Shielded cable for high-speed differential communication

Abstract

The present invention achieves a reduction in height.　This shielded cable (10) for high-speed differential communication is used as a transmission path of a high-speed differential communication circuit, and comprises: a plurality of shielded wires (11) in which conductors (12) are surrounded by shield layers (14); and sheets (20) that hold the plurality of shielded wires (11) in a parallel state. When the direction intersecting the parallel direction of the plurality of shielded wires (11) is defined as the height direction, the overall height of the shielded cable (10) is the sum of the outer diameter of the shielded wires (11) and the thickness dimension of the sheets (20). Since there is no dead space above and below the shielded wires (11), it is possible to reduce the height of the shielded wires (11).

Description

Shielded Cable for High-Speed Differential Communication

[0001] The present disclosure relates to a shielded cable for high-speed differential communication.

[0002] Patent Document 1 discloses a composite cable in which a first shielded electric wire formed by covering a first signal wire with a first shield member and a second shielded electric wire formed by covering a second signal wire with a second shield member are collectively covered with a cylindrical sheath. This composite cable is used as a transmission line for high-speed differential communication.

[0003] Publication No. 2016 / 151753

[0004] When the above composite cable is arranged such that two shielded electric wires are arranged side by side horizontally, the diameter of the sheath, that is, the height of the sheath, becomes larger than the height dimension of the shielded electric wire. In the sheath, the space above the shielded electric wire and the space below the shielded electric wire are dead spaces. Therefore, this composite cable has a problem of being unnecessarily enlarged in the height direction intersecting the parallel direction of the shielded electric wires.

[0005] The shielded cable for high-speed differential communication of the present disclosure has been completed based on the above circumstances, and aims to achieve low-profile.

[0006] The shielded cable for high-speed differential communication of the present disclosure is a shielded cable used as a transmission line for a high-speed differential communication circuit, and includes a plurality of shielded electric wires in which conductors are surrounded by shield layers, and a sheet that holds the plurality of shielded electric wires in a parallel state.

[0007] According to the present disclosure, low-profile can be achieved.

[0008] FIG. 1 is a perspective view of the shielded cable of Example 1. FIG. 2 is a front view of the shielded cable. FIG. 3 is a front view of a comparative cable. FIG. 4 is a graph showing the shielding performance of the shielded cable of Example 1 and the comparative cable.

[0009] [Description of Embodiments of the Disclosure] First, embodiments of the disclosure will be listed and described. Any combination of the following embodiments, insofar as they do not contradict each other, is also included as a form for carrying out the invention.

[0010] The shielded cable for high-speed differential communication of this disclosure comprises: (1) a shielded cable used as a transmission path for a high-speed differential communication circuit, comprising: a plurality of shielded wires in which conductors are surrounded by a shielding layer; and a sheet that holds the plurality of shielded wires in a parallel state. With this configuration, when the direction intersecting the parallel direction of the plurality of shielded wires is defined as the height direction, the overall height of the shielded cable is the sum of the outer diameter of the shielded wires and the thickness of the sheet. Since there is no dead space above or below the shielded wires, a low profile can be achieved.

[0011] (2) In (1), it is preferable that the pair of sheets are arranged so as to sandwich the plurality of shield wires in a direction that intersects the parallel direction. This configuration is excellent in integrating the plurality of shield wires.

[0012] (3) In (2), it is preferable that the pair of sheets cover the entirety of the plurality of shielded wires. This configuration protects the shielded wires from interference by foreign objects.

[0013] (4) In (1) to (3), it is preferable that the sheet includes an insulating layer made of an insulating material. With this configuration, it is possible to keep the shielded wire in an insulated state from external conductive members.

[0014] (5) In (4), it is preferable that the sheet comprises a base material made of an insulating material and a conductive layer laminated on the base material. This configuration makes it possible to suppress the influence of external noise on the shielded wire.

[0015] In (6) and (5), it is preferable that the outermost layer of the shielded wire is made up of the shield layer, and that the conductive layer is in contact with the shield layer of the plurality of shielded wires. With this configuration, the shield layers of the plurality of shielded wires are kept at the same potential by conducting electricity with each other, so the shielding characteristics are improved.

[0016] [Details of Embodiments of the Disclosure] [Example 1] A shielded cable 10 of Example 1 embodying the present disclosure will be described with reference to Figures 1 to 4. The present invention is not limited to these examples and is shown in the claims, including all modifications within the meaning and scope of the equivalents of the claims. In this Example 1, the vertical direction and the height direction are used synonymously. The left-right direction and the width direction are used synonymously.

[0017] The shielded cable 10 of this embodiment 1 is a shielded cable 10 for high-speed differential communication used as a transmission line for a high-speed differential communication circuit. The shielded cable 10 is composed of a plurality of shield wires 11 and a pair of upper and lower sheets 20.

[0018] The shielded wire 11 is composed of one conductor 12, one insulator 13, and one shielding layer 14. The conductor 12 is made of, for example, a conductive stranded wire. The insulator 13 is made of a material having electrical insulating properties, such as synthetic resin. The insulator 13 concentrically surrounds the conductor 12 around its entire circumference. When viewed in an axial direction parallel to the axis of the shielded wire 11, the shape (outer shape) of the outer surface of the insulator 13 is circular.

[0019] The shield layer 14 is a cylindrical member that concentrically surrounds the conductor 12 and the insulator 13. The shield layer 14 is formed by wrapping a single metal foil around the outer surface of the insulator 13. The shielded wire 11 does not have a sheath. Therefore, the shield layer 14 is exposed all around the outer surface of the shielded wire 11. In other words, the outermost layer of the shielded wire 11 is composed solely of the shield layer 14.

[0020] The sheet 20 is a two-layer member consisting of a thin plate-like or thin film-like base material 21 and a conductive layer 22 laminated on the surface of the base material 21. The pair of sheets 20 are arranged symmetrically, with the conductive layers 22 facing each other. On the upper surface of the lower sheet 20, a plurality of shield wires 11 are arranged in parallel in the width direction (left-right direction) perpendicular to the axis of the shield wires 11. Adjacent shield wires 11 in the width direction are arranged with their shield layers 14 in contact with each other. The conductive layer 22 on the upper surface of the sheet 20 and the shield layer 14 of the shield wires 11 are fixed in direct contact by heat fusion. Adjacent shield wires 11 in the width direction may or may not be fixed to each other.

[0021] After the shield wires 11 are fixed to the lower sheet 20, another sheet 20 is placed on top of the multiple shield wires 11. The upper sheet 20 is positioned so that the conductive layer 22 on its lower surface is in contact with the shield layer 14 of the shield wires 11. The conductive layer 22 of the upper sheet 20 and the shield layer 14 of the shield wires 11 are fixed in direct contact by heat fusion. As a result, the multiple shield wires 11 are sandwiched between the upper and lower pair of sheets 20 and fixed to both sheets 20, thereby positioning them in a parallel state. The shield layers 14 of the multiple shield wires 11 arranged in parallel are maintained at the same potential through the upper and lower conductive layers 22. With this, the manufacture of the shield cable 10 is completed.

[0022] Multiple shielded wires 11 are used as a transmission path for high-speed differential communication, with any two wires considered as a pair of Dual-Coax wires. A pair of Dual-Coax wires may be composed of two adjacent shielded wires 11, or two non-adjacent shielded wires 11.

[0023] Figure 3 shows a comparison cable 30 for comparison with the shielded cable 10 of this embodiment 1 in terms of shielding performance. The comparison cable 30 is a cable that has been modified from a typical STP (Shielded Twisted Pair Cable) which has a two-layer shielding structure consisting of metal foil and braided wire, by removing the sheath and braided wire. In other words, the comparison cable 30 is a cable in which one twisted pair wire 31 is surrounded by metal foil 35. The twisted pair wire 31 is constructed by twisting together two insulated wires 32, each in which a conductor 33 is surrounded by an insulator 34, in a spiral shape.

[0024] Figure 4 shows a graph of the characteristic value As (Screening Attenuation characteristic) indicating the shielding performance of the shielded cable 10 of this embodiment 1 and the comparison cable 30. In the graph, curve La represents the As value of the shielded cable 10 of this embodiment 1, and curve Lb represents the As value of the comparison cable 30. The graph also shows the OABR standard value Lc. The OABR standard value Lc is the As standard value for cables described in the communication standard for automotive Ethernet, namely OPEN ALLIANCE 1G (Channel and Component Requirements for 1000BASE-T1 Link Segment Type A (STP)). Note that OABR is a registered trademark.

[0025] As shown in the graph, the As value Lb of the comparison cable 30, in which the braided wire was removed and the two conductors 33 were collectively surrounded by metal foil 35, deteriorated significantly and did not satisfy the OABR standard value Lc. In contrast, the As value La of the shielded cable 10 of this embodiment 1, in which the conductors 12 of each shielded wire 11 are individually covered by the shielding layer 14, clears the OABR standard value Lc. Therefore, the shielded cable 10 of this embodiment 1 exhibits superior shielding performance compared to the comparison cable 30.

[0026] The shielded cable 10 of this embodiment 1 comprises a plurality of shielded wires 11, each in which a conductor 12 is surrounded by a shielding layer 14, and a sheet 20 that holds the plurality of shielded wires 11 in parallel. With this configuration, the plurality of shielded wires 11 can be held in a parallel state by fixing them to the sheet 20.

[0027] In the case of a cable (not shown) formed by housing two shielded wires (not shown) arranged side by side in the width direction within a cylindrical sheath (not shown), dead space is created above and below the shielded wires within the sheath. In contrast, the height dimension of the shielded cable 10 in this embodiment 1 (the direction intersecting the parallel direction of the multiple shielded wires 11) is the sum of the outer diameter of the shielded wires 11 and the thickness of the pair of sheets 20. Since the shielded cable 10 in this embodiment 1 does not have dead space above or below the shielded wires 11, a low profile can be achieved.

[0028] The pair of sheets 20 are arranged to sandwich the multiple shield wires 11 in a parallel direction and in an intersecting vertical direction. This configuration allows for more secure integration of the multiple shield wires 11 compared to a structure where only one sheet 20 holds the multiple shield wires 11. Furthermore, since the pair of sheets 20 completely cover the multiple shield wires 11, the shield cable 10 of this embodiment 1 can protect the shield wires 11 from interference by foreign objects.

[0029] The sheet 20 includes a base material 21 which serves as an insulating layer made of an insulating material. With this configuration, the shielded wire 11 can be kept in an insulated state from external conductive members (not shown). Furthermore, since the base material 21 is made of synthetic resin, the shielded cable 10 of this embodiment 1 can be made lighter compared to a case where the entire sheet 20 including the base material 21 is made of metal.

[0030] The sheet 20 has a base material 21 made of an insulating material and a conductive layer 22 laminated on the base material 21. With this configuration, the influence of external noise on the shield wire 11 can be suppressed. The outermost layer of the shield wire 11 is made of a shield layer 14. The conductive layer 22 is in contact with the shield layers 14 of multiple shield wires 11. With this configuration, the shield layers 14 of multiple shield wires 11 are kept at the same potential by conducting electricity with each other, so the shielding characteristics are improved.

[0031] [Other Embodiments] The present invention is not limited to the embodiments described above and in the drawings, but is shown in the claims. The present invention includes the meaning of equivalences to the claims and all modifications within the claims, and also includes the following embodiments. The conductor of the shielded wire is not limited to stranded wire, but may be single-core wire. The shield layer of the shielded wire may consist only of braided wire, or it may be in the form of metal foil and braided wire coaxially laminated. The cross-sectional shape of the sheet is not limited to a straight line, but may be a corrugated shape that matches the outer shape of the shielded wire. There may be only one sheet. The conductive layer of the sheet and the shield layer of the shielded wire may be fixed not only by heat fusion, but also by using a conductive adhesive. Multiple sheets may be arranged at intervals in the longitudinal direction of the shielded wire so that a part of the shielded wire is exposed. The sheet may be a single-layer structure. In this case, the material of the sheet may be a conductive material such as metal, or an insulating material such as synthetic resin. The conductive layer may be arranged so as not to be in contact with the shielded wire (shield layer).

[0032] 10...Shielded cable 11...Shielded wire 12...Conductor 13...Insulator 14...Shielding layer 20...Sheet 21...Base material (insulating layer) 22...Conductive layer 30...Comparison cable 31...Twisted pair wire 32...Insulated wire 33...Conductor 34...Insulator 35...Metal foil La...As value of shielded cable of Example 1 Lb...As value of comparison cable Lc...OABR standard value

Claims

1. A shielded cable for use as a transmission line in a high-speed differential communication circuit, comprising: a plurality of shielded wires in which conductors are surrounded by a shielding layer; and a sheet that holds the plurality of shielded wires in a parallel arrangement.

2. The shielded cable for high-speed differential communication according to claim 1, wherein a pair of the sheets are arranged to sandwich the plurality of shielded wires in a direction that intersects the parallel direction.

3. The shielded cable for high-speed differential communication according to claim 2, wherein the pair of sheets are configured to cover the entirety of the plurality of shielded wires.

4. The shielded cable for high-speed differential communication according to any one of claims 1 to 3, wherein the sheet comprises an insulating layer made of an insulating material.

5. The shielded cable for high-speed differential communication according to claim 4, wherein the sheet comprises a base material made of an insulating material and a conductive layer laminated on the base material.

6. The shielded cable for high-speed differential communication according to claim 5, wherein the outermost layer of the shielded wire is composed of the shield layer, and the conductive layer is in contact with the shield layer of the plurality of shielded wires.

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