JP2014154490A - Cable for differential signal transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable for differential signal transmission which suppresses between-PN skew and facilitates multidirectional bending.SOLUTION: A cable for differential signal transmission includes at least two conductors 2 and an insulator 3 coating the conductors 2 collectively and is formed in such a way that its cross section is rotated gradually along the longitudinal direction, with the center of the arrangement direction of the conductors 2 and the center of the direction perpendicular to the arrangement direction of the conductors 2 as the rotation axes.

Description

  The present invention relates to a differential signal transmission cable.

  As a conventional differential signal transmission cable, a twisted pair cable in which two insulated wires are twisted together is known.

  Twisted pair cables have the advantage of being flexible and easy to bend, but due to the difference in dielectric constant between the insulators of the two insulated wires, the transmission time difference between the signals transmitted through the two conductors, that is, the pairwise skew (PN) There was a problem that the signal was deteriorated.

  As a differential signal transmission cable that solves such a problem, a differential signal transmission cable 31 having a two-core package structure as shown in FIG. 3 is known.

  The differential signal transmission cable 31 of FIG. 3 is configured by covering two conductors 32 arranged in parallel with an insulator 33 and providing an outer conductor 34 on the outer periphery thereof. The cross-sectional shape of the differential signal transmission cable 31 is an oval shape (a shape in which two parallel straight line ends are connected by a semicircular arc), or a combination of a plurality of curves having different curvature radii. It is thick in the direction of arrangement of the conductors 32 and thin in the direction perpendicular to the direction of arrangement of the conductors 32.

  In addition, there exists patent documents 1-3 as prior art document information relevant to invention of this application.

JP 2011-86458 A JP 2012-169251 A JP 2011-96574 A

  However, the above-described differential signal transmission cable 31 is not particularly problematic when bent in the direction perpendicular to the arrangement direction of the conductors 32, but is difficult to bend mechanically when bent in the arrangement direction of the conductors 32. There is a problem that the degree of freedom is low.

  Further, when the differential signal transmission cable 31 is bent in the direction in which the conductors 32 are arranged, there is a problem that a pairwise skew occurs because a difference in length occurs between the outer peripheral side and the inner peripheral side of the bending.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a differential signal transmission cable that can suppress a skew between pairs and can be easily bent in multiple directions.

  The present invention has been devised to achieve the above object, and has at least two conductors and an insulator that collectively covers the periphery of the two conductors. The differential signal transmission cable is formed so that its cross-sectional shape gradually rotates along the longitudinal direction with the direction and the center in the direction perpendicular to the arrangement direction of the conductors as the rotation axis.

  The insulator has a cross-sectional shape that is axisymmetric with respect to a center in the arrangement direction of the conductors, and is axisymmetric with respect to a center in a direction perpendicular to the arrangement direction of the conductors. It may be formed so as to be thick in the arrangement direction and thin in the direction perpendicular to the arrangement direction of the conductors.

  The rotation period of the cross-sectional shape may be constant.

  The direction of rotation of the cross-sectional shape may be one direction.

  The rotational direction of the cross-sectional shape may be reversed at regular intervals.

  ADVANTAGE OF THE INVENTION According to this invention, the cable for differential signal transmission which can suppress a skew between pairs and can be bent easily in many directions can be provided.

It is a figure which shows the cable for differential signal transmission which concerns on one embodiment of this invention, (a) is a perspective view, (b) is a top view and a cross-sectional view of each part. FIG. 2 is a cross-sectional view of a multicore cable using the differential signal transmission cable of FIG. 1. It is a figure which shows the conventional cable for differential signal transmission, (a) is a perspective view, (b) is a cross-sectional view.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1A and 1B are diagrams showing a differential signal transmission cable according to the present embodiment. FIG. 1A is a perspective view, and FIG. 1B is a plan view and a cross-sectional view of each part.

  As shown in FIGS. 1 (a) and 1 (b), a differential signal transmission cable 1 includes two conductors 2, an insulator 3 that collectively covers the periphery of the two conductors 2, and an insulator. 3 and an outer conductor 4 provided on the outer periphery of 3.

  As the conductor 2, a good electrical conductor such as copper may be used. As the insulator 3, either a foamed insulating resin or a non-foamed insulating resin may be used. As the insulating resin used for the insulator 3, for example, PE ( Polyethylene). The outer conductor 4 is formed by, for example, winding a resin tape (metal tape) having a metal layer on one surface around the outer periphery of an insulator.

  The insulator 3 has an elliptical cross section (a shape in which two parallel straight line ends are connected by a semicircular arc), and is lined with respect to the center of the conductor 2 in the arrangement direction. In addition to being formed symmetrically, the conductor 2 is formed in line symmetry with respect to the center in the direction perpendicular to the arrangement direction of the conductor 2, and further, with respect to the center in the arrangement direction of the conductor 2 It is formed point-symmetrically. The insulator 3 is formed to be thick in the arrangement direction of the conductors 2 and thin in the direction perpendicular to the arrangement direction of the conductors 2. The insulator 3 may have a cross-sectional shape that is a combination of a plurality of curves having different curvature radii. An example of a shape formed by combining a plurality of curves having different radii of curvature includes an ellipse, a pair of elliptical arcs (including arcs) facing the arrangement direction of the conductors 2 and a pair facing the vertical direction of the arrangement direction of the conductors 2 There is a shape that combines an elliptical arc (including an arc).

  In the differential signal transmission cable 1 according to the present embodiment, the cross-sectional shape gradually rotates along the longitudinal direction with the arrangement direction of the conductors 2 and the center in the direction perpendicular to the arrangement direction of the conductors 2 as the rotation axis. It is formed to do.

  That is, it can be said that the differential signal transmission cable 1 is obtained by replacing the insulators of the two insulated wires in the twisted pair cable with the insulator 3 of the cover and providing the outer conductor 4 around the insulator. The conductor 2 is in a twisted state like the twisted pair cable. The outer conductor 4 can be omitted.

  When the differential signal transmission cable 1 is bent in a certain direction, bending occurs in a portion that is likely to bend in the bending direction, that is, in a portion where the cross section in the bending direction is thin. At this time, if the rotational period of the cross-sectional shape in the differential signal transmission cable 1 is formed sufficiently short, the number of bending portions increases and the bending angle per one portion where bending occurs decreases, resulting in smoothness. Bending can be realized.

  The rotation period of the cross-sectional shape of the differential signal transmission cable 1 is desirably constant from the viewpoint of making the cable characteristics uniform in the longitudinal direction. However, the rotation period of the cross-sectional shape of the differential signal transmission cable 1 is not limited to a fixed value, and for example, the rotation period can be shortened only at a place where bending is applied. Furthermore, it is possible to adopt a configuration in which the cross-sectional shape is rotated only in a place where bending is applied, and a straight configuration in which the cross-sectional shape is not rotated in places where bending is not applied.

  Further, the rotational direction of the cross-sectional shape of the differential signal transmission cable 1 is preferably one direction from the viewpoint of making the cable characteristics uniform in the longitudinal direction. However, the rotational direction of the cross-sectional shape of the differential signal transmission cable 1 is not limited to one direction. For example, the rotational direction of the cross-sectional shape of the differential signal transmission cable 1 is reversed at regular intervals. It is also possible to configure (that is, a configuration in which the cross-sectional shape is gradually rotated only in a predetermined section in the longitudinal direction).

  When the differential signal transmission cable 1 is manufactured, for example, the cross-sectional shape can be rotated by rotating the take-up reel when the insulator 3 is extrusion-coated. Note that the differential signal transmission cable 1 can also be manufactured by rotating the extrusion device itself when the insulator 3 is extrusion coated. Further, the differential signal transmission cable 1 can be manufactured by winding the take-up reel once in a state in which the cross-sectional shape is not rotated, and then rotating the insulator while heating it and rewinding it to another take-up reel. Is possible.

  As shown in FIG. 2, a plurality of differential signal transmission cables 1 can be used together as a multicore cable 21.

  The multicore cable 21 of FIG. 2 accommodates the differential signal transmission cable 1 in each of the four spaces partitioned by the cross-shaped interposition 22, and is provided with a shield conductor 23 and a jacket 24 sequentially so as to cover them collectively. Is.

  The specific structure of the multi-core cable 21 is not limited to this. For example, the outer conductor 4 of each differential signal transmission cable 1 is omitted, and the shield conductor 23 is used as a common outer conductor. It may be.

  As described above, the differential signal transmission cable 1 according to the present embodiment includes at least the two conductors 2 and the insulator 3 that collectively covers the periphery of the two conductors 2. The cross-sectional shape is formed so as to gradually rotate along the longitudinal direction with the arrangement direction of the conductors 2 and the center in the direction perpendicular to the arrangement direction of the conductors 2 as the rotation axis.

  By being configured in this way, when bending in a certain direction, bending occurs naturally in a portion that is easily bent in the bending direction, that is, in a portion where the cross section in the bending direction is thin, and in which direction it is flexible. In addition, the differential signal transmission cable 1 that can be easily bent can be realized.

  Moreover, since the differential signal transmission cable 1 adopts a two-core collective structure, the skew between the pair due to the difference in dielectric constant between the insulators of two insulated wires, such as a twisted pair cable used in the past, is suppressed. can do. Furthermore, since the cross-sectional shape is not forced to be bent in the thick direction (the direction in which the conductors 2 are arranged), it becomes possible to suppress the pair-to-pair skew caused by the physical length difference between the inner periphery and the outer periphery of the bend. The differential signal transmission cable 1 with little deterioration in skew characteristics even when bent in the direction can be realized.

  That is, according to the present invention, it is possible to realize the differential signal transmission cable 1 that can suppress the skew between the pairs and can be easily bent in multiple directions.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

1 Cable for differential signal transmission 2 Conductor 3 Insulator 4 Outer conductor

Claims (5)

At least two conductors,
An insulator that collectively covers the periphery of the two conductors,
The differential signal is characterized in that the cross-sectional shape is formed so as to gradually rotate along the longitudinal direction with the arrangement direction of the conductors and the center in the direction perpendicular to the arrangement direction of the conductors as a rotation axis. Transmission cable. The insulator has a cross-sectional shape that is axisymmetric with respect to a center in the arrangement direction of the conductors, and is axisymmetric with respect to a center in a direction perpendicular to the arrangement direction of the conductors. The differential signal transmission cable according to claim 1, wherein the cable is formed so as to be thick in an arrangement direction and thin in a direction perpendicular to the arrangement direction of the conductors. The differential signal transmission cable according to claim 1, wherein a rotation period of the cross-sectional shape is constant. The cable for differential signal transmission according to any one of claims 1 to 3, wherein the rotational direction of the cross-sectional shape is one direction. The cable for differential signal transmission according to any one of claims 1 to 3, wherein the rotation direction of the cross-sectional shape is reversed at constant intervals.