JPH01254088A - Automatic gain controller - Google Patents
Automatic gain controllerInfo
- Publication number
- JPH01254088A JPH01254088A JP8156588A JP8156588A JPH01254088A JP H01254088 A JPH01254088 A JP H01254088A JP 8156588 A JP8156588 A JP 8156588A JP 8156588 A JP8156588 A JP 8156588A JP H01254088 A JPH01254088 A JP H01254088A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- converter
- output
- variable gain
- gain
- 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
- 239000002131 composite material Substances 0.000 claims abstract description 27
- 238000001514 detection method Methods 0.000 claims abstract description 15
- 238000006243 chemical reaction Methods 0.000 claims abstract description 9
- 239000000284 extract Substances 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 8
- 239000003990 capacitor Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000013139 quantization Methods 0.000 description 1
Landscapes
- Processing Of Color Television Signals (AREA)
Abstract
Description
【発明の詳細な説明】
産業上の利用分野
本発明は、ム／Ｄ変換器のダイナミックレンジを有効に
利用するためにム／Ｄ変換器に入力するアナログ映像信
号の振幅を一定の値に制御するための自動利得制御装置
に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to controlling the amplitude of an analog video signal input to a MU/D converter to a constant value in order to effectively utilize the dynamic range of the MU/D converter. The present invention relates to an automatic gain control device for controlling.
従来の技術
近年映像信号処理のディジタル化が盛んに行われ、ム／
Ｄ変換器のダイナミックレンジを有効に利用するために
ム／Ｄ変換器に入力するアナログ映像信号の振幅を一定
の値に制御するための自動利得制御装置に対する要望が
高まっている。Background of the Invention In recent years, video signal processing has been increasingly digitized.
There is an increasing demand for an automatic gain control device for controlling the amplitude of an analog video signal input to a MU/D converter to a constant value in order to effectively utilize the dynamic range of the D converter.
以下図面を参照しながら従来の自動利得制御装置につい
て説明する。第６図は従来の自動利得制御装置の構成を
示したブロック図である。第５図に於て入力端子３０か
ら入力された搬送色信号を含む複合映像信号（以下コン
ポジット信号と呼ぶ）は可変利得増幅器３１で増幅され
てム／Ｄ変換器３２でディジタル信号に変換される。こ
の信号は信号処理部に送られる一方、レベル検出器３５
にも送られて人／Ｄ変換され、コンポジット信号の振幅
が検出され、予め設定された基準値との差が算出される
。このとき従来の同期信号の振幅を検出する方法がよく
用いられている。この振幅値はＤ／Ａ変換器３４でアナ
ログ信号に変換されローパスフィルタ３３を通って可変
利得増幅器３１を制御し、ム／Ｄ変換器３２０入力は一
定の値に保たれる。この様な自動利得制御装置は、例え
ば、特開昭６０−２６１２８２号公報に示されている。A conventional automatic gain control device will be described below with reference to the drawings. FIG. 6 is a block diagram showing the configuration of a conventional automatic gain control device. In FIG. 5, a composite video signal (hereinafter referred to as a composite signal) including a carrier color signal inputted from an input terminal 30 is amplified by a variable gain amplifier 31 and converted into a digital signal by a MU/D converter 32. . This signal is sent to the signal processing section, while the level detector 35
The amplitude of the composite signal is detected, and the difference from a preset reference value is calculated. At this time, a conventional method of detecting the amplitude of the synchronization signal is often used. This amplitude value is converted into an analog signal by the D/A converter 34, passes through the low-pass filter 33, and controls the variable gain amplifier 31, and the input to the MU/D converter 320 is kept at a constant value. Such an automatic gain control device is disclosed in, for example, Japanese Patent Laid-Open No. 60-261282.
発明が解決しようとする課題
しかしながら上記のような構成の自動利得制御装置では
、コンポジット信号中の搬送色信号が輝度信号に対して
振幅の小さいときは、同期信号の振幅を一定になるよう
に制御しても搬送色信号の振幅は小さく、ム／Ｄ変換し
たとき搬送色信号の量子化ノイズが増え、信号処理する
と色信号のＳ／Ｎが劣化する欠点があった。また最近は
コンポジット信号の他に輝度信号と搬送色信号を別々に
伝送するコンポーネント信号がよく用いられるようにな
シ今述べた方法では対処できないという問題があった。Problems to be Solved by the Invention However, in the automatic gain control device configured as described above, when the carrier color signal in the composite signal has a smaller amplitude than the luminance signal, the amplitude of the synchronization signal is controlled to be constant. However, the amplitude of the carrier color signal is small, the quantization noise of the carrier color signal increases when subjected to Mu/D conversion, and the signal-to-noise ratio of the color signal deteriorates when signal processing is performed. Furthermore, recently, in addition to composite signals, component signals that separately transmit a luminance signal and a carrier color signal are often used, and there is a problem that cannot be solved by the method just described.
本発明は上記問題点に鑑み、コンポジット信号の輝度信
号と搬送色信号の振幅を別々に制御してム／Ｄ変換に於
けるダイナミックレンジを輝度信号に対しても搬送色信
号に対しても最適にでき、またコンポーネント信号に対
しても効果的に対応できる自動利得制御装置を提供する
ものである。In view of the above problems, the present invention separately controls the amplitude of the luminance signal and the carrier chrominance signal of a composite signal, thereby optimizing the dynamic range in the MU/D conversion for both the luminance signal and the carrier chrominance signal. The present invention provides an automatic gain control device that can effectively handle component signals.
課題を解決するだめの手段
上記問題点会解決するために本発明の自動利得制御装置
は、搬送色信号を含む複合映像信号の輝度信号帯域の利
得と搬送色信号帯域の利得を独立して制御できる第１の
可変利得増幅器と、第１の可変利得増幅器の出力をム／
Ｄ変換する第１のム／Ｄ変換器と、第１のム／Ｄ変換器
の出力信号から輝度信号の振幅を検出し設定された輝度
信号の基準値との差を算出する第１の振幅検出手段と、
搬送色信号の振幅を検出し設定された搬送色信号の基準
値との差を算出する第２の振幅検出手段と、第１の振幅
検出手段の出力をＤ／Ａ変換する第１のＤ／Ａ変換器と
、第２の振幅検出手段の出力をＤ／Ａ変換する第２のＤ
／Ａ変換器とを具備し、第１の可変利得増幅器の輝度信
号帯域の利得は第１のＤ／Ａ変換器の出力で制御し、搬
送色信号帯域の利得は第２のＤ／Ａ変換器の出力で制御
するように構成されるものである。Means for Solving the Problems In order to solve the above problems, the automatic gain control device of the present invention independently controls the gain of the luminance signal band and the gain of the carrier chrominance signal band of a composite video signal including a carrier chrominance signal. the output of the first variable gain amplifier and the output of the first variable gain amplifier.
A first Mu/D converter that performs D conversion, and a first amplitude that detects the amplitude of a luminance signal from the output signal of the first Mu/D converter and calculates a difference between a set reference value of the luminance signal. detection means;
a second amplitude detection means for detecting the amplitude of the carrier color signal and calculating a difference between the amplitude and a set reference value of the carrier color signal; and a first D/A converter for D/A converting the output of the first amplitude detection means. A converter and a second D that converts the output of the second amplitude detection means from D/A.
/A converter, the gain of the luminance signal band of the first variable gain amplifier is controlled by the output of the first D/A converter, and the gain of the carrier color signal band is controlled by the output of the second D/A converter. It is configured to be controlled by the output of the device.
作用
本発明は上記の構成により、コンポジット信号に対して
は搬送色信号と輝度信号の振幅を別々に検出し、その振
幅情報によって１つの可変利得増幅器を制御して搬送色
信号に対しても輝度信号に対してもム／Ｄ変換器のダイ
ナミックレンジを最適にすることができる。また本発明
はコンポーネント信号に対しては搬送色信号と輝度信号
それぞれを別々の可変利得増幅器で制御して両方の信号
に対してム／Ｄ変換器のダイナミックレンジを最適にす
る自動利得制御装置を実現できる。According to the above configuration, the present invention separately detects the amplitudes of the carrier chrominance signal and the luminance signal for the composite signal, controls one variable gain amplifier based on the amplitude information, and detects the luminance signal for the carrier chrominance signal as well. The dynamic range of the MU/D converter can also be optimized for the signal. Furthermore, the present invention provides an automatic gain control device for component signals, which controls the carrier chrominance signal and the luminance signal using separate variable gain amplifiers, thereby optimizing the dynamic range of the mu/D converter for both signals. realizable.
実施例
本発明の一実施例について図面を参照しながら説明する
。第１図は本発明の自動利得制御装置の構成を示したブ
ロック図である。第１図において、入力端子１から入力
されたコンポジット信号は、可変利得増幅器６で増幅さ
れてム／Ｄ変換器８でディジタル信号に変換される。輝
度信号レベル検出器９は、このディジタル信号に変換さ
れたコンポジット信号の輝度信号のレベルを検出し、予
め設定した輝度信号の基準レベルとの差を算出する。Embodiment An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an automatic gain control device according to the present invention. In FIG. 1, a composite signal input from an input terminal 1 is amplified by a variable gain amplifier 6 and converted to a digital signal by a MU/D converter 8. The brightness signal level detector 9 detects the level of the brightness signal of the composite signal converted into the digital signal, and calculates the difference from a preset reference level of the brightness signal.
輝度信号のレベルは、例えば水平同期信号のレベルから
検出する。色信号レベル検出器１１はディジタル信号に
変換されたコンポジット信号の搬送色信号のレベルを検
出し、予め設定した色信号の基準レベルとの差を算出す
る。搬送色信号レベルは、例えばバースト信号のレベル
から検出する。The level of the luminance signal is detected, for example, from the level of the horizontal synchronization signal. The color signal level detector 11 detects the level of the carrier color signal of the composite signal converted into a digital signal, and calculates the difference from a preset reference level of the color signal. The carrier color signal level is detected from the level of the burst signal, for example.
このようにして検出された輝度信号とその基準振幅値と
の誤差データはＤ／Ａ変換器１４でアナログ信号に変換
され、ローパスフィルタ１６を通って入力端子７から可
変利得増幅器５に入力されて輝度信号レベルが一定に保
たれる。また搬送色信号についても同様に搬送色信号と
その基準振幅値との誤差データはＤ／Ａ変換器１６でア
ナログ信号に変換され、ローパスフィルタ１７を通って
入力端子６から可変利得増幅器５に入力されて搬送色信
号レベルが一定に保たれる。その結果ム／Ｄ変換器８の
入力信号は輝度信号と搬送色信号の両方ともダイナミッ
クレンジが最適となる一定レベルに保たれる。The error data between the luminance signal detected in this way and its reference amplitude value is converted into an analog signal by the D/A converter 14, passed through the low-pass filter 16, and is inputted from the input terminal 7 to the variable gain amplifier 5. The brightness signal level is kept constant. Similarly, regarding the carrier color signal, error data between the carrier color signal and its reference amplitude value is converted into an analog signal by the D/A converter 16, passed through the low-pass filter 17, and inputted from the input terminal 6 to the variable gain amplifier 5. The carrier color signal level is kept constant. As a result, the input signals of the MU/D converter 8, both the luminance signal and the carrier color signal, are maintained at a constant level that optimizes the dynamic range.
つぎにＤ／Ａ変換器１４と１５、可変利得増幅器６の具
体例について第３図と第４図を参照しながら説明する。Next, specific examples of the D/A converters 14 and 15 and the variable gain amplifier 6 will be explained with reference to FIGS. 3 and 4.
第３図（ＩＬ）はＤ／Ａ変換器をＰＷＭ（パルス幅変調
）回路１日とローパスフィルタ１９で構成するときのブ
ロック図でアル。ローパスフィルタ１９は抵抗器Ｒとキ
ャパシタＣで構成している。ＰＷＭ回路１８は第３図Φ
）に示すような入力データに比例した幅τのパルスを一
定の周期Ｔ毎に発生する回路であり、このパルスがロー
パスフィルタ１９で濾波されると、その出力にはＰＷＭ
回路の入力に比例した電圧が現れるのでＤ／Ａ変換器と
して動作する。この構成によれば小規模の回路でＤ／Ａ
変換を行うことができる。FIG. 3 (IL) is a block diagram when the D/A converter is composed of a PWM (pulse width modulation) circuit 1 and a low-pass filter 19. The low-pass filter 19 is composed of a resistor R and a capacitor C. The PWM circuit 18 is shown in FIG.
) is a circuit that generates a pulse with a width τ proportional to the input data at regular intervals T, and when this pulse is filtered by the low-pass filter 19, the output is PWM.
Since a voltage proportional to the input of the circuit appears, it operates as a D/A converter. With this configuration, D/A can be performed using a small-scale circuit.
conversion can be performed.
第４図は可変利得増幅器５の実施例の具体的構成を示す
ブロック図である。バンドパスフィルタ２２は入力され
たコンポジット信号から搬送色信号を抜き出し可変利得
増幅器２３へおぐる。減算器２ｏは搬送色信号を入力コ
ンボジット信号から減算し、その出力を可変利得増幅器
２４におぐる。FIG. 4 is a block diagram showing a specific configuration of an embodiment of the variable gain amplifier 5. As shown in FIG. The bandpass filter 22 extracts the carrier color signal from the input composite signal and sends it to the variable gain amplifier 23. Subtractor 2o subtracts the carrier chrominance signal from the input composite signal and passes its output to variable gain amplifier 24.
従って可変利得増幅器２４の入力には輝度信号が可変利
得増幅器２３０入力には搬送色信号が入力される。可変
利得増幅器２４は入力端子７から入力された制御信号に
よって輝度信号の振幅を制御し、可変利得増幅器２３は
入力端子６から入力された制御信号によって搬送色信号
の振幅を制御する。この２つの可変利得増幅器２３と２
４の出力は加算器２１で加算されて出力される。この構
成を用いれば制御入力端子６と７に入力する信号で輝度
信号と搬送色信号の振幅を別々に制御できる。Therefore, the luminance signal is input to the input of the variable gain amplifier 24, and the carrier chrominance signal is input to the input of the variable gain amplifier 230. The variable gain amplifier 24 controls the amplitude of the luminance signal according to the control signal input from the input terminal 7, and the variable gain amplifier 23 controls the amplitude of the carrier color signal according to the control signal input from the input terminal 6. These two variable gain amplifiers 23 and 2
The outputs of 4 are added by an adder 21 and output. Using this configuration, the amplitudes of the luminance signal and the carrier color signal can be controlled separately by signals input to the control input terminals 6 and 7.
つぎに本発明の他の実施例について第２図を参照しなが
ら説明する。本実施例は第１の実施例の機能に加えコン
ポーネント信号にも対応できるものである。第１の実施
例と同一構成要素には同一番号を付した。初めにコンポ
ジット信号の場合について説明する。コンポジット信号
の場合は３箇所を除き第１の実施例と同じ動作をするの
で異なる点だけ説明する。Next, another embodiment of the present invention will be described with reference to FIG. In addition to the functions of the first embodiment, this embodiment can also support component signals. The same components as in the first embodiment are given the same numbers. First, the case of a composite signal will be explained. In the case of a composite signal, the operation is the same as in the first embodiment except for three points, so only the different points will be explained.
第１点はスイッチ回路４の接点がｂに接続されて入力端
子１から入力されたコンポジット信号が選択され可変利
得増幅器６に入力される点であり、第２点はム／Ｄ変換
された搬送色信号がスイッチ回路１ｏで接点がｂに接続
されて色信号レベル検出回路１１に送られる点であり、
第３点はスイッチ回路４０の接点がｂに接続されてロー
パスフィルタ１７の出力が入力端子６に入力される点で
ある。The first point is the point where the contact of the switch circuit 4 is connected to b and the composite signal input from the input terminal 1 is selected and input to the variable gain amplifier 6, and the second point is the point where the composite signal input from the input terminal 1 is selected and input to the variable gain amplifier 6. This is the point where the color signal is sent to the color signal level detection circuit 11 by connecting the contact point b of the switch circuit 1o,
The third point is the point where the contact of the switch circuit 40 is connected to b and the output of the low-pass filter 17 is input to the input terminal 6.
この３点の相違は、本実施例がコンポジット信号とコン
ポーネント信号の両方に対応するために付加した構成で
あシ、コンポジット信号については第１の実施例と同様
に輝度信号と搬送色信号の振幅に対してム／Ｄ変換器の
ダイナミックレンジが最適に保たれる。These three differences are due to the configuration added to this embodiment in order to support both composite signals and component signals.As for the composite signal, the amplitudes of the luminance signal and carrier chrominance signal are the same as in the first embodiment. The dynamic range of the MU/D converter is maintained optimally.
コンポーネント信号の場合について以下説明する。コン
ポーネント信号の輝度信号は入力端子２から、搬送色信
号は入力端子３から入力される。The case of component signals will be explained below. The luminance signal of the component signal is inputted from the input terminal 2, and the carrier color signal is inputted from the input terminal 3.
スイッチ回路４の接点は乙に接続されて輝度信号が選択
され可変利得増幅器５で増幅されム／Ｄ変換器８でディ
ジタルデータに変換される。搬送色信号は可変利得増幅
器１３で増幅されム／Ｄ変換器１２でディジタルデータ
に変換される。輝度信号レベル検出器９はこのディジタ
ル信号に変換されたコンポジット信号の輝度信号のレベ
ルを検出し、予め設定した輝度信号の基準レベルとの差
を算出する。色信号レベル検出器１１はスイッチ回路１
ｏで接点が已に接続されて選択された搬送色信号のレベ
ルを検出し、予め設定した搬送色信号の基準レベルとの
差を算出する。このようにして検出された輝度信号とそ
の基準振幅値との誤差データはＤ／Ａ変換器１４でアナ
ログ信号に変換され、ローパスフィルタ１６を通って入
力端子γから可変利得増幅器５に入力されて輝度信号レ
ベルが一定に保たれる。このときスイッチ回路４０の接
点をａに倒して固定の電圧を入力端子６に与え、可変利
得増幅器６の搬送色信号帯域の利得を一定にする。また
搬送色信号については搬送色信号とその基準振幅値との
誤差データはＤ／Ａ変換器１５でアナログ信号に変換さ
れ、ローパスフィルタ１７を通って可変利得増幅器１３
を制御し搬送色信号レベルを一定に保つ。その結果、ム
／Ｄ変換器８に入力される輝度信号とム／Ｄ変換器１２
に入力される搬送色信号は、それぞれのム／Ｄ変換器の
ダイナミックレンジに最適な振幅となる。A contact point of the switch circuit 4 is connected to B, and a luminance signal is selected, amplified by a variable gain amplifier 5, and converted into digital data by a MU/D converter 8. The carrier color signal is amplified by a variable gain amplifier 13 and converted into digital data by a MU/D converter 12. The brightness signal level detector 9 detects the level of the brightness signal of the composite signal converted into the digital signal, and calculates the difference between the brightness signal level and a preset reference level of the brightness signal. Color signal level detector 11 is switch circuit 1
The contacts are connected at point o to detect the level of the selected carrier color signal, and calculate the difference between it and a preset reference level of the carrier color signal. The error data between the luminance signal detected in this way and its reference amplitude value is converted into an analog signal by the D/A converter 14, passed through the low-pass filter 16, and is inputted to the variable gain amplifier 5 from the input terminal γ. The brightness signal level is kept constant. At this time, the contact point of the switch circuit 40 is set to a to apply a fixed voltage to the input terminal 6, thereby making the gain of the carrier color signal band of the variable gain amplifier 6 constant. Regarding the carrier color signal, the error data between the carrier color signal and its reference amplitude value is converted into an analog signal by the D/A converter 15, and then passed through the low-pass filter 17 to the variable gain amplifier 13.
control to keep the carrier color signal level constant. As a result, the luminance signal input to the MU/D converter 8 and the MU/D converter 12
The carrier chrominance signal inputted to each MU/D converter has an amplitude optimal for the dynamic range of each MU/D converter.
発明の効果
以上の様に本発明は、コンポジット信号に対しては搬送
色信号と輝度信号の振幅を別々に検出し、その振幅情報
によって１つの可変利得増幅器を制御して搬送色信号に
対しても輝度信号に対してもム／Ｄ変換器のダイナミッ
クレンジを最適にすることができる。また本発明はコン
ポーネント信号に対しては搬送色信号と輝度信号それぞ
れを別々の可変利得増幅器で制御して両方の信号に対し
てム／Ｄ変換器のダイナミックレンジを最適にすること
ができる。このとき色信号レベル検出器は入力信号がコ
ンポジット信号のときとコンポーネント信号のときで共
用できる利点がある。Effects of the Invention As described above, the present invention separately detects the amplitude of a carrier chrominance signal and a luminance signal for a composite signal, and controls one variable gain amplifier based on the amplitude information to detect the amplitude of a carrier chrominance signal and a luminance signal for a composite signal. The dynamic range of the MU/D converter can be optimized for both brightness and luminance signals. Further, in the present invention, for component signals, the carrier chrominance signal and the luminance signal are each controlled by separate variable gain amplifiers, so that the dynamic range of the MU/D converter can be optimized for both signals. At this time, there is an advantage that the color signal level detector can be used both when the input signal is a composite signal and when the input signal is a component signal.
さらに本発明ではＤ／Ａ変換器ｉＰＷＭ回路とローパス
フィルタで構成して回路を簡素化できる。Furthermore, according to the present invention, the circuit can be simplified by configuring the D/A converter iPWM circuit and a low-pass filter.
第１の可変利得増幅器についてはバンドパスフィルタと
２つの可変利得増幅器、減算器と加算器を組み合せて簡
単に構成できる。The first variable gain amplifier can be easily constructed by combining a bandpass filter, two variable gain amplifiers, a subtracter, and an adder.
第１図は本発明の第１の実施例に於ける自動利得制御装
置の構成を示したブロック図、第２図は本発明の第２の
実施例に於ける自動利得制御装置の構成を示したブロッ
ク図、第３図（２Ｌ）は本発明に於けるＤ／Ａ変換器の
構成を示したブロック図、第３図（ｂ）は（＆）に示し
たＰＷＭ回路の出力の波形を示す波形図、第４図は本発
明に於ける第１の可変利得増幅器の一実施例の構成を示
すブロック図、第６図は従来の自動利得制御装置の構成
を示すブロック図である。
５・・・・・・可変利得増幅器、９・・・・・・輝度信
号レベル検出器、１１・・・・・・色信号レベル検出器
、１９・・・・・・ローパスフィルタ、２３．２４・・
・・・・可変利得増幅器。
代理人の氏名 弁理士 中 尾 敏 男 ほか１名３＼
第３図
時開差
大でFIG. 1 is a block diagram showing the configuration of an automatic gain control device in a first embodiment of the invention, and FIG. 2 shows a configuration of an automatic gain control device in a second embodiment of the invention. Figure 3 (2L) is a block diagram showing the configuration of the D/A converter in the present invention, and Figure 3 (b) shows the waveform of the output of the PWM circuit shown in (&). FIG. 4 is a block diagram showing the configuration of an embodiment of the first variable gain amplifier according to the present invention, and FIG. 6 is a block diagram showing the configuration of a conventional automatic gain control device. 5... Variable gain amplifier, 9... Luminance signal level detector, 11... Color signal level detector, 19... Low pass filter, 23.24・・・
...Variable gain amplifier. Name of agent: Patent attorney Toshio Nakao and one other person
Claims (4)
利得と搬送色信号帯域の利得を独立して制御できる第１
の可変利得増幅器と、前記第１の可変利得増幅器の出力
をＡ／Ｄ変換する第１のＡ／Ｄ変換器と、前記第１のＡ
／Ｄ変換器の出力信号から輝度信号の振幅を検出し設定
された輝度信号の基準値との差を算出する第１の振幅検
出手段と、搬送色信号の振幅を検出し設定された搬送色
信号の基準値との差を算出する第２の振幅検出手段と、
前記第１の振幅検出手段の出力をＤ／Ａ変換する第１の
Ｄ／Ａ変換器と、前記第２の振幅検出手段の出力をＤ／
Ａ変換する第２のＤ／Ａ変換器とを具備し、前記第１の
可変利得増幅器の輝度信号帯域の利得は前記第１のＤ／
Ａ変換器の出力で制御し、搬送色信号帯域の利得は前記
第２のＤ／Ａ変換器の出力で制御するように構成したこ
とを特徴とする自動利得制御装置。(1) A first device that can independently control the gain of the luminance signal band and the gain of the carrier chrominance signal band of a composite video signal including the carrier chrominance signal.
a variable gain amplifier; a first A/D converter that A/D converts the output of the first variable gain amplifier;
a first amplitude detection means for detecting the amplitude of the luminance signal from the output signal of the /D converter and calculating the difference between the luminance signal and a set reference value; a second amplitude detection means for calculating the difference between the signal and the reference value;
A first D/A converter converts the output of the first amplitude detection means into D/A, and a first D/A converter converts the output of the second amplitude detection means into D/A.
a second D/A converter that performs A conversion, and the gain of the luminance signal band of the first variable gain amplifier is equal to the gain of the first D/A converter.
An automatic gain control device characterized in that the gain of the carrier color signal band is controlled by the output of the second D/A converter.
利得と搬送色信号帯域の利得を独立して制御できる第１
の可変利得増幅器と、入力される搬送色信号の利得を制
御できる第２の可変利得増幅器と、映像信号が搬送色信
号を含む複合映像信号として入力されたときを第１のモ
ードとし、前記映像信号が輝度信号と搬送色信号の２チ
ャンネルで入力されたときを第２のモードとするとき、
前記第１のモードのときは前記複合映像信号を前記第１
の可変利得増幅器へ送り、前記第２のモードのときは前
記輝度信号を前記第１の可変利得増幅器へ送る第１の切
り替え手段と、前記第１の可変利得増幅器の出力をＡ／
Ｄ変換する第１のＡ／Ｄ変換器と、前記第２の可変利得
増幅器の出力をＡ／Ｄ変換する第２のＡ／Ｄ変換器と、
前記第１のＡ／Ｄ変換器の出力信号から輝度信号の振幅
を検出し設定された輝度信号の基準値との差を算出する
第１の振幅検出手段と、前記第１のモードのときは前記
第１のＡ／Ｄ変換器の出力を選択し、前記第２のモード
のときは前記第２のＡ／Ｄ変換器の出力を選択する第２
の切り替え手段と、前記第２の切り替え手段の出力から
搬送色信号の振幅を検出し設定された搬送色信号の基準
値との差を算出する第２の振幅検出手段と、前記第１の
振幅検出手段の出力をＤ／Ａ変換する第１のＤ／Ａ変換
器と、前記第２の振幅検出手段の出力をＤ／Ａ変換する
第２のＤ／Ａ変換器を具備し、前記第１のモードのとき
は、前記第１の可変利得増幅器の輝度信号帯域の利得は
前記第１のＤ／Ａ変換器の出力で制御し、搬送色信号帯
域の利得は前記第２のＤ／Ａ変換器の出力で制御し、前
記第２のモードのときは前記第１の可変利得増幅器の輝
度信号帯域の利得を前記第１のＤ／Ａ変換器の出力で制
御し且つ搬送色信号帯域の利得を固定し、前記第２の可
変利得増幅器の利得を前記第２のＤ／Ａ変換器の利得で
制御するように構成したことを特徴とする自動利得制御
装置。(2) A first device that can independently control the gain of the luminance signal band and the gain of the carrier chrominance signal band of the composite video signal including the carrier chrominance signal.
a variable gain amplifier, a second variable gain amplifier capable of controlling the gain of the input carrier chrominance signal; When the second mode is when the signal is input in two channels, a luminance signal and a carrier color signal,
When in the first mode, the composite video signal is
a first switching means for transmitting the luminance signal to a variable gain amplifier of the first variable gain amplifier and transmitting the luminance signal to the first variable gain amplifier when in the second mode;
a first A/D converter that performs D conversion; a second A/D converter that performs A/D conversion of the output of the second variable gain amplifier;
a first amplitude detection means for detecting the amplitude of the brightness signal from the output signal of the first A/D converter and calculating a difference between the brightness signal and a set reference value; a second A/D converter that selects the output of the first A/D converter, and selects the output of the second A/D converter when in the second mode;
a second amplitude detection means for detecting the amplitude of the carrier color signal from the output of the second switching means and calculating a difference between a set reference value of the carrier color signal, and the first amplitude a first D/A converter that D/A converts the output of the detection means; and a second D/A converter that D/A converts the output of the second amplitude detection means; In this mode, the gain of the luminance signal band of the first variable gain amplifier is controlled by the output of the first D/A converter, and the gain of the carrier chrominance signal band is controlled by the output of the second D/A converter. When in the second mode, the gain of the luminance signal band of the first variable gain amplifier is controlled by the output of the first D/A converter, and the gain of the carrier chrominance signal band is controlled by the output of the first D/A converter. An automatic gain control device characterized in that the gain of the second variable gain amplifier is controlled by the gain of the second D/A converter.
調）回路とその出力を濾波するアナログローパスフィル
タで構成したことを特徴とする請求項（１）または請求
項（２）記載の自動利得制御装置。(3) Claim (1) or (2) characterized in that the first and second D/A converters are constituted by a PWM (pulse width modulation) circuit and an analog low-pass filter that filters the output thereof. Automatic gain control device as described.
を抜き出すバンドパスフィルタと前記入力信号から前記
バンドパスフィルタの出力信号を減じる減算回路と、前
記減算回路の出力信号の利得を制御する第３の可変利得
増幅器と前記バンドパスフィルタの出力の利得を制御す
る第４の可変利得増幅器と第３と第４の可変利得増幅器
の出力を加算する加算回路からなることを特徴とする請
求項（１）または請求項（２）記載の自動利得制御装置
。(4) The first variable gain amplifier includes a bandpass filter that extracts a carrier color signal from the input signal, a subtraction circuit that subtracts the output signal of the bandpass filter from the input signal, and controls the gain of the output signal of the subtraction circuit. Claim comprising: a third variable gain amplifier; a fourth variable gain amplifier that controls the gain of the output of the bandpass filter; and an adder circuit that adds the outputs of the third and fourth variable gain amplifiers. The automatic gain control device according to (1) or claim (2).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8156588A JPH01254088A (en) | 1988-04-01 | 1988-04-01 | Automatic gain controller |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8156588A JPH01254088A (en) | 1988-04-01 | 1988-04-01 | Automatic gain controller |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01254088A true JPH01254088A (en) | 1989-10-11 |
Family
ID=13749815
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8156588A Pending JPH01254088A (en) | 1988-04-01 | 1988-04-01 | Automatic gain controller |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01254088A (en) |
-
1988
- 1988-04-01 JP JP8156588A patent/JPH01254088A/en active Pending
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