JP3957562B2 - Multi-access switching method - Google Patents

Description

すなわち、先発地球局のＱｃ信号重畳から衛星上にて先発地球局の送信信号が切れる時間と、先発地球局のＱｃ信号重畳から次発地球局の送信信号が衛星へ到達する時間とが一致するように、先発地球局のＱｃ信号の重畳から先発地球局の送信をＯＦＦにするまでの時間（Ｄｓ）と次発地球局がＱｃ信号を受信し次発地球局が送信を開始するまでの時間（Ｄｒ）を設定する必要がある。
【００１２】
送信局の切替を行う際には、上記の関係式を満たすことを前提とし、先発地球局では、Ｑｃ信号発生器１１よりＱｃ信号を生成し、Ｑｃ信号重畳器１３によりＱｃ信号が放送信号に重畳した後、遅延時間タイマー１２によりＤｓ時間の経過後に送信機２を停止する。次発地球局では、先発地球局が衛星経由で送信したＱｃ信号を、Ｑｃ検出器６２にてＱｃ信号を重畳した時刻からＴｓ＋Ｔｒ時間後に検出し、遅延時間タイマー６３にてＤｒ時間の経過後に送信機５２の送信を開始する。
【００１３】
しかしながら、上述における衛星から地球局（先発地球局及び次発地球局）間の信号の伝搬時間は衛星の軌道により変化するため、正確な時間を把握する事が困難であった。その結果、信号の重なりや切れ間が生じて画像が乱れていた。特にスクランブル放送では、受信画像を再生する上で連続したデータの受信が必要不可欠であり、当該データの重なりや切れ間の発生により再生ができず受信画像に数秒の乱れが生じる問題が指摘されている。
【００１４】
これらを解決する手段として、特開２００１−１２７６８３号公報に記載される発明では、次の方策が採られている。図９及び図１０に他の発明案件のマルチアクセス切替系統図とタイムチャートを示す。
【００１５】
概略的には、３つのステップに大別され、ステップ１では、先発地球局と衛星間における信号伝搬時間（２Ｔｓ）の測定を行い、ステップ２では、ステップ１で測定した信号伝搬時間（２Ｔｓ）に当該伝搬時間を放送波に重畳する時刻から放送を停止するまでの予め設定した所定時間を加算して得た放送停止時間と、前記重畳時刻とからなる切替情報を次発地球局へ送信し、所定時間経過後（Ｄｓ）に先発地球局からの送信をＯＦＦにする処理を行う。また、ステップ３では、次発地球局において、先発地球局が送信したマルチアクセス切替に必要な情報を基に送信開始時刻を算出し送信をＤｒ時間経過後に送信を開始する。なお、上記のマルチアクセスには、先発地球局と次発地球局との間で時刻の同期がとれている必要がある。
【００１６】
【発明が解決しようとする課題】
しかしながら、特開２００１−１２７６８３号公報に記載される発明では、先発局では、局切替前にパイロット信号(Qp)を送信波に重畳し、衛星〜先発局間の伝搬時間（Ts）を測定し、かつ、局切替用タイミング信号（Qc）と切替えのための情報を送信波に重畳する必要があった。
【００１７】
一方、次発局では、衛星を経由して送られてきたQc信号の受信時刻(T2)と先発局にて放送波に重畳された情報を基に、Qc信号受信〜Tx ONまでの時間Dr）値を演算しTx ON制御を行う必要があった。
【００１８】
更に、先発局と次発局間で時刻を正確に合わす必要があり、時刻同期のため設備が必要であった。
【００１９】
そこで、本発明においては、放送波に制御信号を重畳する必要がなく、特殊な装置を必要としないマルチアクセス切替方式の提供を目的とする。
【００２０】
【課題を解決するための手段】
本発明によれば、衛星、及び衛星と相互に通信可能な複数の地球局から構成され、前記複数の地球局のうち衛星と回線接続中にある先発地球局から、次に衛星と回線接続を行う次発地球局に切り替えて接続する衛星通信システムのマルチアクセス切替方法において、前記先発地球局は、第１周波数の信号を前記衛星に向けて送信し、衛星から折り返えされた前記第１周波数の信号の受信タイミングで第２周波数の信号を衛星に向けて送信し、前記次発地球局は、前記衛星を介して前記第１周波数の信号を受信し、この受信タイミングで第３周波数の信号を前記衛星に向けて送信し、前記先発地球局は、前記衛星を介して前記第３周波数の信号を受信するタイミングで放送を停止し、また前記次発地球局は、前記衛星を介して前記第２周波数の信号を受信するタイミングで放送を開始することを特徴とするマルチアクセス切替方法を得ることができる。
【００２１】
【発明の実施の形態】
以下、図面を参照して、この発明の好適な実施の形態を例示的に説明する。ただし、この実施の形態に記載されている構成部品の寸法、材質、その相対配置などは、特に特定的な記載がない限りは、この発明の範囲をそれらのみに限定する趣旨のものではない。
【００２２】
図１に、本発明の実施形態に係るマルチアクセス切替方式の概念を示す。本実施形態では、ＴＶ信号とは別に、衛星〜地球局間の信号伝搬時間を自動的に補正するための３つの制御用信号（無変調波）を使用する。
【００２３】
図２は、当該３つの制御用信号が衛星を介して地球局間を伝搬する際の接続系統を示すものである。先発局は制御信号ＴＸ ｆ１並びにＴＸ ｆ２を送信し、次発局はＴＸ ｆ３を送信する。ＴＸ ｆ２及びＴＸ ｆ３は、ＴＸ ｆ１の衛星経由の折り返し信号ＲＸ ｆ１を元に生成される。
【００２４】
図３および図４には、時間的起点である先発局の制御信号ＴＸ ｆ１送信（Ｔ１）から先発局のＴＶ信号が衛星上で断になる時間（Ｔ２）と、次発局のＴＶ信号が衛星上でＯＮになる時間（Ｔ２）までの制御、ＴＶ信号の流れを示す。
【００２５】
図５は、先発局のＴＸ ｆ１送信から衛星上で放送波が切り替わるまでの制御信号並びに放送波の時間的流れを示す。
【００２６】
図６には、本実施形態のマルチアクセス切替方式のブロック図を示す。システムに応じてＮ局で構成される地球局を順次切り替えることで、衛星とのマルチアクセスを行っているが、ここでは、説明を簡略化するため、先発地球局と次発地球局で構成される二局の地球局を示している。
【００２７】
先発地球局は、放送波を衛星へ指向させるためのアンテナ１と、放送信号並びに制御用信号を周波数変換および増幅した後にアンテナ１へ導く送信機２と、アンテナ１にて集束した衛星からの放送波並びに制御信号を低雑音増幅し、周波数変換する受信機３と、放送信号を送出する放送設備４、放送用信号並びに制御用信号ｆ１、ｆ２を合成する合成器５、受信機３からの信号を分岐する分配器６、制御用信号ｆ１を発振するf1信号発生器７、分配器６から出力される制御用信号ｆ１を周波数変換し制御用信号ｆ２を生成する周波数変換器８、分配器６から出力される制御信号ｆ３を検出し、送信ＳＷ１０にＴＸ ＯＦＦ制御信号を送出するｆ３検出器９、ｆ３検出器９からのＴＸ ＯＦＦ制御信号を受けて放送波を断にする送信ＳＷ１０から構成される。
【００２８】
一方、次発地球局は、放送波並びに制御用信号を衛星へ指向させるためのアンテナ５１と、放送信号並びに制御用信号を周波数変換および増幅した後にアンテナ５１へ導く送信機５２と、アンテナ５１にて集束した衛星からの放送波並びに制御用信号を低雑音増幅し、周波数変換及び復調する受信機５３と、放送信号を送出する放送設備５４と、放送用信号並びに制御用信号ｆ３を合成する合成器５５、受信機５３からの信号を分岐する分配器５６、分配器５６から出力される制御用信号ｆ１を周波数変換し制御用信号ｆ３を生成する周波数変換器５７、分配器６から出力される制御信号ｆ２を検出し、送信ＳＷ５９にＴＸ ＯＮ制御信号を送出するｆ２検出器５８、ｆ２検出器５８からのＴＸ ＯＮ制御信号を受けて放送波を断にする送信ＳＷ５９から構成される。
【００２９】
図５に、本発明のマルチアクセス切り替え方式のタイムチャートを示す。タイムチャートに記載の時間を表す略語の意味を以下に示す。Ｔ１は、先発局の制御信号ＴＸ ｆ１送信時の時刻である。Ｔ２は、衛星の中継器上で先発局送信のＴＶ信号が断となる時刻である。また、次発局送信のＴＶ信号がＯＮとなる時刻でもある。Ｔｓは、先発局と衛星間の信号の伝搬時間である。Ｔｒは、次発局と衛星間の信号の伝搬時間である。
【００３０】
図５のタイムチャート並びに図６系統図を用いて、時間的流れに従い、ＴＶ信号を先発局の送信から次発局の送信に切り替える場合の動作について説明する。
【００３１】
マルチアクセス切替開始時には、先発局はｆ１信号発生器７により制御信号ｆ１を発生させる。制御信号ｆ１は合成器５を経由し送信機２にて周波数変換並びに電力増幅されアンテナ１にて衛星に向けて送信される。先発局より送信された制御用信号ＴＸ ｆ１は衛星にて周波数変換され、受信信号ＲＸ ｆ１として地球局へ配信される。
【００３２】
次発局に送られた制御用信号ＲＸ ｆ１はアンテナ５１で集束され、受信機５３に低雑音増幅並びに周波数変換され、分配器５６を経由して周波数変換器５７に入力される。 周波数変換器５７は、入力された制御用信号ｆ１を周波数変換し制御用信号ｆ３を生成する。制御用信号ｆ３は合成器５５を経由して送信機５２にて周波数変換・電力増幅されアンテナ５１より制御用信号ＴＸ ｆ３として衛星へ送信される。 制御用信号ＴＸ ｆ３は衛星にて周波数変換され受信信号ＲＸ ｆ３として先発局へ送られる。制御用信号ｆ３はアンテナ１にて集束され受信機３にて低雑音増幅・周波数変換後、分配器６に送られ、ｆ３検出器９に入力される。ｆ３検出器９は、制御用信号ｆ３を検出すると送信ＳＷ１０へＴＸ ＯＦＦ制御信号を送る。送信ＳＷ１０は、ＴＸ ＯＦＦ制御信号を受信すると放送波の送信を断にする。
【００３３】
一方、先発局に送られた制御用信号ＲＸ ｆ１はアンテナ１で集束され、受信機３に低雑音増幅並びに周波数変換され、分配器６を経由して周波数変換器８に入力される。周波数変換器８は、入力された制御用信号ｆ１を周波数変換し制御用信号ｆ２を生成する。制御用信号ｆ２は合成器５を経由して送信機２にて周波数変換・電力増幅されアンテナ１より制御用信号ＴＸ ｆ２として衛星へ送信される。 制御用信号ＴＸ ｆ２は衛星にて周波数変換され受信信号ＲＸ ｆ２として次発局へ送られる。制御用信号ｆ２はアンテナ５１にて信号を集束され受信機５３にて低雑音増幅・周波数変換後、分配器５６に送られ、ｆ２検出器５８に入力される。ｆ２検出器５８は、制御用信号ｆ２を受信すると送信ＳＷ５９へＴＸＯＮ制御信号を送る。送信ＳＷ５９は、ＴＸ ＯＮ制御信号を受信すると放送波の送信をＯＮにする。
【００３４】
先発局の制御用信号ｆ１送信の時刻 Ｔ１から先発局の放送波が衛星の中継器上で断になるまでの時刻Ｔ２までの時間は、制御用信号ｆ１が衛星を経由して次発局へ送られ、制御用信号ｆ３として先発局に帰還するまでの時間に先発局から衛星までの信号の伝搬時間Ｔｓを加えた時間であり、ＴｓとＴｒの組み合わせによる時間（３Ｔｓ＋２Ｔｒ）となる。
【００３５】
また、先発局の制御用信号ｆ１送信の時刻 Ｔ１から次発局の放送波が衛星の中継器に到達するまでの時刻Ｔ２までの時間は、制御用信号ｆ１が衛星を経由して先発局へ戻され、制御用信号ｆ２として次発局に送られる時間に次発局から衛星までの信号の伝搬時間Ｔrを加えた時間であり、同様に、ＴｓとＴｒの組み合わせによる時間（３Ｔｓ＋２Ｔｒ）となる。
【００３６】
この結果、Ｔｓ、ＴｒがＴ１からＴ２の期間（静止衛星の場合、０．６秒）に変化しない限り、精度の高いマルチアクセス切替が実現できる。
【００３７】
【発明の効果】
本発明によれば、パイロット信号、Qc信号および切替え時間に関する情報を放送波に重畳すること無しに送信局の切替えが可能となり、また、衛星の軌道により変化する衛星〜地球局間の信号伝搬時間が変化しても精度の高い切替えが可能となる。その結果、放送波の加工並びに放送信号にＱｐ信号、Qc信号および時刻情報の重畳・抽出を行うマルチアクセス装置を必要とせず、放送波の形式（ＮＴＳＣ、ＭＵＳＥ、デジタル等）に関系なく精度の高い局切替えが可能となる。
【００３８】
また、複数の地球局による切替えが可能となるばかりでなく、衛星〜地球局間の遅延時間が自動的に補正されるため、あらゆる衛星（静止衛星、低軌道衛星等）を用いた時分割通信のガード時間帯を狭くすることが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係るマルチアクセス切替方式の概念図である。
【図２】本発明の一実施の形態に係るマルチアクセス切替方式の信号接続図である。
【図３】本発明の一実施の形態に係るマルチアクセス切替方式の先発局のＴＸ ＯＦＦまでの制御回線ルートである。
【図４】本発明の一実施の形態に係るマルチアクセス切替方式の次発局のＴＸ ＯＮまでの制御回線ルートである。
【図５】本発明の一実施の形態に係るマルチアクセス切替方式のタイムチャートである。
【図６】本発明の一実施の形態に係るマルチアクセス切替方式の系統図である。
【図７】従来方式のマルチアクセスの切り替え系統図である。
【図８】従来方式のマルチアクセスの切り替えタイムチャートである。
【図９】他の発明案件のマルチアクセス切替系統図である。
【図１０】他の発明案件のマルチアクセス切替えタイムチャートである。
【符号の説明】
１，５１ アンテナ
２，５２ 送信機
３，５３ 受信機
４，５４ 放送設備
５，５５ 合成器
６，５６ 分配器
７ ｆ１制御信号発生器
８，５７ 周波数変換器
９ ｆ３検出器
５８ ｆ２検出器
１０、５９ 送信ＳＷ
１１ Ｑｃ信号発生器
１２ Ｄｓ遅延時間タイマー
１３ 重畳器
６１ 分配器
６２ Ｑｃ検出器
６３ Ｄｒ遅延時間タイマー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission station switching system for satellite communication and satellite broadcasting, and more particularly to a system for switching stations without interruption.
[0002]
[Prior art]
In satellite broadcasting, broadcast waves are transmitted from the earth station to the satellite and distributed to general viewing stations scattered over a wider area than the satellite. The program is switched by switching the transmitting earth station. In the case of satellite broadcasting, programs produced locally are sent to the central broadcasting earth station using other transmission channels, and it is not necessary to send broadcast waves from this earth station to the satellite. It is possible to transmit broadcast waves directly to the satellite.
[0003]
In order to perform this switching so as not to give the general viewer a sense of incongruity, it is necessary to control the transmission ON / OFF time between the earth stations so that signals do not overlap or break on the satellite.
[0004]
FIG. 7 shows a system of a conventional multi-access switching system (Japanese Patent Publication No. 59-2411 broadcast satellite program switching system).
In such a multi-access switching system, multi-access with a satellite is performed by sequentially switching earth stations composed of N stations in accordance with the system. Here, in order to simplify the explanation, the starting earth station As an example, two earth stations will be described.
[0005]
The starting earth station is a station that is transmitting a broadcast wave, an antenna 1 for directing the broadcast wave to a satellite, a transmitter 2 that guides the broadcast signal to the antenna 1 after modulating / frequency converting and amplifying the broadcast signal, and an antenna The receiver 3 that amplifies the broadcast wave from the satellite focused at 1 with low noise amplification, frequency conversion and demodulation, and the multi-access device 4 that controls the transmission OFF time so as not to overlap or break the signal on the satellite. And a broadcast facility 5 for transmitting broadcast signals. The multi-access device 4 also includes a Qc signal generator 11 that generates a timing signal (hereinafter referred to as a Qc signal) for multi-access switching, and a delay time timer 12 that controls the time from Qc signal superposition to transmission OFF. And a Qc signal superimposing unit 13 for superimposing the Qc signal on the broadcast signal.
[0006]
The next earth station, on the other hand, transmits an antenna 51 for directing a broadcast wave to the satellite, a transmitter 52 that modulates the broadcast signal, converts the frequency, and amplifies the signal, then guides the antenna 51. A receiver 53 that amplifies a broadcast wave with low noise, frequency-converts and demodulates, a multi-access device 54 that controls transmission ON time so that signals do not overlap or break on a satellite, and broadcasting equipment that transmits a broadcast signal 55. The multi-access device 54 includes a distributor 61 that distributes a received broadcast signal, a Qc detector 62 that detects a Qc signal from the broadcast signal, and a delay time timer 63 that controls the time from Qc reception to Tx ON. The
[0007]
A plurality of earth stations to which such a multi-access switching method is applied do not have to be provided with a difference in device configuration because each of them plays the role of the first earth station and the next earth station according to the TDMA transmission timing. In the present embodiment, in order to facilitate explanation when switching broadcasting from the previous earth station being transmitted to the next earth station waiting for transmission, it is necessary for the first earth station and the next earth station at a certain broadcast timing. Only the minimum required components are shown.
[0008]
Next, the operation of the multi-access switching method shown in FIG. 7 will be described with reference to the time chart shown in FIG. The time chart shown in FIG. 7 is a case where the transmission of the preceding earth station is stopped and the transmission is switched to the next earth station waiting.
[0009]
In order to perform switching so that there is no overlap or break in the transmission signal on the satellite, the time when the transmission signal of the previous earth station cuts off on the satellite from the Qc signal superposition of the previous earth station, and the Qc of the previous earth station The time required for the transmission signal of the next earth station to reach the satellite from the signal superposition needs to coincide.
[0010]
Specifically, it is necessary to satisfy the following relational expression with reference to the superimposed time of the Qc signal in the preceding earth station. Here, Ts is the propagation time of the signal between the preceding earth station and the satellite, and refers to the time until the preceding earth station superimposes the Qc signal and the Qc signal reaches the satellite. Ds is the time from the Qc signal superposition of the previous earth station until the transmission signal is stopped (TXOFF). Tr is the propagation time of the signal between the next earth station and the satellite, and indicates the time until the next earth station receives the Qc signal from the satellite. Dr is the time from when the next earth station receives the Qc signal until the transmitter 52 starts transmission (TX ON).
[0011]
[Expression 1]

That is, the time when the transmission signal of the previous earth station is cut off on the satellite from the Qc signal superposition of the previous earth station coincides with the time when the transmission signal of the next earth station reaches the satellite from the Qc signal superposition of the previous earth station. As described above, the time (Ds) from the superposition of the Qc signal of the preceding earth station until the transmission of the preceding earth station is turned off and the time from when the next earth station receives the Qc signal and the next earth station starts transmission. (Dr) needs to be set.
[0012]
When switching transmission stations, it is assumed that the above relational expression is satisfied, and the preceding earth station generates a Qc signal from the Qc signal generator 11, and the Qc signal superimposing unit 13 converts the Qc signal into a broadcast signal. After the superposition, the transmitter 2 is stopped after the Ds time has elapsed by the delay time timer 12. At the next earth station, the Qc signal transmitted from the previous earth station via the satellite is detected after Ts + Tr time from the time when the Qc signal is superimposed by the Qc detector 62, and transmitted after Dr time has elapsed by the delay time timer 63. The transmission of the machine 52 is started.
[0013]
However, since the signal propagation time from the satellite to the earth station (the first earth station and the next earth station) varies depending on the orbit of the satellite, it is difficult to grasp the accurate time. As a result, overlapping and gaps in signals occurred, and the image was distorted. In particular, in scrambled broadcasting, it is indispensable to receive continuous data in order to reproduce a received image, and it has been pointed out that the received image cannot be reproduced due to the overlap or breakage of the data, and the received image is disturbed for several seconds. .
[0014]
As means for solving these problems, the following measures are taken in the invention described in JP-A-2001-127683. 9 and 10 show a multi-access switching system diagram and a time chart of another invention item.
[0015]
In general, it is roughly divided into three steps. In step 1, the signal propagation time (2Ts) between the starting earth station and the satellite is measured, and in step 2, the signal propagation time (2Ts) measured in step 1 is measured. The switching information consisting of the broadcast stop time obtained by adding a predetermined time from when the propagation time is superimposed on the broadcast wave to when the broadcast is stopped and the superposition time is transmitted to the next earth station. Then, after a predetermined time has elapsed (Ds), processing for turning off transmission from the preceding earth station is performed. In step 3, the next earth station calculates the transmission start time based on the information necessary for multi-access switching transmitted by the previous earth station, and starts transmission after the Dr time has elapsed. Note that the above multi-access requires time synchronization between the preceding earth station and the next earth station.
[0016]
[Problems to be solved by the invention]
However, in the invention described in Japanese Patent Application Laid-Open No. 2001-127683, the starting station superimposes the pilot signal (Qp) on the transmission wave before station switching, and measures the propagation time (Ts) between the satellite and the starting station. In addition, it is necessary to superimpose the station switching timing signal (Qc) and switching information on the transmission wave.
[0017]
On the other hand, at the next station, based on the reception time (T2) of the Qc signal sent via the satellite and the information superimposed on the broadcast wave at the previous station, the time from the Qc signal reception to Tx ON Dr ) It was necessary to calculate the value and perform Tx ON control.
[0018]
Furthermore, it is necessary to accurately set the time between the preceding station and the next station, and equipment is required for time synchronization.
[0019]
Accordingly, an object of the present invention is to provide a multi-access switching method that does not require a control signal to be superimposed on a broadcast wave and does not require a special device.
[0020]
[Means for Solving the Problems]
According to the present invention, a satellite and a plurality of earth stations that can communicate with each other are connected, and a satellite is connected to a satellite from a starting earth station that is currently connected to the satellite among the plurality of earth stations. In the multi-access switching method of the satellite communication system that is switched to and connected to the next earth station to be performed, the first earth station transmits a signal having a first frequency to the satellite and is returned from the satellite. A second frequency signal is transmitted to the satellite at the reception timing of the frequency signal, and the next earth station receives the first frequency signal via the satellite, and the third frequency signal is received at the reception timing. A signal is transmitted to the satellite, the first earth station stops broadcasting at a timing when the third frequency signal is received via the satellite, and the next earth station is transmitted via the satellite. Of the second frequency It is possible to obtain a multi-access switching method characterized by initiating the broadcast timing of receiving the item.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings. However, the dimensions, materials, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.
[0022]
FIG. 1 shows the concept of the multi-access switching method according to the embodiment of the present invention. In this embodiment, three control signals (unmodulated waves) for automatically correcting the signal propagation time between the satellite and the earth station are used separately from the TV signal.
[0023]
FIG. 2 shows a connection system when the three control signals propagate between the earth stations via the satellite. The preceding station transmits control signals TX f1 and TX f2, and the next station transmits TX f3. TX f2 and TX f3 are generated based on the return signal RX f1 via the satellite of TX f1.
[0024]
3 and FIG. 4, the time (T2) when the TV signal of the preceding station is cut off on the satellite from the control signal TX f1 transmission (T1) of the preceding station, which is the time starting point, and the TV signal of the next originating station are shown. The flow of control and TV signal up to the time (T2) when the satellite is turned on is shown.
[0025]
FIG. 5 shows a control signal and a temporal flow of the broadcast wave from the TX f1 transmission of the preceding station until the broadcast wave is switched on the satellite.
[0026]
FIG. 6 shows a block diagram of the multi-access switching method of this embodiment. Multi-access with the satellite is performed by sequentially switching the earth station composed of N stations according to the system, but here it is composed of the first earth station and the next earth station to simplify the explanation. Shows two earth stations.
[0027]
The first earth station transmits an antenna 1 for directing broadcast waves to the satellite, a transmitter 2 that converts the frequency of the broadcast signal and the control signal to the antenna 1 after frequency conversion and amplification, and broadcasts from the satellite focused by the antenna 1 A signal from a receiver 3 that amplifies a wave and a control signal with low noise and converts the frequency, a broadcasting facility 4 that transmits a broadcast signal, a synthesizer 5 that synthesizes the broadcast signal and the control signals f1 and f2, , A frequency converter 8 that oscillates the control signal f1, a frequency converter 8 that generates a control signal f2 by converting the frequency of the control signal f1 output from the distributor 6, and a distributor 6 The control signal f3 output from the transmission SW10 is detected, the TXOFF control signal is transmitted to the transmission SW10, and the TXSW control signal from the f3 detector 9 is received and the transmission SW10 is configured to cut off the broadcast wave. Made.
[0028]
On the other hand, the next earth station transmits an antenna 51 for directing the broadcast wave and the control signal to the satellite, a transmitter 52 for converting the broadcast signal and the control signal to frequency 51 Receiver 53 for low noise amplification, frequency conversion and demodulation, broadcast equipment 54 for transmitting broadcast signals, and synthesis signal for synthesizing broadcast signals and control signal f3. 55, a divider 56 for branching the signal from the receiver 53, a frequency converter 57 for generating a control signal f3 by converting the frequency of the control signal f1 output from the divider 56, and the divider 6 for output. The transmission signal S2 that detects the control signal f2 and sends the TX ON control signal to the transmission SW 59, and receives the TX ON control signal from the f2 detector 58 and cuts off the broadcast wave. It consists of 59.
[0029]
FIG. 5 shows a time chart of the multi-access switching method of the present invention. The meanings of the abbreviations representing the times described in the time chart are shown below. T1 is the time when the control signal TX f1 of the preceding station is transmitted. T2 is the time when the TV signal transmitted from the starting station is cut off on the satellite repeater. It is also the time when the TV signal for the next station transmission turns on. Ts is a signal propagation time between the starting station and the satellite. Tr is the signal propagation time between the next station and the satellite.
[0030]
With reference to the time chart of FIG. 5 and the system diagram of FIG. 6, the operation when the TV signal is switched from the transmission of the previous station to the transmission of the next station will be described according to the time flow.
[0031]
When the multi-access switching is started, the preceding station generates the control signal f1 by the f1 signal generator 7. The control signal f1 is frequency-converted and power-amplified by the transmitter 2 via the synthesizer 5, and transmitted to the satellite by the antenna 1. The control signal TX f1 transmitted from the preceding station is frequency-converted by the satellite and distributed to the earth station as the received signal RX f1.
[0032]
The control signal RX f1 sent to the next transmitting station is focused by the antenna 51, subjected to low noise amplification and frequency conversion by the receiver 53, and input to the frequency converter 57 via the distributor 56. The frequency converter 57 converts the frequency of the input control signal f1 to generate a control signal f3. The control signal f3 is frequency-converted and power-amplified by the transmitter 52 via the synthesizer 55, and transmitted from the antenna 51 to the satellite as the control signal TX f3. The control signal TX f3 is frequency-converted by the satellite and sent to the preceding station as a reception signal RX f3. The control signal f3 is focused by the antenna 1, is subjected to low noise amplification and frequency conversion by the receiver 3, is sent to the distributor 6, and is input to the f3 detector 9. When detecting the control signal f3, the f3 detector 9 sends a TX OFF control signal to the transmission SW 10. When the transmission SW 10 receives the TX OFF control signal, the transmission SW 10 stops the transmission of the broadcast wave.
[0033]
On the other hand, the control signal RX f1 sent to the preceding station is focused by the antenna 1, subjected to low noise amplification and frequency conversion by the receiver 3, and input to the frequency converter 8 via the distributor 6. The frequency converter 8 frequency-converts the input control signal f1 to generate a control signal f2. The control signal f2 is frequency-converted and power-amplified by the transmitter 2 via the synthesizer 5, and transmitted from the antenna 1 to the satellite as the control signal TX f2. The control signal TX f2 is frequency-converted by the satellite and sent to the next station as a received signal RX f2. The control signal f2 is focused by the antenna 51, amplified by the low noise and frequency converted by the receiver 53, sent to the distributor 56, and input to the f2 detector 58. When receiving the control signal f2, the f2 detector 58 sends a TXON control signal to the transmission SW 59. When receiving the TX ON control signal, the transmission SW 59 turns on the transmission of the broadcast wave.
[0034]
The time from transmission time T1 of the control signal f1 of the previous station to time T2 until the broadcast wave of the previous station is cut off on the satellite repeater is transmitted from the control signal f1 to the next transmission station via the satellite. This is a time obtained by adding the signal propagation time Ts from the preceding station to the satellite to the time until it is sent back to the preceding station as the control signal f3, and is a time (3Ts + 2Tr) by a combination of Ts and Tr.
[0035]
Further, the time from the time T1 at which the control signal f1 of the preceding station is transmitted to the time T2 until the broadcast wave of the next station arrives at the satellite repeater, the control signal f1 passes through the satellite to the preceding station. This is a time obtained by adding the signal propagation time Tr from the next source station to the satellite to the time sent back to the next source station as the control signal f2, and is similarly a time (3Ts + 2Tr) by a combination of Ts and Tr. .
[0036]
As a result, high-accuracy multi-access switching can be realized as long as Ts and Tr do not change during the period from T1 to T2 (0.6 seconds for a geostationary satellite).
[0037]
【The invention's effect】
According to the present invention, the transmission station can be switched without superimposing information on the pilot signal, the Qc signal, and the switching time on the broadcast wave, and the signal propagation time between the satellite and the earth station that changes depending on the orbit of the satellite. Even if changes, high-precision switching is possible. As a result, there is no need for a multi-access device for processing broadcast waves and superimposing / extracting Qp signals, Qc signals and time information on broadcast signals, and accuracy regardless of the broadcast wave format (NTSC, MUSE, digital, etc.) High station switching is possible.
[0038]
In addition to being able to switch between multiple earth stations, the delay time between the satellite and the earth station is automatically corrected, so time-division communication using any satellite (stationary satellite, low orbit satellite, etc.) It is possible to narrow the guard time zone.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a multi-access switching method according to an embodiment of the present invention.
FIG. 2 is a signal connection diagram of a multi-access switching method according to an embodiment of the present invention.
FIG. 3 is a control line route up to TX OFF of a starting station in a multi-access switching method according to an embodiment of the present invention.
FIG. 4 is a control line route to TX ON of the next station of the multi-access switching method according to the embodiment of the present invention.
FIG. 5 is a time chart of a multi-access switching method according to an embodiment of the present invention.
FIG. 6 is a system diagram of a multi-access switching method according to an embodiment of the present invention.
FIG. 7 is a switching diagram of a conventional multi-access system.
FIG. 8 is a switching time chart of a conventional multi-access.
FIG. 9 is a multi-access switching system diagram of another invention item.
FIG. 10 is a multi-access switching time chart of another invention item.
[Explanation of symbols]
1, 51 Antenna 2, 52 Transmitter 3, 53 Receiver 4, 54 Broadcast equipment 5, 55 Synthesizer 6, 56 Divider 7 f1 Control signal generator 8, 57 Frequency converter 9 f3 detector 58 f2 detector 10 59 Transmission SW
11 Qc signal generator 12 Ds delay time timer 13 Superimposer 61 Distributor 62 Qc detector 63 Dr delay time timer

Claims (1)

Consists of a satellite and a plurality of earth stations that can communicate with each other, and from the first earth station that is connected to the satellite to the next earth station that is next connected to the satellite. In the multi-access switching method of the satellite communication system to be switched and connected,
The advance earth station transmits a first frequency signal toward the satellite, and transmits a second frequency signal toward the satellite at the reception timing of the first frequency signal returned from the satellite,
The next earth station receives the signal of the first frequency via the satellite, and transmits the signal of the third frequency toward the satellite at this reception timing,
The preceding earth station stops broadcasting at the timing of receiving the signal of the third frequency via the satellite, and the timing of the next earth station receiving the signal of the second frequency via the satellite A multi-access switching method characterized by starting broadcasting.

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