TWINAX ROUTING FOR TIGHT BEND RADIUS

Abstract

Twinax cable assemblies including cable lacing sections are described. An example cable assembly includes a first assembly end section, a second assembly end section, and a cable lacing section between the first and second assembly end sections, and a plurality of cable sets. Each cable set includes a plurality of cables. At least one cable set laces through at least one other cable set in the cable lacing section in one example. When the cable assembly bends substantially around a bend axis, conductors in the plurality of cable sets remain substantially aligned.

Claims

1. A cable assembly comprising: a first assembly end section, a second assembly end section, and a cable lacing section between the first and second assembly end sections; and a plurality of cable sets, each cable set comprising a plurality of cables, wherein: at least one cable set laces through at least one other cable set in the cable lacing section.

2. The cable assembly of claim 1, wherein at least one cable in the at least one cable set laces between at least two cables in the at least one other cable set in the cable lacing section.

3. The cable assembly of claim 1, wherein, when the cable assembly bends substantially around a bend axis, conductors in the plurality of cable sets remain substantially aligned.

4. The cable assembly of claim 1, further comprising: a first tie bar mounted on the first assembly end section; and a second tie bar mounted on the second assembly end section.

5. The cable assembly of claim 1, further comprising a binder configured to wrap around cable end sections of a plurality of cables of the at least one cable set.

6. The cable assembly of claim 5, wherein the binder is configured to substantially align conductors in the plurality of cables of the at least one cable set.

7. The cable assembly of claim 1, further comprising a binder configured to wrap around cable end sections of each of the plurality of cable sets.

8. The cable assembly of claim 1, wherein the plurality of cable sets are stacked in a first order at the first assembly end section and in a second order in reverse of the first order at the second assembly end section.

9. The cable assembly of claim 1, wherein: a first subset of plurality of cable sets connects to a top side of a first printed circuit board at the first assembly end section of the cable assembly; and a second subset of the plurality of cable sets connects to a bottom side of the first printed circuit board at the first assembly end section of the cable assembly.

10. The cable assembly of claim 9, wherein: the first subset of the plurality of cable sets lace through the second subset of the plurality of cable sets in the cable lacing section; the first subset of the plurality of cable sets connects to a bottom side of a second printed circuit board at the second assembly end section of the cable assembly; and the second subset of the plurality of cable sets connects to a top side of the second printed circuit board at the second assembly end section of the cable assembly.

11. The cable assembly of claim 1, wherein: at the first assembly end section, the plurality of cable sets are stacked in a first order; and at the second assembly end section, the plurality of cable sets are stacked in a second order different than the first order.

12. The cable assembly of claim 11, wherein: cables of a first cable set stacked at a first level at the first assembly end section lace through cables of a second cable set stacked at a second level at the first assembly end section; and the cables of the second cable set re-form at a third level different from the second level at the second assembly end section.

13. A cable assembly comprising: a first assembly end section comprising a first printed circuit board; a second assembly end section comprising a second printed circuit board; and a plurality of cable sets, each cable set comprising a plurality of cables, wherein: a cable set among the plurality of cable sets connects to a top side of the first printed circuit board at the first assembly end section of the cable assembly; and the cable set connects to a bottom side of the second printed circuit board at the second assembly end section of the cable assembly.

14. The cable assembly of claim 13, wherein: a second cable set among the plurality of cable sets connects to a bottom side of the first printed circuit board at the first assembly end section of the cable assembly; and the second cable set connects to a top side of the second printed circuit board at the second assembly end section of the cable assembly.

15. The cable assembly of claim 14, wherein, between the first assembly end section and the second assembly end section, the cable set laces through the second cable set.

16. The cable assembly of claim 13, wherein, when the cable assembly bends substantially around a bend axis, conductors in the plurality of cable sets remain substantially aligned.

17. The cable assembly of claim 13, further comprising a tie bar mounted on at least one of the first assembly end section or the second assembly end section.

18. The cable assembly of claim 13, further comprising a binder configured to wrap around cable end sections of a plurality of cables of the cable set.

19. A cable assembly comprising: a printed circuit board at an assembly end of the cable assembly; a plurality of cable sets, each cable set comprising a plurality of cables, wherein: a first cable set among the plurality of cable sets connects to a top side of the printed circuit board; and a second cable set among the plurality of cable sets connects to a bottom side of the printed circuit board; and the first cable set laces through the second cable set along a length of the cable assembly.

20. The cable assembly of claim 19, wherein, when the cable assembly bends substantially around a bend axis, conductors in the plurality of cable sets remain substantially aligned.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is an example embodiment of a twinax cable assembly configured for routing with tight bends without substantial degradation of signal integrity.

[0011] FIG. 2A is a top view of the twinax cable assembly of FIG. 1.

[0012] FIG. 2B is a side view of the twinax cable assembly of FIG. 1.

[0013] FIG. 3 is a top perspective view of the twinax cable assembly of FIG. 1 connected to connector printed circuit boards on opposite ends.

[0014] FIG. 4 is a close-up view of a connector printed circuit board at one end of the twinax cable assembly in FIG. 3.

[0015] FIG. 5 is a close-up view of the connector printed circuit board at an opposite end of the twinax cable assembly in FIG. 3 viewed from behind the cable connections to the connector printed circuit board.

[0016] FIG. 6 is a connector end of the twinax cable assembly with a connector shell covering the connector printed circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Example implementations of a twinax cable assembly described below address the possible degradation of signal integrity when twinax cable assemblies are bent, particularly near a connection to an electrical component. As is well-known in the art, twinax cables include a pair of conductors surrounded by an insulating material within a cable covering or sheath. Twinax cables are designed to benefit from the same structural characteristics that improve signal integrity in coaxial cables in which a signal conductor extends through the length of the cable. In particular, twinax cables may be surrounded as mentioned above with selected insulating materials including plastic such as polyethylene, foam, and other suitable dielectric materials having sufficient strength and flexibility to keep the conductors separated within the cable and to bend with the bending of the cable assembly.

[0018] One cause of the degradation of signal integrity at tight bends of twinax cable assemblies occurs when a cable bends such that the conductor pair in the cable is aligned perpendicular to the axis around which the cable is bent. In such a bend, one cable, the outside cable, is disposed further from a bending axis around which the cable is bent than the inside cable disposed closer to the bending axis. Such a bend has been shown to cause a lengthening in the timing of the signal traveling along the outside conductor relative to the timing of the signal traveling along the inside conductor. Such a lengthening in the timing between the differential signals degrades the signal integrity and can compromise the ability of the cable to perform within the signal integrity specifications typically specified for cable bends.

[0019] Cables are typically required to maintain adequate signal integrity around a bend having an effective bend radius that is greater than or equal to 5 the outer diameter of the cable. An effective bend radius of less than 5 the outer diameter of the cable is becoming the preferred specification for a bend radius. Twinax cable assemblies typically include multiple cables formed into a bundle. The twinax cables terminate at connectors that plug into electronic equipment, such as backplane connectors of servers and other computing equipment connectors. In example implementations described below, multiple twinax cables may be arranged as twinax cable sets with the cables disposed side by side with the conductor pairs aligned along a lateral direction. The twinax cables are typically terminated on a printed circuit board or other structure in a connector component such that the conductor pairs connect to a planar surface along the same lateral direction. Example implementations of twinax cable assemblies configured for routing with tight bends may be formed by disposing the twinax cable sets to form levels stacked at the cable ends and lacing, weaving, or routing the twinax cables through each other as the cable assembly extends to the other end. The lacing between end sections of the cable assembly permits the individual cables to maintain the conductor pairs aligned along a lateral direction in which the cables are disposed. In this manner, cables at tight bends have their conductors aligned along the lateral direction so that both conductors are equidistant to the bending axis thereby minimizing the negative effects of bending on signal integrity.

[0020] The end sections of the twinax cable assemblies in example implementations may be secured by a tie bar that distributes the cables before the cables connect to the connector component(s). The twinax cable sets may be arranged along a two-dimensional cross-section of the cable assembly. The conductor pairs align in a lateral direction corresponding to each twinax cable set and the multiple twinax cable sets are stacked such that the aligned conductor pairs are in parallel with one another. In example implementations, a binder, such as for example, a binding tape, may be used to keep the individual twinax cables in a twinax cable set disposed along a lateral direction with the conductor pairs aligned in the lateral direction.

[0021] FIG. 1 is an example embodiment of a twinax cable assembly 100 configured for routing with tight bends without substantial degradation of signal integrity. FIGS. 2A and 2B are top and side views, respectively, of the twinax cable assembly of FIG. 1. Referring to FIGS. 1 and 2A-2B, the example twinax cable assembly includes a first assembly end section 102, a second assembly end section 104 opposite the first assembly end section 102, and a cable assembly lacing section 106 between the first assembly end section 102 and the second assembly end section 104. The twinax cable assembly 100 includes a plurality of twinax cable sets 120, 122, 124, and 126 having a plurality of twinax cables 120a-d, 122a-d, 124a-d, and 126a-d, each comprising a pair of conductors 150a and 150b spaced apart in a lateral direction depicted for each twinax cable set 120, 122, 124, and 126 by parallel lines L1-L4, respectively. The conductor pairs 150a and 150b within each twinax cable are surrounded by an insulating material. Each of the twinax cable sets 120, 122, 124, 126 has opposite cable set end sections 202 and 204 at the first and second assembly end sections 102 and 104, a middle section 206 within the cable assembly lacing section 106 between the cable set end sections 202 and 204, and connector ends where each of the twinax cables in the twinax cable sets connect to terminal components 130 and 132 (shown schematically in FIGS. 2A and 2B and described in more detail as a printed circuit board in FIG. 3 below).

[0022] The example twinax cable assembly 100 in FIGS. 1 and 2A-2B includes a first tie bar 110 depicted in cross-section (shown as cross-section S-S in FIGS. 2A and 2B) to also depict a cross-section of the twinax cable assembly 100. The first tie bar 110 is mounted on the first assembly end section 102 and a second tie bar 112 mounted on the second assembly end section 104. Each tie bar 110, 112 is disposed between the cable assembly lacing section 106 and the terminal components 130, 132. Each tie bar 110, 112 is configured to orient the plurality of twinax cable sets 120, 122, 124, 126 such that each twinax cable set 120, 122, 124, 126 is stacked on each next twinax cable set 120, 122, 124, 126 substantially parallel to each other at the first and second assembly end sections 102, 104.

[0023] The twinax cable sets 120, 122, 124, and 126 are arranged so that at least one of the twinax cable sets 120, 122, 124, or 126 is laced with at least one of the other twinax cable sets 120, 122, 124, or 126 in the cable lacing section of the twinax cable assembly 100. As an example, twinax cable set 120 laces with twinax cable set 126 in the example implementation shown in FIGS. 1, 2A and 2B. The lacing of the twinax cable sets 120, 122, 124, 126 is conducted during assembly of the twinax cable assembly 100 so as to maintain the pairs of conductors 150 in each of the twinax cables 120a-d, 122a-d, 124a-d, and 126a-d substantially aligned in the lateral direction such that when the twinax cable assembly 100 bends (at bend B around axis A in FIG. 1) substantially around a bend axis A extending in the lateral direction, the pairs of conductors in each of the twinax cables remain substantially aligned in the lateral direction. The alignment of the conductor pairs 150a and 150b is shown as remaining in the lateral direction as the twinax cables 126d and 124d bend in image I in FIG. 1. The lacing of the twinax cables in the cable assembly lacing section 106 of the twinax cable assembly 100 helps ensure that the conductor pairs 150 are maintained in alignment such that each conductor in a pair is equidistant to the bend axis A.

[0024] It is noted that the lacing of the twinax cable sets 120, 122, 124, and 126 may be determined by how the cables terminate on opposite ends of the cable assembly 100. As noted above, the cable sets 120, 122, 124, and 126 are stacked at the opposite assembly end section 102, 104. The twinax cables in each twinax cable set 120, 122, 124, and 126 may terminate at the terminal components 130, 132 in a manner that changes the stacking order of the twinax cable sets 120, 122, 124, 126. The lacing of the cables with cables from different cable sets may be configured to ensure that each cable terminates at each terminal component 130, 132 such that the signals conducted in the cables are communicated as intended. The stacking of the cable sets is described further with reference to FIGS. 3-5.

[0025] The alignment of the conductor pairs 150a and 150b in each twinax cable 120a-d, 122a-d, 124a-d, and 126a-d may be further maintained by applying a binder 108 to each twinax cable set 120, 122, 124, 126. The binder 108 may be wrapped around the cable set end sections 202, 204 of each of the plurality of twinax cable sets between the cable assembly lacing section 106 and the connector ends of each twinax cable set 120, 122, 124, 126. Each binder 108 is configured to further ensure that the twinax cable sets 120, 122, 124, 126 bend substantially around the bend axis A extending in the lateral direction with all of the conductor pairs substantially aligned laterally. The binders 108 may be any suitable tape or strap-like material, such as, for example, duct tape, packing tape, or a similar alternative.

[0026] The twinax cables in the twinax cable assembly 100 may be any suitable twinax cable having a pair of conductors 150. The twinax cables may be surrounded by a dielectric material to keep the conductors apart while providing some flexibility to permit bending. The conductor pairs and insulation may also be surrounded by a shielding material, such as a metal foil or braided metal in a film-like arrangement. In some embodiments, the twinax cables include a pair of ground wires disposed on opposite sides of the pair of conductors as described in more detail below with reference to FIG. 5. The pair of conductors 150 and pair of ground wires may be spaced apart and aligned in the lateral direction. In some examples, the ground, or drain, wires may not be aligned with the conductor pairs 150, and in some cases, a cable shield, or foil layer, may be connected to function as a drain.

[0027] FIG. 3 is a top perspective view of the twinax cable assembly 100 of FIG. 1 connected to connector printed circuit boards 130 and 132 on opposite ends of the twinax cable assembly 100. FIG. 4 is a close-up view of a connector printed circuit board 130 at one assembly end section 102 of the twinax cable assembly 100 in FIG. 3. FIG. 5 is a close-up view of the connector printed circuit board 132 at an opposite assembly end section 104 of the twinax cable assembly 100 in FIG. 3 viewed from behind the cable connections to the connector printed circuit board.

[0028] Referring to FIGS. 3-5, the twinax cable assembly 100 may be any suitable length and may typically be covered by a sheath or a suitable material that keeps the twinax cables encased for convenience in handling. The printed circuit boards 130 and 132 may be enclosed in connector shell components as described below with reference to FIG. 6. The twinax cable sets 120, 122, 124, and 126 may be stacked as shown in FIG. 3 in a first order 120-122-124-126 at the first cable set end section 202 to connect to the first printed circuit board 130. As the cable assembly 100 extends to the opposite assembly end section 104, through the lacing section 106, the stacking order may change. As shown in the figures, the stacking order at the second cable set end section 204 is 124-126-120-122 from top to bottom.

[0029] The stacking order may be determined by the type of signal being conducted by the conductor pairs. For example, a signal may be transmitted on one of the twinax cables at the first end. The conductor pair in the twinax cable would be connected to a transmit terminal on the printed circuit board 130 at the first cable set end section 202 of the twinax cable and to a receive terminal on the printed circuit board 132 at the second end 204 of the twinax cable. It is noted that while the cable sets 120, 122, 124, 126 are formed so that the same twinax cables form each twinax cable set 120, 122, 124, 126 at both ends, it is possible in some embodiments for the twinax cables to cross within the lacing section to different twinax cable sets at the opposite cable set end sections 202, 204. The twinax cables are maintained in the same twinax cable sets from one cable end section 202 to the other cable set end section 204 for purposes of clarity in describing the example implementations. Example implementations of the twinax cable assembly having a lacing section 106 advantageously use the lacing to maintain the lateral alignment of the conductor pairs in each twinax cable regardless of how the twinax cables are routed between the first cable set end section 202 and the second cable set end section 204 of the twinax cable assembly 100.

[0030] The lacing section 106 of the twinax cable assembly 100 includes one or more of the twinax cables in each twinax cable set laced through the other twinax cable sets. The twinax cables may be separated individually and laced through the twinax cable sets, or in pairs of twinax cables, or in other groups. The twinax cables may also be laced individually or in groups at random. The example cable assembly 100 shown in FIG. 3 laces the twinax cables in pairs. That is, pairs of twinax cables in each twinax cable set are separated and laced through the other twinax cable sets.

[0031] The stacking order of the twinax cable sets may be changed through the lacing section 106 individually such that the twinax cable sets are in a different order at the opposite cable set end sections 202, 204. The twinax cable assembly 100 in FIG. 3 depicts the twinax cable sets paired so that the stacking order of the pairs of twinax cable sets is reversed at opposite assembly end sections 102, 104 of the twinax cable assembly 100.

[0032] The twinax cables 120a-d, 122a-d, 124a-d, 126a-d connect to the first printed circuit board 130 at the first assembly end section 102 of the cable assembly 100. Each end of the twinax cables may be fixed to the printed circuit board 130 by a bracket 145. A first bracket 145a secures the ends of twinax cable 120a-d. A second bracket 145b secures the ends of twinax cable 122a-d. A third bracket 145c secures the ends of twinax cable 124a-d. A fourth bracket 145d secures the ends of twinax cable 126a-d. The conductor pairs 150 in each twinax cable 120a-d, 122a-d, 124a-d, 126a-d may be soldered, or otherwise functionally secured to the surface of the printed circuit board 130 to electrically connect to a suitable trace etched on the printed circuit board 130. The connections of the conductor pairs 150 may be connected to the printed circuit board 130 in rows according to the stacking order of the twinax cable sets 120, 122, 124, 126.

[0033] The twinax cables 120a-d, 122a-d, 124a-d, 126a-d connect to the second printed circuit board 132 at the second assembly end section 104 of the cable assembly 100. Each end of the twinax cables may be fixed to the printed circuit board 132 by a bracket 145 similar to that of the brackets 145a-d in FIG. 4. A first bracket 145e secures the ends of twinax cable 124a-d. A second bracket 145f secures the ends of twinax cable 126a-d. A third bracket 145g secures the ends of twinax cable 120a-d. A fourth bracket 145h secures the ends of twinax cable 122a-d. The conductor pairs 150 in each twinax cable 120a-d, 122a-d, 124a-d, 126a-d may be soldered, or otherwise functionally secured to the surface of the printed circuit board 130 to electrically connect to a suitable trace etched on the printed circuit board 132. The connections of the conductor pairs 150 may be connected to the printed circuit board 132 in rows according to the stacking order of the twinax cable sets 120, 122, 124, 126.

[0034] It is noted that the example twinax cable assembly 100 described with reference to FIGS. 3-5 include terminal connections to printed circuit boards 130, 132. It is noted that other example twinax cable assembly 100 implementations may terminate at different structures. Printed circuit boards 130, 132 comprise but one type of terminal structure illustrated here for purposes of providing a clear description. Other suitable connection structures may be used as well.

[0035] FIG. 6 is a connector 200 at one assembly end section 102 of the twinax cable assembly 100. The connector 200 has a connector shell 210 covering the connector printed circuit board 130. The twinax cable assembly 100 is shown covered with a cable cover or sheath 220. The connector 200 may include a suitable mating structure 230 that mates with a corresponding structure on a receiving connector. The receiving connector may be a part of an electronic component configured to receive the connector 200 and the signals communicated on the twinax cable assembly 100.

[0036] It is noted that the example implementations of the twinax cable sets 120, 122, 124, 126 described in this disclosure each include four twinax cables. However, other example implementations may include any other suitable number of twinax cables. In addition, four twinax cable sets 120, 122, 124, 126 form the example twinax cable assemblies 100 described herein, however, other example implementations may include any suitable number of twinax cable sets. In addition, example implementations may include a first plurality of twinax cable sets having one number of twinax cables, and through lacing, come together at the other end with a second plurality of cable sets with a different number of twinax cables in each twinax cable set.

[0037] The disclosure provided herein describes features in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure.