JPH0896631A - Multipair shielded cable - Google Patents

Abstract

PURPOSE: To provide a multipair shielded cable by which dispersion of a characteristic impedance and the propagation delay time of respective paired stranded wires in the same cable can be reduced and which is excellent in uniformity of respective signal transmitting passages and is excellent in terminal workability. CONSTITUTION: A multipair shielded cable is constituted in such a way that a large number of paired stranded wires (a) whose insulating strands have the same constitution are stranded in layers as plural layers and are formed as a multipair aggregate stranded wire (b) and shielding layers (d1 and d2 ) are arranged on the outer periphery. An interposing layer (c) which is composed of a dielectric and has a thickness not less than 0.1mm is arranged between the multipair aggregate stranded wire (b) and the shielding layer (d1 ), and the total lay ratio Yo of paired stranded wires of the outermost layer of the multipair aggregate strnded wire (b) and the total lay ratio Yi of paired stranded wires of an inner layer are set in (Yo>=Yi).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-pair shielded cable suitable for parallel transmission of digital signals in electronic equipment such as computers and their peripheral equipment.

[0002]

2. Description of the Related Art With the advanced development of electronic equipment such as computers and their peripheral equipment, electric wires and cables used in this field are required to have high performance and high reliability. In particular, in parallel transmission of digital signals using a multi-pair cable, variations in characteristic impedance and deviations in the arrival time of transmission pulses are becoming strict as the signal transmission speed increases.

For example, US ANSI X3T9.3 H
According to the SC / HIPPI interface standard, the characteristic impedance difference is 11Ω and the propagation delay time difference is 0.13 ns.
/ M, and similarly in the SCSI-3 parallel interface, the characteristic impedance difference is 20Ω,
The propagation delay time difference is specified as 0.15 ns / m.
The characteristic impedance difference and the propagation delay time difference are the difference between the maximum value and the minimum value of the characteristic impedance and the propagation delay time of each twisted pair in the same cable.

The conventional multi-pair cable for a computer has no regulation on the characteristic impedance difference and the propagation delay time difference and is generally used. The characteristic impedance difference is 30Ω and the propagation delay time difference is about 0.3 ns / m. there were. This difference occurs because the characteristic impedance and the propagation delay time change depending on where each twisted pair wire is located in the multi-pair cable.

The characteristic impedance of the twisted pair is determined by the distance between the conductors and the effective relative permittivity around the conductor, and in terms of the position within the multi-pair cable, the characteristic impedance becomes lower as it is closer to the shield layer having many metal parts. Further, the propagation delay time of the twisted pair is determined by the effective relative permittivity around the conductor, and the propagation delay time becomes larger as the shield layer is closer to the metal layer. Note that the characteristic impedance and the propagation delay time are the differential type TDR (Time Domain Reflect
or meter).

[0006]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to reduce variations in the characteristic impedance and propagation delay time of each twisted pair in the same cable and to make each signal transmission line uniform. It is to provide a multi-pair shielded cable having good performance.

In order to reduce the variations in the characteristic impedance and the propagation delay time of each twisted pair in the same cable, the insulation coating thickness of the twisted pair of twisted pair wires should be set for each layer of the multipair twisted pair wire. Means such as adjusting or adjusting the dielectric constant of the insulating coating by changing the material or the foaming ratio can be considered. However, with such a means, it is necessary to change the configuration of the twisted pair insulated wire for each layer of the multi-pair assembled stranded wire, which not only complicates the manufacturing of the cable but also terminates the terminal such as the connector attachment. There is a problem in that it is not possible to carry out a batch processing because the insulation coating thickness and material of the insulation strands of each twisted pair wire differ during processing.

[0008]

In order to achieve the above object, the present invention provides a multi-pair aggregated stranded wire by twisting a plurality of twisted stranded wires having the same constitution as an insulated wire into a plurality of layers, and the outer periphery thereof. In a multi-pair shielded cable in which a shield layer is provided on the outermost layer, an intervening layer having a thickness of 0.1 mm or more made of a dielectric material is provided between the multi-pair assembled stranded wire and the shield layer, and the outermost layer of the multi-pair assembled stranded wire is provided. Twisted ratio Yo of the twisted pair wire located at and the total twisted ratio Yi of the twisted pair wire not located in the outermost layer
Is defined as Yo ≧ Yi.

[0009]

The intervening layer made of a dielectric material is provided between the multi-pair assembled stranded wire and the shield layer in order to prevent the shield layer from electrically affecting the outermost pair stranded wire. That is, by providing an intervening layer made of a dielectric material between the multi-pair assembled stranded wire and the shield layer, the effective relative permittivity of the twisted pair located in the outermost layer of the multi-pair assembled stranded wire can be adjusted to the outermost layer. Do not attempt to reduce the variation in characteristic impedance by approaching the effective relative permittivity of the twisted pair. The thickness of the intervening layer is set to 0.1 mm or more in order to sufficiently reduce the electrical influence of the shield layer on the twisted pair of the outermost layer. The intervening layer needs to have a thickness of 0.1 mm or more, but it is preferable to use a dielectric material having a low dielectric constant in order to keep the thickness as thin as possible.

If an intervening layer made of a dielectric material and having a thickness of 0.1 mm or more is provided between the multi-pair twisted pair wire and the shield layer, the effective relative permittivity of the twisted pair wire in the multi-pair cable is adjusted. Therefore, variations in propagation delay time should be suppressed, but in reality, the propagation delay time of the twisted pair located in the outermost layer becomes too short (propagation speed becomes too fast), and the thickness of the intervening layer It was found that it is difficult to suppress variations in propagation delay time only by adjustment.

Therefore, the point that the propagation delay time of the twisted pair wire located in the outermost layer becomes too short is that the total twisting ratio Yo of the twisted pair wire positioned in the outermost layer is the total twisting rate of the twisted pair wire not located in the outermost layer. It should be equal to or more than the twist rate Yi, that is,
In the cable, the length of the twisted pair wire located in the outermost layer is adjusted to be relatively longer than the length of the twisted pair wire not located in the outermost layer. As a result, it has become possible to provide a multi-pair shielded cable in which the characteristic impedance of each twisted pair and the variation in propagation delay time are both sufficiently small.

The total twisting ratio Y is represented by the following equation, where yt is the twisting ratio of the twisted pair and yc is the twisting ratio of the multipair twisted pair.

[0013]

## EQU1 ## Y = yt xyc

The twisting ratio yt of the twisted pair wire is expressed by the following equation, where Pt is the twisting pitch of the twisted pair wire and dt is the distance between the centers of the insulating strands.

[0015]

## EQU2 ## yt = {Pt ² + (π × dt) ² } ^1/2 / Pt

In addition, the twisting ratio yc of the multi-pair assembled stranded wire is
The twist pitch of each layer of the multi-pair assembled stranded wire is Pc, and the core diameter is d
Let c be expressed by the following equation.

[0017]

## EQU3 ## yc = {Pc ² + (π × dc) ² } ^1/2 / Pc

On the other hand, the shield layer is usually made of tin, nickel,
It is formed by braiding or horizontally winding a copper wire or an aluminum wire with or without plating of silver or the like. The shield layer may be formed by winding an aluminum tape, a copper tape, or a laminate of these tapes with a plastic film in one layer or a plurality of layers. Further, braid, horizontal winding, and metal tape may be used in combination depending on the application. A sheath of polyethylene, polyvinyl chloride, or the like is applied to the outside of the shield layer to complete the multi-pair shielded cable.

[0019]

Embodiments of the present invention and comparative examples will be described below in detail with reference to the drawings. FIG. 1 shows a multi-pair shielded cable used in Examples of the present invention and Comparative Examples. In this cable, 25 pairs of twisted pair wires a are twisted in three layers to form a multi-pair set twisted wire b, and an intervening layer c is provided on the outer periphery of the multi-pair set twisted wire b.
The shield layers d ₁ and d ₂ and the sheath e are sequentially provided. The number in the circle indicating the twisted pair a is a pair number for identification. Each twisted pair a has a conductor f as shown in FIG.
It is formed by twisting two insulating strands h each having an insulating coating g applied thereto.

The dimensions and materials of each part are as follows. Conductor f: A stranded conductor obtained by twisting seven tin-plated copper wires having an outer diameter of 0.127 mm, and a standard outer diameter of 0.38 mm. Insulation coating g: Polyethylene (fluorine resin, polyvinyl chloride, etc. may be used) Insulation wire h: Outer diameter 0.70 mm Pair twisted wire a: Insulation wire h is twisted left-handed and twisted many pairs b: The center layer is twisted left, the middle layer is twisted right,
The outermost layer is left-handed. Intervening layer c: Dielectric tape is horizontally wound with 1/4 wrap. Shield layer d ₁ : 25 μm thick aluminum-laminated polyester tape is horizontally wound in a 1/4 wrap. Shield layer d ₂ : outer diameter 0.12 mm, tin-plated annealed copper wire 5
Braided with 16 books. Sheath e: 0.8 mm thick flexible polyvinyl chloride

[Example 1] The twist pitch of the twisted pair a was set to 2
5 mm and 27 mm are selected, the twist pitch of the center layer (pair numbers 23 to 25) of the multi-pair assembled twisted wire b is 37 mm, the twist pitch of the intermediate layer (pair numbers 15 to 22) is 90 mm, and the outermost layer (pair number 1). 14), the twist pitch of 100 mm is set, the total twist rate Yo of the outermost layer is made larger than the total twist rate Yi of the intermediate layer and the center layer, and the thickness of the intervening layer c is 0.2 m.
A polyester non-woven tape having a width of m and a width of 25 mm was horizontally wound with a 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 1 were obtained. The characteristic impedance difference is 6.0Ω, the propagation delay time difference is 0.06 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
s / m was satisfied with a sufficient margin. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Embodiment 2] The twist pitch of the twisted pair a is set to 2
5mm and 27mm are selected, and the twist pitch of the center layer of the multi-pair assembled twisted wire b is 30mm, and the twist pitch of the intermediate layer is 75m.
m, the twist pitch of the outermost layer is 124 mm, and the total twist ratio Yo of the outermost layer is the total twist ratio Yi of the middle layer and the center layer.
The same, and the intervening layer c has a thickness of 0.2 mm and a width of 25 m.
The polyester non-woven fabric tape of m was horizontally wound with 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 2 were obtained. The characteristic impedance difference is 6.0Ω, the propagation delay time difference is 0.09 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
It satisfied s / m. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Embodiment 3] The twist pitch of the twisted pair a is set to 2
5mm and 27mm are selected, and the twist pitch of the center layer of the multi-pair assembled twisted wire b is 37mm, and the twist pitch of the intermediate layer is 90m.
m, the twist pitch of the outermost layer is 100 mm, and the total twist rate Yo of the outermost layer is the total twist rate Yi of the middle layer and the center layer.
It is made larger, and the thickness of the intervening layer c is 0.1 mm and the width is 25.
mm non-woven polyester tape was wound horizontally with a 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 3 were obtained. The characteristic impedance difference is 6.0Ω, the propagation delay time difference is 0.10 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
It satisfied s / m. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Example 4] The twist pitch of the twisted pair a is selected to be 15 mm and 17 mm for the outermost layer and 25 mm and 27 mm for the middle layer and the center layer, and the twist pitch of the center layer of the multi-pair assembled twisted wire b is 30 mm. , The twist pitch of the intermediate layer is 75 mm, the twist pitch of the outermost layer is 124 mm, the total twist rate Yo of the outermost layer is larger than the total twist rate Yi of the intermediate layer and the central layer, and the thickness of the intervening layer c is 0. A polyester non-woven tape having a width of 1 mm and a width of 25 mm was horizontally wound with a 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 4 were obtained. The characteristic impedance difference is 6.0Ω, the propagation delay time difference is 0.08 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
The s / m was satisfied with a margin. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Comparative Example 1] The twist pitch of the twisted pair a is 2
5mm and 27mm are selected, and the twist pitch of the center layer of the multipair twisted pair b is 27mm and the twist pitch of the intermediate layer is 68m.
m, the twist pitch of the outermost layer is 124 mm, and the total twist ratio Yo of the outermost layer is the total twist ratio Yi of the middle layer and the center layer.
It is made smaller, and the thickness of the intervening layer c is 0.2 mm and the width is 25.
mm non-woven polyester tape was wound horizontally with a 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 5 were obtained. The characteristic impedance difference is 6.0Ω, the propagation delay time difference is 0.23 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
s / m could not be satisfied. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Comparative Example 2] The twist pitch of the twisted pair a is 2
5mm and 27mm are selected, and the twist pitch of the center layer of the multi-pair assembled twisted wire b is 37mm, and the twist pitch of the intermediate layer is 90m.
m, the twist pitch of the outermost layer is 100 mm, and the total twist rate Yo of the outermost layer is the total twist rate Yi of the middle layer and the center layer.
It is made larger, and the thickness of the intervening layer c is 0.05 mm and the width is 2
A 5 mm polyester non-woven tape was wound horizontally with a 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 6 were obtained. Characteristic impedance difference is 1
1.0Ω, the propagation delay time difference is 0.33 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
s / m could not be satisfied. Also, when the pressure contact type connector was attached to the completed cable, it could be attached without any problems.

[Comparative Example 3] The twist pitch of the twisted pair a is 2
Select 5 mm and 27 mm, and increase the outer diameter of the outermost pair of twisted pair insulation wires to 0.76 mm (the outer diameter of the middle and center layer twisted pair insulation wires is 0.70 mm) , The twist pitch of the central layer of the multi-pair assembled twisted wire b is 27 mm, the twist pitch of the intermediate layer is 68 mm, and the twist pitch of the outermost layer is 124 mm.
As the intervening layer c, a polyester non-woven tape having a thickness of 0.05 mm and a width of 25 mm was horizontally wound with 1/4 wrap.

For all twisted pairs of the completed cable,
When the characteristic impedance Z ₀ and the propagation delay time Tpd were measured, the results shown in Table 7 were obtained. The characteristic impedance difference is 8.0Ω, the propagation delay time difference is 0.09 ns / m,
ANSI X3 HIPPI standard 12Ω, 0.13n
It satisfied s / m. However, when I tried to attach the insulation displacement connector to the completed cable, it was difficult to align it because the outer diameter of the insulation wire was different, and I could not attach it.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

[Table 7]

[0042]

As described above, according to the present invention, there are few variations in the characteristic impedance and propagation delay time of each twisted pair in the same cable, the uniformity of each signal transmission line is excellent, and the terminal processability is excellent. It is possible to obtain a good multi-pair shielded cable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a multi-pair shielded cable.

FIG. 2 is a perspective view showing an example of a twisted pair wire.

[Explanation of symbols]

a: twisted pair wire b: multi-pair set twisted wire c: intervening layers d ₁ and d ₂ : shield layer e: sheath f: conductor g: insulating coating h: insulating element wire

Claims (1)

[Claims] 1. A multi-pair shielded cable in which a large number of twisted pair wires each having the same structure as an insulating element are twisted into a plurality of layers to form a multi-pair twisted wire, and a shield layer is provided on the outer periphery of the twisted pair wire. An intervening layer made of a dielectric material and having a thickness of 0.1 mm or more is provided between the twisted wire and the shield layer, and the total twisting ratio Yo of the twisted pair and the outermost layer of the twisted pair located in the outermost layer of the multipair twisted pair The total twist ratio Yi of the twisted pair that is not located is
A multi-pair shielded cable characterized by ≧ Yi.