefore cancel out. 
     Preferable, the insulator  106 , first vertical flat conductor  102  and second flat conduct  104  are fabricated from a material that provides both the desired respective electrical properties, for example conductivity, dielectric insulation, and the like, and desired respective physical properties such as flexibility such that cable  100  is at least a partially flexible structure. Vertical flat conductors are desirable because they easier to control both the width and depth of material of the conductor as well as the spacing between the conductors. Thus, the capacitance, cross talk, conductance, impedance and DC resistance may be more easily controlled as desired by a user. Additionally, the electrical cable may be formed using extrusion technology, thereby enabling the cable to be produced in a time efficient and cost-effective manner. 
     Referring now to FIG. 2, an exemplary embodiment of the present invention is shown wherein a first pair of conductors and a second pair of conductors are constructed utilizing a spacer so that the first pair of conductors and the second pair of conductors can be made to be at an isolated electrical and electromagnetic distance. A cable  200  includes a first pair of electrical conductors  210  and a second pair of electrical conductors  220 . The first pair of conductors  210  may include a first conductor  212  and a second conductor  214  so as to create an effective electrical differential pair, for instance, suitable for operating in an even or odd mode. Likewise, the second pair of conductors  220  may include a first conductor  222  and a second conductor  224  to create an electrical differential pair. An insulator  202  may be formed to surround the electrical conductors  212 ,  214 ,  222  and  224 . Thus, the present invention may provide a differential vertically paired vertical flat conductor cable (FCC) and a high density controlled impedance differential paired cable for use with low voltage differential signals (LVDS) in I/O data applications. 
     Additionally, a spacer  230  may be included between the first pair of electrical conductors  210  and the second pair of electrical conductors  220 . Preferable, the spacer  230  is formed so as to isolate the first pair of electrical conductors  210  from the second pair of electrical conductors  220  electromagnetic field. For example, the spacer  230  may separate the pairs at an isolated electromagnetic distance. Thus, it is possible to more closely control the electrical and magnetic parameters that influence high speed signal quality in “ribbon cable”. In this way, the electromagnetic envelope of the signaling environment may be controlled. In one embodiment, the electrical conductors  212 ,  214 ,  222  and  224  are flat conductors formed in generally rectangular shapes and positioned vertically to each other. For instance, the electrical conductors may be positioned orthogonal to the plane of the cable. Each pair of electrical conductors  210  and  220  include two electrical conductors  212 ,  214  and  222 ,  224  oriented generally parallel to each other. The spacer  230  may be formed at a midpoint of the connector so as to impart a generally “H” structure to the first pair of electrical conductors  210 —spacer  230 —second pair of electrical conductors  220  arrangement. Additionally, the “H” structure also allows a connector construct/design with insulation displacement cabling formats for connector attachment in the “middle” of the cable, instead of just at the end. 
     Referring now to FIG. 3, an exemplary embodiment of the present invention is shown wherein multiple pairs of electrical conductors are utilized to form a ribbon cable. A first pair of electrical conductors  302 , a second pair of electrical conductors  304 , and a third pair of electrical conductors  306  may be spaced with the use of spacers  308  and  310  disposed between the electrical conductors  302 ,  304  and  306 . The spacing distance may be varied depending on the desired properties of the corresponding electromagnetic envelope formed by the respective conductors. For example, the interference between the second pair of electrical conductors  304  and the third pair of electrical conductors  306  may be less than the interference between the third pair of electrical conductors  306  and a fourth pair of electrical conductors  312 . Therefore, a spacer  314  resulting in a greater length between conductors may be utilized between the third pair of electrical conductors  306  and the fourth pair of electrical conductors  312  than the spacer utilized between the second pair of electrical conductors  304  and the third pair of electrical conductors  306 . 
     It should be noted that a cable  300  may be varied to include a number of conductors depending upon the number of conductive paths required for the particular application of cable  300 . For instance, a variety of standards may utilize the present invention. For example, in one embodiment contemplated by the present invention, cable  300  may be compliant with a small computer system interface (SCSI) standard, such as SCSI parallel interface (SPI-4), integrated device electronics (IDE), advanced technology attachment (ATA), insulation displacement cable (IDC), insulation displacement termination (IDT), Ultra2, intelligent peripheral interface (IPI), high performance parallel interface (HIPPI), very high density cable interconnect (VHDCI) standard, and the like standard as contemplated by a person of ordinary skill in the art without departing from the spirit and scope of the present invention. For instance, in one embodiment, the cable is compliant with a very high density cable interconnect (VHDCI) standard, and is suitable for employing an insulation displacement cable (IDC) type connector. In another embodiment, the cable is compliant with the SPI-4 standard. 
     Referring now to FIG. 4, an exemplary embodiment of the present invention is shown wherein a cable includes staggered pairs of electrical conductors. A cable  400  may include pairs of electrical conductors  402 ,  404 ,  406  and  408  that are staggered. Staggering may provide room for displacement of insulation when utilizing a connector and also provide electromagnetic isolation. The pairs may be non-electrically bonded together for control of mechanical strength and electromagnetic properties, such as impedance, capacitance, inductance, and the like. Additionally, the electrical cable may be formed using extrusion technology, thereby enabling the cable to be produced in a time efficient and cost-effective manner. 
     It is believed that the electrical cable of the present invention and many of its attendant advantages will be understood by the forgoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.