JP5454648B2 - Differential signal cable, transmission cable using the same, and method for manufacturing differential signal cable - Google Patents
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Description
本発明は、数Ｇｂｐｓ以上の高速デジタル信号を伝送させるために用いる差動信号用ケーブル及びこれを用いた伝送ケーブル、並びに差動信号用ケーブルの製造方法に係り、特に、信号波形劣化の小さい差動信号用ケーブル及びこれを用いた伝送ケーブル、並びに差動信号用ケーブルの製造方法に関するものである。 The present invention relates to a differential signal cable used for transmitting a high-speed digital signal of several Gbps or more, a transmission cable using the same, and a method for manufacturing the differential signal cable, and in particular, a difference in small signal waveform deterioration. The present invention relates to a dynamic signal cable, a transmission cable using the same, and a method for manufacturing a differential signal cable.
数Ｇｂｐｓ以上の高速デジタル信号を扱うサーバ、ルータ、ストレージ製品などにおいて、電子機器間あるいは電子機器内の基板間の信号伝送には、差動信号による信号伝送が用いられている。電子機器間あるいは電子機器内の基板間は、差動信号用ケーブルにより電気的に接続される。 In servers, routers, storage products, and the like that handle high-speed digital signals of several Gbps or more, signal transmission using differential signals is used for signal transmission between electronic devices or between substrates in electronic devices. The electronic devices or the substrates in the electronic device are electrically connected by a differential signal cable.
差動信号による信号伝送では、位相を反転させた２つの信号を用い、受信側で２つの信号の差分を合成出力する。差動信号用ケーブルは、位相を反転させた２つの信号を伝送するための２本の信号用導体（導線、芯線）を備えている。 In signal transmission using a differential signal, two signals having inverted phases are used, and the difference between the two signals is synthesized and output on the receiving side. The differential signal cable includes two signal conductors (conductive wire and core wire) for transmitting two signals whose phases are inverted.
差動信号用ケーブルでは、２本の信号用導体に流れる電流が互いに逆方向を向いて流れることとなるため、外部に放射される電磁波が小さくなる。また、差動信号用ケーブルでは、外部から受けたノイズが２本の信号用導体に等しく重畳されるため、受信側で２つの信号の差分を合成出力することで、ノイズによる影響を打ち消すことができる。これらの理由から、高速デジタル信号の伝送には、差動信号による信号伝送が好適である。 In the differential signal cable, since the currents flowing through the two signal conductors flow in opposite directions, electromagnetic waves radiated to the outside are reduced. In addition, in the differential signal cable, noise received from the outside is equally superimposed on the two signal conductors, so that the influence of the noise can be canceled by combining and outputting the difference between the two signals on the receiving side. it can. For these reasons, signal transmission using differential signals is suitable for high-speed digital signal transmission.
従来の差動信号用ケーブルとして、信号用導体を絶縁体で被覆した２本の絶縁電線を撚り合わせて対にしたツイストペアケーブルがある。ツイストペアケーブルは、安価で平衡性に優れており、曲げも容易であるため、中距離の信号伝送に広く用いられている。 As a conventional differential signal cable, there is a twisted pair cable in which two insulated wires each having a signal conductor covered with an insulator are twisted and paired. Twisted pair cables are widely used for medium-distance signal transmission because they are inexpensive, excellent in balance, and easy to bend.
しかし、このツイストペアケーブルは、グランドに相当する導体が無いので、ケーブル近傍に置かれた金属の影響を受けやすく、特性インピーダンスが安定しない。そのため、ツイストペアケーブルでは、数ＧＨｚの高周波領域では信号波形が崩れやすいという問題がある。このような理由から、ツイストペアケーブルは、数Ｇｂｐｓ以上の伝送線路にはあまり用いられることがない。 However, since this twisted pair cable has no conductor corresponding to the ground, it is easily affected by the metal placed in the vicinity of the cable, and the characteristic impedance is not stable. For this reason, the twisted pair cable has a problem that the signal waveform tends to collapse in a high frequency region of several GHz. For these reasons, twisted pair cables are rarely used for transmission lines of several Gbps or more.
一方、他の差動信号用ケーブルとして、２本の絶縁電線を撚らずに並行して配置し、これをシールド用導体で覆ったツイナックスケーブルがある。ツイナックスケーブルは、ツイストペアケーブルに比べて２本の導体間の物理長の差が少なく、また、シールド用導体が２本の絶縁電線を覆うように設けられるので、ケーブル近傍に金属を置いても、特性インピーダンスが不安定になることもなく、また、ノイズ耐性も高い。そのため、ツイナックスケーブルは、比較的高速で短距離（数ｍから数十ｍ）の信号伝送に用いられている。 On the other hand, as another differential signal cable, there is a twinax cable in which two insulated wires are arranged in parallel without being twisted and covered with a shield conductor. A twinax cable has a smaller difference in physical length between two conductors than a twisted pair cable, and a shield conductor is provided so as to cover two insulated wires. The characteristic impedance does not become unstable and noise resistance is high. Therefore, the twinax cable is used for signal transmission at a relatively high speed and a short distance (several meters to several tens of meters).
ツイナックスケーブルのシールド用導体には、導体付きテープ（金属箔テープ）を用いたもの、編組状の素線を用いたもの、また接地用のドレイン線等を付け合わせたものなどがある。 The shield conductor of the twinax cable includes a conductor using a tape with a conductor (metal foil tape), a conductor using a braided element wire, a conductor attached with a grounding drain wire, and the like.
一例として、特許文献１で開示されているツイナックスケーブルの横断面図を図８に示す。 As an example, a cross-sectional view of a twinax cable disclosed in Patent Document 1 is shown in FIG.
図８に示すツイナックスケーブル８１は、信号用導体８２を絶縁体８３で絶縁した２本の絶縁電線８４の周囲に、ポリエチレンのテープにアルミニウム等の金属箔を貼り付けた金属箔テープからなるシールド用導体８５を巻き付け、あるいは縦添えし、さらにそのシールド用導体８５の周囲に、ケーブル内部を保護するためのジャケット８６を被覆したものである。 A twinax cable 81 shown in FIG. 8 is a shield made of a metal foil tape in which a metal foil such as aluminum is bonded to a polyethylene tape around two insulated wires 84 in which a signal conductor 82 is insulated by an insulator 83. The conductor 85 is wound or vertically attached, and the shield conductor 85 is covered with a jacket 86 for protecting the inside of the cable.
シールド用導体８５と絶縁電線８４との間には、ドレイン線８７がシールド用導体８５の導電面（金属箔）と接触するように縦添えされ、このドレイン線８７がグランド接続されるようになっている。 A drain line 87 is vertically provided between the shield conductor 85 and the insulated wire 84 so as to contact the conductive surface (metal foil) of the shield conductor 85, and the drain line 87 is grounded. ing.
ところで、数Ｇｂｐｓ以上の高速信号を伝送するためには、２本の信号用導体における２つの信号の伝搬時間の差、すなわちスキューを低減する必要がある。これは、スキューが増加すると、受信側で２つの信号の差分を合成出力したデジタル信号の波形を崩してしまうためである。例えば、１０Ｇｂｐｓ相当の高速信号伝送においては、数ｐｓのスキューでも信号品質を劣化させてしまう。また、最近は、ＥＭＩ（Electromagnetic Interference；電磁波妨害）を低減する必要から、差動・同相変換量を低く抑えることも要求されている。 By the way, in order to transmit a high-speed signal of several Gbps or more, it is necessary to reduce a difference in propagation time of two signals in two signal conductors, that is, a skew. This is because when the skew increases, the waveform of the digital signal obtained by synthesizing and outputting the difference between the two signals on the receiving side is destroyed. For example, in high-speed signal transmission corresponding to 10 Gbps, signal quality is deteriorated even with a skew of several ps. Recently, since it is necessary to reduce EMI (Electromagnetic Interference), it is also required to reduce the amount of differential / in-phase conversion.
図９に示すツイナックスケーブル９１は、２本の信号用導体９２を、絶縁体９３で一度に被覆し、この絶縁体９３の周囲に金属箔テープからなるシールド用導体９４を巻き付け、あるいは縦添えし、さらにそのシールド用導体９４の周囲に、ケーブル内部を保護するためのジャケット９５を被覆したものである（特許文献２）。 In the twinax cable 91 shown in FIG. 9, two signal conductors 92 are covered with an insulator 93 at one time, and a shield conductor 94 made of a metal foil tape is wound around the insulator 93 or vertically attached. Furthermore, a jacket 95 for protecting the inside of the cable is covered around the shield conductor 94 (Patent Document 2).
このツイナックスケーブル９１では、２本の信号用導体９２をひとつの絶縁体９３で一括被覆することで、絶縁体９３の誘電率差を抑えて、スキューを低減している。 In this twinax cable 91, the two signal conductors 92 are collectively covered with one insulator 93, so that the dielectric constant difference of the insulator 93 is suppressed and the skew is reduced.
図１０に示すツイナックスケーブル１０１は、信号用導体１０２を絶縁体１０３により被覆した２本の絶縁電線１０４の周囲を発泡剤テープ１０５で覆い、その発泡剤テープ１０５の周囲に金属箔テープからなるシールド用導体１０６を被覆し、さらにその周囲にジャケット１０７を被覆したものである。発泡剤テープ１０５とシールド用導体１０６との間には、ドレイン線１０８が、シールド用導体１０６の導体面（金属箔）と接触するように縦添えされている（特許文献３）。 A twinax cable 101 shown in FIG. 10 is formed by covering the periphery of two insulated wires 104 in which a signal conductor 102 is covered with an insulator 103 with a foaming agent tape 105 and forming a metal foil tape around the foaming agent tape 105. A shield conductor 106 is covered and a jacket 107 is covered around the shield conductor 106. Between the foaming agent tape 105 and the shield conductor 106, a drain wire 108 is vertically attached so as to be in contact with the conductor surface (metal foil) of the shield conductor 106 (Patent Document 3).
このツイナックスケーブル１０１では、２本の絶縁電線１０４をシールド用導体１０６で覆う前に、絶縁体である発泡剤テープ１０５を巻き付け、信号用導体１０２とシールド用導体１０６との距離を相対的に離すことで、両信号用導体１０２の電磁結合（電磁気的結合）を強くし、スキューを低減している。 In this twinax cable 101, before covering the two insulated wires 104 with the shield conductor 106, the foaming tape 105 as an insulator is wrapped, and the distance between the signal conductor 102 and the shield conductor 106 is relatively set. By separating, the electromagnetic coupling (electromagnetic coupling) between the signal conductors 102 is strengthened, and the skew is reduced.
図１１に示すツイナックスケーブル１１１は、信号用導体１１２を発泡体からなる絶縁体１１３で被覆した２本の絶縁電線１１４の周囲に、金属箔テープからなるシールド用導体１１５を巻き付け、あるいは縦添えし、さらにそのシールド用導体１１５の周囲にジャケット１１６を被覆したものである（特許文献４）。 In the twinax cable 111 shown in FIG. 11, a shield conductor 115 made of a metal foil tape is wound around or vertically attached around two insulated wires 114 in which a signal conductor 112 is covered with an insulator 113 made of foam. Further, a jacket 116 is covered around the shield conductor 115 (Patent Document 4).
このツイナックスケーブル１１１では、絶縁体１１３を発泡体で形成し、２本の絶縁電線１１４をテープ状のシールド用導体１１５で被覆する際、絶縁体１１３が少し潰れるくらいにきつく巻いて、信号用導体１１２同士の距離を小さくしている。これによって、両信号用導体１１２の電磁結合が強くなり、スキューが小さくなる。 In this twinax cable 111, the insulator 113 is formed of a foam, and when the two insulated wires 114 are covered with the tape-shaped shield conductor 115, the insulator 113 is wound so tightly as to be slightly crushed, so that the signal The distance between the conductors 112 is reduced. As a result, the electromagnetic coupling between the two signal conductors 112 is strengthened, and the skew is reduced.
しかしながら、図９のツイナックスケーブル９１では、２本の信号用導体９２をひとつの絶縁体９３で一括被覆することでスキューを低減しているが、単に絶縁体９３で一括被覆するだけでは、絶縁体９３内部の誘電率分布や、シールド形状の左右の対称性のズレが僅かに残るため、１０Ｇｂｐｓ相当の高速信号の伝送においては、スキュー、差動・同相変換量ともに十分な低減効果が得られない。 However, in the twinax cable 91 of FIG. 9, the skew is reduced by collectively covering the two signal conductors 92 with one insulator 93, but by simply covering the two with the insulator 93, insulation is achieved. In the transmission of high-speed signals corresponding to 10 Gbps, the skew, differential / in-phase conversion amount can be sufficiently reduced, because the dielectric constant distribution inside the body 93 and the left / right symmetry deviation of the shield shape remain slightly. Absent.
また、図１０のツイナックスケーブル１０１では、発泡剤テープ１０５を巻く工程が増えるので、コストの増加が避けられない。さらに、発泡剤テープ１０５の厚さが０．２ｍｍと、ある程度厚い発泡剤テープ１０５を使用しないとスキュー低減の効果が得られないため、発泡剤テープ１０５の重なり具合によって、左右の対称性が崩れ、スキューや差動・同相変換量が増大したり、特性インピーダンスが変動してしまうという問題が発生する。したがって、発泡剤テープ１０５の重なり具合を精密に制御する必要があるが、実際の工程では非常に困難である。 Further, in the twinax cable 101 of FIG. 10, the process of winding the foaming agent tape 105 is increased, and thus an increase in cost is inevitable. Further, since the thickness of the foaming agent tape 105 is 0.2 mm and the foaming tape 105 is not thick enough, the effect of reducing the skew cannot be obtained. There arises a problem that the skew, the differential / in-phase conversion amount increases, and the characteristic impedance fluctuates. Accordingly, it is necessary to precisely control the overlapping state of the foaming agent tape 105, but it is very difficult in an actual process.
さらに、図１１のツイナックスケーブル１１１では、テープ状のシールド用導体１１５を巻き付けることで絶縁体１１３を潰しているが、信号用導体１１２同士の距離の制御が難しく、左右の対称性が崩れたりすることで、スキューや差動・同相変換量の増大、特性インピーダンスの変動などの問題が発生する。 Further, in the twinax cable 111 of FIG. 11, the insulator 113 is crushed by winding the tape-shaped shield conductor 115, but it is difficult to control the distance between the signal conductors 112, and the left-right symmetry is lost. As a result, problems such as an increase in skew, differential / common-mode conversion, and fluctuations in characteristic impedance occur.
また、電気特性の面において、両信号用導体の電磁結合を強くするには、ケーブル外径を大きくするか、信号用導体を細くしないと、所望の特性インピーダンス（差動インピーダンス）にすることができないという問題もある。つまり、ケーブル外径を変更しない場合には、信号用導体を細くしなければならないので、ケーブルの伝送損失の増大が避けられない。さらに、電磁結合が強過ぎる場合には、同相の特性インピーダンスが大きくなるので、同相入力成分に対して特性インピーダンスが不整合となる。その結果、同相成分の反射を引き起こし、ＥＭＩ等の問題が発生する。 In addition, in terms of electrical characteristics, in order to strengthen the electromagnetic coupling between the two signal conductors, the desired characteristic impedance (differential impedance) can be obtained unless the cable outer diameter is increased or the signal conductor is reduced. There is also a problem that it cannot be done. In other words, if the outer diameter of the cable is not changed, the signal conductor must be thinned, so an increase in cable transmission loss is inevitable. Further, when the electromagnetic coupling is too strong, the characteristic impedance of the in-phase is increased, so that the characteristic impedance is mismatched with respect to the in-phase input component. As a result, in-phase component reflection occurs, and problems such as EMI occur.
また、実装面において、両信号用導体の電磁結合を強くするには、信号用導体の間隔をケーブル外径に対して相対的に狭くする必要があるが、ツイナックスケーブルを基板やコネクタにハンダ付け等で実装する際に、接続ピッチが小さくなり、接続作業が困難となる問題がある。 In order to strengthen the electromagnetic coupling between the two signal conductors on the mounting surface, the distance between the signal conductors needs to be relatively narrow with respect to the cable outer diameter, but the twinax cable is soldered to the board or connector. When mounting by attaching, etc., there is a problem that the connection pitch becomes small and the connection work becomes difficult.
通常、ドレイン線は左右の対称性と位置の安定性を考慮して２本の絶縁電線の間に配置される（図８、図１０参照）が、接続ピッチが小さい場合（つまり信号用導体の間隔が狭い場合）には、そのままの配置での接続が困難になり、シールド用導体をある程度引き剥がして信号用導体の脇までドレイン線を引き出した状態で、両信号用導体とドレイン線をハンダ付けするといった方法をとらなければならない。ドレイン線を長く引き出すことにより、グランドが不安定になり、電気特性を損なってしまう。 Normally, the drain line is arranged between two insulated wires in consideration of left-right symmetry and positional stability (see FIGS. 8 and 10), but when the connection pitch is small (that is, the signal conductor) When the interval is narrow), it becomes difficult to connect in the same arrangement, and the signal conductor and the drain line are soldered in a state where the shield conductor is peeled off to some extent and the drain line is pulled out to the side of the signal conductor. You have to take the method of attaching. If the drain line is extended for a long time, the ground becomes unstable and the electrical characteristics are impaired.
そこで、本発明の目的は、上記課題を解決し、数Ｇｂｐｓ以上の高速伝送に用いられる差動信号用ケーブルにおいて、スキュー及び差動・同相変換量、伝送損失を共に低減し、ＥＭＩ性能が良好であり、伝送特性を決定する特性インピーダンスが逐次変動せず安定的な生産が可能であり、かつ、基板やコネクタ等への実装も容易で実装部分での電気特性の劣化も小さく、信号波形劣化の小さい差動信号用ケーブル及びこれを用いた伝送ケーブル、並びに差動信号用ケーブルの製造方法を提供することにある。 Therefore, the object of the present invention is to solve the above-mentioned problems and reduce both skew, differential / in-phase conversion amount and transmission loss in a differential signal cable used for high-speed transmission of several Gbps or more, and good EMI performance. The characteristic impedance that determines the transmission characteristics does not fluctuate sequentially and can be stably produced, and can be easily mounted on a board or connector, with little deterioration in electrical characteristics in the mounting area, and signal waveform deterioration. It is an object of the present invention to provide a differential signal cable, a transmission cable using the same, and a method for manufacturing a differential signal cable.
本発明は上記目的を達成するために創案されたものであり、並行に設けられた１対の信号用導体と、該１対の信号用導体の周囲を一括して被覆する絶縁体と、該絶縁体の外周に設けられたシールド用導体とを備え、１０Ｇｂｐｓ以上の高速伝送に用いられる差動信号用ケーブルにおいて、前記１対の信号用導体の間隔を、偶モードインピーダンスが奇モードインピーダンスの１．５から１．９倍となる間隔とした差動信号用ケーブルである。 The present invention was devised to achieve the above object, and includes a pair of signal conductors provided in parallel, an insulator that collectively covers the periphery of the pair of signal conductors, A differential signal cable having a shield conductor provided on an outer periphery of an insulator and used for high-speed transmission of 10 Gbps or more, wherein the even-mode impedance is an odd-mode impedance of 1 This is a differential signal cable having an interval of 0.5 to 1.9 times.
前記絶縁体は、前記１対の信号用導体を並べた方向である幅方向の長さが、幅方向と垂直な厚さ方向の長さよりも大きく形成され、前記１対の信号用導体は、前記絶縁体の厚さ方向の中心に配置されてもよい。 The insulator is formed such that the length in the width direction, which is the direction in which the pair of signal conductors are arranged, is larger than the length in the thickness direction perpendicular to the width direction, and the pair of signal conductors is You may arrange | position in the center of the thickness direction of the said insulator.
前記絶縁体の幅方向の長さと厚さ方向の長さの比が２：１であるとよい。 The ratio of the length in the width direction and the length in the thickness direction of the insulator is preferably 2: 1.
前記絶縁体の幅方向の片側あるいは両側の端部にドレイン線を縦添えに配置し、前記絶縁体と前記ドレイン線の周囲に前記シールド用導体を設けると共に、前記ドレイン線と前記シールド用導体とを電気的に接続してもよい。 A drain line is vertically arranged at one or both ends in the width direction of the insulator, the shield conductor is provided around the insulator and the drain line, and the drain line and the shield conductor May be electrically connected.
前記ドレイン線と前記信号用導体は、前記絶縁体の幅方向に沿って一直線状に配置されてもよい。 The drain line and the signal conductor may be arranged in a straight line along the width direction of the insulator.
前記絶縁体の幅方向の両側の端部に前記ドレイン線をそれぞれ配置すると共に、両前記ドレイン線を前記絶縁体の幅方向に沿って一直線状に配置し、かつ、両前記ドレイン線を、前記絶縁体の厚さ方向の中心からずれた位置に配置してもよい。 The drain lines are arranged at both ends in the width direction of the insulator, the drain lines are arranged in a straight line along the width direction of the insulator, and both the drain lines are You may arrange | position in the position shifted | deviated from the center of the thickness direction of an insulator.
前記絶縁体の幅方向の片側あるいは両側の端部に、前記ドレイン線を嵌め込むための嵌め込み溝を形成し、該嵌め込み溝に前記ドレイン線を嵌め込み固定してもよい。 A fitting groove for fitting the drain wire may be formed at one or both ends in the width direction of the insulator, and the drain wire may be fitted and fixed in the fitting groove.
また、本発明は、前記差動信号用ケーブルを少なくとも２本以上束ね、その周囲に一括シールド用導体を設けると共に、その一括シールド用導体の外周に絶縁体からなるジャケットを被覆した伝送ケーブルである。 Further, the present invention is a transmission cable in which at least two differential signal cables are bundled, a collective shield conductor is provided around the cable, and an outer jacket of the collective shield conductor is covered with an insulating jacket. .
また、本発明は、並行に設けられた１対の信号用導体と、該１対の信号用導体の周囲を一括して被覆する絶縁体と、該絶縁体の外周に設けられたシールド用導体とを備え、１０Ｇｂｐｓ以上の高速伝送に用いられる差動信号用ケーブルの製造方法において、前記１対の信号用導体を、偶モードインピーダンスが奇モードインピーダンスの１．５から１．９倍となる間隔に配置し、該１対の信号用導体の周囲に押出成形により前記絶縁体を一括被覆する差動信号用ケーブルの製造方法である。 The present invention also provides a pair of signal conductors provided in parallel, an insulator that collectively covers the periphery of the pair of signal conductors, and a shield conductor provided on the outer periphery of the insulator. In the method for manufacturing a differential signal cable used for high-speed transmission of 10 Gbps or more, the pair of signal conductors are spaced apart with an even mode impedance of 1.5 to 1.9 times the odd mode impedance. And a differential signal cable manufacturing method in which the insulator is collectively covered by extrusion molding around the pair of signal conductors.
本発明によれば、スキュー及び差動・同相変換量、伝送損失を共に低減し、ＥＭＩ性能が良好であり、伝送特性を決定する特性インピーダンスが逐次変動せず安定的な生産が可能であり、かつ、基板やコネクタ等への実装も容易で実装部分での電気特性の劣化も小さく、信号波形劣化の小さい差動信号用ケーブル及びこれを用いた伝送ケーブル、並びに差動信号用ケーブルの製造方法を提供できる。 According to the present invention, both skew, differential / common-mode conversion amount, transmission loss are reduced, EMI performance is good, characteristic impedance that determines transmission characteristics does not fluctuate successively, and stable production is possible. In addition, a differential signal cable that can be easily mounted on a substrate, a connector, etc., has little deterioration in electrical characteristics in the mounting portion, and has little signal waveform deterioration, a transmission cable using the same, and a method for manufacturing the differential signal cable Can provide.
以下、本発明の好適な実施の形態を添付図面にしたがって説明する。 Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
図１は、本実施の形態に係る差動信号用ケーブルの横断面図である。 FIG. 1 is a cross-sectional view of a differential signal cable according to the present embodiment.
図１に示すように、差動信号用ケーブル１は、並行に設けられた１対の信号用導体２と、両信号用導体２の周囲を一括して被覆する所定の誘電率を有する絶縁体３と、絶縁体３の外周に設けられたシールド用導体４と、絶縁体３とシールド用導体４の間に縦添えされたグランド接続用のドレイン線５と、シールド用導体４の外周を設けられたケーブル保護用のジャケット６とを備えている。 As shown in FIG. 1, a differential signal cable 1 includes a pair of signal conductors 2 provided in parallel and an insulator having a predetermined dielectric constant that collectively covers the periphery of both signal conductors 2. 3, a shield conductor 4 provided on the outer periphery of the insulator 3, a drain wire 5 for ground connection vertically provided between the insulator 3 and the shield conductor 4, and an outer periphery of the shield conductor 4. And a jacket 6 for protecting the cable.
信号用導体２としては、銅等の電気良導体、または、電気良導体にメッキ等を施した単線または撚線を用いる。 As the signal conductor 2, a good electric conductor such as copper or a single wire or a stranded wire obtained by plating the good electric conductor is used.
本実施の形態に係る差動信号用ケーブル１では、信号用導体２の間隔は、偶モードインピーダンスＺevenが奇モードインピーダンスＺoddの１．５から１．９倍となる間隔とされる。この理由については後述する。 In the differential signal cable 1 according to the present embodiment, the interval between the signal conductors 2 is such that the even mode impedance Z even is 1.5 to 1.9 times the odd mode impedance Z odd . The reason for this will be described later.
絶縁体３は、押出機により供給される絶縁樹脂で両信号用導体２を一括被覆することで形成される。 The insulator 3 is formed by collectively covering both signal conductors 2 with an insulating resin supplied by an extruder.
絶縁体３は、断面視で扁平状に形成される。１対の信号用導体２を並べた方向（図１では左右方向）を幅方向、幅方向と垂直な方向（図１では上下方向）を厚さ方向とすると、絶縁体３は、幅方向の長さ（以下、単に幅という）が、厚さ方向の長さ（以下、単に厚さという）よりも大きく形成される。 The insulator 3 is formed in a flat shape when viewed in cross section. When the direction in which the pair of signal conductors 2 are arranged (left and right in FIG. 1) is the width direction and the direction perpendicular to the width direction (up and down in FIG. 1) is the thickness direction, the insulator 3 is The length (hereinafter simply referred to as width) is formed to be greater than the length in the thickness direction (hereinafter simply referred to as thickness).
本実施の形態では、絶縁体３を、断面視で、略直線状の２つの辺と、この２つの辺を結ぶ曲線状の２辺とからなる形状に形成している。なお、絶縁体３を断面視で楕円形に形成してもよい。両信号用導体２は、絶縁体３の厚さ方向の中心に配置される。 In the present embodiment, the insulator 3 is formed in a shape composed of two substantially straight sides and two curved sides connecting the two sides in a sectional view. Note that the insulator 3 may be formed in an elliptical shape in a cross-sectional view. Both signal conductors 2 are arranged at the center of the insulator 3 in the thickness direction.
差動信号用ケーブル１は、実際には、送信用と受信用の２本を１組で使用することが多いので、２本合わせたときの断面を円形に近くするために、絶縁体３の幅と厚さの比は、２：１とすることが好ましい。 In practice, the differential signal cable 1 is often used as a pair of transmission and reception cables. Therefore, in order to make the cross-section of the two together close to a circle, the insulator 3 The ratio of width to thickness is preferably 2: 1.
絶縁体３に用いる絶縁樹脂としては、誘電率、誘電正接の小さいものが望ましく、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、パーフロロアルコキシ（ＰＦＡ）、ポリエチレン等を用いるとよい。 As the insulating resin used for the insulator 3, one having a low dielectric constant and dielectric loss tangent is desirable. For example, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), polyethylene, or the like may be used.
また、誘電率、誘電正接を小さくするため、絶縁体３に発泡絶縁樹脂を用いてもよい。絶縁体３に発泡絶縁樹脂を用いる場合、成形前に発泡剤を練り込み、成形時の温度によって発泡度を制御する方法、あるいは窒素等のガスを成形圧力で注入しておき、圧力解放時に発泡させる方法等で絶縁体３を形成するとよい。 In order to reduce the dielectric constant and the dielectric loss tangent, a foamed insulating resin may be used for the insulator 3. When using foamed insulating resin for the insulator 3, a foaming agent is kneaded before molding, and a method of controlling the degree of foaming according to the molding temperature, or a gas such as nitrogen is injected at the molding pressure, and foaming is performed when the pressure is released The insulator 3 may be formed by a method such as
絶縁体３の幅方向の片側の端部（図１では左側の端部）には、両信号用導体２と並行してドレイン線５が縦添え配置される。つまり、ドレイン線５と両信号用導体２は、絶縁体３の幅方向に沿って一直線状に配置される。ドレイン線５としては、信号用導体２と同様に、銅等の電気良導体、または、電気良導体にメッキ等を施した単線または撚線を用いる。 A drain line 5 is vertically arranged in parallel with both signal conductors 2 at one end of the insulator 3 in the width direction (the left end in FIG. 1). That is, the drain line 5 and both signal conductors 2 are arranged in a straight line along the width direction of the insulator 3. As the drain wire 5, similarly to the signal conductor 2, an electric good conductor such as copper, or a single wire or a stranded wire obtained by plating the electric good conductor is used.
シールド用導体４としては、ポリエチレンテープにアルミニウム等の金属箔を貼り合わせた金属箔テープを用いる。シールド用導体４はこれに限らず、編組状の素線からなるものを用いてもよい。 As the shield conductor 4, a metal foil tape in which a metal foil such as aluminum is bonded to a polyethylene tape is used. The shield conductor 4 is not limited to this, and a shield conductor 4 may be used.
シールド用導体４は、絶縁体３とドレイン線５の周囲に巻き付けられ、これにより、ドレイン線５は絶縁体３に固定される。このとき、シールド用導体４の導体面（金属箔）がドレイン線５に接触するように、シールド用導体４を巻き付ける。シールド用導体４の外周には、ケーブル保護のために、絶縁体からなるジャケット６が被覆される。 The shield conductor 4 is wound around the insulator 3 and the drain wire 5, whereby the drain wire 5 is fixed to the insulator 3. At this time, the shield conductor 4 is wound so that the conductor surface (metal foil) of the shield conductor 4 is in contact with the drain wire 5. The outer periphery of the shield conductor 4 is covered with a jacket 6 made of an insulator for protecting the cable.
図２に示すように、差動信号用ケーブル１をプリント基板２１に実装する際には、ジャケット６、シールド用導体４、絶縁体３を順次段剥きして、信号用導体２とドレイン線５を露出させ、この状態で、信号用導体２をプリント基板２１の信号用電極２２（Ｐ電極２２ａ、Ｎ電極２２ｂ）に、ドレイン線５をグランド用電極２３に合わせて、ハンダ付けで固定する。 As shown in FIG. 2, when the differential signal cable 1 is mounted on the printed circuit board 21, the jacket 6, the shield conductor 4, and the insulator 3 are sequentially stripped, and the signal conductor 2 and the drain line 5 are removed. In this state, the signal conductor 2 is fixed to the signal electrode 22 (P electrode 22a, N electrode 22b) of the printed board 21 and the drain line 5 is fixed to the ground electrode 23 by soldering.
このように、差動信号用ケーブル１では、信号用導体２とドレイン線５を露出させた状態でそのままハンダ付けすることが可能であり、信号用導体２の間隔が狭い場合であっても、ドレイン線５が邪魔することなく実装可能である。また、シールド用導体４の剥き長も小さいので、電気特性を損なわない。 Thus, the differential signal cable 1 can be soldered as it is with the signal conductor 2 and the drain line 5 exposed, and even if the distance between the signal conductors 2 is narrow, The drain line 5 can be mounted without obstruction. Moreover, since the stripping length of the shield conductor 4 is small, the electrical characteristics are not impaired.
ここで、信号用導体２の間隔を、偶モードインピーダンスＺevenが奇モードインピーダンスＺoddの１．５から１．９倍となる間隔とする理由を説明する。 Here, the reason why the interval between the signal conductors 2 is an interval at which the even mode impedance Z even is 1.5 to 1.9 times the odd mode impedance Z odd will be described.
差動信号用ケーブル１では、両信号用導体２の周囲に絶縁体３を押出成形により一括被覆するので、信号用導体２の間隔を自由に設定し、両信号用導体２の電磁結合を所望の量にすることが可能であるが、この信号用導体２の間隔は、スキュー及び差動・同相変換量の低減と、伝送損失の低減の両者を考慮して決定する必要がある。 In the differential signal cable 1, since the insulator 3 is collectively covered by extrusion molding around the signal conductors 2, the distance between the signal conductors 2 can be freely set, and electromagnetic coupling between the signal conductors 2 is desired. However, it is necessary to determine the distance between the signal conductors 2 in consideration of both the skew and the reduction of the differential / common-mode conversion amount and the reduction of the transmission loss.
例えば、電磁結合が全くない差動信号用ケーブルでは、ケーブル内部を伝搬する電磁波は、一方の信号用導体とシールド用導体の間と、他方の信号用導体とシールド用導体との間で別々に伝搬するため、各線路の伝搬定数の僅かな違いが、スキュー、差動・同相変換量の増大に影響することになる。つまり、両信号用導体の電磁結合が小さいほど、スキュー及び差動・同相変換量は増大する。 For example, in a differential signal cable having no electromagnetic coupling, electromagnetic waves propagating inside the cable are separately transmitted between one signal conductor and a shield conductor and between the other signal conductor and the shield conductor. In order to propagate, a slight difference in propagation constant of each line affects the increase in skew and differential / in-phase conversion amount. That is, the smaller the electromagnetic coupling between the two signal conductors, the greater the skew and the differential / in-phase conversion amount.
他方、両信号用導体の電磁結合が強い場合、ケーブル内部を伝搬する電磁波のうち信号用導体間を伝搬する成分が増大するので、スキューを低減でき、また差動・同相変換量も小さくできる。ただし、電磁界が信号用導体間に集中するため、ケーブルの伝送損失が増大する。さらに、両信号用導体の電磁結合が強い場合、ケーブルの同相インピーダンスが大きくなるため、同相入力成分に対して特性インピーダンスが不整合となり、その結果、同相成分の反射を引き起こしてＥＭＩの原因となる。つまり、両信号用導体の電磁結合が強いほど、伝送損失が増大し、ＥＭＩ性能も悪化する。 On the other hand, when the electromagnetic coupling between the two signal conductors is strong, the component propagating between the signal conductors of the electromagnetic wave propagating inside the cable increases, so that the skew can be reduced and the differential / in-phase conversion amount can be reduced. However, since the electromagnetic field is concentrated between the signal conductors, the transmission loss of the cable increases. Further, when the electromagnetic coupling between both signal conductors is strong, the common-mode impedance of the cable becomes large, so that the characteristic impedance is mismatched with respect to the common-mode input component, resulting in reflection of the common-mode component and causing EMI. . That is, the stronger the electromagnetic coupling between both signal conductors, the greater the transmission loss and the worse the EMI performance.
両信号用導体の電磁結合の度合いは、信号用導体の偶モードインピーダンスＺevenと奇モードインピーダンスＺoddの比（Ｚeven／Ｚodd）で規定することができる。偶モードインピーダンスＺevenとは、両信号用導体を位相差無しで励振した場合のグランドに対するインピーダンスであり、奇モードインピーダンスＺoddとは、両信号用導体を逆位相で励振した場合のグランドに対するインピーダンスである。 The degree of electromagnetic coupling between both signal conductors can be defined by the ratio (Z even / Z odd ) of the even mode impedance Z even and the odd mode impedance Z odd of the signal conductor. The even mode impedance Z even is the impedance with respect to the ground when both signal conductors are excited without phase difference, and the odd mode impedance Z odd is the impedance with respect to the ground when both signal conductors are excited with opposite phases. It is.
Ｚeven／Ｚoddは、信号用導体の間隔で調整可能であり、信号用導体の間隔を狭くするとＺeven／Ｚoddの値は高くなり、両信号用導体の電磁結合が強くなる。また、Ｚeven／Ｚoddは、信号用導体の外径でも調整可能である。なお、信号用導体の外径によるＺeven／Ｚoddの調整は、差動インピーダンスを１００Ωにする為に必要となる。 Z even / Z odd can be adjusted by the distance between the signal conductors. If the distance between the signal conductors is narrowed, the value of Z even / Z odd increases, and the electromagnetic coupling between both signal conductors becomes stronger. Z even / Z odd can also be adjusted by the outer diameter of the signal conductor. The adjustment of Z even / Z odd by the outer diameter of the signal conductor is necessary to make the differential impedance 100Ω.
両信号用導体の電磁結合の度合い（Ｚeven／Ｚodd）に対する、スキュー及び伝送特性（差動モード挿入損失Ｓdd21）の関係を解析した結果を図３に示す。 FIG. 3 shows the result of analyzing the relationship between skew and transmission characteristics (differential mode insertion loss S dd21 ) with respect to the degree of electromagnetic coupling (Z even / Z odd ) of both signal conductors.
図３に示すように、Ｚeven／Ｚoddが１．５未満では、スキューの低減効果が小さく、また、Ｚeven／Ｚoddが１．９を超えると、伝送特性（差動モード挿入損失Ｓdd21）の劣化が顕著である。したがって、スキューを低減し、かつ伝送特性の劣化を抑制するためには、信号用導体２の間隔を、Ｚeven／Ｚoddが１．５〜１．９となる間隔、すなわち、偶モードインピーダンスＺevenが奇モードインピーダンスＺoddの１．５から１．９倍となる間隔とすればよい。 As shown in FIG. 3, when Z even / Z odd is less than 1.5, the effect of reducing the skew is small, and when Z even / Z odd exceeds 1.9, transmission characteristics (differential mode insertion loss S The deterioration of dd21 ) is remarkable. Therefore, in order to reduce the skew and suppress the deterioration of the transmission characteristics, the interval between the signal conductors 2 is set to an interval where Z even / Z odd is 1.5 to 1.9, that is, even mode impedance Z The even number may be an interval that is 1.5 to 1.9 times the odd mode impedance Z odd .
一般的には、差動インピーダンスは１００Ωとするので、Ｚodd＝５０Ωとなり、Ｚeven＝７５〜９５Ωの範囲となる。 Generally, since the differential impedance is 100Ω, Z odd = 50Ω and Z even = 75 to 95Ω.
例えば、信号用導体２の実効外径を０．１８ｍｍとし、絶縁体３としてＰＦＡ（誘電率εr＝２．１）を用い、絶縁体３を幅１．４８ｍｍ、厚さ０．７４ｍｍとした場合、信号用導体２の間隔を０．３７５ｍｍとすると、信号用導体２の差動インピーダンス１００Ωで、同相インピーダンスが約４２Ωとなり、Ｚeven／Ｚodd＝１．６７となる。 For example, when the effective outer diameter of the signal conductor 2 is 0.18 mm, PFA (dielectric constant εr = 2.1) is used as the insulator 3, and the insulator 3 has a width of 1.48 mm and a thickness of 0.74 mm If the distance between the signal conductors 2 is 0.375 mm, the differential impedance of the signal conductors 2 is 100Ω, the in-phase impedance is about 42Ω, and Z even / Z odd = 1.67.
同様にして、サイズの異なる複数の差動信号用ケーブルについて、Ｚeven／Ｚodd、スキュー、差動モード挿入損失Ｓdd21、同相モード反射損失（リターンロス）Ｓcc11を解析した結果を表１に示す。なお、表１において、導体構成７／０．０８は、外径０．０８ｍｍの素線を７本撚って信号用導体を構成していることを表している。また、減衰量は、差動モード挿入損失Ｓdd21の絶対値と等しく、１ｍあたりの信号の減衰量を表す。 Similarly, Table 1 shows the results of analyzing Z even / Z odd , skew, differential mode insertion loss S dd21 , and common mode reflection loss (return loss) S cc11 for a plurality of differential signal cables of different sizes. Show. In Table 1, the conductor configuration 7 / 0.08 indicates that a signal conductor is formed by twisting seven strands having an outer diameter of 0.08 mm. The attenuation is equal to the absolute value of the differential mode insertion loss S dd21 and represents the attenuation of the signal per meter.
表１に示すように、Ｚeven／Ｚoddが１．５未満である３２ＡＷＧの差動信号用ケーブルでは、スキューが１８ｐｓ／ｍと大きくなっており、Ｚeven／Ｚoddが１．９を超える３６ＡＷＧ，３７ＡＷＧの差動信号用ケーブルでは、差動モード挿入損失Ｓdd21の絶対値である減衰量が４．８ｄＢ／ｍ、５．４ｄＢ／ｍと大きくなり、伝送特性が劣化している。さらに、Ｚeven／Ｚoddが１．９を超える３６ＡＷＧ、３７ＡＷＧの差動信号用ケーブルでは、同相モード反射損失Ｓcc11が−１０ｄＢ／ｍ以上となっており、ＥＭＩ性能が悪化している。 As shown in Table 1, in the differential signal cable of 32 AWG where Z even / Z odd is less than 1.5, the skew is as large as 18 ps / m, and Z even / Z odd exceeds 1.9. In the 36 AWG and 37 AWG differential signal cables, the attenuation, which is the absolute value of the differential mode insertion loss S dd21 , increases to 4.8 dB / m and 5.4 dB / m, and the transmission characteristics deteriorate. Furthermore, in the 36 AWG and 37 AWG differential signal cables with Z even / Z odd exceeding 1.9, the common-mode reflection loss S cc11 is −10 dB / m or more, and the EMI performance is deteriorated.
以上説明したように、本実施の形態に係る差動信号用ケーブル１では、信号用導体２の間隔を、偶モードインピーダンスが奇モードインピーダンスの１．５から１．９倍となる間隔としている。 As described above, in the differential signal cable 1 according to the present embodiment, the interval between the signal conductors 2 is set such that the even mode impedance is 1.5 to 1.9 times the odd mode impedance.
これにより、スキュー及び差動・同相変換量を低減し、かつ、伝送損失を実用上十分小さい領域に抑えることができ、かつ、ＥＭＩ性能を良好にでき、信号波形劣化を小さくできる。その結果、電子機器間あるいは電子機器内で数Ｇｂｐｓ以上の高速信号の伝送を行うことが可能となり、電子機器の性能向上に寄与する。 As a result, the skew and the amount of differential / in-phase conversion can be reduced, the transmission loss can be suppressed to a sufficiently small region in practice, the EMI performance can be improved, and the signal waveform deterioration can be reduced. As a result, it becomes possible to transmit high-speed signals of several Gbps or more between electronic devices or within electronic devices, which contributes to improving the performance of electronic devices.
また、差動信号用ケーブル１では、信号用導体２の周囲に押出成形により絶縁体３を一括被覆しているため、ケーブル長手方向の寸法変動を小さくでき、特性インピーダンスの変動を抑制できる。さらに、差動信号用ケーブル１では、押出成形時に信号用導体２の間隔を変更することで容易にＺeven／Ｚoddを調整できるので、従来のように厚手の発泡剤テープを巻いたり、テープ状のシールド用導体をきつく巻いて絶縁体を潰したりといった製法上困難な方法をとる必要がなくなり、安定的な生産が可能となる。 In the differential signal cable 1, since the insulator 3 is collectively covered around the signal conductor 2 by extrusion molding, dimensional fluctuation in the cable longitudinal direction can be reduced, and fluctuation in characteristic impedance can be suppressed. Further, in the differential signal cable 1, Z even / Z odd can be easily adjusted by changing the interval between the signal conductors 2 during extrusion molding. This eliminates the need for a difficult manufacturing method such as tightly winding the shield conductor and crushing the insulator, thereby enabling stable production.
また、差動信号用ケーブル１では、ドレイン線５を信号用導体２の横に配置しているため、信号用導体２の間隔が狭くても、基板やコネクタ等への実装が容易となり、さらには、シールド用導体４の剥き長が小さくて済むため、実装部分での電気特性劣化も小さい。 Further, in the differential signal cable 1, since the drain line 5 is arranged beside the signal conductor 2, even if the interval between the signal conductors 2 is narrow, it can be easily mounted on a board or a connector. Since the stripping length of the shield conductor 4 can be small, the deterioration of electrical characteristics at the mounting portion is also small.
次に、本発明の他の実施の形態を説明する。 Next, another embodiment of the present invention will be described.
図４に示す差動信号用ケーブル４１は、図１の差動信号用ケーブル１と基本的に同じ構造であり、絶縁体３の左右にドレイン線５を配置した点が異なる。両ドレイン線５と両信号用導体２は、絶縁体３の幅方向に沿って一直線状に配置される。 A differential signal cable 41 shown in FIG. 4 has basically the same structure as that of the differential signal cable 1 shown in FIG. 1 except that drain wires 5 are arranged on the left and right sides of the insulator 3. Both drain lines 5 and both signal conductors 2 are arranged in a straight line along the width direction of the insulator 3.
差動信号用ケーブル４１では、ドレイン線５を左右対称に配置しているため、信号用導体２を伝搬する電磁波の左右の対称性が良好となり、スキュー及び差動・同相変換量をより低減できる。 In the differential signal cable 41, since the drain lines 5 are symmetrically arranged, the left and right symmetry of the electromagnetic wave propagating through the signal conductor 2 is improved, and the skew and the differential / in-phase conversion amount can be further reduced. .
図５に示す差動信号用ケーブル５１は、図４の差動信号用ケーブル４１において、絶縁体３の幅方向の両側の端部にドレイン線５を嵌め込むための嵌め込み溝３ａを長手方向に沿って形成し、嵌め込み溝３ａにドレイン線５を嵌め込み固定したものである。 The differential signal cable 51 shown in FIG. 5 has, in the differential signal cable 41 of FIG. 4, insertion grooves 3 a for inserting the drain wires 5 into the ends on both sides in the width direction of the insulator 3 in the longitudinal direction. The drain wire 5 is fitted and fixed in the fitting groove 3a.
嵌め込み溝３ａは、例えば、絶縁体３を押出成形する際に、押出機の排出部の一部（嵌め込み溝３ａを形成する部分）に突起をつけておくことで容易に形成できる。嵌め込み溝３ａの深さは、ドレイン線５がシールド用導体４によって押さえつけられる程度に、また、シールド用導体４の導体面（金属箔）が十分ドレイン線５と接触するように、あまり深くならないようにする。 The fitting groove 3a can be easily formed, for example, by providing a protrusion on a part of the discharge portion of the extruder (a part for forming the fitting groove 3a) when the insulator 3 is extruded. The depth of the fitting groove 3a is not so deep that the drain wire 5 is pressed down by the shield conductor 4 and that the conductor surface (metal foil) of the shield conductor 4 is sufficiently in contact with the drain wire 5. To.
差動信号用ケーブル５１では、ドレイン線５が、絶縁体３に形成された嵌め込み溝３ａに嵌め込み固定されるので、ドレイン線５の位置が安定する。よって、ケーブル断面構造の左右の対称性が保たれ、信号用導体２を伝搬する電磁波の左右の対称性が良好となり、スキュー及び差動・同相変換量をより低減できる。また、ドレイン線５のズレによる製品不良を大幅に低減でき、差動信号用ケーブル５１の生産速度を上げることが可能になる。 In the differential signal cable 51, the drain line 5 is fitted and fixed in the fitting groove 3a formed in the insulator 3, so that the position of the drain line 5 is stabilized. Therefore, the left-right symmetry of the cable cross-sectional structure is maintained, the left-right symmetry of the electromagnetic wave propagating through the signal conductor 2 is improved, and the skew and the differential / in-phase conversion amount can be further reduced. Further, product defects due to the deviation of the drain line 5 can be greatly reduced, and the production speed of the differential signal cable 51 can be increased.
図６に示す差動信号用ケーブル６１は、図５の差動信号用ケーブル５１において、ドレイン線５を嵌め込むための嵌め込み溝３ａを、絶縁体３の厚さ方向の中心ではなく、絶縁体３の厚さ方向の中心からずれた位置（図６では下にずれた位置）に形成したものである。 The differential signal cable 61 shown in FIG. 6 is different from the differential signal cable 51 of FIG. 5 in that the fitting groove 3a for fitting the drain wire 5 is not the center in the thickness direction of the insulator 3, but the insulator. 3 is formed at a position shifted from the center in the thickness direction (position shifted downward in FIG. 6).
すなわち、差動信号用ケーブル６１では、両ドレイン線５が、絶縁体３の厚さ方向の中心からずれた位置に配置される。両ドレイン線５は、絶縁体３の幅方向に沿って一直線状に配置される。 That is, in the differential signal cable 61, both the drain lines 5 are arranged at positions shifted from the center in the thickness direction of the insulator 3. Both drain lines 5 are arranged in a straight line along the width direction of the insulator 3.
従来の２本の絶縁電線を備えた差動信号用ケーブル（例えば図８参照）では、絶縁電線を色違いにすることで信号用導体の極性を識別することが可能であるが、２本の信号用導体を１つの絶縁体で一括被覆した場合、信号用導体の極性を識別することが困難となり、差動信号用ケーブルをプリント基板等に実装する際の作業効率が悪化する。 In a conventional differential signal cable having two insulated wires (see, for example, FIG. 8), the polarity of the signal conductor can be identified by making the insulated wires different in color. When the signal conductors are collectively covered with one insulator, it is difficult to identify the polarity of the signal conductors, and the working efficiency when the differential signal cables are mounted on a printed board or the like is deteriorated.
差動信号用ケーブル６１では、ドレイン線５がケーブル断面の厚さ方向の中心になく、一方にずれているので、実装時にジャケット６、シールド用導体４を剥いた後、ドレイン線５の位置を確認することで、信号用導体２の極性を識別することが可能となる。つまり、差動信号用ケーブル６１によれば、信号用導体２の極性を容易に識別することが可能となり、ケーブル実装時における作業性が向上する。 In the differential signal cable 61, the drain wire 5 is not centered in the thickness direction of the cable cross section and is shifted to one side. Therefore, after the jacket 6 and the shield conductor 4 are peeled off during mounting, the position of the drain wire 5 is changed. By checking, the polarity of the signal conductor 2 can be identified. That is, according to the differential signal cable 61, the polarity of the signal conductor 2 can be easily identified, and workability at the time of cable mounting is improved.
図７に示す伝送ケーブル７１は、図６の差動信号用ケーブル６１（ジャケット６を省いたもの）を２本束ね、その周囲に一括シールド用導体７２を設けると共に、その一括シールド用導体７２の外周に絶縁体からなるジャケット７３を被覆したものである。 A transmission cable 71 shown in FIG. 7 is a bundle of two differential signal cables 61 (without the jacket 6) shown in FIG. 6 and a collective shield conductor 72 is provided around the cable 61. The outer periphery is covered with a jacket 73 made of an insulator.
差動信号用ケーブル６１は、その２本のドレイン線５を配置した側を向き合わせて束ねられる。ここでは、一括シールド用導体７２として、編組状の素線７２ａからなるものを用いたが、金属箔テープを用いるようにしてもよい。 The differential signal cable 61 is bundled by facing the side where the two drain wires 5 are arranged. Here, as the collective shield conductor 72, a braided strand 72a is used, but a metal foil tape may be used.
伝送ケーブル７１では、信号伝送用として、送信用に差動信号用ケーブル６１を１本、受信用に差動信号用ケーブル６１を１本備えており、さらに、ＥＭＩ及びＥＭＣ（Electromagnetic Compatibility）対策のために、両差動信号用ケーブル６１を一括シールド用導体７２で覆っており、伝送特性とＥＭＩ及びＥＭＣ性能の両立をコンパクトに実現している。 The transmission cable 71 includes one differential signal cable 61 for transmission and one differential signal cable 61 for reception for signal transmission, and further measures against EMI and EMC (Electromagnetic Compatibility). Therefore, both the differential signal cables 61 are covered with the collective shield conductor 72, so that both the transmission characteristics and the EMI and EMC performance can be realized in a compact manner.
このように、伝送ケーブル７１によれば、伝送特性とＥＭＩ及びＥＭＣ性能を両立できるので、伝送ケーブル７１の両端にＳＦＰ＋トランシーバ（光モジュール形状のコネクタ）を設けることで、１０ＧｂＥ用のダイレクトアタッチケーブルとして用いることも可能である。 Thus, according to the transmission cable 71, both transmission characteristics and EMI and EMC performance can be achieved. Therefore, by providing an SFP + transceiver (optical module-shaped connector) at both ends of the transmission cable 71, a direct attach cable for 10 GbE is provided. It is also possible to use it.
ここでは、伝送ケーブル７１として、２本の差動信号用ケーブル６１を用いる場合を説明したが、差動信号用ケーブル６１を３本以上用いるようにしてもよいし、差動信号用ケーブル６１に替えて、図１の差動信号用ケーブル１、図４の差動信号用ケーブル４１，あるいは図５の差動信号用ケーブル５１を用いてもよい。 Here, the case where two differential signal cables 61 are used as the transmission cable 71 has been described, but three or more differential signal cables 61 may be used. Instead, the differential signal cable 1 in FIG. 1, the differential signal cable 41 in FIG. 4, or the differential signal cable 51 in FIG. 5 may be used.
本発明は上記実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々の変更を加え得ることは勿論である。 The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.
１ 差動信号用ケーブル
２ 信号用導体
３ 絶縁体
４ シールド用導体
５ ドレイン線
６ ジャケット
1 Cable for differential signal 2 Signal conductor 3 Insulator 4 Shield conductor 5 Drain wire 6 Jacket
Claims (9)
前記１対の信号用導体の間隔を、偶モードインピーダンスが奇モードインピーダンスの１．５から１．９倍となる間隔としたことを特徴とする差動信号用ケーブル。 A pair of signal conductors provided in parallel, an insulator that collectively covers the periphery of the pair of signal conductors, and a shield conductor provided on the outer periphery of the insulator, and 10 Gbps or more In the differential signal cable used for high-speed transmission of
The differential signal cable according to claim 1, wherein an interval between the pair of signal conductors is an interval in which an even mode impedance is 1.5 to 1.9 times an odd mode impedance.
前記１対の信号用導体は、前記絶縁体の厚さ方向の中心に配置される請求項１記載の差動信号用ケーブル。 The insulator is formed such that a length in a width direction, which is a direction in which the pair of signal conductors are arranged, is larger than a length in a thickness direction perpendicular to the width direction,
The differential signal cable according to claim 1, wherein the pair of signal conductors is disposed at a center in a thickness direction of the insulator.
前記１対の信号用導体を、偶モードインピーダンスが奇モードインピーダンスの１．５から１．９倍となる間隔に配置し、該１対の信号用導体の周囲に押出成形により前記絶縁体を一括被覆することを特徴とする差動信号用ケーブルの製造方法。 A pair of signal conductors provided in parallel, an insulator that collectively covers the periphery of the pair of signal conductors, and a shield conductor provided on the outer periphery of the insulator, and 10 Gbps or more In the method of manufacturing a differential signal cable used for high-speed transmission of
The pair of signal conductors are arranged at an interval where the even mode impedance is 1.5 to 1.9 times the odd mode impedance, and the insulators are collectively formed around the pair of signal conductors by extrusion molding. A method for manufacturing a cable for differential signal, characterized in that:
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