JP2004356780A

JP2004356780A - Transmission signal equalizing system, method thereof, and method of determining optimum equalization amount of transmission path

Info

Publication number: JP2004356780A
Application number: JP2003150054A
Authority: JP
Inventors: Seigo Takahashi; 成五高橋
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2003-05-28
Filing date: 2003-05-28
Publication date: 2004-12-16

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the equalizing system of a transmission signal which is capable of contributing to reduction of a manufacturing cost or a device cost by enabling conventionally required reduction of the number of processes of manpower or an adjusting time. <P>SOLUTION: A transmission signal equalizing system applies equalization to a transmission signal to compensate transmission characteristics of a transmission path 3 in transmitting a signal from a transmission circuit 1 to a reception circuit 2 via the transmission path 3. In this system, the reception circuit 2 detects a present amount of equalization on the basis of the reception signal having passed through the transmission path 3, generates an equalization error signal being a difference between the previously set optimum equalization amount for the transmission path 3 and the present equalization amount, and transmits the generated signal to the transmission circuit 1. The transmission circuit 1 controls the equalization amount of an equalizing transmission circuit 11 on the basis of the equalization error signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は伝送信号等化システムとその方法及び伝送路の最適等化量決定方法に関し、特にＩＰ（ＩｎｔｅｒｎｅｔＰｒｏｔｏｃｏｌ）ルータやクロスコネクト等の大容量通信装置、スーパーコンピュータ等の大規模な情報処理装置を構成する複数のプリント基板間の高速インタコネクション方式において、伝送路導体の表皮効果、絶縁材料の誘電損失等による伝送信号の高周波成分の減衰を補償するようにした等化方式に関するものである。
【０００２】
【従来の技術】
一例として、図１６に、大容量通信装置の異なるプリント基板（ＰＫＧと称する）１０と２０との間を、バックワイヤボード（ＢＷＢと称す）３０上に形成されたプリントパタンの伝送路３を経由して、電気信号の送受を行う場合における構成を示す。伝達される電気信号は、送信回路１から受信回路２に伝達されるが、この場合の伝送路３は、ＰＫＧ１０及び２０とＢＷＢ３０の上に形成されたパタン配線と、ＰＫＧ１０とＢＷＢ３０の特定のパタン配線同士を電気的に接続するコネクタ３１とからなる。
【０００３】
ＰＫＧ１０上の送信回路１からＰＫＧ２０上の受信回路２までの一続きの伝送路３は、ＢＷＢ３０の場合、数１０ｃｍから２ｍ以下、ＢＷＢの代替としてケーブル伝送路を用いる場合、１ｍから１００ｍ程度である。以下は、代表してＢＷＢ伝送の場合について述べる。
【０００４】
このパタン配線を含む伝送路３を伝達される電気信号のビットレートが１Ｇｂｐｓを越える領域では、伝送路３を形成する導電体の直流的な電気抵抗の他に、導体の表皮効果による伝導損失の増大と、ＰＫＧ１０と２０及びＢＷＢ３０を構成する絶縁体の誘電損失の増大と、コネクタ３１などのインピーダンス不連続点における電気信号の反射とによって、信号波形の劣化が生じて受信側で符号識別誤りが発生する。
【０００５】
この問題に対して、従来は、非特許文献１や２に開示されている様な、プリエンファシスと呼ばれる送信等化方式が適用される。この送信等化方式では、個々の送信回路に対して、異なる等化強度の設定が必要である。その理由は以下の如くである。すなわち、パタン配線３の伝送路長は一定ではなく、個々のパタン配線３における伝達特性が、各々異なった値を取るためであり、また、ある特定のパタン配線距離に対しては、最適な等化強度が唯一存在し、等化によ補正が最適値よりも大き過ぎる場合には、受信信号のアイパタンの開口幅は狭まり、逆効果となるためである。
【０００６】
図１７に、上述の従来技術による、等化強度設定回路の構成例を示す。従来の技術では、送信回路１と受信回路２との間を接続する伝送路３の伝達特性を補償する等化強度を、等化量生成制御回路１２により、等化送信回路１１に対して設定する必要がある。なお、図１７において、受信回路２における２１は受信増幅器（アンプ）であり、２２は受信符号を識別するための識別回路である。
【０００７】
【非特許文献１】
Ａ．Ｆｉｅｄｌｅｒｅｔａｌ．，”Ａ１．０６２５ＧｂｐｓＴｒａｎｓｃｅｉｖｅｒｗｉｔｈ２ｘＯｖｅｒｓａｍｐｌｉｎｇａｎｄＴｒａｎｓｍｉｔＳｉｇｎａｌＰｒｅ−Ｅｍｐｈａｓｉｓ， ”Ｐｒｏｃ．ＩＥＥＥＩｎｔ．ｌＳｏｌｉｄｓ−ＳｔａｔｅＣｉｒｃｕｉｔｓＣｏｎｆ．，ＤｉｇｅｓｔｏｆＴｅｃｈｎｉｃａｌＰａｐｅｒｓ，ＩＥＥＥＰｒｅｓｓ，Ｐｉｓｃａｔａｗａｙ，Ｎ．Ｊ．，１９９７，ｐｐ．２３８−２３９．
【０００８】
【非特許文献２】
Ｍ．Ｆｕｋａｉｓｈｉ，Ｋ．Ｎａｋａｍｕｒａ，Ｍ．Ｙｏｔｓｕｙａｎａｇｉ，ｅｔ．ａｌ．， ”Ａ２０−Ｇｂ／ｓＣＭＯＳＭｕｌｔｉ−ＣｈａｎｎｅｌＴｒａｎｓｍｉｔｔｅｒａｎｄＲｅｃｅｉｖｅｒＣｈｉｐＳｅｔｆｏｒＵｌｔｒａ−ＨｉｇｈＲｅｓｏｌｕｔｉｏｎＤｉｇｉｔａｌＤｉｓｐｌａｙ”，２０００ＩＳＳＣＣＤｉｇｅｓｔｏｆｔｅｃｈｎｉｃａｌＰａｐｅｒｓ，ＳａｎＦｒａｎｃｉｓｃｏ，ｐｐ．２６０−２６１，Ｆｅｂ，２０００．
【０００９】
【発明が解決しようとする課題】
上記従来技術では、送信回路１１における等化量生成制御回路１２により設定される等化強度の最適値の自動検出が出来ずに、手動あるいはプログラムを介して、明示的に設定を行う必要があることと、その設定した等化強度が最適であることが保証されないことが課題となっている。
【００１０】
前者に関しては、装置を構成するＰＫＧ１０と２０のＢＷＢ３０上の配置は、装置組み立て時に初めて決定される。ここで、ＰＫＧ１０は、ＢＷＢ３０上の複数のスロットに接続可能であり、機能的には共用化が可能なものとする。例えば、ＰＫＧ１０とＰＫＧ２０を、ＢＷＢ３０上で空間的に隣接して配置する場合から、ＢＷＢ３０の空間的に両端に配置する場合まで、複数の組み合わせがあり得る。このとき、伝送路３の配線長は、最短の数ｃｍから、最長の概ねＢＷＢ３０の寸法と同等の配線長を取るために、相応の信号伝達特性の変化が現れることになる。
【００１１】
ＰＫＧ１０及び２０の製造時には、それらが接続される伝送路３の信号伝達特性を知り得ないために、多数の異なる等化強度を持つＰＫＧ品種を製造するか、あるいは、共通のＰＫＧを製造して、装置組み立て後に等化強度の設定を行う必要がある。同等機能のＰＫＧにも関わらず、異なる品種として製造、管理することは、即座にコスト上昇に繋がる。また、後工程として、等化強度の設定を行うと、設定に要する人的な費用の発生と、調整に要する時間だけの在庫の滞留が発生し、装置価格の上昇を引き起こす。
【００１２】
後者の設定した等化強度の信頼性に関しては、伝送路３の信号伝達特性の個体差を吸収することが困難なことと、経時変化に対応出来ないことが問題となる。装置組み立て時に設定する等化強度の最適値を、各々のＢＷＢ３０を含む伝送路３と、関連する全ての回路の製造誤差に起因した個々の伝達特性に対して最適化するには、各々の個体に対して実測を必要とするために、多大な検査工数を要する。逆に、製造誤差を小さくすると、製造歩留まりの悪化に結びつく。
【００１３】
ＢＷＢなどの伝送路３及び送受信回路１及び２は温度特性を持つために、運用中の環境温度変化によって、信号伝達特性や、送受信特性の変動が起こり得る。しかし、従来の方式における等化強度の設定では、伝達特性の設計値と実際の値との差を等化強度として、送信回路１の等化量生成制御回路１２へ帰還する手段が無いために、実際の伝送路の伝達特性に対して誤差のある等化強度を設定し、装置運用を行う可能性がある。これは、受信回路２における受信マージンを減少させ、符号識別誤り発生の確率を上昇させる危険がある。
【００１４】
本発明の目的は、従来必要とされていた人的な工数の削減や、調整時間の削減を可能として、製造コストや装置コストの低減に寄与する伝送信号等化システムとその方法及び伝送路の最適等化量決定方法を提供することである。
【００１５】
【課題を解決するための手段】
本発明による伝送信号等化システムは、送信部から伝送路を介して受信部へ信号を伝送するに際して、前記伝送路の伝達特性の補償のために伝送信号に対して等化を施すようにした伝送信号等化システムであって、前記受信部において、前記伝送路を経た受信信号を基に現在の等化量を検出し、予め設定されている、前記伝送路に対する最適等化量と現在の等化量との差である等化誤差信号を生成して前記送信部へ送信する等化誤差信号生成手段を設け、前記送信部において、前記伝送信号の等化をなす等化手段と、前記等化誤差信号生成手段からの前記等化誤差信号に基づき前記等化手段の等化量の制御をなす等化量制御手段とを設けたことを特徴とする。
【００１６】
本発明による伝送信号等化方法は、送信部から伝送路を介して受信部へ信号を伝送するに際して、前記伝送路の伝達特性の補償のために伝送信号に対して等化を施すようにした伝送信号等化方法であって、前記受信部において、前記伝送路を経た受信信号を基に現在の等化量を検出する等化量検出ステップと、予め設定されている、前記伝送路に対する最適等化量と現在の等化量との差である等化誤差信号を生成する等化誤差信号生成ステップと、この等化誤差信号を、前記送信部へ送信するステップとを含み、前記送信部において、前記等化誤差信号に基づき等化手段の等化量の制御をなす等化量制御ステップと、前記等化量制御ステップにて制御された等化量に基づき、前記等化手段により前記伝送信号の等化をなすステップとを含むことを特徴とする。
【００１７】
本発明による最適等化量検出方法は、送信部から伝送路を介して受信部へ信号を伝送するに際して、前記伝送路の伝達特性の補償のために伝送信号に対して等化を施すようにした伝送信号等化システムにおける最適等化量検出方法であって、前記送信部において、前記伝送信号の周波数帯域の第一の周波数成分を有する第一の固定パタン信号と、前記周波数とは異なる第二の周波数成分を有する第二の固定パタン信号とをそれぞれ送信するステップと、前記受信部において、前記第一の固定パタン及び第二の固定パタンの受信強度をそれぞれ測定してこれら測定結果に基づき送信等化強度を検出するステップと、前記送信部において、前記送信等化強度と逆になるような等化量を設定して擬似ランダムパタン信号を伝送するステップと、前記受信部において、前記擬似ランダムパタン信号の前記第一及び第二の周波数成分の受信強度をそれぞれ測定してこれら測定結果に基づき前記最適等化量を決定するステップとを含むことを特徴とする。
【００１８】
本発明による他の最適等化量検出方法は、送信部から伝送路を介して受信部へ信号を伝送するに際して、前記伝送路の伝達特性の補償のために伝送信号に対して等化を施すようにした伝送信号等化システムにおける最適等化量検出方法であって前記送信部において、擬似ランダムパタン信号を送信しつつ等化強度を最小値と最大値の範囲で掃引するステップと、前記受信部において、前記等化強度の掃引中における各受信符号誤り率と、前記擬似ランダムパタン信号の第一の周波数成分の受信強度及び前記周波数とは異なる第二の周波数成分の受信強度とをそれぞれ測定するステップと、これら測定結果に基づき等化強度と受信符号誤り率との特性を採取するステップと、この特性に基づき最小の受信符号誤り率をとる等化強度に対応する第一及び第二の受周波数成分の受信強度の比を求めて前記最適等化量とするステップとを含むことを特徴とする。
【００１９】
本発明の作用を述べる。送信部から伝送路を介して受信部へ信号を伝送するに際して、伝送路の伝達特性の補償のために伝送信号に対して等化を施すようにした伝送信号等化システムにおいて、受信部において、伝送路を経た受信信号を基に現在の等化量を検出し、予め設定されている、伝送路に対する最適等化量と現在の等化量との差である等化誤差信号を生成して送信部へ送信し、送信部において、等化誤差信号に基づき等化回路の等化量の制御をなすものである。
【００２０】
【発明の実施の形態】
以下に図面を参照しつつ本発明の実施例について詳細に説明する。図１は本発明の一実施例を示す機能ブロック図であり、図１６，１７と同等部分は同一符号により示している。図１を参照すると、伝送路３を介して送信回路１と受信回路２とが接続されている。送信回路１は、送信等化機能を持つ等化送信回路１１と、この送信回路１１の等化量を生成する等化量生成制御回路１２と、受信回路２からの等化誤差信号を受信して等化量生成制御回路１２の等化量の制御をなす等化誤差信号受信回路１３と、本発明による自動等化のための等化基準値を生成するために使用される予め定められたパタンを発生するパタン発生回路１４と、このパタン発生回路１４の出力と送信信号とを選択するセレクタ１５と、これら各部を制御する制御部１６とを有している。
【００２１】
受信回路２は、増幅器（アンプ）２１と、このアンプ出力の符号識別をなす識別回路２２と、この識別回路２２の出力の符号誤り率を検出する符号誤り率検出回路２３と、アンプ２１の出力から等化誤差を検出する等化誤差検出回路２４と、この検出された等化誤差を送信回路１へフィードバックして送信する等化誤差信号送信回路２５と、等化誤差検出回路２４等を制御する制御部２６とを有している。
【００２２】
送信回路１１へ入力される送信信号は等化送信回路１１において送信等化処理をされて伝送路３へ送出される。この時の送信等化強度（等化量）は、等化量制御回路１２より与えられる。伝送路３を通して伝達された送信信号は、受信回路２のアンプ２１にて増幅され、識別回路２２と、等化誤差検出回路２４へ入力される。識別回路２２は入力された信号の符号識別を行って再生信号として外部へ出力する。
【００２３】
等化誤差検出回路２４は、アンプ２１の出力である受信信号のアイ開口を観測することにより、現在の等化状態と、等化送信回路１１による伝送路３の伝達特性の等化が最適に行われている状態との誤差を検出する。この誤差の量を、等化誤差信号送信回路２５において、電圧値あるいは電流値など正負両極性の意味を持つアナログ値で規定される誤差信号として、送信回路１の等化誤差信号受信回路１３へ伝達する。
【００２４】
運用時に変化する等化誤差は、環境温度変化や経時劣化のような十分にゆっくりとした変化であり、速い変動要因はない。このために、等化誤差信号送信回路２５には、十分に長い時定数を持った低域通過フィルタを備え、短時間の変動成分を除去して、送信回路１へ送信すべき誤差信号に対して十分な平滑化を施す機能を有している。等化誤差信号受信回路１３は受信回路２にて生成された誤差信号を受信して、現在設定されている等化量を補正するよう等化量の制御を行う。
【００２５】
図２に、等化強度（等化量）と等化誤差との関係及びその時の伝送路３の両端の送受信信号の模式図を例示する。図２のグラフの横軸は等化強度を示し、縦軸はその時の誤差信号の大きさを示す。伝送路の伝達特性により、等化強度には最適点が存在する。等化が最適な場合には、誤差信号は零となり、受信信号波形のアイ開口は最大となる。等化強度が小さいときは、伝送路伝達後の波形は、高周波成分が減少して、受信信号のアイ開口幅が小さくなる。逆に等化強度が過大な場合には、受信信号のアイ開口部の振幅が全幅よりも小さくなるため、受信条件は最適ではない。
【００２６】
図３に、等化誤差検出回路２４の具体的構成を示す。等化誤差検出回路２４は、透過中心周波数の異なる２つの狭帯域な帯域透過フィルタ（ＢＰＦ）２４１、２４２と、強度変換器（ＰＤＥＦ）２４３、２４４と、割り算演算器２４６と、基準メモリ（ＭＥＭ）２４５と、引き算器２４７とからなる。
【００２７】
受信回路２のアンプ２１で増幅された受信信号は、２つの帯域透過フィルタ２４１と２４２に入力される。帯域透過フィルタ２４１の透過中心周波数ｆ０は、例えば、伝送信号のビットレートの半分の周波数である。もう一方の帯域透過フィルタ２４２の透過中心周波数ｆ１は、帯域透過フィルタ２４１のそれよりも低い周波数に設定されている。
【００２８】
図４は信号スペクトルの模式図を示すものである。理想的なアイ開口を持つ信号スペクトルにおいては、ｆ０とｆ１の強度は、各々矢印の大きさに対応しており、この時のアイ開口は最大となる。それに対して、高周波成分の減衰の激しい、例えば図５のような伝達特性を持ったプリント基板などの伝送路を介して伝達された信号のスペクトルでは、図６に示すように、ｆ０とｆ１の強度比が、理想値と大きく異なる。
【００２９】
簡単な例として、伝送信号のビットレートが２Ｇｂｐｓの場合について、図７を用いて説明する。２Ｇｂｐｓの信号に於いて、“０１０１０１……”の繰り返しビットパタンは、図７の上側に示す様に、１ＧＨｚの正弦波と同等と見なすことが可能である。つまり、アイパタンを十分に開かせるための伝送路の遮断周波数は、最大でも１ＧＨｚで十分である。これにより、帯域透過フィルタ２４１の透過中心周波数を、１ＧＨｚとする。
【００３０】
それに対して、伝送路の伝達特性により、波形劣化を引き起こした場合、例えば、１ビットの孤立パルスの振幅が、図７の下側に示す様に、４ビット後に正規の振幅を得るような場合には、帯域透過フィルタ２４２の中心周波数ｆ１は、ｆ０／４とするのが望ましい。
【００３１】
帯域透過フィルタ２４１と帯域透過フィルタ２４２の出力は、それぞれ、強度検出器２４３、２４４により、ｆ０とｆ１のスペクトル強度、Ｐ（ｆ０）及びＰ（ｆ１）に変換され、続いて、割り算器２４６により、得られた２つのスペクトル強度比Ｐ（ｆ０）／Ｐ（ｆ１）が求められる。等化誤差信号は、引き算器２４７を用いて、上述の測定により得られたスペクトル強度比と、基準メモリ２４５に保存された、最良の受信波形のスペクトル強度比を示す基準値との差より生成されることになる。
【００３２】
基準メモリ２４５に保存する等化基準値の決定手法について説明する。この等化基準値はトレーニングパタンを用いて生成することになる。前述の例を用いて説明することにする。ｆ０とｆ１の２つのスペクトル成分の強度を求めるために、２つの固定パタンを用いる。１つは、“０”と“１”とを１ビットづつ交互に変化させる“０１０１０１０１……”のパタンであり、ｆ０の強度を得るために用いるパタンである。他方は、例えば、各々４ビットづつ連続した“０”と“１”とを交互に変化させる“００００１１１１……”のパタンであり、ｆ１の強度を得るために用いるパタンである。
【００３３】
ここで、ｆ１＝ｆ０／４であるが、後者の信号パタンは２×ｆ０の周波数成分までを持つ矩形波である。しかし、後者の信号パタンをフーリエ級数展開した時の基本波の係数は１であることから、長周期の矩形波を用いてｆ１のスペクトル強度を求めることは可能である。
【００３４】
図８を参照すると、等化基準値を得るためのトレーニング手順の一例を示すフローチャートである。送受信系の初期化ルーチンにおいて、等化送信回路１１の等化強度を零に設定し（ステップＳ１）、トレーニングパタンとして、パタン発生回路１４により、上述した２つの固定パタンを送信し（ステップＳ２，Ｓ４）、受信した信号のそれぞれのスペクトル強度Ｐ（ｆ０）０とＰ（ｆ１）０とを測定する（ステップＳ３，Ｓ５）。ここで得られた２点のスペクトル強度は、図９に示すように、実際の伝達特性を直線近似したものである。この結果から、送信等化強度は、近似的にＰ（ｆ１）０／Ｐ（ｆ０）０と求められる（ステップＳ６）。
【００３５】
次に、送信回路１のパタン発生回路１４により、疑似ランランダムパタンを生成し、これを送信回路１より伝送路３へ送信する。この時、送信回路１の等化送信回路１１における送信等化強度は、上記のトレーニングパタンで求められた伝達特性の逆特性に相当する等化を施す。具体的には、ｆ０の帯域のスペクトル強度が、ｆ１のそれと比較して、Ｐ（ｆ１）０／Ｐ（ｆ０）０倍となるような等化を施す（ステップＳ７）。
【００３６】
かかる等化が施された疑似ランダムパタンを伝送して（ステップＳ８）、受信回路２の等化誤差検出回路２４において、Ｐ（ｆ０）１とＰ（ｆ１）１とを測定し（ステップＳ９）、その強度比Ｐ（ｆ０）１／Ｐ（ｆ１）１を最良の受信波形のスペクトル強度比として（ステップＳ１０）、基準メモリ２４５に格納する（ステップＳ１１）。
【００３７】
次に、図１０を参照すると、ある特定の伝送路に対する等化強度の最適値は、等化強度の最小から最大の間の、ある特定の１点に規定され、その時のアイ開口が最大となる。そして、その最適値から等化強度の誤差が大きくなれば、等化強度が過大でも過小でも受信信号のアイ開口は狭くなり、ビットエラーレートが増大する。この特性を用いて、最適な等化強度を求める手順を以下に説明する。
【００３８】
図１１は、この場合の等化基準値を得るためのトレーニング手順の例を示すフローチャートである。送信回路１において、パタン発生回路１４により疑似ランダムパタン信号を送信しつつ、単位時間毎にステップ的に等化送信回路１１の等化強度を最小から最大まで掃引する（ステップＳ２１）。その時、受信回路２では、この単位時間と同じ周期で、受信信号の符号誤り率を計数し、図１０のグラフに相当する符号誤り率特性と、同時に前記スペクトル強度Ｐ（ｆ０）とＰ（ｆ１）を採取する（ステップＳ２２）。
【００３９】
採取した符号誤り率特性において、最小の符号誤り率を取る等化強度が最適な等化強度である（ステップＳ２３）。その時のＰ（ｆ０）／Ｐ（ｆ１）を、最良の受信波形のスペクトル強度比として（ステップＳ２４）、基準メモリ２４５に格納する（ステップＳ２５）。
【００４０】
または、採取した符号誤り率特性において、ある適当な符号誤り率を取る等化強度は、最適な等化強度から過大な方向と過小な方向の２点を見いだすことが出来る。その２点の等化強度の平均値を、最適な等化強度とし、その時のＰ（ｆ０）／Ｐ（ｆ１）を、最良の受信波形のスペクトル強度比として、基準メモリ２４５に格納しても良い。
【００４１】
以上の図８及び図１１に示した処理フローは、送信回路１の制御部１６と受信回路２の制御部２６との連携により行われるものである。
【００４２】
次に、等化誤差検出回路から得られた等化誤差信号を、受信回路２から送信回路１へ伝達する方法について説明する。伝達する高速信号の配線とは別に、誤差信号専用の配線を用いて誤差信号を送信回路１へ伝達しても良い。しかし、別配線を用いることは、別配線を設計する必要があり、同時に、ＢＷＢとＰＫＧの接続端子を必要とするため、端子数の増加に繋がる。
【００４３】
そこで、本発明では、誤差信号の変化が、伝達される高速信号（送信信号）の変化と比較して十分に遅いことに着目し、誤差信号と高速信号とを、簡便に重畳と分離とが可能な回路を用いて、高速信号と同一の配線パタンを用いて、当該誤差信号を送信回路１へ伝達する方法を用いる。
【００４４】
図１２は、等化誤差信号を受信回路２から送信回路１へ伝達する場合の一例を説明するブロック図であり、複雑化を避けるために、誤差信号の伝達に関係する部分についてのみ示しており、他は省略している。なお、図１２において、図１と同等部分は同一符号により示している。
【００４５】
図１２において、等化誤差信号の伝達回路は、高速信号（送信信号）のための等化送信回路１１と、受信増幅器であるアンプ２１と、等化誤差信号の送信のための等化誤差信号送信回路２５と、等化誤差信号受信回路１３と、伝送路３と、高域透過フィルタ（ＨＰＦ）４１，４１´と、低域透過フィルタ（ＬＰＦ）４２，４２´とにより構成される。
【００４６】
低域透過フィルタ４２，４２´の遮断周波数は、高速信号（送信信号）の信号帯域よりも十分に低い周波数を用いる。例えば、高速信号のビットレートの１／１００００か、それ以下の周波数に設定することが現実的である。
【００４７】
図１２に示す構成では、等化送信回路１１から受信側のアンプ２１へ伝達される高速信号（送信信号）は、高域透過フィルタ４１，４１´は通過するが、低域通過フィルタ４２，４２´では遮断されるために、等化誤差信号の等化誤差信号送信回路２５及び等化誤差信号受信回路１３への分岐による信号の減衰や劣化は無い。反対に、等化誤差信号は、高速信号の帯域と比較すると、ほとんど直流的な振る舞いとなり、高域通過フィルタ４１，４１´により、等化送信回路１１や受信側のアンプ２１への等化誤差信号の流入はなく、高速信号（送信信号）と等化誤差信号とは互いに干渉することなく、同一の伝送路３上を独立な信号として伝達することが可能となる。
【００４８】
図１３は等化誤差信号を受信回路２から送信回路１へ伝達する場合の他の例を説明するブロック図であり、複雑化を避けるために、誤差信号の伝達に関係する部分についてのみ示しており、他は省略している。なお、図１３において、図１と同等部分は同一符号により示している。
【００４９】
本回路構成では、図１２における高域透過フィルタ４１，４１´と低域透過フィルタ４２，４２´との代替として、バイアスＴ回路４３，４３´を用いており、図１２に説明した構成と同等の効果を得ることができる。バイアスＴ回路は、周知の様に、低周波成分（ＤＣ成分）と高周波成分（ＡＣ成分）とを分離／合流する機能を有しており、図示する様に、“ＤＣ”，“ＲＦ（ＡＣ）”，“ＲＦ（ＡＣ）＋ＤＣ”の３ポートを有し、ハイパスフィルタとローパスフィルタとらなる。
【００５０】
かかる構成により、受信回路側の等化誤差信号（ＤＣ）をバイアスＴ回路４３で高周波信号に合流し、送信回路側のバイアスＴ回路４３´で高周波信号から分離することができる。
【００５１】
図１４は等化誤差信号を受信回路２から送信回路１へ伝達する場合の更に他の例を説明するブロック図であり、複雑化を避けるために、誤差信号の伝達に関係する部分についてのみ示しており、他は省略している。なお、図１４において、図１と同等部分は同一符号により示している。
【００５２】
本回路構成では、可変定電流源回路４５と、高入力抵抗の電流検出回路４６とを用いている。すなわち、受信回路側において、等化誤差信号送信回路２５からの等化誤差信号により可変定電流源４５を制御して、等化誤差信号に応じた電流を生成して伝送路３を介して送信回路側へ送信し、高入力抵抗電流検出回路４６により当該電流を検出することにより、等化誤差信号の伝達が可能である。本構成は、高速信号（送信信号）の送受信回路を集積したＬＳＩの一部とすることも可能である。なお、図において、４４，４４´は直流阻止回路である。
【００５３】
図１５は等化誤差信号を受信回路２から送信回路１へ伝達する場合の別の例を説明するブロック図であり、複雑化を避けるために、誤差信号の伝達に関係する部分についてのみ示しており、他は省略している。なお、図１５において、図１と同等部分は同一符号により示している。
【００５４】
図１の等化誤差検出回路２４にて得られた等化誤差信号は、論理的に正負両極性を持った信号である。この極性は、例えば、電圧や電流値などのようなアナログ値を用いるが、適正が等化がなされていることを示す等化基準値を、等化誤差信号の送信受信回路の双方で、同一とする必要がある。
【００５５】
ここで、高速信号には、差動信号を用いることが一般的であり、そのため、伝送路のパタン配線は２本となっている。この２本の配線の一方を用いて等化誤差信号を伝達し、他方を用いて等化誤差信号の基準値を伝達するようにしている。すなわち、送信すべき高速信号は等化送信回路１１から出力され、バイアスＴ回路４３ａ，４３ｂを介して伝送路３を通り、アンプ２１で受信増幅される。
【００５６】
受信回路２の等化誤差検出回路２４（図１参照）で検出された等化誤差信号は、等化誤差信号送信回路２５において、固定された基準電圧発生回路４７で生成された基準電圧を基に、誤差信号（基準信号に対する差の信号）とされて、バイアスＴ回路４３ｃにおいて伝送路３に重畳される。また、基準電圧発生回路４７からの基準電圧はバイアスＴ回路４３ｄにおいて伝送路３に重畳される。
【００５７】
伝送路３を介して送信回路１へ供給された誤差信号（基準信号に対する差の信号）と基準電圧とは、バイアスＴ回路４３ａ，４３ｂによりそれぞれ高速信号と分離され、差動アンプ４８へ入力される。差動アンプ４８において、基準電圧と誤差信号との差が演算され、等化誤差信号が再生されて等化誤差信号受信回路１３へ入力される様になっている。
【００５８】
なお、図１５の例においては、図３に示した引き算器２４７を省いて、割り算器２５６の出力であるスペクトル強度比の値をそのまま誤差信号として出力し、同時に固定された基準電圧（基準電圧発生回路４７の出力）に代えて、基準メモリ２４５の出力である基準値を出力し、これら誤差信号と基準値とを差動アンプ４８で演算（減算）することで、等化誤差信号を得ることも可能である。
【００５９】
図１に示した送信回路１や受信回路２は、それぞれ１チップ型のＬＳＩ（集積回路）により構成することができることは明白である。
【００６０】
【発明の効果】
以上説明したように、本発明によれば、個々のパタン配線などの伝送路に対する最適な等化パラメータを自動的に検出して設定することにより、従来必要とされていた、人的な工数が削減され、同時に調整時間の削減が可能である。このため、人手を介してＢＷＢの配線長を意識して、個々のＰＫＧに対して等化パラメータを設定していた従来技術に対して、装置の製造コストの削減が可能となり、装置価格の低減が可能となるという効果がある。
【００６１】
また、本発明によれば、配線の追加を必要とせず、信号伝送路と同一の配線を用いて、自動的な帰還制御機構を実現し、長期的な信号伝送特性の安定化制御を可能とするという効果がある。これは、半二重の伝送を行う装置構成に対しても適用が可能であり、送受信回路の外部に、プロセッサのような制御回路を介する通信も不要なために、装置設計面での簡易化を図ることが出来ることになる。
【図面の簡単な説明】
【図１】本発明の実施例を示すブロック図である。
【図２】等化強度と等化誤差との関係及び等化強度に対する送受信波形を示す模式図である。
【図３】図１の等化誤差検出回路２４の例を示すブロック図である。
【図４】送信信号のスペクトル分布とアイパタンの形状を説明する模式図である。
【図５】プリント基板伝送路の伝達特性を説明する模式図である。
【図６】受信信号のスペクトル分布とアイパタンの形状を説明する模式図である。
【図７】アイパタンの形状を説明する模式図である。
【図８】等化基準値を得るためのトレーニング手順の一例を示すフローチャートである。
【図９】本発明の実施例におけるスペクトル強度測定による伝送路の伝達特性の直線近似を説明する模式図である。
【図１０】等化強度と受信信号の符号誤り率特性と、対応するアイパタンの形状を説明する模式図である。
【図１１】等化基準値を得るためのトレーニング手順の他の例を示すフローチャートである。
【図１２】本発明の実施例における等化誤差信号の伝達方法の一例を説明するブロック図である。
【図１３】本発明の実施例における等化誤差信号の伝達方法の他の例を説明するブロック図である。
【図１４】本発明の実施例における等化誤差信号の伝達方法の更に他の例を説明するブロック図である。
【図１５】本発明の実施例における等化誤差信号の伝達方法の別の例を説明するブロック図である。
【図１６】本発明が適用される装置の構成の概略を説明する図である。
【図１７】従来技術を説明するためのブロック図である。
【符号の説明】
１送信回路
２受信回路
３伝送路
１０送信側ＰＫＧ
１１等化送信回路
１２等化量生成制御回路
１３等化誤差信号受信回路
１４パタン発生回路
１５セレクタ
１６，２６制御回路
２０受信側ＰＫＧ
２１アンプ
２２識別回路
２３符号誤り率検出回路
２４等化誤差検出回路
２４１，２４２帯域透過フィルタ
２５等化誤差信号送信回路
３０ＢＷＢ
３１コネクタ
４１，４１´ 高域通過フィルタ
４２，４２´ 低域通過フィルタ
４３，４３´，４３ａ〜４３ｄバイアスＴ回路
４４，４４´ 直流阻止回路
４５可変電流源
４６高入力抵抗電流検出回路
４７基準電圧発生回路
４８差動アンプ
２４３，２４４強度変換器
２４５基準値メモリ
２４６割り算器
２４７引き算器[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal equalization system and a method thereof, and a method of determining an optimal equalization amount of a transmission path, and particularly to a large-capacity communication device such as an IP (Internet Protocol) router or a cross-connect, and a large-scale information processing device such as a supercomputer. The present invention relates to an equalization method for compensating attenuation of a high-frequency component of a transmission signal due to a skin effect of a transmission line conductor, a dielectric loss of an insulating material, etc. in a high-speed interconnection method between a plurality of printed circuit boards constituting the above.
[0002]
[Prior art]
As an example, in FIG. 16, between the different printed circuit boards (referred to as PKG) 10 and 20 of the large-capacity communication device passes through a transmission path 3 of a printed pattern formed on a back wire board (referred to as BWB) 30. Then, a configuration in the case of transmitting and receiving an electric signal will be described. The transmitted electric signal is transmitted from the transmission circuit 1 to the reception circuit 2. In this case, the transmission path 3 includes a pattern wiring formed on the PKGs 10 and 20 and the BWB 30, and a specific pattern of the PKG 10 and the BWB 30. And a connector 31 for electrically connecting the wires.
[0003]
The continuous transmission path 3 from the transmission circuit 1 on the PKG 10 to the reception circuit 2 on the PKG 20 is several tens cm to 2 m or less in the case of BWB 30, and about 1 m to 100 m in the case of using a cable transmission path as an alternative to BWB. . Hereinafter, the case of BWB transmission will be described as a representative.
[0004]
In a region where the bit rate of the electric signal transmitted through the transmission line 3 including the pattern wiring exceeds 1 Gbps, in addition to the DC electric resistance of the conductor forming the transmission line 3, the conduction loss due to the skin effect of the conductor is reduced. Due to the increase, the increase in the dielectric loss of the insulator constituting the PKGs 10 and 20, and the BWB 30, and the reflection of the electric signal at the impedance discontinuity point such as the connector 31, the signal waveform is deteriorated, and the code identification error occurs on the receiving side. appear.
[0005]
Conventionally, a transmission equalization method called pre-emphasis as disclosed in Non-Patent Documents 1 and 2 is applied to this problem. In this transmission equalization method, it is necessary to set different equalization strengths for individual transmission circuits. The reason is as follows. In other words, the transmission path length of the pattern wiring 3 is not constant, but the transmission characteristics of each pattern wiring 3 take different values. This is because, if only the equalization intensity exists and the correction by the equalization is too large than the optimum value, the aperture width of the eye pattern of the received signal is narrowed, which has the opposite effect.
[0006]
FIG. 17 shows a configuration example of an equalization strength setting circuit according to the above-described conventional technique. In the prior art, the equalization strength for compensating the transfer characteristics of the transmission line 3 connecting the transmission circuit 1 and the reception circuit 2 is set for the equalization transmission circuit 11 by the equalization amount generation control circuit 12. There is a need to. In FIG. 17, reference numeral 21 in the reception circuit 2 denotes a reception amplifier (amplifier), and reference numeral 22 denotes an identification circuit for identifying a reception code.
[0007]
[Non-patent document 1]
A. See Fiedler et al. , "A 1.0625 Gbps Transceiver with 2x Oversampling and Transmit Signal Pre-Emphasis," Proc. IEEE Int. l Solids-State Circuits Conf. , Digest of Technical Papers, IEEE Press, Piscataway, N.W. J. , 1997 pp. 238-239.
[0008]
[Non-patent document 2]
M. Fukaishi, K .; Nakamura, M .; Yotsuyanagi, et. al. , "A20-Gb / s CMOS Multi-Channel Transmitter and Receiver Chip Set for Ultra-High Resolution Digital Display, 2000 ISSCC Digestive Technology. 260-261, Feb, 2000.
[0009]
[Problems to be solved by the invention]
In the above-mentioned prior art, the optimum value of the equalization strength set by the equalization amount generation control circuit 12 in the transmission circuit 11 cannot be automatically detected, and it is necessary to explicitly set the value manually or via a program. The problem is that it is not guaranteed that the set equalization strength is optimal.
[0010]
Regarding the former, the arrangement of the PKGs 10 and 20 constituting the device on the BWB 30 is determined only when the device is assembled. Here, it is assumed that the PKG 10 can be connected to a plurality of slots on the BWB 30, and can be shared in function. For example, there may be a plurality of combinations from a case where the PKG 10 and the PKG 20 are arranged spatially adjacent to each other on the BWB 30 to a case where the PKG 10 and the PKG 20 are arranged at both ends of the BWB 30 spatially. At this time, since the wiring length of the transmission path 3 is set to be the same as the longest dimension of the BWB 30 from the shortest several cm, a corresponding change in signal transmission characteristics appears.
[0011]
At the time of manufacturing the PKGs 10 and 20, in order to be unable to know the signal transmission characteristics of the transmission line 3 to which they are connected, a number of PKG types having different equalization strengths are manufactured, or a common PKG is manufactured. It is necessary to set the equalization strength after assembling the apparatus. Despite having a PKG with the same function, manufacturing and managing it as a different type immediately leads to an increase in cost. In addition, when the equalization strength is set as a post-process, human expenses required for the setting are generated, and stocks remain for the time required for the adjustment, which causes an increase in the price of the apparatus.
[0012]
Regarding the reliability of the equalization strength set by the latter, there are problems in that it is difficult to absorb individual differences in the signal transmission characteristics of the transmission path 3 and that it cannot cope with aging. In order to optimize the optimum value of the equalization strength set at the time of assembling the apparatus with respect to the transmission path 3 including each BWB 30 and individual transfer characteristics caused by manufacturing errors of all related circuits, it is necessary to optimize each individual Requires a large number of inspection man-hours. Conversely, reducing the manufacturing error leads to a reduction in the manufacturing yield.
[0013]
Since the transmission path 3 such as BWB and the transmission / reception circuits 1 and 2 have temperature characteristics, fluctuations in signal transmission characteristics and transmission / reception characteristics may occur due to a change in environmental temperature during operation. However, in the setting of the equalization strength in the conventional method, there is no means for returning the difference between the design value of the transfer characteristic and the actual value to the equalization amount generation control circuit 12 of the transmission circuit 1 as the equalization strength. However, there is a possibility that the equalization strength having an error with respect to the transmission characteristics of the actual transmission path is set to operate the apparatus. This may reduce the reception margin in the reception circuit 2 and increase the probability of occurrence of a code identification error.
[0014]
SUMMARY OF THE INVENTION An object of the present invention is to reduce the number of man-hours required conventionally and to reduce the adjustment time, thereby contributing to a reduction in manufacturing costs and equipment costs. An object of the present invention is to provide a method for determining an optimal equalization amount.
[0015]
[Means for Solving the Problems]
In a transmission signal equalization system according to the present invention, when transmitting a signal from a transmission unit to a reception unit via a transmission path, the transmission signal is equalized to compensate for transmission characteristics of the transmission path. A transmission signal equalization system, wherein the receiving unit detects a current equalization amount based on a reception signal passed through the transmission path, and sets a preset optimal equalization amount for the transmission path and a current equalization amount. Providing an equalization error signal generation means for generating an equalization error signal that is a difference from the equalization amount and transmitting the signal to the transmission unit, in the transmission unit, an equalization means for equalizing the transmission signal, An equalization amount control means for controlling the equalization amount of the equalization means based on the equalization error signal from the equalization error signal generation means is provided.
[0016]
In the transmission signal equalization method according to the present invention, when transmitting a signal from a transmission unit to a reception unit via a transmission path, the transmission signal is equalized to compensate for transmission characteristics of the transmission path. A transmission signal equalization method, wherein the receiving unit detects an equalization amount based on a received signal passing through the transmission path and detects a current equalization amount. An equalization error signal generating step of generating an equalization error signal that is a difference between the equalization amount and the current equalization amount, and a step of transmitting the equalization error signal to the transmission unit, the transmission unit In the equalization amount control step of controlling the equalization amount of the equalization means based on the equalization error signal, based on the equalization amount controlled in the equalization amount control step, the equalization means, Equalizing the transmitted signal. The features.
[0017]
The optimal equalization amount detection method according to the present invention is configured such that, when a signal is transmitted from a transmission unit to a reception unit via a transmission path, the transmission signal is equalized to compensate for transmission characteristics of the transmission path. Method for detecting an optimal equalization amount in a transmission signal equalization system, wherein in the transmission unit, a first fixed pattern signal having a first frequency component of a frequency band of the transmission signal, Transmitting a second fixed pattern signal having two frequency components, and, in the receiving unit, measuring the reception strength of the first fixed pattern and the second fixed pattern, respectively, based on these measurement results Detecting a transmission equalization strength, and transmitting a pseudo-random pattern signal by setting an equalization amount opposite to the transmission equalization strength in the transmitting unit; In signal portion, characterized in that it comprises the step of determining the optimal equalization amount based on these measurement results the reception intensity of the first and second frequency components of the pseudo-random pattern signal measured.
[0018]
Another method of detecting an optimum equalization amount according to the present invention performs equalization on a transmission signal to compensate for transmission characteristics of the transmission line when transmitting a signal from a transmission unit to a reception unit via a transmission line. A method for detecting an optimum equalization amount in a transmission signal equalization system as described above, wherein the transmitting section transmits a pseudo-random pattern signal and sweeps an equalization strength in a range between a minimum value and a maximum value; In the unit, each received code error rate during the sweeping of the equalization strength, the reception strength of the first frequency component of the pseudo random pattern signal and the reception strength of the second frequency component different from the frequency are measured, respectively. Collecting the characteristics of the equalization strength and the received bit error rate based on these measurement results, and the step corresponding to the equalization strength taking the minimum received code error rate based on the characteristics. And seeking the ratio of the reception intensity of the second receiving frequency components, characterized in that it comprises a step of said optimal equalization amount.
[0019]
The operation of the present invention will be described. In transmitting a signal from a transmission unit to a reception unit via a transmission path, in a transmission signal equalization system that performs equalization on a transmission signal for compensation of transmission characteristics of the transmission path, the reception unit includes: Detecting the current equalization amount based on the received signal that has passed through the transmission path, and generating an equalization error signal that is a difference between a preset, optimal equalization amount for the transmission path and the current equalization amount. The signal is transmitted to the transmission unit, and the transmission unit controls the equalization amount of the equalization circuit based on the equalization error signal.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing one embodiment of the present invention, and the same parts as those in FIGS. Referring to FIG. 1, a transmission circuit 1 and a reception circuit 2 are connected via a transmission line 3. The transmission circuit 1 receives an equalization error signal from an equalization transmission circuit 11 having a transmission equalization function, an equalization amount generation control circuit 12 for generating an equalization amount of the transmission circuit 11, and a reception circuit 2. And an equalization error signal receiving circuit 13 for controlling the equalization amount of the equalization amount generation control circuit 12, and a predetermined equalization reference value used for generating an equalization reference value for automatic equalization according to the present invention. It has a pattern generation circuit 14 for generating a pattern, a selector 15 for selecting an output of the pattern generation circuit 14 and a transmission signal, and a control unit 16 for controlling these components.
[0021]
The receiving circuit 2 includes an amplifier (amplifier) 21, an identification circuit 22 for identifying the code of the output of the amplifier, a code error rate detection circuit 23 for detecting a code error rate of the output of the identification circuit 22, and an output of the amplifier 21. An equalization error detection circuit 24 that detects an equalization error from the control signal, an equalization error signal transmission circuit 25 that feeds back the detected equalization error to the transmission circuit 1 and transmits the same, and controls the equalization error detection circuit 24 and the like. And a control unit 26 that performs the operation.
[0022]
The transmission signal input to the transmission circuit 11 is subjected to transmission equalization processing in the equalization transmission circuit 11 and transmitted to the transmission path 3. The transmission equalization strength (equalization amount) at this time is provided from the equalization amount control circuit 12. The transmission signal transmitted through the transmission path 3 is amplified by the amplifier 21 of the reception circuit 2 and input to the identification circuit 22 and the equalization error detection circuit 24. The identification circuit 22 identifies the code of the input signal and outputs it as a reproduction signal to the outside.
[0023]
The equalization error detection circuit 24 optimizes the equalization of the current equalization state and the transfer characteristic of the transmission path 3 by the equalization transmission circuit 11 by observing the eye opening of the reception signal output from the amplifier 21. An error from the state where the operation is being performed is detected. The amount of this error is sent to the equalization error signal reception circuit 13 of the transmission circuit 1 as an error signal defined by an analog value having both positive and negative polarities such as a voltage value or a current value in the equalization error signal transmission circuit 25. introduce.
[0024]
The equalization error that changes during operation is a sufficiently slow change such as a change in environmental temperature or deterioration over time, and there is no fast fluctuation factor. For this purpose, the equalization error signal transmission circuit 25 is provided with a low-pass filter having a sufficiently long time constant to remove short-term fluctuation components and to reduce an error signal to be transmitted to the transmission circuit 1. And has a function of performing sufficient smoothing. The equalization error signal receiving circuit 13 receives the error signal generated by the receiving circuit 2 and controls the equalization amount so as to correct the currently set equalization amount.
[0025]
FIG. 2 exemplarily shows a relationship between the equalization strength (equalization amount) and the equalization error, and a schematic diagram of transmission / reception signals at both ends of the transmission path 3 at that time. The horizontal axis of the graph in FIG. 2 indicates the equalization strength, and the vertical axis indicates the magnitude of the error signal at that time. There is an optimum point in the equalization strength depending on the transmission characteristics of the transmission path. When the equalization is optimal, the error signal becomes zero and the eye opening of the received signal waveform becomes maximum. When the equalization strength is small, the high-frequency component of the waveform after transmission through the transmission path is reduced, and the eye opening width of the received signal is reduced. Conversely, if the equalization strength is excessive, the amplitude of the eye opening of the received signal becomes smaller than the full width, so that the receiving condition is not optimal.
[0026]
FIG. 3 shows a specific configuration of the equalization error detection circuit 24. The equalization error detection circuit 24 includes two narrow band pass filters (BPFs) 241 and 242 having different transmission center frequencies, intensity converters (PDEFs) 243 and 244, a division calculator 246, and a reference memory (MEM). ) 245 and a subtractor 247.
[0027]
The reception signal amplified by the amplifier 21 of the reception circuit 2 is input to two band-pass filters 241 and 242. The transmission center frequency f0 of the band transmission filter 241 is, for example, half the frequency of the bit rate of the transmission signal. The transmission center frequency f1 of the other band transmission filter 242 is set to a lower frequency than that of the band transmission filter 241.
[0028]
FIG. 4 shows a schematic diagram of the signal spectrum. In a signal spectrum having an ideal eye opening, the intensities of f0 and f1 each correspond to the size of the arrow, and the eye opening at this time becomes the maximum. On the other hand, in the spectrum of a signal transmitted through a transmission line such as a printed circuit board having a transmission characteristic as shown in FIG. 5 in which the high-frequency component is greatly attenuated, as shown in FIG. The intensity ratio greatly differs from the ideal value.
[0029]
As a simple example, a case where the bit rate of the transmission signal is 2 Gbps will be described with reference to FIG. In a 2 Gbps signal, a repeated bit pattern of “010101...” Can be regarded as equivalent to a 1 GHz sine wave as shown in the upper part of FIG. In other words, the cut-off frequency of the transmission line for opening the eye pattern sufficiently is at most 1 GHz. Thereby, the transmission center frequency of the band transmission filter 241 is set to 1 GHz.
[0030]
On the other hand, when the waveform is degraded due to the transmission characteristics of the transmission path, for example, when the amplitude of a 1-bit isolated pulse obtains a normal amplitude after 4 bits as shown in the lower part of FIG. It is desirable that the center frequency f1 of the bandpass filter 242 be f0 / 4.
[0031]
Outputs of the band-pass filters 241 and 242 are converted into spectral intensities f0 and f1, P (f0) and P (f1) by intensity detectors 243 and 244, respectively, and subsequently by a divider 246. , The obtained two spectral intensity ratios P (f0) / P (f1) are obtained. An equalization error signal is generated using a subtractor 247 from a difference between the spectrum intensity ratio obtained by the above-described measurement and a reference value stored in the reference memory 245 and indicating the spectrum intensity ratio of the best received waveform. Will be done.
[0032]
A method of determining an equalization reference value stored in the reference memory 245 will be described. This equalization reference value is generated using a training pattern. This will be described using the above-described example. Two fixed patterns are used to determine the intensities of the two spectral components f0 and f1. One is a pattern of “01010101...” In which “0” and “1” are alternately changed bit by bit, and is a pattern used to obtain the intensity of f0. The other pattern is, for example, a pattern of “000011111...” That alternates between “0” and “1”, each of which is continuous by 4 bits, and is a pattern used to obtain the intensity of f1.
[0033]
Here, f1 = f0 / 4, but the latter signal pattern is a rectangular wave having up to 2 × f0 frequency components. However, since the coefficient of the fundamental wave when the latter signal pattern is subjected to Fourier series expansion is 1, it is possible to obtain the spectrum intensity of f1 using a long-period rectangular wave.
[0034]
FIG. 8 is a flowchart illustrating an example of a training procedure for obtaining an equalization reference value. In the initialization routine of the transmission / reception system, the equalization strength of the equalization transmission circuit 11 is set to zero (step S1), and the above-mentioned two fixed patterns are transmitted by the pattern generation circuit 14 as a training pattern (step S2). S4) Measure the respective spectral intensities P (f0) 0 and P (f1) 0 of the received signal (steps S3 and S5). The spectral intensities at the two points obtained here are obtained by linearly approximating the actual transfer characteristics as shown in FIG. From this result, the transmission equalization strength is approximately obtained as P (f1) 0 / P (f0) 0 (step S6).
[0035]
Next, a pseudo-random pattern is generated by the pattern generation circuit 14 of the transmission circuit 1 and transmitted from the transmission circuit 1 to the transmission line 3. At this time, the transmission equalization strength in the equalization transmission circuit 11 of the transmission circuit 1 performs equalization corresponding to the inverse characteristic of the transfer characteristic obtained by the above-mentioned training pattern. Specifically, equalization is performed so that the spectrum intensity of the band of f0 is P (f1) 0 / P (f0) 0 times as large as that of f1 (step S7).
[0036]
The pseudo random pattern subjected to the equalization is transmitted (step S8), and P (f0) 1 and P (f1) 1 are measured in the equalization error detection circuit 24 of the reception circuit 2 (step S9). Then, the intensity ratio P (f0) 1 / P (f1) 1 is stored as the best received waveform spectrum intensity ratio in the reference memory 245 (step S11).
[0037]
Next, referring to FIG. 10, the optimum value of the equalization strength for a certain transmission path is defined at a certain one point between the minimum and the maximum of the equalization strength, and the eye opening at that time is the maximum. Become. If the error of the equalization strength becomes larger than the optimum value, the eye opening of the received signal becomes narrower even if the equalization strength is too large or too small, and the bit error rate increases. A procedure for obtaining the optimum equalization strength using this characteristic will be described below.
[0038]
FIG. 11 is a flowchart showing an example of a training procedure for obtaining an equalization reference value in this case. In the transmission circuit 1, the equalization strength of the equalization transmission circuit 11 is swept from the minimum to the maximum in a stepwise manner every unit time while transmitting the pseudo random pattern signal by the pattern generation circuit 14 (step S21). At this time, the receiving circuit 2 counts the bit error rate of the received signal at the same cycle as the unit time, and simultaneously obtains the bit error rate characteristics corresponding to the graph of FIG. 10 and the spectrum intensities P (f0) and P (f1). ) Is collected (step S22).
[0039]
In the collected bit error rate characteristics, the equalization strength that takes the minimum bit error rate is the optimum equalization strength (step S23). P (f0) / P (f1) at that time is stored in the reference memory 245 (Step S25) as the spectrum intensity ratio of the best received waveform (Step S24).
[0040]
Alternatively, in the sampled bit error rate characteristics, two points of the equalization strength at which a certain appropriate bit error rate is obtained can be found from the optimum equalization strength, that is, an excessive direction and an excessive direction. The average value of the equalization intensities at the two points is set as the optimum equalization intensity, and P (f0) / P (f1) at that time is stored in the reference memory 245 as the spectrum intensity ratio of the best received waveform. good.
[0041]
The processing flow shown in FIGS. 8 and 11 is performed in cooperation with the control unit 16 of the transmission circuit 1 and the control unit 26 of the reception circuit 2.
[0042]
Next, a method of transmitting the equalization error signal obtained from the equalization error detection circuit from the reception circuit 2 to the transmission circuit 1 will be described. The error signal may be transmitted to the transmission circuit 1 by using a wiring dedicated to the error signal separately from the wiring of the high-speed signal to be transmitted. However, the use of separate wiring requires the design of separate wiring, and at the same time, requires connection terminals for BWB and PKG, which leads to an increase in the number of terminals.
[0043]
Therefore, the present invention focuses on the fact that the change in the error signal is sufficiently slower than the change in the transmitted high-speed signal (transmission signal), and the error signal and the high-speed signal can be easily superimposed and separated. A method of transmitting the error signal to the transmission circuit 1 using a possible circuit and the same wiring pattern as the high-speed signal is used.
[0044]
FIG. 12 is a block diagram illustrating an example of a case where an equalization error signal is transmitted from the reception circuit 2 to the transmission circuit 1, and only parts related to transmission of the error signal are shown in order to avoid complication. , Others are omitted. In FIG. 12, the same parts as those in FIG. 1 are indicated by the same reference numerals.
[0045]
In FIG. 12, an equalization error signal transmission circuit includes an equalization transmission circuit 11 for a high-speed signal (transmission signal), an amplifier 21 as a reception amplifier, and an equalization error signal for transmission of the equalization error signal. The transmission circuit 25, the equalization error signal reception circuit 13, the transmission path 3, the high pass filters (HPF) 41, 41 ', and the low pass filters (LPF) 42, 42'.
[0046]
As the cutoff frequency of the low-pass filters 42 and 42 ', a frequency sufficiently lower than the signal band of the high-speed signal (transmission signal) is used. For example, it is realistic to set the frequency to 1 / 10,000 or less of the bit rate of the high-speed signal.
[0047]
In the configuration shown in FIG. 12, a high-speed signal (transmission signal) transmitted from the equalizing transmission circuit 11 to the reception-side amplifier 21 passes through the high-pass filters 41 and 41 ′, but the low-pass filters 42 and 42 ′. ′, There is no signal attenuation or deterioration due to branching of the equalization error signal to the equalization error signal transmission circuit 25 and the equalization error signal reception circuit 13. Conversely, the equalization error signal behaves almost DC-like when compared with the high-speed signal band, and is equalized by the high-pass filters 41 and 41 'to the equalization transmission circuit 11 and the reception-side amplifier 21. There is no inflow of the signal, and the high-speed signal (transmission signal) and the equalization error signal can be transmitted as independent signals on the same transmission path 3 without interfering with each other.
[0048]
FIG. 13 is a block diagram illustrating another example in which an equalization error signal is transmitted from the receiving circuit 2 to the transmitting circuit 1, and only parts related to the transmission of the error signal are shown in order to avoid complication. And others are omitted. In FIG. 13, the same parts as those in FIG. 1 are indicated by the same reference numerals.
[0049]
In this circuit configuration, bias T circuits 43 and 43 'are used instead of the high-pass filters 41 and 41' and the low-pass filters 42 and 42 'in FIG. 12, and are equivalent to the configuration described in FIG. The effect of can be obtained. As is well known, the bias T circuit has a function of separating / merging a low-frequency component (DC component) and a high-frequency component (AC component), and as shown in the figure, “DC”, “RF (AC ) "And" RF (AC) + DC ", and constitutes a high-pass filter and a low-pass filter.
[0050]
With this configuration, the equalization error signal (DC) on the receiving circuit side can be combined with the high-frequency signal by the bias T circuit 43 and separated from the high-frequency signal by the bias T circuit 43 'on the transmission circuit side.
[0051]
FIG. 14 is a block diagram for explaining still another example in which an equalization error signal is transmitted from the receiving circuit 2 to the transmitting circuit 1. In order to avoid complication, only a portion related to the transmission of the error signal is shown. And others are omitted. In FIG. 14, the same parts as those in FIG. 1 are indicated by the same reference numerals.
[0052]
In this circuit configuration, a variable constant current source circuit 45 and a current detection circuit 46 having a high input resistance are used. That is, on the receiving circuit side, the variable constant current source 45 is controlled by the equalization error signal from the equalization error signal transmission circuit 25 to generate a current corresponding to the equalization error signal and transmit it via the transmission line 3. By transmitting the current to the circuit side and detecting the current by the high input resistance current detection circuit 46, it is possible to transmit an equalization error signal. This configuration can be a part of an LSI in which a transmission / reception circuit for a high-speed signal (transmission signal) is integrated. In the figure, reference numerals 44 and 44 'denote DC blocking circuits.
[0053]
FIG. 15 is a block diagram illustrating another example in which an equalization error signal is transmitted from the reception circuit 2 to the transmission circuit 1, and only parts related to the transmission of the error signal are shown in order to avoid complication. And others are omitted. In FIG. 15, the same parts as those in FIG. 1 are indicated by the same reference numerals.
[0054]
The equalization error signal obtained by the equalization error detection circuit 24 in FIG. 1 is a signal having logically both positive and negative polarities. For this polarity, for example, an analog value such as a voltage or a current value is used, but an equalization reference value indicating that equalization has been performed is the same in both of the equalization error signal transmission and reception circuits. It is necessary to
[0055]
Here, a differential signal is generally used for a high-speed signal, and therefore, there are two pattern wirings in a transmission line. One of the two wirings is used to transmit an equalization error signal, and the other is used to transmit a reference value of the equalization error signal. That is, the high-speed signal to be transmitted is output from the equalizing transmission circuit 11, passes through the transmission line 3 via the bias T circuits 43a and 43b, and is amplified by the amplifier 21.
[0056]
The equalization error signal detected by the equalization error detection circuit 24 (see FIG. 1) of the reception circuit 2 is based on the reference voltage generated by the fixed reference voltage generation circuit 47 in the equalization error signal transmission circuit 25. Then, the error signal (difference signal with respect to the reference signal) is superimposed on the transmission line 3 in the bias T circuit 43c. The reference voltage from the reference voltage generation circuit 47 is superimposed on the transmission line 3 in the bias T circuit 43d.
[0057]
The error signal (the difference signal with respect to the reference signal) and the reference voltage supplied to the transmission circuit 1 via the transmission path 3 are separated from the high-speed signal by the bias T circuits 43a and 43b, respectively, and input to the differential amplifier 48. You. In the differential amplifier 48, the difference between the reference voltage and the error signal is calculated, and the equalized error signal is reproduced and input to the equalized error signal receiving circuit 13.
[0058]
In the example of FIG. 15, the subtracter 247 shown in FIG. 3 is omitted, the value of the spectrum intensity ratio output from the divider 256 is output as it is as an error signal, and the fixed reference voltage (reference voltage A reference value which is an output of the reference memory 245 is output in place of the output of the generation circuit 47, and the error signal and the reference value are calculated (subtracted) by the differential amplifier 48 to obtain an equalization error signal. It is also possible.
[0059]
It is apparent that the transmission circuit 1 and the reception circuit 2 shown in FIG. 1 can be each configured by a one-chip type LSI (integrated circuit).
[0060]
【The invention's effect】
As described above, according to the present invention, by automatically detecting and setting the optimal equalization parameter for the transmission path such as an individual pattern wiring, the conventionally required man-hour is reduced. The adjustment time can be reduced at the same time. For this reason, the manufacturing cost of the device can be reduced as compared with the conventional technology in which the equalization parameter is set for each PKG by manually considering the wiring length of the BWB, and the device price is reduced. There is an effect that it becomes possible.
[0061]
Also, according to the present invention, it is possible to realize an automatic feedback control mechanism using the same wiring as the signal transmission path without requiring additional wiring, and to perform long-term stable control of signal transmission characteristics. There is an effect of doing. This can be applied to a device configuration that performs half-duplex transmission, and since there is no need for communication via a control circuit such as a processor outside the transmission / reception circuit, simplification in device design is possible. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a relationship between an equalization strength and an equalization error and a transmission / reception waveform with respect to the equalization strength;
FIG. 3 is a block diagram illustrating an example of an equalization error detection circuit 24 of FIG. 1;
FIG. 4 is a schematic diagram illustrating a spectrum distribution of a transmission signal and a shape of an eye pattern.
FIG. 5 is a schematic diagram illustrating transfer characteristics of a printed circuit board transmission line.
FIG. 6 is a schematic diagram illustrating a spectrum distribution of a received signal and a shape of an eye pattern.
FIG. 7 is a schematic diagram illustrating the shape of an eye pattern.
FIG. 8 is a flowchart illustrating an example of a training procedure for obtaining an equalization reference value.
FIG. 9 is a schematic diagram illustrating linear approximation of transfer characteristics of a transmission line by spectrum intensity measurement according to the embodiment of the present invention.
FIG. 10 is a schematic diagram illustrating equalization strength, code error rate characteristics of a received signal, and a corresponding eye pattern shape.
FIG. 11 is a flowchart illustrating another example of a training procedure for obtaining an equalization reference value.
FIG. 12 is a block diagram illustrating an example of a method for transmitting an equalization error signal according to an embodiment of the present invention.
FIG. 13 is a block diagram illustrating another example of a method of transmitting an equalization error signal according to an embodiment of the present invention.
FIG. 14 is a block diagram illustrating still another example of a method of transmitting an equalization error signal according to an embodiment of the present invention.
FIG. 15 is a block diagram illustrating another example of a method of transmitting an equalization error signal according to the embodiment of the present invention.
FIG. 16 is a diagram schematically illustrating the configuration of a device to which the present invention is applied.
FIG. 17 is a block diagram for explaining a conventional technique.
[Explanation of symbols]
1 Transmission circuit
2 Receiver circuit
3 Transmission line
10 Sender PKG
11 Equalization transmission circuit
12 Equalization generation control circuit
13 Equalization error signal receiving circuit
14 Pattern generation circuit
15 Selector
16, 26 control circuit
20 Receiver PKG
21 amplifier
22 Identification circuit
23 Code error rate detection circuit
24 Equalization error detection circuit
241, 242 Band transmission filter
25 Equalization error signal transmission circuit
30 BWB
31 Connector
41, 41 'high-pass filter
42, 42 'low-pass filter
43, 43 ', 43a to 43d Bias T circuit
44, 44 'DC blocking circuit
45 Variable current source
46 High input resistance current detection circuit
47 Reference voltage generation circuit
48 differential amplifier
243,244 intensity converter
245 Reference value memory
246 divider
247 subtractor

Claims

When transmitting a signal from a transmission unit to a reception unit via a transmission path, a transmission signal equalization system that performs equalization on the transmission signal to compensate for transmission characteristics of the transmission path,
In the receiving unit,
A current equalization amount is detected based on the received signal that has passed through the transmission line, and an equalization error signal that is a preset difference between the optimal equalization amount for the transmission line and the current equalization amount is generated. And providing an equalization error signal generating means for transmitting to the transmitting unit,
In the transmitting unit,
Equalizing means for equalizing the transmission signal,
A transmission signal equalization system comprising: an equalization amount control unit that controls an equalization amount of the equalization unit based on the equalization error signal from the equalization error signal generation unit.

2. The transmission signal or the like according to claim 1, wherein the equalization error signal generation unit includes a unit that detects a reception intensity ratio of the reception signal at two different frequencies and sets the current equalization amount. System.

The equalization error signal generation unit includes a storage unit that stores the optimum equalization amount in advance, and a unit that detects a difference between an output of the storage unit and the current equalization amount. Item 3. The transmission signal equalization system according to Item 1 or 2.

The equalization error signal generating means has means for superimposing the equalization error signal on the transmission signal on the transmission path,
The transmission signal equalization system according to any one of claims 1 to 3, wherein the reception unit includes means for separating the equalized error signal superimposed on the transmission path.

5. The transmission signal equalization system according to claim 4, wherein said superimposing means and said separating means are configured using a high-pass filter and a low-pass filter.

The said superimposing means is a variable constant current source whose output current is varied according to the equalization error signal, and the separating means is a high input resistance type current detection circuit. 4. The transmission signal equalization system according to 4.

The transmission path is a pair of transmission paths for differential signals, one of which transmits the difference between the equalization error signal and the reference voltage, and the other which transmits the reference voltage,
5. The transmission signal equalization system according to claim 4, wherein the receiving unit detects a difference between the difference and the reference voltage and uses the difference as the equalization error signal.

The transmission path is a pair of transmission paths for differential signals, one of which transmits the current equalization amount, the other transmitting the optimal equalization amount,
The transmission signal equalization system according to claim 4, wherein the receiving unit detects a difference between the current equalization amount and the optimal equalization amount and uses the difference as the equalization error signal.

Each of the means constituting the transmitting unit is included in a one-chip integrated circuit, and each of the means constituting the receiving unit is included in a one-chip integrated circuit. Item 9. A transmission signal equalization system according to any one of Items 1 to 8.

When transmitting a signal from a transmission unit to a reception unit via a transmission path, a transmission signal equalization method that performs equalization on a transmission signal to compensate for transmission characteristics of the transmission path,
In the receiving unit,
Equalization amount detection step of detecting the current equalization amount based on the received signal that has passed through the transmission path,
An equalization error signal generation step of generating an equalization error signal that is a preset difference between the optimal equalization amount for the transmission path and the current equalization amount,
Transmitting the equalization error signal to the transmission unit,
In the transmitting unit,
An equalization amount control step of controlling the equalization amount of the equalization means based on the equalization error signal,
Performing the equalization of the transmission signal by the equalization means based on the equalization amount controlled in the equalization amount control step.

11. The transmission signal equalization method according to claim 10, wherein in the equalization amount detection step, a reception intensity ratio at two different frequencies of the received signal is detected and set as the current equalization amount.

12. The transmission signal or the like according to claim 10, wherein the equalization error signal generating step detects a difference between an output of a storage unit in which the optimum equalization amount is stored in advance and the current equalization amount. Method.

The transmitting step has a step of superimposing the equalization error signal on the transmission signal on the transmission path,
13. The transmission signal equalization method according to claim 10, wherein the receiving unit includes a step of separating the superimposed equalization error signal on the transmission path.

When transmitting a signal from a transmission unit to a reception unit via a transmission path, an optimal equalization amount in a transmission signal equalization system configured to perform equalization on the transmission signal to compensate for transmission characteristics of the transmission path. A detection method,
In the transmitting unit,
A first fixed pattern signal having a first frequency component of the frequency band of the transmission signal, and transmitting a second fixed pattern signal having a second frequency component different from the frequency,
In the receiving unit,
The step of measuring the reception strength of the first fixed pattern and the second fixed pattern, respectively, and detecting the transmission equalization strength based on these measurement results,
In the transmitting unit,
Transmitting a pseudo-random pattern signal by setting an equalization amount that is opposite to the transmission equalization strength,
In the receiving unit,
Measuring the reception intensities of the first and second frequency components of the pseudo-random pattern signal, respectively, and determining the optimal equalization amount based on the measurement results. Method.

When transmitting a signal from a transmission unit to a reception unit via a transmission path, an optimal equalization amount in a transmission signal equalization system configured to perform equalization on the transmission signal to compensate for transmission characteristics of the transmission path. A detection method,
In the transmitting unit,
Sweeping the equalization strength in a range between a minimum value and a maximum value while transmitting a pseudo random pattern signal;
In the receiving unit,
Measuring each reception code error rate during the sweeping of the equalization strength, and the reception strength of a first frequency component of the pseudo-random pattern signal and the reception strength of a second frequency component different from the frequency. ,
Collecting characteristics of the equalization strength and the received bit error rate based on these measurement results;
Determining the ratio of the reception intensity of the first and second reception frequency components corresponding to the equalization intensity taking the minimum reception code error rate based on this characteristic and setting the ratio as the optimal equalization amount. The optimal equalization amount detection method.