JPH0865651A - Catv head-end device - Google Patents
Catv head-end deviceInfo
- Publication number
- JPH0865651A JPH0865651A JP6201865A JP20186594A JPH0865651A JP H0865651 A JPH0865651 A JP H0865651A JP 6201865 A JP6201865 A JP 6201865A JP 20186594 A JP20186594 A JP 20186594A JP H0865651 A JPH0865651 A JP H0865651A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- frequency
- station
- local
- mixer
- 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.)
- Granted
Links
Landscapes
- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明はCATVヘッドエンド装
置に関し、特に地域外からのTV信号を受信しチャンネ
ル変換して再送信するCATVヘッドエンド装置に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV head-end device, and more particularly to a CATV head-end device which receives a TV signal from outside the area, converts the channel, and retransmits it.
【0002】[0002]
【従来の技術】地方のCATV局では、例えば、東京民
放局の微弱なTV電波を受信しチャンネル変換した後、
同軸ケーブルを介して加入者へ再送信している。ところ
で、CATV加入者の居住する地域の地元TV局が、再
送信するTV信号の送信チャンネルと同じチャンネルに
よりTV電波を送信している場合には、加入者のテレビ
画面上に視覚的な妨害が生じることになる。この場合、
両TV信号の搬送波周波数のずれに応じて、妨害画像が
上下左右に移動するので非常に見苦しい。このような視
覚的な妨害を軽減するために、CATV局側では、再送
信TV信号の搬送波周波数が地元TV局の送信搬送波周
波数と一致するように、公知のPLLを設けて位相同期
させて妨害画像が上下左右に移動するのを抑えている。2. Description of the Related Art A local CATV station, for example, receives a weak TV radio wave from a Tokyo commercial broadcasting station, converts the channel, and then converts the channel.
Retransmitting to the subscriber via coaxial cable. By the way, if a local TV station in the area where the CATV subscriber resides transmits TV radio waves on the same channel as the transmission channel of the TV signal to be retransmitted, visual interference is displayed on the television screen of the subscriber. Will happen. in this case,
The disturbing image moves up, down, left, and right in accordance with the difference between the carrier frequencies of both TV signals, so that it is very unsightly. In order to reduce such visual interference, the CATV station side installs a well-known PLL so that the carrier frequency of the retransmitted TV signal coincides with the transmission carrier frequency of the local TV station, and performs phase synchronization to prevent the interference. This suppresses the image from moving up, down, left, and right.
【0003】[0003]
【発明が解決しようとする課題】上述したように従来
は、CATV局が再送信するTVチャンネルと地元TV
局の送信チャンネルとが同じチャンネルである場合の視
覚的妨害を軽減するために、再送信するTV信号の送信
搬送波周波数を地元TV局の送信搬送波周波数に一致さ
せ、妨害画像が上下左右に移動するのを抑えているい
る。しかし、同じチャンネルの2つのTV信号の画像が
同一であるならば視覚的妨害は軽減できるが、異なる画
像のときには画像が互いに重なった状態となり、視覚的
妨害を十分に軽減できないという問題点を有している。As described above, conventionally, the CATV station retransmits the TV channel and the local TV.
In order to reduce visual interference when the transmission channel of the station is the same channel, the transmission carrier frequency of the TV signal to be retransmitted is matched with the transmission carrier frequency of the local TV station, and the interference image moves up, down, left and right. Have been suppressed. However, if two TV signals of the same channel have the same image, the visual interference can be reduced, but when the images are different, the images overlap with each other, and the visual interference cannot be sufficiently reduced. are doing.
【0004】本発明の目的は、CATV局が再送信する
TV信号の送信チャンネルと地元TV局の送信チャンネ
ルとが同じ場合でも、視覚的妨害を軽減できるCATV
ヘッドエンド装置を提供することにある。An object of the present invention is to provide a CATV system capable of reducing visual interference even when the transmission channel of a TV signal retransmitted by a CATV station is the same as that of a local TV station.
To provide a headend device.
【0005】[0005]
【課題を解決するための手段】本発明のCATVヘッド
エンド装置は、制御信号に応じて発振周波数を変化させ
る電圧制御発振器と、再送信のために受信するTV信号
を周波数変換して搬送波周波数fiの第1の中間周波信
号として出力する第1の混合器と、再送信するTV信号
の送信チャンネルと同じチャンネルの地元TV局のTV
信号を前記電圧制御発振器の発振出力信号により周波数
変換して第2の中間周波信号として出力する第2の混合
器と、前記第1の中間周波信号を分周比1/M(Mは2
以上の整数)で分周する第1の分周器と、前記第2の中
間周波信号を分周比1/N(Nは2以上の整数かつN≠
M)で分周する第2の分周器と、前記第1および第2の
分周器の出力信号をそれぞれ受けて位相比較し前記制御
信号を出力する位相比較器と、前記第1の中間周波信号
を前記電圧制御発振器の発振出力信号により周波数変換
して前記地元TV局のTV信号に対してオフセット周波
数Δf=fi(1−M/N)だけオフセットされた再送
信TV信号を出力する第3の混合器とを備える。また、
前記第1の分周器は、外部から供給される信号により分
周比を可変できるように構成してもよい。A CATV head-end device according to the present invention comprises a voltage-controlled oscillator for changing an oscillation frequency in accordance with a control signal, and a carrier frequency fi by converting a TV signal received for retransmission. A first mixer for outputting the first intermediate frequency signal of the first TV and a TV of a local TV station on the same channel as the transmission channel of the TV signal to be retransmitted
A second mixer that frequency-converts the signal by the oscillation output signal of the voltage-controlled oscillator and outputs it as a second intermediate frequency signal, and the first intermediate frequency signal with a frequency division ratio 1 / M (M is 2).
A first frequency divider that divides the frequency of the second intermediate frequency signal by a frequency division ratio of 1 / N (N is an integer of 2 or more and N ≠).
M), a phase comparator that receives the output signals of the first and second frequency dividers, compares the phases, and outputs the control signal, and the first intermediate divider. A frequency signal is converted into a frequency by the oscillation output signal of the voltage controlled oscillator, and a retransmission TV signal is output which is offset by an offset frequency Δf = fi (1-M / N) with respect to the TV signal of the local TV station. 3 mixers. Also,
The first frequency divider may be configured so that the frequency division ratio can be changed by a signal supplied from the outside.
【0006】[0006]
【実施例】次に本発明について図面を参照して説明す
る。The present invention will be described below with reference to the drawings.
【0007】図1は本発明の一実施例を示すブロック図
である。ここで、混合器1は、CATV局が再送信のた
めに受信するTV信号S1を受け、局部発振器2からの
局発信号S2と混合して中間周波信号S3に変換する。
一方、混合器4は、CATV局が再送信するTV信号の
送信チャンネルと同じチャンネルの地元TV局のTV信
号S4を受け、VCO(電圧制御発振器)8の発振出力
信号S8と混合して中間周波信号S5に変換する。FIG. 1 is a block diagram showing an embodiment of the present invention. Here, the mixer 1 receives the TV signal S1 received by the CATV station for retransmission, mixes it with the local signal S2 from the local oscillator 2, and converts it into an intermediate frequency signal S3.
On the other hand, the mixer 4 receives the TV signal S4 of the local TV station on the same channel as the transmission channel of the TV signal to be retransmitted by the CATV station, mixes it with the oscillation output signal S8 of the VCO (voltage controlled oscillator) 8, and The signal is converted to a signal S5.
【0008】可変分周器5は、外部から供給される分周
比制御信号Sdの指定により分周比を変化させて、中間
周波信号S3を分周する。同様に分周器6は、中間周波
信号S5を所定の分周比で分周する。位相比較器7は、
可変分周器5および分周器6の出力信号S6,S7の位
相を比較し、制御信号ScをVCO8へ出力して位相同
期するように発振出力信号S8の周波数f8を制御す
る。混合器3は、VCO8の発振出力信号S8と中間周
波信号S3とを混合して再送信TV信号S9として出力
する。The variable frequency divider 5 divides the intermediate frequency signal S3 by changing the frequency division ratio according to a frequency division ratio control signal Sd supplied from the outside. Similarly, the frequency divider 6 frequency-divides the intermediate frequency signal S5 at a predetermined frequency division ratio. The phase comparator 7
The phases of the output signals S6 and S7 of the variable frequency divider 5 and the frequency divider 6 are compared, and the control signal Sc is output to the VCO 8 to control the frequency f8 of the oscillation output signal S8 so that the phases are synchronized. The mixer 3 mixes the oscillation output signal S8 of the VCO 8 and the intermediate frequency signal S3 and outputs it as the retransmitted TV signal S9.
【0009】次に動作を説明する。Next, the operation will be described.
【0010】いま、例えば、TV信号S1の搬送波周波
数f1を489.25MHzとし、,TV信号S4の搬
送波周波数f4を171.25MHzとし、中間周波信
号S3,S5の搬送波周波数f3,f5を58.75M
Hzとする。また、VCO8の発振出力信号S8の周波
数f8は、f8=f4+f5=171.25+58.7
5=230.00MHzとする。Now, for example, the carrier frequency f1 of the TV signal S1 is 489.25 MHz, the carrier frequency f4 of the TV signal S4 is 171.25 MHz, and the carrier frequencies f3 and f5 of the intermediate frequency signals S3 and S5 are 58.75M.
Hz. The frequency f8 of the oscillation output signal S8 of the VCO 8 is f8 = f4 + f5 = 171.25 + 58.7.
5 = 230.00 MHz.
【0011】まず、可変分周器5および分周器6の分周
比を同じにして1/5875とすれば、分周後の信号S
6,S7の周波数は共に10kHzとなる。位相比較器
7は、信号S6と信号S7とが位相同期するようにVC
O8の発振周波数f8を制御する。従って、混合器3が
出力する再送信TV信号S9の搬送波周波数f9は、f
9=f8−f3=230.00−58.75=171.
25MHz となり、地元TV局の送信信号S2の搬送
波周波数と一致する。First, if the frequency division ratios of the variable frequency divider 5 and the frequency divider 6 are set to 1/5875, the signal S after the frequency division is obtained.
The frequencies of 6 and S7 are both 10 kHz. The phase comparator 7 controls the VC so that the signal S6 and the signal S7 are phase-synchronized.
The oscillation frequency f8 of O8 is controlled. Therefore, the carrier frequency f9 of the retransmitted TV signal S9 output from the mixer 3 is f
9 = f8-f3 = 230.00-58.75 = 171.
25 MHz, which matches the carrier frequency of the transmission signal S2 of the local TV station.
【0012】ここで、可変分周器5の分周比のみを変更
して1/5876とすれば、分周後の信号S6の周波数
f6は、f6=58750/5876=9.998kH
zとなる。Here, if only the frequency division ratio of the variable frequency divider 5 is changed to 1/5876, the frequency f6 of the frequency-divided signal S6 is f6 = 58750/5876 = 9.998 kHz.
z.
【0013】位相比較器7は、信号S6と信号S7とが
位相同期するようにVCO8の発振周波数f8を制御す
るので、信号S7の周波数f7は信号S6と一致し、f
7=9.998kHzとなる。ところで、分周器6の分
周比は1/5875であるから、分周器6の入力信号S
5の搬送波周波数f5は、f5=5875×9.998
≒58.74MHzとなっている。すなわち、VCO8
の発振周波数f8は、f8=f4+f5=171.25
+58.74=229.99MHzとなっている。従っ
て、混合器3が出力する再送信TV信号S9の搬送波周
波数f9は、f9=f8−f3=229.99−58.
75=171.24MHzとなり、地元TV局のTV信
号S4の搬送波周波数f4=171.25MHzに対し
て、−10kHzだけオフセットされる。Since the phase comparator 7 controls the oscillation frequency f8 of the VCO 8 so that the signal S6 and the signal S7 are phase-synchronized, the frequency f7 of the signal S7 matches the signal S6, and f
7 = 9.998 kHz. By the way, since the frequency division ratio of the frequency divider 6 is 1/5875, the input signal S
The carrier frequency f5 of 5 is f5 = 5875 × 9.998
≒ 58.74 MHz. That is, VCO8
Oscillation frequency f8 is f8 = f4 + f5 = 171.25
+ 58.74 = 229.99 MHz. Therefore, the carrier frequency f9 of the retransmitted TV signal S9 output from the mixer 3 is f9 = f8−f3 = 229.99−58.
75 = 171.24 MHz, which is offset by -10 kHz with respect to the carrier frequency f4 = 171.25 MHz of the TV signal S4 of the local TV station.
【0014】なお、一般的に、中間周波信号の搬送波周
波数をfiとし、可変分周器5の分周比を1/M(Mは
2以上の整数)とし、分周器6の分周比を1/N(Nは
2以上の整数かつN≠M)とし、オフセット周波数をΔ
fとすれば、Δf=fi(1−M/N)を満足するよう
に分周比を設定すればよい。また、Mを変化させること
により、オフセット周波数Δfを調整することができ
る。Generally, the carrier frequency of the intermediate frequency signal is fi, the frequency division ratio of the variable frequency divider 5 is 1 / M (M is an integer of 2 or more), and the frequency division ratio of the frequency divider 6 is (N is an integer of 2 or more and N ≠ M), and the offset frequency is Δ
Assuming that f, the frequency division ratio may be set so as to satisfy Δf = fi (1−M / N). Further, the offset frequency Δf can be adjusted by changing M.
【0015】[0015]
【発明の効果】以上説明したように本発明によれば、C
ATV局の再送信TV信号の送信チャンネルと地元TV
局の送信チャンネルとが同じTVチャンネルになる場
合、再送信するために受信したTV信号および地元TV
局の送信信号をそれぞれ中間周波信号に変換した後、異
なる分周比でそれぞれ分周して位相比較してVCOを制
御し、地元TV局の送信信号に対して所定のオフセット
周波数だけオフセットされた局部発振信号をVCOによ
り生成し、再送信するために受信した中間周波数のTV
信号を再び周波数変換して再送信TV信号とすることに
より、再送信TV信号の送信搬送波周波数を地元TV局
の搬送波周波数に対してオフセット周波数だけオフセッ
トできるので、TV信号の画像が異なっている場合で
も、画面上では各ライン間にオフセットビートとして現
われるため、同じチャンネルであるために生じる視覚的
妨害を更に軽減できるという効果を有している。また、
分周比を変化させることにより、所定のオフセット周波
数にすることができる。As described above, according to the present invention, C
ATV station retransmission TV signal transmission channel and local TV
If the station's transmission channel is the same TV channel, the received TV signal and the local TV for retransmission
After converting the transmission signal of each station into an intermediate frequency signal, the frequency is divided at different division ratios and the phases are compared to control the VCO, and the transmission signal of the local TV station is offset by a predetermined offset frequency. A local oscillation signal generated by a VCO and received at an intermediate frequency TV for retransmission.
When the frequency of the signal is converted again into the retransmitted TV signal, the transmission carrier frequency of the retransmitted TV signal can be offset by the offset frequency with respect to the carrier frequency of the local TV station. However, since it appears as an offset beat between each line on the screen, it has the effect of further reducing the visual interference caused by the same channel. Also,
By changing the frequency division ratio, a predetermined offset frequency can be obtained.
【図1】本発明の一実施例を示すブロック図である。FIG. 1 is a block diagram showing an embodiment of the present invention.
1,3,4 混合器 5 可変分周器 6 分周器 7 位相比較器 8 VCO(電圧制御発振器) S1 CATV局が再送信のために受信するTV信号 S4 地元TV局が送信するTV信号(S9と同じチ
ャンネル) S3,S5 中間周波信号 S8 VCO出力信号 S9 CATV局が再送信するTV信号(S4と同じ
チャンネル) Sd 分周比制御信号1, 3, 4 mixer 5 variable frequency divider 6 frequency divider 7 phase comparator 8 VCO (voltage controlled oscillator) S1 TV signal received by CATV station for retransmission S4 TV signal transmitted by local TV station ( S3, S5 Intermediate frequency signal S8 VCO output signal S9 TV signal retransmitted by CATV station (same channel as S4) Sd Division ratio control signal
Claims (2)
る電圧制御発振器と、再送信のために受信するTV信号
を周波数変換して搬送波周波数fiの第1の中間周波信
号として出力する第1の混合器と、再送信するTV信号
の送信チャンネルと同じチャンネルの地元TV局のTV
信号を前記電圧制御発振器の発振出力信号により周波数
変換して第2の中間周波信号として出力する第2の混合
器と、前記第1の中間周波信号を分周比1/M(Mは2
以上の整数)で分周する第1の分周器と、前記第2の中
間周波信号を分周比1/N(Nは2以上の整数かつN≠
M)で分周する第2の分周器と、前記第1および第2の
分周器の出力信号をそれぞれ受けて位相比較し前記制御
信号を出力する位相比較器と、前記第1の中間周波信号
を前記電圧制御発振器の発振出力信号により周波数変換
して前記地元TV局のTV信号に対してオフセット周波
数Δf=fi(1−M/N)だけオフセットされた再送
信TV信号を出力する第3の混合器とを備えることを特
徴とするCATVヘッドエンド装置。1. A voltage-controlled oscillator for changing an oscillation frequency in accordance with a control signal, and a first for converting a frequency of a TV signal received for retransmission and outputting the converted signal as a first intermediate frequency signal of a carrier frequency fi. A mixer and a TV of a local TV station on the same channel as the transmission channel of the retransmitted TV signal
A second mixer that frequency-converts the signal by the oscillation output signal of the voltage-controlled oscillator and outputs it as a second intermediate frequency signal, and the first intermediate frequency signal with a frequency division ratio 1 / M (M is 2).
A first frequency divider that divides the frequency of the second intermediate frequency signal by a frequency division ratio of 1 / N (N is an integer of 2 or more and N ≠).
M), a phase comparator that receives the output signals of the first and second frequency dividers, compares the phases, and outputs the control signal, and the first intermediate divider. A frequency signal is converted into a frequency by the oscillation output signal of the voltage controlled oscillator, and a retransmission TV signal is output which is offset by an offset frequency Δf = fi (1-M / N) with respect to the TV signal of the local TV station. 3. A CATV head-end device comprising:
る信号により分周比を可変できることを特徴とする請求
項1記載のCATVヘッドエンド装置。2. The CATV headend device according to claim 1, wherein the first frequency divider can change a frequency division ratio by a signal supplied from the outside.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP6201865A JP2609819B2 (en) | 1994-08-26 | 1994-08-26 | CATV headend device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP6201865A JP2609819B2 (en) | 1994-08-26 | 1994-08-26 | CATV headend device |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH0865651A true JPH0865651A (en) | 1996-03-08 |
JP2609819B2 JP2609819B2 (en) | 1997-05-14 |
Family
ID=16448177
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP6201865A Expired - Lifetime JP2609819B2 (en) | 1994-08-26 | 1994-08-26 | CATV headend device |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2609819B2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010050945A (en) * | 2008-03-05 | 2010-03-04 | Yagi Antenna Co Ltd | Retransmission device |
-
1994
- 1994-08-26 JP JP6201865A patent/JP2609819B2/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010050945A (en) * | 2008-03-05 | 2010-03-04 | Yagi Antenna Co Ltd | Retransmission device |
JP2010158045A (en) * | 2008-03-05 | 2010-07-15 | Yagi Antenna Co Ltd | Retransmitting device |
Also Published As
Publication number | Publication date |
---|---|
JP2609819B2 (en) | 1997-05-14 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 19961217 |