JP4110382B2 - Digital signal differential transmission cable, manufacturing method thereof, and harness using the same - Google Patents

Description

【００３４】
ここで上記表１では、スプリットありとは同一ケーブルから切り出したものをいう。
【００３５】
このように本発明の実施の形態のディジタル信号差動伝送ケーブルの場合、指定した2本の同軸ケーブルの遅延時間の差は最大でも２２ｐｓ／ｍ以下となっている。
【００３６】
なおこのようなディジタル信号差動伝送ケーブルの両端にコネクタを取り付けることにより信頼性の高いハーネスを得ることが可能となる。
【００３７】
また、前記実施の形態では、2，4，6，8本のケーブルにより差動伝送に用いた例について説明したがこの他さらにこの外側に何対かの同軸ケーブル対を形成したもの、あるいは中心の制御信号用ケーブルの使用しないものなど、種々の場合に適用可能であることは言うまでもない。
【００３８】
【発明の効果】
以上説明したように、本発明のディジタル信号差動伝送ケーブルによれば差動伝送ライン（＋芯とー芯）に同一の断面構造をもつ２本の同軸ケーブル対を用いることにより、Ｓｋｅｗを低減することが可能となる
【図面の簡単な説明】
【図１】本発明の実施の形態のディジタル信号差動伝送ケーブルを示す断面説明図である。
【図２】本発明の実施の形態のディジタル信号差動伝送ケーブルの要部拡大説明図である。
【図３】本発明の実施の形態のディジタル信号差動伝送ケーブルを示す断面説明図である。
【図４】本発明の実施の形態のディジタル信号差動伝送ケーブルを示す断面説明図である。
【図５】本発明の実施の形態のディジタル信号差動伝送ケーブルを示す断面説明図である。
【図６】従来例のディジタル信号差動伝送ケーブルを示す図である。
【図７】従来例のディジタル信号差動伝送ケーブルを示す図である。
【符号の説明】
３０A、３０B 同軸ケーブル
３１Ａ 第1の絶縁樹脂
３２Ａ 第1の中心導体
３３A 第1の内側内部遮蔽
３４A 被覆層
３１Ｂ 第２の絶縁樹脂
３２Ｂ 第２の中心導体
３３Ｂ 第２の内側内部遮蔽
３４Ｂ 被覆層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital signal differential transmission cable, a method of manufacturing the same, and a harness using the same, and in particular, in a digital transmission system, two coaxial cables are used to form a differential, and the coaxial cable is shielded and manufactured. The present invention relates to a differential transmission cable in which the two differential transmission cores are manufactured concentrically and the difference between the two delay times (inward skew) is reduced.
[0002]
[Prior art]
A current DVI cable is shown in FIG. The differential transmission cable used in this DVI cable is formed by twisting two insulated conductor wires 100A and 100B made of conductors 101A and 101B covered with an insulating resin 102 together with a drain wire 103, as shown in FIG. The four shielded twisted pair cables 100 covered with the insulating resin 105 and shielded by using the metal tape 104 are used, and the electrical connectors defined by the standards are connected to both ends thereof. ing. The insulated conductor wires 100A and 100B are formed by covering the central conductor wires 101A and 101B with an insulating resin 102. In this DVI cable, as shown in FIG. 6, five independent covered third central conductors 120 are twisted, and each of the above-mentioned twisted pair cables (Twinax) 100 with shielding is interposed therebetween. Four of them are arranged, and this is covered with a first and second outer shielding layers 107 and 108 and a jacket made of PVC resin.
[0003]
In order to reduce the inward skew with each such shielded cable,
A. Variations in insulator dimensions (conductor diameter, insulation diameter),
B. Variation of dielectric constant of insulator,
C. Variation in twisting pitch,
D. It is necessary to suppress fluctuations in the shielding space.
Since the twinax cable currently used twists two insulators together, the insulators may be crushed, and the relative permittivity that determines the delay time may vary in the length direction of the cable.
[0004]
Twinax cables are made by twisting two insulated conductor wires, each of which is an insulation coating on the central conductor wire, and shielding it on top of each other. Therefore, a space layer (between each insulated conductor wire and the shield ( Air gap) may occur, and the equivalent dielectric constant may fluctuate. As a result, there was a problem that the inward skew would deteriorate.
[0005]
[Problems to be solved by the invention]
As described above, in the digital transmission using the conventional twinax cable, the relative permittivity that determines the relative permittivity of the two insulated conductor wires fluctuates in the length direction of the cable, or the twisted insulated pair and the shield are shielded. There is a problem that the inward skew becomes worse due to a gap between the two and the equivalent dielectric constant fluctuating.
[0006]
This invention is made | formed in view of the said situation, and it aims at reducing inward skew.
[0007]
[Means for Solving the Problems]
Therefore, the present invention includes a first central conductor, a first insulating resin layer formed around the first central conductor, a first conductor layer covering the outer side, and a first insulating coating layer covering the outer side. A first coaxial cable, a second central conductor, a second insulating resin layer formed therearound, a second conductor layer covering the outside, and a second conductor layer covering the outside. A second coaxial cable having an insulating coating layer, wherein the first conductor layer and the second conductor layer are respectively formed in a horizontal winding, and the first and second coaxial cables are formed. The cables constitute coaxial cable pairs that have the same cross-sectional structure and have the same length, and the coaxial cable pairs of each pair are arranged in a concentric circle, A conductor layer for external shielding covering the outside, and further the conductor layer Characterized by comprising an insulating jacket city covering the side.
[0008]
According to such a configuration, by using two coaxial cables having the same cross-sectional structure for the differential transmission line (+ core and -core), the delay time of each coaxial cable that causes a problem with the conventional cable is determined. The relative dielectric constant becomes the same level, and the inward skew can be reduced. Furthermore, since each pair is arranged so as to be arranged concentrically, the physical distance between the two cores can be made the same, and fluctuations in the delay time of each core can be suppressed, thereby reducing the pair skew. It becomes possible to do.
[0009]
Preferably, the first and second coaxial cables are formed of coaxial cables cut out from the same cable at least for each pair.
[0010]
According to such a configuration, a cable having the same structure can be manufactured easily and reliably.
[0011]
Desirably, the coaxial cable is formed to transmit a differential signal having an opposite phase.
[0012]
According to such a configuration, it is possible to provide a cable with a small skew and a high-speed transmission method using the cable.
[0015]
The harness of the present invention comprises the above-mentioned digital signal differential transmission cable and electrical connectors connected to both ends thereof.
[0016]
According to such a configuration, it is possible to provide a harness having a small inward skew and good transmission characteristics.
[0017]
Further, the method of the present invention includes a coaxial cable forming step of forming a coaxial cable comprising a central conductor, an insulating resin layer formed around the center conductor, and a horizontally wound conductor layer covering the outside thereof, and the coaxial cable forming step. Cutting the cable to have the same length and dividing it into a plurality of coaxial cables, arranging the plurality of coaxial cables so that they are arranged concentrically, and covering the outside with a conductor layer for external shielding And a step of coating the outside of the conductor layer with an insulating coating layer.
[0018]
According to such a configuration, since the coaxial cable is configured by splitting the coaxial cable manufactured under the same conditions, the relative permittivity that determines the delay time of each core becomes the same level, and the inward skew is reduced. Is possible.
[0019]
In addition, it is possible to identify the specified 2-core by forming a resin layer of a specified color such as polyester tape or PVC resin on a metal shielding material or printing a specific pattern. .
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the digital signal differential transmission cable according to the first embodiment of the present invention constitutes a coaxial two-core cable with a collectively braided shield. In this example, two coaxial cables 30A and 30B are provided. Are arranged on concentric circles, and the outside is covered with a first external shield 40 made of aluminum-coated polyester tape, and the outside is further covered with a single braided tin-plated annealed copper wire having a wire diameter of 0.10 mm. The outer cover 50 is covered with a PVC resin as the outer cover 60 at the end.
[0021]
Each of the coaxial cables 30A and 30B is one coaxial cable cut out to the same length and arranged. That is, the coaxial cable pair which is one of these coaxial cables is composed of coaxial cables having the same structure as shown in the enlarged view of FIG. For example, the coaxial cable 30A is formed as a first central conductor 32A covered with a first insulating resin 31A having a thickness of 0.35 mm and an outer diameter of 1.10 mm and surrounded by an annealed copper wire having a diameter of 0.41 mm. The first inner inner shield 33A is formed by horizontally winding an annealed copper wire having a strand diameter of 0.08 mm, and further covering the outer side with a coating layer 34A made of PVC resin.
[0022]
As described above, in the present invention, skew can be reduced by using a pair of coaxial cables arranged in a concentric circle on the differential transmission line.
[0023]
(Second Embodiment)
Next, as a second embodiment of the present invention, as shown in FIG. 3, it is also effective to use two-to-four coaxial cables 30A, 30B, 30C, and 30D. In this example, all four cables are cut out from the same cable and used so that the first pair of coaxial cables 30A and 30B and the second pair of coaxial cables 30C and 30D are concentrically adjacent to each other. Each coaxial cable is formed in the same manner as in the first embodiment.
Here, by coating the colored PVC resin on the outside of the first outer inner shields 34A, 34B, 34C, 34D, 34E, 34D, each pair can be easily identified.
[0024]
(Third embodiment)
Next, as a third embodiment of the present invention, as shown in FIG. 4, it is effective to use two-to-four coaxial cables 30A, 30B, 30C, and 30D. In this example, all four cables are cut out from the same cable, and the first pair of coaxial cables 30A and 30B, the second pair of coaxial cables 30C and 30D, and the third pair of coaxial cables 30E and 30F are concentrically arranged. It is formed to be adjacent.
[0025]
(Fourth embodiment)
Next, as a fourth embodiment of the present invention, as shown in FIG. 5, one using three to six coaxial cables 30A, 30B, 30C, 30D, 30E, 30F is also effective. In this example, all six cables are cut out from the same cable, and the first pair of coaxial cables 30A and 30B, the second pair of coaxial cables 30C and 30D, and the third pair of coaxial cables 30E and 30F are concentrically arranged. It is formed to be adjacent. Here, a resin material called a core or another cable is arranged at the center of the cable.
[0026]
Next, as a fifth embodiment of the present invention, as shown in FIG. 6, it is also effective to use four to eight coaxial cables 30A, 30B, 30C, 30D, 30E, 30F, 30G, and 30H. . In this example, all eight cables are cut out from the same cable and used, and the first pair of coaxial cables 30A and 30B, the second pair of coaxial cables 30C and 30D, the third pair of coaxial cables 30E and 30F, and the fourth pair. A pair of coaxial cables 30G and 30H are formed concentrically so as to face each other.
[0027]
In this example, all eight cables were cut out from the same cable. In the second, third, and fourth embodiments, at least each pair that transmits a differential signal may be of equal length, and each pair that is cut out from the same cable is used. Also good. For example, in the fourth embodiment, a first pair consisting of coaxial cables 30A and 30B, a second pair consisting of second coaxial cables 30E and 30F consisting of coaxial cables 30C and 30D, and coaxial cables 30G and 30H. The fourth pair consisting of 4 is cut out from different coaxial cables, and a differential signal is input and used for each pair.
[0028]
Further, the outer shield 40 inside the sheath part is made of, for example, an aluminum-attached polyester tape having a thickness of 0.015 mm, and can have a thin outer diameter and maintain good electrical characteristics and mechanical characteristics.
[0029]
When a metal tape is used, unnecessary radiation (EMI: Electromagnetic Interference) noise can be reduced as compared with the case where an insulating tape is used.
[0030]
In this example, the skew is 10 ps / m or less.
[0031]
As described above, in the present invention, by using two coaxial cables for the differential transmission line, the relative permittivity for determining the delay time of each core becomes the same level, the inward skew can be reduced, and the transmission characteristics are excellent. It is possible to provide a simple digital signal transmission cable.
[0032]
As a result of measuring the skew of the digital signal differential transmission cable (not split) and the conventional shielded twisted pair cable according to the embodiment of the present invention, the results were as follows.
[0033]
[Table 1]

[0034]
Here, in Table 1 above, “with split” means one cut from the same cable.
[0035]
As described above, in the case of the digital signal differential transmission cable according to the embodiment of the present invention, the difference in delay time between the two designated coaxial cables is 22 ps / m or less at the maximum.
[0036]
It is possible to obtain a highly reliable harness by attaching connectors to both ends of such a digital signal differential transmission cable.
[0037]
Further, in the above embodiment, the example used for differential transmission with 2, 4, 6, 8 cables has been described, but in addition to this, several coaxial cable pairs are formed outside this, or the center Needless to say, the present invention can be applied to various cases such as those not using the control signal cable.
[0038]
【The invention's effect】
As described above, according to the digital signal differential transmission cable of the present invention, skew is reduced by using two coaxial cable pairs having the same cross-sectional structure for the differential transmission line (+ core and −core). [Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view showing a digital signal differential transmission cable according to an embodiment of the present invention.
FIG. 2 is an enlarged explanatory view of a main part of the digital signal differential transmission cable according to the embodiment of the present invention.
FIG. 3 is an explanatory cross-sectional view showing a digital signal differential transmission cable according to an embodiment of the present invention.
FIG. 4 is an explanatory cross-sectional view showing a digital signal differential transmission cable according to an embodiment of the present invention.
FIG. 5 is an explanatory cross-sectional view showing a digital signal differential transmission cable according to an embodiment of the present invention.
FIG. 6 is a diagram showing a conventional digital signal differential transmission cable.
FIG. 7 is a diagram showing a conventional digital signal differential transmission cable.
[Explanation of symbols]
30A, 30B Coaxial cable 31A First insulating resin 32A First central conductor 33A First inner inner shielding 34A coating layer 31B Second insulating resin 32B Second central conductor 33B Second inner inner shielding 34B coating layer

Claims (6)

A first central conductor, a first insulating resin layer formed around the first central conductor, a first conductor layer covering the outer side, and a first insulating coating layer covering the outer side. Coaxial cable,
A second central conductor, a second insulating resin layer formed around the second central conductor, a second conductive layer covering the outer side, and a second insulating coating layer covering the outer side. 2 coaxial cables,
Each of the first conductor layer and the second conductor layer is formed by horizontal winding,
The first and second coaxial cables constitute a coaxial cable pair configured to have the same cross-sectional structure and the same length .
These pairs of coaxial cables are arranged in a concentric circle,
A conductor layer for external shielding covering the outside;
Further characteristics and to Rudy digital signal differential transmission cable by comprising an insulating jacket city that covers the outside of the conductor layer.   2. The digital signal differential transmission cable according to claim 1, wherein the first and second coaxial cables are cut from the same cable.   3. The digital signal differential transmission cable according to claim 1, wherein the first coaxial cable and the second coaxial cable are connected so as to transmit signals having opposite phases to each other. 4. The digital signal differential transmission cable according to any one of claims 1 to 3 , wherein the first and second coaxial cables are configured to be able to identify the insulating coating layer. A digital signal differential transmission cable according to any one of claims 1 to 4, consisting of the connected electrical connectors at both ends harness. A coaxial cable forming step of forming a coaxial cable comprising a central conductor, an insulating resin layer formed around the center conductor, and a horizontally wound conductor layer covering the outside;
Cutting the coaxial cable to have the same length and dividing it into a plurality of coaxial cables;
The plurality of coaxial cables are arranged so as to be arranged concentrically,
Coating the outside with a conductor layer for external shielding;
And a step of covering the outside of the conductor layer with an insulating covering layer.

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