JP2009199829A - Transmission cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission cable that suppresses the generation of capacitance in an external conductor layer without degrading flexibility of the external conductor layer. <P>SOLUTION: The transmission cable is provided with the external conductor layer formed by spirally winding in the outside of one or more signal wires comprising a center conductor and an insulating cover layer formed in the outer periphery of the center conductor. The external conductor layer is formed with a conductive resin layer 4a consisting of a conductive resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission cable such as a differential signal transmission cable and a coaxial cable.

  Conventionally, a transmission cable for LVDS (Low Voltage Differential Signal) (hereinafter referred to as “differential signal transmission”) is used as a cable for high-speed data communication used for internal wiring of various devices such as various communication devices and computers. Cables) and coaxial cables are known.

  Around the signal line used in such a transmission cable, a tape is vertically attached or spirally wound as an outer conductor layer for suppressing noise. In addition to a metal foil tape such as a copper tape, the tape has a conductive metal layer 14b such as aluminum, copper, silver or gold on the surface of a plastic layer 14a such as a polyester film or a polyimide film as shown in FIG. (For example, refer patent document 1 and patent document 2). As an example of a tape provided with the plastic layer 14a and the metal layer 14b, an aluminum mylar tape (AlPET tape) is mentioned, for example. Some tapes have an adhesive attached thereto.

Generally, in the vertical attachment, the insulating coating layer and the tape are poorly adhered, and the position of the insulating coating layer is not stable, so that the transmission characteristics are not stable. Furthermore, it is known that the flexibility is poor in the vertical attachment.
Japanese Patent Application No. 7-205036 JP 2006-286480 A

  However, there are some problems with spiral wound tapes. FIG. 7 is a perspective view of a differential signal transmission cable having two signal lines (reference numerals omitted) composed of the central conductor 11 and the insulating coating layer 12 and one drain line 13. When the tape (outer conductor layer 14) shown in FIG. 6 is spirally wound outside the two signal lines and the drain line 13 so that the plastic layer 14a is on the inner side, a portion A in the figure which is an overlapping portion of the tape. Then, the plastic layer 14a enters between the metal layers 14b. For this reason, a capacitance is generated in the overlapping portion of the tapes, and the attenuation amount suddenly drops at a specific frequency. Further, if a metal foil tape is used, no capacitance is generated. However, since the metal foil tape does not stretch, the tape is easily cut when the tape is wound, and the tape becomes weak against bending.

  In view of the above problems, an object of the present invention is to provide a transmission cable that suppresses the occurrence of capacitance in the outer conductor layer without impairing the flexibility of the outer conductor layer.

  In order to achieve the above object, an invention according to claim 1 is directed to an external device formed by spirally winding outside of one or more signal lines comprising a central conductor and an insulating coating layer provided on the outer periphery of the central conductor. A gist of the present invention is a transmission cable including a conductor layer, wherein the outer conductor layer is a transmission cable including a conductive resin layer made of a conductive resin.

  According to the transmission cable according to this feature, it is possible to suppress the occurrence of capacitance in the outer conductor layer without impairing the flexibility of the outer conductor layer.

  According to a second aspect of the present invention, in the transmission cable of the first aspect, the outer conductor layer is composed of a conductive resin layer and a metal layer.

  According to this transmission cable, it is possible to further suppress the occurrence of capacitance in the outer conductor layer.

  ADVANTAGE OF THE INVENTION According to this invention, the transmission cable which suppresses that a capacitance generate | occur | produces in an external conductor layer without impairing the flexibility of an external conductor layer can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Transmission cable structure)
As shown in FIG. 1, the transmission cable according to the present embodiment is spirally disposed outside one or more signal lines (reference numerals omitted) including a central conductor 1 and an insulating coating layer 2 provided on the outer periphery of the central conductor 1. An outer conductor layer 4 formed by winding is provided. FIG. 1 shows a cable (so-called Twinax) having a parallel two-core structure.

  The center conductor 1 is made of copper, for example, and may be a conductive wire that is tin-plated or silver-plated. The center conductor 1 is preferably a stranded wire because it has flexibility, but may be a single wire.

  The insulating coating layer 2 is made of a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), or PP. (Polypropylene), PE (polyethylene) and other olefin resins.

  In addition to the two central conductors 1 arranged in parallel at predetermined intervals, the signal line includes a drain line 3. The drain wire 3 is made of, for example, copper, and may be a conducting wire plated with tin or silver.

  As shown in FIG. 2, the outer conductor layer 4 includes a conductive resin layer 4a made of a conductive resin and a metal layer 4b. For example, an acrylic conductive adhesive can be used as the conductive resin layer 4a, and an electrolytic copper foil can be used as the metal layer 4b. Alternatively, a polyethylene terephthalate portion of an aluminum mylar tape (AlPET tape) can be formed with the conductive resin layer 4a, and aluminum can be used as the metal layer 4b.

  Further, as shown in FIG. 3, the outer conductor layer 4 may be composed of a conductive resin layer 4a. For example, a highly conductive plastic sheet can be used as the conductive resin layer 4a.

(Function and effect)
According to the transmission cable according to the present embodiment, even if the outer conductor layer 4 is spirally wound around the signal line, the outer conductor layer 4 is elongated compared to the metal foil tape. It is hard to cut and does not impair the flexibility. Conventionally, when the outer conductor layer 4 is spirally wound, a plastic layer is inserted between the metal layers at the overlapping portion, and thus a capacitance is generated. However, in the present embodiment, since the outer conductor layer 4 is composed of the conductive resin layer 4a made of conductive resin, it is possible to suppress the occurrence of capacitance. Therefore, the attenuation does not drop sharply at a specific frequency.

  In the transmission cable according to the present embodiment, the outer conductor layer 4 may be composed of a conductive resin layer 4a and a metal layer 4b. According to the transmission cable having such a configuration, it is possible to further suppress the occurrence of capacitance in the outer conductor layer 4.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. It goes without saying that various alternative embodiments, examples and operational techniques are conceivable to those skilled in the art from this disclosure.

  For example, in the above embodiment, the differential signal transmission cable having two signal lines has been described as an example. However, the present invention covers the outer side of one central conductor with an insulating coating layer and the outer side of the outer conductor. You may apply to the coaxial table spirally wound by a layer. That is, the external conductor layer may be applied to a coaxial table by spirally winding a conductive resin layer or a tape composed of a conductive resin layer and a metal layer.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Hereinafter, the differential signal transmission cable according to the present invention will be specifically described with reference to examples. However, the present invention is not limited to those shown in the following examples, and the gist thereof is not changed. In the range, it can implement by changing suitably.

(Example)
As the differential signal transmission cable according to the example of the present invention, a differential signal transmission cable having a balanced two-core structure shown in FIGS. 1 and 2 was produced. Specifically, a silver-plated annealed copper stranded wire was used as the central conductor 1 and the drain wire 3, and polyethylene was used as the insulating coating layer 2. Further, as the outer conductor layer 4, a polyethylene terephthalate portion of an aluminum mylar tape (AlPET tape) was formed with a conductive resin layer 4a, and a metal layer 4b using aluminum was used.

(Comparative example)
As a differential signal transmission cable according to a comparative example of the present invention, a differential signal transmission cable having a balanced two-core structure shown in FIGS. 1 and 6 was produced. Specifically, the outer conductor layer 4 has the same structure as that of the example except that an aluminum mylar tape (AlPET tape) is used.

(Evaluation)
About the differential signal transmission cable which concerns on an Example and a comparative example, the attenuation amount in a specific frequency was measured. The measurement was performed using an Agilent E8364B PNA series network analyzer. The results of the comparative example and the example are shown in FIGS. 4 and 5, respectively.

  As shown in FIG. 4, in the conventional differential signal transmission cable used as a comparative example, capacitance is generated at the overlapping portion of the outer conductor layer (tape), and the attenuation amount suddenly drops at a specific frequency. As shown in FIG. 5, the differential signal transmission cable according to the present example was confirmed to have good characteristics without a drop in attenuation.

It is sectional drawing of the differential signal transmission cable which concerns on this embodiment. It is detail drawing of the outer conductor layer of the differential signal transmission cable which concerns on this embodiment (the 1). It is detail drawing of the outer conductor layer of the differential signal transmission cable which concerns on this embodiment (the 2). It is a graph which shows the attenuation amount of the differential signal transmission cable which concerns on a comparative example. It is a graph which shows the attenuation amount of the differential signal transmission cable which concerns on an Example. It is detail drawing of the outer conductor layer of the conventional differential signal transmission cable. It is a perspective view of the conventional differential signal transmission cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 ... Center conductor 2, 12 ... Insulation coating layer 3, 13 ... Drain wire 4, 14 ... External conductor layer 4a ... Conductive resin layer 4b ... Metal layer 14a ... Plastic layer 14b ... Metal layer

Claims (2)

A transmission cable comprising an outer conductor layer formed by spiral winding outside one or more signal lines comprising a center conductor and an insulating coating layer provided on the outer periphery of the center conductor,
The transmission cable, wherein the outer conductor layer is composed of a conductive resin layer made of a conductive resin.   The transmission cable according to claim 1, wherein the outer conductor layer includes the conductive resin layer and a metal layer.

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