JP3963132B2

JP3963132B2 - Communications system

Info

Publication number: JP3963132B2
Application number: JP2002204731A
Authority: JP
Inventors: 直樹梅田; 英雄阪本; 光治池田
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 2002-07-12
Filing date: 2002-07-12
Publication date: 2007-08-22
Anticipated expiration: 2022-07-12
Also published as: JP2004048500A

Description

【０００１】
【発明の属する技術分野】
本発明は、データ信号の送受信を行う通信システムに関するものである。
【０００２】
【従来の技術】
図９は従来の一般的な通信システムの一構成例を示す図である。この図に示す通信システムは、複数の通信端末１００と、これらの各通信端末１００に分岐接続される平衡２線ケーブル（ペア線）Ｃとにより構成され、複数の通信端末１００が平衡２線ケーブルＣを介して相互にデータ信号を送受信するようになっている。
【０００３】
通信端末１００は、平衡２線ケーブルＣで当該通信端末１００を他の通信端末１００と接続するための端子部１００ｉと、データ信号の送信及び受信などの各種処理を実行するＣＰＵ部１００ｆと、このＣＰＵ部１００ｆからの送信するべきデータ信号から被変調波信号を生成し、これを端子部１００ｉから他の通信端末１００に送信する信号送信部１００ｂと、信号送信部１００ｂが送信した自らの被変調波信号を受信し、これを復調して得られるデータ信号を信号衝突検出部１００ｅに出力する送信信号受信部１００ｃと、端子部１００ｉに入来する平衡２線ケーブルＣからの被変調波信号を受信し、これを復調して得られるデータ信号をＣＰＵ部１００ｆおよび信号衝突検出部１００ｅに出力する伝送信号受信部１００ｄと、送信信号受信部１００ｃと伝送信号受信部１００ｄとが受信して得られた夫々のデータ信号を比較することにより平衡２線ケーブルＣ上のデータ信号の衝突を検出する信号衝突検出部と、信号送信部１００ｂの出力および伝送信号受信部１００ｄの入力と端子部１００ｉとの間に介設される２線４線変換回路１００ａと、交流電源の交流電力を直流電力に変換する電源部１００ｇと、この電源部１００ｇで変換された直流電力から駆動電力を生成して各部に供給する内部電源１００ｈとを備えている。
【０００４】
このような通信システムでは、通信端末１００の信号送信部１００ｂでデータ信号および搬送波信号から被変調波信号が生成され、２線４線変換回路１００ａを経由して平衡２線ケーブルＣ上に送信される。送信された被変調波信号は、別の通信端末１００に受信され、その伝送信号受信部１００ｄで復調され、元のデータ信号に復号される。
【０００５】
ここで、平衡２線ケーブルＣ上の伝送信号の周波数については、上りと下りとで同一の周波数帯域が使用される。配線形態は任意の箇所で分岐が可能なマルチドロップであり、分岐点では直接平衡２線ケーブルＣ同士が結ばれる。
【０００６】
このような通信方式の場合、複数の通信端末１００が同時に送信すると、平衡２線ケーブルＣに送信された信号が衝突し、何れの通信端末１００においても通信相手の信号を正常に受信することができなくなる。このため、一般的に、各通信端末１００は、送信前に、伝送信号受信部１００ｄで受信されるデータ信号を監視することにより、平衡２線ケーブルＣ上に送信中の信号が有るか無いかを検出することになっている。そして、平衡２線ケーブルＣ上に送信中の信号が有ることを検出した場合には、送信時点を延期し、再度検出を行って送信中の信号が無ければ送信を行うように送信タイミングの調整が行われるようになっている。
【０００７】
また、通信装置１００は、被変調波信号の送信中には、信号衝突検出部１００ｅにてデータ信号が正常に送信されているのか、他の通信装置１００から送信されたデータ信号と衝突していないのかを検出している。つまり、伝送信号受信部１００ｄと送信信号受信部１００ｃとのデータ信号が一致した場合には、平衡２線ケーブルＣ上に伝送されている信号は１つであり信号の衝突は起こっていないと判断し、一致しない場合には、平衡２線ケーブルＣ上に伝送されている信号は複数あり、信号の衝突が起こっていると判断する。データ信号の衝突を検出した場合には、送信中の被変調波信号を停止させ、時間をおいて再び被変調波信号の送信を試みる。
【０００８】
【発明が解決しようとする課題】
しかしながら、上記従来の通信システムでは、信号の衝突を回避しつつ信号の送受信を好適に行うことができるものの、平衡２線ケーブルＣの分岐点ｘでは、直接ケーブル同士が接続されるために、その分岐点ｘで平衡２線ケーブルのインピーダンスが低下してしまい、伝送信号である被変調波信号が減衰および反射するという問題があった。また、これにより、被変調波信号の振幅が小さくなり、被変調波信号が大きな歪みを持つようになると、データ信号の復調が不可能となり、伝送距離および分岐接続数の両最大値を増加することができない。
【０００９】
本発明は上記問題点に鑑みて為されたものであって、その目的とするところは、衝突検出機能を有した通信システムにおいて、伝送距離および分岐接続数の両最大値を増加することができる通信システムを提供することにある。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成され、前記分岐器は、前記送り端子部からの被変調波信号を増幅する受信信号増幅器と、前記分岐端子部からの被変調波信号を増幅する送信信号増幅器と、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し、第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力する２つのハイブリッド回路とを有し、一方の前記ハイブリッド回路の第１の入出力端子を前記分岐回路部と前記分岐端子部との間で前記分岐回路部側に接続し、他方のハイブリッド回路の第１の入出力端子を前記分岐回路部と前記分岐端子部との間で前記分岐端子部側に接続し、２つの前記ハイブリッド回路の第２，第３の入出力端子間を、前記受信信号増幅器と前記送信信号増幅器とで接続した。
【００１２】
請求項２の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成され、前記通信端末は、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力するハイブリッド回路を有し、前記ハイブリッド回路の第１の入出力端子を前記平衡２線ケーブルと接続し、前記ハイブリッド回路の第２の入出力端子と前記信号送信部との間に、前記信号送信部からの被変調波信号を増幅する送信信号増幅器を接続し、前記ハイブリッド回路の第３の入出力端子と前記伝送信号受信部との間に、前記平衡２線ケーブルからの被変調波信号を増幅する受信信号増幅器を接続して構成され、前記送信信号増幅器と前記受信信号増幅器は、合わせて、前記ハイブリッド回路における逆結合減衰量分だけ被変調波信号を増幅させるものとした。
【００１３】
請求項３の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成され、前記通信端末は、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力するハイブリッド回路を有し、前記ハイブリッド回路の第１の入出力端子を前記平衡２線ケーブルと接続し、前記ハイブリッド回路の第２の入出力端子と前記信号送信部との間に、前記信号送信部からの被変調波信号を増幅する送信信号増幅器を接続し、前記ハイブリッド回路の第３の入出力端子と前記伝送信号受信部とを接続して構成され、前記送信信号増幅器は、前記ハイブリッド回路における逆結合減衰量分だけ被変調波信号を増幅させるものとした。
【００１４】
【発明の実施の形態】
以下、本発明を実施形態１から実施形態３と実施形態に関連した参考例とによって説明する。
（参考例）
図１は本発明に関連した参考例の通信システムの構成例を示す図、図２は同通信システムにおける通信端末の構成図、図３は同通信システムにおける分岐器の構成図である。
【００１５】
参考例の通信システムは、図１に示すように、複数の通信端末１と、これらの各通信端末１に接続される分岐器２と、これらの各分岐器２間に接続される平衡２線ケーブルＣ１とにより構成され、複数の通信端末１が分岐器２および平衡２線ケーブルＣ１を介して相互にデータ信号を送受信するようになっている。
【００１６】
通信端末１は、図２に示すように、平衡２線ケーブルＣ２を介して直下の（当該通信端末１に接続される）分岐器２と接続される端子部１ｉと、データ信号の送信および受信などの各種処理を実行するＣＰＵ部１ｆと、このＣＰＵ部１ｆからの送信するべきデータ信号から被変調波信号を生成し、これを直下の分岐器２経由で他の通信端末１に送信する信号送信部１ｂと、信号送信部１ｂが送信した自らの被変調波信号を受信し、これを復調して得られるデータ信号を信号衝突検出部１ｅに出力する送信信号受信部１ｃと、端子部１ｉに入来する平衡２線ケーブルＣ１，Ｃ２からの被変調波信号を受信し、これを復調して得られるデータ信号をＣＰＵ部１ｆおよび信号衝突検出部１ｅに出力する伝送信号受信部１ｄと、送信信号受信部１ｃと伝送信号受信部１ｄとが受信し復調して得られた夫々のデータ信号を比較することにより平衡２線ケーブルＣ１，Ｃ２上のデータ信号の衝突を検出する信号衝突検出部１ｅと、信号送信部１ｂの出力および伝送信号受信部１ｄの入力と端子部１ｉとの間に介設される２線４線変換回路１ａと、交流電源の交流電力を直流電力に変換する電源部１ｇと、この電源部１ｇで変換された直流電力から駆動電力を生成して各部に供給する内部電源１ｈとを備えている。
【００１７】
分岐器２は、図３に示すように、平衡２線ケーブルＣ１と接続するための一対の送り端子部２ａ，２ｂと、平衡２線ケーブルＣ２を介して当該分岐器２を通信端末１に接続するための分岐端子部２ｃとを備えているほか、分岐回路部２ｄを備えている。
【００１８】
尚、送り端子部２ａの端子２０，２１および送り端子部２ｂの端子２２，２３は、それぞれ、分岐器２の内部で互いに電気的に接続されている。
【００１９】
分岐回路部２ｄは、一対の送り端子部２ａ，２ｂのうち一方の送り端子部に入来する被変調波信号に対して、他方の送り端子部から送出される被変調波信号の減衰が少なくなるように、分岐点を高インピーダンスで接続し、分岐端子部２ｃのインピーダンスが被変調波信号の伝送線路の特性インピーダンスに等しくなるように構成される。則ち、一対の送り端子部２ａ，２ｂ間の両ラインＬＮ１，ＬＮ２と分岐端子部２ｃとの間に介設され平衡２線ケーブルＣ１に対してハイインピーダンスとなる一対の抵抗Ｒ１，Ｒ２と、これらの抵抗Ｒ１，Ｒ２と両ラインＬＮ１，ＬＮ２との間に直列に介設される一対のコンデンサＣ１，Ｃ２と、一対の抵抗Ｒ１，Ｒ２と分岐端子部２ｃとの間に介設され平衡２線ケーブルＣ２とインピーダンス整合をとるためのトランスＴ１と、このトランスＴ１と分岐端子部２ｃとの間に介設される一対のコンデンサＣ３，Ｃ４とにより構成される。
【００２０】
コンデンサＣ１，Ｃ２，Ｃ３，Ｃ４は、低周波成分の通過を阻止するために設けられる。抵抗Ｒ１，Ｒ２は、平衡２線ケーブルＣ１の特性インピーダンスよりも十分に大きいインピーダンス値を有し、分岐点での平衡２線ケーブルＣ１の特性インピーダンスに影響を与えずに、被変調波信号を分岐端子部２ｃに伝達する役目を担う。トランスＴ１は、分岐端子部２ｃ側からみた特性インピーダンスが平衡２線ケーブルＣ１の特性インピーダンスと等しくなるように巻き数比が調整されている。尚、終端となる分岐器２における一方の送り端子部には、コンデンサおよび抵抗からなる終端部材Ｚが接続される。
【００２１】
このように構成される通信システムでは、通信端末１の信号送信部１ｂでデータ信号および搬送波信号から被変調波信号が生成され、２線４線変換回路１ａおよび平衡２線ケーブルＣ２を経由して分岐器２の分岐端子部２ｃに送信される。その送信された被変調波信号は、分岐回路部２ｄを介して一対の送り端子部２ａ，２ｂに伝達され、そこからそれぞれの平衡２線ケーブルＣ１上に送信されて、別の両分岐器２に伝送される。
【００２２】
別の両分岐器２の各々において、一方の送り端子部に入来した上記被変調波信号は、他方の送り端子部からさらに別の分岐器２に伝送されていく。このようにして上記被変調波信号が他の全ての分岐器２に伝送される。
【００２３】
これらの各分岐器２において、一方の送り端子部に入来した上記被変調波信号は、分岐回路部２ｄを介して分岐端子部２ｃに伝達され、そこからその平衡２線ケーブルＣ２上に送信されて、他の通信端末１に送られる。
【００２４】
他の通信端末１では、被変調波信号が伝送信号受信部１ｄで復調され、元のデータ信号に復号される。
【００２５】
要するに、各分岐器２において、分岐端子部２ｃに入った被変調波信号は、一対の送り端子部２ａ，２ｂの各々から出力し、一方の送り端子部に入った被変調波信号は、他方の送り端子部および分岐端子部２ｃから出力し、他方の送り端子部に入った被変調波信号は、一方の送り端子部および分岐端子部２ｃから出力するのである。
【００２６】
かかる通信システムによれば、分岐器２において平衡２線ケーブルＣ１のインピーダンス整合が保たれ、しかも高インピーダンスで被変調波信号が分岐されるので、被変調波信号の分岐点における挿入損失を低減することができ、伝送距離および分岐接続数の両最大値を増加することができる。
【００２７】
（実施形態１）
本実施形態における通信システムの基本構成は、参考例と同様であり、参考例と共通する部分については同一の符号を付して説明を省略し、本実施形態の特徴となる部分についてのみ詳細に説明する。
【００２８】
本実施形態の通信システムは、参考例の通信システムと比較して、通信端末１および分岐器２に代えて、図４および図５に夫々示した、通信端末１Ａおよび分岐器２Ａとを備えた点に特徴がある。
【００２９】
通信端末１Ａは、図４に示すように、２線４線変換回路１ａと、信号送信部１ｂと、送信信号受信部１ｃと、伝送信号受信部１ｄと、信号衝突検出部１ｅと、ＣＰＵ１ｆと、電源部１ｇと、内部電源１ｈと、端子部１ｉとを参考例の通信端末１と同様に備えているほか、通信端末１との相違点として、ＤＣ電源重畳部１ｊとを備えている。
【００３０】
ＤＣ電源重畳部１ｊは、２線４線変換回路１ａと端子部１ｉとの間に介設され、電源部１ｇから直流電力を得て、直下の分岐器２Ａ用にＤＣ電源を確保するための直流電力を端子部１ｉから出力するものである。
【００３１】
分岐器２Ａは、図５に示すように、送り端子部２ａ，２ｂと、分岐端子部２ｃと、分岐回路部２ｄとを参考例の分岐器２と同様に備えているほか、分岐器２との相違点として、第１のハイブリッド回路２ｅと、第２のハイブリッド回路２ｆと、受信信号増幅器２ｇと、送信信号増幅器２ｈと、ＤＣ電源分離部２ｉと、内部電源２ｊとを備えている。
【００３２】
第１，第２のハイブリッド回路２ｅ，２ｆは、夫々の第１の入出力端子部２４，２７から入力された被変調波信号を分配して夫々の第２の入出力端子部２５，２８と第３の入出力端子部２６，２９とから出力し、また夫々の第２，第３の入出力端子部から入力された被変調波信号を混合して夫々の第１の入出力端子部２４，２７から出力する。第１のハイブリッド回路２ｅの第１の入出力端子部２４は、分岐回路部２ｄと分岐端子部２ｃとの間の分岐回路部２ｄ側に接続され、第２のハイブリッド回路２ｆの第１の入出力端子部２７は、分岐回路部２ｄと分岐端子部２ｃとの間の分岐端子部２ｃ側に接続される。夫々のハイブリッド回路の第２の入出力端子部２５，２８間には、送信信号増幅器２ｈが接続され、第３の入出力端子部２６，２９間には、受信信号増幅器２ｇが接続される。
【００３３】
送信信号増幅器２ｈは、分岐端子部２ｃからの被変調波信号を増幅するためのものであり、受信信号増幅器２ｇは、送り端子部２ａ，２ｂからの被変調波信号を増幅するためのものである。
【００３４】
ＤＣ電源分離部２ｉは、第２のハイブリッド回路２ｆと分岐端子部２ｃとの間に接続され、通信端末１Ａからの被変調波信号および直流電力からそれぞれを分離し、被変調波信号を第２のハイブリッド回路２ｆに伝達する一方、直流電力を内部電源２ｊに供給するものである。
【００３５】
内部電源２ｊは、ＤＣ電源分離部２ｉから供給される直流電力により当該分岐器２Ａの各部に必要な電力を供給するものである。
【００３６】
ここで、図６を用いて第１，第２のハイブリッド回路についてさらに詳説する。第１のハイブリッド回路２ｅは、トランスＴ２〜５と抵抗Ｒ３，Ｒ４とからなり、第１の入出力端子部２４の各端子には、並列結合されたトランスＴ２，Ｔ３が接続されている。第２の入出力端子部２５の一方の端子は、トランスＴ４及び抵抗Ｒ３の一端と接続され、第２の入出力端子部２５の他方の端子は、トランスＴ５及び抵抗Ｒ４の一端と接続されている。第３の入出力端子部２６の一方の端子は、トランスＴ４及び抵抗Ｒ３の他端と接続され、第３の入出力端子２６の他方の端子は、トランスＴ５及び抵抗Ｒ４の他端と接続されている。
【００３７】
第２のハイブリッド回路２ｆも同様に、トランスＴ６〜９と抵抗Ｒ５，Ｒ６とからなり、第１の入出力端子部２７の各端子は、並列結合されたトランスＴ８，Ｔ９と接続され、第２の入出力端子部２８の一方の端子はトランスＴ６及び抵抗Ｒ５の一端と、第２の入出力端子部２８の他方の端子はトランスＴ７及び抵抗Ｒ６の一端と、第３の入出力端子部２９の一方の端子はトランスＴ７及び抵抗Ｒ６の他端と、第３の入出力端子部２９の他方の端子はトランスＴ６及び抵抗Ｒ５の他端と夫々接続されている。
【００３８】
ここで抵抗Ｒ３〜Ｒ６は増幅器接続側の出力インピーダンスを決定するための抵抗であると共に、アンバランス分の電力を吸収する。トランスＴ４〜Ｔ７は信号を２つに分配或いは２つの信号を１つに混合させる役割をしている。またトランスＴ２，Ｔ３は第１のハイブリッド回路２ｅの第１の入出力端子部２４の、トランスＴ８，Ｔ９は第２のハイブリッド回路２ｆの第１の入出力端子部２７のインピーダンス整合を取るためのものであり、整合が取れるように巻き数比を夫々調整している。
【００３９】
上記のように構成されたハイブリッド回路において、第１のハイブリッド回路２ｅの第１の入出力端子部２４から入力された被変調波信号は、等しく２つの信号成分に分配され、第２の入出力端子部２５と第３の入出力端子部２６へと出力される。
【００４０】
第３の入出力端子部２６へ出力された信号成分は、順方向に接続された受信信号増幅器２ｇの利得によって増幅され、第２のハイブリッド回路２ｆの第３の入出力端子部２９へ入力される。
【００４１】
一方、第２の入出力端子部２５には、逆方向に接続された送信信号増幅器２ｈが接続されているため、第２の入出力端子部２５から出力された信号成分は、第２のハイブリッド回路２ｆの第２の入出力端子部２８へ透過することはない。
【００４２】
第２のハイブリッド回路２ｆの第３の入出力端子部２９に入力された被変調波信号は、再び第２のハイブリッド回路２ｆを経由して第２のハイブリッド回路２ｆの第１の入出力端子２７から出力される。
【００４３】
この時、第２のハイブリッド回路２ｆの第３の入出力端子部２９と第２の入出力端子部２８との間には、逆結合減衰量が存在するため、第３の入出力端子部２９に入力された信号成分が第２の入出力端子部２８に漏れ出す量は極僅かとなる。ただし、信号の発振を防ぐために、ハイブリッド回路１つ当たりの逆結合減衰量が−Ａ［ｄＢ］の場合、受信信号増幅器２ｇと送信信号増幅器２ｈとの利得合計は２Ａ［ｄＢ］を越えてはならない。
【００４４】
同様に、第２のハイブリッド回路２ｆの第１の入出力端子部２７から入力された被変調波信号は、第２のハイブリッド回路２ｆによって分配され、第２の入出力端子部２８から出力した信号成分が送信信号増幅器２ｈの利得によって増幅された後、第１のハイブリッド回路２ｅの第１の入出力端子部２４から出力される。
【００４５】
かかる通信システムにおいては、分岐器２Ａ内で被変調波信号の双方向増幅が可能となり、通信端末１Ａから送信される被変調波信号を適切なレベルで他の通信端末１Ａに伝送することができると共に、他の通信端末１Ａからの被変調波信号を適切なレベルで受信することができ、参考例よりさらに通信システム全体の伝送距離および分岐接続数の両最大値を増加することができる。
【００４６】
（実施形態２）
本実施形態における通信システムの基本構成は、参考例又は実施形態１と同様であり、それらと共通する部分については同一の符号を付して説明を省略し、本実施形態の特徴となる部分についてのみ詳細に説明する。
【００４７】
本実施形態の通信システムは、参考例の通信端末１に代えて、図７に示した通信端末１Ｂを備えた点に特徴がある。分岐器２の構成は、参考例と同様である。
【００４８】
通信端末１Ｂは、信号送信部１ｂと、送信信号受信部１ｃと、伝送信号受信部１ｄと、信号衝突検出部１ｅと、ＣＰＵ１ｆと、電源部１ｇと、内部電源１ｈと、端子部１ｉとを参考例の通信端末１と同様に備えているほか、通信端末１との相違点として、２線４線変換回路１ａを省いて、ハイブリッド回路１ｋと、送信信号増幅器１ｌと、受信信号増幅器１ｍとを備えている。
【００４９】
ハイブリッド回路１ｋと、送信信号増幅器１ｌと、受信信号増幅器１ｍとは、夫々実施形態１のハイブリッド回路２ｅと送信信号増幅器２ｈと受信信号増幅器２ｇと同様のものであり、本実施形態は、実施形態１のハイブリッド回路２ｅと送信信号増幅器２ｈと受信信号増幅器２ｇとを、分岐器内部から通信端末内部へ移動させたものに相当する。
【００５０】
ハイブリッド回路１ｋの第１の入出力端子部１０は、端子部１ｉに接続され、第２の入出力端子部１１は、送信信号増幅器１ｌの出力端と接続され、第３の入出力端子部１２は、受信信号増幅器１ｍの入力端と接続される。
【００５１】
送信信号増幅器１ｌは、その入力端が抵抗Ｒを介して信号送信部１ｂと接続され、信号送信部１ｂからの被変調波信号を増幅する。受信信号増幅器１ｍは、その出力端が伝送信号受信部１ｄと接続され、端子部１ｉに入来した被変調波信号を増幅して伝送信号受信部１ｄへ入力する。
【００５２】
このように構成される通信システムでは、信号送信部１ｂから送信された被変調波信号は、送信信号増幅器１ｌによって増幅され、ハイブリッド回路１ｋを介して、端子部１ｉから平衡２線ケーブルＣ２上に送信される。
【００５３】
また、平衡２線ケーブルＣ２から端子部１ｉに入来した被変調波信号は、ハイブリッド回路１ｋによって、等しく２つの信号成分に分配され、第２，第３の入出力端子部１１，１２から出力される。第３の入出力端子部１２から出力された信号成分は、順方向に接続された受信信号増幅器１ｍによって増幅された後、伝送信号受信部１ｄへ入力される。一方、第２の入出力端子部１１には逆方向に接続された送信信号増幅器１ｌが接続されているため、第２の入出力端子部１１から出力された信号成分が信号送信部１ｂへ透過することはない。
【００５４】
ここで、送信信号増幅器１ｌと受信信号増幅器１ｍの利得について説明する。信号衝突検出部１ｅは、データ信号の送信中に伝送信号受信部１ｄが受信する信号と送信信号受信部１ｃが受信する自身の送信した信号とを比較し、一致した場合には、平衡２線ケーブルＣ上に伝送されている信号は１つであり信号の衝突は起こっていないと判断し、一致しない場合には、平衡２線ケーブルＣ上に伝送されている信号は複数あり、信号の衝突が起こっていると判断する。よって、衝突検出機能を正常に働かせるためには、送信信号受信部１ｃと伝送信号受信部１ｄとが受信する信号レベルが同一である必要がある。
【００５５】
ここで、信号送信部１ｂと送信信号増幅器１ｌとの間に設置された抵抗Ｒでの減衰量を−ｒ［ｄＢ］、送信信号増幅器１ｌの利得をα［ｄＢ］、受信信号増幅器１ｍの利得をβ［ｄＢ］、ハイブリッド回路１ｋの逆結合減衰量を−Ａ［ｄＢ］とすると、送信信号受信部１ｃが受信する信号のレベルは、信号送信部１ｂが送信した信号のレベルと同じ（０［ｄＢ］）であるが、伝送信号受信部１ｄが受信する信号のレベルは、信号送信部１ｂが送信した信号のレベルに対して利得が−ｒ＋α−Ａ＋β［ｄＢ］となっているため、送信信号受信部１ｃと伝送信号受信部１ｄとで受信する信号のレベルを同一にするためには、−ｒ＋α−Ａ＋β＝０、つまりα＋β＝Ａ＋ｒでなければならない。
【００５６】
則ち、送信信号受信部１ｃと伝送信号受信部１ｄとが受信する信号のレベルを同一にして信号衝突検出部１ｅの衝突検出機能を正常に働かせるためには、送信信号増幅器１ｌと受信信号増幅器１ｍとは、合わせて、ハイブリッド回路１ｋにおける逆結合減衰量分と抵抗Ｒにおける減衰量分だけ信号を増幅させればよい。
【００５７】
尚、抵抗Ｒが無ければ、送信信号増幅器１ｌと受信信号増幅器１ｍとはハイブリッド回路１ｋにおける逆結合減衰量分だけ信号を増幅させればよい。
【００５８】
また、受信信号増幅器１ｍと伝送信号受信部１ｄとの間にアッテネータ（減衰量：−Ｂ［ｄＢ］）を挿入すれば、伝送信号受信部１ｄが受信するデータ信号のレベルは、信号送信部１ｂが送信したデータ信号のレベルに対して利得が−ｒ＋α−Ａ＋β−Ｂ［ｄＢ］となり、α＋β＝ｒ＋Ａ＋Ｂが成り立つように、信号を増幅させればよい。
【００５９】
かかる通信システムにおいては、通信端末は信号衝突検出機能を失わずにデータ信号を増幅して送信することが可能となり、通信システム全体の伝送距離および分岐接続数の両最大値を増加することができる。また、ハイブリッド回路が２線４線変換回路の役割も兼ねることができるので、２線４線変換回路が不要となる。また、実施形態１と比較するとハイブリッド回路が１つで済み、分岐器へＤＣ電源を送信するためのＤＣ電源重畳部、ＤＣ電源とデータ信号とを分離させる電源分離回路も不要となるため、低コスト化を図ることができる。
【００６０】
（実施形態３）
本実施形態における通信システムの基本構成は実施形態２と共通するために共通する部分については同一の符号を付して説明を省略し、本実施形態の特徴となる部分についてのみ詳細に説明する。
【００６１】
本実施形態の通信システムは、実施形態２の通信端末１Ｂに代えて、図８に示した通信端末１Ｃを備えた点に特徴がある。
【００６２】
この通信端末１Ｃは、信号送信部１ｂと、送信信号受信部１ｃと、伝送信号受信部１ｄと、信号衝突検出部１ｅと、ＣＰＵ１ｆと、電源部１ｇと、内部電源１ｈと、端子部１ｉと、ハイブリッド回路１ｋと、送信信号増幅器１ｌとを実施形態２の通信端末１Ｂと同様に備えおり、通信端末１Ｂとの相違点として、受信信号増幅器１ｍを省いて、ハイブリッド回路１ｋの第３の入出力端子１２と伝送信号受信部１ｄとを直接接続した構成となっている。
【００６３】
ただし、本実施形態の送信信号増幅器１ｌの利得は、後述するように、実施形態２の送信信号増幅器１ｌの利得とは異なっている。
【００６４】
実施形態２で述べたように、通信端末の信号衝突検出部１ｅが正常に機能するには、送信信号受信部１ｃと伝送信号受信部１ｄとが受信する信号のレベルが同一である必要があった。よって、本実施形態の通信端末１Ｃでは、送信信号増幅器１ｌのみで、送信する信号をハイブリッド回路１ｋの逆結合減衰量分と抵抗Ｒにおける減衰量分だけ増幅させ、受信する信号は増幅せずに通過させる構成とし、送信信号受信部１ｃと伝送信号受信部１ｄとが受信する信号のレベルを同一に保って信号の衝突検出機能を働かせている。
【００６５】
かかる通信システムにおいては、通信端末は、信号衝突検出機能を失わずに、実施形態２で双方向の増幅器で実現していた利得を１台の送信方向の増幅器で実現したため、送信時に予めノイズに対してレベルの大きいデータ信号を送信することが可能となり、信号対ノイズ比（Ｓ／Ｎ比）が向上し、信頼性の高い高品位のシステムを実現することが可能となる。また、増幅器の数も削減できるため、さらなる低コスト化を図ることができる。
【００６６】
【発明の効果】
請求項１の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成されるので、分岐回路部により高インピーダンスで被変調波信号の分岐を行うことで、分岐点における挿入損失を低減することができ、またトランスを用いて分岐箇所での平衡２線ケーブルと分岐器とのインピーダンス整合を保つことで、平衡２線ケーブル上における被変調波信号の減衰を低減することができるので、被変調波信号の減衰ないしは反射の影響が減少され、衝突検出機能を有した通信システムにおいて、伝送距離および分岐接続数の両最大値を増加することができるという効果がある。また、前記分岐器は、前記送り端子部からの被変調波信号を増幅する受信信号増幅器と、前記分岐端子部からの被変調波信号を増幅する送信信号増幅器と、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し、第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力する２つのハイブリッド回路とを有し、一方の前記ハイブリッド回路の第１の入出力端子を前記分岐回路部と前記分岐端子部との間で前記分岐回路部側に接続し、他方のハイブリッド回路の第１の入出力端子を前記分岐回路部と前記分岐端子部との間で前記分岐端子部側に接続し、２つの前記ハイブリッド回路の第２，第３の入出力端子間を、前記受信信号増幅器と前記送信信号増幅器とで接続したので、分岐器内でデータ信号の双方向増幅が可能となり、さらに伝送距離および分岐接続数の両最大値を増加することができるという効果がある。
【００６８】
請求項２の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成されるので、分岐回路部により高インピーダンスで被変調波信号の分岐を行うことで、分岐点における挿入損失を低減することができ、またトランスを用いて分岐箇所での平衡２線ケーブルと分岐器とのインピーダンス整合を保つことで、平衡２線ケーブル上における被変調波信号の減衰を低減することができるので、被変調波信号の減衰ないしは反射の影響が減少され、衝突検出機能を有した通信システムにおいて、伝送距離および分岐接続数の両最大値を増加することができるという効果がある。また、前記通信端末は、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力するハイブリッド回路を有し、前記ハイブリッド回路の第１の入出力端子を前記平衡２線ケーブルと接続し、前記ハイブリッド回路の第２の入出力端子と前記信号送信部との間に、前記信号送信部からの被変調波信号を増幅する送信信号増幅器を接続し、前記ハイブリッド回路の第３の入出力端子と前記伝送信号受信部との間に、前記平衡２線ケーブルからの被変調波信号を増幅する受信信号増幅器を接続して構成され、前記送信信号増幅器と前記受信信号増幅器は、合わせて、前記ハイブリッド回路における逆結合減衰量分だけ被変調波信号を増幅させるので、通信端末は信号衝突検出機能を失わずにデータ信号を増幅して送信することが可能となり、衝突検出機能を有した通信システム全体の伝送距離および分岐接続数の両最大値を増加することができるという効果がある。
【００６９】
請求項３の発明は、複数の通信端末と、これらの各通信端末に接続される分岐器と、これらの各分岐器間に接続される平衡２線ケーブルとにより構成され、前記複数の通信端末が前記分岐器および前記平衡２線ケーブルを介して相互にデータ信号を送受信する通信システムであって、前記通信端末は、送信するべきデータ信号から被変調波信号を生成し前記平衡２線ケーブルに送信する信号送信部と、その信号送信部が送信した自らの被変調波信号を受信しこれを復調してデータ信号を得る送信信号受信部と、前記平衡２線ケーブルからの被変調波信号を受信しこれを復調してデータ信号を得る伝送信号受信部と、前記送信信号受信部と前記伝送信号受信部とが受信し復調して得られた夫々のデータ信号を比較することにより前記平衡２線ケーブル上のデータ信号の衝突を検出する信号衝突検出部とを備え、前記分岐器は、前記平衡２線ケーブルと接続するための一対の送り端子部と、当該分岐器を前記通信端末に接続するための分岐端子部と、分岐回路部を含み、前記分岐回路部は、前記一対の送り端子部間の両ラインと前記分岐端子部との間に介設され前記平衡２線ケーブルに対してハイインピーダンスとなる一対の抵抗と、これら一対の抵抗と前記分岐端子部との間に介設され前記平衡２線ケーブルとインピーダンス整合をとるためのトランスとにより構成されるので、分岐回路部により高インピーダンスで被変調波信号の分岐を行うことで、分岐点における挿入損失を低減することができ、またトランスを用いて分岐箇所での平衡２線ケーブルと分岐器とのインピーダンス整合を保つことで、平衡２線ケーブル上における被変調波信号の減衰を低減することができるので、被変調波信号の減衰ないしは反射の影響が減少され、衝突検出機能を有した通信システムにおいて、伝送距離および分岐接続数の両最大値を増加することができるという効果がある。また、前記通信端末は、第１の入出力端子から入力された被変調波信号を分配して第２，第３の入出力端子から出力し第２，第３の入出力端子から入力された被変調波信号を混合して前記第１の入出力端子から出力するハイブリッド回路を有し、前記ハイブリッド回路の第１の入出力端子を前記平衡２線ケーブルと接続し、前記ハイブリッド回路の第２の入出力端子と前記信号送信部との間に、前記信号送信部からの被変調波信号を増幅する送信信号増幅器を接続し、前記ハイブリッド回路の第３の入出力端子と前記伝送信号受信部とを接続して構成され、前記送信信号増幅器は、前記ハイブリッド回路における逆結合減衰量分だけ被変調波信号を増幅させるので、信号衝突検出機能を失わずに、送信時に予めノイズに対してレベルの大きいデータ信号を送信でき、信号対ノイズ比（Ｓ／Ｎ比）を向上できるので、より信頼性の高い高品位の通信システムを実現することが可能となり、さらにデータ信号を増幅させる増幅器の台数も削減できるため、低コスト化も図ることができるという効果がある。
【図面の簡単な説明】
【図１】参考例の通信システムのシステム構成を示すブロック図である。
【図２】同上の通信端末の構成を示すブロック図である。
【図３】同上の分岐器の構成を示すブロック図である。
【図４】実施形態１の通信システムの通信端末の構成を示すブロック図である。
【図５】同上の分岐器の構成を示すブロック図である。
【図６】同上の要部を説明する説明図である。
【図７】実施形態２の通信システムの通信端末の構成を示すブロック図である。
【図８】実施形態３の通信システムの通信端末の構成を示すブロック図である。
【図９】従来の通信システムのシステム構成を示すブロック図である。
【符号の説明】
１通信端末
１ａ２線４線変換回路
１ｂ信号送信部
１ｃ送信信号受信部
１ｄ伝送信号受信部
１ｅ信号衝突検出部
１ｆＣＰＵ部
１ｇ電源部
１ｈ内部電源
１ｉ端子部
１ｊＤＣ電源重畳部
１ｋハイブリッド回路
１ｌ送信信号増幅器
１ｍ受信信号増幅器
２分岐器
２ａ，２ｂ送り端子部
２ｃ分岐端子部
２ｄ分岐回路部
２ｅ，２ｆハイブリッド回路
２ｇ受信信号増幅器
２ｈ送信信号増幅器
２ｉＤＣ電源分離部
２ｊ内部電源
Ｃ１，Ｃ２平衡２線ケーブル
Ｚ終端部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication system that transmits and receives data signals.
[0002]
[Prior art]
FIG. 9 is a diagram showing a configuration example of a conventional general communication system. The communication system shown in this figure is composed of a plurality of communication terminals 100 and a balanced two-wire cable (pair line) C that is branched and connected to each of these communication terminals 100, and the plurality of communication terminals 100 are balanced two-wire cables. Data signals are mutually transmitted and received via C.
[0003]
The communication terminal 100 includes a terminal unit 100i for connecting the communication terminal 100 to another communication terminal 100 with a balanced two-wire cable C, a CPU unit 100f that executes various processes such as transmission and reception of data signals, and the like. A signal transmitting unit 100b that generates a modulated wave signal from the data signal to be transmitted from the CPU unit 100f and transmits the modulated wave signal to the other communication terminal 100 from the terminal unit 100i, and its own modulated signal transmitted by the signal transmitting unit 100b A modulated signal from a balanced two-wire cable C that enters a terminal unit 100i and a transmission signal receiving unit 100c that receives a wave signal and outputs a data signal obtained by demodulating the signal to the signal collision detection unit 100e. A transmission signal receiving unit 100d that receives and demodulates the received data signal and outputs the data signal to the CPU unit 100f and the signal collision detection unit 100e; A signal collision detection unit that detects a collision of data signals on the balanced two-wire cable C by comparing the respective data signals received by the transmission unit 100c and the transmission signal reception unit 100d, and a signal transmission unit 100b A two-wire four-wire conversion circuit 100a interposed between the input and the input of the transmission signal receiving unit 100d and the terminal unit 100i, a power source unit 100g for converting AC power of the AC power source into DC power, and the power source unit And an internal power supply 100h that generates driving power from the DC power converted at 100 g and supplies the driving power to each unit.
[0004]
In such a communication system, a modulated wave signal is generated from the data signal and the carrier wave signal by the signal transmission unit 100b of the communication terminal 100, and is transmitted onto the balanced two-wire cable C via the two-wire four-wire conversion circuit 100a. The The transmitted modulated wave signal is received by another communication terminal 100, demodulated by the transmission signal receiving unit 100d, and decoded into the original data signal.
[0005]
Here, with respect to the frequency of the transmission signal on the balanced two-wire cable C, the same frequency band is used for uplink and downlink. The wiring form is multidrop capable of branching at an arbitrary location, and balanced two-wire cables C are directly connected at the branch point.
[0006]
In the case of such a communication method, when a plurality of communication terminals 100 transmit at the same time, the signals transmitted to the balanced two-wire cable C collide, and any communication terminal 100 can normally receive the signal of the communication partner. become unable. For this reason, generally, each communication terminal 100 monitors the data signal received by the transmission signal receiving unit 100d before transmission, so that there is a signal being transmitted on the balanced two-wire cable C. Is supposed to detect. When it is detected that there is a signal being transmitted on the balanced two-wire cable C, the transmission timing is adjusted so that the transmission time is postponed, and the detection is performed again and if there is no signal being transmitted, transmission is performed. Is to be done.
[0007]
In addition, during transmission of the modulated wave signal, the communication device 100 is colliding with a data signal transmitted from another communication device 100, that is, whether the data signal is normally transmitted by the signal collision detection unit 100e. Detect if there is no. That is, when the data signals of the transmission signal receiving unit 100d and the transmission signal receiving unit 100c match, it is determined that there is one signal transmitted on the balanced two-wire cable C and no signal collision occurs. If they do not match, there are a plurality of signals transmitted on the balanced two-wire cable C, and it is determined that a signal collision has occurred. When a collision of data signals is detected, the modulated wave signal being transmitted is stopped, and transmission of the modulated wave signal is attempted again after a certain time.
[0008]
[Problems to be solved by the invention]
However, in the above conventional communication system, although signal transmission and reception can be suitably performed while avoiding signal collision, the cables are directly connected at the branch point x of the balanced two-wire cable C. There is a problem that the impedance of the balanced two-wire cable is lowered at the branch point x, and the modulated wave signal that is a transmission signal is attenuated and reflected. As a result, when the amplitude of the modulated wave signal becomes small and the modulated wave signal has a large distortion, it becomes impossible to demodulate the data signal, and both maximum values of the transmission distance and the number of branch connections are increased. I can't.
[0009]
The present invention has been made in view of the above problems, and its object is to increase both maximum values of transmission distance and the number of branch connections in a communication system having a collision detection function. It is to provide a communication system.
[0010]
[Means for Solving the Problems]
 In order to achieve the above object, the invention of claim 1 includes a plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between these branching devices. A communication system in which the plurality of communication terminals transmit / receive data signals to / from each other via the branching unit and the balanced two-wire cable, wherein the communication terminal receives a modulated wave signal from the data signal to be transmitted A signal transmission unit that generates and transmits to the balanced two-wire cable; a transmission signal reception unit that receives a modulated wave signal transmitted by the signal transmission unit and demodulates the signal; A transmission signal receiving unit that receives a modulated wave signal from a cable and demodulates the signal to obtain a data signal, and each data signal obtained by receiving and demodulating the transmission signal receiving unit and the transmission signal receiving unit Compare A signal collision detection unit for detecting a collision of data signals on the balanced two-wire cable, and the branching unit includes a pair of feed terminal units for connecting to the balanced two-wire cable, and the branching unit. A branch terminal section for connecting to the communication terminal; and a branch circuit section, the branch circuit section being interposed between both lines between the pair of feed terminal sections and the branch terminal section. A pair of resistors having high impedance with respect to the wire cable, and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion.The branching unit receives from the first input / output terminal a reception signal amplifier that amplifies the modulated wave signal from the sending terminal unit, a transmission signal amplifier that amplifies the modulated wave signal from the branch terminal unit, and The modulated wave signal is distributed and output from the second and third input / output terminals, and the modulated wave signal input from the second and third input / output terminals is mixed and the first input / output is mixed. Two hybrid circuits that output from the terminal, and the first input / output terminal of one of the hybrid circuits is connected to the branch circuit unit side between the branch circuit unit and the branch terminal unit, and the other A first input / output terminal of the hybrid circuit is connected to the branch terminal part side between the branch circuit part and the branch terminal part, and between the second and third input / output terminals of the two hybrid circuits, Connected by the reception signal amplifier and the transmission signal amplifier
[0012]
 Claim2The invention ofA plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals include the branching device and the branching device. A communication system for transmitting / receiving data signals to / from each other via a balanced two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; Receiving a modulated wave signal transmitted from the signal transmitting unit and demodulating the modulated signal to obtain a data signal; and receiving the modulated wave signal from the balanced two-wire cable and demodulating it The data on the balanced two-wire cable is obtained by comparing the data signal obtained by receiving and demodulating the transmission signal receiving unit, the transmission signal receiving unit, and the transmission signal receiving unit. A signal collision detection unit for detecting a collision of signals, and the branching unit is a pair of feed terminal units for connecting to the balanced two-wire cable, and a branching terminal for connecting the branching unit to the communication terminal And a branch circuit unit, and the branch circuit unit is interposed between both lines between the pair of feed terminal units and the branch terminal unit, and is a pair having a high impedance with respect to the balanced two-wire cable. And a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion,The communication terminal distributes the modulated wave signal input from the first input / output terminal, outputs the modulated wave signal from the second and third input / output terminals, and inputs the modulated wave signal input from the second and third input / output terminals. A hybrid circuit that mixes and outputs a wave signal from the first input / output terminal, connects the first input / output terminal of the hybrid circuit to the balanced two-wire cable, and outputs a second input of the hybrid circuit. A transmission signal amplifier that amplifies the modulated wave signal from the signal transmission unit is connected between the output terminal and the signal transmission unit, and the third input / output terminal of the hybrid circuit and the transmission signal reception unit And a reception signal amplifier for amplifying the modulated wave signal from the balanced two-wire cable. The transmission signal amplifier and the reception signal amplifier are combined with the amount of inverse coupling attenuation in the hybrid circuit. Only permuted It was assumed for amplifying the wave signal.
[0013]
 Claim3The invention ofA plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals include the branching device and the branching device. A communication system for transmitting / receiving data signals to / from each other via a balanced two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; Receiving a modulated wave signal transmitted from the signal transmitting unit and demodulating the modulated signal to obtain a data signal; and receiving the modulated wave signal from the balanced two-wire cable and demodulating it The data on the balanced two-wire cable is obtained by comparing the data signal obtained by receiving and demodulating the transmission signal receiving unit, the transmission signal receiving unit, and the transmission signal receiving unit. A signal collision detection unit for detecting a collision of signals, and the branching unit is a pair of feed terminal units for connecting to the balanced two-wire cable, and a branching terminal for connecting the branching unit to the communication terminal And a branch circuit unit, and the branch circuit unit is interposed between both lines between the pair of feed terminal units and the branch terminal unit, and is a pair having a high impedance with respect to the balanced two-wire cable. And a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion,The communication terminal distributes the modulated wave signal input from the first input / output terminal, outputs the modulated wave signal from the second and third input / output terminals, and inputs the modulated wave signal input from the second and third input / output terminals. A hybrid circuit that mixes and outputs a wave signal from the first input / output terminal, connects the first input / output terminal of the hybrid circuit to the balanced two-wire cable, and outputs a second input of the hybrid circuit. A transmission signal amplifier for amplifying the modulated wave signal from the signal transmission unit is connected between the output terminal and the signal transmission unit, and the third input / output terminal of the hybrid circuit and the transmission signal reception unit are connected. The transmission signal amplifier is configured to amplify the modulated wave signal by an inverse coupling attenuation amount in the hybrid circuit.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described from the first embodiment to the first embodiment.3 and reference examples related to the embodimentWill be explained by.
(Reference example)
 FIG. 1 shows the present invention.Related reference examplesFIG. 2 is a configuration diagram of a communication terminal in the communication system, and FIG. 3 is a configuration diagram of a branching device in the communication system.
[0015]
 Reference exampleAs shown in FIG. 1, the communication system of FIG. 1 includes a plurality of communication terminals 1, a branching device 2 connected to each of these communication terminals 1, and a balanced two-wire cable C1 connected between these branching devices 2. The plurality of communication terminals 1 transmit / receive data signals to / from each other via the branching device 2 and the balanced two-wire cable C1.
[0016]
As shown in FIG. 2, the communication terminal 1 includes a terminal unit 1 i connected to a branching device 2 (connected to the communication terminal 1) directly below the balanced two-wire cable C 2, and transmission and reception of data signals. A signal for generating a modulated wave signal from the CPU unit 1f that executes various processes such as the above and a data signal to be transmitted from the CPU unit 1f and transmitting the modulated signal to another communication terminal 1 via the branching device 2 directly below A transmission unit 1b, a transmission signal reception unit 1c that receives its own modulated wave signal transmitted by the signal transmission unit 1b, and outputs a data signal obtained by demodulating the signal to the signal collision detection unit 1e, and a terminal unit 1i A transmission signal receiving unit 1d that receives the modulated wave signals from the balanced two-wire cables C1 and C2 coming in and outputs a data signal obtained by demodulating the modulated signal to the CPU unit 1f and the signal collision detection unit 1e; A transmission signal receiver 1c; A signal collision detection unit 1e that detects a collision of data signals on the balanced two-wire cables C1 and C2 by comparing respective data signals received and demodulated by the transmission signal reception unit 1d, and a signal transmission unit A 2-wire 4-wire conversion circuit 1a interposed between the output of 1b and the input of the transmission signal receiving section 1d and the terminal section 1i; a power supply section 1g for converting AC power of the AC power supply into DC power; An internal power supply 1h that generates drive power from the DC power converted by the unit 1g and supplies the drive power to each unit.
[0017]
As shown in FIG. 3, the branching device 2 connects the branching device 2 to the communication terminal 1 via the pair of feed terminal portions 2a and 2b for connecting to the balanced two-wire cable C1 and the balanced two-wire cable C2. In addition to the branch terminal portion 2c, a branch circuit portion 2d is provided.
[0018]
The terminals 20 and 21 of the feed terminal portion 2a and the terminals 22 and 23 of the feed terminal portion 2b are electrically connected to each other inside the branching device 2.
[0019]
The branch circuit unit 2d has less attenuation of the modulated wave signal sent from the other feed terminal unit with respect to the modulated wave signal coming into one feed terminal unit of the pair of feed terminal units 2a and 2b. In this way, the branch points are connected with high impedance, and the impedance of the branch terminal portion 2c is configured to be equal to the characteristic impedance of the transmission line of the modulated wave signal. That is, a pair of resistors R1 and R2 that are interposed between both lines LN1 and LN2 between the pair of feed terminal portions 2a and 2b and the branch terminal portion 2c and have high impedance with respect to the balanced two-wire cable C1, A pair of capacitors C1 and C2 interposed in series between these resistors R1 and R2 and both lines LN1 and LN2, and a balanced 2 between the pair of resistors R1 and R2 and the branch terminal portion 2c. A transformer T1 for impedance matching with the line cable C2 and a pair of capacitors C3 and C4 interposed between the transformer T1 and the branch terminal portion 2c.
[0020]
Capacitors C1, C2, C3, and C4 are provided to prevent passage of low frequency components. The resistors R1 and R2 have an impedance value sufficiently larger than the characteristic impedance of the balanced two-wire cable C1, and branch the modulated wave signal without affecting the characteristic impedance of the balanced two-wire cable C1 at the branch point. It plays a role of transmitting to the terminal portion 2c. The transformer T1 has a winding ratio adjusted so that the characteristic impedance seen from the branch terminal portion 2c side is equal to the characteristic impedance of the balanced two-wire cable C1. In addition, the termination | terminus member Z which consists of a capacitor | condenser and resistance is connected to one sending terminal part in the branching device 2 used as the termination | terminus.
[0021]
In the communication system configured as described above, a modulated wave signal is generated from the data signal and the carrier wave signal by the signal transmission unit 1b of the communication terminal 1, and the signal is transmitted via the 2-wire 4-wire conversion circuit 1a and the balanced 2-wire cable C2. It is transmitted to the branch terminal 2c of the branching device 2. The transmitted modulated wave signal is transmitted to the pair of sending terminal portions 2a and 2b via the branch circuit portion 2d, and is transmitted from there to each balanced two-wire cable C1 to be separated into the other two branching devices 2. Is transmitted.
[0022]
In each of the other branching devices 2, the modulated wave signal that has entered one of the sending terminal portions is transmitted from the other sending terminal portion to another branching device 2. In this way, the modulated wave signal is transmitted to all other branching devices 2.
[0023]
In each of these branching devices 2, the modulated wave signal that has entered one of the sending terminal units is transmitted to the branching terminal unit 2c via the branching circuit unit 2d, and transmitted from there to the balanced two-wire cable C2. And sent to another communication terminal 1.
[0024]
In the other communication terminal 1, the modulated wave signal is demodulated by the transmission signal receiving unit 1d and decoded into the original data signal.
[0025]
In short, in each branching device 2, the modulated wave signal entering the branch terminal portion 2c is output from each of the pair of feed terminal portions 2a and 2b, and the modulated wave signal entering one feed terminal portion is the other. The modulated wave signal output from the feed terminal portion and the branch terminal portion 2c and into the other feed terminal portion is output from the one feed terminal portion and the branch terminal portion 2c.
[0026]
According to such a communication system, the impedance matching of the balanced two-wire cable C1 is maintained in the branching device 2, and the modulated wave signal is branched with a high impedance, so that the insertion loss at the branch point of the modulated wave signal is reduced. It is possible to increase both the maximum values of the transmission distance and the number of branch connections.
[0027]
 (Embodiment1)
 The basic configuration of the communication system in this embodiment is as follows:Reference exampleAndReference exampleThe same reference numerals are given to the common parts, and the description thereof will be omitted, and only the parts that are characteristic of this embodiment will be described in detail.
[0028]
 The communication system of this embodiment isReference exampleCompared with the above communication system, the communication terminal 1 and the branching device 2 are replaced by the communication terminal 1A and the branching device 2A shown in FIGS. 4 and 5, respectively.
[0029]
 As shown in FIG. 4, the communication terminal 1A includes a 2-wire 4-wire conversion circuit 1a, a signal transmission unit 1b, a transmission signal reception unit 1c, a transmission signal reception unit 1d, a signal collision detection unit 1e, and a CPU 1f. The power supply unit 1g, the internal power supply 1h, and the terminal unit 1iReference exampleThe communication terminal 1 includes a DC power supply superimposing unit 1j as a difference from the communication terminal 1.
[0030]
The DC power supply superimposing unit 1j is interposed between the 2-wire 4-wire conversion circuit 1a and the terminal unit 1i, and obtains DC power from the power supply unit 1g to secure a DC power supply for the branching device 2A directly below. DC power is output from the terminal portion 1i.
[0031]
 As shown in FIG. 5, the branching device 2A includes sending terminal portions 2a and 2b, a branching terminal portion 2c, and a branching circuit portion 2d.Reference exampleThe difference from the branching device 2 is that the first hybrid circuit 2e, the second hybrid circuit 2f, the reception signal amplifier 2g, the transmission signal amplifier 2h, and the DC A power supply separation unit 2i and an internal power supply 2j are provided.
[0032]
The first and second hybrid circuits 2e and 2f distribute the modulated wave signals input from the first input / output terminal portions 24 and 27, respectively, and the second input / output terminal portions 25 and 28 respectively. The first input / output terminal sections 24 are mixed with the modulated wave signals output from the third input / output terminal sections 26 and 29 and input from the second and third input / output terminal sections. , 27. The first input / output terminal unit 24 of the first hybrid circuit 2e is connected to the branch circuit unit 2d side between the branch circuit unit 2d and the branch terminal unit 2c, and the first input / output terminal unit 24 of the second hybrid circuit 2f is connected to the first input / output terminal unit 24c. The output terminal portion 27 is connected to the branch terminal portion 2c side between the branch circuit portion 2d and the branch terminal portion 2c. A transmission signal amplifier 2h is connected between the second input / output terminal portions 25 and 28 of each hybrid circuit, and a reception signal amplifier 2g is connected between the third input / output terminal portions 26 and 29.
[0033]
The transmission signal amplifier 2h is for amplifying the modulated wave signal from the branch terminal section 2c, and the reception signal amplifier 2g is for amplifying the modulated wave signal from the transmission terminal sections 2a and 2b. is there.
[0034]
The DC power source separation unit 2i is connected between the second hybrid circuit 2f and the branch terminal unit 2c, separates each of the modulated wave signal and the DC power from the communication terminal 1A, and outputs the modulated wave signal to the second Is transmitted to the hybrid circuit 2f, and DC power is supplied to the internal power source 2j.
[0035]
The internal power supply 2j supplies necessary power to each part of the branching device 2A by direct current power supplied from the DC power supply separation unit 2i.
[0036]
Here, the first and second hybrid circuits will be further described in detail with reference to FIG. The first hybrid circuit 2 e includes transformers T 2 to T 5 and resistors R 3 and R 4. Transformers T 2 and T 3 coupled in parallel are connected to each terminal of the first input / output terminal unit 24. One terminal of the second input / output terminal portion 25 is connected to one end of the transformer T4 and the resistor R3, and the other terminal of the second input / output terminal portion 25 is connected to one end of the transformer T5 and the resistor R4. Yes. One terminal of the third input / output terminal portion 26 is connected to the other end of the transformer T4 and the resistor R3, and the other terminal of the third input / output terminal 26 is connected to the other end of the transformer T5 and the resistor R4. ing.
[0037]
Similarly, the second hybrid circuit 2f includes transformers T6 to T9 and resistors R5 and R6. Each terminal of the first input / output terminal unit 27 is connected to the transformers T8 and T9 coupled in parallel. One terminal of the input / output terminal section 28 is one end of the transformer T6 and the resistor R5, the other terminal of the second input / output terminal section 28 is one end of the transformer T7 and the resistor R6, and the third input / output terminal section 29. Is connected to the other end of the transformer T7 and the resistor R6, and the other terminal of the third input / output terminal portion 29 is connected to the other end of the transformer T6 and the resistor R5.
[0038]
Here, the resistors R3 to R6 are resistors for determining the output impedance on the amplifier connection side and absorb unbalanced power. The transformers T4 to T7 serve to distribute the signal into two or to mix the two signals into one. Transformers T2 and T3 are for impedance matching of the first input / output terminal portion 24 of the first hybrid circuit 2e, and transformers T8 and T9 are for impedance matching of the first input / output terminal portion 27 of the second hybrid circuit 2f. Therefore, the winding ratio is adjusted to achieve matching.
[0039]
In the hybrid circuit configured as described above, the modulated wave signal input from the first input / output terminal portion 24 of the first hybrid circuit 2e is equally distributed to two signal components, and the second input / output The data is output to the terminal unit 25 and the third input / output terminal unit 26.
[0040]
The signal component output to the third input / output terminal section 26 is amplified by the gain of the reception signal amplifier 2g connected in the forward direction, and input to the third input / output terminal section 29 of the second hybrid circuit 2f. The
[0041]
On the other hand, since the transmission signal amplifier 2h connected in the reverse direction is connected to the second input / output terminal section 25, the signal component output from the second input / output terminal section 25 is the second hybrid. There is no transmission to the second input / output terminal portion 28 of the circuit 2f.
[0042]
The modulated wave signal input to the third input / output terminal portion 29 of the second hybrid circuit 2f passes through the second hybrid circuit 2f again and passes through the first input / output terminal 27 of the second hybrid circuit 2f. Is output from.
[0043]
At this time, since there is a reverse coupling attenuation amount between the third input / output terminal portion 29 and the second input / output terminal portion 28 of the second hybrid circuit 2f, the third input / output terminal portion 29 is provided. The amount of the signal component input to is leaked to the second input / output terminal portion 28 is extremely small. However, in order to prevent signal oscillation, when the reverse coupling attenuation amount per hybrid circuit is −A [dB], the total gain of the reception signal amplifier 2g and the transmission signal amplifier 2h does not exceed 2A [dB]. Don't be.
[0044]
Similarly, the modulated wave signal input from the first input / output terminal portion 27 of the second hybrid circuit 2f is distributed by the second hybrid circuit 2f and output from the second input / output terminal portion 28. After the component is amplified by the gain of the transmission signal amplifier 2h, it is output from the first input / output terminal portion 24 of the first hybrid circuit 2e.
[0045]
 In such a communication system, the modulated wave signal can be bi-directionally amplified in the branching device 2A, and the modulated wave signal transmitted from the communication terminal 1A can be transmitted to another communication terminal 1A at an appropriate level. In addition, the modulated wave signal from the other communication terminal 1A can be received at an appropriate level,Reference exampleFurthermore, both maximum values of the transmission distance and the number of branch connections of the entire communication system can be increased.
[0046]
 (Embodiment2)
 The basic configuration of the communication system in this embodiment is as follows:Reference exampleOr embodiment1The same reference numerals are given to the portions common to them, and the description thereof is omitted, and only the portions that characterize the present embodiment will be described in detail.
[0047]
 The communication system of this embodiment isReference exampleInstead of the communication terminal 1, the communication terminal 1B shown in FIG. 7 is provided. The structure of the branching device 2 isReference exampleIt is the same.
[0048]
 The communication terminal 1B includes a signal transmission unit 1b, a transmission signal reception unit 1c, a transmission signal reception unit 1d, a signal collision detection unit 1e, a CPU 1f, a power supply unit 1g, an internal power supply 1h, and a terminal unit 1i.Reference exampleThe communication terminal 1 includes a hybrid circuit 1k, a transmission signal amplifier 1l, and a reception signal amplifier 1m, except that the two-wire / four-wire conversion circuit 1a is omitted. ing.
[0049]
 The hybrid circuit 1k, the transmission signal amplifier 1l, and the reception signal amplifier 1m are each an embodiment.1The hybrid circuit 2e, the transmission signal amplifier 2h, and the reception signal amplifier 2g are the same as those in the first embodiment.1This corresponds to the hybrid circuit 2e, the transmission signal amplifier 2h, and the reception signal amplifier 2g that are moved from the branching unit to the communication terminal.
[0050]
The first input / output terminal unit 10 of the hybrid circuit 1k is connected to the terminal unit 1i, the second input / output terminal unit 11 is connected to the output terminal of the transmission signal amplifier 1l, and the third input / output terminal unit 12 is connected. Is connected to the input terminal of the reception signal amplifier 1m.
[0051]
The input end of the transmission signal amplifier 11 is connected to the signal transmission unit 1b via the resistor R, and amplifies the modulated wave signal from the signal transmission unit 1b. The output end of the reception signal amplifier 1m is connected to the transmission signal reception unit 1d, amplifies the modulated wave signal that has entered the terminal unit 1i, and inputs the amplified signal to the transmission signal reception unit 1d.
[0052]
In the communication system configured as described above, the modulated wave signal transmitted from the signal transmission unit 1b is amplified by the transmission signal amplifier 11 and is passed from the terminal unit 1i to the balanced two-wire cable C2 via the hybrid circuit 1k. Sent.
[0053]
Further, the modulated wave signal that enters the terminal unit 1i from the balanced two-wire cable C2 is equally distributed to two signal components by the hybrid circuit 1k, and is output from the second and third input / output terminal units 11 and 12. Is done. The signal component output from the third input / output terminal unit 12 is amplified by the reception signal amplifier 1m connected in the forward direction and then input to the transmission signal reception unit 1d. On the other hand, since the transmission signal amplifier 11 connected in the opposite direction is connected to the second input / output terminal unit 11, the signal component output from the second input / output terminal unit 11 is transmitted to the signal transmission unit 1b. Never do.
[0054]
Here, the gains of the transmission signal amplifier 1l and the reception signal amplifier 1m will be described. The signal collision detection unit 1e compares the signal received by the transmission signal receiving unit 1d with the signal transmitted by the transmission signal receiving unit 1c during transmission of the data signal. It is determined that there is only one signal transmitted on the cable C and no signal collision occurs. If they do not match, there are a plurality of signals transmitted on the balanced two-wire cable C, and there is a signal collision. Determine that is happening. Therefore, in order for the collision detection function to work normally, the signal level received by the transmission signal receiving unit 1c and the transmission signal receiving unit 1d needs to be the same.
[0055]
Here, the attenuation amount at the resistor R installed between the signal transmission unit 1b and the transmission signal amplifier 11 is −r [dB], the gain of the transmission signal amplifier 11 is α [dB], and the gain of the reception signal amplifier 1m. Is β [dB] and the reverse coupling attenuation of the hybrid circuit 1k is -A [dB], the level of the signal received by the transmission signal receiving unit 1c is the same as the level of the signal transmitted by the signal transmitting unit 1b (0 [DB]), but the level of the signal received by the transmission signal receiving unit 1d is -r + α-A + β [dB] with respect to the level of the signal transmitted by the signal transmitting unit 1b. In order to make the level of the signal received by the signal receiving unit 1c and the transmission signal receiving unit 1d the same, it must be −r + α−A + β = 0, that is, α + β = A + r.
[0056]
In other words, the transmission signal amplifier 1l and the reception signal amplifier are used in order for the collision detection function of the signal collision detection unit 1e to work normally with the same level of the signal received by the transmission signal reception unit 1c and the transmission signal reception unit 1d. In addition to 1m, the signal may be amplified by an amount corresponding to the reverse coupling attenuation amount in the hybrid circuit 1k and the attenuation amount in the resistor R.
[0057]
If there is no resistor R, the transmission signal amplifier 1l and the reception signal amplifier 1m may amplify the signal by the amount of reverse coupling attenuation in the hybrid circuit 1k.
[0058]
Further, if an attenuator (attenuation amount: -B [dB]) is inserted between the reception signal amplifier 1m and the transmission signal reception unit 1d, the level of the data signal received by the transmission signal reception unit 1d becomes the signal transmission unit 1b. The signal may be amplified so that the gain becomes −r + α−A + β−B [dB] with respect to the level of the data signal transmitted by, and α + β = r + A + B.
[0059]
 In such a communication system, the communication terminal can amplify and transmit the data signal without losing the signal collision detection function, and can increase both the maximum value of the transmission distance and the number of branch connections of the entire communication system. . Further, since the hybrid circuit can also serve as the 2-wire 4-wire conversion circuit, the 2-wire 4-wire conversion circuit becomes unnecessary. Embodiments1Compared with, a single hybrid circuit is sufficient, and a DC power supply superimposing unit for transmitting the DC power to the branching unit and a power supply separation circuit for separating the DC power and the data signal are not required. Can do.
[0060]
 (Embodiment3)
 The basic configuration of the communication system in this embodiment is an embodiment.2Therefore, common parts are denoted by the same reference numerals, description thereof is omitted, and only the characteristic parts of the present embodiment will be described in detail.
[0061]
 The communication system of the present embodiment2Instead of the communication terminal 1B, the communication terminal 1C shown in FIG. 8 is provided.
[0062]
 The communication terminal 1C includes a signal transmission unit 1b, a transmission signal reception unit 1c, a transmission signal reception unit 1d, a signal collision detection unit 1e, a CPU 1f, a power supply unit 1g, an internal power supply 1h, and a terminal unit 1i. Embodiment of hybrid circuit 1k and transmission signal amplifier 1l2The communication terminal 1B has the same configuration as that of the communication terminal 1B, except that the reception signal amplifier 1m is omitted and the third input / output terminal 12 of the hybrid circuit 1k and the transmission signal receiving unit 1d are directly connected. It has become.
[0063]
 However, as will be described later, the gain of the transmission signal amplifier 11 according to the present embodiment2This is different from the gain of the transmission signal amplifier 1l.
[0064]
 Embodiment2As described above, in order for the signal collision detection unit 1e of the communication terminal to function properly, the signal levels received by the transmission signal reception unit 1c and the transmission signal reception unit 1d need to be the same. Therefore, in the communication terminal 1C of the present embodiment, the signal to be transmitted is amplified by the reverse coupling attenuation amount of the hybrid circuit 1k and the attenuation amount in the resistor R only by the transmission signal amplifier 1l, and the received signal is not amplified. The transmission signal receiving unit 1c and the transmission signal receiving unit 1d receive signals at the same level to make the signal collision detection function work.
[0065]
 In such a communication system, the communication terminal can perform the embodiment without losing the signal collision detection function.2Since the gain realized by the bidirectional amplifier is realized by the amplifier in one transmission direction, it becomes possible to transmit a data signal having a high level with respect to noise in advance at the time of transmission, and the signal-to-noise ratio (S / N ratio) is improved, and a high-quality system with high reliability can be realized. Further, since the number of amplifiers can be reduced, further cost reduction can be achieved.
[0066]
【The invention's effect】
 The invention of claim 1 comprises a plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices. Is a communication system for transmitting / receiving data signals to / from each other via the branching device and the balanced two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable. A signal transmission unit to transmit, a transmission signal reception unit that receives and modulates its own modulated wave signal transmitted by the signal transmission unit, and a modulated wave signal from the balanced two-wire cable. The balanced signal 2 is obtained by comparing the data signal obtained by receiving and demodulating the transmission signal receiving unit that receives and demodulates the data to obtain the data signal and the transmission signal receiving unit and the transmission signal receiving unit. Line A signal collision detection unit that detects a collision of data signals on the cable, and the branching unit connects a pair of feed terminal units for connection to the balanced two-wire cable and the branching unit to the communication terminal. And a branch circuit unit, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, the branch circuit unit being high with respect to the balanced two-wire cable. Since it is composed of a pair of resistors that become impedance, and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, the branch circuit portion has a high impedance. By branching the modulated wave signal at, the insertion loss at the branch point can be reduced, and the impedance of the balanced two-wire cable and branch at the branch point using a transformer By maintaining the connection, the attenuation of the modulated wave signal on the balanced two-wire cable can be reduced, so that the influence of the attenuation or reflection of the modulated wave signal is reduced, and in a communication system having a collision detection function, There is an effect that both the maximum values of the transmission distance and the number of branch connections can be increased.The branching unit includes a reception signal amplifier that amplifies the modulated wave signal from the sending terminal unit, a transmission signal amplifier that amplifies the modulated wave signal from the branch terminal unit, and a first input / output terminal. The input modulated wave signal is distributed and output from the second and third input / output terminals, and the modulated wave signal input from the second and third input / output terminals is mixed and the first input signal is mixed. Two hybrid circuits that output from the output terminal, and the first input / output terminal of one of the hybrid circuits is connected to the branch circuit unit side between the branch circuit unit and the branch terminal unit, and the other The first input / output terminal of the hybrid circuit is connected to the branch terminal part side between the branch circuit part and the branch terminal part, and between the second and third input / output terminals of the two hybrid circuits. Connected between the reception signal amplifier and the transmission signal amplifier Since, enables bidirectional amplification of the data signal in the splitter, there is an effect that it is possible to increase the further transmission distances and both the maximum value of the branch connections.
[0068]
 Claim2The invention ofA plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals are connected to the branching device and the balanced A communication system that transmits and receives data signals to and from each other via a two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; The signal transmitter receives its own modulated wave signal transmitted and demodulates it to obtain a data signal, and receives and demodulates the modulated wave signal from the balanced two-wire cable. A transmission signal receiving unit that obtains a data signal, and the transmission signal receiving unit and the transmission signal receiving unit receive and demodulate the data signals obtained and demodulated to compare the data signals on the balanced two-wire cable. A signal collision detecting unit for detecting a collision of the two-way cable, the branching unit being connected to the balanced two-wire cable, and a branching terminal unit for connecting the branching unit to the communication terminal A pair of branch circuit units, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, and having a pair of high impedance with respect to the balanced two-wire cable Since it comprises a resistor and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, a modulated wave signal with high impedance by the branch circuit portion By performing the branching, the insertion loss at the branching point can be reduced, and the impedance matching between the balanced two-wire cable and the branching device at the branching point is maintained using a transformer. Since the attenuation of the modulated wave signal on the two-wire cable can be reduced, the influence of the attenuation or reflection of the modulated wave signal is reduced. In a communication system having a collision detection function, the transmission distance and the number of branch connections There is an effect that both of the maximum values can be increased. Also,The communication terminal distributes the modulated wave signal input from the first input / output terminal, outputs the modulated wave signal from the second and third input / output terminals, and inputs the modulated wave signal input from the second and third input / output terminals. A hybrid circuit that mixes and outputs a wave signal from the first input / output terminal, connects the first input / output terminal of the hybrid circuit to the balanced two-wire cable, and outputs a second input of the hybrid circuit. A transmission signal amplifier that amplifies the modulated wave signal from the signal transmission unit is connected between the output terminal and the signal transmission unit, and the third input / output terminal of the hybrid circuit and the transmission signal reception unit And a reception signal amplifier for amplifying the modulated wave signal from the balanced two-wire cable. The transmission signal amplifier and the reception signal amplifier are combined with the amount of inverse coupling attenuation in the hybrid circuit. Only permuted Since the wave signal is amplified, the communication terminal can amplify and transmit the data signal without losing the signal collision detection function, and both the transmission distance and the number of branch connections of the entire communication system having the collision detection function can be maximized. There is an effect that the value can be increased.
[0069]
 Claim3The invention ofA plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals are connected to the branching device and the balanced A communication system that transmits and receives data signals to and from each other via a two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; The signal transmitter receives its own modulated wave signal transmitted and demodulates it to obtain a data signal, and receives and demodulates the modulated wave signal from the balanced two-wire cable. A transmission signal receiving unit that obtains a data signal, and the transmission signal receiving unit and the transmission signal receiving unit receive and demodulate the data signals obtained and demodulated to compare the data signals on the balanced two-wire cable. A signal collision detecting unit for detecting a collision of the two-way cable, the branching unit being connected to the balanced two-wire cable, and a branching terminal unit for connecting the branching unit to the communication terminal A pair of branch circuit units, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, and having a pair of high impedance with respect to the balanced two-wire cable Since it comprises a resistor and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, a modulated wave signal with high impedance by the branch circuit portion By performing the branching, the insertion loss at the branching point can be reduced, and the impedance matching between the balanced two-wire cable and the branching device at the branching point is maintained using a transformer. Since the attenuation of the modulated wave signal on the two-wire cable can be reduced, the influence of the attenuation or reflection of the modulated wave signal is reduced. In a communication system having a collision detection function, the transmission distance and the number of branch connections There is an effect that both of the maximum values can be increased. Also,The communication terminal distributes the modulated wave signal input from the first input / output terminal, outputs the modulated wave signal from the second and third input / output terminals, and inputs the modulated wave signal input from the second and third input / output terminals. A hybrid circuit that mixes and outputs a wave signal from the first input / output terminal, connects the first input / output terminal of the hybrid circuit to the balanced two-wire cable, and outputs a second input of the hybrid circuit. A transmission signal amplifier for amplifying the modulated wave signal from the signal transmission unit is connected between the output terminal and the signal transmission unit, and the third input / output terminal of the hybrid circuit and the transmission signal reception unit are connected. Since the transmission signal amplifier amplifies the modulated wave signal by the inverse coupling attenuation amount in the hybrid circuit, the signal collision detection function is not lost, and the level is high with respect to noise in advance during transmission. data Signal can be transmitted and the signal-to-noise ratio (S / N ratio) can be improved, so that a more reliable and high-quality communication system can be realized, and the number of amplifiers that amplify data signals can be reduced. Therefore, there is an effect that the cost can be reduced.
[Brief description of the drawings]
[Figure 1]Reference exampleIt is a block diagram which shows the system configuration | structure of a communication system.
FIG. 2 is a block diagram showing a configuration of a communication terminal same as above.
FIG. 3 is a block diagram showing a configuration of a branching device same as above.
FIG. 4 Embodiment1It is a block diagram which shows the structure of the communication terminal of the communication system.
FIG. 5 is a block diagram showing the configuration of the branching device according to the above.
FIG. 6 is an explanatory diagram for explaining a main part of the above.
FIG. 72It is a block diagram which shows the structure of the communication terminal of the communication system.
FIG. 83It is a block diagram which shows the structure of the communication terminal of the communication system.
FIG. 9 is a block diagram showing a system configuration of a conventional communication system.
[Explanation of symbols]
1 Communication terminal
1a 2-wire 4-wire conversion circuit
1b Signal transmitter
1c Transmission signal receiver
1d Transmission signal receiver
1e Signal collision detector
1f CPU section
1g power supply
1h Internal power supply
1i terminal
1j DC power supply superimposing section
1k hybrid circuit
1l Transmitter signal amplifier
1m reception signal amplifier
2 turnout
2a, 2b Feed terminal
2c Branch terminal
2d branch circuit
2e, 2f hybrid circuit
2g Receive signal amplifier
2h Transmission signal amplifier
2i DC power supply separation unit
2j Internal power supply
C1, C2 balanced 2-wire cable
Z end member

Claims

A plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals are connected to the branching device and the balanced A communication system that transmits and receives data signals to and from each other via a two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; The signal transmitter receives its own modulated wave signal transmitted and demodulates it to obtain a data signal, and receives and demodulates the modulated wave signal from the balanced two-wire cable. A transmission signal receiving unit that obtains a data signal, and the transmission signal receiving unit and the transmission signal receiving unit receive and demodulate the data signals obtained and demodulated to compare the data signals on the balanced two-wire cable. A signal collision detecting unit for detecting a collision of the two-way cable, the branching unit being connected to the balanced two-wire cable, and a branching terminal unit for connecting the branching unit to the communication terminal A pair of branch circuit units, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, and having a pair of high impedance with respect to the balanced two-wire cable A pair of resistors and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, and the branching device is modulated from the feed terminal portion. A reception signal amplifier for amplifying a wave signal; a transmission signal amplifier for amplifying a modulated wave signal from the branch terminal; and a modulated wave signal input from a first input / output terminal to distribute the second and second 3 input / output terminals And the two hybrid circuits that mix the modulated wave signals input from the second and third input / output terminals and output from the first input / output terminal. A first input / output terminal is connected to the branch circuit section side between the branch circuit section and the branch terminal section, and a first input / output terminal of the other hybrid circuit is connected to the branch circuit section and the branch terminal section. And the second and third input / output terminals of the two hybrid circuits are connected by the reception signal amplifier and the transmission signal amplifier. system.

A plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals are connected to the branching device and the balanced A communication system that transmits and receives data signals to and from each other via a two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; The signal transmitter receives its own modulated wave signal transmitted and demodulates it to obtain a data signal, and receives and demodulates the modulated wave signal from the balanced two-wire cable. A transmission signal receiving unit that obtains a data signal, and the transmission signal receiving unit and the transmission signal receiving unit receive and demodulate the data signals obtained and demodulated to compare the data signals on the balanced two-wire cable. A signal collision detecting unit for detecting a collision of the two-way cable, the branching unit being connected to the balanced two-wire cable, and a branching terminal unit for connecting the branching unit to the communication terminal A pair of branch circuit units, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, and having a pair of high impedance with respect to the balanced two-wire cable A resistor, and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, and the communication terminal receives an input from a first input / output terminal. The modulated wave signal is distributed and output from the second and third input / output terminals, and the modulated wave signal input from the second and third input / output terminals is mixed to the first input / output terminal. the Ruha hybrid circuits be output from the And, the first input-output terminal of the hybrid circuit connected to said balanced two-wire cable, between the second input terminal and the signal transmitting unit of the hybrid circuit, the modulated from the signal transmission unit A reception signal amplifier for amplifying a modulated wave signal from the balanced two-wire cable between a third input / output terminal of the hybrid circuit and the transmission signal receiving unit; is constructed by connecting the received signal amplifier and the transmission signal amplifier, together, communication system that is characterized in that only the reverse coupling attenuation amount to amplify the modulated wave signal in the hybrid circuit.

A plurality of communication terminals, a branching device connected to each of these communication terminals, and a balanced two-wire cable connected between each of these branching devices, wherein the plurality of communication terminals are connected to the branching device and the balanced A communication system that transmits and receives data signals to and from each other via a two-wire cable, wherein the communication terminal generates a modulated wave signal from the data signal to be transmitted and transmits the modulated wave signal to the balanced two-wire cable; The signal transmitter receives its own modulated wave signal transmitted and demodulates it to obtain a data signal, and receives and demodulates the modulated wave signal from the balanced two-wire cable. A transmission signal receiving unit that obtains a data signal, and the transmission signal receiving unit and the transmission signal receiving unit receive and demodulate the data signals obtained and demodulated to compare the data signals on the balanced two-wire cable. A signal collision detecting unit for detecting a collision of the two-way cable, the branching unit being connected to the balanced two-wire cable, and a branching terminal unit for connecting the branching unit to the communication terminal A pair of branch circuit units, the branch circuit unit being interposed between both lines between the pair of feed terminal units and the branch terminal unit, and having a pair of high impedance with respect to the balanced two-wire cable A resistor, and a transformer for impedance matching with the balanced two-wire cable interposed between the pair of resistors and the branch terminal portion, and the communication terminal receives an input from a first input / output terminal. The modulated wave signal is distributed and output from the second and third input / output terminals, and the modulated wave signal input from the second and third input / output terminals is mixed to the first input / output terminal. Hybrid circuit output from The first input / output terminal of the hybrid circuit is connected to the balanced two-wire cable, and the modulated signal from the signal transmission unit is provided between the second input / output terminal of the hybrid circuit and the signal transmission unit. A transmission signal amplifier for amplifying a wave signal, and a third input / output terminal of the hybrid circuit and the transmission signal receiving unit are connected, and the transmission signal amplifier has an inverse coupling attenuation amount in the hybrid circuit amount corresponding communication system that is characterized in that to amplify the modulated wave signal.