Patent Publication Number: US-2015075695-A1

Title: Cable for electrical and optical transmission

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 12/895,842, filed Sep. 30, 2010, which is incorporated by reference. 
    
    
     BACKGROUND 
     The amount of data transferred between electronic devices has grown tremendously the last few years. Large amounts of audio, video, text, and other types of data content, are now regularly transferred among computers, media devices, such as handheld media devices, displays, storage devices, and other types of electronic devices. Since it is often desirable to transfer this data rapidly, the data rates of these transfers have substantially increased. 
     This data is often transferred over cables. Unfortunately, these cables may not be capable of conveying signals at these higher data rates. But while improved cables capable of operating at higher speeds are desirable, it is often useful to be backward compatible with older or legacy technologies. Accordingly, it is desirable to have cables that can operate at these higher data rates while remaining compatible with legacy technologies. 
     One feature common to cables is the use of a braided shield. This shield may be placed around one or more center conductors of the cable. This shield is typically braided, that is, it is typically formed of interwoven wire. 
     But this weave can be difficult to manipulate during cable manufacturing. For example, during cable manufacturing, the braiding may be pulled apart and soldered to form a ground connection with one or more strain-reliefs, circuits, connector pins, or other circuits or cable components. Since the braiding is woven, it may be difficult to pull apart and solder. Accordingly, it is desirable to have a shield that is more easily manipulated during manufacturing. 
     One difficulty encountered with cables is that they may be pulled, stretched, twisted, or bent. This may damage or break either the cable or one or more internal conductors. Accordingly, it is also desirable to have cables that have increased strength and are less likely to be damaged by twisting or bending. 
     Thus, what is needed are circuits, methods, and apparatus that provide cables capable of high-speed transmission while remaining compatible with legacy signals, have shielding that may be easily manipulated during manufacturing, have good tensile strength, and are less likely to be damaged by twisting and bending that may occur during use. 
     SUMMARY 
     Accordingly, embodiments of the present invention may provide circuits, methods, and apparatus that provide cables capable of high-speed transmission while remaining compatible with legacy signals. Embodiments of the present invention may have shielding that may be easily manipulated during manufacturing. Embodiments of the present invention may have good tensile strength, and may be less likely to be damaged by twisting and bending that may occur during use. 
     An illustrative embodiment of the present invention may provide a cable having both fiber-optic cables and electrical conductors. The fiber-optic cables may be useful in conveying high-speed signals that are compliant with current and newly developing signaling standards. The electrical conductors may be useful in conveying signals compliant with current or legacy standards, such as USB2. 
     To increase cable flexibility of various embodiments of the present invention, the fiber-optic cables may be twisted around each other. Further, to reduce the losses incurred by this twisting, the fiber-optic cables may be annealed. In one specific embodiment of the present invention, this annealing may occur during the encapsulation of the cable in a jacket. The fiber-optic cables may be formed of glass, polytetrafluoroethylene, or other material. 
     In various embodiments of the present invention, the electrical conductors may have different diameters. For example, the power conductors may have a large diameter to increase the conductor&#39;s current-carrying capability. Data or signal conductors may have a smaller diameter to limit the cross talk and capacitance. 
     Another illustrative embodiment of the present invention may include and arrange conductors and other materials such that the cable has a relatively rounded cross section. This may help limit damage that may occur due to bending and twisting of the cable. Specifically, embodiments of the present invention may include additional conductors. For example, additional power conductors may be included. In other embodiments of the present invention, fillers or other fibers may be included. These may be formed of cotton, aramid, or other materials. 
     Another illustrative embodiment of the present invention may include reinforcing members for strength. For example, the aramid fillers mentioned above may be used to provide a rounded cross section as well as increased strength. These or other fibers may also be used in the electrical conductors. 
     Another illustrative embodiment of the present invention may use multiple counter-rotating spirals as a shield in place of a conventional braid. This may provide increased flexibility and may be easily manipulated during cable manufacturing. 
     Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be gained by reference to the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates various layers of a high-speed cable according to an embodiment of the present invention; 
         FIG. 2  illustrates a cross-section of a cable according to an embodiment of the present invention; 
         FIG. 3  illustrates a side view of a portion of the cable according to an embodiment of the present invention; 
         FIG. 4  illustrates a cross-section of a cable according to an embodiment of the present invention; 
         FIG. 5  illustrates a detailed view of fiber optic cables that may be employed by cables according to an embodiment of the present invention; 
         FIG. 6  illustrates a side view of two fiber-optic cables wrapped around each other; and 
         FIG. 7  illustrates a method of manufacturing a cable according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
       FIG. 1  illustrates various layers of a high-speed cable according to an embodiment of the present invention. This cable includes center conductors  110 , dielectric  120 , shield  130 , and jacket  140 . Center conductors  110  may include single conductors, coaxial conductors, or pairs of conductors, such as twinaxial, twisted-pair, shielded twisted pair, or other pairs of conductors. The conductors may convey power, data, status or other information. The conductors may be single wires or multiple strands of wires. In some embodiments of the present invention, one or more conductors may be formed of a group of strands of wires, where each wire is coated with a layer of material to provide spatial separation among the strands. This separation aids in limiting skin effects and thus limits skin effects. This layer of material may be enamel or other material. The wires may be arranged as a Litz wire. Each of these various conductors may be formed of copper, aluminum, or other conductive material. They may be coated or plated with a layer to protect the wire from oxidation, for example, they may be plated with silver. 
     Dielectric  120  may be included to isolate shield  130  from center conductors  110 . Selection of a low-loss tangent dielectric  120  may increase isolation and reduce capacitance coupling effects between center conductors  110  and shield  130  as compared to a lower-quality, higher-loss tangent dielectric. 
     Shield  130  may provide a ground path through the cable. Shield  130  may also provide electrical isolation (or RF shielding or isolation) for the center conductors  110 . This isolation may protect the center conductors  110  from receiving noise and spurious signals, and the isolation may protect other lines or circuits from noise and spurious signals generated on the center conductors  110 . Jacket  140  may be used to insulate shield  130 , to provide mechanical support, and to provide a tactile surface for users to manipulate. 
     Again, embodiments of the present invention may provide improved cables. These cables may include reinforcing members for improved strength. They may include conductors for power and data transmission. They may employ fibers or other filler material such that the cable has an approximately rounded cross-section. The cables may also be shielded in a manner that provides for easy manipulation during manufacturing. An example is shown in the following figure. 
       FIG. 2  illustrates a cross-section of a cable according to an embodiment of the present invention. This cable may include data conductors  210 , power conductors  220 , reinforcing members (shown here as aramid fibers)  230 , and filler  240 . Conductors  210  and  220 , aramid fibers  230 , and filler  240 , may be wrapped in Mylar layer  250 . Counter-rotating spirals may provide a shield  260 , which may be encapsulated by jacket  270 . 
     Data connectors  210  may be insulated by insulating layers  212 . Conductors  210  may be relatively narrow to reduce capacitance from the conductor  210  to the other connectors  210  and  220 , shield  260 , as well as external conductors. 
     Power conductors  220  may be insulated by insulating layers  222 . Connectors  220  may be relatively wide to handle relatively large amounts of current. 
     Reinforcing members  230  may also be included to provide increased cable strength. Again, in this example, the reinforcing members are aramid fibers  230 . Aramid fibers  230  may be located inside one or more of conductors  210  and  220 . Aramid fibers  230  may also be located between or around conductors  210  and  220 . In this specific example, one of aramid fibers  230  may be located between conductors  210  and  220 . 
     It may be desirable that these cables have a relatively rounded cross section. This rounded shape may improve cable flexibility and reliability. Accordingly, a number of fillers  240  may be used. These fillers may be polytetrafluoroethylene, cotton, or they may be formed of other types of material. 
     Connectors  210  and  220 , fibers  230 , and filler  240 , may be wrapped in Mylar layer  250 . Mylar layer  250  may keep the bundle of individual conductors, fibers, and filler together during manufacturing. 
     Again, it may be desirable to provide a shield to isolate conductors  210  and  220  from external noise sources, as well as to prevent noise and spurious signals on conductors  210  and  220  from radiating away from the cable. It may also be desirable to have a shield that is easily manipulated during manufacturing. For example, each end of these cables may be connected to a connector plug during manufacturing. As part of this connection, the shield may be soldered to a portion of one or more of these connector plugs. Accordingly, it may be desirable that the shield be easily handled such that it may be connected in this way. 
     Accordingly, various embodiments of the present invention employ wires in counter-rotating spirals, such as counter-rotating spirals  260 . Counter-rotating spirals may comprise two layers of wires wrapped in opposing directions. By having the wires wrapped in this way, as opposed to a conventional braiding, wires in the shield may be easily manipulated during manufacturing. That is, the wires may be easily unwound from around the inside conductors. While various embodiments of the present invention utilize these counter-rotating spirals, other embodiments of the present invention may employ conventional braiding or other shielding techniques. 
     Jacket  270  may be extruded around the cable for mechanical support and handling by a user. 
     Again, embodiments of the present invention may employ two counter-rotating spirals as a shield. An example is shown in the following figure. 
       FIG. 3  illustrates a side view of a portion of the cable according to an embodiment of the present invention. This figure illustrates a cable surrounded by jacket  310 . Jacket  310  has been cut away to reveal a first counter-rotating spiral  320  and a second counter-rotating spiral  330 . The first of these spirals may have an angle approximately equal to phi  340 . In a specific embodiment of the present invention, phi may be equal to 17 degrees. In other embodiments of the present invention, other angles may be used. The second of these may have approximately the same relative angle, shown here as negative phi  342  to indicate a different absolute direction. 
     In this way, during manufacturing, the wires in the counter-rotating spirals  320  and  330  may be easily peeled away, straightened, and soldered or otherwise electrically connected to locations in a connector plug. 
     Utilizing counter-rotating spirals  320  and  330  may also improve flexibility of the cable. For example, when the cable is twisted in a first direction, counter-rotating spiral  320  may tighten while counter-rotating spiral  330  may loosen. The tightening of counter-rotating spiral  320  may protect the internal conductors. Similarly, when the cable is twisted in a second direction, counter-rotating spiral  330  may tighten while counter-rotating spiral  320  may loosen. The tightening of counter-rotating spirals  330  may protect the internal conductors. 
     Again, data rates for signals over these cables have been increasing at a tremendous rate. Accordingly, improvements to these cables may be needed to handle the higher data rates. But it is often desirable to be able to support legacy standards. Accordingly, embodiments of the present invention may provide cables that are capable of these higher data rates while still supporting legacy standards. An example is shown in the following figure. 
       FIG. 4  illustrates a cross-section of a cable according to an embodiment of the present invention. This figure may include fiber optic cables  410 , data conductors  420 , power conductors  430 , shield  440 , Mylar layer  450 , and jacket  460 . 
     Fiber-optic cables  410  are capable of handling very high data rates. In this example, two fiber-optic cables may be included for full duplex communication. In other embodiments of the present invention, one cable, or more than two cables, may be included. These fiber-optic cables may be glass, polytetrafluoroethylene, or other material. In a various embodiments of the present invention, these fiber-optic cables may be used to convey signals that are consistent with standardized or proprietary signaling schemes that have been developed, are currently being developed, or will be developed in the future. 
     While fiber-optic cables  410  are capable of handling high data rates, many current electronic devices communicate over electrical conductors. For example, USB1 and USB2 devices communicate using electrical conductors. Accordingly, embodiments of the present invention also include electrical conductors for conveying signals according to legacy standards, such as USB1 and USB2. 
     Accordingly, this specific example includes electrical conductors  420 . As before, electrical conductors  420  may be relatively narrow to reduce parasitic capacitances. These electrical conductors may be isolated by insulation layers  422 . Power conductors  430  may be relatively wide to increase current handling capabilities. Power conductors  430  may be insulated by isolation layers  432 . Electrical conductors  420  and  430  may be single wires, or multiple strands of wires. In some embodiments of the present invention, one or more conductors may be formed of a group of strands of wires, where each wire is coated with a layer of material to provide spatial separation among the strands. This separation aids in limiting skin effects and thus limits skin effects. This layer of material may be enamel or other material. The wires may be arranged as a Litz wire. Each of these various conductors may be formed of copper, aluminum, or other conductive material. They may be coated or plated with a layer to protect the wire from oxidation, for example, they may be plated with silver. 
     As before, Mylar layer  440  may be used to hold the conductors and fiber-optic cables together during manufacturing. Fillers and fibers (not shown), such as aramid fibers, may be used to provide a rounded cross section and reinforcement. For example, the aramid or other types of fibers may be included around, among, or inside the various cables and conductors of embodiments of the present invention. 
     Shield  450  may be used to isolate conductors  420  and  430 . This shielding may be formed using conventional techniques, such as braiding. In other embodiments of the present invention, counter-rotating spirals may be used, as shown above. Jacket  460  may be extruded around the cable for mechanical support and handling by a user. 
       FIG. 5  illustrates a detailed view of fiber optic cables  510  that may be employed by cables according to an embodiment of the present invention. Cables  510  may be mechanically supported by filler  520 . Fiber-optic cables  510  and fillers  520  may be wrapped by Mylar film  530  for mechanical support during manufacturing. 
     Fiber optic cables  510  may be wrapped around each other. This may improve flexibility of the overall cable. For example, if fiber-optic cables  510  are parallel to each other throughout the cable, when the cable is bent, a fiber-optic cable inside the bending radius may experience a compression force, while a fiber-optic cable outside the bending radius may experience an expansion force. These differential forces may damage the cable. By twisting or wrapping the cables around each other, these compression and expansion forces may be distributed along the length of the cable, thereby improving cable reliability. An example is shown in the following figure. 
       FIG. 6  illustrates a side view of fiber-optic cables  610  and  620  wrapped around each other. As fiber-optic cables  610  and  620  are bent, compression and expansion forces are distributed along the length of the fiber-optic cables, thereby improving overall cable flexibility and reliability. 
     Unfortunately, twisting fiber-optic cables in this way can increase their loss significantly. Accordingly, embodiments of the present invention anneal these fiber-optic cables after twisting to reduce this loss. In a specific embodiment of the present invention, this annealing occurs during jacket extrusion. An example is shown in the following figure. 
       FIG. 7  illustrates a method of manufacturing a cable according to an embodiment of the present invention. A number of spools  710  may provide power and data conductors  720  and fiber-optic cables  730  for a cable. Power and data conductors  720  and fiber-optic cables  730  may be bound together by taping  740 . Jacket extrusion  750  may extrude a jacket over the cable for mechanical support and manipulation by a user. 
     In this embodiment of the present invention, fiber-optic cables  730  may be held in place, that is, they are not twisted, as the cable is assembled. Power and data conductors  720  may be twisted around two fiber-optic cables  730 . This may prevent further losses in fiber-optic cables  730 . 
     Again, embodiments of the present invention may employ annealing to reduce losses in fiber-optic cables  730  due to their being twisted together, as shown in  FIG. 6 . In a specific embodiment of the present invention, this annealing is achieved during jacket extrusion  750 . 
     Specifically, the jacket may be a halogen-free material. Due to the properties of halogen-free materials, the jacket may be extruded at a slower rate than would otherwise be necessary for a material that includes halogens. Also, in various embodiments of the present invention, the temperature at jacket extrusion  750  may be higher than would otherwise be necessary. This slower rate and possibly higher temperature provides for annealing of fiber-optic cables  730 . 
     The losses incurred by twisting fiber-optic cables  730  may be increased if excessive tension is placed on fiber-optic cables  730  during construction of the cable. Accordingly, various embodiments of the present invention may reduce the tension placed on fiber-optic cables  730  during construction. A specific embodiment of the present invention may maintain no more tension on the fiber-optic cables  730  than is necessary for the construction of the cable. 
     The above description of embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Thus, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.