JP4041697B2

JP4041697B2 - Broadcast signal retransmission system for mobile

Info

Publication number: JP4041697B2
Application number: JP2002159756A
Authority: JP
Inventors: 敏博杉浦; 清貴大山
Original assignee: Maspro Denkoh Corp
Current assignee: Maspro Denkoh Corp
Priority date: 2002-05-31
Filing date: 2002-05-31
Publication date: 2008-01-30
Anticipated expiration: 2022-05-31
Also published as: JP2004007219A

Description

【０００１】
【発明の属する技術分野】
本発明は、テレビ等の放送信号を受信し、その受信した放送信号を移動体の走行路に向けて再送信する移動体用放送信号再送信システムに関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
自動車や列車等の移動体において、テレビ放送を視聴できるようにするには、移動体に、放送局からの放送電波を受信するための受信アンテナや、この受信アンテナにて受信された放送信号の中から所望チャンネルの放送信号を選局して復調するチューナを設けるようにすればよい。
【０００３】
しかしながら、このように、移動体に設けた受信アンテナにて、放送局からの放送電波を直接受信するようにした場合、移動体の移動時には、走行路周囲の環境変化等によって受信アンテナにて得られる放送信号の受信レベルが変動することから、テレビ放送を良好に視聴できなくなるといった問題があった。また、この場合、移動体がトンネル内等の放送電波が届かない場所を走行している際には、放送信号を受信できないことから、移動体でのテレビ放送の視聴は不可能になる、という問題もある。
【０００４】
また、上記のように移動体に設けた受信アンテナにて放送局からの放送電波を直接受信するようにした場合、移動体が長距離走行中には、移動体の移動に伴い受信アンテナにて放送電波を受信可能な放送局が変化することから、移動体の移動に応じて、チューナにて選局する放送信号のチャンネルを切り換えなければならず、その選局のための操作が面倒であるという問題もある。
【０００５】
本発明は、こうした問題に鑑みなされたものであり、テレビ放送等の各種放送信号を移動体の走行路に向けて再送信する移動体用放送信号再送信システムを提供することで、走行路を走行中の移動体にて所望の放送を安定して選局・復調できるようにすることを目的とする。
【０００６】
【課題を解決するための手段】
かかる目的を達成するためになされた本発明（請求項１〜９）の移動体用放送信号再送信システムにおいては、受信手段にて受信された放送信号を、伝送手段を介して出力手段まで伝送し、出力手段が、その放送信号を、移動体の走行路に沿って敷設された漏洩同軸ケーブルに出力することで、漏洩同軸ケーブルから走行路に向けて放送信号を無線にて送信させる。
【０００７】
つまり、本発明の移動体用放送信号再送信システムは、従来より列車無線等で使用されている漏洩同軸ケーブルを利用することで、放送信号を移動体の走行路に沿って伝送しつつ、その走行路を走行する移動体に対して、放送信号を無線にて配信するようにされている。
【０００８】
このため、本発明によれば、移動体の走行路が放送局からの放送電波が届き難い場所にあっても、或いは、その走行路がトンネル内であっても、その走行路に沿って漏洩同軸ケーブルを敷設することにより、その走行路を走行する移動体に対して、放送信号を常時安定して配信することができるようになり、その走行路を走行する移動体側では、漏洩同軸ケーブルから放射される放送信号の電波を受信し、復調することで、所望チャンネルの放送信号を安定して選局・復調できることになる。
【０００９】
また、本発明の移動体用放送信号再送信システムでは、受信手段にて受信された放送信号を漏洩同軸ケーブルに流すことから、その漏洩同軸ケーブルが敷設された走行路の距離が長く、その走行路が複数の放送局のサービスエリアに跨る場合であっても、漏洩同軸ケーブルからは、受信手段が設置された地域の放送局からの放送信号が再送信されることになる。
【００１０】
例えば、漏洩同軸ケーブルが、東京から大阪に至る移動体の走行路（例えば新幹線等の列車の線路或いは高速道路）に沿って敷設されている場合、その走行路は、東京付近では関東地方の放送局のサービスエリアに属し、大阪付近では関西地方の放送局のサービスエリアに属し、東京と大阪との間の名古屋付近では、東海地方の放送局のサービスエリアに属すことになるが、このような場合であっても、受信手段が関東地方に設置されている場合には、漏洩同軸ケーブルが敷設された走行路全域で、関東地方の放送信号が再送信され、受信手段が関西地方に設置されている場合には、漏洩同軸ケーブルが敷設された走行路全域で、関西地方の放送信号が再送信される。
【００１１】
このため、本発明によれば、漏洩同軸ケーブルが敷設された走行路全域で同一チャンネルの放送信号を受信することができるようになり、この走行路を走行する移動体側では、所望チャンネルの放送信号を選局・復調するために、移動体の走行中に放送信号の選局チャンネルを切り換える必要がない。
【００１２】
ところで、本発明のように、走行路に敷設された漏洩同軸ケーブルを利用して放送信号を再送信する場合、一本の漏洩同軸ケーブルで放送信号を再送信し得る距離には限界があり、列車無線等で実用化されている現在の漏洩同軸ケーブルでは、例えば１ｋｍ〜２ｋｍと、極めて短い。
【００１３】
そこで、請求項１〜６、９に記載の移動体用放送信号再送信システムにおいては、放送信号を再送信可能な長さの漏洩同軸ケーブルを、移動体の走行路に沿って、複数連続的に敷設し、出力手段を、その複数の漏洩同軸ケーブルに対応して、走行路に沿って複数分散して配置し、伝送手段が、受信手段にて受信された放送信号を、その複数の出力手段に夫々伝送するように構成されている。
【００１４】
また、このように、受信手段にて受信された放送信号を複数の出力手段に伝送する場合、伝送手段を、各出力手段専用の伝送路を介して、受信手段から各出力手段に直接放送信号を伝送するように構成してもよいが、このように構成すると、移動体の走行路が長くなって、その走行路に分散配置される出力手段の数が増えるに従い、受信手段から出力手段まで放送信号を伝送する伝送路の数や放送信号伝送用の機器が増えてしまい、当該移動体用放送信号再送信システムのコストアップを招くことになる。
【００１５】
つまり、一般的なＣＡＴＶシステムのように、導電線からなる電気伝送路（一般に同軸ケーブル）を利用して、放送信号を電気信号の状態で伝送する場合、その伝送可能距離は、放送信号の伝送ロスを補償する増幅装置を利用しても、数ｋｍであるため、受信手段との間の距離がこの伝送可能距離（数ｋｍ）を越える出力手段に対しては、伝送ロスの少ない光信号を利用する必要があるが、上記のように、受信手段から各出力手段に夫々専用の伝送路を介して放送信号を伝送するようにした場合には、殆どの出力手段に対して、放送信号を光信号に変換して光伝送路を介して伝送しなければならなくなり、これでは、受信手段側に設ける光送信器の数や、各光送信器から各出力手段に光信号を伝送するための光伝送路（一般に光ファイバ）や数が膨大となり、移動体用放送信号再送信システムのコストアップを招いてしまう。
【００１６】
そこで、請求項１〜６に記載の移動体用放送信号再送信システムにおいては、走行路に沿って分散配置された複数の出力手段が、走行路に沿って、放送信号を導電線からなる電気伝送路（同軸ケーブル等）を介して電気信号の状態で伝送可能な距離毎にグループ分けされると共に、受信手段が、受信した放送信号を光信号に変換して出力するように構成される。
【００１７】
また、請求項１〜６に記載の移動体用放送信号再送信システムには、上記のようにグループ分けされた出力手段の各グループに１つの割で、受信手段から伝送されてきた光信号を電気信号からなる放送信号に変換する中継手段が設けられ、受信手段から各中継手段には、夫々、光伝送手段としての光伝送路を介して光信号を伝送し、各中継手段から対応するグループの出力手段には、電気伝送手段としての電気伝送路を介して、放送信号を伝送するようにされている。
【００１８】
このため請求項１〜６に記載の移動体用放送信号再送信システムによれば、漏洩同軸ケーブルを敷設する走行路の距離が長く、その走行路に沿って配置される出力手段の数が増えたとしても、受信手段に設ける光送信器の数や光伝送路の数を、各出力手段をグループ分けしたグループの数に制限することができ、本発明の移動体用放送信号再送信システムを比較的安価に構成できることになる。
【００１９】
つまり、放送信号を光信号に変換して伝送する場合、放送信号を電気信号の状態で伝送する電気伝送路や伝送機器に比べて極めて高価な光伝送用の機材（光送信器や光伝送路等）が必要であるが、この場合、上記のように、出力手段をグループ分けして、各グループ毎に、光信号を電気信号（放送信号）に変換する中継手段を設け、受信手段から各中継手段に光信号を伝送するようにすれば、光信号伝送用の機材（光送信器や光伝送路等）を少なくして、移動体用放送信号再送信システムのコストを抑制できるようになる。
【００２０】
また更に、出力手段をグループ分けして、各グループ毎に中継手段を設ける場合、受信手段から各グループの中継手段には、夫々、専用の光伝送路を介して光信号を伝送するようにしてもよいが、請求項１〜６に記載の移動体用放送信号再送信システムにおいては、中継手段を、走行路に沿って複数にグループ分けし、各グループを構成する中継手段の一つを、光伝送手段としての第１光伝送路を介して受信手段から伝送されてきた光信号を受信し、その光信号を電気信号に変換して増幅した後、再度光信号に変換し、その変換後の光信号を、光伝送手段としての第２光伝送路を介して、同一グループの他の中継手段に送信する基地局として構成することで、受信手段が、各グループの基地局に対して、第１光伝送路を介して光信号を送信するようにされている。
【００２１】
つまり、移動体用放送信号再送信システムをこのように構成すれば、受信手段から光信号を送信する光送信器や光伝送路（ここでは第１光伝送路）の数を少なくして、移動体用放送信号再送信システムをより低コストで実現できる。
【００２２】
尚、移動体用放送信号再送信システムを上記のように構成した場合、同一グループを構成する中継手段の内、基地局となる中継手段から他の中継手段に対しては、第２光伝送路を介して、光信号が伝送されることになるが、この光信号の伝送には、請求項１に記載のように、光カプラや光スプリッタ等からなる光分岐手段を用いるようにするとよい。
【００２３】
即ち、請求項１に記載の移動体用放送信号再送信システムでは、同一グループを構成する中継手段の内、基地局となる中継手段から第２光伝送路を介して光信号を受ける中継手段が、第２光伝送路を流れる光信号を光分岐手段を介して取り込むことで、光信号を第２光伝送路を介してグループの末端の中継手段まで伝送するよう構成される。
このため、基地局から同一グループの中継手段に対しては、第２光伝送路１本で光信号を伝送できることになり、基地局となる中継手段に設ける光送信器や第２光伝送路の数を１つにして、本発明の移動体用放送信号再送信システムをより低コストで実現できることになる。
【００２４】
ところで、移動体用放送信号再送信システムを上記のように構成した場合、受信手段から各基地局（中継手段）に光信号を伝送するのに使用される第１光伝送路の距離は、基地局から同一グループの中継手段に対して光信号を伝送する第２光伝送路に比べて極めて長くなる。
このため、受信手段には、基地局に比べて大電力の光信号を送信可能な高価な光送信器を設ける必要があるが、光送信器の送信電力を単に増加させるだけでは、移動体用放送信号再送信システムのコストアップを招くだけでなく、光信号の伝送距離を延ばすにも限界がある。
【００２５】
このため、移動体用放送信号再送信システムの規模にもよるが、漏洩同軸ケーブルを利用して、数百ｋｍといった長距離の走行路上で放送信号を再送信するような場合には、請求項２又は請求項３に記載のように、第１光伝送路を介して受信手段から各グループの基地局へ夫々伝送される光信号の波長を、基地局から中継手段へ第２光伝送路を介して伝送される光信号の波長よりも長くし、第１光伝送路で生じる光信号の伝送ロスを、第２光伝送路で生じる光信号の伝送ロスよりも少なくすることが望ましい。
【００２６】
つまり、このようにすれば、受信手段から第１光伝送路を介して光信号を伝送可能な距離を長くし、放送信号の再送信を行う走行路の長さ、延いては、本発明の移動体用放送信号再送信システムの規模を、大きくすることができる。
また、本発明を、より大規模な移動体用放送信号再送信システムとして実現する場合には、請求項４に記載のように、移動体の走行路に対して、受信手段を起点として第１光伝送路を介して光信号を伝送可能な距離毎に、放送信号を一旦復調して再変調する再生中継手段を配置し、この再生中継手段が、第１光伝送路を介して受信手段から送信された光信号を取得し、その光信号を電気信号からなる放送信号に変換して、その放送信号を一旦復調することにより、放送信号を再生し、その再生した放送信号を光信号に変換して、その変換後の光信号を、第１光伝送路を介して、当該再生中継手段よりも前記受信手段から離れた再生中継手段及び当該再生中継手段周囲の基地局に夫々送信するようにすればよい。
【００２７】
一方、本発明の移動体用放送信号再送信システムを実現するには、放送信号の再送信サービスを行うべき走行路に沿って敷設された漏洩同軸ケーブルが必要であるが、この漏洩同軸ケーブルは、当該システム専用のものである必要はなく、例えば、新幹線等の列車に対して放送信号を再送信するような場合には、請求項５又は請求項７に記載のように、列車無線用として線路に沿って敷設された既存の漏洩同軸ケーブルを利用することができる。
【００２８】
但し、この場合、この漏洩同軸ケーブルに放送信号を出力する出力手段としては、少なくとも、列車無線用の伝送機器と漏洩同軸ケーブルとの接続部分に配置されて、この接続部分を流れる無線通信用の信号と、受信手段から伝送手段を介して伝送されてきた放送信号とを混合する混合手段を用いる必要がある。
【００２９】
また、この場合、より好ましくは、請求項６又は請求項８に記載のように、出力手段には、伝送手段を介して取得した放送信号を増幅して混合手段に出力する増幅手段を設けることが望ましい。
【００３０】
【発明の実施の形態】
以下に本発明の実施の形態（実施例）を図面と共に説明する。
図１は、本発明が適用された実施例の放送信号再送信システム全体の構成を表す説明図である。
【００３１】
本実施例の放送信号再送信システムは、新幹線等の列車に対して、例えば地上波デジタル放送等のテレビ放送信号（周波数：例えば４７０ＭＨｚ〜５８０ＭＨｚのＲＦ信号）を再送信するためのものであり、テレビ放送信号（以下、ＴＶ放送信号と記載する）の再送信には、列車の線路に沿って既に敷設されている列車無線用の漏洩同軸ケーブル（以下、単にＬＣＸという）２０を利用する。
【００３２】
即ち、図１（ａ）に示すように、新幹線等の列車無線では、東京、名古屋、大阪、…といった各地区の中心となる駅に統制局１０を設置し、各統制局１０の間を通信回線１４で接続すると共に、各統制局１０と各統制局１０が管轄する駅毎に設置された基地局（以下、無線基地局という）１２とを夫々通信用のアプローチ回線１６を介して接続し、更に、各無線基地局１２を中心として線路の全線をカバーするように夫々敷設された複数のＬＣＸ２０と各無線基地局１２とを接続することにより、線路上の列車が、ＬＣＸ２０を介して、無線基地局１２（延いては統制局１０）との間で無線通信できるようにされているため、本実施例の放送信号再送信システムは、こうした既存の列車無線設備２を利用して、線路上の列車に対して、ＴＶ放送信号を再送信するのである。
【００３３】
そして、このために、本実施例の放送信号再送信システムでは、図１（ａ）に示すように、統制局１０が配置された任意の駅に、受信手段としての受信設備（所謂ヘッドエンド）３０を設置すると共に、他の統制局１０が配置された駅には、受信設備３０から伝送されてきた受信信号（ＴＶ放送信号）を一旦復調して再変調することにより再生し、その再生した受信信号を更に遠くの統制局１０まで送信する再生中継装置３１を設置することで、線路の全線に渡って、一つの受信設備３０で受信したＴＶ放送信号を伝送できるようにされている。
【００３４】
また、各駅には、ＴＶ放送信号再送信用の基地局（以下、ＴＶ用基地局という）３２が設置されており、各ＴＶ用基地局３２には、各ＴＶ用基地局３２を管轄する受信設備３０或いは再生中継装置３１からＴＶ放送信号が伝送される。
また、受信設備３０から再生中継装置３１へのＴＶ放送信号の伝送、再生中継装置３１から他の再生中継装置３１へのＴＶ放送信号の伝送、及び、受信設備３０若しくは再生中継装置３１から各ＴＶ用基地局３２へのＴＶ放送信号の伝送には、第１光伝送路としての光ケーブル３４が使用される。
【００３５】
そして、この光ケーブル３４には、光信号を長距離伝送できるように、伝送ロスが小さい長波長（例えば、波長：１．５５μｍ）の光信号を伝送するための光ケーブルが使用されている。
即ち、図２に示すように、受信設備３０には、例えば、地上波デジタル放送を行う放送局からの送信電波を受信する受信アンテナ４１と、この受信アンテナ４１からの受信信号（つまりＴＶ放送信号）を増幅する増幅器（以下、光増幅器と区別するために電気増幅器という）４２と、電気増幅器４２による増幅後のＴＶ放送信号を複数に分配する分配器４４と、この分配器４４で分配されたＴＶ放送信号を夫々長波長の光信号に変換する複数の光送信器（Ｅ／Ｏ）４６と、光送信器４６にて変換された光信号を増幅して光ケーブル３４に出力する複数の光増幅器４８とが備えられ、これら各光増幅器４８から、光ケーブル３４を介して、再生中継装置３１及び当該受信設備３０が管轄する複数のＴＶ用基地局３２に光信号を送信するようにされている。
【００３６】
また、再生中継装置３１には、受信設備３０から光ケーブル３４を介して伝送されてきた光信号を元のＴＶ放送信号（電気信号：ＲＦ信号）に変換する光受信器（Ｏ／Ｅ）５２と、光受信器５２にて変換されたＴＶ放送信号を各チャンネル毎に一旦復調して再変調することにより各チャンネルのＴＶ放送信号を再生する復変調器５４と、この復変調器５４にて再生されたＴＶ放送信号を夫々長波長の光信号に変換する複数の光送信器（Ｅ／Ｏ）５６と、光送信器５６にて変換された光信号を増幅して光ケーブル３４に出力する複数の光増幅器５８とが備えられ、これら各光増幅器４８から、光ケーブル３４を介して、他の再生中継装置３１及び当該再生中継装置３１が管轄する複数のＴＶ用基地局３２に光信号を送信するようにされている。
【００３７】
尚、受信設備３０と再生中継装置３１とを接続する光ケーブル３４等、光信号の伝送距離が長くなる光ケーブル３４には、適宜、光信号を増幅する光増幅器５０が設けられ、光信号の伝送ロスを補償するようにされている。
一方、図１（ｂ）に示すように、列車無線設備２において、各無線基地局１２が管轄するＬＣＸ２０は、線路に沿って、所定距離間隔（例えば、１．３ｋｍ〜１．５ｋｍ間隔）で分断されており、その分断されたＬＣＸ２０の間には、列車と無線基地局１２との間で送受信される通信信号を処理（増幅・再生等）するための無線中継器１８が設けられている。このため、ＬＣＸ２０を利用してＴＶ放送信号を再送信するには、無線中継器１８で分断された各ＬＣＸ２０毎にＴＶ放送信号を重畳する必要がある。
【００３８】
そこで、本実施例の放送信号再送信システムでは、各ＴＶ用基地局３２が管轄する全線路領域で各ＬＣＸ２０にＴＶ放送信号を配信するために、ＴＶ用基地局３２を中心として所定距離間隔（例えば、約４ｋｍ間隔）でＴＶ用中継器３８を設置し、ＴＶ用基地局３２から各ＴＶ用中継器３８へ、第２光伝送路としての光ケーブル３６を介してＴＶ放送信号（光信号）を伝送し、更に、各ＴＶ用中継器３８から各ＬＣＸ２０へは、導電線からなる電気伝送路である同軸ケーブル４０を介してＴＶ放送信号（電気信号）を伝送（ＲＦ伝送）するようにされている。
【００３９】
尚、光ケーブル３６には、短波長（例えば、波長：１．３１μｍ）の光信号を伝送するための光ケーブルが使用されている。これは、ＴＶ用基地局３２から端末側に光信号を伝送すべき距離が短く、短波長の光信号でも良好な伝送品質が得られるためである。
【００４０】
即ち、図３に示すように、ＴＶ用基地局３２には、光ケーブル３４を介して受信設備３０若しくは再生中継装置３１から伝送されてきた光信号を、元のＴＶ放送信号（電気信号：ＲＦ信号）に変換する光受信器（Ｏ／Ｅ）６０と、光受信器５２にて変換されたＴＶ放送信号を増幅する電気増幅器６２と、電気増幅器６２にて増幅されたＴＶ放送信号を短波長の光信号に変換する光送信器（Ｅ／Ｏ）６４と、光送信器６４にて変換された光信号を光ケーブル３６に出力すると共に、その光信号の一部を分岐させる光分岐手段としての光分岐器（具体的には光カプラ、光スプリッタ等）６６と、光分岐器６６で分岐された光信号を元のＴＶ放送信号に変換する光受信器（Ｏ／Ｅ）６８とが備えられている。
【００４１】
また、ＴＶ用中継器３８には、光ケーブル３６を介してＴＶ用基地局３２から伝送されてきた光信号の一部を取り込むための光分岐器６６と、光分岐器６６で分岐された光信号を元のＴＶ放送信号に変換する光受信器（Ｏ／Ｅ）６８とが備えられている。
【００４２】
そして、ＴＶ用基地局３２或いはＴＶ用中継器３８の光受信器６８にて変換されたＴＶ放送信号は、同軸ケーブル４０を介して、ＴＶ用基地局３２或いはＴＶ用中継器３８が管轄するＬＣＸ２０に直接された無線基地局１２或いは無線中継器１８まで夫々伝送され、無線基地局１２或いは無線中継器１８とＬＣＸ２０との接続部分に設けられた混合器７８を介して、各ＬＣＸ２０に出力される。
【００４３】
尚、同軸ケーブル４０には、適宜、一般的なＣＡＴＶシステムで使用されるＴＶ放送信号増幅用の電気増幅器７２が設けられ、同軸ケーブル４０でのＴＶ放送信号の伝送ロスを補償するようにされている。
また、列車無線設備２では、下り列車用と上り列車用とに分けて２本のＬＣＸ２０が線路に沿って敷設されており、無線基地局１２及び無線中継器１８は、これら２本のＬＣＸ２０に夫々接続されているため、同軸ケーブル４０を介して無線基地局１２或いは無線中継器１８まで伝送されて来たＴＶ放送信号は、分配器７４を介して２分配若しくは４分配され、更に、電気増幅器７４で増幅された後、各接続部分に設けられた混合器７８を介して、各ＬＣＸ２０に出力される。
【００４４】
また、混合器７８は、図４に示すように、ハイパスフィルタ（ＨＰＦ）７８ａとローパスフィルタ（ＬＰＦ）７８ｂとからなる所謂ダイプレックスフィルタとして構成されており、ＴＶ用基地局３２側から伝送されてきたＴＶ放送信号をＨＰＦ７８を介してＬＣＸ２０に出力し、無線基地局１２或いは中継器１８とＬＣＸ２０との間はＬＰＦ７８ｂを介して通信信号を通過させる。これは、列車無線で使用される通信信号の周波数が４００ＭＨｚ帯で、再送信の対象となるＴＶ放送信号の周波数（４７０ＭＨｚ〜５８０ＭＨｚよりも低いためである。
【００４５】
以上説明したように、本実施例の放送信号再送信システムは、既設の列車無線設備２を利用し、その列車無線設備で線路に沿って敷設されているＬＣＸ２０を介して、地上波デジタル放送のＴＶ放送信号を再送信するようにされている。
このため、本実施例によれば、放送信号再送信システム専用の漏洩同軸ケーブル（ＬＣＸ）を新たに敷設することなく、走行中の列車に対してＴＶ放送信号を安定して配信することができるようになり、列車側では、ＬＣＸ２０から放射される放送信号の電波を受信し、復調することで、所望チャンネルの放送信号を安定して選局・復調できることになる。
【００４６】
また、本実施例では、光ケーブル３４、３６を用いた光伝送、及び、同軸ケーブル４０を用いたＲＦ伝送によって、ＴＶ放送信号を再送信すべき線路全域に、一つの受信設備３０で受信したＴＶ放送信号を再送信するようにされているので、その線路上に再送信されるＴＶ放送信号の放送チャンネルは一定であり、列車側では、走行している地域によって選局・復調する放送チャンネルを切り換える必要がない。
【００４７】
尚、本実施例では、光ケーブル３４、光増幅器５０、再生中継装置３１、ＴＶ用基地局３２、光ケーブル３６、ＴＶ用中継器３８、同軸ケーブル４０、電気増幅器７２が、本発明の伝送手段に相当する。また、このうち、光ケーブル３４は、本発明の第１光伝送路に相当し、再生中継装置３１は、本発明の再生中継手段に相当し、ＴＶ用基地局３２及びＴＶ用中継器３８は、本発明の中継手段に相当し、光ケーブル３６は、本発明の第２光伝送路に相当し、同軸ケーブル４０は、本発明の電気伝送路に相当する。また、分配器７４、電気増幅器７６、混合器７８は、本発明の出力手段に相当し、このうち、電気増幅器７６は、本発明の増幅手段に相当し、混合器７８は、本発明の混合手段に相当する。
【００４８】
ところで、本実施例では、ＴＶ放送信号の長距離伝送を可能とするために再生中継装置３１を設け、受信設備３０から再生中継装置３１、再生中継装置３１から更に離れた再生中継装置３１へと、ＴＶ放送信号を再生中継しながら伝送するようにしているが、上述したように、ＴＶ放送信号の伝送に、波長：１．５５μｍの長波長の光信号を用いる場合、光ケーブル３４に光増幅器５０を設けたとしても、現状では、図５（ａ）に示すように、光増幅器５０で光信号の伝送ロスを補償し得る距離が約６４ｋｍで、また、光増幅器５０を設置可能な数は２個程度であるため（これよりも多くするとＴＶ放送信号のキャリア対ノイズ比（Ｃ／Ｎ）が悪くなる）、約２００ｋｍの光伝送が限界である。このため、本実施例のシステムを実際に構築する際には、再生中継装置３１は、約２００ｋｍ若しくはそれよりも短い距離間隔で設置することが望ましい。
【００４９】
また、本実施例では、ＴＶ用基地局の光送信器６４からＴＶ用中継器３８の光受信器６８まで光ケーブル３６を介して短波長（波長：１．３１μｍ）の光信号を伝送し、光受信器６８から、ＬＣＸ２０へのＴＶ放送信号の出力部分までは、同軸ケーブル４０を介してＴＶ放送信号をＲＦ伝送するようにしているが、上記のように、同軸ケーブル４０にＣＡＴＶシステムで利用されている増幅器（電気増幅器）７２を設けたとしても、現状では、図５（ｂ）に示すように、ＴＶ放送信号のＲＦ伝送が可能な距離は約２ｋｍである。このため、本実施例のシステムを実際に構築する際には、図５（ｃ）に示すように、ＴＶ用中継器３８は、ＴＶ用基地局３２を中心として、約４ｋｍ（＝２ｋｍ×２）若しくはそれよりも短い距離間隔で設置することが望ましい。
【００５０】
また、光ケーブル３６を用いた短波長の光伝送では、光分岐器６６等による伝送ロスがないとすれば、現状では、図５（ｂ）に示すように、約２８ｋｍ程度の光伝送が可能であるが、本実施例では、光ケーブル３６や光送信器６４の数を少なくするため、ＴＶ用中継器３８に光分岐器６６を設けて、光信号を分岐しながら伝送するようにしているため、図５（ｃ）に示すように、ＴＶ用基地局３２から光ケーブル３６を介して光信号を伝送可能な距離は、約１６ｋｍとなり、光ケーブル３６の末端に、ＴＶ用中継器３８として光受信器６８のみを設けたとしても、ＴＶ用基地局３２からＴＶ放送信号を伝送可能な距離は、約１８ｋｍとなる。このため、本実施例のシステムを実際に構築する際には、ＴＶ用基地局３２は、約３６ｋｍ（＝１８ｋｍ×２）若しくはそれよりも短い距離間隔で設置することが望ましい。
【００５１】
尚、光ケーブル３６に光増幅器を設ければ、ＴＶ用基地局３２から光信号を伝送可能な距離を伸ばすことはできるが、光増幅器は高価であるため、本実施例では、光増幅器は、長波長光伝送用の光ケーブル３４にのみ設けるようにしている。
【００５２】
以上、本発明の一実施例について説明したが、本発明は上記実施例に限定されるものではなく、種々の態様を採ることができる。
例えば、上記実施例では、列車無線用の既存の漏洩同軸ケーブルを利用して、移動体である列車にＴＶ放送信号を再送信するシステムについて説明したが、本発明は、高速道路等に漏洩同軸ケーブルを敷設して、移動体である自動車にＴＶ放送信号を再送信するシステムであっても、上記実施例と同様に適用できる。
【００５３】
尚、この場合、道路に沿って敷設される漏洩同軸ケーブルは、ＴＶ放送信号だけでなく、交通情報等の各種情報を移動体に送信するサービスにも利用できる。
また、上記実施例では、受信手段としての受信設備３０は、地上波デジタル放送を行う放送局から送信された放送電波を受信し、その受信したＴＶ放送信号を出力するものとして説明したが、例えば、人工衛星からの放送電波を受信し、例えばデジタル音声信号を出力するようにすれば、移動体に対してデジタル音声放送を再送信することができる。
【００５４】
また、受信手段としての受信設備３０は、必ずしも、放送局や人工衛星からの送信電波を受信する必要はなく、例えば、インターネットで配信されるインターネットテレビ放送、或いはインターネットラジオ放送を受信し、各放送信号を所定の放送チャンネルの周波数帯に変換して、出力するようにすれば、各種インターネット放送信号を、移動体に対して再送信することができる。
【００５５】
また、上記実施例では、線路に沿って敷設された漏洩同軸ケーブルを利用して列車の線路全線に渡って放送信号を再送信するものとして説明したが、例えば、図６に示すように、トンネル内等、電波の届き難い区間でのみ放送信号を再送信するようにしてもよい。
【００５６】
そして、この場合は、放送信号を再送信すべき走行路の長さが短いことから、トンネル内に、トンネル外部に設置した受信設備から同軸ケーブル若しくは光ケーブルを介して放送信号を受けるＴＶ用中継局を設け、この中継局から同軸ケーブル４０を介して各ＬＣＸ２０にＴＶ放送信号を伝送するようにすればよい。
【図面の簡単な説明】
【図１】実施例の放送信号再送信システム全体の構成を表すブロック図である。
【図２】受信設備及び再生中継装置の構成を表す説明図である。
【図３】ＴＶ用基地局からＬＣＸ２０に至る伝送系の詳細構成を表す説明図である。
【図４】混合器の構成を表す説明図である。
【図５】再生中継装置及びＴＶ用中継器の設置間隔を説明する説明図である。
【図６】トンネル内の放送信号再送信システムの構成を表すブロック図である。
【符号の説明】
２…列車無線設備、１０…統制局、１２…無線基地局、１４…通信回線、１６…アプローチ回線、１８…無線中継器、３０…受信設備、３１…再生中継装置、３２…ＴＶ用基地局、３４，３６…光ケーブル、３８…ＴＶ用中継器、４０…同軸ケーブル、４１…受信アンテナ、４２，６２…電気増幅器、４４…分配器、４６，５６，６４…光送信器、４８，５０，５８…光増幅器、５２，６８…光受信器、５４…復変調器、６２，７２，７４，７６…電気増幅器、６６…光分岐器、７４…分配器、７８…混合器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile broadcast signal retransmission system that receives a broadcast signal of a television or the like and retransmits the received broadcast signal toward a traveling path of the mobile body.
[0002]
[Prior art and problems to be solved by the invention]
In order to make it possible to view TV broadcasts on mobile objects such as automobiles and trains, the mobile object can receive a broadcast antenna received from the broadcast station and broadcast signals received by this reception antenna. A tuner for selecting and demodulating a broadcast signal of a desired channel from among them may be provided.
[0003]
However, in this way, when the broadcast antenna from the broadcasting station is directly received by the reception antenna provided on the mobile body, when the mobile body moves, it can be obtained by the reception antenna due to environmental changes around the traveling road. Since the reception level of the broadcast signal to be changed fluctuates, there has been a problem that it is impossible to view the television broadcast well. Also, in this case, when the mobile body is traveling in a place where broadcast radio waves do not reach such as in a tunnel, it is impossible to receive a broadcast signal, so it is impossible to view TV broadcast on the mobile body. There is also a problem.
[0004]
In addition, when the broadcast wave from the broadcasting station is directly received by the receiving antenna provided on the moving body as described above, the moving antenna moves with the receiving antenna along with the movement of the moving body. Since the broadcasting station that can receive broadcast waves changes, the channel of the broadcast signal to be selected by the tuner must be switched according to the movement of the moving object, and the operation for selecting the channel is troublesome. There is also a problem.
[0005]
The present invention has been made in view of these problems, and provides a mobile broadcast signal retransmission system that retransmits various broadcast signals such as television broadcasts to the mobile travel path, thereby reducing the travel path. An object of the present invention is to make it possible to stably select and demodulate a desired broadcast on a moving mobile object.
[0006]
[Means for Solving the Problems]
  According to the present invention (claims 1 to 9) made to achieve such an object.In the broadcast signal retransmission system for a mobile unit, the broadcast signal received by the reception unit is transmitted to the output unit via the transmission unit, and the output unit transmits the broadcast signal along the traveling path of the mobile unit. By outputting the signal to the installed leaky coaxial cable, the broadcast signal is transmitted wirelessly from the leaky coaxial cable toward the traveling path.
[0007]
That is, the mobile broadcast signal retransmission system of the present invention uses a leaky coaxial cable conventionally used in train radio etc. to transmit the broadcast signal along the travel path of the mobile, Broadcast signals are distributed wirelessly to a moving body that travels along a travel path.
[0008]
For this reason, according to the present invention, even if the traveling path of the mobile object is in a place where broadcast radio waves from the broadcasting station are difficult to reach, or even if the traveling path is in a tunnel, the mobile body leaks along the traveling path. By laying the coaxial cable, it becomes possible to always deliver a broadcast signal stably to a moving body traveling on the traveling path. On the moving body side traveling on the traveling path, from the leaky coaxial cable By receiving and demodulating the radiated broadcast signal, the broadcast signal of the desired channel can be selected and demodulated stably.
[0009]
Further, in the broadcast signal retransmission system for a mobile body of the present invention, since the broadcast signal received by the receiving means flows through the leaky coaxial cable, the distance of the travel path where the leaky coaxial cable is laid is long, Even when the road spans the service areas of a plurality of broadcasting stations, the broadcast signal from the broadcasting station in the area where the receiving means is installed is retransmitted from the leaky coaxial cable.
[0010]
For example, if a leaky coaxial cable is laid along a traveling path of a moving body from Tokyo to Osaka (for example, a train line such as a bullet train or a highway), the traveling path is broadcast in the Kanto region near Tokyo. It belongs to the service area of the station, belongs to the service area of the broadcasting station in the Kansai region near Osaka, and belongs to the service area of the broadcasting station in the Tokai region near Nagoya between Tokyo and Osaka. Even when the receiving means is installed in the Kanto region, the Kanto region broadcast signal is retransmitted and the receiving means is installed in the Kansai region throughout the travel route where the leaky coaxial cable is laid. If this is the case, broadcast signals in the Kansai region are retransmitted over the entire travel path where the leaky coaxial cable is laid.
[0011]
For this reason, according to the present invention, the broadcast signal of the same channel can be received over the entire travel route where the leaky coaxial cable is laid, and the broadcast signal of the desired channel is received on the mobile body side traveling on this travel route. Therefore, it is not necessary to switch the channel for selecting a broadcast signal while the mobile body is traveling.
[0012]
By the way, as in the present invention, when retransmitting a broadcast signal using a leaky coaxial cable laid on the road, there is a limit to the distance at which the broadcast signal can be retransmitted with a single leaky coaxial cable. The current leaky coaxial cable put into practical use in train radio etc. is extremely short, for example, 1 km to 2 km.
[0013]
Therefore, in the mobile broadcast signal retransmission system according to claims 1 to 6 and 9,A plurality of leaky coaxial cables of a length capable of retransmitting broadcast signals are continuously laid along the traveling path of the moving body, and the output means is adapted to the plurality of leaky coaxial cables along the traveling path. The transmission means is configured to transmit the broadcast signal received by the receiving means to the plurality of output means, respectively.Has been.
[0014]
In this way, when the broadcast signal received by the receiving means is transmitted to a plurality of output means, the transmission means is directly transmitted from the receiving means to each output means via a transmission path dedicated to each output means. However, with this configuration, as the traveling path of the moving body becomes longer and the number of output means distributed in the traveling path increases, the receiving means to the output means The number of transmission paths for transmitting broadcast signals and the number of devices for transmitting broadcast signals increase, leading to an increase in cost of the mobile broadcast signal retransmission system.
[0015]
That is, when a broadcast signal is transmitted in the state of an electric signal using an electric transmission line (generally a coaxial cable) made of a conductive line as in a general CATV system, the transmittable distance is the transmission distance of the broadcast signal. Even if an amplifying device that compensates for loss is used, it is only a few kilometers, so for output means whose distance to the receiving means exceeds this transmittable distance (several kilometers), an optical signal with little transmission loss is used. As described above, when a broadcast signal is transmitted from the receiving means to each output means via a dedicated transmission path as described above, the broadcast signal is transmitted to most output means. It must be converted into an optical signal and transmitted through an optical transmission line. In this case, the number of optical transmitters provided on the receiving means side and the optical signal to be transmitted from each optical transmitter to each output means Optical transmission line (generally optical fiber) It becomes enormous, resulting in an increase in cost of the mobile body broadcasting signal retransmission system.
[0016]
  Therefore,In the mobile broadcast signal retransmission system according to claim 1,A plurality of output means arranged in a distributed manner along the travel path for each distance at which the broadcast signal can be transmitted along the travel path in the state of an electrical signal via an electrical transmission path (coaxial cable, etc.) made of conductive wires. In addition to being grouped, the receiving means is configured to convert the received broadcast signal into an optical signal and output it.
[0017]
  Also,Claims 1-6In the broadcast signal retransmission system for a mobile unit, a relay for converting an optical signal transmitted from a receiving means into a broadcast signal made up of an electric signal, one for each group of output means grouped as described above. Means for transmitting an optical signal from the receiving means to each relay means via an optical transmission path as an optical transmission means, and from each relay means to an output means of the corresponding group as an electric transmission means. Broadcast signals are transmitted through the electrical transmission line.
[0018]
  For this reasonClaims 1-6According to the mobile broadcast signal re-transmission system, even if the distance of the traveling path where the leaky coaxial cable is laid is long and the number of output means arranged along the traveling path increases, the optical transmission provided in the receiving means The number of units and the number of optical transmission lines can be limited to the number of groups obtained by grouping each output means, and the mobile broadcast signal retransmission system of the present invention can be configured at a relatively low cost.
[0019]
  That is, when a broadcast signal is converted into an optical signal and transmitted, the equipment for optical transmission (optical transmitter or optical transmission path) is extremely expensive compared to an electrical transmission path or transmission equipment that transmits the broadcast signal in the state of an electrical signal. Etc.)In this case, as above,If the output means is divided into groups and a relay means for converting an optical signal into an electrical signal (broadcast signal) is provided for each group, and the optical signal is transmitted from the receiving means to each relay means, optical signal transmission Equipment costs (optical transmitters, optical transmission lines, etc.) can be reduced to reduce the cost of broadcast signal retransmission systems for mobile objectsBecome.
[0020]
  Furthermore, when the output means is divided into groups and a relay means is provided for each group, an optical signal is transmitted from the receiving means to the relay means of each group via a dedicated optical transmission line. It ’s okay,In the mobile broadcast signal retransmission system according to claim 1,Relay meansTheThe optical signal transmitted from the receiving means via the first optical transmission line as the optical transmission means is received by one of the relay means constituting each group divided into a plurality of groups along the traveling path, After the optical signal is converted into an electrical signal and amplified, it is converted again into an optical signal, and the converted optical signal is sent to another relay means in the same group via the second optical transmission line as the optical transmission means. Configure as transmitting base stationWith thatThe receiving means transmits an optical signal to the base station of each group via the first optical transmission line.Has been.
[0021]
  In other words, the mobile broadcast signal retransmission systemin this wayIf configured, the number of optical transmitters and optical transmission lines (here, the first optical transmission lines) that transmit optical signals from the receiving means is reduced.AndA mobile broadcast signal retransmission system can be realized at a lower cost.
[0022]
  still, TransferBroadcast signal retransmission system for moving objectsWhen configured as above,Among the relay means constituting the same group, an optical signal is transmitted from the relay means serving as a base station to the other relay means via the second optical transmission path. For transmission,Claim 1As described, it is preferable to use an optical branching unit composed of an optical coupler, an optical splitter, or the like.
[0023]
  That is,Claim 1In the mobile broadcast signal retransmission system described above, the relay unit that receives the optical signal from the relay unit serving as a base station through the second optical transmission line among the relay units constituting the same group is the second optical transmission line. By taking the optical signal flowing through the optical branching means through the optical branching means, the optical signal is transmitted to the relay means at the end of the group via the second optical transmission line.
  For this reason, an optical signal can be transmitted from the base station to the same group of relay means using one second optical transmission line, and the optical transmitter and the second optical transmission line provided in the relay means serving as the base station can be used. By making the number one, the mobile broadcast signal retransmission system of the present invention can be realized at a lower cost.
[0024]
  by the way, TransferBroadcast signal retransmission system for moving objectsIs configured as above,The distance of the first optical transmission line used for transmitting the optical signal from the receiving means to each base station (relay means) is the second optical transmission for transmitting the optical signal from the base station to the same group of relay means. Extremely long compared to the road.
  For this reason, it is necessary to provide the receiving means with an expensive optical transmitter capable of transmitting an optical signal having a higher power than that of the base station. However, simply increasing the transmission power of the optical transmitter is necessary for a mobile unit. In addition to increasing the cost of the broadcast signal retransmission system, there is a limit to extending the transmission distance of the optical signal.
[0025]
  For this reason, depending on the scale of the broadcast signal retransmission system for mobile units, when a broadcast signal is retransmitted on a long-distance travel path of several hundred km using a leaky coaxial cable,Claim 2 or claim 3As described above, the wavelength of the optical signal transmitted from the receiving means to the base station of each group via the first optical transmission line, and the optical signal transmitted from the base station to the relay means via the second optical transmission line. It is desirable that the transmission loss of the optical signal generated in the first optical transmission path is less than the transmission loss of the optical signal generated in the second optical transmission path.
[0026]
  In other words, in this way, the distance that the optical signal can be transmitted from the receiving means via the first optical transmission line is increased, and the length of the traveling path for retransmitting the broadcast signal, that is, The scale of the mobile broadcast signal retransmission system can be increased.
  When the present invention is realized as a larger-scale mobile broadcast signal retransmission system,Claim 4The regenerative repeater that once demodulates and remodulates the broadcast signal for each distance that the optical signal can be transmitted through the first optical transmission line from the receiving means as a starting point with respect to the traveling path of the mobile body The regenerative relay means acquires the optical signal transmitted from the receiving means via the first optical transmission line, converts the optical signal into a broadcast signal composed of an electric signal, and converts the broadcast signal into the broadcast signal. Once demodulated, the broadcast signal is reproduced, the reproduced broadcast signal is converted into an optical signal, and the converted optical signal is received from the reproduction relay unit via the first optical transmission line. It is only necessary to transmit to the regenerative relay means remote from the means and the base stations around the regenerative relay means.
[0027]
  On the other hand, in order to realize the broadcast signal retransmission system for a mobile unit of the present invention, a leaky coaxial cable laid along a traveling path where a broadcast signal retransmission service should be performed is necessary. It is not necessary to be dedicated to the system. For example, when retransmitting broadcast signals to trains such as Shinkansen,Claim 5 or claim 7As described above, the existing leaky coaxial cable laid along the track for train radio can be used.
[0028]
However, in this case, as an output means for outputting a broadcast signal to the leaky coaxial cable, it is arranged at least at the connection portion between the transmission device for train radio and the leaky coaxial cable, and for radio communication flowing through this connection portion. It is necessary to use mixing means for mixing the signal and the broadcast signal transmitted from the receiving means through the transmission means.
[0029]
  In this case, more preferably,Claim 6 or Claim 8As described above, it is desirable that the output means is provided with an amplifying means for amplifying the broadcast signal acquired via the transmission means and outputting the amplified signal to the mixing means.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments (examples) of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing the overall configuration of a broadcast signal retransmission system according to an embodiment to which the present invention is applied.
[0031]
The broadcast signal retransmission system of the present embodiment is for retransmitting a television broadcast signal (frequency: for example, an RF signal of 470 MHz to 580 MHz) such as a terrestrial digital broadcast to a train such as a bullet train, For retransmitting a television broadcast signal (hereinafter referred to as a TV broadcast signal), a leaky coaxial cable (hereinafter simply referred to as LCX) 20 already laid along a train line is used.
[0032]
That is, as shown in FIG. 1A, in train radio such as the Shinkansen, a control station 10 is installed at a central station in each district such as Tokyo, Nagoya, Osaka,... In addition to being connected by a line 14, each control station 10 and a base station (hereinafter referred to as a radio base station) 12 installed at each station under the control of each control station 10 are connected via an approach line 16 for communication. Furthermore, by connecting each radio base station 12 with a plurality of LCXs 20 each laid so as to cover all the lines of the track with each radio base station 12 as the center, the train on the track can pass through the LCX 20. Since the wireless communication with the radio base station 12 (and thus the control station 10) can be performed wirelessly, the broadcast signal retransmission system according to the present embodiment uses the existing train radio equipment 2 to TV on the train above It is retransmitting a signal.
[0033]
For this purpose, in the broadcast signal retransmission system according to the present embodiment, as shown in FIG. 1 (a), a receiving facility (so-called headend) as a receiving means is provided at any station where the control station 10 is arranged. 30 and at the station where the other control station 10 is located, the received signal (TV broadcast signal) transmitted from the receiving facility 30 is once demodulated and remodulated to be reproduced. By installing a regenerative repeater 31 that transmits a received signal to a farther control station 10, a TV broadcast signal received by one receiving facility 30 can be transmitted over the entire line.
[0034]
Each station is provided with a base station (hereinafter referred to as a TV base station) 32 for retransmitting TV broadcast signals, and each TV base station 32 has a receiving facility that controls each TV base station 32. 30 or the regenerative repeater 31 transmits a TV broadcast signal.
In addition, transmission of TV broadcast signals from the reception facility 30 to the regenerative relay device 31, transmission of TV broadcast signals from the regenerative relay device 31 to other regenerative relay devices 31, and each TV from the reception facility 30 or the regenerative relay device 31 An optical cable 34 serving as a first optical transmission path is used for transmitting a TV broadcast signal to the base station 32.
[0035]
The optical cable 34 is an optical cable for transmitting an optical signal having a long wavelength (for example, wavelength: 1.55 μm) with a small transmission loss so that the optical signal can be transmitted over a long distance.
That is, as shown in FIG. 2, the receiving facility 30 includes, for example, a receiving antenna 41 that receives a transmission radio wave from a broadcasting station that performs digital terrestrial broadcasting, and a reception signal (that is, a TV broadcast signal) from the receiving antenna 41. ) 42 (hereinafter referred to as an electric amplifier to distinguish it from an optical amplifier), a distributor 44 for distributing the TV broadcast signal amplified by the electric amplifier 42 into a plurality of parts, and the distributor 44 A plurality of optical transmitters (E / O) 46 for converting TV broadcast signals into long-wavelength optical signals, and a plurality of optical amplifiers for amplifying the optical signals converted by the optical transmitter 46 and outputting them to the optical cable 34 48, and transmit optical signals from each of these optical amplifiers 48 to the plurality of TV base stations 32 managed by the regenerative repeater 31 and the receiving equipment 30 via the optical cable 34. To have.
[0036]
The regenerative repeater 31 includes an optical receiver (O / E) 52 that converts an optical signal transmitted from the receiving facility 30 via the optical cable 34 into an original TV broadcast signal (electrical signal: RF signal). The TV broadcast signal converted by the optical receiver 52 is demodulated once for each channel and re-modulated to regenerate the TV broadcast signal of each channel, and the re-modulator 54 reproduces the TV broadcast signal. A plurality of optical transmitters (E / O) 56 for converting the TV broadcast signals converted into long wavelength optical signals, and a plurality of optical signals converted by the optical transmitter 56 and output to the optical cable 34 An optical amplifier 58 is provided, and an optical signal is transmitted from each of these optical amplifiers 48 to another regenerative repeater 31 and a plurality of TV base stations 32 managed by the regenerative repeater 31 via the optical cable 34. Has been.
[0037]
An optical amplifier 50 that amplifies the optical signal is appropriately provided in the optical cable 34 that increases the transmission distance of the optical signal, such as the optical cable 34 that connects the reception facility 30 and the regenerative repeater 31, and transmission loss of the optical signal is appropriately provided. Have been to compensate.
On the other hand, as shown in FIG.1 (b), in the train radio | wireless installation 2, LCX20 which each radio base station 12 has jurisdiction at a predetermined distance interval (for example, 1.3km-1.5km interval) along a track | line. A radio repeater 18 is provided between the divided LCXs 20 to process (amplify / regenerate, etc.) communication signals transmitted and received between the train and the radio base station 12. . For this reason, in order to retransmit the TV broadcast signal using the LCX 20, it is necessary to superimpose the TV broadcast signal for each LCX 20 divided by the wireless repeater 18.
[0038]
Therefore, in the broadcast signal retransmission system according to the present embodiment, in order to distribute the TV broadcast signal to each LCX 20 in the entire line area managed by each TV base station 32, a predetermined distance interval ( For example, TV repeaters 38 are installed at intervals of about 4 km), and TV broadcast signals (optical signals) are transmitted from the TV base stations 32 to the TV repeaters 38 via the optical cable 36 as the second optical transmission line. Furthermore, a TV broadcast signal (electric signal) is transmitted (RF transmission) from each TV repeater 38 to each LCX 20 via a coaxial cable 40 which is an electric transmission path made of a conductive wire. Yes.
[0039]
Note that an optical cable for transmitting an optical signal having a short wavelength (for example, wavelength: 1.31 μm) is used for the optical cable 36. This is because the distance at which the optical signal should be transmitted from the TV base station 32 to the terminal side is short, and good transmission quality can be obtained even with an optical signal with a short wavelength.
[0040]
In other words, as shown in FIG. 3, the TV base station 32 receives the optical signal transmitted from the receiving facility 30 or the regenerative repeater 31 via the optical cable 34 as the original TV broadcast signal (electric signal: RF signal). ), An optical amplifier 62 for amplifying the TV broadcast signal converted by the optical receiver 52, and a TV broadcast signal amplified by the electric amplifier 62 with a short wavelength. An optical transmitter (E / O) 64 for converting to an optical signal, and an optical branching means for outputting the optical signal converted by the optical transmitter 64 to the optical cable 36 and branching a part of the optical signal. A branching unit (specifically, an optical coupler, an optical splitter, etc.) 66 and an optical receiver (O / E) 68 for converting the optical signal branched by the optical branching unit 66 into the original TV broadcast signal are provided. Yes.
[0041]
Further, the TV repeater 38 includes an optical branching unit 66 for capturing a part of the optical signal transmitted from the TV base station 32 via the optical cable 36, and an optical signal branched by the optical branching unit 66. And an optical receiver (O / E) 68 for converting the signal into the original TV broadcast signal.
[0042]
Then, the TV broadcast signal converted by the optical receiver 68 of the TV base station 32 or the TV repeater 38 is transmitted through the coaxial cable 40 to the LCX 20 that is under the jurisdiction of the TV base station 32 or the TV repeater 38. Are directly transmitted to the radio base station 12 or the radio repeater 18 and output to each LCX 20 via a mixer 78 provided at a connection portion between the radio base station 12 or the radio repeater 18 and the LCX 20. .
[0043]
The coaxial cable 40 is appropriately provided with an electric amplifier 72 for amplifying a TV broadcast signal used in a general CATV system so as to compensate for a transmission loss of the TV broadcast signal in the coaxial cable 40. Yes.
Further, in the train radio equipment 2, two LCXs 20 are laid along the track separately for the down train and the up train, and the radio base station 12 and the radio repeater 18 are connected to the two LCXs 20. Since they are respectively connected, the TV broadcast signal transmitted to the radio base station 12 or the radio repeater 18 via the coaxial cable 40 is divided into two or four via the distributor 74, and further, an electric amplifier After being amplified at 74, the signal is output to each LCX 20 via a mixer 78 provided at each connection portion.
[0044]
As shown in FIG. 4, the mixer 78 is configured as a so-called diplex filter including a high-pass filter (HPF) 78a and a low-pass filter (LPF) 78b, and is transmitted from the TV base station 32 side. The TV broadcast signal is output to the LCX 20 via the HPF 78, and the communication signal is passed between the radio base station 12 or the repeater 18 and the LCX 20 via the LPF 78b. This is because the frequency of communication signals used in train radio is in the 400 MHz band and is lower than the frequency of TV broadcast signals to be retransmitted (470 MHz to 580 MHz).
[0045]
As described above, the broadcast signal re-transmission system of the present embodiment uses the existing train radio equipment 2 and performs digital terrestrial broadcasting via the LCX 20 installed along the track in the train radio equipment. The TV broadcast signal is retransmitted.
For this reason, according to the present embodiment, it is possible to stably distribute TV broadcast signals to a running train without newly laying a leaky coaxial cable (LCX) dedicated to the broadcast signal retransmission system. Thus, on the train side, by receiving and demodulating the radio wave of the broadcast signal radiated from the LCX 20, the broadcast signal of the desired channel can be stably selected and demodulated.
[0046]
Further, in this embodiment, the TV received by one receiving facility 30 over the entire line where the TV broadcast signal should be retransmitted by optical transmission using the optical cables 34 and 36 and RF transmission using the coaxial cable 40. Since the broadcast signal is retransmitted, the broadcast channel of the TV broadcast signal retransmitted on the track is constant, and on the train side, the broadcast channel to be selected and demodulated according to the area where it is running is selected. There is no need to switch.
[0047]
In this embodiment, the optical cable 34, the optical amplifier 50, the regenerative repeater 31, the TV base station 32, the optical cable 36, the TV repeater 38, the coaxial cable 40, and the electric amplifier 72 correspond to the transmission means of the present invention. To do. Of these, the optical cable 34 corresponds to the first optical transmission line of the present invention, the regenerative repeater 31 corresponds to the regenerative repeater of the present invention, and the TV base station 32 and the TV repeater 38 include The optical cable 36 corresponds to the second optical transmission path of the present invention, and the coaxial cable 40 corresponds to the electrical transmission path of the present invention. The distributor 74, the electric amplifier 76, and the mixer 78 correspond to the output means of the present invention. Of these, the electric amplifier 76 corresponds to the amplifying means of the present invention, and the mixer 78 is the mixing means of the present invention. Corresponds to means.
[0048]
By the way, in the present embodiment, a regenerative repeater 31 is provided to enable long-distance transmission of TV broadcast signals, and the reception facility 30 regenerates the regenerative repeater 31, and the regenerative repeater 31 further away from the regenerative repeater 31. The TV broadcast signal is transmitted while being reproduced and relayed. As described above, when a long wavelength optical signal having a wavelength of 1.55 μm is used for transmitting the TV broadcast signal, the optical amplifier 50 is connected to the optical cable 34. However, at present, as shown in FIG. 5A, the distance at which the optical amplifier 50 can compensate for the transmission loss of the optical signal is about 64 km, and the number of the optical amplifiers 50 that can be installed is two. Since the number is about one (the number is larger than this, the carrier-to-noise ratio (C / N) of the TV broadcast signal is deteriorated), the optical transmission of about 200 km is the limit. For this reason, when actually constructing the system of the present embodiment, it is desirable to install the regenerative repeaters 31 at a distance interval of about 200 km or shorter.
[0049]
In this embodiment, an optical signal having a short wavelength (wavelength: 1.31 μm) is transmitted from the optical transmitter 64 of the TV base station to the optical receiver 68 of the TV repeater 38 via the optical cable 36. From the receiver 68 to the TV broadcast signal output portion to the LCX 20, the TV broadcast signal is RF-transmitted via the coaxial cable 40. As described above, the coaxial cable 40 is used in the CATV system. Even if the amplifier (electric amplifier) 72 is provided, at present, as shown in FIG. 5B, the distance that can be used for RF transmission of the TV broadcast signal is about 2 km. Therefore, when the system of the present embodiment is actually constructed, as shown in FIG. 5C, the TV repeater 38 is about 4 km (= 2 km × 2) with the TV base station 32 as the center. ) Or shorter distance intervals are desirable.
[0050]
In addition, in short-wavelength optical transmission using the optical cable 36, if there is no transmission loss due to the optical branching unit 66 or the like, currently, optical transmission of about 28 km is possible as shown in FIG. However, in this embodiment, in order to reduce the number of optical cables 36 and optical transmitters 64, an optical branching device 66 is provided in the TV repeater 38 so that the optical signal is transmitted while being branched. As shown in FIG. 5C, the distance that the optical signal can be transmitted from the TV base station 32 via the optical cable 36 is about 16 km, and an optical receiver 68 serving as a TV repeater 38 is provided at the end of the optical cable 36. However, the distance that the TV broadcast signal can be transmitted from the TV base station 32 is about 18 km. For this reason, when the system of the present embodiment is actually constructed, it is desirable that the TV base stations 32 be installed at a distance interval of about 36 km (= 18 km × 2) or shorter.
[0051]
If an optical amplifier is provided in the optical cable 36, the distance at which the optical signal can be transmitted from the TV base station 32 can be increased. However, since the optical amplifier is expensive, in this embodiment, the optical amplifier is It is provided only in the optical cable 34 for wavelength light transmission.
[0052]
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
For example, in the above embodiment, a system for retransmitting a TV broadcast signal to a train which is a moving body using an existing leaky coaxial cable for train radio has been described. Even a system in which a cable is laid and a TV broadcast signal is retransmitted to a moving vehicle is applicable in the same manner as in the above embodiment.
[0053]
In this case, the leaky coaxial cable laid along the road can be used not only for the TV broadcast signal but also for a service for transmitting various information such as traffic information to the mobile body.
In the above embodiment, the receiving facility 30 as a receiving unit has been described as receiving a broadcast radio wave transmitted from a broadcasting station that performs terrestrial digital broadcasting and outputting the received TV broadcast signal. If a broadcast radio wave from an artificial satellite is received and, for example, a digital audio signal is output, the digital audio broadcast can be retransmitted to the mobile body.
[0054]
Further, the receiving facility 30 as a receiving means does not necessarily need to receive radio waves transmitted from broadcasting stations or artificial satellites. For example, the receiving facility 30 receives Internet TV broadcasts or Internet radio broadcasts distributed over the Internet, and receives each broadcast. If the signal is converted into a frequency band of a predetermined broadcast channel and output, various Internet broadcast signals can be retransmitted to the mobile body.
[0055]
Further, in the above-described embodiment, it has been described that the broadcast signal is retransmitted over the entire line of the train using the leaky coaxial cable laid along the line. For example, as shown in FIG. The broadcast signal may be retransmitted only in a section where radio waves are difficult to reach.
[0056]
And in this case, since the length of the traveling path where the broadcast signal should be retransmitted is short, the relay station for TV that receives the broadcast signal from the receiving equipment installed outside the tunnel through the coaxial cable or the optical cable in the tunnel And a TV broadcast signal may be transmitted from the relay station to each LCX 20 via the coaxial cable 40.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an entire broadcast signal retransmission system according to an embodiment.
FIG. 2 is an explanatory diagram illustrating configurations of a reception facility and a regenerative repeater.
FIG. 3 is an explanatory diagram showing a detailed configuration of a transmission system from a TV base station to LCX 20;
FIG. 4 is an explanatory diagram showing a configuration of a mixer.
FIG. 5 is an explanatory diagram for explaining an installation interval between a regenerative repeater and a TV repeater.
FIG. 6 is a block diagram showing a configuration of a broadcast signal retransmission system in a tunnel.
[Explanation of symbols]
2 ... Train radio equipment, 10 ... Control station, 12 ... Radio base station, 14 ... Communication line, 16 ... Approach line, 18 ... Radio repeater, 30 ... Receiving equipment, 31 ... Regenerative repeater, 32 ... TV base station , 34, 36 ... optical cable, 38 ... TV repeater, 40 ... coaxial cable, 41 ... receiving antenna, 42, 62 ... electric amplifier, 44 ... distributor, 46, 56, 64 ... optical transmitter, 48, 50, 58 ... Optical amplifier, 52, 68 ... Optical receiver, 54 ... Demodulator, 62, 72, 74, 76 ... Electrical amplifier, 66 ... Optical splitter, 74 ... Distributor, 78 ... Mixer.

Claims

Receiving means for receiving a broadcast signal;
By outputting the broadcast signal received by the receiving means to a leaky coaxial cable laid along the traveling path of the mobile object, the broadcast signal is transmitted wirelessly from the leaky coaxial cable toward the traveling path. Output means for transmission;
Transmission means for transmitting the broadcast signal received by the receiving means to the output means;
A broadcast signal retransmission system for a mobile unit comprising:
A plurality of leaky coaxial cables having a length capable of transmitting a broadcast signal output from the output means are continuously laid on the travel path,
The receiving means is configured to convert the received broadcast signal into an optical signal and output the optical signal,
The output means is arranged in a distributed manner along the travel path corresponding to the plurality of leaky coaxial cables, and the plurality of output means conducts the broadcast signal along the travel path. Grouped for each distance that can be transmitted in the state of an electrical signal through an electrical transmission line consisting of wires,
The transmission means includes
A plurality of relay means that are dispersedly arranged along the travel path in one group for each group of the output means, and convert an optical signal transmitted from the receiving means into a broadcast signal composed of an electrical signal;
An optical transmission means comprising a plurality of optical transmission paths for transmitting the optical signals output from the receiving means to the relay means;
An electrical transmission means comprising a plurality of electrical transmission paths for transmitting the broadcast signal converted from the optical signal to the electrical signal by each relay means to the output means of the group corresponding to each relay means;
With
The plurality of relay means are grouped into a plurality along the travel path,
One of the relay means constituting each group receives an optical signal transmitted from the receiving means via a first optical transmission line as the optical transmission means, and converts the optical signal into an electrical signal. The base station transmits the converted optical signal to another relay means in the same group via the second optical transmission line as the optical transmission means. ,
The relay means other than the base station constituting each group takes in the optical signal flowing through the second optical transmission line via the optical branching means, and the optical signal is grouped via the second optical transmission line. A broadcast signal retransmitting system for a mobile unit , characterized by transmitting to the relay means at the end of the mobile unit .

Optical signals transmitted from the receiving means to the base stations of each group via the first optical transmission path are transmitted via the second optical transmission path from the base station to relay means other than the base station. 2. The broadcast signal retransmission system for mobile units according to claim 1, wherein the wavelength is longer than the optical signal to be transmitted.

  Receiving means for receiving a broadcast signal;
  By outputting the broadcast signal received by the receiving means to a leaky coaxial cable laid along the traveling path of the mobile object, the broadcast signal is transmitted wirelessly from the leaky coaxial cable toward the traveling path. Output means for transmission;
  Transmission means for transmitting the broadcast signal received by the receiving means to the output means;
  A broadcast signal retransmission system for a mobile unit comprising:
  A plurality of leaky coaxial cables having a length capable of transmitting the broadcast signal output from the output means are continuously laid on the travel path,
  The receiving means is configured to convert the received broadcast signal into an optical signal and output the optical signal,
  The output means is arranged in a distributed manner along the travel path corresponding to the plurality of leaky coaxial cables, and the plurality of output means conducts the broadcast signal along the travel path. Grouped for each distance that can be transmitted in the state of an electrical signal via an electrical transmission line consisting of wires. ,
  The transmission means includes
  A plurality of relay means that are dispersedly arranged along the travel path in one group for each group of the output means, and convert an optical signal transmitted from the receiving means into a broadcast signal composed of an electrical signal;
  An optical transmission means comprising a plurality of optical transmission paths for transmitting the optical signals output from the receiving means to the relay means;
  An electrical transmission means comprising a plurality of electrical transmission paths for transmitting the broadcast signal converted from the optical signal to the electrical signal by each relay means to the output means of the group corresponding to each relay means;
  With
  The plurality of relay means are grouped into a plurality along the travel path,
  One of the relay means constituting each group receives an optical signal transmitted from the receiving means via a first optical transmission line as the optical transmission means, and converts the optical signal into an electrical signal. The base station transmits the converted optical signal to another relay means in the same group via the second optical transmission line as the optical transmission means. ,
  Optical signals transmitted from the receiving means to the base stations of each group via the first optical transmission path are transmitted via the second optical transmission path from the base station to relay means other than the base station. A broadcast signal re-transmission system for mobile objects, characterized in that the wavelength is longer than the optical signal to be transmitted.

A regenerative repeater that demodulates and remodulates the broadcast signal is disposed on the travel path for each distance that the optical signal can be transmitted through the first optical transmission path, starting from the receiving means. ,
The regenerative relay means acquires the optical signal transmitted from the receiving means via the first optical transmission line, converts the optical signal into a broadcast signal composed of the electrical signal, and demodulates the broadcast signal once. By doing so, the broadcast signal is reproduced, the reproduced broadcast signal is converted into an optical signal, and the optical signal is separated from the receiving unit via the first optical transmission line than the reproduction relay unit. 4. The mobile broadcast signal re-transmission system according to claim 2, wherein transmission is performed to the regenerative repeater and a base station around the regenerative repeater.

The leaky coaxial cable is a leaky coaxial cable for train radio laid along a track,
The output means is disposed at a connection portion between a train radio transmission device and a leaky coaxial cable, and mixes a signal for wireless communication flowing through the connection portion and a broadcast signal acquired through the transmission means. The mobile broadcast signal retransmission system according to any one of claims 1 to 4, further comprising: means.

6. The mobile broadcast signal retransmission system according to claim 5, wherein the output means includes amplification means for amplifying a broadcast signal acquired via the transmission means and outputting the amplified signal to the mixing means.

  Receiving means for receiving a broadcast signal;
  By outputting the broadcast signal received by the receiving means to a leaky coaxial cable laid along the traveling path of the mobile object, the broadcast signal is transmitted wirelessly from the leaky coaxial cable toward the traveling path. Output means for transmission;
  Transmission means for transmitting the broadcast signal received by the receiving means to the output means;
  A broadcast signal retransmission system for a mobile unit comprising:
  The leaky coaxial cable is a leaky coaxial cable for train radio laid along a track,
  The output means is disposed at a connection portion between a train radio transmission device and a leaky coaxial cable, and mixes a signal for wireless communication flowing through the connection portion and a broadcast signal acquired through the transmission means. A broadcast signal retransmitting system for a mobile unit, characterized by comprising means.

8. The mobile broadcast signal retransmission system according to claim 7, wherein the output means includes amplification means for amplifying a broadcast signal acquired via the transmission means and outputting the amplified signal to the mixing means.

  A plurality of leaky coaxial cables having a length capable of transmitting the broadcast signal output from the output means are continuously laid on the travel path,
  The output means is arranged correspondingly to the plurality of leaky coaxial cables and is distributed in a plurality along the travel path,
  9. The mobile broadcast signal retransmission system according to claim 7, wherein the transmission unit transmits the broadcast signal received by the reception unit to the output units.