JPH0326008A - Automatic gain control circuit - Google Patents
Automatic gain control circuitInfo
- Publication number
- JPH0326008A JPH0326008A JP15959189A JP15959189A JPH0326008A JP H0326008 A JPH0326008 A JP H0326008A JP 15959189 A JP15959189 A JP 15959189A JP 15959189 A JP15959189 A JP 15959189A JP H0326008 A JPH0326008 A JP H0326008A
- Authority
- JP
- Japan
- Prior art keywords
- input signal
- variable gain
- voltage
- signal level
- level
- 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
- 238000010586 diagram Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 210000004243 sweat Anatomy 0.000 description 1
Landscapes
- Control Of Amplification And Gain Control (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は自動利得制御回路，特に無線通信装置などに用
いられる可変利得増幅器の自動利得制御を行う回路構或
に関する．
［従来の技術］
従来から、無線通信装置などに用いられる可変利得増幅
器をフィードバック制御することが周知であり、このた
めの自動利得制御回路が第２図に示されている．
図において、入力端子ｌから入力された信号は可変利得
増幅器３により増幅され，出力端子２から出力されるが
、この可変利得増幅器２の利得をフィードバック制御す
るために検波器４および差動増幅器５が設けられている
．
すなわち、可変利得増幅器２の出力信号は検波器４で検
波され，この検波電圧が差動増幅器５に入力されると，
誤差電圧に対する制御電圧が出力されることになり、こ
の制御電圧によって可変利得増＠器３の利得が制御され
る．したがって、出力端子２からは一定レベルの信号が
出力されることになる．
，［解決すべき課題］
上述した従来の自動利得制御回路では，入力信号がない
場合，あるいは入力信号のレベルが非常に低い場合には
可変利得増幅器３の増幅度が最大となっており、入力信
号が入力された瞬間、あるいは瞬時に入力信号′レベル
が高くなった場合に可変利得増幅器３からは定常に出力
レベルより高いレベルの信号が瞬時に出力されることに
なる．そのため，その後自動利得制御回路により定常の
出力レベルに戻っても、入力信号の急激な変動により隣
接する他の信号への周波数による干渉が生じるという問
題がある．
第４図に示されるように、例えば入力信号の立上り時間
をｔ１とすると、差動増幅器５の電Ｉｔ！圧（Ｖ）は実
線のように一定であるが、可変利得増幅器３の利得を制
御するための差動増幅器５の制御電圧（Ｖａ）は立上り
時間ｔ１の後に破線にように低下する．したがって，可
変利得増幅器３の出力信号レベルも上記制御電圧に比例
して変化することになり、入力信号の立上りの瞬間では
利得最大の信号が出力される．
本発明は上記問題点にかんがみてなされたもので、その
目的は，入力信号の急激な変動により利得が最大となる
のを防止し，他の信号への干渉をなくすことのできる自
動利得制御回路を提供することにある．
［課題の解決手段］
上記目的を達成するために、本発明は，可変利得増幅器
の出力信号レベルを検出する検波器と、この検波器出力
の誤差電圧に対する制御電圧を出力する差動増幅器とを
備え，上記制御電圧により可変利得増幅器の利得をフィ
ードバック制御する自動利得制御回路において，上記可
変利得増幅器の入力信号レベルを検出する検波器と、こ
の検波器で検出された入力信号レベルと予め設定した所
定値とを比較する電圧比較器と，この電圧比較器出力に
基づいて上記入力信号レベルが所定値よりも小さいとき
は、上記差動増幅器の電源電圧をオフし所定値よりも大
きいときはオンする制御器と、この制御器のオン・オフ
動作の時定数を決める時定数回路を設けた構成としてあ
る．［作用］
上記構戊によれば、検波器により可変利得増幅器の入力
信号レベルが検出され、この入力信号レベルは電圧比較
器により所定値と比較される．そして、上記入力信号レ
ベルが所定値よりも小さいときは制御器により差動増幅
器の電源電圧がオフされ、可変利得増幅器の利得は最少
となる．一方、信号レベルが所定値よりも大きくなった
とき、すなわち入力信号に急激な変動があったときは制
御器により差動増幅器の電源電圧がオンされ、この電源
電圧は時定数回路の時定数に基づいて徐々に上昇する．
したがって，可変利得制御のための制御電圧も徐々に上
昇するとこになり、その後は定常の利得制御が行われる
．
［実施例］
以下、本発明の一実施例について図面を参照しながら詳
細に説明する．
第１図には、実施例に係る自動利得制御回路の回路構成
が示されており、入力端子ｌと出力端子２の間に、可変
利得増幅器３、検波器４および差動増幅器５を備え、可
変利得増幅器３の利得をフィードバック制御することに
ついては従来（第２図）と同様である．
実施例では，上記可変利得増幅器３の入力側に入力信号
レベルを検出する検波器６を接続し、この検波器６には
人力信号レベルと予め設定してある所定値とを比較する
電圧比較器７，この電圧比較器７の出力に基づいて差動
増幅器５の電源電圧を十ン◆才フ制御する制御器８、上
記電源１１！汗のオン・オフ動作の時定数を決定する時
定数回路９を接続する．
実施例は以上の構威からなり，その作用を第３図を参照
しながら説明する．
まず，可変利得増幅器３への入力信号が所定値よりも小
さいことが電圧比較器７で検出された場合には，差動増
輻器５の電源電圧はオフされ、第３図に示されるように
２可変利得増幅器３の利得制御のための差動増輻器５の
制御電圧も０（０≦ｔ≦ｊ＋）となる。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic gain control circuit, and particularly to a circuit structure for performing automatic gain control of a variable gain amplifier used in a wireless communication device or the like. [Prior Art] It has been well known to perform feedback control on variable gain amplifiers used in wireless communication devices, and an automatic gain control circuit for this purpose is shown in FIG. In the figure, a signal input from an input terminal 1 is amplified by a variable gain amplifier 3 and output from an output terminal 2. In order to feedback control the gain of the variable gain amplifier 2, a detector 4 and a differential amplifier 5 are used. is provided. That is, the output signal of the variable gain amplifier 2 is detected by the detector 4, and when this detected voltage is input to the differential amplifier 5,
A control voltage for the error voltage is output, and the gain of the variable gain amplifier 3 is controlled by this control voltage. Therefore, a signal at a constant level is output from output terminal 2. , [Problem to be solved] In the conventional automatic gain control circuit described above, when there is no input signal or when the level of the input signal is very low, the amplification degree of the variable gain amplifier 3 is maximized, and the input At the moment when a signal is input, or when the level of the input signal becomes high instantaneously, the variable gain amplifier 3 instantaneously outputs a signal constantly at a level higher than the output level. Therefore, even if the automatic gain control circuit returns to a steady output level, there is a problem in that rapid fluctuations in the input signal cause frequency interference with other adjacent signals. As shown in FIG. 4, for example, if the rise time of the input signal is t1, the voltage It! of the differential amplifier 5! The voltage (V) is constant as shown by the solid line, but the control voltage (Va) of the differential amplifier 5 for controlling the gain of the variable gain amplifier 3 decreases as shown by the broken line after the rise time t1. Therefore, the output signal level of the variable gain amplifier 3 also changes in proportion to the control voltage, and the signal with the maximum gain is output at the instant of the rise of the input signal. The present invention has been made in view of the above-mentioned problems, and its purpose is to prevent the gain from reaching its maximum due to sudden fluctuations in the input signal, and to eliminate interference with other signals as an automatic gain control circuit. The goal is to provide the following. [Means for Solving the Problems] In order to achieve the above object, the present invention includes a detector that detects the output signal level of a variable gain amplifier, and a differential amplifier that outputs a control voltage for the error voltage of the output of the detector. In an automatic gain control circuit that feedback-controls the gain of the variable gain amplifier using the control voltage, there is provided a detector for detecting the input signal level of the variable gain amplifier, and a preset value for the input signal level detected by the detector. A voltage comparator compares the input signal level with a predetermined value, and turns off the power supply voltage of the differential amplifier when the input signal level is smaller than the predetermined value based on the output of this voltage comparator, and turns it on when it is higher than the predetermined value. The configuration includes a controller that controls the power output, and a time constant circuit that determines the time constant of the on/off operation of this controller. [Operation] According to the above structure, the input signal level of the variable gain amplifier is detected by the wave detector, and this input signal level is compared with a predetermined value by the voltage comparator. When the input signal level is lower than a predetermined value, the power supply voltage of the differential amplifier is turned off by the controller, and the gain of the variable gain amplifier is minimized. On the other hand, when the signal level becomes larger than a predetermined value, that is, when there is a sudden change in the input signal, the controller turns on the power supply voltage of the differential amplifier, and this power supply voltage changes to the time constant of the time constant circuit. gradually increases based on
Therefore, the control voltage for variable gain control also increases gradually, and after that, steady gain control is performed. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a circuit configuration of an automatic gain control circuit according to an embodiment, which includes a variable gain amplifier 3, a detector 4, and a differential amplifier 5 between an input terminal 1 and an output terminal 2, Feedback control of the gain of the variable gain amplifier 3 is the same as the conventional method (Fig. 2). In the embodiment, a detector 6 for detecting the input signal level is connected to the input side of the variable gain amplifier 3, and the detector 6 is equipped with a voltage comparator for comparing the human input signal level with a predetermined value. 7. A controller 8 that controls the power supply voltage of the differential amplifier 5 based on the output of the voltage comparator 7; and the power supply 11! Connect a time constant circuit 9 that determines the time constant of sweat on/off operation. The embodiment consists of the above structure, and its operation will be explained with reference to Fig. 3. First, when the voltage comparator 7 detects that the input signal to the variable gain amplifier 3 is smaller than a predetermined value, the power supply voltage of the differential amplifier 5 is turned off, as shown in FIG. Also, the control voltage of the differential amplifier 5 for controlling the gain of the variable gain amplifier 3 becomes 0 (0≦t≦j+).
一方、入力信号が急激に変動して電圧比較器７により入
力信号レベルが所定値を超えたことを検出したとき，す
なわち第３図において１＝１＋のときには，差動増幅器
５の電源電圧がオンされ、実線のように時定数回路９の
時定数で徐々に電圧が立ち上げられる．したがって、可
変利得増幅器３の制ｇｌ’ｉＷ圧も破線のように徐々に
電圧■δまで１二昇することになり、町変利得増幅器３
の利得も最小から正常なレベルに制御され、利得最大と
なることなく安定した増幅作用が行われる，［発明の効
果］
以上説明したように、本発明によれば、可変利得増幅器
の入力信号を検出し，入力信号レベルが所定値を超える
か否かにより差動増幅器の電源電圧をオン●才フ制御す
るようにしたので，入力信号の急激なレベル変動に対し
ても可変利得増幅器の出力信号レベルを安定に制御でき
、無線通信装置などにおいては隣接するチャンネルの信
号に対する周波数の干渉を防止できる効果がある。On the other hand, when the input signal fluctuates rapidly and the voltage comparator 7 detects that the input signal level exceeds a predetermined value, that is, when 1=1+ in FIG. 3, the power supply voltage of the differential amplifier 5 is turned on. The voltage is gradually raised by the time constant of the time constant circuit 9 as shown by the solid line. Therefore, the control gl'iW voltage of the variable gain amplifier 3 also gradually rises by 12 to the voltage ■δ as shown by the broken line, and the variable gain amplifier 3
The gain of the variable gain amplifier is also controlled from the minimum to the normal level, and stable amplification is performed without reaching the maximum gain. [Effects of the Invention] As explained above, according to the present invention, the input signal of the variable gain amplifier can be controlled from the minimum to the normal level. Since the power supply voltage of the differential amplifier is controlled on and off depending on whether the input signal level exceeds a predetermined value, the output signal of the variable gain amplifier can be controlled even when the input signal level fluctuates rapidly. The level can be controlled stably, and in wireless communication devices, etc., it is effective in preventing frequency interference with signals of adjacent channels.
第１図は本発明の実施例に係る自動利得制御回路の構或
を示す回路ブロック図、第２図は従来の自動利得制御回
路の構戒を示す回路ブロック図第３図は第１図実施例で
の差動増幅器電源電圧と可変利得増幅器制御電圧の変化
を示すグラフ図、第４図は従来の回路での差動増幅器電
源電圧と可変利得増幅器制御電圧の変化を示すグラフ図
である．
１：入力端子 ２：出力端子FIG. 1 is a circuit block diagram showing the structure of an automatic gain control circuit according to an embodiment of the present invention, and FIG. 2 is a circuit block diagram showing the structure of a conventional automatic gain control circuit. FIG. 3 is a circuit block diagram showing the structure of a conventional automatic gain control circuit. FIG. 4 is a graph showing changes in the differential amplifier power supply voltage and variable gain amplifier control voltage in the conventional circuit. 1: Input terminal 2: Output terminal
Claims (1)
この検波器出力の誤差電圧に対する制御電圧を出力する
差動増幅器とを備え、上記制御電圧により可変利得増幅
器の利得をフィードバック制御する自動利得制御回路に
おいて、上記可変利得増幅器の入力信号レベルを検出す
る検波器と、この検波器で検出された入力信号レベルと
予め設定した所定値とを比較する電圧比較器と、この電
圧比較器出力に基づいて上記入力信号レベルが所定値よ
りも小さいときは、上記差動増幅器の電源電圧をオフし
所定値よりも大きいときはオンする制御器と、この制御
器のオン、オフ動作の時定数を決める時定数回路とを設
けたことを特徴とする自動利得制御回路。a detector that detects the output signal level of the variable gain amplifier;
an automatic gain control circuit that includes a differential amplifier that outputs a control voltage for the error voltage of the detector output, and that feedback controls the gain of the variable gain amplifier using the control voltage, detecting the input signal level of the variable gain amplifier; a wave detector; a voltage comparator that compares the input signal level detected by the wave detector with a predetermined value; and when the input signal level is smaller than the predetermined value based on the output of the voltage comparator; The automatic gain is characterized by being provided with a controller that turns off the power supply voltage of the differential amplifier and turns it on when it is larger than a predetermined value, and a time constant circuit that determines the time constant of the on and off operations of the controller. control circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15959189A JPH0326008A (en) | 1989-06-23 | 1989-06-23 | Automatic gain control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15959189A JPH0326008A (en) | 1989-06-23 | 1989-06-23 | Automatic gain control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0326008A true JPH0326008A (en) | 1991-02-04 |
Family
ID=15697053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15959189A Pending JPH0326008A (en) | 1989-06-23 | 1989-06-23 | Automatic gain control circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0326008A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07288435A (en) * | 1994-04-14 | 1995-10-31 | Nec Corp | Output level control circuit |
| JP2007012444A (en) * | 2005-06-30 | 2007-01-18 | Sumitomo Electric Ind Ltd | Insulating film for flat cable and flat cable using it |
-
1989
- 1989-06-23 JP JP15959189A patent/JPH0326008A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07288435A (en) * | 1994-04-14 | 1995-10-31 | Nec Corp | Output level control circuit |
| JP2007012444A (en) * | 2005-06-30 | 2007-01-18 | Sumitomo Electric Ind Ltd | Insulating film for flat cable and flat cable using it |
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