JPH07288047A - Communication cable - Google Patents

Abstract

PURPOSE:To reduce attenuation while holding sufficient proximity crosstalks characteristics to provide superior frequency characteristics in high speed data transmission and high frequency transmission of aboat 100Mbps. CONSTITUTION:A communication cable 10 is provided with an integrated twisted layer 12 and a shield layer 14. The integrated twisted layer 12 is formed by twisting a plurality of pairs 16 at different twisting pitches. An insulation layer 34 is provided between the integrated twisted layer 12 and the shied layer 14 so that ratio RIs/Ic of impedance Is between a core in two-core conductors constituting all the pairs 16 and the shield layer 14, to characteristic inpedance Ic between two-core conductors constituting all the pairs 16 is 0.76 R 0.80. The insulation layer 34 is formed from two unwoven fabrics 36 wrapped around the integrated twisted layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication cable used for high-speed data communication or the like, and more particularly to a communication cable formed by covering a shield layer with a collective twist layer formed by collectively twisting a plurality of pairs. It is about improvement.

[0002]

2. Description of the Related Art As a communication cable used in a regionally limited area such as in an office or a building,
Generally, an indoor line or a premises cable mainly transmitting an audio signal, or a communication cable formed by twisting a plurality of pairs developed for a computer network (LAN) up to 20 Mbps is used. In this case, in order to deal with multimedia, when an image signal is transmitted by these communication cables, reception of a desired electromagnetic signal is impaired due to unnecessary electromagnetic signals or electromagnetic disturbance (hereinafter referred to as EMI). In order to prevent it, it is actually necessary to apply a shield layer to the communication cable,
In that case, there is a problem that the high-frequency characteristics of 100 MHz or more, particularly the value of the attenuation amount becomes large.

In recent years, there has been an increasing demand for high-speed data transmission of about 100 Mbps even in premises wiring systems such as offices and commercial buildings. For communication cables used for such high-speed data communication, see E
IA / TIA (American Electronics Industry Association / American Telecommunications Industry Association) defines the standard. Especially, for electric wires that can be used for data transmission up to 100 Mbps, a unit formed by twisting a plurality of pairs in category 5. The minimum performance standard is stipulated in the performance specifications for unshielded unit type cables that are made by twisting together.

The standard by EIA / TIA (American Electronics Industry Association / American Telecommunications Industry Association) basically assumes a communication cable having no shield layer, but when actually transmitting an image signal. As already mentioned, EM
As a countermeasure against I, it is essential to provide a shield layer on the communication cable to reduce the influence of external noise.

However, when the shield layer is provided in this way, a capacitive impedance is usually generated between the conductor of the insulated wire forming the pair and the shield layer, and this becomes a kind of resistance, so that the shield layer is provided. There is a problem that the amount of attenuation becomes larger than that of a communication cable that does not. Therefore, conventionally, the conductor resistance of the insulated wires forming the pair is increased to reduce the conductor resistance, or the insulation coating of the insulated wires is increased in thickness or the insulation coating is formed of foamed resin or the like. Therefore, the dielectric constant has been lowered to lower the capacitance.

[0006]

However, in the conventional communication cable formed by twisting a plurality of pairs, in a high frequency of about 100 Mbps or more, for example, in a computer network (ATM LAN) in an asynchronous transfer mode. It is not possible to obtain sufficient characteristics such as attenuation around 300 MHz, characteristic impedance, near-end crosstalk, and EMI characteristics, which are necessary for high-speed data communication of about 150 Mbps and high-frequency communication of image communication such as cable television (CATV). It was

Of particular concern is the frequency characteristic of attenuation, which is one of the conventional communication cables in which a plurality of pairs are twisted together and a shield layer is applied, and which has an outer diameter large enough to fit in a modular jack. Electric wire (maximum outer diameter 0.9
When it is limited to 65 mm), the EIA / T already mentioned
It has been difficult to satisfy the attenuation amount defined by the IA (American Electronics Industry Association / American Telecommunications Industry Association) category 5 standard.

In this case, as a means for suppressing the amount of attenuation, an insulated wire having an insulating coating made of foamed resin is used, and the two cores of insulated wire are twisted together at a long twist pitch such that the foamed resin is not crushed to form a pair. It is possible that
If this is done, the amount of attenuation will be reduced, but the amount of near-end crosstalk attenuation specified in the category 5 standard cannot be satisfied.

An object of the present invention is to avoid the above-mentioned drawbacks and to provide a communication cable in which a shield layer is applied to a collective twist layer formed by collectively twisting a plurality of pairs, and 100 Mbps.
To provide a communication cable capable of suppressing an increase in attenuation and obtaining good frequency characteristics while maintaining a sufficient near-end crosstalk characteristic even in the case of supporting the above high-frequency high-speed data communication and high-frequency communication. It is in.

[0010]

According to the present invention, as means for solving the above-mentioned problems, a plurality of pairs formed by twisting insulation-coated two-core conductors have different twist pitches. In a communication cable comprising a collective twisted layer formed by collective twisting and a shield layer applied to the collective twisted layer, one of two core conductors forming all pairs and the shield layer Impedance Is between and the characteristic impedance I between the two core conductors that make up all pairs
The ratio R (Is / Ic) with respect to c is 0.76 ≦ R ≦ 0.80
Thus, a communication cable is provided, in which an insulating layer is provided between the collective twisted layer and the shield layer.

Here, the ratio R (Is / of the impedance Is between one of the two core conductors forming the pair and the shield layer and the characteristic impedance Ic between the two core conductors forming the pair. The reason why Ic) is used as an index is that this value serves as a standard for knowing the influence of the shield layer on the conductor of the insulated wire. However, in this case, the impedance ratio R
When (Is / Ic) exceeds 0.80, the outer diameter of the communication cable becomes significantly larger than the outer diameter of the conductor, and problems arise in practicality such as wiring and transportation.
It is set to 0.80.

[0012]

In this way, the ratio R of the impedance Is between one of the two core conductors forming the pair and the shield layer and the characteristic impedance Ic between the two core conductors forming the pair is R.
(Is / Ic) is 0.76 ≦
If an insulating layer is provided between the collective twisted layer and the shield layer so that R ≦ 0.80, the insulation distance between the shield layer and the insulated wire forming the pair becomes large, and the shield layer gives the conductor. Since the influence can be reduced, good frequency characteristics can be obtained by suppressing the amount of attenuation even in a high frequency band, and in particular, it is a category 5 standard by EIA / TIA (American Electronics Industry Association / American Telecommunications Industry Association). The amount of attenuation specified in the standard can be sufficiently satisfied, and the amount of attenuation can be reduced while supporting high-speed data communication and high-frequency communication.

In particular, in this case, since the attenuation amount is reduced by the insulating layer, it is not necessary to lengthen the twist pitch of the pair, and a twist pitch suitable for improving the near-end crosstalk characteristic can be selected. While maintaining sufficient near-end crosstalk characteristics,
Attenuation can be reduced to obtain good frequency characteristics,
It is possible to simultaneously satisfy all the requirements of electrical characteristics (attenuation, characteristic impedance, near-end crosstalk characteristic) defined by the EIA (American Electronics Industry Association) standard. In addition, since the amount of attenuation is reduced without increasing the thickness of the insulation coating of the insulated wire, the outer diameter of the insulated wire can be set small, so a practical outer diameter that can be fitted into the modular jack. The amount of attenuation can be reduced even when using an insulated wire having

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a communication cable 10 of the present invention. The communication cable 10 includes an aggregate twist layer 12 and an aggregate twist layer 12. And the applied shield layer 14.

As shown in FIG. 1, the collective twist layer 12 is formed by collectively twisting a plurality of pairs 16. Note that FIG.
In the example shown in FIG.
Through 16D, but any other suitable number may be used if desired.

Each pair 16 is formed by twisting two insulated wires 18 as shown in FIG. As shown in FIG. 2, each insulated wire 18 is composed of a two-core conductor 20 that is insulation-coated with an insulator 22. As the conductor 20, for example, annealed copper wire or the like can be used, and
The insulator 22 can be formed of polyethylene or the like, and more specifically, it is preferable to use foamed polyethylene because the dielectric constant can be lowered.

These four pairs 16A to 16D are twisted so that adjacent pairs 16 have different twist pitches so that near-end crosstalk does not occur. Therefore, for example, the twist pitch P _A of one pair 16A of the adjacent pairs 16A and 16B shown in FIG. 1 is different from the twist pitch P _B of the other pair 16B, which means that the pair 16B and the pair 16C, 16C are paired.
The same holds between C and pair 16D, and between pair 16D and pair 16A. That is, the twist pitch of pair 16A is P _A , pair 16B
If the twist pitch of P is P _B , the twist pitch of 16C is P _C , and the twist pitch of 16D is P _D , then P _A ≠ P _B , P
_B ≠ P _C , P _C ≠ P _D , P _D ≠ P _A always hold. In the present invention, the twist pitch of the pair 16 means each pair 1
It means a pitch at which two insulated electric wires 18 constituting 6 are twisted together.

In the embodiment shown in FIG. 1, the shield layer 14 is composed of a double-sided aluminum PET tape 24 and a braid 26 provided on the double-sided aluminum PET tape 24. As shown in FIG. 3, the double-sided aluminum PET tape 24 is formed by joining aluminum tapes 30 on both sides of a polyester tape 28 by an appropriate joining means such as an adhesive, and as shown in FIG. It is wrapped around the twisted layer 12 to form a shield layer 14. In addition, the braid 26 is generally formed of a metal material such as copper or aluminum. Since the shield layer 14 is provided in this manner, the influence of external noise can be reduced as a measure against EMI. The shield layer 14 is not limited to the one made of the double-sided aluminum PET tape 24 and the braid 26, and another shield layer 14, for example, made of a metal pipe may be used. Further, in FIG. 1, reference numeral 32 denotes a sheath which is further covered on the shield layer 14 to protect the collective twisted layer 12 and the shield layer 14 from the external environment. The sheath 32 is made of, for example, polyvinyl chloride. Can be formed.

Further, the communication cable 10 of the present invention is shown in FIG.
As shown in, the ratio R between the impedance Is between one core of the two-core conductors 20 forming the pair 16 and the shield layer 14 and the characteristic impedance Ic between the two-core conductors 20 forming the pair 16 is shown. The insulating layer 34 is provided between the collective twist layer 12 and the shield layer 16 so that (Is / Ic) is 0.76 ≦ R ≦ 0.80 regardless of which pair 16.

This is to reduce the influence of the shield layer 14 on the conductor 20 of the insulated wire 18 and reduce the amount of attenuation. That is, when the insulating layer 34 is provided in this way,
Since the insulation distance between the insulated wire 18 forming the pair 16 and the shield layer 14 can be increased, the attenuation amount can be reduced and a good frequency can be obtained, as will be understood from Comparative Examples and Experimental Examples described later. The characteristics can be obtained. In this case, in particular, the amount of attenuation defined by the EIA (American Electronics Industry Association) standard can be sufficiently cleared, and a good amount of attenuation can be obtained while supporting high-speed data communication and high-frequency communication.

Further, since the attenuation amount is reduced by the insulating layer 34 in this manner, it is not necessary to consider increasing the twist pitch of the pair 16 in order to reduce the attenuation amount, and if the twist pitch of the pair 16 is different. Since the twist pitch of the pair 16 suitable for improving the near-end crosstalk characteristic can be set, the attenuation amount can be reduced while maintaining the sufficient near-end crosstalk characteristic. Further, since the attenuation amount can be reduced without increasing the thickness of the insulating coating of the insulated wire 18,
The outer diameter of the insulated wire 18 can be set small, and the attenuation amount can be reduced even when the insulated wire 18 having a practical outer diameter that can be fitted into the modular jack is used.

In the embodiment shown in FIG. 1, the insulating layer 34 is a non-woven fabric 36 wrapped around the collective twisted layer 12.
Made of. The non-woven fabric 36 is formed, for example, by entwining fibers made of polyester or the like mechanically with a needle punch or the like or with an adhesive or the like. By providing the non-woven fabric 36, the insulation distance between the shield layer 14 and the insulated electric wire 18 is increased, so that the influence of the shield layer 14 on the conductor 20 of the insulated electric wire 18 can be reduced and the attenuation amount can be reduced. can do.

In the embodiment shown in FIG. 1, the impedance ratio R (Is / Ic) is 0.76≤R≤0.8.
In order to satisfy the condition of 0, two non-woven fabrics 36 are stacked, but the impedance ratio R (Is / I
The number of non-woven fabrics 36 does not matter as long as the insulation distance can be increased to the extent that c) is 0.76 ≦ R ≦ 0.80. For example, when another thick non-woven fabric 36 is used, even one Good.

This impedance ratio R (Is / Ic)
The value of "0.76≤R≤0.80" with respect to
This is a criterion for determining how much the insulation distance between the insulated wire 18 and the shield layer 14 that form 6 should be set, and the impedance ratio R (Is / Ic)
Is used as an index because it serves as a guide for determining the influence of the shield layer 14 on the conductor 20. Therefore, next, the impedance ratio R (Is / Ic) is set to "0.76.
The process of setting “≦ R ≦ 0.80” will be described with reference to comparative examples and experimental examples shown in Tables 1 and 2.

[0025]

[Table 1]

Table 1 shows the impedance ratio R (Is
/ Ic) is a comparison of the performance use of the communication cable 10 of two comparative examples set to investigate how much the attenuation can be sufficiently reduced and the experimental example included in the category of the present invention. It is shown. That is, as shown in Table 1, first, a conductor 20 made of a bare annealed copper wire having an outer diameter of 0.511 mm is coated with an insulating coating made of an insulator 22 made of expanded polyethylene. In the case of 1.10 mm, Comparative Example 2 and Experimental Example, an insulated electric wire 18 having an insulating coating with an outer diameter of 0.95 mm was formed, and the two insulated wires 18 were twisted together to form a pair 16.

Of these Comparative Examples and Experimental Examples, Comparative Example 1 was set to investigate how much the attenuation amount can be reduced by increasing the thickness of the insulator 22, and therefore, As shown in Table 1, the outer diameter of the insulated wire 18 is 1.10 as compared with other comparative examples 2 and experimental examples.
It is set as large as mm. On the other hand, in Comparative Example 2 and Experimental Example, the insulated wire 18 has a size (maximum of 0.965 mm) that can be fitted into the modular jack without increasing the outer diameter of the insulated wire 18.
When the outer diameter is within the range, the setting is made to investigate how much the attenuation amount can be reduced by increasing the insulation distance between the insulated wire 18 and the shield layer 14 forming the pair 16. It was done.

In this case, as shown in Table 1, the twisting pitch of the four pairs 16A to 16D forming the communication cable 10, that is, the pitch of twisting the two insulated wires 18 forming each pair 16 is shown in Table 1. For Comparative Example 1, 12 mm, 16 mm, 20 mm, 24
mm, and 14 mm, 16 mm, 18 mm, and 22 for Comparative Example 2 and the experimental example relating to the present invention, respectively.
mm, 4 pairs 16 to prevent near-end crosstalk
Were twisted at different twist pitches.

Further, in each of the comparative examples and experimental examples, as shown in Table 1, a shield composed of a double-sided aluminum PET tape 24 wrapped and a braid 26 applied on the double-sided aluminum PET tape 24. Apply layer 14,
Further, a communication cable 10 was manufactured by applying a sheath 32 made of polyvinyl chloride thereon.

Under the above conditions, as shown in Table 1, in Comparative Example 1, the shield layer 14 was directly applied onto the collective twisted layer 12 without the insulating layer 34 interposed, and in Comparative Example 2 and the experiment. In Example 1, an insulating layer 34 made of a non-woven fabric 36 having a thickness of 0.22 mm was wrapped and wrapped between the collective twist layer 12 and the shield layer 14. However, in Comparative Example 2, the number of the non-woven fabrics 36 that are the insulating layers 34 was set to one, and in Experimental Example 1 related to the present invention, the number of the non-woven fabrics 36 was set to two.
Is set so that the insulation distance between the insulated wire 18 and the shield layer 14 becomes larger. The experimental example 2 will be described later.

Next, with respect to the two comparative examples and the experimental example 1 shown in Table 1, the attenuation amounts at various frequencies were measured, and the results are shown in FIGS. 4 to 6.

That is, FIG. 4 shows the relationship between frequency and attenuation for Comparative Example 1 shown in Table 1, FIG. 5 shows the relationship between frequency and attenuation for Comparative Example 2, and FIG. 6 shows the experiment of the present invention. 5 shows the relationship between frequency and attenuation for Example 1. 4 to 6, the attenuation amount defined by the EIA (Electronic Industries Association) standard is also shown to facilitate comparison with the standard defined by this standard.

As can be seen from FIGS. 4 to 6, first,
The amount of attenuation obtained for Comparative Example 1 is, as shown in FIG.
The amount of attenuation is larger than that specified by the EIA (Electronic Industries Association) standard, and it is understood that this standard is not satisfied. It should be noted that this Comparative Example 1 corresponds to the above-mentioned conventional technique of increasing the thickness of the insulating coating, and therefore FIG. 4 proves that the conventional technique cannot satisfy the standard. To be At the same time, the insulated wire 18 used in Comparative Example 1 has an outer diameter of 1.10 mm.
Therefore, it is not possible to fit the modular jack into which only the insulated electric wire 18 having an outer diameter of 0.965 mm at the maximum can be inserted. As described above, in the communication cable 10 specified by this comparative example 1, although the thickness of the insulating coating is increased in order to reduce the attenuation amount, the attenuation amount cannot be sufficiently reduced and the purpose of use is In terms of, the range will be limited.

Next, the insulating layer 3 made of one piece of nonwoven fabric 36
Focusing on the amount of attenuation obtained for Comparative Example 2 in which No. 4 was applied, as shown in FIG. 5, although it is slightly below the upper limit of the amount of attenuation specified by the EIA (American Electronics Industry Association) standard, it is still sufficient. It is hard to say that the standards are satisfied with sufficient margin. This is because although the amount of attenuation can be reduced to some extent by providing the non-woven fabric 36 which is the insulating layer 34, the insulation distance between the insulated wire 18 and the shield layer 14 is not yet sufficiently wide. . As described above, from the data on Comparative Example 2 shown in FIG. 5, it is not possible to sufficiently satisfy the EIA (Electronic Industries Association) standard by simply providing the insulating layer 34. It can be seen that the insulating layer 34 needs to be applied.

Then, looking at the amount of attenuation obtained for the experimental example 1 of the present invention in which the insulating layer 34 composed of two non-woven fabrics 36 is further examined, as shown in FIG. 6, EIA ( It is clear that the amount of attenuation is well below the standard specified by the Electronic Industries Association of Japan and that the standard is satisfied with some margin. In this way, if the insulation distance between the insulated wire 18 and the shield layer 14 is appropriately set by providing the insulation layer 34, the shield layer 1 for the conductor 20 can be obtained.
It is possible to reduce the effect of 4 and sufficiently reduce the amount of attenuation.

In this case, the above-mentioned 2 is used as a guide for judging the influence of the shield layer 14 on the conductor 20.
For one comparative example and the experimental example 1 of the present invention, the impedance Is between one core of the two-core conductors 20 forming the pair 16 and the shield layer 14 and the two-core conductors 20 forming the pair 16 are compared. Ratio R (Is / I
c) was obtained for each pair 16 and the results are shown in Table 2.

[0037]

[Table 2]

As can be seen from Table 2, the impedance ratio R (Is / Ic) in the experimental example 1 of the present invention in which the attenuation amount can be sufficiently reduced is at least 0.76. The impedance ratio R (I
s / Ic) was 0.76 ≦ R. In this case, the impedance ratio R (Is / Ic) is 0.8.
If it exceeds 0, the outer diameter of the communication cable 10 becomes significantly larger than the outer diameter of the conductor 20 and a problem occurs in practicality such as wiring and transportation. Therefore, it is necessary to set 0.80 as the upper limit. is there. In this way, “0.76 ≦ R ≦ 0.
80 ”, and if the impedance ratio R (Is / Ic) is set within this range, a sufficient insulation distance between the insulated wire 18 and the shield layer 14 is secured. As a result, the influence of the shield layer 14 on the conductor 20 is reduced, and the attenuation amount can be sufficiently reduced as shown in FIG.

On the other hand, the impedance ratio R relating to Comparative Examples 1 and 2 in which the attenuation amount defined by the EIA (American Electronics Industry Association) standard could not be sufficiently satisfied.
Focusing on (Is / Ic), the pair 16 that satisfies R <0.76 is included. From this, even if the insulated electric wires 18 forming any of the pairs 16 are set to "0.76≤
R ≦ 0.80 ”so that the impedance ratio R (I
It is understood that the attenuation amount cannot be sufficiently reduced unless s / Ic) is set.

Regarding the communication cable 10 of Experimental Example 1 of the present invention shown in Table 1, a combination of all pairs 16 constituting the communication cable 10 (for example, a pair 16 twisted at a twist pitch of 14 mm and a pair of 16 mm). The near-end crosstalk attenuation amount in each frequency band was measured for a total of 6 combinations with the pair 16 twisted at the twist pitch, etc., and as shown in FIG. We have secured near-end crosstalk characteristics, especially
It was found that the near-end crosstalk attenuation amount defined by the EIA (American Electronics Industry Association) standard was sufficiently satisfied. This is because in the present invention, the pair 16 is twisted at different twist pitches, and in particular, since the insulating layer 34 reduces the attenuation amount without increasing the twist pitch of the pair 16, the pair 1
It is considered that the twist pitch of 6 can be set to a value suitable for improving the near-end crosstalk attenuation amount. As described above, in the present invention, the improvement of the near-end crosstalk characteristic and the reduction of the attenuation amount can be achieved at the same time.

In the embodiment shown in FIG. 1, the insulating layer 34 is formed from two non-woven fabrics 36, but the impedance ratio R (Is / Ic) is in the range of 0.76≤R≤0.80. If it is possible, another insulating layer 34 may be used. For example, as shown in Experimental Example 2 of Table 1, an insulating layer 34 formed by extruding a thermoplastic resin such as a fluororesin onto the aggregated twisted layer 12 in a pipe shape may be used. In this case, the thickness of the insulating layer 34 is 0.7.
By setting 0 mm, the impedance ratio R (Is
It has been confirmed by experiments that the above-mentioned value for / Ic) can be realized and the value of the attenuation amount sufficiently satisfies the standard value defined by EIA.

[0042]

According to the present invention, as described above, the impedance Is between one core of the two core conductors forming all the pairs and the shield layer and the two cores forming all the pairs. Ratio R (Is / Ic) with the characteristic impedance Ic between conductors
Is the optimum value obtained as a result of the experiment 0.76 ≦ R ≦
Since the insulating layer is provided between the collective twist layer and the shield layer so as to be 0.80, the insulation distance between the shield layer and the insulated wire is increased, and the influence of the shield layer on the conductor is reduced. Therefore, it is possible to suppress the amount of attenuation even in a high frequency band and obtain good frequency characteristics,
In particular, it can sufficiently satisfy the attenuation amount defined in the category standard of 5 by EIA / TIA (American Electronics Industry Association / American Telecommunications Industry Association), and is compatible with high-speed data communication and high-frequency communication. Can be reduced.

In particular, in this case, since the attenuation amount is reduced by the insulating layer, it is not necessary to lengthen the twist pitch of the pair, and the twist pitch suitable for improving the near-end crosstalk characteristic can be selected. While maintaining sufficient near-end crosstalk characteristics,
Attenuation can be reduced to maintain good frequency characteristics, and electrical characteristics (attenuation, characteristic impedance, near-end crosstalk characteristics) defined by the EIA (American Electronics Industry Association) standard
There is a real benefit of being able to satisfy all of the above requirements simultaneously.
In addition, since the amount of attenuation is reduced without increasing the thickness of the insulation coating of the insulated wire, the outer diameter of the insulated wire can be set small, so a practical outer diameter that can be fitted into the modular jack. There is also a practical benefit of being able to reduce the amount of attenuation even when using an insulated wire having

[Brief description of drawings]

FIG. 1 is a sectional view of a communication cable of the present invention.

FIG. 2 is a sectional view of a pair used in the present invention.

FIG. 3 is a cross-sectional view of a double-sided aluminum PET tape that constitutes a shield layer used in the present invention.

FIG. 4 is a plot diagram showing the relationship between frequency and attenuation obtained for Comparative Example 1 shown in Table 1.

5 is a plot diagram showing the relationship between frequency and attenuation obtained for Comparative Example 2 shown in Table 1. FIG.

FIG. 6 is a plot diagram showing the relationship between frequency and attenuation obtained for Experimental Example 1 of the present invention shown in Table 1.

7 is a plot diagram showing measured values of near-end crosstalk attenuation amounts obtained for all pairs of combinations in the communication cable of Experimental Example 1 of the present invention shown in Table 1. FIG.

[Explanation of symbols]

 10 Communication Cable 12 Collected Twisted Layer 14 Shield Layer 16 Pair 18 Insulated Wire 20 Conductor 22 Insulator 24 Double-sided Aluminum PET Tape 26 Braid 28 Polyester Tape 30 Aluminum Tape 32 Sheath 34 Insulating Layer 36 Nonwoven Fabric

Claims (1)

[Claims] 1. A collective twist layer formed by collectively twisting a plurality of pairs formed by twisting insulation-coated two-core conductors so that adjacent pairs have different twist pitches, and the collective twist layer is applied to the collective twist layer. In a communication cable including a shield layer, the impedance Is between one core of the two-core conductors forming all the pairs and the shield layer and the two-core conductors forming all the pairs. Characteristic impedance of
The ratio R (Is / Ic) with respect to c is 0.76 ≦ R ≦ 0.80
An insulating layer is provided between the collective twisted layer and the shield layer so that