Coaxial wire and multi-core cable

Abstract

The invention relates to a coaxial wire and a multi-core cable. The present disclosure provides a coaxial wire in which generation of a band empty segment is suppressed. A coaxial electric wire is provided with: a center conductor formed by twisting a plurality of conductor wires; an insulator disposed outside the center conductor; a shield layer disposed outside the insulator; and a sheath disposed outside the shield layer, the shield layer including, in order from a position closer to the center conductor, a first shield layer in which a metal wire is laterally wound, and a second shield layer in which a metal tape is disposed outside the first shield layer, the sheath including, in order from the position closer to the center conductor, the first shield layer and the second shield layer, the first shield layer being a layer in which the metal wire is laterally wound, and the second shield layer being a layer in which the metal tape is disposed outside the first shield layer. The outer diameter of the center conductor is 0.2 mm or more and 0.4 mm or less, and the twist pitch of the conductor wires in the center conductor is 6 times or more and 10 times or less of the outer diameter of the center conductor.

Description

Technical Field

[0001] The present disclosure relates to coaxial wires and multi-core cables. Background Art

[0002] Patent document 1 discloses a coaxial cable, which comprises: a conductor; an insulator covering the periphery of the conductor; a shielding layer having a transversely wound shielding portion obtained by spirally winding a plurality of metal wires in a manner covering the periphery of the insulator; and a sheath covering the periphery of the shielding layer, wherein the insulator has a recess on the surface of a portion in contact with the plurality of metal wires, which is engaged with the plurality of metal wires, and with respect to the shielding layer, portions of the plurality of metal wires in contact with the insulator in the circumferential direction are engaged with the recess of the insulator, and the plurality of metal wires adjacent in the circumferential direction of the shielding layer are in surface contact with each other.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-003613

[0006] Conventionally, coaxial electric wires having a shield layer have been used in various applications.

[0007] Furthermore, in conventional coaxial cables, a phenomenon called "suck out" may occur in which a sharp attenuation occurs in a predetermined frequency range. Summary of the invention

[0008] Therefore, an object of the present disclosure is to provide a coaxial electric wire in which generation of a frequency band null segment is suppressed.

[0009] The coaxial wire disclosed herein comprises: a center conductor formed by twisting a plurality of conductor wires; an insulator arranged outside the center conductor; a shielding layer arranged outside the insulator; and an outer sheath arranged outside the shielding layer, the shielding layer including a first shielding layer and a second shielding layer in order from a position close to the center conductor, the first shielding layer being a layer formed by transversely winding a metal wire, and the second shielding layer being a layer obtained by arranging a metal tape outside the first shielding layer, the outer diameter of the center conductor being greater than 0.2 mm and less than 0.4 mm, and the lay length of the conductor wire in the center conductor being greater than 6 times and less than 10 times the outer diameter of the center conductor.

[0010] Effects of the Invention

[0011] According to the present disclosure, it is possible to provide a coaxial electric wire in which generation of a frequency band null segment is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a cross-sectional view of a coaxial wire according to one embodiment of the present disclosure, taken on a plane perpendicular to the longitudinal direction.

[0013] Figure 2 This is a cross-sectional view of the metal strip taken on a plane perpendicular to the longitudinal direction.

[0014] Figure 3 This is a cross-sectional view of a multi-core cable according to one embodiment of the present disclosure, taken on a plane perpendicular to the longitudinal direction.

[0015] Figure 4 The following are evaluation results of the attenuation of the coaxial cables produced in Experimental Example 1.

[0016] Figure 5 The following are evaluation results of the attenuation of the coaxial cables produced in Experimental Example 2.

[0017] Description of Reference Numerals

[0018] 10: coaxial wire;

[0019] 11: center conductor;

[0020] D11: outer diameter of the center conductor;

[0021] 111: Conductor wire;

[0022] 12: Insulator;

[0023] 13: Shielding layer;

[0024] 131: first shielding layer;

[0025] 132: second shielding layer;

[0026] 1311: Metal wire;

[0027] 14: skin;

[0028] 20: Metal belt;

[0029] 21: resin layer;

[0030] 22: metal layer;

[0031] 30: Multi-core cable;

[0032] 300: core;

[0033] 31: Filling;

[0034] 32: Pressing roll;

[0035] 33: external shielding layer;

[0036] 34: Peripheral covering;

[0037] 40: empty frequency band. DETAILED DESCRIPTION

[0038] Hereinafter, specific implementation methods will be described.

[0039] [Description of Embodiments of the Present Disclosure]

[0040] First, the embodiments of the present disclosure will be described by way of example. In the following description, the same reference numerals are given to the same or corresponding elements, and the same description thereof will not be repeated.

[0041] (1) A coaxial electric wire according to one embodiment of the present invention comprises: a center conductor formed by twisting a plurality of conductor wires; an insulator arranged outside the center conductor; a shielding layer arranged outside the insulator; and a sheath arranged outside the shielding layer, the shielding layer including a first shielding layer and a second shielding layer in order from a position close to the center conductor, the first shielding layer being a layer formed by transversely winding a metal wire, and the second shielding layer being a layer formed by arranging a metal tape outside the first shielding layer, the outer diameter of the center conductor being not less than 0.2 mm and not more than 0.4 mm, and the lay length of the conductor wires in the center conductor being not less than 6 times and not more than 10 times the outer diameter of the center conductor.

[0042] The coaxial electric wire according to one aspect of the present disclosure includes the first shield layer and the second shield layer as shield layers, thereby being able to particularly suppress signal leakage to the outside and radio wave intrusion from the outside.

[0043] By setting the twisting length of the conductor wire in the center conductor to be greater than 6 times and less than 10 times the outer diameter of the center conductor, the frequency at which the band gap occurs can be in a frequency region higher than 20 GHz. Therefore, the generation of the band gap in the frequency domain of the signal transmitted by the coaxial cable of one embodiment of the present disclosure can be suppressed.

[0044] (2) A multi-core cable according to one aspect of the present disclosure includes: a core formed by twisting a plurality of coated electric wires including the coaxial electric wire described in (1); and an outer peripheral coating arranged outside the core.

[0045] According to the multi-core cable of one aspect of the present disclosure, since it includes the coaxial electric wire of one aspect of the present disclosure, it is possible to suppress the occurrence of a frequency band null segment.

[0046] [Details of the embodiments of the present disclosure]

[0047] Hereinafter, specific examples of coaxial wires and multi-core cables of one embodiment of the present disclosure (hereinafter referred to as "this embodiment") are described with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, but is shown by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0048] Explains the structure of coaxial wires, metal ribbons, and multi-core cables Figure 1 , Figure 2 , Figure 3 The drawings are schematically shown for explaining the arrangement of each component, and do not accurately show the size, shape, etc. of each component.

[0049] [Coaxial cable]

[0050] Figure 1 2 shows a cross section perpendicular to the longitudinal direction of the coaxial wire 10 of the present embodiment. Figure 1 In FIG. 1 , the Z axis perpendicular to the paper plane is an axis along the longitudinal direction of the coaxial wire 10 and the central conductor 11 , and the XY plane is a plane perpendicular to the longitudinal direction of the coaxial wire 10 and the central conductor 11 .

[0051] like Figure 1 As shown, the coaxial cable 10 of the present embodiment includes: a center conductor 11 ; an insulator 12 disposed outside the center conductor 11 ; a shield layer 13 disposed outside the insulator 12 ; and a sheath 14 disposed outside the shield layer 13 .

[0052] Hereinafter, each member included in the coaxial cable 10 of the present embodiment will be described.

[0053] (1) Components of coaxial cables

[0054] (1-1) Center conductor and conductor wire

[0055] The central conductor 11 has a structure in which a plurality of conductor wires 111 are twisted together. That is, the central conductor 11 may be a twisted wire.

[0056] The material of the conductor wire 111 is not particularly limited, but for example, one or more conductor materials selected from copper alloy, copper, silver-plated annealed copper, and tin-plated annealed copper can be used. Annular copper can be preferably used as copper.

[0057] exist Figure 1 , an example is shown in which seven conductor wires 111 are twisted to form the center conductor 11, but the number of conductor wires 111 constituting the center conductor 11 is not particularly limited. The number of conductor wires 111 of the center conductor 11 can be set to any number according to the outer diameter D11 and cross-sectional area required for the center conductor 11.

[0058] The inventors of the present invention have studied a coaxial wire in which generation of a frequency band null is suppressed. In this specification, the coaxial wire in which generation of a frequency band null is suppressed refers to a coaxial wire in which generation of a frequency band null is suppressed in a frequency range of 20 GHz or less.

[0059] As a result of research, the inventors of the present invention have found that the occurrence of band gaps can be suppressed by configuring the lay length of the conductor wire 111 in the center conductor 11 to be a predetermined ratio relative to the outer diameter D11 of the center conductor 11, thereby completing the present invention.

[0060] Therefore, in the coaxial cable 10 of the present embodiment, the lay length of the conductor wire 111 in the center conductor 11 can be set to be 6 times or more and 10 times or less the outer diameter D11 of the center conductor 11 .

[0061] By setting the lay length of the conductor wire 111 in the center conductor 11 to be greater than 6 times and less than 10 times the outer diameter D11 of the center conductor 11, the frequency at which the band gap occurs can be in a frequency region higher than 20 GHz. Therefore, the occurrence of the band gap in the frequency domain of the signal transmitted through the coaxial cable 10 can be suppressed.

[0062] The lay length of the conductor wire 111 in the center conductor 11 may be 6 times or more and 8 times or less the outer diameter D11 of the center conductor 11 .

[0063] The outer diameter D11 of the center conductor 11 is not particularly limited, but can be set to, for example, 0.2 mm or more and 0.4 mm or less.

[0064] (1-2) Insulator

[0065] The material constituting the insulator 12 is not particularly limited, but may include a resin material.

[0066] For example, one or more selected from fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride, polymethylpentene, etc. can be used as the resin material. The resin material contained in the insulator may be cross-linked or not.

[0067] The insulator 12 may also be composed only of the above-mentioned resin material, but in addition to the resin material, the insulator 12 may also contain one or more additives selected from flame retardants, flame retardant aids, antioxidants, lubricants, colorants, reflective agents, masking agents, processing stabilizers, plasticizers, etc.

[0068] (1-3) Shielding layer

[0069] The coaxial cable 10 of the present embodiment may include, as the shield layer 13 , a first shield layer 131 and a second shield layer 132 in order from a position close to the center conductor 11 .

[0070] The coaxial cable 10 of the present embodiment includes the first shield layer 131 and the second shield layer 132 as the shield layer 13 , thereby being able to particularly suppress signal leakage to the outside and radio wave intrusion from the outside.

[0071] Each shielding layer is described.

[0072] (First shielding layer)

[0073] The first shield layer 131 is a layer formed by transversely winding a metal wire 1311 , that is, spirally winding a plurality of metal wires in a state where the metal wires are closely connected and arranged in parallel.

[0074] By setting the first shielding layer 131 as a layer formed by winding the metal wire 1311 horizontally, the coaxial wire 10 can be made thinner, the flexibility of the coaxial wire 10 can be improved, and the coaxial wire 10 can be easily bent. In addition, by setting the first shielding layer 131 as a layer formed by winding the metal wire 1311 horizontally, the cost of the coaxial wire 10 can be reduced.

[0075] The material of the metal wire 1311 is not particularly limited, but for example, metal materials such as copper, copper alloy, aluminum, and aluminum alloy, or tin-plated annealed copper, which is a material obtained by plating the surface of these materials, can be used. Annular copper can be preferably used as copper.

[0076] (Second shielding layer)

[0077] The second shield layer 132 is a layer in which a metal tape is arranged outside the first shield layer 131. The second shield layer 132 can be configured by, for example, spirally winding a metal tape on the surface of the first shield layer 131.

[0078] use Figure 2 Next, a configuration example of the metal tape 20 that can be used for the second shield layer 132 is described. Figure 2 It is a cross-sectional view of the metal strip 20 taken along a plane perpendicular to the longitudinal direction.

[0079] like Figure 2 As shown, the metal tape 20 may include a resin layer 21 and a metal layer 22 and may have a structure in which the resin layer 21 and the metal layer 22 are stacked.

[0080] Examples of the resin contained in the resin layer 21 include one or more selected from polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene (PP), and vinyl resins such as polyvinyl chloride (PVC). The resin layer 21 may contain additives in addition to various resins.

[0081] The material of the metal layer 22 is not particularly limited, and one or more metal materials selected from copper, copper alloy, aluminum, aluminum alloy, etc. can be cited. The metal layer 22 can be composed of a single metal type, or can be composed of metal layers of two or more metal types stacked. In addition, a material other than metal, such as a protective film containing an organic material, can also be arranged on the surface of the metal layer 22.

[0082] The metal layer 22 may be a vapor-deposited film or a plated film.

[0083] (1-4) Skin

[0084] The outer skin 14 may be disposed outside the shielding layer 13 .

[0085] The material of the outer skin 14 is not particularly limited, and may include, for example, a resin material. Examples of the resin material include one or more selected from polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene, polyvinyl chloride (PVC), FEP, and fluororesins such as PFA.

[0086] The outer cover 14 may contain various additives such as a flame retardant in addition to the resin material.

[0087] The resin material of the outer skin 14 may or may not be cross-linked.

[0088] The outer covering 14 can be formed, for example, by spirally winding a resin tape containing a resin material on the surface of the shield layer 13 .

[0089] [Multi-core cable]

[0090] Figure 3 2 shows a configuration example of a cross section perpendicular to the longitudinal direction of the multi-core cable of the present embodiment. Figure 3 The direction along the Z axis from the paper surface in φ corresponds to the longitudinal direction of the multi-core cable 30 and the core 300. The XY plane is a cross section perpendicular to the longitudinal direction of the multi-core cable 30 and the core 300.

[0091] like Figure 3 As shown, the multi-core cable 30 of the present embodiment includes a core 300 formed by twisting a plurality of coated electric wires including the coaxial electric wire 10 , and an outer peripheral coating 34 disposed outside the core 300 .

[0092] According to the multi-core cable 30 of the present embodiment, since it includes the coaxial electric wire 10 according to one aspect of the present disclosure, it is possible to suppress the occurrence of a frequency band null segment.

[0093] Each member included in the multi-core cable of this embodiment will be described.

[0094] (1) core

[0095] The core 300 has a plurality of coated electric wires including the coaxial electric wire 10 according to one aspect of the present disclosure.

[0096] exist Figure 3 In the illustrated multi-core cable 30 , an example is shown in which the core 300 includes the coaxial electric wire 10 according to one aspect disclosed in the present invention, but the present invention is not limited to this embodiment.

[0097] The configuration and number of the coated electric wires included in the core 300 are not particularly limited and can be selected based on the performance required of the multi-core cable 30 .

[0098] The core 300 may include, in addition to the coaxial wire 10, an electric wire having a central conductor 11 and an insulator 12 disposed outside the central conductor 11 as a covered electric wire. In addition, the core 300 may include, in addition to the covered electric wire, a drain wire consisting only of a conductor.

[0099] The covered electric wires included in the multi-core cable 30 may be, for example, twisted pair electric wires in which two wires are twisted as a pair.

[0100] The arrangement of the covered electric wires in the core 300 is not particularly limited, and for example, the covered electric wires may be arranged in a single layer or multiple layers from the center in a cross section perpendicular to the longitudinal direction of the core 300 .

[0101] exist Figure 3 In the illustrated multi-core cable 30 , coaxial electric wires 10 as coated electric wires are arranged in one layer with respect to the core 300 and are twisted.

[0102] (2) Peripheral covering

[0103] The outer peripheral cover 34 may be disposed outside the core 300 .

[0104] The material of the outer peripheral cover 34 is not particularly limited. The outer peripheral cover 34 may include a resin material. Examples of the resin material include polyolefins such as polyethylene, polyvinyl chloride (PVC), and thermoplastic elastomers (TPE).

[0105] The outer peripheral cover 34 may contain various additives such as a flame retardant in addition to the above-mentioned resin material.

[0106] The material of the outer peripheral coating 34 may or may not be cross-linked.

[0107] The multi-core cable 30 has an outer peripheral coating 34 , and thereby can protect the coated electric wires and the like arranged inside.

[0108] The multi-core cable 30 may include components other than the core 300 and the outer peripheral coating 34 .

[0109] (3) External shielding layer

[0110] The outer shield layer 33 may be disposed between the core 300 and the outer peripheral cover 34 .

[0111] The multi-core cable 30 has the outer shield layer 33, thereby suppressing the superposition of noise on the signal propagated by the coated electric wire. In addition, the influence of noise on external equipment can be suppressed.

[0112] The outer shielding layer 33 may include a conductive material.

[0113] For example, the outer shield layer 33 may be configured by spirally winding a conductive tape including a conductive layer along the length direction of the core 300 .

[0114] The conductive tape may include a base member and a conductive layer disposed on at least one of the upper surface and the lower surface of the base member. The conductive tape may include the conductive layer on both the upper surface and the lower surface of the base member. The conductive tape may also not include a base member but be composed only of the conductive layer.

[0115] The material of the conductive layer is not particularly limited, but preferably contains metal, and for example, metal foil can be used. When the conductive layer contains metal, the material of the metal is not particularly limited, and for example, copper, copper alloy, aluminum, aluminum alloy, etc. can be used.

[0116] The material of the base member is not particularly limited, but is preferably made of an insulating material such as an organic polymer material or a nonwoven fabric. Examples of the organic polymer material include polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene, and vinyl resins such as polyvinyl chloride. The base member may be a base member including an insulating material or a base member consisting only of an insulating material.

[0117] When the outer shield layer 33 is formed by winding a conductive tape as described above, the winding direction of the conductive tape can be arbitrarily selected, for example, it can be the same direction as the twisting direction of the core 300 or a direction different from the twisting direction of the core 300 .

[0118] The outer shielding layer 33 may also include a metal wire. In this case, the outer shielding layer 33 may have a structure in which the metal wire is wound horizontally, or a structure in which the metal wire is braided. Copper, aluminum, copper alloy, etc. may be used as the material of the metal wire. The surface of the metal wire may also be plated with silver or tin. Therefore, for example, a silver-plated copper alloy, a tin-plated copper alloy, etc. may also be used as the metal wire.

[0119] The outer shielding layer 33 may be composed of not only one layer but also multiple layers. When the outer shielding layer 33 has multiple layers, for example, it may have a first outer shielding layer obtained by spirally winding a conductive tape along the length direction of the core 300 and a second outer shielding layer obtained by transversely winding a metal wire or braiding a metal wire.

[0120] (4) Rolling

[0121] The multi-core cable 30 may also have a crimp 32 covering the outer surface of the core 300 .

[0122] The multi-core cable 30 has the crimp 32 , and thereby the arrangement of the plurality of coated electric wires included in the multi-core cable 30 can be stabilized and the plurality of coated electric wires can be bundled.

[0123] As the press roll 32 , for example, a resin tape may be used.

[0124] Examples of the resin used for the resin belt include one or more selected from fluororesins such as polytetrafluoroethylene (PTFE) resin, polyester resins such as polyethylene terephthalate (PET) resin, and polyethylene (PE) that are excellent in heat resistance and abrasion resistance.

[0125] In order to have conductivity, the resin tape used as the roll 32 may also contain a conductive material such as carbon. The conductive material is preferably added in a manner dispersed in the resin constituting the resin tape. In addition, for example, a metal tape obtained by configuring copper foil or aluminum foil on the surface of the resin tape may also be used.

[0126] The winding direction of the roll 32 may be the same as or opposite to the twisting direction of the covered electric wires constituting the core 300. It should be noted that as the roll 32, a metal tape having copper foil, aluminum foil, etc. may be used instead of the resin tape.

[0127] Since the multi-core cable 30 has the crimp 32 , when the outer shield layer 33 is disposed outside the core 300 , it is possible to prevent the insulation and the like of the coated electric wire constituting the core 300 from being damaged.

[0128] (5) Filling

[0129] The multi-core cable 30 may also include a filler 31. The filler 31 may be arranged in a gap surrounded by the covered electric wires such as the coaxial wire 10. Figure 3 , an example is shown in which the filler 31 is arranged in the center surrounded by the coaxial wire 10 in a cross section perpendicular to the longitudinal direction of the multi-core cable 30, but the present invention is not limited to this form, and the filler 31 can be arranged in any place. Figure 3 In the figure, the filler 31 is shown in a shape close to a circle, but the filler 31 may also be in a shape corresponding to the gap to be configured, and is not limited to Figure 3 Shape shown.

[0130] The filler 31 may include fibers such as staple fibers, nylon yarns, etc. The filler may also include tensile fibers.

[0131] The multi-core cable 30 has the filler 31, which can improve the workability when twisting the covered wires to produce the core 300 and the multi-core cable 30. In addition, the multi-core cable 30 has the filler 31, which can easily make the outer shape of the core 300 and the multi-core cable 30 in the cross section perpendicular to the length direction close to a circle, thereby improving the handling of the multi-core cable 30.

[0132] [Example]

[0133] Hereinafter, specific examples will be given for description, but the present invention is not limited to these examples.

[0134] (Evaluation method)

[0135] First, a method for evaluating coaxial electric wires produced in the following experimental examples will be described.

[0136] (1) The outer diameter of the center conductor D11

[0137] The outer diameter D11 of the center conductor 11 included in the coaxial electric wire 10 was measured using a micrometer in accordance with the method described in JIS C 3005 (2014).

[0138] Specifically, in any cross section perpendicular to the longitudinal direction of the coaxial wire 10 , the lengths of two orthogonal diameters of the center conductor 11 are measured, and the average value is defined as the outer diameter of the center conductor 11 .

[0139] (2) The lay length of the conductor wire in the center conductor

[0140] The lay pitch of the conductor wire 111 in the center conductor 11 was measured according to the method described in JIS C 3005 (2014). The ratio (P / D11) of the lay pitch P to the outer diameter D11 of the center conductor 11 was calculated.

[0141] (3) Frequency band vacancy

[0142] The attenuation per unit length of the coaxial cable 10 was measured and calculated using a network analyzer.

[0143] When no empty band was found in the frequency band below 20 GHz, the evaluation was A, and when an empty band was found in the frequency band below 20 GHz, the evaluation was B.

[0144] When the evaluation is A, it can be evaluated that the coaxial wire suppresses the occurrence of a band null segment. When the evaluation is B, it can be evaluated that the coaxial wire fails to suppress the occurrence of a band null segment.

[0145] (Experimental conditions and results)

[0146] Hereinafter, the coaxial electric wire in each experimental example will be described.

[0147] Coaxial electric wires were produced according to the following Experimental Examples 1, 2, 3, and 4. Experimental Example 1 is a comparative example, and Experimental Examples 2, 3, and 4 are examples.

[0148] [Experimental Example 1]

[0149] like Figure 1 As shown, a coaxial wire 10 is produced which has a center conductor 11, an insulator 12 arranged outside the center conductor 11, a shield layer 13 arranged outside the insulator 12, and a sheath 14 arranged outside the shield layer 13 in a cross section perpendicular to the longitudinal direction.

[0150] The center conductor 11 is a stranded wire formed by stranding seven conductor wires 111 which are silver-plated annealed copper wires having outer diameters shown in Table 1. Table 1 shows the evaluation results of the outer diameter D11 of the center conductor 11 and the lay length P of the conductor wires 111.

[0151] The insulator 12 , the shield layer 13 , and the outer skin 14 have the configuration shown in Table 1.

[0152] Figure 4 The evaluation results of the attenuation of the coaxial wire of Experimental Example 1 are shown in FIG. Figure 4 As shown, a frequency band null segment 40 is observed.

[0153] [Experimental Example 2, Experimental Example 3]

[0154] The coaxial electric wire 10 was produced and evaluated under the same conditions as those in Experimental Example 1 except that the lay length of the conductor wire 111 was changed to the value shown in Table 1 when the center conductor 11 was produced.

[0155] Table 1 shows the evaluation results.

[0156] Figure 5 2 shows the evaluation results of the attenuation of the coaxial cable in Experimental Example 2.

[0157] [Experimental Example 4]

[0158] When manufacturing the center conductor 11, the conductor wire 111 having the outer diameter shown in Table 1 was used, and the twist pitch of the conductor wire 111 was changed to the value shown in Table 1. Except for the above, the coaxial cable 10 was manufactured under the same conditions as Experimental Example 1 and evaluated.

[0159] Table 1 shows the evaluation results.

[0160] [Table 1]

[0161]

Claims

1. A coaxial wire having: The center conductor is made by twisting multiple conductor wires; an insulator, disposed outside the central conductor; A shielding layer, arranged outside the insulator; as well as An outer skin is arranged outside the shielding layer, The shielding layer includes a first shielding layer and a second shielding layer in order from a position close to the center conductor. The first shielding layer is a layer formed by transversely winding a metal wire. The second shielding layer is a layer obtained by configuring a metal tape outside the first shielding layer. The outer diameter of the central conductor is not less than 0.2 mm and not more than 0.4 mm, A lay length of the conductor wire in the center conductor is 6 times or more and 10 times or less of an outer diameter of the center conductor.

2. A multi-core cable having: A core formed by twisting a plurality of coated electric wires including the coaxial electric wire according to claim 1; and The outer periphery cover is arranged outside the core.

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