JP2014110544A - Communication network - Google Patents

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JP2014110544A
JP2014110544A JP2012264205A JP2012264205A JP2014110544A JP 2014110544 A JP2014110544 A JP 2014110544A JP 2012264205 A JP2012264205 A JP 2012264205A JP 2012264205 A JP2012264205 A JP 2012264205A JP 2014110544 A JP2014110544 A JP 2014110544A
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communication network
transmission line
branch point
resistors
nodes
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JP6013158B2 (en
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Hiroyuki Mori
寛之 森
Keigo Takahashi
佳吾 高橋
Hideki Goto
英樹 後藤
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Toyota Motor Corp
Soken Inc
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Nippon Soken Inc
Toyota Motor Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a communication network capable of effectively suppressing distortion in waveform.SOLUTION: In a communication network 1, a plurality of nodes 10 configured to transmit and receive signals are connected via a transmission line 20 using a differential signal line. The communication network 1 includes a plurality of branch points 31-3n, at which the transmission line 20 branches off, and a plurality of resistances R1-Rn configured to connect differential signal lines of the branch points to the plurality of branch points 31-3n, respectively. A synthetic resistance value of the resistances R1-Rn, when all the resistances are connected in parallel, is set to a value approximately 1/2 of a characteristic impedance of the transmission line 20.

Description

本発明は、有線通信が可能な通信ネットワークに関し、より特定的には、多数のノードが接続された通信ネットワークにおける終端抵抗の設定技術に関する。   The present invention relates to a communication network capable of wired communication, and more particularly, to a termination resistance setting technique in a communication network in which a large number of nodes are connected.

有線通信が可能な通信ネットワークの１つとして、例えば自動車に搭載されるＬＡＮ（Local Area Network）に用いられるコントローラエリアネットワーク（Controller Area Network；ＣＡＮ）が知られている。このＣＡＮは、信号を送受信する複数のノードが差動伝送線路を介して接続される通信ネットワークである。   As one of communication networks capable of wired communication, for example, a controller area network (CAN) used for a LAN (Local Area Network) mounted in an automobile is known. The CAN is a communication network in which a plurality of nodes that transmit and receive signals are connected via a differential transmission line.

この有線通信が可能な通信ネットワークでは、通常、伝送線路の両端にこの伝送線路が有する特性インピーダンスと同じ値の終端抵抗をそれぞれ設け、伝送線路で生じる反射波に起因する波形歪を抑制することを行っている。   In a communication network capable of wired communication, normally, termination resistors having the same value as the characteristic impedance of the transmission line are provided at both ends of the transmission line to suppress waveform distortion caused by the reflected wave generated in the transmission line. Is going.

しかし、車載ＬＡＮに用いられるＣＡＮのように多数のノードが接続された通信ネットワークでは、終端抵抗が設けられるノードは低インピーダンスであるが、終端抵抗が設けられないノードは高インピーダンスとなり、大きな反射歪が生じる可能性がある。また、終端抵抗が設けられないノード間では、生じた反射歪の収束時間が長くなる場合がある。さらに、反射歪の大きさによって通信信号にビット誤りが生じるため、配索規模（ノード数、配線長、分岐数など）や通信速度が制限されることになる。   However, in a communication network in which a large number of nodes are connected, such as a CAN used in an in-vehicle LAN, a node provided with a termination resistor has a low impedance, but a node without a termination resistor has a high impedance, resulting in a large reflection distortion. May occur. In addition, the convergence time of the generated reflection distortion may be long between nodes where no termination resistor is provided. Furthermore, since a bit error occurs in the communication signal due to the magnitude of the reflection distortion, the arrangement scale (number of nodes, wiring length, number of branches, etc.) and communication speed are limited.

そこで、通信ネットワークで生じる波形歪を抑制する技術として、特許文献１において終端抵抗の決定手法が提案されている。この特許文献１では、他ノードまでの距離総和が長いノードほど大きな重みを付与し、伝送線路の特性インピーダンスの１／２と重みに比例した定数とを乗算した値を各ノードの終端抵抗として設定する。これにより、他ノードまでの距離総和が長いノードほど特性インピーダンスに近い値の終端抵抗が接続されることになり、波形歪が抑制されるという効果を発揮する。   Thus, as a technique for suppressing waveform distortion that occurs in a communication network, Patent Document 1 proposes a method for determining a termination resistance. In Patent Document 1, a node having a longer total distance to other nodes is given a greater weight, and a value obtained by multiplying 1/2 of the characteristic impedance of the transmission line and a constant proportional to the weight is set as a termination resistance of each node. To do. As a result, a terminal resistor having a value closer to the characteristic impedance is connected to a node having a longer total distance to other nodes, and the effect of suppressing waveform distortion is exhibited.

特表２００９−５０５４７０号公報Special table 2009-505470

上記特許文献１に記載の技術は、他ノードまでの距離総和が長いノードほど波形歪が大きいという仮定に基づいて提案された技術である。しかしながら、現実には、他ノードまでの距離総和が長いノードほど波形歪が大きいとは限らないため、波形歪抑制の実効性に課題が残る。   The technique described in Patent Document 1 is a technique proposed based on the assumption that a node having a longer total distance to another node has a larger waveform distortion. However, in reality, a node having a longer total distance to other nodes does not necessarily have a larger waveform distortion, and thus there remains a problem in the effectiveness of waveform distortion suppression.

それ故に、本発明の目的は、波形歪抑制の実効性が高い通信ネットワークを提供することである。   Therefore, an object of the present invention is to provide a communication network that is highly effective in suppressing waveform distortion.

本発明は、信号を送受信する複数のノードが差動伝送線路を介して接続される通信ネットワークに向けられている。そして、上記目的を達成するために、本発明の通信ネットワークは、伝送線路が分岐する分岐点を３つ以上有し、３つ以上の分岐点のそれぞれに設けられ、その各分岐点の差動線間を接続する３つ以上の抵抗を備えている。この３つ以上の抵抗は、全ての抵抗を並列接続したときの合成抵抗値が、伝送線路が有する特性インピーダンスの略１／２の値に設定されている。
かかる構成により、ノード間で生じる反射波が分岐点に設けられた抵抗を必ず通過するため、反射波のエネルギーが抵抗によって消費させられて、通信信号の波形歪を抑制することができる。 The present invention is directed to a communication network in which a plurality of nodes that transmit and receive signals are connected via a differential transmission line. In order to achieve the above object, the communication network of the present invention has three or more branch points at which the transmission line branches, and is provided at each of the three or more branch points. It has three or more resistors that connect the lines. For these three or more resistors, the combined resistance value when all the resistors are connected in parallel is set to a value approximately half the characteristic impedance of the transmission line.
With this configuration, the reflected wave generated between the nodes always passes through the resistor provided at the branch point, so that the energy of the reflected wave is consumed by the resistor and the waveform distortion of the communication signal can be suppressed.

３つ以上の抵抗は、伝送線路の分岐数に応じてそれぞれ重みが付与されており、また、分岐点に設けられる抵抗の値は、３つ以上の抵抗全ての重みの合計を分岐点の重みの値で除算した結果を、伝送線路が有する特性インピーダンスの１／２の値に乗算することで求められる。
かかる構成により、さらに、通信信号の電圧振幅の低下を回避して、Ｈｉｇｈレベルを確保することができる。 Three or more resistors are weighted according to the number of branches of the transmission line, and the resistance value provided at the branch point is the sum of the weights of all three or more resistors. Is obtained by multiplying the result of dividing by the value of ½ of the characteristic impedance of the transmission line.
With this configuration, a high level can be secured by avoiding a decrease in the voltage amplitude of the communication signal.

上記本発明によれば、各分岐点の線間に設けた抵抗による通信信号の波形歪を抑制と、全抵抗の並列合成抵抗値を伝送線路の特性インピーダンスの略１／２とすることによる通信信号の電圧振幅の確保（低下回避）とを両立させることができる。   According to the present invention, communication by suppressing the waveform distortion of the communication signal due to the resistance provided between the lines of each branch point, and by setting the parallel combined resistance value of all the resistances to approximately half the characteristic impedance of the transmission line It is possible to achieve both ensuring of signal voltage amplitude (avoidance of reduction).

本発明の一実施形態にかかる通信ネットワーク１の概略構成を示す図The figure which shows schematic structure of the communication network 1 concerning one Embodiment of this invention. 本発明の一実施形態にかかる通信ネットワーク１の具体例１を示す図The figure which shows the specific example 1 of the communication network 1 concerning one Embodiment of this invention. 図２の具体例１による波形歪の抑制効果を示す図The figure which shows the suppression effect of the waveform distortion by the specific example 1 of FIG. 本発明の一実施形態にかかる通信ネットワーク１の具体例２を示す図The figure which shows the specific example 2 of the communication network 1 concerning one Embodiment of this invention. 図４の具体例２による波形歪の抑制効果を示す図The figure which shows the suppression effect of the waveform distortion by the specific example 2 of FIG.

以下、本発明の一実施形態について、図面を参照しながら説明を行う。但し、必要以上に詳細な説明、例えば既によく知られた事項の説明や実質的に同一の構成に対する重複した説明など、を省略する場合がある。この省略は、説明が不必要に冗長になるのを避け、当業者の理解を容易にするためである。
なお、発明者は、当業者が本発明を十分に理解するために図面および以下の説明を提供するのであり、これらの図面や説明によって特許請求の範囲に記載の主題を限定することを意図するものではない。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, a more detailed description than necessary may be omitted, for example, a description of already well-known matters or a duplicate description of substantially the same configuration. This omission is for the purpose of avoiding unnecessarily redundant description and facilitating understanding by those skilled in the art.
The inventor provides drawings and the following description for those skilled in the art to fully understand the present invention, and intends to limit the subject matter described in the claims by these drawings and description. It is not a thing.

＜通信ネットワークの基本構成＞
図１は、本発明の一実施形態にかかる通信ネットワーク１の概略構成を示す図である。図１に例示した通信ネットワーク１は、例えばＣＡＮ規格に基づいて構成された車載通信ネットワークであり、信号を送受信する複数のノード１０が伝送線路２０を介して接続された構成である。複数のノード１０は、例えば電子制御ユニット（electronic control unit；ＥＣＵ）である。このＥＣＵとは、車両に関していえば、エンジンＥＣＵ、トランスミッションＥＣＵ、ブレーキＥＣＵ、メーターＥＣＵ、走行制御ＥＣＵなどである。伝送線路２０は、差動伝送線路であり、幾つかに分岐して複数のノード１０をそれぞれ接続している。この差動伝送線路の一例としては、ツイストペア線を用いた差動信号線などがある。 <Basic configuration of communication network>
FIG. 1 is a diagram showing a schematic configuration of a communication network 1 according to an embodiment of the present invention. The communication network 1 illustrated in FIG. 1 is an in-vehicle communication network configured based on the CAN standard, for example, and has a configuration in which a plurality of nodes 10 that transmit and receive signals are connected via a transmission line 20. The plurality of nodes 10 are, for example, electronic control units (ECUs). With regard to the vehicle, the ECU is an engine ECU, a transmission ECU, a brake ECU, a meter ECU, a travel control ECU, or the like. The transmission line 20 is a differential transmission line, and is branched into several to connect a plurality of nodes 10 respectively. An example of the differential transmission line is a differential signal line using a twisted pair line.

この通信ネットワーク１における通信は、例えば次のようにして行われる。
通信ネットワーク１がパワートレイン系に使用されるハイスピードＣＡＮである場合、送信ノード１０から伝送線路２０に用いた差動信号線にそれぞれＨｉｇｈレベル信号とＬｏｗレベル信号とを流し、受信ノード１０において伝送線路２０の２本線間の信号電圧差を判断することで、ノード間でデータを送受信する。 Communication in the communication network 1 is performed as follows, for example.
When the communication network 1 is a high-speed CAN used for a powertrain system, a high level signal and a low level signal are respectively sent from the transmission node 10 to the differential signal line used for the transmission line 20 and transmitted at the reception node 10. By determining the signal voltage difference between the two lines of the line 20, data is transmitted and received between the nodes.

本実施形態にかかる通信ネットワーク１は、幾つかのノード１０が１つに接続される伝送線路２０上の点、すなわち伝送線路２０が分岐して幾つかのノード１０に接続される点である分岐点３１〜３ｎを複数有しており、その分岐点３１〜３ｎごとに所定の抵抗Ｒ１〜Ｒｎが接続されている。
なお、本発明は、分岐点を複数有する通信ネットワークであれば適用可能である。しかし、従来にない本発明特有の効果を発揮させるためには、３つ以上の分岐点（ｎが３以上の整数）を有している通信ネットワークが適している。 The communication network 1 according to the present embodiment has a branch on a transmission line 20 where several nodes 10 are connected to one, that is, a branch which is a point where the transmission line 20 branches and is connected to several nodes 10. A plurality of points 31 to 3n are provided, and predetermined resistors R1 to Rn are connected to the respective branch points 31 to 3n.
The present invention is applicable to any communication network having a plurality of branch points. However, a communication network having three or more branch points (n is an integer of 3 or more) is suitable for exhibiting an unprecedented effect unique to the present invention.

図１の例では、分岐点３１には、４つのノード１０と分岐点３２が繋がっている、つまり分岐点３１から５本の伝送線路２０が分岐している。分岐点３２には、２つのノード１０と分岐点３１と分岐点３３（図示せず）が繋がっている、つまり分岐点３２から４本の伝送線路２０が分岐している。以降も同様に考えて、分岐点３ｎには、２つのノード１０と分岐点３ｎ−１（図示せず）が繋がっている、つまり分岐点３ｎから３本の伝送線路２０が分岐している。   In the example of FIG. 1, four nodes 10 and a branch point 32 are connected to the branch point 31, that is, five transmission lines 20 are branched from the branch point 31. Two nodes 10, a branch point 31, and a branch point 33 (not shown) are connected to the branch point 32, that is, four transmission lines 20 branch from the branch point 32. In the same manner, the two nodes 10 and the branch point 3n-1 (not shown) are connected to the branch point 3n, that is, three transmission lines 20 branch from the branch point 3n.

抵抗Ｒ１〜Ｒｎは、それぞれの分岐点３１〜３ｎにおいて、伝送線路２０に用いた差動信号線の２本線間（実線と太実線との間）に接続される。
例えば、図１に例示した通信ネットワーク１が上述したハイスピードＣＡＮである場合には、分岐点３１における伝送線路２０のＨｉｇｈレベル信号線（太実線、以下同じ）とＬｏｗレベル信号線（実線、以下同じ）との間に、抵抗Ｒ１が接続される。また、分岐点３２における伝送線路２０のＨｉｇｈレベル信号線とＬｏｗレベル信号線との間に、抵抗Ｒ２が接続される。以降も同様にして、分岐点３ｎにおける伝送線路２０のＨｉｇｈレベル信号線とＬｏｗレベル信号線との間に、抵抗Ｒｎが接続される。 The resistors R1 to Rn are connected between the two differential signal lines used for the transmission line 20 (between the solid line and the thick solid line) at the respective branch points 31 to 3n.
For example, when the communication network 1 illustrated in FIG. 1 is the above-described high-speed CAN, a high level signal line (thick solid line, the same below) and a low level signal line (solid line, below) of the transmission line 20 at the branch point 31. And the same) are connected to the resistor R1. In addition, a resistor R <b> 2 is connected between the high level signal line and the low level signal line of the transmission line 20 at the branch point 32. Similarly, the resistor Rn is connected between the high level signal line and the low level signal line of the transmission line 20 at the branch point 3n.

抵抗Ｒ１〜Ｒｎの各値は、それぞれが接続される分岐点３１〜３ｎにおける伝送線路２０の分岐数に応じて定められる。具体的には、抵抗Ｒ１〜Ｒｎには、全分岐数に対する接続先の分岐点３１〜３ｎにおける分岐数の比率に応じた重みが付与される。
今、伝送線路２０が有する特性インピーダンスをＺ０と、抵抗Ｒｊ（ｊ＝１〜ｎ）に付与される重みをＷｊで表すと、抵抗Ｒｊの値は次式［１］で与えられる。

Figure 2014110544
Each value of the resistors R1 to Rn is determined according to the number of branches of the transmission line 20 at the branch points 31 to 3n to which the resistors R1 to Rn are connected. Specifically, the resistors R1 to Rn are given a weight according to the ratio of the number of branches at the connection branch points 31 to 3n with respect to the total number of branches.
If the characteristic impedance of the transmission line 20 is Z 0 and the weight given to the resistor Rj (j = 1 to n) is W j , the value of the resistor Rj is given by the following equation [1].
Figure 2014110544

上記式［１］で与えられた抵抗Ｒ１〜Ｒｎは、全ての抵抗Ｒ１〜Ｒｎを並列接続したときの合成抵抗値が、伝送線路２０が有する特性インピーダンスの略１／２の値となる。
以下、通信ネットワーク１の配索が異なる２つの具体例を挙げて、抵抗Ｒ１〜Ｒｎの各値の求め方を説明する。 In the resistors R1 to Rn given by the above equation [1], the combined resistance value when all the resistors R1 to Rn are connected in parallel is approximately half the characteristic impedance of the transmission line 20.
Hereinafter, how to obtain each value of the resistances R1 to Rn will be described by giving two specific examples in which the wiring of the communication network 1 is different.

＜通信ネットワークの具体例１＞
図２は、本発明の一実施形態にかかる通信ネットワーク１の具体例１を示す図である。図２に例示する通信ネットワーク１は、１７つのノード１０が３つの分岐点３１〜３３を介して接続された通信ネットワークである。分岐点３１には、８つのノード１０と分岐点３２とが繋がっている、つまり分岐点３１から９本の伝送線路２０が分岐している。分岐点３２には、１つのノード１０と分岐点３１と分岐点３３とが繋がっている、つまり分岐点３２から３本の伝送線路２０が分岐している。分岐点３３には、８つのノード１０と分岐点３２とが繋がっている、つまり分岐点３３から９本の伝送線路２０が分岐している。 <Specific example 1 of a communication network>
FIG. 2 is a diagram showing a specific example 1 of the communication network 1 according to the embodiment of the present invention. The communication network 1 illustrated in FIG. 2 is a communication network in which 17 nodes 10 are connected via three branch points 31 to 33. Eight nodes 10 and branch points 32 are connected to the branch point 31, that is, nine transmission lines 20 branch from the branch point 31. One node 10, a branch point 31, and a branch point 33 are connected to the branch point 32, that is, three transmission lines 20 are branched from the branch point 32. The eight nodes 10 and the branch point 32 are connected to the branch point 33, that is, nine transmission lines 20 branch from the branch point 33.

具体例１では、分岐点３１〜３３に接続される抵抗Ｒ１〜３の重みをＷ１〜Ｗ３は、次式［２］に示すように分岐数の逆数で付与されるものとする。なお、伝送線路２０が有する特性インピーダンスＺ０は１２０Ωとする。

Figure 2014110544
In the first specific example, the weights W 1 to W 3 of the resistors R 1 to R 3 connected to the branch points 31 to 33 are given by the reciprocal number of the branches as shown in the following formula [2]. Note that the characteristic impedance Z 0 of the transmission line 20 is 120Ω.
Figure 2014110544

よって、分岐点３１〜３３の全分岐数に関する重みの総和は、次式［３］で表される。

Figure 2014110544
Therefore, the sum of the weights related to the total number of branches at the branch points 31 to 33 is expressed by the following equation [3].
Figure 2014110544

よって、上記式［２］および［３］を上記式［１］に当てはめると、抵抗Ｒ１〜Ｒ３の各値が次式［４］〜［６］のように求められる。

Figure 2014110544
Therefore, when the above equations [2] and [3] are applied to the above equation [1], the respective values of the resistors R1 to R3 are obtained as the following equations [4] to [6].
Figure 2014110544

上記抵抗Ｒ１〜Ｒ３は、全てを並列に接続したときの合成抵抗値［１／（１／Ｒ１＋１／Ｒ２＋１／Ｒ３）］が、伝送線路２０が有する特性インピーダンスの１／２の値（＝６０Ω）となる。よって、通信信号のＨｉｇｈ（ドミナント）の電圧振幅が低下することなく、抵抗値を増やすことができる、すなわち反射歪（波形歪）を抑制することができる。この具体例１による波形歪の抑制効果を図３に示す。   The combined resistance value [1 / (1 / R1 + 1 / R2 + 1 / R3)] when the resistors R1 to R3 are all connected in parallel is half the characteristic impedance of the transmission line 20 (= 60Ω). It becomes. Therefore, the resistance value can be increased without decreasing the voltage amplitude of High (dominant) of the communication signal, that is, reflection distortion (waveform distortion) can be suppressed. FIG. 3 shows the effect of suppressing waveform distortion according to the specific example 1.

例えば、通信ネットワークに用いられる従来の技術では、分岐点３１および分岐点３３の２箇所だけに終端抵抗１２０Ωを接続する。このため、従来の手法では、通信信号のＨｉｇｈ（ドミナント）からＬｏｗ（リセッシブ）への移行時に非常に大きな反射歪が発生し、通信信号がＬｏｗ（リセッシブ）の閾値（０．７Ｖ）以下に収束するまでに１１００ｎｓ以上時間がかかった。
これに対し、本発明の通信ネットワーク構成では、反射歪の発生を大幅に抑制できるので、通信信号がＬｏｗ（リセッシブ）の閾値（０．７Ｖ）以下に収束するまでの時間を４８０ｎｓ程度に短縮することができる。従って、通信信号におけるビット誤判定までの余裕度が向上するため、配索規模（ノード数、配線長、分岐数など）の拡張や通信速度の向上が可能となる。 For example, in the conventional technique used in a communication network, a termination resistor 120Ω is connected to only two points of the branch point 31 and the branch point 33. For this reason, in the conventional method, a very large reflection distortion occurs when the communication signal shifts from High (dominant) to Low (recessive), and the communication signal converges below the threshold (0.7 V) of the low (recessive). It took more than 1100ns to complete.
On the other hand, in the communication network configuration of the present invention, since the occurrence of reflection distortion can be significantly suppressed, the time until the communication signal converges below the Low (recessive) threshold (0.7 V) is shortened to about 480 ns. be able to. Accordingly, since the margin to erroneous bit determination in the communication signal is improved, the routing scale (number of nodes, wiring length, number of branches, etc.) can be expanded and the communication speed can be improved.

＜通信ネットワークの具体例２＞
図４は、本発明の一実施形態にかかる通信ネットワーク１の具体例２を示す図である。図４に例示する通信ネットワーク１は、１６つのノード１０が３つの分岐点３１〜３３を介して接続された通信ネットワークである。分岐点３１には、７つのノード１０と分岐点３２とが繋がっている、つまり分岐点３１から８本の伝送線路２０が分岐している。分岐点３２には、２つのノード１０と分岐点３１と分岐点３３とが繋がっている、つまり分岐点３２から４本の伝送線路２０が分岐している。分岐点３３には、７つのノード１０と分岐点３２とが繋がっている、つまり分岐点３３から８本の伝送線路２０が分岐している。 <Specific example 2 of communication network>
FIG. 4 is a diagram showing a specific example 2 of the communication network 1 according to the embodiment of the present invention. The communication network 1 illustrated in FIG. 4 is a communication network in which 16 nodes 10 are connected via three branch points 31 to 33. Seven nodes 10 and a branch point 32 are connected to the branch point 31, that is, eight transmission lines 20 are branched from the branch point 31. Two nodes 10, a branch point 31, and a branch point 33 are connected to the branch point 32, that is, four transmission lines 20 branch from the branch point 32. Seven nodes 10 and a branch point 32 are connected to the branch point 33, that is, eight transmission lines 20 branch from the branch point 33.

具体例２では、分岐点３１〜３３に接続される抵抗Ｒ１〜３の重みをＷ１〜Ｗ３は、次式［７］に示すように分岐数そのままで付与されるものとする。なお、伝送線路２０が有する特性インピーダンスＺ０は１２０Ωとする。

Figure 2014110544
In the second specific example, the weights W 1 to W 3 of the resistors R 1 to R 3 connected to the branch points 31 to 33 are given as the number of branches as shown in the following formula [7]. Note that the characteristic impedance Z 0 of the transmission line 20 is 120Ω.
Figure 2014110544

よって、分岐点３１〜３３の全分岐数に関する重みの総和は、次式［８］で表される。

Figure 2014110544
Therefore, the sum of the weights related to the total number of branches at the branch points 31 to 33 is expressed by the following equation [8].
Figure 2014110544

よって、上記式［７］および［８］を上記式［１］に当てはめると、抵抗Ｒ１〜Ｒ３の各値が次式［９］〜［１１］のように求められる。

Figure 2014110544
Therefore, when the above equations [7] and [8] are applied to the above equation [1], the respective values of the resistors R1 to R3 are obtained as the following equations [9] to [11].
Figure 2014110544

上記抵抗Ｒ１〜Ｒ３は、全てを並列に接続したときの合成抵抗値［１／（１／Ｒ１＋１／Ｒ２＋１／Ｒ３）］が、伝送線路２０が有する特性インピーダンスの１／２の値（＝６０Ω）となる。よって、通信信号のＨｉｇｈ（ドミナント）の電圧振幅が低下することなく、抵抗値を増やすことができる、すなわち反射歪（波形歪）を抑制することができる。この具体例２による波形歪の抑制効果を図５に示す。   The combined resistance value [1 / (1 / R1 + 1 / R2 + 1 / R3)] when the resistors R1 to R3 are all connected in parallel is half the characteristic impedance of the transmission line 20 (= 60Ω). It becomes. Therefore, the resistance value can be increased without decreasing the voltage amplitude of High (dominant) of the communication signal, that is, reflection distortion (waveform distortion) can be suppressed. FIG. 5 shows the effect of suppressing waveform distortion according to the second specific example.

以上のように、本発明の一実施形態にかかる通信ネットワークによれば、全てを並列に接続したときの合成抵抗値が伝送線路の特性インピーダンスの略１／２の値となる抵抗を、伝送線路上の各分岐点の線間にそれぞれ設ける。各分岐点の線間に設ける抵抗の値は、その分岐点における伝送線路の分岐数の比率に応じて決定される。
これにより、ノード間で生じる反射波が分岐点に設けられた抵抗を必ず通過するため、反射波のエネルギーが抵抗によって消費させられて、通信信号の波形歪を抑制することができる。従って、各分岐点の線間に設けた抵抗による通信信号の波形歪を抑制と、全抵抗の並列合成抵抗値を伝送線路の特性インピーダンスの略１／２とすることによる通信信号の電圧振幅の確保（低下回避）とを両立させることができる。 As described above, according to the communication network according to the embodiment of the present invention, a resistance whose combined resistance value when all of them are connected in parallel is approximately a half of the characteristic impedance of the transmission line is Provided between the lines of the upper branch points. The value of the resistance provided between the lines of each branch point is determined according to the ratio of the number of branches of the transmission line at the branch point.
Thereby, since the reflected wave generated between the nodes necessarily passes through the resistor provided at the branch point, the energy of the reflected wave is consumed by the resistor, and the waveform distortion of the communication signal can be suppressed. Therefore, the waveform distortion of the communication signal due to the resistance provided between the lines of each branch point is suppressed, and the voltage amplitude of the communication signal is reduced by setting the parallel combined resistance value of all the resistances to approximately half the characteristic impedance of the transmission line. It is possible to achieve both ensuring (avoidance of reduction).

なお、本発明が提供する技術の一実施例として図面を用いた詳細な説明を行ったが、この図面および詳細な説明に記載された構成要素の中には、課題解決のために必須な構成要素だけでなく、本技術を例示するために課題解決のためには必須でない構成要素も含まれ得る。よって、図面や詳細な説明に記載されているからといって、全ての構成要素が発明に必須の構成要素であるわけではない。
さらに、上述した実施形態は、本発明における技術を例示するためのものであるから、特許請求の範囲またはその均等の範囲において、種々の変更、置き換え、付加、省略などを行うことができる。 In addition, although detailed description using drawing was performed as one Example of the technique which this invention provides, in the component described in this drawing and detailed description, it is essential structure for solution of a problem. Not only elements but also components that are not essential for solving the problem in order to illustrate the present technology may be included. Therefore, just because they are described in the drawings and detailed description, not all the constituent elements are essential elements for the invention.
Furthermore, since the above-described embodiment is for exemplifying the technique in the present invention, various modifications, replacements, additions, omissions, and the like can be made within the scope of the claims or an equivalent scope thereof.

本発明は、多数のノードが有線接続された通信ネットワークに利用可能であり、特に伝送線路で生じる反射波に起因する波形歪を抑制したい場合などに有用である。   The present invention can be used in a communication network in which a large number of nodes are connected by wire, and is particularly useful when it is desired to suppress waveform distortion caused by reflected waves generated in a transmission line.

１ 通信ネットワーク
１０ ノード
２０ 伝送線路
３１、３２、３３、３ｎ 分岐点
Ｒ１、Ｒ２、Ｒ３、Ｒｎ 抵抗 1 Communication network 10 Node 20 Transmission lines 31, 32, 33, 3n Branch points R1, R2, R3, Rn Resistance

Claims (3)

信号を送受信する複数のノードが差動伝送線路を介して接続される通信ネットワークであって、
前記伝送線路が分岐する分岐点を３つ以上有し、
前記３つ以上の分岐点のそれぞれに設けられ、当該各分岐点の差動線間を接続する３つ以上の抵抗を備えており、
前記３つ以上の抵抗は、全ての抵抗を並列接続したときの合成抵抗値が、前記伝送線路が有する特性インピーダンスの略１／２の値に設定されていることを特徴とする、通信ネットワーク。 A communication network in which a plurality of nodes that transmit and receive signals are connected via a differential transmission line,
Having three or more branch points where the transmission line branches;
Provided at each of the three or more branch points, and provided with three or more resistors for connecting the differential lines of the branch points;
The communication network, wherein the three or more resistors are set such that a combined resistance value when all the resistors are connected in parallel is approximately a half of a characteristic impedance of the transmission line. 前記３つ以上の抵抗は、前記伝送線路の分岐数に応じてそれぞれ重みが付与されていることを特徴とする、請求項１に記載の通信ネットワーク。   2. The communication network according to claim 1, wherein the three or more resistors are each given a weight according to the number of branches of the transmission line. 前記分岐点に設けられる前記抵抗の値は、前記３つ以上の抵抗全ての重みの合計を当該分岐点の重みの値で除算した結果を、前記伝送線路が有する特性インピーダンスの１／２の値に乗算することで求められることを特徴とする、請求項２に記載の通信ネットワーク。   The value of the resistor provided at the branch point is a value obtained by dividing the sum of the weights of all the three or more resistors by the weight value of the branch point, and is a value of ½ of the characteristic impedance of the transmission line. The communication network according to claim 2, wherein the communication network is obtained by multiplying.
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JP2007201697A (en) * 2006-01-25 2007-08-09 Auto Network Gijutsu Kenkyusho:Kk Branching connector
JP2009505470A (en) * 2005-08-10 2009-02-05 エヌエックスピー ビー ヴィ Method for determining cable termination resistance value of communication network and corresponding communication network
JP2012004802A (en) * 2010-06-16 2012-01-05 Nippon Soken Inc Waveform distortion reduction method and cable communication system
JP2012235336A (en) * 2011-05-02 2012-11-29 Auto Network Gijutsu Kenkyusho:Kk Communication system

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5043857A (en) * 1973-08-21 1975-04-19
JPH08288891A (en) * 1995-04-10 1996-11-01 Oki Electric Ind Co Ltd Transmission/reception line network for high-speed signal
JP2009505470A (en) * 2005-08-10 2009-02-05 エヌエックスピー ビー ヴィ Method for determining cable termination resistance value of communication network and corresponding communication network
JP2007201697A (en) * 2006-01-25 2007-08-09 Auto Network Gijutsu Kenkyusho:Kk Branching connector
JP2012004802A (en) * 2010-06-16 2012-01-05 Nippon Soken Inc Waveform distortion reduction method and cable communication system
JP2012235336A (en) * 2011-05-02 2012-11-29 Auto Network Gijutsu Kenkyusho:Kk Communication system

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