JPS62154882A - Carrier synchronizing circuit - Google Patents
Carrier synchronizing circuitInfo
- Publication number
- JPS62154882A JPS62154882A JP29417185A JP29417185A JPS62154882A JP S62154882 A JPS62154882 A JP S62154882A JP 29417185 A JP29417185 A JP 29417185A JP 29417185 A JP29417185 A JP 29417185A JP S62154882 A JPS62154882 A JP S62154882A
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- local oscillator
- video
- carrier
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明はＣＡＴＶシステム等に使用される搬送波同期回
路に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carrier synchronization circuit used in CATV systems and the like.
ＣＡＴＶシステムは、当初、難視聴対策の有効な手段と
して導入されてきたが、最近、電界強度の大きな都市部
において、新サービス提供の手段として使用されようと
している。このようなＣＡＴＶシステムは、上位局にお
いて放送波を受信して下位局にベースバンド伝送を行な
い、下位局においてベースバンド信号を放送波と同一チ
ャンネルに周波数変換して再送信するよう構成できるが
、放送波と再送信信号の搬送周波数が一致していないと
ビート障害が発生することが予想される。しかしながら
、従来、上記ビート障害に対する屏大手段は何ら提案さ
れていなかった。CATV systems were initially introduced as an effective means of countermeasures against viewing difficulties, but recently they are being used as a means of providing new services in urban areas where electric field strength is large. Such a CATV system can be configured such that an upper station receives a broadcast wave and transmits the baseband signal to a lower station, and the lower station converts the frequency of the baseband signal to the same channel as the broadcast wave and retransmits it. If the carrier frequencies of the broadcast wave and the retransmitted signal do not match, it is expected that beat disturbances will occur. However, conventionally, no measures to improve the above-mentioned beat disorder have been proposed.
本発明の搬送波同期回路は、上記問題を解決するために
、放送波め映ｆ４１搬送波と再送信の映像搬送波の周波
数を比較するための位相比較器を有し、この位相比較器
の出力で再送信の映像搬送波の周波数を制御して放送波
の映像搬送波の周波数に一致させた安定な再送信の映像
搬送波？得ている。In order to solve the above problem, the carrier synchronization circuit of the present invention has a phase comparator for comparing the frequencies of the broadcast wave image F41 carrier wave and the retransmission video carrier wave, and uses the output of this phase comparator to reproduce the frequency. A stable retransmission video carrier that controls the frequency of the transmitted video carrier to match the frequency of the broadcast video video carrier? It has gained.
次に本発明を図面？参照して詳細に説明す／Ｓ ６第１
図は本発明の搬送波同期回路の一実施例を示す。図に２
いて、映像信号入力端子１から入力される複合映像ベー
スバンド信号は変調器２で中間周波数に変換される。帯
域ろ波器３は変調信号から不要信号を除云して変調器４
に供給する。変調器４は放送波と同一のチャンネルの周
波数に変換して帯域ろ波器５に送り、ここで不要信号に
除去して装置出力端子６からＣＡＴＶ伝送路へ送用する
。一方、アンテナ等により受信した放送孜は放送波入力
端子７から入力された後、帯域ろ波器８で希望チャン坏
ルの信号が抽出されて変調器９に供給される。変調器９
はろ波器８の出を中間周波数に変換して帯域ろ波器１０
で不要波を除云して位相比較器１１に供給する。ここで
、この信号を基準信号と呼ぶ。一方、電圧制御型の第１
）ｆ７Ｊ部発振器１３の出力は２分配され、１つは変調
器２に入力されて周波数変換のための搬送波として使用
され、他の１つは位相比較器１１に入力されて前述の基
準信号と位相が比較される。比較出力のうち映像信号の
水平同期信号の時間の位相比較出力電圧だけがテンプル
ホールド１５でサンプリングされた後、ループフィルタ
１２を介して電圧制御型の第１局部発振器１３に制御信
号として供給される。これにより、基準信号すなわち、
端子７から入力した信号に同期した安定な発振周波数を
得ることができる。Next, drawing the invention? Please refer to and explain in detail/S 6 1st
The figure shows an embodiment of the carrier synchronization circuit of the present invention. Figure 2
A composite video baseband signal input from a video signal input terminal 1 is converted to an intermediate frequency by a modulator 2. The bandpass filter 3 removes unnecessary signals from the modulated signal and passes it to the modulator 4.
supply to. The modulator 4 converts the frequency of the broadcast wave to the same channel frequency and sends it to the bandpass filter 5, where it is removed as an unnecessary signal and sent from the device output terminal 6 to the CATV transmission line. On the other hand, a broadcast signal received by an antenna or the like is inputted from a broadcast wave input terminal 7, and then a signal of a desired channel is extracted by a bandpass filter 8 and supplied to a modulator 9. Modulator 9
converts the output of the filter 8 to an intermediate frequency and passes it through the bandpass filter 10
, removes unnecessary waves and supplies it to the phase comparator 11. Here, this signal is called a reference signal. On the other hand, the voltage-controlled first
) The output of the f7J part oscillator 13 is divided into two parts, one is input to the modulator 2 and used as a carrier wave for frequency conversion, and the other is input to the phase comparator 11 and is used as the reference signal and the above-mentioned reference signal. The phases are compared. Of the comparison outputs, only the phase comparison output voltage at the time of the horizontal synchronization signal of the video signal is sampled by the temple hold 15 and then supplied as a control signal to the voltage-controlled first local oscillator 13 via the loop filter 12. . This allows the reference signal, i.e.
A stable oscillation frequency synchronized with the signal input from the terminal 7 can be obtained.
なおサンプルホールド１５でサンプリングするためのサ
ンプリングパルスは、映像復調器１７で放送波の映像信
号を復調して水平同期パルス分離器１６により映像信号
に含まれる水平同期信号を分離して得ている。The sampling pulse for sampling by the sample hold 15 is obtained by demodulating a broadcast wave video signal with a video demodulator 17 and separating the horizontal synchronization signal contained in the video signal with a horizontal synchronization pulse separator 16.
第２局部発振器１４の出力は変調器４と変調器９０両方
に入力して周波数変換のための搬送波として使用されて
いる。The output of the second local oscillator 14 is input to both the modulator 4 and the modulator 90 and is used as a carrier wave for frequency conversion.
いま第１局部発振器１３の出力周波数をＦｌ、第２局部
発振器１４の出力周ｅ数をＦＺｅ装匝出力端子６での映
像搬送波の周波数をＦ３．放送波の映像搬送波周波数を
Ｆｏとすると、位相比較器１１の２つの位相が同期、す
なわち周波数が一致した伏線ではＰ、−Ｆ、 −Ｆｌ、
Ｆｌ−Ｆ、 −Ｆｏ、の式が成立する。Now, the output frequency of the first local oscillator 13 is Fl, the output frequency e of the second local oscillator 14 is F3, and the frequency of the video carrier wave at the FZe-equipped output terminal 6 is F3. When the video carrier frequency of the broadcast wave is Fo, the two phases of the phase comparator 11 are synchronized, that is, when the frequencies match, P, -F, -Fl,
The formula Fl-F, -Fo holds true.
これを整理するとＦ、−Ｆ・となυ、装置出力端子６で
の映像搬送波周波数Ｆｓが放送波の搬送波周波数Ｆｏに
一致する。Rearranging this, F, -F. and υ, the video carrier frequency Fs at the device output terminal 6 matches the carrier frequency Fo of the broadcast wave.
以上のように、本発明では、下位局で受信し／こ放送波
から抽出した基準信号に、上位局からのベースバンド信
号の搬送波周波数を一致させることより、ビートのない
吠＊僅号が得られる。As described above, in the present invention, by matching the carrier frequency of the baseband signal from the upper station to the reference signal received by the lower station and extracted from the broadcast wave, a beat-free signal can be obtained. It will be done.
第１図は本発明の一実施例の搬送波同期回路のプロ、り
図である。FIG. 1 is a schematic diagram of a carrier synchronization circuit according to an embodiment of the present invention.
Claims (1)
発振器および第２局部発振器と、放送波を前記第２局部
発振器で周波数変換して中間周波数の映像搬送波を得る
周波数変換手段と、この中間周波数の映像搬送波と前記
第１局部発振器の周波数を比較するための位相比較器と
、前記中間周波数の映像信号を復調して得られる水平同
期パルスにより前記位相比較器の出力をサンプリングし
て制御信号を得るサンプリング手段と、前記制御信号に
より前記第１局部発振器を制御してテレビ変調装置と放
送波の映像搬送波の周波数を一致させることを特徴とす
る搬送波同期回路。a voltage-controlled first local oscillator and a second local oscillator for converting the frequency of the video signal; a frequency conversion means for converting the frequency of the broadcast wave by the second local oscillator to obtain a video carrier wave of an intermediate frequency; a phase comparator for comparing the frequency of the video carrier wave and the frequency of the first local oscillator; and a control signal obtained by sampling the output of the phase comparator using a horizontal synchronization pulse obtained by demodulating the intermediate frequency video signal. 1. A carrier synchronization circuit comprising: sampling means for obtaining a signal; and controlling the first local oscillator using the control signal to match the frequency of a television modulation device and a video carrier wave of a broadcast wave.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29417185A JPS62154882A (en) | 1985-12-26 | 1985-12-26 | Carrier synchronizing circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29417185A JPS62154882A (en) | 1985-12-26 | 1985-12-26 | Carrier synchronizing circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS62154882A true JPS62154882A (en) | 1987-07-09 |
Family
ID=17804230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29417185A Pending JPS62154882A (en) | 1985-12-26 | 1985-12-26 | Carrier synchronizing circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62154882A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63292889A (en) * | 1987-05-26 | 1988-11-30 | Miharu Tsushin Kk | Removing method for same channel beat |
-
1985
- 1985-12-26 JP JP29417185A patent/JPS62154882A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63292889A (en) * | 1987-05-26 | 1988-11-30 | Miharu Tsushin Kk | Removing method for same channel beat |
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