JPH024542Y2 - - Google Patents
Info
- Publication number
- JPH024542Y2 JPH024542Y2 JP1984093625U JP9362584U JPH024542Y2 JP H024542 Y2 JPH024542 Y2 JP H024542Y2 JP 1984093625 U JP1984093625 U JP 1984093625U JP 9362584 U JP9362584 U JP 9362584U JP H024542 Y2 JPH024542 Y2 JP H024542Y2
- Authority
- JP
- Japan
- Prior art keywords
- signal
- circuit
- level
- vits
- output
- 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.)
- Expired
Links
- 238000000926 separation method Methods 0.000 claims description 8
- 238000001514 detection method Methods 0.000 claims description 7
- 239000000284 extract Substances 0.000 claims description 4
- 238000010586 diagram Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
Landscapes
- Television Receiver Circuits (AREA)
- Details Of Television Systems (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Description
【考案の詳細な説明】
〔産業上の利用分野〕
本考案はテレビジヨン受像機やVTR（Video
Tape Recorder）のAGC（Automatic Gain
Control）回路に関するもので、特に近い将来実
用化が予想されるデイジタルテレビジヨンやフア
クシミリ放送等に好適なAGC回路に関するもの
である。[Detailed explanation of the invention] [Field of industrial application] This invention is applicable to television receivers and VTRs (Video receivers).
Tape Recorder)'s AGC (Automatic Gain)
This invention relates to AGC circuits suitable for digital television and facsimile broadcasting, which are expected to be put into practical use in the near future.
ビデオ信号のAGC回路には従来から、映像信
号全体を検波してその平均値で制御する方法（平
均値型AGC）や、同期信号レベルを検出して制
御する方法（尖頭値型AGC）や、水平同期信号
の入る期間中だけ選択動作するAGC方式（キー
ドAGC）等があり、VTRでは水平同期信号のバ
ツクポーチに疑似パルスを挿入させ、同期信号と
疑似パルスのピーク検波を行つてAGC回路を制
御する方法等がとられている。
Traditionally, AGC circuits for video signals have a method of detecting the entire video signal and controlling it using its average value (average value type AGC), a method of detecting and controlling the synchronization signal level (peak value type AGC), There is an AGC method (keyed AGC) that selectively operates only during the period when the horizontal synchronizing signal is input.In VTRs, a pseudo pulse is inserted into the back porch of the horizontal synchronizing signal, and the peak detection of the synchronizing signal and pseudo pulse is performed to activate the AGC circuit. Control methods are being taken.
上記従来からとられている方法にはいずれも若
干問題点がある。すなわち、平均値型AGCでは
映像信号の影響でAGCのレベルが上・下するし、
同期信号レベルを検出するものでは同期信号を取
り出す回路（同期分離回路）が必要でしかも選局
した局によつてレベル変動を起すことがある。
All of the conventional methods described above have some problems. In other words, in average value type AGC, the AGC level increases or decreases due to the influence of the video signal,
A device that detects the synchronization signal level requires a circuit for extracting the synchronization signal (synchronization separation circuit), and the level may vary depending on the selected station.
本考案はこれらの問題点を解消し、受信チヤン
ネルの切換を行つてもほぼ一定のコントラストの
受像ができ、また入力信号の強弱によつてコント
ラストがつぶれたり同期が乱れたりすることのな
い、安定したAGC電圧が得られるAGC回路を提
供することを目的とするものである。 The present invention solves these problems, and enables image reception with almost constant contrast even when switching reception channels, and stable image reception that does not collapse the contrast or disrupt synchronization due to the strength or weakness of the input signal. The purpose of this invention is to provide an AGC circuit that can obtain a high AGC voltage.
上記の目的を達成するために、本考案のAGC
回路はテレビジヨン信号〔第２図ａ参照〕に重畳
されているVITS信号（VITS：Vertical nterval
Test Signal）の白信号（100％）のレベル（第
３図参照）と外部（受像機）に設定した基準信号
（基準レベル）とのレベルの比較を行い、増幅器
の増幅度を制御する構成にした。
In order to achieve the above objectives, the AGC of the present invention
The circuit converts the VITS signal (VITS: Vertical Interval) superimposed on the television signal (see Figure 2a).
The level of the white signal (100%) of the test signal (see Figure 3) is compared with the reference signal (reference level) set externally (receiver), and the amplification degree of the amplifier is controlled. did.
テレビジヨン信号は第２図ａに示すように、垂
直帰線期間（Field Blanking Period）の一部に
各種テスト用の信号としてVITS信号が挿入され
ている。上記VITS信号は例えば第３図Ａ，Ｂの
様な波形で構成されており、このような信号が１
フイードに２〜３ライン重畳されている（重畳の
仕方は放送局によつて異なる）。そして１フイー
ドに１回以上は必ず白100％の信号が普通重畳さ
れている。
As shown in FIG. 2a, in the television signal, a VITS signal is inserted as a signal for various tests into a part of the vertical blanking period (Field Blanking Period). The above VITS signal is composed of waveforms as shown in Figure 3 A and B, for example, and when such a signal is
Two to three lines are superimposed on the feed (the method of superimposition differs depending on the broadcasting station). And a 100% white signal is usually superimposed at least once in one feed.
本考案は、フイールド毎に重畳されている上記
白信号に着目し、基準信号とのレベル比較により
AGC動作をさせるものであり、映像信号の影響
を受けることがなく、検出感度も良くなる。 This invention focuses on the above-mentioned white signal that is superimposed on each field, and compares the level with the reference signal.
It performs AGC operation, is not affected by video signals, and has improved detection sensitivity.
次に本考案の実施例を図面を参照して説明す
る。
Next, embodiments of the present invention will be described with reference to the drawings.
第１図は本考案のAGC回路の一実施例を示す
ブロツク図である。 FIG. 1 is a block diagram showing an embodiment of the AGC circuit of the present invention.
ビデオ信号（テレビジヨン信号）入力端子１に
は第２図ｄの様な波形の信号が入力される。この
信号はローパスフイルタ（LPF）２と可変減衰
器１０に入力される。ローパスフイルタ２は
VITS信号の高域成分を除去するとともに雑音を
除去し、低域成分（白レベル信号）を安定にとり
だす。例えば第３図Ｂに示すVITS信号がローパ
スフイルタ２を通つた後の信号波形は同図B′の
ようになる。この信号を垂直同期分離回路３に入
力し、垂直同期パルス列を検出し、第２図ｂに示
す垂直同期分離信号を得る。この信号をゲートパ
ルス発生回路４に入力し、垂直同期分離信号の立
下りを用いて第２図ｃに示すVITS信号抜きとり
用のゲートパルスを発生させる。VITS信号は通
常数ラインにわたつて挿入されており、抜きとり
用のゲートパルス幅はこれを考慮して決める。ゲ
ートパルスはゲート回路５に入力される。ゲート
回路５はローパスフイルタ２を通つた後の信号か
らVITS信号を抜きとる。次段のピーク検波回路
６はVITS信号の白レベル（白ピーク）を検出
し、これを１フイード間ホールドする。この検出
された白レベルは、次段のレベル比較器７で基準
レベル設定回路８からの基準レベルと振幅比較が
行われる。比較出力はデコーダ９でデコードさ
れ、信号ラインに挿入されている可変減衰器１０
の抵抗値を制御してビデオ信号の出力信号レベル
を一定にする。 A video signal (television signal) input terminal 1 receives a signal having a waveform as shown in FIG. 2d. This signal is input to a low pass filter (LPF) 2 and a variable attenuator 10. Low pass filter 2
It removes the high-frequency components of the VITS signal, removes noise, and stably extracts the low-frequency components (white level signal). For example, after the VITS signal shown in FIG. 3B passes through the low-pass filter 2, the signal waveform becomes as shown in FIG. 3B'. This signal is input to the vertical synchronization separation circuit 3, a vertical synchronization pulse train is detected, and a vertical synchronization separation signal shown in FIG. 2b is obtained. This signal is input to the gate pulse generation circuit 4, and the falling edge of the vertical synchronization separation signal is used to generate the gate pulse for extracting the VITS signal shown in FIG. 2c. The VITS signal is usually inserted over several lines, and the gate pulse width for extraction is determined with this in mind. The gate pulse is input to the gate circuit 5. The gate circuit 5 extracts the VITS signal from the signal passed through the low-pass filter 2. The next stage peak detection circuit 6 detects the white level (white peak) of the VITS signal and holds it for one feed. The detected white level is compared in amplitude with the reference level from the reference level setting circuit 8 in the level comparator 7 at the next stage. The comparison output is decoded by a decoder 9 and a variable attenuator 10 inserted into the signal line.
The output signal level of the video signal is kept constant by controlling the resistance value of the video signal.
第４図及び第５図は、上記実施例（第１図）の
レベル比較器より後段の部分を詳細に示した回路
図で、第４図はオープンループのAGC回路の場
合の一例であり、第５図は閉回路のAGC回路の
場合の一例である。いずれの場合にも、レベル比
較器７には適宜ビツト数のＡ／Ｄコンバータを用
いている。 FIGS. 4 and 5 are circuit diagrams showing in detail the stage after the level comparator of the above embodiment (FIG. 1), and FIG. 4 is an example of an open-loop AGC circuit. FIG. 5 is an example of a closed AGC circuit. In either case, the level comparator 7 uses an A/D converter with an appropriate number of bits.
オープンループのAGC回路（第４図）では、
上記レベル比較器７で基準レベル設定回路８が設
定した基準レベルE0とレベル比較を行い、この
出力をデコーダ９でデコードして、可変減衰器１
０の抵抗R1〜Rnをオン・オフすることにより出
力信号レベルを調整している。 In the open-loop AGC circuit (Figure 4),
The level comparator 7 compares the level with the reference level E 0 set by the reference level setting circuit 8, and this output is decoded by the decoder 9, and the variable attenuator 1
The output signal level is adjusted by turning on and off the zero resistances R 1 to Rn.
閉回路（第５図）の場合には、可変減衰器１０
の出力側レベル検出器１２に入力し、ここで基準
レベル設定回路８からの基準レベルE0とレベル
比較してレベル比較器７の基準入力直流電圧を発
生させている。 In the case of a closed circuit (Fig. 5), a variable attenuator 10
The voltage is input to the output side level detector 12, where the level is compared with the reference level E0 from the reference level setting circuit 8 to generate a reference input DC voltage for the level comparator 7.
以上説明したように、本考案のAGC回路は
VITS信号の白信号レベルを検出してAGC電圧を
作つているので、映像信号の影響を受けないし、
検出感度も上げられる。また、可変減衰器の抵抗
の数を多くして、減衰比を種々変えられるように
すれば、きめの細かい自動利得制御を行うことが
できる。
As explained above, the AGC circuit of the present invention
Since the AGC voltage is created by detecting the white signal level of the VITS signal, it is not affected by the video signal.
Detection sensitivity can also be increased. Further, by increasing the number of resistors in the variable attenuator so that the attenuation ratio can be varied, fine-grained automatic gain control can be performed.
第１図は本考案のAGC回路のブロツク図。第
２図は各部の信号の波形図で、同図ａはテレビジ
ヨン信号、ｂは垂直同期分離信号、ｃはゲートパ
ルスである。第３図はVITS信号の波形図で、同
図Ａ，Ｂはテレビジヨン信号に含まれいる波形の
例、B′はＢに示した波形の信号をローパスフイ
ルタに通した後の波形である。第４図及び第５図
は本考案のAGC回路の一部分を詳細に示した回
路図である。
１……ビデオ信号入力端子、２……ローパスフ
イルタ（LPF）、３……垂直同期分離回路、４…
…ゲートパルス発生回路、５……ゲート回路、６
……ピーク検波回路、７……レベル比較器、８…
…基準レベル設定回路、９……デコーダ、１０…
…可変減衰器、１１……ビデオ信号出力端子、１
２……レベル検出器。
Figure 1 is a block diagram of the AGC circuit of the present invention. FIG. 2 is a waveform diagram of signals at various parts, in which a is a television signal, b is a vertical synchronization separation signal, and c is a gate pulse. FIG. 3 is a waveform diagram of the VITS signal, in which A and B are examples of waveforms included in the television signal, and B' is the waveform after the waveform signal shown in B is passed through a low-pass filter. 4 and 5 are circuit diagrams showing in detail a portion of the AGC circuit of the present invention. 1...Video signal input terminal, 2...Low pass filter (LPF), 3...Vertical synchronization separation circuit, 4...
...Gate pulse generation circuit, 5...Gate circuit, 6
...Peak detection circuit, 7...Level comparator, 8...
...Reference level setting circuit, 9...Decoder, 10...
...Variable attenuator, 11...Video signal output terminal, 1
2...Level detector.
Claims (1)
VITS信号（VITS：Vertical Internal Test
Signal）を用いるAGC回路であつて、 前記テレビジヨン信号の低周波成分を通過する
ローパスフイルタと、垂直同期分離信号を得る垂
直同期分離回路と、VITS信号を抜きとるゲート
パルスを得るゲートパルス発生回路と、 前記ローパスフイルタの出力と前記ゲートパル
ス回路の出力とによりVITS信号を抜きとるゲー
ト回路と、VITS信号の白レベルを検出するピー
ク検波回路と、基準レベル設定回路と、 前記ピーク検波回路の出力と前記基準レベル設
定回路の出力との白レベルと基準レベルの振幅比
較を行うレベル比較器と、比較出力信号をデコー
ドするデコーダと、前記デコーダの出力により前
記テレビジヨン信号を一定レベルに調整する可変
減衰器とを具備した ことを特徴とするAGC回路。[Scope of claim for utility model registration]
VITS signal (VITS: Vertical Internal Test
The AGC circuit uses a low-frequency component of the television signal, a vertical sync separation circuit that obtains a vertical sync separation signal, and a gate pulse generation circuit that obtains a gate pulse that extracts the VITS signal. a gate circuit that extracts the VITS signal based on the output of the low-pass filter and the output of the gate pulse circuit; a peak detection circuit that detects the white level of the VITS signal; a reference level setting circuit; and an output of the peak detection circuit. and a level comparator that compares the amplitude of the white level and the reference level with the output of the reference level setting circuit, a decoder that decodes the comparison output signal, and a variable that adjusts the television signal to a constant level using the output of the decoder. An AGC circuit characterized by comprising an attenuator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984093625U JPS619962U (en) | 1984-06-22 | 1984-06-22 | AGC circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984093625U JPS619962U (en) | 1984-06-22 | 1984-06-22 | AGC circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS619962U JPS619962U (en) | 1986-01-21 |
| JPH024542Y2 true JPH024542Y2 (en) | 1990-02-02 |
Family
ID=30651471
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1984093625U Granted JPS619962U (en) | 1984-06-22 | 1984-06-22 | AGC circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS619962U (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07101932B2 (en) * | 1987-09-04 | 1995-11-01 | シャープ株式会社 | AGC circuit for high definition television signals |
| US8330550B2 (en) * | 2006-06-23 | 2012-12-11 | Rgb Systems, Inc. | Method and apparatus for automatic compensation of video signal losses from transmission over conductors |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5416919A (en) * | 1977-07-08 | 1979-02-07 | Hitachi Ltd | Automaic gain control circuit |
-
1984
- 1984-06-22 JP JP1984093625U patent/JPS619962U/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5416919A (en) * | 1977-07-08 | 1979-02-07 | Hitachi Ltd | Automaic gain control circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS619962U (en) | 1986-01-21 |
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