JP4665023B2 - Metal cable for LAN - Google Patents

Description

  The present invention relates to a metal cable for a LAN that can support stable gigabit transmission.

  As an example of a LAN metal cable used in transmission of a communication network such as a LAN (Local Area Network), two cores in which an insulator 32 is coated on a conductor 33 are conventionally twisted as shown in FIG. A LAN metal cable 31 is known in which a pair of twisted wires 34 are assembled and a plurality of wires are assembled and then a first shielding layer 35, a second shielding layer 36, and a jacket 37 are applied.

  By the way, in a normally used metal cable for LAN as shown in FIG. 3, there are many cases in which four pairs have a basic structure because of the transmission system, and each pair has a twisted pair pitch in consideration of prevention of crosstalk between the pairs. Is done differently.

Factors affecting the transmission characteristics of such a LAN metal cable include characteristic impedance, return loss, insertion loss, and the like, all of which are attributable to capacitance. Capacitance is desirably as constant as possible over the entire length of the cable, when the electrostatic capacitance C, the relationship between the characteristic impedance Z ₀ and the capacitance is as in Equation 1.

  Here, L is a self-inductance, which is a substantially constant value. Therefore, if the characteristic impedance becomes constant, the capacitance becomes constant.

  Further, the expression of the return loss RL is as shown in Equation 2.

Here, R is a conductor resistance, and Z _in is an input impedance. When the input impedance approaches 100Ω, which is the standard value in all pairs, the return loss of all pairs can be improved.

  Furthermore, the insertion loss can be expressed by Equation 3 as follows, where the attenuation constant is α.

  Here, the value of the conductor resistance R varies depending on the twisted pair pitch, and usually increases as the twisted pair pitch is shorter. Therefore, the insertion loss (attenuation amount) can be reduced by adjusting the twisted pair pitch.

  By the way, as described above, conventionally, in a metal cable for LAN, in order to reduce crosstalk, the twisting pitches of a plurality of twisted wires are made different from each other, and the transmission characteristics of the twisted wire having the shortest twisting pitch are predetermined. It is designed to meet the standard value. In such a case, since the insertion loss varies depending on the twisted pair pitch, if the twisted pair pitch of the twisted pair wire is different, the insertion loss is also different in each paired twisted wire. In view of this, a device has been devised so that the insertion loss is constant in each pair of twisted wires (see, for example, Patent Document 1).

  On the other hand, the insertion loss increases as the pair twist pitch becomes shorter. Therefore, in order to reduce the insertion loss, the insulator may be thickened, but the problem arises that the outer diameter of the cable also increases. In order to solve such a problem, an insulating body is foamed to reduce the insulation outer diameter of the cable (for example, see Patent Document 2).

JP-A-11-176252 Japanese Utility Model Publication No. 6-7116

  As described above, conventionally, in order to improve the transmission characteristics of the metal cable for LAN, the twisting pitch of each twisted wire is made different and the insulator is foamed. However, the capacitance tends to be higher as the twisted pair pitch is shorter, and there is a problem that the capacitance is different between the twisted pairs.

  Also, as described above, the characteristic impedance is 100Ω as a standard value, but the characteristic impedance becomes lower as the twisted pair pitch becomes shorter. Therefore, even if one pair is designed and manufactured to be 100Ω, the other pair is 100Ω. There is also a problem of deviation from the above. Therefore, when the characteristic impedance deviates from 100Ω, there arises a problem that the return loss characteristic also deteriorates as shown in Equation 2.

  As described above, in a LAN metal cable, conventionally, the twisted pitch of each twisted wire is made different and the insulator is foamed. There was a limit to improving the characteristics.

  The present invention has been made in order to solve the above-described problems. By varying the twisted pitch of each twisted wire, the insulator is foamed and the foaming rate of the insulator is changed for each twisted wire. A metal cable for LAN having excellent transmission characteristics is provided.

In order to achieve this object, the first aspect of the twisted pair cable of the present invention includes a plurality of pairs of twisted pair wires in which two cores each coated with an insulator made of a foam layer are twisted together to form a pair. have, in pairs twisted pair twisted metal cable pitches are different from each other LAN that of, as varies respectively in accordance with the foaming rate is twisted pair pitch of the insulating foam layer in the plurality of pairs twisted wire, twisted pair pitch is short The foaming rate of the insulating foam layer is high .

Furthermore, the second aspect of the twisted pair cable of the present invention is characterized in that, in the first aspect, there are four pairs of twisted wires.

A third aspect of the twisted pair cable of the present invention is characterized in that, in the first or second aspect, the surface of the insulating foam layer is a non-foamed layer.

Furthermore, the fourth aspect of the twisted pair cable of the present invention is characterized in that, in the first to third aspects, the foam ratio of the insulating foam layer is different between 5 to 40% between each pair of twisted wires.

A fifth aspect of the twisted pair cable of the present invention is characterized in that, in the first to fourth aspects, the thickness of the non-foamed layer is 0.04 to 0.06 mm.

  According to the present invention, the foaming rate of the insulating foam layer is also different according to different twisted pitches in a plurality of twisted wires, so that the capacitance is constant over the entire length and the transmission characteristics are excellent. A metal cable for LAN can be provided.

  Hereinafter, preferred embodiments of a metal cable for LAN of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view of a metal cable for LAN according to the present invention. In FIG. 1, for convenience of explanation, illustration of a shielding layer and a jacket that are usually applied to a metal cable for LAN is omitted. In FIG. 1, a LAN metal cable 1 is formed by twisting two cores made of a conductor 3 covered with an insulator 2 into a pair of stranded wires, twisting four pairs of these stranded wires, 4b, 4c, and 4d. The twisted pair wires 4a to 4d have different twisted pair pitches. The twisted pair pitch is appropriately varied between 8 mm and 25 mm in each twisted pair wire. This is because when the twisted pair pitch is less than 8 mm, the twisting rate is increased, so that the insertion loss becomes excessive, and when it exceeds 25 mm, the stability of the twisted pair is impaired.

  The insulator 2 is composed of a foam layer 5 and a non-foam layer 6 on the surface of the insulator 2 as shown in FIG. When the insulator 2 is foamed, the strength is reduced. However, the strength reduction can be prevented by providing the non-foamed layer 6. The thickness of the non-foamed layer 6 is preferably 0.04 to 0.06 mm. If the thickness of the non-foamed layer 6 is less than 0.04 mm, the effect of preventing the strength from being reduced cannot be obtained. This is because the transmission characteristics to be obtained cannot be obtained.

  Here, in the metal cable for LAN according to the present invention, the foaming rate of the insulator 2 differs depending on the twisted pitch of each twisted wire. Specifically, the foaming rate of the insulator 2 is higher as the counter twist pitch is shorter. The foaming rate of the insulator 2 is preferably different between 5% and 40%. This is because if it is less than 5%, there is almost no foaming effect, and if it exceeds 40%, the strength of the entire insulator 2 is significantly reduced.

Next, a specific example is shown about the relationship between the twisted pair pitch and the foaming rate of the LAN metal cable of the present invention. In addition, as a comparative example, a metal cable for LAN (Comparative Example 1) in which an insulator is foamed but the foaming rate of each twisted pair is not different, and a LAN metal cable (Comparative Example 2) in which the insulator is not foamed ) Is also shown.
<Example 1>

  The outer periphery of a conductor having an outer diameter of 0.515 mm is coated with an insulator having a thickness of 0.170 mm, and two cores having an outer diameter of 0.855 mm are twisted to form a twisted pair. 4c and 4d) were produced by twisting four metal cables for LAN. The insulator is made of foamed polyethylene (foam skin polyethylene), and a non-foamed layer having a thickness of 0.04 mm is provided on the surface of the insulator.

  The twisted pitches of the four twisted wires are 11.4 mm for 4a, 13.5 mm for 4b, 15.6 mm for 4c, and 18.0 mm for 4d, and the foaming rate of the insulator according to this twisted pitch. Is changing. Specifically, the foaming rate is increased as the counter twist pitch is shorter.

In the metal cable for LAN of Example 1, as shown in Table 1, the electrostatic capacity of each twisted wire is 4.83 to 4.86 nF / 100 m, and the difference between the maximum value and the minimum value is 0.03 nF. / 100m. Moreover, the characteristic impedance in 100 MHz of each twisted pair was 99.9-100.1 (ohm), and all were very uniform. In addition, the return loss and insertion loss both showed excellent characteristics.
<Comparative Example 1>

  A metal cable for LAN having the same structure as in Example 1 was manufactured. The insulator in this cable is made of foamed polyethylene (foam skin polyethylene), and a non-foamed layer having a thickness of 0.04 mm is provided on the surface of the insulator. It was made the same with a twisted pair wire, and it was 16.5%.

In the LAN metal cable of Comparative Example 1, as shown in Table 1, the capacitance of each twisted wire is 4.63 to 4.85 nF / 100 m, and the difference between the maximum value and the minimum value is 0.22 nF. The variation was larger than that of Example 1. In addition, the characteristic impedance of each twisted pair at 100 MHz is 100.0 to 102.0Ω, which is deviated from 100Ω, and the difference between the maximum value and the minimum value is also 2.0Ω, which is a variation compared to Example 1. Was big. Moreover, both the return loss and the insertion loss were inferior to those of Example 1.
<Comparative example 2>

  The outer periphery of a conductor having an outer diameter of 0.515 mm is covered with an insulator having a thickness of 0.220 mm, and two cores having an outer diameter of 0.955 mm are twisted to form a twisted pair. 4c and 4d) were produced by twisting four metal cables for LAN. In this cable, the insulator is not foamed. Therefore, in order to ensure the necessary transmission characteristics, the thickness of the insulator must be increased, and a cable having an insulator thickness 0.050 mm thicker than that of Example 1 was produced.

  In the metal cable for LAN of the comparative example 2, as shown in Table 1, the capacitance of each twisted pair is 4.68 to 4.89 nF / 100 m, and the difference between the maximum value and the minimum value is 0.21 nF. There was also / 100 m, and the variation was very large compared to Example 1. In addition, the characteristic impedance of each twisted pair at 100 MHz is 105.1 to 107.0Ω, which is significantly different from 100Ω and also has a difference of 1.9Ω between the maximum value and the minimum value. The variation was very large. Further, the return loss and the insertion loss were both inferior to those of Example 1, and of course were inferior to those of Comparative Example 1.

As can be seen from Table 1, in Comparative Example 1 and Comparative Example 2, the insulation outer diameter is smaller in Comparative Example 1 in which the insulator is foamed than in Comparative Example 2 in which the insulator is not foamed. Although the transmission characteristics such as capacity and characteristic impedance are stable, in Example 1, the capacitance and characteristic impedance are more stable than those in Comparative Example 1, and the LAN metal cable of the present invention has excellent transmission characteristics. It became clear to have.
<Example 2>

  The outer periphery of a conductor having an outer diameter of 0.545 mm is covered with an insulator having a thickness of 0.170 mm, and two cores having an outer diameter of 0.885 mm are twisted to form a twisted pair. 4c and 4d) were produced by twisting four metal cables for LAN. The insulator is made of foamed polyethylene (foam skin polyethylene), and a non-foamed layer having a thickness of 0.04 mm is provided on the surface of the insulator.

  The twisted pitch of the four twisted wires is 10.4 mm for 4a, 12.4 mm for 4b, 14.5 mm for 4c, and 16.4 mm for 4d, and the foaming rate is higher as the twisted pitch is shorter. It is said.

In the LAN metal cable of Example 2, as shown in Table 2, the capacitance of each twisted pair wire is 4.71 to 4.78 nF / 100 m, and the difference between the maximum value and the minimum value is 0.07 nF. / 100m. Moreover, the characteristic impedance in 100 MHz of each twisted pair was 99.9-100.1 (ohm), and all were very uniform. Both return loss and insertion loss showed excellent characteristics.
<Comparative Example 3>

  A metal cable for LAN having the same structure as in Example 2 was manufactured. The insulator in this cable is made of foamed polyethylene (foam skin polyethylene), and a non-foamed layer having a thickness of 0.04 mm is provided on the surface of the insulator. The foaming rate was the same for each twisted pair, and was 23.0%.

In the metal cable for LAN of the comparative example 3, as shown in Table 2, the electrostatic capacity of each twisted pair is 4.41 to 4.78 nF / 100 m, and the difference between the maximum value and the minimum value is 0.37 nF. The variation was larger than that of Example 2. In addition, the characteristic impedance at 100 MHz of each twisted pair is 100.1 to 103.0Ω, which is deviated from 100Ω, and there is also a difference of 2.9Ω between the maximum value and the minimum value. The variation was large. Moreover, both the return loss and the insertion loss were inferior to those of Example 2.
<Comparative example 4>

  The outer circumference of the conductor having an outer diameter of 0.545 mm is covered with an insulator having a thickness of 0.220 mm, 0.210 mm, 0.205 mm, and 0.195 mm as the twisted wires 4a, 4b, 4c, and 4d, respectively, Two pieces of cores with 0.985mm, 0.965mm, 0.955mm, and 0.935mm are twisted together to form twisted wires 4a, 4b, 4c, and 4d. I made a cable. In this cable, the insulator is not foamed.

  In the metal cable for LAN of Comparative Example 4, as shown in Table 2, the capacitance of each twisted pair is 4.82 to 4.99 nF / 100 m, and the difference between the maximum value and the minimum value is 0.17 nF. There was also / 100 m, and the variation was very large compared to Example 2. Further, the characteristic impedance of each twisted pair at 100 MHz is 102.4 to 104.1Ω, which is greatly deviated from 100Ω and there is a difference of 1.7Ω between the maximum value and the minimum value, which is also compared with Example 2. The variation was very large. Further, the return loss and the insertion loss were inferior to those of Example 2 in all characteristics, and were inferior to those of Comparative Example 3.

  As described above, from the values of Example 2, Comparative Example 3 and Comparative Example 4 shown in Table 2, the LAN metal cable of the present invention has excellent transmission characteristics as well as the tendency in Example 1, Comparative Example 1 and Comparative Example 2. It became clear to have.

  As described above, according to the present invention, since the foaming rate of the insulator is increased as the twisted pitch is shorter with respect to the twisted pitch of the twisted wire, the capacitance, characteristic impedance, return loss, insertion loss, etc. It is possible to provide a LAN metal cable having excellent transmission characteristics.

It is sectional drawing of the metal cable for LAN of this invention. It is a figure explaining the insulator of the metal cable for LANs of this invention. It is sectional drawing of the conventional metal cable for LAN.

DESCRIPTION OF SYMBOLS 1 Metal cable for LAN 2 Insulator 3 Conductor 4a, 4b, 4c, 4d Twisted wire 5 Foamed layer 6 Non-foamed layer

Claims (5)

In a metal cable for LAN having a plurality of twisted pairs in which two cores covered with an insulator made of a foam layer are twisted on the outer periphery of a conductor to make a pair, and the twisted pitches of the twisted wires are different from each other the foaming rate of the plurality of insulating foam layer in the pair twisted wire of varies respectively in response to said twisted pair pitch, wherein the foaming rate of the higher pair twisted pitch shorter the insulator foam layer is high LAN metal cable.   2. The LAN metal cable according to claim 1, wherein the number of twisted pairs is four. Claim 1 or claim 2 LAN metal cable according surface of the insulator foam layer is characterized by comprising a layer which is non-foamed. LAN metal cable according to any one of claims of claims 1 to 3, expansion ratio of the insulating foam layer, characterized in that the different between 5-40% between each pair of twisted wire. The LAN metal cable according to any one of claims 1 to 4, wherein the non-foamed layer has a thickness of 0.04 to 0.06 mm.

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