JP2003249128A - Transmission cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce difference of differential impedance among all pairs of signal lines in a cable and improve tolerance for crosstalk between pairs of signal lines. <P>SOLUTION: A plurality of pairs of signal lines 7 each of which is formed by tying a pair of signal lines 5 in parallel to each other with a conductive band 3 are arranged in contact with each other in a shielding layer 9 of a transmission cable. Further, a plurality of pairs thereof in the outermost side is contact with the shielding layer 9. Since the conductive band 3 has conduction to the shield layer 9 and this equalizes the spacial relationship between GND and signal lines 5 in any pair of signal lines 7, their characteristics such as impedance become identical. The conductive band 3 continues just before a connector attaching part of a terminal treatment part, which improves tolerance for crosstalk between signal lines. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission cable used as a communication transmission cable used between servers such as computers. Even if a communication signal or the like is instantaneously transmitted with a large capacity, reception and transmission are instantaneous or At the same time, it relates to a transmission cable used when performing smoothly.

[0002]

2. Description of the Related Art Referring to FIG. 3, in a conventional transmission cable 101, a general SCSI cable (scuzzy) used as an interface cable is considered to be the closest. With this SCSI cable,
A pair of signal lines 103 is twisted to form a pair of signal lines 10.
7, a plurality of the signal line pairs 107 are twisted together and assembled, and the plurality of signal line pairs 107 are braided 109 (shielded), and then a sheath 111 is provided around the braid 109 to complete the process. .

[0003]

By the way, the conventional SC
In the transmission cable 101 such as the SI cable, it is necessary to untwist the twist at the terminal processing portion as shown in FIG. 4, and when the untwisted signal line pair 107 is connected to the connector 113, for example. Multiple signal line pairs 1
The signal lines 07 are not necessarily parallel to each other and often cross each other like the dotted signal line pair 107 and the solid signal line pair 107.
Since the crossed signal line pairs 107 are likely to affect each other, there is a problem that crosstalk (crosstalk) is likely to occur in the terminal processing portion.

Further, since the conventional transmission cable 101 does not have a shield on each signal line pair 107, the outer peripheral braid 1
Signal line pair 1 near 09 (shield part; GND)
As the capacitance increases to 07, the impedance tends to decrease, and there is a problem that impedance control is difficult.

Further, there is a problem that it is difficult to control the impedance because the signal line pairs 107 are electrically coupled to each other.

In addition, in order to match the impedance, it may be necessary to change the design of the signal line 103 on the inner circumference and the outer circumference of the transmission cable 101. That is, since it is necessary to design the outer peripheral signal line pair 107 to have a larger impedance than the inner peripheral signal line pair 107,
There is a problem that the processing productivity of the transmission cable 101 is reduced.

Further, in the conventional transmission cable 101, in order to prevent the crosstalk from occurring between the signal line pairs 107 of each other and improve the characteristics of the crosstalk, FIG.
Changing the twist pitch in each pair as shown in (A) and (B) (for example, pitch P ₁ to pitch P
(Change to ₂ ) is required. As a result, since the length of the center conductor is different for each signal line pair 107, it is difficult to control the total length of each pair to be equal, and there is a problem that the propagation delay time is different for each pair. In other words, the skew (propagation delay time difference) characteristic between pairs (between differential pairs) becomes large, and the conductor length difference has become a problem in terms of transmission characteristics in recent high-speed transmission cables.

In the pair (in the differential pair), the signal line 103A and the signal line 10 of the differential pair as shown in FIG. 6 and FIG.
Inward skew (inward propagation delay time difference) characteristics in 3B may be deteriorated. In order to use a cable with a large amount of information for the purpose of recent high-speed transmission, sk in each pair and within each pair
Since it is necessary to make ew as small as possible, there is a problem that the conventional transmission cable 101 has a severe structure for recent high-speed transmission.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to reduce the difference in the differential impedance of each signal line pair of a cable and to improve the crosstalk resistance between the signal line pairs. At the very least, it is to provide a transmission cable capable of improving the processing productivity of the cable.

[0010]

In order to achieve the above object, the transmission cable of the present invention according to claim 1 contacts a plurality of signal line pairs in which a pair of signal lines are held in parallel by a conductive strip. And place it in the shield layer of the cable,
In addition, it is characterized in that a plurality of signal line pairs located on the outer peripheral side are in contact with the shield layer of the cable.

Therefore, since the shield of the conductive strip is maintained until immediately before the connector mounting portion of the terminal processing portion, the crosstalk resistance of each signal line is improved.

Further, since it is not necessary to twist each signal line pair for the purpose of anti-crosstalk, it is easy to keep each signal line pair in equal length, and the cable processing productivity is improved and The skew characteristic is improved and the skew in the signal line caused by unbalanced twist is reduced.

Further, since the shield layer of the conductive strip of the signal line pair is electrically connected to the shield layer of the cable, the positional relationship between GND and the signal line is the same for all signal line pairs, so that impedance and The characteristics are the same for all signal line pairs.

A transmission cable according to a second aspect of the present invention is the transmission cable according to the first aspect, wherein the conductive strip comprises a conductive tape or a conductive wire having conductivity. .

Therefore, the conductive strip may be any one having conductivity, and the conductive tape and the conductor line are easy to shield the pair of signal lines.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a transmission cable 1 according to this embodiment is wound around the entire circumference in order to hold a pair of signal lines 5 in parallel by a conductive tape 3, for example, a conductive tape 3. A plurality of signal line pairs 7 configured by being shielded by being in contact with each other are arranged inside the shield layer 9 of the cable. Moreover, the plurality of signal line pairs 7 located on the outer peripheral side among the plurality of signal line pairs 7 are in contact with the shield layer 9 of the cable.

In this embodiment, an intermediate member 11 for keeping the cable in a circular shape is provided substantially at the center of the plurality of signal line pairs 7. A sheath 13 made of resin is provided on the outermost periphery of the shield layer 9.

More specifically, referring to FIG. 2, each signal line pair 7 has a pair of signal lines 5 arranged in parallel.
The pair of signal lines 5 are machined so as to be mechanically kept equal in length. Each of the above-mentioned signal lines 5 is configured by covering the outer periphery of the central conductor 15 made of, for example, a stranded wire of a conductor element wire with the insulating portion 17 of a low-density insulator. In addition,
The outer periphery of the insulating portion 17 may be covered with a skin layer.

Further, as described above, the conductive tape 3 such as an Al tape is spirally wound or vertically attached to the outside of the pair of signal lines 5 over the entire circumference. The conductive tape 3 is characterized in that the conductor is exposed on the outer peripheral surface. The inner peripheral surface of the conductive tape 3 is made adhesive by an adhesive 19 or the like so that the insulating portion 17 of the signal line 5 is provided.
May or may not be attached. Also,
As the conductive strip, the conductive tape 3 may be a copper tape or a horizontally wound shield using a linear conductor wire.

Referring again to FIG. 1, the shield layer 9 of the transmission cable 1 described above may be braided, or may be a conductive tape wound using an Al tape or the like, or both of them may be used. As a result, the shield layer formed by the conductive tape 3 of the signal line pair 7 and the shield layer 9 of the transmission cable 1 are electrically connected.

From the above, each signal line pair 7 is in an independent state in which the pair of signal lines 5 is shielded by the conductive tape 3, and the conductive tape 3 of each signal line pair 7 and the shield layer 9 of the cable are electrically connected. By doing so, the shield layers of all the signal line pairs 7 can be kept at the same potential. For example, when the shield layer 9 is a ground (GND),
All signal line pairs 7 have the same potential GND on the outer circumference. Therefore, regardless of the positions on the inner circumference side and the outer circumference side of the transmission cable 1, all the signal line pairs 7 have the same GND positional relationship and the impedance is kept the same. As a result, there is no need to change the design as in the conventional case in order to make the signal line pairs 7 have the same characteristics on the inner and outer circumferences of the transmission cable 1.

Further, in the transmission cable 1 according to the embodiment of the present invention, since each signal line pair 7 is shielded by the conductive tape 3, the conductive shield is provided right before the connector mounting portion of the terminal processing portion. Can be maintained. Therefore, since the signal line pairs 7 are not electrically coupled to each other, the crosstalk resistance of each signal line 5 is improved. Therefore, it is not necessary to insert twist in the signal line pair 7 for the purpose of improving crosstalk resistance, which is required in the structure of the conventional transmission cable.

Further, since the twist applied to each signal line pair 7 can be eliminated, the length of the central conductor 15 of each signal line pair 7 can be controlled more easily than in the conventional transmission cable, and the transmission cable can be controlled. The processing productivity of 1 can be improved. In addition, the skew characteristic between pairs due to the conductor length difference of the signal line pair 7 can be improved. In addition, by eliminating the twist, it is possible to eliminate the twist imbalance itself, which is likely to occur in a twisted wire, and as a result, it is possible to improve the skew characteristic to the inside.

Further, comparing the assembly product using the transmission cable 1 of the embodiment of the present invention with the assembly product using the conventional cable, in the case of the conventional cable, the signal line pair 7 is disturbed near the terminal processing section. As a result, the anti-crosstalk characteristic is likely to deteriorate, but the transmission cable 1 of the present invention
In the assembly product using, the GN is attached to the outer periphery of each signal line pair 7.
As a result of the structure having the D layer, even if the signal line pairs 7 are disturbed and crossed, the crosstalk resistance is not deteriorated.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes.

[0027]

As can be understood from the above description of the embodiment of the invention, according to the invention of claim 1, the shield of the conductive strip is maintained until immediately before the connector mounting portion of the terminal processing portion. Therefore, the crosstalk resistance of each signal line is improved.

Further, since it is not necessary to twist each signal line pair for the purpose of anti-crosstalk, it is easy to keep each signal line pair in the same length, and the cable processing productivity can be improved, The skew characteristic between pairs can be improved. Furthermore, since it is not necessary to twist the signal line pair, skew in the signal line caused by unbalanced twist can be reduced.

Further, by connecting the shield layer of the conductive strip of the signal line pair to the shield layer of the cable, the GND
The positional relationship between the signal line and the signal line can be the same for any signal line pair. Therefore, characteristics such as impedance can be made the same for any signal line pair.

According to the second aspect of the present invention, the conductive strip may have conductivity, but the pair of signal lines can be easily shielded by using a conductive tape or a conductor wire. .

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing the structure of a signal line pair in the transmission cable of FIG.

FIG. 3 is a perspective view of a conventional transmission cable.

FIG. 4 is a schematic explanatory view showing a terminal processing state of a conventional transmission cable.

FIG. 5 shows a twisted state of a signal line pair of a conventional transmission cable, and FIGS. 5A and 5B are schematic explanatory diagrams showing a state in which a twisted pitch is different.

FIG. 6 is a comparative diagram showing a propagation delay time difference between a signal line A and a signal line B of a signal line pair of a conventional transmission cable.

FIG. 7 is a partially enlarged view of FIG.

[Explanation of symbols]

1 transmission cable 3 Conductive tape (conductive strip) 5 signal lines 7 signal line pairs 9 Shield layer 11 Intermediary material 13 sheath 15 center conductor 17 Insulation part 19 Adhesive

Claims (2)

[Claims] 1. A plurality of signal line pairs in which a plurality of signal line pairs in which a pair of signal lines are held in parallel by a conductive strip are in contact with each other and arranged in a shield layer of a cable, and which are located on the outer peripheral side. A transmission cable having a structure in which the cable contacts the shield layer of the cable. 2. The conductive strip comprises a conductive tape or a conductive wire having conductivity.
The listed transmission cable.