JP2016167466A - Multi pair cable for differential signal transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi pair cable for differential signal transmission, in which the occurrence of cross talk can be suppressed.SOLUTION: The multi pair cable for differential signal transmission is provided that is formed by binding a plurality of differential signal transmission cables. Each of the differential signal transmission cable is formed of a pair of signal line conductors, an insulator disposed around the signal line conductors, and a first shield conductor disposed around the insulator. The multi pair cable for differential signal transmission comprises: a first cable aggregation formed by laminating the plurality of differential signal transmission cable; a first interposition member for covering surrounding of the first cable aggregation; a second interposition member disposed in a gap between the plurality of laminated differential signal transmission cables and the first interposition member, and holding a traverse surface shape of the first interposition member in a circular shape; a second cable aggregation disposed around the first interposition member, and formed by arranging the plurality of differential signal transmission cables in a peripheral direction of the first interposition member; and a coating member for covering the surrounding of the second cable aggregation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multiple-to-differential signal transmission cable formed by bundling a plurality of differential signal transmission cables.

  Conventionally, in devices such as servers, routers, and storage products that handle high-speed digital signals of several Gbit / s or more, differential interface standards such as LVDS (Low Voltage Differential Signal) have been adopted. Differential signals are transmitted between the circuit boards using a differential signal transmission cable. The differential signal has a feature of high resistance to external noise while realizing a low system power supply voltage.

  The differential signal transmission cable includes a pair of signal line conductors, and a positive signal and a negative signal whose phases are inverted by 180 degrees are transmitted to the signal line conductors. The potential difference between these two signals becomes the signal level. For example, if the potential difference is positive, the signal level is recognized as “High”, and if it is negative, the signal level is recognized as “Low”. Yes.

  As the transmission capacity increases in recent years, a multi-differential signal transmission cable formed by bundling a plurality of differential signal transmission cables has come to be used. As a technique which disclosed the cable for many pairs differential signal transmission which can transmit such many differential signals, there exist some which were described in patent document 1, for example. This Patent Document 1 includes a pair of insulating wires and drain wires formed by covering a signal line (signal line conductor) with an insulating layer (insulator), covering these with a shielding material (shield tape conductor), Further, a transmission cable (differential signal transmission cable) is disclosed in which a cushion material is covered around the shield material. A plurality of transmission cables are bundled with a shield tape, a braided shield, and a jacket layer to form a collective transmission cable (multi-pair differential signal transmission cable).

JP 2004-087189 A (FIGS. 2 and 6)

  However, in the multi-pair differential signal transmission cable described in Patent Document 1 described above, signal transmission efficiency is reduced due to crosstalk between the differential signal transmission cables (between pairs), that is, crosstalk. Such a problem may occur.

  Here, in crosstalk, electromagnetic energy is transferred from a differential signal transmission cable (Aggressor) that does not contribute to signal transmission to a differential signal transmission cable (Victim) that contributes to signal transmission. Caused by. This transfer of electromagnetic energy is mainly induced by a common mode component having a large electric field spread.

  Further, in a normal multiple-pair differential signal transmission cable, each of the differential signal transmission cables is shielded by a shield tape conductor to prevent the above-described electric field spread (leakage of common mode energy). . However, in practice, a magnetic field is generated by a current (common mode current) flowing through the shield tape conductor, and a common mode component generated thereby also causes crosstalk. The amount of energy of the common mode component at this time is determined by the common mode current flowing on the outer surface of the shield tape conductor.

  As described above, the cause of crosstalk includes the transfer of common mode energy between pairs and the common mode current flowing through the shield tape conductor of each differential signal transmission cable. Furthermore, the common mode current is also generated when the electrical balance of each differential signal transmission cable is lost. Specifically, when manufacturing a multi-pair differential signal transmission cable by twisting each differential signal transmission cable, the direction of each differential signal transmission cable is changed or the insulator is crushed and deformed. The common mode current is also generated by, for example.

  An object of the present invention is to provide a multi-pair differential signal transmission cable capable of suppressing the occurrence of crosstalk.

  In one aspect of the present invention, a multiple-pair differential signal transmission cable formed by bundling a plurality of differential signal transmission cables, wherein the differential signal transmission cable includes a pair of signal line conductors, A first cable assembly formed of an insulator provided around the signal line conductor and a first shield conductor provided around the insulator, wherein a plurality of the differential signal transmission cables are stacked. A first interposed member that covers the periphery of the first cable assembly, and a plurality of stacked cables for differential signal transmission and the first interposed member, the first interposed member A second interposed member that holds the cross-sectional shape of the member in a circular shape, and a plurality of the differential signal transmission cables that are provided around the first interposed member and arranged in the circumferential direction of the first interposed member A second cable assembly; And a, a covering member covering the periphery of the cable assembly.

  In another aspect of the present invention, the second interposed member is disposed on both end sides along the arrangement direction of the signal conductors of the differential signal transmission cable in the first interposed member.

  In another aspect of the present invention, the second interposed member is twisted together with the first cable assembly.

  In another aspect of the present invention, the second interposed member is made of a circular thread, paper, foam or rubber.

  In another aspect of the invention, the signal line conductors are collectively covered with the insulator, and the periphery of the insulator is covered with the first shield tape conductor without a gap.

  In another aspect of the present invention, the cross-sectional shape of the insulator includes a pair of linear portions extending in the direction in which the signal line conductors are arranged, and a pair of arc portions provided between the linear portions. It has a track shape.

  In another aspect of the present invention, a cross-sectional shape of the insulator is an elliptical shape having a major axis extending in the direction in which the signal line conductors are arranged and a minor axis perpendicular to the major axis.

  In another aspect of the present invention, the first cable assembly is formed by the two differential signal transmission cables, and the second cable assembly is formed by the six differential signal transmission cables. Is done.

  In another aspect of the present invention, the covering member is formed of a second shield tape conductor, a braided wire covering the periphery of the second shield tape conductor, and a jacket covering the periphery of the braided wire.

  ADVANTAGE OF THE INVENTION According to this invention, the cable for many pairs differential signal transmission which can suppress generation | occurrence | production of crosstalk can be obtained.

2 is a cross-sectional view showing a cross section of the multiple-differential signal transmission cable according to Embodiment 1. FIG. (A) is a perspective view of the cable for differential signal transmission, (b) is a sectional view of the cable for differential signal transmission. It is a schematic diagram which shows typically an example of the measurement system which analyzes the magnetic field intensity in the vicinity of the cable for differential signal transmission. It is a graph which shows a magnetic field strength spectrum at the time of inputting a differential mode signal to a cable for differential signal transmission. It is a graph which shows a magnetic field strength spectrum at the time of inputting a common mode signal to the cable for differential signal transmission. (A) is a perspective view of the differential signal transmission cable according to the second embodiment, and (b) is a cross-sectional view of the differential signal transmission cable according to the second embodiment. (A) is sectional drawing of the cable for differential signal transmission which concerns on Embodiment 3, (b) is sectional drawing of the cable for differential signal transmission concerning Embodiment 4. FIG.

  Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.

  1 is a cross-sectional view showing a cross-section of a multi-pair differential signal transmission cable according to Embodiment 1, FIG. 2 (a) is a perspective view of the differential signal transmission cable, and FIG. 1 (b) is a differential signal transmission. Sectional drawing of the cable is shown, respectively.

  As shown in FIG. 1, the multi-differential signal transmission cable 10 according to the first embodiment has a circular cross-sectional shape, and the axial center C (dashed circle in the figure) side is A first cable assembly 20 is provided, and a second cable assembly 30 is provided around the first cable assembly 20.

  The first cable assembly 20 is formed by twisting two differential signal transmission cables 40 together. The second cable assembly 30 is formed by arranging six differential signal transmission cables 40 around the first cable assembly 20 along the circumferential direction and twisting them together. As described above, the multi-pair differential signal transmission cable 10 is formed by twisting and bundling a total of eight differential signal transmission cables 40.

  Prior to detailed description of the multi-pair differential signal transmission cable 10, first, the structure of the differential signal transmission cable 40 forming the multi-pair differential signal transmission cable 10 will be described in detail.

  As shown in FIG. 2, the differential signal transmission cable 40 includes a pair of signal line conductors 41. A positive signal as a differential signal is transmitted to one of the signal line conductors 41, and a negative signal as a differential signal is transmitted to the other of the signal line conductors 41. It is like that. Each signal line conductor 41 is formed of, for example, an annealed copper wire (Silver plated Copper Wire) whose surface is subjected to silver plating, and is excellent in high-speed transmission applications. However, if necessary, an annealed copper wire (Tinned Annealed Copper Wire) subjected to an inexpensive surface treatment such as a tin plating treatment can also be used.

  The periphery of each signal line conductor 41 is collectively covered with a common insulator 42. The insulator 42 is made of, for example, solid polyethylene (Poly-Ethylene) that does not contain bubbles in order to give the differential signal transmission cable 40 flexibility. The cross-sectional shape of the insulator 42 includes a pair of straight portions 42a of equal length extending in the arrangement direction of the signal line conductors 41 and a pair of arc portions 42b provided between the straight portions 42a. It is formed in a track-like shape that is substantially the same shape as a track in an athletic field.

  The insulator 42 holds the signal line conductors 41 so as to have a distance P1 between axes (for example, 0.572 mm), and the length dimension along the arrangement direction of the signal line conductors 41 of the insulator 42 is L1 ( For example, the width dimension in the direction orthogonal to the arrangement direction of the signal line conductors 41 of the insulator 42 is set to W1 (for example, 0.96 mm) (L1 = 2 · W1). By setting the shape of the insulator 42 in this way, the aspect ratio of the cross-sectional shape of the differential signal transmission cable 40 is set to “2: 1”. Therefore, as shown in FIG. 1, when two differential signal transmission cables 40 are stacked, the cross-sectional shape thereof becomes a substantially square.

  Around the insulator 42, a first shield tape conductor 43 for suppressing the influence of external noise is covered with a vertical auxiliary winding (also referred to as a cigarette winding) without a gap. The first shield tape conductor 43 is formed of, for example, a sheet-like copper foil, and both end portions along the winding direction are overlapped portions 43a that are overlapped with each other. The overlap portion 43 a is formed by the first shield tape conductor 43 and extends in the longitudinal direction of the differential signal transmission cable 40.

  Here, the length dimension along the arrangement direction of the signal line conductors 41 of the overlap portion 43a is set to a length dimension D1 smaller than the distance P1 between the axis centers of the signal line conductors 41 (D1 <P1). ). The overlap portion 43 a is disposed on the vertical line V in the middle of the line segment H connecting the axis centers of the signal line conductors 41. Thereby, the distance from the overlap part 43a to each signal line conductor 41 is made substantially equal to suppress the deterioration of the electrical characteristics of the differential signal transmission cable 40.

  However, the first shield tape conductor 43 is not limited to a copper foil, and may be another metal foil, or may be a braided wire knitted with a fine metal wire such as an annealed copper wire.

  Around the first shield tape conductor 43, an insulating tape 44 that functions as a protective sheath for protecting the differential signal transmission cable 40 is wound. Here, as the insulating tape 44, for example, an insulating tape made of heat-resistant PVC (Heat Resistant Polyvinyl Chloride) is used.

  As shown in FIG. 1, the plurality of differential signal transmission cables 40 that form the first cable assembly 20 and the second cable assembly 30 all have overlapping portions 43 a in the multiple-differential signal transmission cable 10. It arrange | positions so that it may face the radial direction outer side. That is, each of the differential signal transmission cables 40 is disposed so as to face the axis C of the multiple-pair differential signal transmission cable 10.

  Between the 1st cable assembly 20 and the 2nd cable assembly 30, the 1st interposition member 11 formed in the substantially cylindrical shape is provided. The first interposed member 11 is provided so as to cover the periphery of the first cable assembly 20, and is constituted by, for example, an insulating tape made of heat-resistant PVC.

  A pair of second interposed members 12 is provided in the first interposed member 11 together with the first cable assembly 20. Each of the second interposed members 12 is on the side opposite to the overlap portion 43a side of each of the differential signal transmission cables 40 forming the first cable assembly 20, and each signal line conductor 41 (see FIG. 2) is arranged. It is arranged on both ends along the direction. Each second interposed member 12 is twisted together with each differential signal transmission cable 40 when the first cable assembly 20 is twisted and manufactured.

  Thus, by arranging the second interposed members 12 at the predetermined positions described above, the cross-sectional shape of the first interposed member 11 is held in a circular shape as illustrated. That is, the outer shape of the first cable assembly 20 whose cross-sectional shape is formed in a substantially square shape by stacking the two differential signal transmission cables 40 is provided with the pair of second interposed members 12. Each of the second interposed members 12 is formed into a substantially circular shape. Here, as each 2nd interposition member 12, the material which has buffer property, such as the thread | yarn and paper formed by twisting a thin fibrous substance, and also foam and rubber | gum, is used.

  Around the first interposed member 11, a second cable formed by arranging six differential signal transmission cables 40 at equal intervals (60 ° intervals) along the circumferential direction of the first interposed member 11. An assembly 30 is provided. Each differential signal transmission cable 40 forming the second cable assembly 30 is pressed toward the first intervening member 11 by a second shield tape conductor (covering member) 13 wound so as to cover the periphery thereof. Are twisted together. The second shield tape conductor 13 is also formed of, for example, a sheet-like copper foil, similarly to the first shield tape conductor 43 (see FIG. 2). However, the second shield tape conductor 13 is not limited to a copper foil, and may be another metal foil, or may be a braided wire in which a fine metal wire such as an annealed copper wire is knitted.

  Here, when the second shield tape conductor 13 is wound around each of the differential signal transmission cables 40 forming the second cable assembly 30 in the manufacturing process of the multiple-pair differential signal transmission cable 10, The differential signal transmission cables 40 are each pressed toward the first interposed member 11. Then, the pressing force tends to incline some of the differential signal transmission cables 40 as indicated by a broken-line arrow M in FIG. However, since the first interposing member 11 is held in a circular shape by the second interposing member 12 disposed therein, each differential signal transmission cable 40 forming the second cable assembly 30 is inclined. It is possible to prevent the orientation from changing.

  As a result, as shown in FIG. 1, it is possible to arrange each of the differential signal transmission cables 40 regularly and orderly without tilting all (eight) cables. Accordingly, the insulator 42 (see FIG. 2) of each differential signal transmission cable 40 is also prevented from being deformed by being partially subjected to a large load. As a result, the first shield tape conductor 43 is peeled off from the insulator 42. Inconveniences that would occur are also suppressed. In particular, in the differential signal transmission cable 40 having a pair of straight portions 42a as shown in FIG. 2, the deformation of the insulator 42 is directly connected to the peeling of the first shield tape conductor 43 at each straight portion 42a, Since this leads to deterioration of electrical characteristics, deformation of the insulator 42 is a matter to be suppressed.

  Around the second shield tape conductor 13, a braided wire 14 formed by weaving a fine metal wire such as an annealed copper wire is provided. Further, a jacket (sheath) 15 made of heat-resistant PVC is provided around the braided wire 14, for example. Here, the braided wire 14 and the jacket 15 also constitute a covering member in the present invention, like the second shield tape conductor 13.

  As shown in FIG. 2, an overlap portion 43 a formed by the first shield tape conductor 43 is provided on one side along the short direction of the differential signal transmission cable 40, and the differential signal transmission cable 40. The overlap part 43a is not provided on the other side along the short direction. Accordingly, when leakage of electromagnetic energy around the differential signal transmission cable 40 was confirmed, it was found that the overlap portion 43a side was larger than the opposite side. Hereinafter, the analysis result will be described.

  FIG. 3 is a schematic diagram showing an example of a measurement system for analyzing the magnetic field strength in the vicinity of the differential signal transmission cable, and FIG. 4 shows the magnetic field strength spectrum when a differential mode signal is input to the differential signal transmission cable. FIG. 5 is a graph showing a magnetic field intensity spectrum when a common-mode signal is input to the differential signal transmission cable.

  FIG. 3 shows a measurement system having an EMI (Electro-Magnetic Interference) measuring device 53 that has been subjected to correction processing so that the ends of a plurality of cables 51 connected to the network analyzer 50 become calibration surfaces 52. Show. In this measurement system, a signal propagation defined by a mixed mode signal, that is, a differential mode signal and a common mode signal, is passed through a pair of cable terminal processing jigs 54 to a differential signal transmission cable 40 that is a measurement object. Enter the mode. Here, the EMI measuring device 53 side of the differential signal transmission cable 40, which is a measurement object, is subjected to antireflection processing by the terminator 55. By performing the non-reflection process in this way, unnecessary reflection signals that can become noise are reduced, and a highly accurate analysis result can be obtained.

  The common mode current that causes crosstalk flows on the surface of the first shield tape conductor 43 (see FIG. 2) that forms the differential signal transmission cable 40. Therefore, the magnetic field probe (magnetic field detector) 56 is disposed close to the surface of the differential signal transmission cable 40 to detect the magnetic field radiated from the differential signal transmission cable 40. The magnetic field signal detected by the magnetic field probe 56, that is, the common mode current component is amplified by the preamplifier 57, and then the network analyzer 50 via the cable 58, the SMA (Sub-Miniature Type A) connector 59 and the cable 51. Is measured as a single-ended mode signal.

  FIG. 4 shows a magnetic field intensity spectrum when a differential mode signal (Odd Mode signal) is input to the differential signal transmission cable 40. That is, in the measurement system of FIG. 3, when a differential mode signal is input to the differential signal transmission cable 40, the common mode current component generated from the differential signal transmission cable 40 is graphed.

  On the other hand, FIG. 5 shows a magnetic field intensity spectrum when an in-phase mode signal (Even Mode signal) is input to the differential signal transmission cable 40. That is, in the measurement system of FIG. 3, when a common mode signal is input to the differential signal transmission cable 40, the common mode current component generated from the differential signal transmission cable 40 is graphed.

  As shown in FIG. 4, the analysis result when the differential mode signal is input shows that the magnetic field probe 56 is brought close to the surface where the overlap portion 43a is present, and the surface where the overlap portion 43a is not present. It can be confirmed that there is almost no difference in the common mode current component when the magnetic field probe 56 is brought close to each other.

  On the other hand, as shown in FIG. 5, when the analysis result when the common mode signal is input is seen, the side where the magnetic field probe 56 is brought close to the surface on the side where the overlap portion 43a is present is the side where the overlap portion 43a is not present. It can be confirmed that the common mode current component is larger than the case where the magnetic field probe 56 is brought close to the surface. This indicates that the leakage of electromagnetic energy from the side where the overlap portion 43a is present is larger than the leakage of electromagnetic energy from the side where the overlap portion 43a is not present. It can be seen that this tendency becomes more prominent as the frequency is higher (at 5 Ghz or more, particularly at 8 Ghz or more).

  That is, in the multiple-pair differential signal transmission cable 10 capable of performing a high-speed digital signal of several Gbit / s or more, the overlap portion 43a of each differential signal transmission cable 40 is connected to the multiple-pair differential signal transmission cable 10. It turns out that directing regularly and orderly to the outside in the radial direction is an important design element in the countermeasure against crosstalk of the cable 10 for multi-pair differential signal transmission.

  As described above in detail, according to the multiple-pair differential signal transmission cable 10 according to the first embodiment, the second interposed member 12 that holds the cross-sectional shape of the first interposed member 11 in a circular shape is the first. The overlap portion 43a of the differential signal transmission cable 40 that is provided in the first interposition member 11 together with the cable assembly 20 and forms the first cable assembly 20 and the second cable assembly 30 is formed by the second shield tape conductor. Is directed to 13.

  As a result, even when the plurality of differential signal transmission cables 40 are twisted and bundled, the cross-sectional shape of the first interposed member 11 is held in a circular shape by the second interposed member 12, so that each differential signal By preventing the direction of the transmission cable 40 from changing or the insulator 42 from being crushed and deformed, it is possible to suppress the collapse of electrical balance.

  Moreover, since the overlap part 43a through which a large amount of common mode current flows is directed to the second shield tape conductor 13, leakage of common mode energy to the inside of the multiple-differential signal transmission cable 10 can be suppressed.

  Therefore, the many-to-differential signal transmission cable 10 that can suppress the occurrence of crosstalk can be obtained.

  Furthermore, since leakage of common mode energy to other differential signal transmission cables 40 can be suppressed, the physical distance between each differential signal transmission cable 40 can be reduced without increasing the physical distance between each pair. Common mode energy interference can be prevented. Therefore, it is possible to reduce the diameter of the multi-differential signal transmission cable 10 and to reduce the size of the multi-differential signal transmission cable 10.

  Next, Embodiment 2 of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  6A is a perspective view of a differential signal transmission cable according to the second embodiment, and FIG. 6B is a cross-sectional view of the differential signal transmission cable according to the second embodiment.

  As shown in FIG. 6, the differential signal transmission cable 60 forming the multiple-differential signal transmission cable according to the second embodiment is the differential signal transmission cable 40 (FIG. 2) of the first embodiment described above. Compared with the reference), only the cross-sectional shape of the insulator 61 is different. Specifically, the cross-sectional shape of the insulator 61 has a major axis whose length dimension is set to L2 in the arrangement direction of the signal line conductors 41, and a length dimension perpendicular to the major axis is W2. It is formed in an elliptical shape having a minor axis set to (L2> W2). The insulator 61 is also formed of solid polyethylene that does not contain bubbles.

  Also in the second embodiment formed as described above, the same operational effects as those of the first embodiment described above can be achieved. In the second embodiment, the first shield tape conductor 43 is wound around the insulator 61 having an elliptical cross section. Therefore, compared to the first embodiment having the pair of straight portions 42a (see FIG. 2), the first shield tape conductor 43 is less likely to be peeled off from the insulator 61 with respect to a partial external force load. It is also possible to achieve an effect that a gap is hardly generated between the insulator 61 and the first shield tape conductor 43.

  Next, Embodiment 3 of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those in the second embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 7A is a cross-sectional view of the differential signal transmission cable according to the third embodiment.

  As shown in FIG. 7 (a), the differential signal transmission cable 70 forming the multi-differential signal transmission cable according to the third embodiment is made of foamed polyethylene (Foamed Poly-Ethylene). 71 is different from the first embodiment in that an insulator skin layer 72 is provided between the insulator 71 and the first shield tape conductor 43. Here, the insulator skin layer 72 is formed in a substantially cylindrical shape by an insulator such as polytetrafluoroethylene (PTFE), and is a soft insulator before being hardened when the insulator 71 is extruded. It plays the role which hold | maintains 71 so that it may not deform | transform.

  Further, the third embodiment is different in that the overlap portion 43a of the first shield tape conductor 43 is offset from the vertical line V by a predetermined amount as shown by a one-dot chain line arrow in the figure. Here, the offset amount of the overlap portion 43a from the vertical line V is set to an amount that is sufficiently smaller than the inter-axial distance P1 of each signal line conductor 41. Accordingly, the offset amount does not adversely affect the occurrence of crosstalk.

  In the third embodiment formed as described above, the same function and effect as in the second embodiment described above can be achieved. In the third embodiment, since the insulator 71 is made of foamed polyethylene, the dielectric constant of the insulator 71 can be lowered. As a result, it is possible to provide a differential signal transmission cable 70 more suitable for high-speed transmission applications while suppressing a decrease in transmission speed and the like. Further, as compared with the solid insulator 61 (see FIG. 6) in the second embodiment, the thickness of the insulator 71 can be reduced without changing the transmission efficiency, and the differential signal transmission cable 70 is compact. Can be realized.

  Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 7B is a cross-sectional view of the differential signal transmission cable according to the fourth embodiment.

  As shown in FIG. 7 (b), the differential signal transmission cable 80 forming the multiple-differential signal transmission cable according to the fourth embodiment includes the signal line conductors 41 individually connected to the insulators 81, The difference is that 82 is covered. Since each signal line conductor 41 is individually covered with the insulators 81 and 82, the distance P2 between the axis centers of each signal line conductor 41 is the distance between the axis centers of the above-described first to third embodiments. It is larger than P1 (P2> P1).

  Moreover, the length dimension D2 along the arrangement direction of each signal line conductor 41 of the overlap part 43a in the 1st shield tape conductor 43 is longer than the length dimension D1 of each Embodiment 1-3 mentioned above. (D2> D1). However, in order to prevent a large amount of common mode current from flowing through the overlap portion 43a, the length dimension along the arrangement direction of the signal line conductors 41 of the overlap portion 43a is within a range that does not hinder manufacturing. It is desirable to make it as short as possible.

  It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, in each of the above embodiments, the first cable assembly 20 is formed by the two differential signal transmission cables 40, and the second cable assembly 30 is formed by the six differential signal transmission cables 40. However, the present invention is not limited to this. According to the specifications required for the multi-pair differential signal transmission cable, for example, the first cable assembly 20 is formed by three differential signal transmission cables 40 and the second cable assembly 30 is seven. Alternatively, the differential signal transmission cable 40 may be used. That is, an arbitrary number such as an odd number may be set.

  Further, in each of the above-described embodiments, the signal line conductor 41 has been subjected to a silver plating process around the signal line conductor 41. However, the present invention is not limited thereto, and the signal line in which the surrounding plating process is not performed. A conductor can also be used. In this case, the manufacturing cost of the multi-differential signal transmission cable can be reduced.

  Further, in each of the above-described embodiments, the cross-sectional shape of the second interposed member 12 is a circular shape. However, the present invention is not limited to this, and the inner shape (arc shape) of the first interposed member 11 is not limited thereto. For example, a second interposition member having a fan-shaped cross section may be used. In this case, the cross-sectional shape of the first interposed member 11 can be held in a circular shape with higher accuracy.

  Further, in each of the above-described embodiments, the multiple-differential signal transmission cable 10 including the first cable assembly 20 and the second cable assembly 30 is shown, but the present invention is not limited to this, for example, A third, fourth, fifth, etc. cable assembly comprising a plurality of differential signal transmission cables 40 is provided between the second cable assembly 30 and the second shield tape conductor 13. Also good. In this case, the overlap portion 43a of each differential signal transmission cable 40 forming each cable assembly is also arranged so as to face the radially outer side of the multiple-differential signal transmission cable.

DESCRIPTION OF SYMBOLS 10 Cable for many pairs differential signal transmission 11 1st interposition member 12 2nd interposition member 13 2nd shield tape conductor (covering member)
14 Braided wire (coating material)
15 Jacket (coating material)
DESCRIPTION OF SYMBOLS 20 1st cable aggregate 30 2nd cable aggregate 40 Differential signal transmission cable 41 Signal line conductor 42 Insulator 42a Straight line part 42b Arc part 43 First shield tape conductor 43a Overlap part 60 Differential signal transmission cable 61 Insulator 70 Differential signal transmission cable 71 Insulator 80 Differential signal transmission cable 81 Insulator H line segment V Vertical line

Claims (9)

A multi-differential signal transmission cable formed by bundling a plurality of differential signal transmission cables,
The differential signal transmission cable is
A pair of signal line conductors;
An insulator provided around the signal line conductor;
A first shield conductor provided around the insulator;
Formed from
A first cable assembly in which a plurality of differential signal transmission cables are stacked;
A first interposed member that covers the periphery of the first cable assembly;
A second interposed member that is provided in a gap between the plurality of stacked differential signal transmission cables and the first interposed member, and holds a cross-sectional shape of the first interposed member in a circular shape;
A second cable assembly provided around the first interposition member, wherein a plurality of the differential signal transmission cables are arranged in a circumferential direction of the first interposition member;
A multi-differential signal transmission cable comprising: a covering member that covers the periphery of the second cable assembly. The multi-differential signal transmission cable according to claim 1,
The second interposition member is a multiple-pair differential signal transmission cable disposed on both ends of the differential signal transmission cable in the first interposition member along the arrangement direction of the signal conductors. In the cable for many-to-differential signal transmission according to claim 1 or 2,
The second interposition member is a multi-differential signal transmission cable that is twisted together with the first cable assembly. In the cable for many-to-differential signal transmission according to any one of claims 1 to 3,
The second interposition member is a multi-pair differential signal transmission cable made of a circular thread, paper, foam or rubber. In the cable for many-to-differential signal transmission according to any one of claims 1 to 4,
The signal line conductors are collectively covered with the insulator, and the periphery of the insulator is covered with the first shield conductor without any gaps. In the cable for many-to-differential signal transmission according to any one of claims 1 to 5,
The insulator has a cross-sectional shape that is a track-like shape having a pair of linear portions extending in the arrangement direction of the signal line conductors and a pair of arc portions provided between the linear portions. Cable for differential signal transmission. In the cable for many-to-differential signal transmission according to any one of claims 1 to 5,
The multi-differential signal transmission cable, wherein a cross-sectional shape of the insulator is an elliptical shape having a long axis extending in the direction in which the signal line conductors are arranged and a short axis perpendicular to the long axis. . In the cable for many-to-differential signal transmission according to any one of claims 1 to 7,
The multiple differential signal, wherein the first cable assembly is formed by two differential signal transmission cables, and the second cable assembly is formed by six differential signal transmission cables. Transmission cable. In the cable for many-to-differential signal transmission according to any one of claims 1 to 8,
A multi-pair differential signal transmission cable, wherein the covering member is formed of a second shield conductor, a braided wire covering the periphery of the second shield conductor, and a jacket covering the periphery of the braided wire.