JPH1196837A - Communication cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication cable having reduced propagation delay time difference and reduced cross talks by constituting the same of plural pair twisted wires for all equal pair twist pitches and without shield, and devising the arrangement method of the pair twisted wires or the twist pitch. SOLUTION: A communication cable is formed by constituting pair-twisted wires 2 through twisting insulator-coated insulated conductors 1 and circularly arranging plural pair twisted wires 2. The pair twisted wires 2 are respectively twisted in an equal pitch and are arranged, so that all the distances from the centers of the pair twisted wires 2 to the center of a cable cross section center are equal and the pair twisted wires 2, 2 are brought into contact with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-speed data transmission,
In particular, the present invention relates to an improvement of a communication cable formed by collectively twisting a plurality of twisted pairs used for an interface for high-speed data transmission such as SCSI (small computer systems interface). .

[0002]

2. Description of the Related Art As a communication cable used for an interface for high-speed data transmission, there is a cable in which a plurality of twisted pair wires are collectively twisted. By the way, the interface for high-speed data transmission mainly uses a method of transmitting signals in parallel. In this method, since a plurality of bundled twisted pairs transmit signals at the same time, it is desirable that the signal arrival time of each twisted pair at the receiving end be the same, and the difference in delay time between each twisted pair. Should be smaller. More specifically, two or more twisted pairs of twisted wires are selected as a crosstalk reducing measure, and each twisted pair is arranged so that twisted pairs of the same length twisted pitch are not adjacent to each other. Further, as a measure for reducing the delay time difference, the difference in the twisting ratio (the ratio of the conductor length of one pitch to the twist pitch) of the twisted pair wire having two or more selected pitches is made as small as possible. Also, in order to satisfy both reduction measures, after applying a shield layer by covering each of a plurality of twisted pairs having the same twist pitch with a metal tape or a metal braid,
There is also a method of cabling.

[0003]

When the difference between the maximum value and the minimum value of the propagation delay time of each signal line (twisted pair) is allowed up to about 0.2 ns / m in the signal transmission method, However, when a high-speed signal of 100 Mbps or more is transmitted in parallel, it is required to further reduce the difference in propagation delay time. Therefore, in order to reduce the propagation delay time difference,
It is conceivable to make all the twisted pitches of each signal line the same, but this has the problem that the crosstalk characteristics are significantly deteriorated. Further, if a shield layer is provided on signal lines having the same pitch to prevent crosstalk, there is a problem that the outer diameter of the cable increases, the cable becomes heavy, and the cost increases.

An object of the present invention is to provide a method for arranging a plurality of untwisted twisted pairs, all of which have the same twist pitch, and have no shield, in order to reduce the difference in propagation delay time in view of the above-mentioned problems. Or by devising the twist pitch,
An object of the present invention is to provide a communication cable with reduced crosstalk.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 comprises a twisted pair of core wires each having a conductor coated with an insulator. In a communication cable in which a plurality of the twisted pair wires are arranged in a circular shape, the twisted pair wires are respectively twisted at an equal pitch, and the distance between the center of all the twisted pair wires and the center of the cable cross section is increased. It is characterized by being arranged so that the distances are equal and the twisted pair wires are in contact with each other.

According to a second aspect of the present invention, in the first aspect, the twist pitch p of the twisted pair wire and the outer diameter of the core wire constituting the twisted pair wire are d, and Where p / d ≦
It has a relationship of 25.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a plurality of insulated wires for supplying power are provided in a circle formed by arranging a plurality of twisted pairs in a circular shape. Are arranged.

According to a fourth aspect of the present invention, in the third aspect, a twisting direction in which a plurality of twisted pairs are bundled is opposite to a twisting direction in which a plurality of insulated wires are bundled. It is assumed that.

Further, the invention described in claim 5 is the third invention.
Alternatively, in the invention described in Item 4, the insulator forming the core wire of the twisted pair wire and the insulator forming the insulated wire have substantially the same dielectric constant.

Next, each claim will be described. First,
As in claim 1, when all the twisted pairs are twisted at the same pitch, and when the twisted pairs are grouped so that the distance to the center of the cable cross section is equal, all the twisted pairs are used. Are arranged on one circumference of the cable cross section, the conductor lengths of a plurality of twisted pair wires become equal, and the difference in propagation delay time can be reduced. As described above, the reason why the twisted pair wires are arranged on one circumferential layer and are not dispersed in two or more concentric layers is that the inner layer and the outer layer are dispersed in two or more layers. The conductor length is different between layers. In this case, it is possible to adjust the conductor length by reducing the collective twist pitch of the inner layer and making the collective twist pitch of the outer layer larger than that of the inner layer. This is because it is difficult to reduce the propagation delay time difference to 0.1 ns / m or less in the case of a double layer.

Further, the propagation delay time τ greatly depends on the dielectric constant ε around the twisted pair, and can be expressed by τ ^{1 /} 2ε1 ^{/ 2.} Desirably, the rates are equal for all twisted pairs. Therefore, the adjacent twisted pair wires are arranged without any gap so as to always contact. This is because if there is a gap between the twisted pair wires and this portion is filled with an inclusion, the dielectric constant of the surrounding of the twisted pair wire that contacts this inclusion changes, and the propagation delay time changes.

The invention according to claim 2 has been achieved as a result of intensive experimentation. From the viewpoint of propagation delay time, it is considered that the smaller the twist pitch, the longer the propagation delay time, which is disadvantageous in transmission characteristics. However, in the case of parallel transmission using a multi-pair cable, when the transmission distance is short, the propagation delay time difference becomes more important than the propagation delay time. Regarding this point, paying attention to the twist pitch of the twisted pair, all twisted pairs are twisted at the same pitch and arranged on one concentric circle so that the distance to the center of the cable section becomes equal. In this case, the difference in propagation delay time is considered to be due to the difference in the effect of each twisted pair from the dielectric such as the presser-wound tape and filled inclusions around each twisted pair. Can be Here, as the twist pitch of the twisted pair wire is smaller, the volume occupied by the insulator used for insulating coating per unit length of the twisted pair wire becomes larger, so that the influence from dielectrics other than the insulator coated conductor is reduced. It can be considered that the propagation delay time difference (variation) can be reduced.

This was examined experimentally. In the cable used in the experiment, 20 pairs of twisted wires each composed of a core wire having an insulation outer diameter of 0.5 mm and having a conductor coated with a crosslinked polyethylene material were arranged concentrically, and the inside of the concentric circle was filled with inclusions. At this time, the twist pitch is the same for all 20 strands, and 5 mm, 9 mm,
There were six types, 17 mm, 23 mm, 30 mm, and 50 mm. Also, the insulation outer diameter of the core wire was changed to 0.7 mm, and the twist pitch was 7 mm, 9 mm, 17 mm, 23 mm, 30 mm.
20 pairs of cables of mm, 50 mm, 80 mm, and 100 mm were produced. Furthermore, the insulation outer diameter of the core wire was changed to 1.0 mm, and the twist pitch was 9 mm, 17 mm, 23 mm, and 23 mm.
mm, 30 mm, 50 mm, 80 mm, 100 mm, 1
Twenty pairs of cables having a length of 50 mm were produced. With respect to these cables, the dispersion of the propagation delay time of 20 pairs of twisted pairs was measured. The results are shown in FIG.

From FIG. 4, regardless of the insulation outer diameter of the core wire,
It can be seen that the larger the twist pitch, the larger the variation (standard deviation σ) of the propagation delay time. FIG. 5 shows the result of rewriting the relationship in FIG. 4 and setting the horizontal axis to p / d (p: twist pitch, d: insulating outer diameter). From FIG. 5, it can be seen that as p / d decreases, the variation in propagation delay time decreases. This result can be approximately expressed by the following empirical formula. σ = 0.00999 + 0.0186 · log (p /
d) On the other hand, that the propagation delay time difference is 0.1 ns / m or less means that the variation width of the propagation delay time of a plurality of twisted pair wires in the same cable is 0.1 ns / m or less. By the way, in the case of the normal distribution, 99.7% of the data falls within the range of +/− 3σ with respect to the average value. Therefore, if the value obtained by multiplying the standard deviation σ by 6 with respect to the variation of the propagation delay time is smaller than 0.1 ns / m, 0.1
Most of the data may fall within the width of ns / m, and the propagation delay time difference may be 0.1 ns / m or less. For that purpose, σ may be 0.016 ns / m or less, and p / d ≦ 25 from FIG. Also,
Regarding the cable used for measuring the above propagation delay time,
When the near-end crosstalk attenuation was measured, when the p / d was smaller than 25, the level of crosstalk between all twisted pairs was 10 Mb.
The category 3 level (international standard: ISO / IEC11801) near-end crosstalk standard that guarantees the transmission speed of the ps class was satisfied.

In the case where a twisted pair for signal transmission and a plurality of insulated wires for power supply are combined as in claim 3, the insulated wire is formed in a circle formed by the twisted pair. Put it in the space. In this case, as in claim 4,
The twisting direction of the plurality of insulated wires and the twisting direction of bundling the pair of twisted wires are opposite to each other. The reason for the opposite direction is that if the direction is the same, the insulated wire will drop irregularly between the twisted pair wires, causing the dielectric constant around the twisted pair wire to become non-uniform, causing a variation in the delay time. .

Further, it is desirable that the insulator of the insulated wire for power supply and the insulator of the signal line have the same dielectric constant. The reason is that even when multiple twisted pairs of the same pitch are twisted, if the dielectric constant of the insulator of the insulated wire and the dielectric of the twisted pair of wires are different from each other, the wires will be in a collectively twisted state. This is because the distances between the individual twisted pair wires and the insulated wires are not all equal, and the equivalent permittivity around each twisted pair wire varies, and the propagation delay time varies.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view of an embodiment of a communication cable according to the present invention. In FIG. 1, 1 is a core wire in which a tin-plated annealed copper wire is coated with crosslinked polyethylene, 2 is a twisted pair wire, 3 is a plastic tape press-wrap, 4 is a shield layer (aluminum-PET laminated tape 4a + aluminum braid 4b), 5 is A sheath 6 made of PVC is a filling inclusion. In the present embodiment, the characteristic impedance is finally 1
The twisted pair wire 2 in which the core wire 1 is twisted so as to be 00Ω,
Ten pieces are placed in a circular shape on the filling inclusions 6 such as a thermoplastic resin and the like, and a plastic tape press winding 3 is applied. Then, an aluminum-PET laminated tape 4a is wrapped as a shielding layer 4. Wound, and aluminum braid 4b on it
And finally covered with a sheath 5 made of PVC. In addition, by appropriately setting the diameter of the filling inclusion 6,
The ten twisted pair wires 2 were arranged without gaps and were not overlapped with each other. In this embodiment, by changing the core conductor diameter, the core outer diameter d, and the twisting pitch p of the twisted pair wire 2, the sample Nos.
No. 4 communication cables were prepared, and the delay time difference (ns / m) of these samples was measured. Table 1 shows the detailed size and measurement results of each sample. As can be seen from Table 1, p / d ≦ 2
Each sample satisfying the condition of No. 5 was able to realize a delay time difference of less than 0.1 ns / m.

[0018]

(Embodiment 2) Samples Nos. 5 and 6 were prepared in which a plurality of power lines composed of insulated electric wires for power supply were arranged in the portion of the filling inclusions of Embodiment 1. As shown in FIG. 2 (a), the sample of sample No. 5 is a power source bundle 8 in which a seven-core power source wire 7 in which tinned soft copper wire is coated with crosslinked polyethylene is twisted at the filling inclusion portion of the sample of sample No. 1. Was placed. Further, as shown in FIG. 2 (b), the sample of sample No. 6
A power line bundle 10 in which eight lines of power lines 7 coated with cross-linked polyethylene were twisted around a polyethylene rod 9 having a diameter of φ was arranged. In the samples of Sample Nos. 5 and 6, the core 1 serving as the signal line and the insulating coating material of the power supply line 7 are made of the same material.
In addition, the set twist direction of the ten twisted pair wires 2 and the set twist direction of the power supply line 7 were set to be opposite. The delay time difference (ns / m) was measured for these samples. Table 2 shows the detailed size and measurement results of each sample. As can be seen from Table 2, Sample No. 5,
The sample No. 6 had a slightly larger delay time difference than the samples Nos. 1 and 3, but could realize a delay time difference smaller than 0.1 ns / m.

[0020]

FIG. 3 shows the measurement result of the relationship between the transmission frequency and the near-end crosstalk attenuation for the sample No. 6. As can be seen from FIG. 3, the near-end crosstalk attenuation of this sample is smaller than the category-3 level (international standard: ISO / IEC11801) at 0.3 to 300 MHz, and is a sufficiently satisfactory value.

[0022]

According to the present invention, there is an excellent effect that the twist pitch can be made equal, the propagation delay time difference can be made 0.1 ns / m or less, and the crosstalk can be sufficiently reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a communication cable according to the present invention.

FIGS. 2A and 2B are cross-sectional views of other embodiments.

FIG. 3 is a diagram showing a relationship between a frequency and a near-end crosstalk attenuation amount in the embodiment shown in FIG. 2 (b).

FIG. 4 is a diagram showing a relationship between a twist pitch and a standard deviation σ of propagation delay time in the present invention.

FIG. 5 is a diagram showing a relationship between p / d and a standard deviation σ of propagation delay time in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core wire 2 Twisted wire 3 Plastic tape retainer winding 4 Shield layer 4a Aluminum pet tape 4b Aluminum braid 5 Sheath 6 Filling inclusion 7 Power line 8, 10 Power line bundle 9 Polyethylene rod

Claims (5)

[Claims] 1. A communication cable in which a pair of twisted core wires each comprising a conductor covered with an insulator are twisted to form a twisted pair, and a plurality of the twisted pairs are arranged in a circular shape. So that the distance between the center of all twisted pair wires and the center of the cable section is equal.
A communication cable, wherein the twisted pair wires are arranged to be in contact with each other. 2. The twist pitch of the twisted pair wire is p, and the outer diameter of the core wire constituting the twisted pair wire is d, and p / d ≦ 25 between p and d.
2. The communication cable according to claim 1, wherein the communication cable has the following relationship. 3. The communication cable according to claim 1, wherein a plurality of insulated wires for power supply are arranged in a circle formed by arranging a plurality of twisted pair wires in a circular shape. Bull. 4. A twisting direction for bundling a plurality of twisted pair wires,
4. The communication cable according to claim 3, wherein the twisting directions for bundling the plurality of insulated wires are opposite. 5. The communication cable according to claim 3, wherein the insulator forming the core wire of the twisted pair and the insulator forming the insulated wire have substantially the same dielectric constant.