JPH09130206A - Characteristic frequency adjustment device for active filter - Google Patents
Characteristic frequency adjustment device for active filterInfo
- Publication number
- JPH09130206A JPH09130206A JP31004695A JP31004695A JPH09130206A JP H09130206 A JPH09130206 A JP H09130206A JP 31004695 A JP31004695 A JP 31004695A JP 31004695 A JP31004695 A JP 31004695A JP H09130206 A JPH09130206 A JP H09130206A
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- Japan
- Prior art keywords
- characteristic frequency
- pass filter
- filter
- characteristic
- reference frequency
- 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.)
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Links
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】この発明は、能動フィルタ、
特に移動通信端末などに用いられ、その端末などの小型
化のために集積回路化された能動フィルタの特性周波数
を調整する装置に関する。TECHNICAL FIELD The present invention relates to an active filter,
In particular, the present invention relates to a device used for a mobile communication terminal or the like, and adjusting the characteristic frequency of an active filter integrated into a circuit for downsizing the terminal or the like.
【0002】[0002]
【従来の技術】フィルタの周波数特性は、相対的な周波
数特性と、特性周波数の、2つに分けて考えることがで
きる。2. Description of the Related Art The frequency characteristic of a filter can be considered as being divided into a relative frequency characteristic and a characteristic frequency.
【0003】相対的な周波数特性とは、例えば、5次バ
ターワース型低域通過フィルタというように、フィルタ
のトポロジー、そのパラメータ、通過帯域の種類により
決定される、いわばフィルタ周波数特性の形状のことを
指す。The relative frequency characteristic is, for example, the shape of the filter frequency characteristic, which is determined by the topology of the filter, its parameters, and the type of the pass band, such as a fifth-order Butterworth type low-pass filter. Point to.
【0004】これに対して、特性周波数とは、このよう
な相対的な周波数特性の定まっているフィルタを、周波
数領域上のどの位置に配置するかを決定することができ
る、特異点の周波数のことを指す。例えば、バターワー
ス型フィルタにおいては、3dB減衰極の周波数は、こ
こで述べるところの特性周波数であると言える。On the other hand, the characteristic frequency is a frequency of a singular point which can determine at which position in the frequency domain the filter having such a fixed frequency characteristic is arranged. It means that. For example, in a Butterworth filter, the frequency of the 3 dB attenuation pole can be said to be the characteristic frequency described here.
【0005】一般に、集積回路の製造過程におけるばら
つきは、抵抗で±十数パーセント、容量で±数パーセン
トであり、抵抗と容量によって構成されるフィルタの特
性周波数は、±20パーセント以上のばらつきを生じ
る。Generally, variations in the manufacturing process of an integrated circuit are ± 10% for resistors and ± 10% for capacitors, and the characteristic frequency of a filter formed by resistors and capacitors varies by ± 20% or more. .
【0006】そのため、従来、能動フィルタを集積回路
化する場合には、その集積回路化された能動フィルタの
特性周波数の精度を向上させるために、能動フィルタに
対して図3に示すような特性周波数調整装置が設けられ
ることがあった。Therefore, conventionally, when an active filter is integrated into a circuit, in order to improve the accuracy of the characteristic frequency of the integrated circuit active filter, the characteristic frequency as shown in FIG. Adjustment devices were sometimes provided.
【0007】この特性周波数調整装置20は、基準周波
数信号発生器21、帯域通過フィルタ22、および位相
比較回路23を備え、基準周波数信号発生器21からの
基準周波数信号Srが、帯域通過フィルタ22の入力端
子22iに供給され、その帯域通過フィルタ22の出力
信号Sbと、基準周波数信号発生器21からの基準周波
数信号Srが、位相比較回路23に供給されて、位相比
較回路23において両者の位相が比較され、その比較結
果の出力信号Scが、帯域通過フィルタ22の、特性周
波数を変化させる制御端子22cに供給される。The characteristic frequency adjusting device 20 comprises a reference frequency signal generator 21, a band pass filter 22 and a phase comparison circuit 23. The reference frequency signal Sr from the reference frequency signal generator 21 is supplied to the band pass filter 22. The output signal Sb of the band-pass filter 22 and the reference frequency signal Sr from the reference frequency signal generator 21 are supplied to the input terminal 22i, and are supplied to the phase comparison circuit 23. The output signal Sc as a result of the comparison is supplied to the control terminal 22c of the bandpass filter 22 for changing the characteristic frequency.
【0008】そして、その位相比較回路23の出力信号
Scが、特性周波数調整装置20の出力の調整用信号と
して、特性周波数が調整されるべき能動フィルタ2の、
特性周波数を変化させる制御端子2cに供給される。The output signal Sc of the phase comparison circuit 23 is used as an adjustment signal for the output of the characteristic frequency adjusting device 20 of the active filter 2 whose characteristic frequency is to be adjusted.
It is supplied to the control terminal 2c for changing the characteristic frequency.
【0009】ここで、帯域通過フィルタ22は、その振
幅特性を図4(A)に示し、その位相特性を図4(B)
に示すように、比較的、尖鋭度Qの低い、特性周波数が
Foのフィルタである。Here, the bandpass filter 22 shows its amplitude characteristic in FIG. 4 (A) and its phase characteristic in FIG. 4 (B).
As shown in (1), the filter has a relatively low sharpness Q and a characteristic frequency of Fo.
【0010】したがって、基準周波数信号発生器21か
らの基準周波数信号Srは、帯域通過フィルタ22を通
過することにより、図4の特性に従って、その基準周波
数frと帯域通過フィルタ22の特性周波数Foとの差
Δfに応じた位相回転を受ける。Therefore, the reference frequency signal Sr from the reference frequency signal generator 21 passes through the band pass filter 22 to obtain the reference frequency fr and the characteristic frequency Fo of the band pass filter 22 according to the characteristic of FIG. It undergoes phase rotation according to the difference Δf.
【0011】そして、帯域通過フィルタ22は、この位
相回転量がゼロとなるように、位相比較回路23の出力
信号Scによって、その特性周波数Foが変えられる。
したがって、帯域通過フィルタ22の特性周波数Fo
は、基準周波数frに連動することになる。The characteristic frequency Fo of the bandpass filter 22 is changed by the output signal Sc of the phase comparison circuit 23 so that the phase rotation amount becomes zero.
Therefore, the characteristic frequency Fo of the bandpass filter 22 is
Will be linked to the reference frequency fr.
【0012】この場合、帯域通過フィルタ22の特性周
波数Foと、能動フィルタ2の特性周波数Faとの間
に、互いに強い相関を与えるように、それぞれの回路を
構成することで、上記のように位相比較回路23の出力
信号Scにより帯域通過フィルタ22の特性周波数Fo
が制御され、かつその位相比較回路23の出力信号Sc
により能動フィルタ2の特性周波数Faが調整されるこ
とによって、能動フィルタ2の特性周波数Faも基準周
波数frに連動することになり、能動フィルタ2の特性
周波数Faを調整することができる。In this case, by configuring the respective circuits such that the characteristic frequency Fo of the bandpass filter 22 and the characteristic frequency Fa of the active filter 2 are strongly correlated with each other, the phase is increased as described above. The characteristic frequency Fo of the bandpass filter 22 is determined by the output signal Sc of the comparison circuit 23.
Is controlled and the output signal Sc of the phase comparison circuit 23 is controlled.
By adjusting the characteristic frequency Fa of the active filter 2 by the above, the characteristic frequency Fa of the active filter 2 also interlocks with the reference frequency fr, and the characteristic frequency Fa of the active filter 2 can be adjusted.
【0013】[0013]
【発明が解決しようとする課題】しかし、上述した特性
周波数調整装置20で、能動フィルタ2の特性周波数F
aの調整精度を十分に確保するには、帯域通過フィルタ
22の特性周波数Foの近傍における周波数の変化に対
する位相の変化の割合を、十分大きくする必要がある。However, in the characteristic frequency adjusting device 20 described above, the characteristic frequency F of the active filter 2 is reduced.
In order to sufficiently secure the adjustment accuracy of a, it is necessary to sufficiently increase the ratio of the phase change to the frequency change in the vicinity of the characteristic frequency Fo of the bandpass filter 22.
【0014】そのため、帯域通過フィルタ22として、
その振幅特性を図2(A)に示し、その位相特性を図2
(B)に示すように、尖鋭度Qの高いものを用いること
が考えられる。Therefore, as the bandpass filter 22,
Its amplitude characteristic is shown in FIG. 2 (A), and its phase characteristic is shown in FIG.
As shown in (B), it is possible to use a material having a high sharpness Q.
【0015】しかしながら、このように帯域通過フィル
タ22の尖鋭度Qを高くすると、第1に、尖鋭度Qを高
くするに従って、尖鋭度Qの値に多くのパラメータが関
与するようになるため、尖鋭度Qの絶対値の制御が困難
になり、その結果、帯域通過フィルタ22の出力信号S
bの振幅がばらついて、位相比較回路23が正しく動作
しなくなる。However, if the sharpness Q of the bandpass filter 22 is increased in this way, firstly, as the sharpness Q is increased, many parameters are involved in the value of the sharpness Q, and thus the sharpness is increased. It becomes difficult to control the absolute value of the degree Q, and as a result, the output signal S of the bandpass filter 22 is
The amplitude of b varies and the phase comparison circuit 23 does not operate correctly.
【0016】第2に、帯域通過フィルタ22の尖鋭度Q
を高くすると、基準周波数frと帯域通過フィルタ22
の特性周波数Foとの差Δfが大きいときには、帯域通
過フィルタ22の出力信号Sbの振幅が極端に小さくな
り、逆に差Δfが小さいときには、出力信号Sbの振幅
が極端に大きくなって、位相比較回路23に供給される
信号Sbの振幅が大きく変動するため、やはり位相比較
回路23が正しく動作しなくなる。Second, the sharpness Q of the bandpass filter 22.
Is increased, the reference frequency fr and the band pass filter 22
When the difference Δf from the characteristic frequency Fo is large, the amplitude of the output signal Sb of the bandpass filter 22 is extremely small. Conversely, when the difference Δf is small, the amplitude of the output signal Sb is extremely large and the phase comparison is performed. Since the amplitude of the signal Sb supplied to the circuit 23 largely fluctuates, the phase comparison circuit 23 also does not operate properly.
【0017】そのため、従来においては、上述したよう
に帯域通過フィルタ22として尖鋭度Qの低いものを用
いざるを得ず、そのため能動フィルタ2の特性周波数F
aの調整精度を十分に確保することができなかった。Therefore, in the prior art, as described above, the bandpass filter 22 having a low sharpness Q must be used, and therefore the characteristic frequency F of the active filter 2 is required.
It was not possible to sufficiently secure the adjustment accuracy of a.
【0018】この発明は、帯域通過フィルタを通過した
基準周波数信号と、通過しない基準周波数信号との位相
を比較し、その比較結果出力によって、帯域通過フィル
タの特性周波数を制御するとともに、特性周波数が調整
されるべき能動フィルタの特性周波数を調整する、能動
フィルタの特性周波数調整装置において、帯域通過フィ
ルタの尖鋭度Qを高くした場合においても、位相比較回
路が常に正しく動作するようにし、帯域通過フィルタの
尖鋭度Qを高くすることによって、能動フィルタの特性
周波数の調整精度を十分に確保することができるように
したものである。According to the present invention, the reference frequency signal that has passed through the band pass filter and the reference frequency signal that does not pass are compared in phase, and the characteristic frequency of the band pass filter is controlled by the output of the comparison result. In a characteristic frequency adjusting device for an active filter for adjusting a characteristic frequency of an active filter to be adjusted, a phase comparison circuit is always operated correctly even when the sharpness Q of the bandpass filter is increased, By increasing the sharpness Q of, the adjustment accuracy of the characteristic frequency of the active filter can be sufficiently ensured.
【0019】[0019]
【課題を解決するための手段】この発明では、基準周波
数信号発生器と帯域通過フィルタの入力端子との間に、
帯域通過フィルタに入力される基準周波数信号のレベル
を制御する利得制御回路を挿入接続するとともに、帯域
通過フィルタの出力側に、帯域通過フィルタの出力信号
レベルを検出するレベル検出回路を設け、そのレベル検
出回路の出力信号によって、帯域通過フィルタの出力信
号レベルが一定となるように、上記の利得制御回路を制
御する。According to the present invention, between the reference frequency signal generator and the input terminal of the band pass filter,
A gain control circuit that controls the level of the reference frequency signal input to the bandpass filter is inserted and connected, and a level detection circuit that detects the output signal level of the bandpass filter is provided on the output side of the bandpass filter. The gain control circuit is controlled by the output signal of the detection circuit so that the output signal level of the bandpass filter becomes constant.
【0020】上記のように構成した、この発明の特性周
波数調整装置においては、帯域通過フィルタの尖鋭度Q
を高くした場合においても、その尖鋭度Qのばらつきや
帯域通過フィルタの振幅特性による、帯域通過フィルタ
の出力振幅のばらつきや変動が抑止される。In the characteristic frequency adjusting device of the present invention configured as described above, the sharpness Q of the band pass filter is obtained.
Even when the value is increased, variations or fluctuations in the output amplitude of the bandpass filter are suppressed due to variations in the sharpness Q or the amplitude characteristics of the bandpass filter.
【0021】したがって、位相比較回路に供給される信
号の振幅が常に一定となり、位相比較回路は常に正しく
動作する。そのため、帯域通過フィルタの尖鋭度Qを高
くすることによって、能動フィルタの特性周波数の調整
精度を十分に確保することができる。Therefore, the amplitude of the signal supplied to the phase comparison circuit is always constant, and the phase comparison circuit always operates correctly. Therefore, by increasing the sharpness Q of the bandpass filter, it is possible to sufficiently secure the adjustment accuracy of the characteristic frequency of the active filter.
【0022】[0022]
【発明の実施の形態】図1は、この発明の特性周波数調
整装置の一実施形態を示し、その特性周波数調整装置1
0は、基準周波数信号発生器11、帯域通過フィルタ1
2、位相比較回路13、利得制御回路14、およびレベ
ル検出回路15を備える。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a characteristic frequency adjusting device of the present invention.
0 is the reference frequency signal generator 11 and the band pass filter 1
2, a phase comparison circuit 13, a gain control circuit 14, and a level detection circuit 15.
【0023】基準周波数信号発生器11からの基準周波
数信号Srは、一方で位相比較回路13の一方の入力端
子に、そのまま供給されるとともに、他方で利得制御回
路14の入力端子に供給され、その利得制御回路14の
出力信号である、レベル制御された基準周波数信号Sg
が、帯域通過フィルタ12の入力端子12iに供給さ
れ、その帯域通過フィルタ12の出力信号Sbが、位相
比較回路13の他方の入力端子に供給される。The reference frequency signal Sr from the reference frequency signal generator 11 is directly supplied to one input terminal of the phase comparison circuit 13 on the one hand and to the input terminal of the gain control circuit 14 on the other hand, The level-controlled reference frequency signal Sg, which is the output signal of the gain control circuit 14.
Is supplied to the input terminal 12i of the bandpass filter 12, and the output signal Sb of the bandpass filter 12 is supplied to the other input terminal of the phase comparison circuit 13.
【0024】さらに、帯域通過フィルタ12の出力信号
Sbが、レベル検出回路15に供給されて、レベル検出
回路15において、出力信号Sbのレベルが検出され、
そのレベル検出回路15の出力信号Sdが、利得制御回
路14の制御端子に供給されて、帯域通過フィルタ12
の出力信号Sbのレベルが一定となるように、利得制御
回路14の利得、すなわち利得制御回路14の出力信号
Sgのレベルが負帰還制御される。Further, the output signal Sb of the bandpass filter 12 is supplied to the level detection circuit 15, and the level detection circuit 15 detects the level of the output signal Sb.
The output signal Sd of the level detection circuit 15 is supplied to the control terminal of the gain control circuit 14, and the band pass filter 12 is supplied.
The gain of the gain control circuit 14, that is, the level of the output signal Sg of the gain control circuit 14 is negatively feedback-controlled so that the level of the output signal Sb of is constant.
【0025】そして、位相比較回路13において、基準
周波数信号発生器11からの基準周波数信号Srと、帯
域通過フィルタ12の出力信号Sbの位相が比較され、
その位相比較回路13の出力信号Scが、帯域通過フィ
ルタ12の、特性周波数を変化させる制御端子12cに
供給される。Then, the phase comparison circuit 13 compares the phase of the reference frequency signal Sr from the reference frequency signal generator 11 with the phase of the output signal Sb of the band pass filter 12,
The output signal Sc of the phase comparison circuit 13 is supplied to the control terminal 12c of the bandpass filter 12 that changes the characteristic frequency.
【0026】さらに、その位相比較回路13の出力信号
Scが、特性周波数調整装置10の出力の調整用信号と
して、特性周波数が調整されるべき能動フィルタ1の、
特性周波数を変化させる制御端子1cに供給される。Further, the output signal Sc of the phase comparison circuit 13 serves as an adjustment signal for the output of the characteristic frequency adjusting device 10 of the active filter 1 whose characteristic frequency is to be adjusted.
It is supplied to the control terminal 1c for changing the characteristic frequency.
【0027】帯域通過フィルタ12は、その振幅特性を
図2(A)に示し、その位相特性を図2(B)に示すよ
うに、尖鋭度Qが十分に高い、特性周波数がFoのフィ
ルタとされる。As shown in FIG. 2 (A) for its amplitude characteristic and for its phase characteristic in FIG. 2 (B), the bandpass filter 12 is a filter having a sharpness Q of sufficiently high and a characteristic frequency of Fo. To be done.
【0028】利得制御回路14の出力信号である、レベ
ル制御された基準周波数信号Sgは、帯域通過フィルタ
12を通過することにより、図2の特性に従って、その
基準周波数frと帯域通過フィルタ12の特性周波数F
oとの差Δfに応じた位相回転を受ける。The level-controlled reference frequency signal Sg, which is the output signal of the gain control circuit 14, passes through the band-pass filter 12 to obtain the reference frequency fr and the characteristic of the band-pass filter 12 according to the characteristic of FIG. Frequency F
It undergoes phase rotation according to the difference Δf from o.
【0029】そして、帯域通過フィルタ12は、この位
相回転量がゼロとなるように、位相比較回路13の出力
信号Scによって、その特性周波数Foが変えられる。
したがって、帯域通過フィルタ12の特性周波数Fo
は、基準周波数frに連動することになる。The characteristic frequency Fo of the bandpass filter 12 is changed by the output signal Sc of the phase comparison circuit 13 so that the phase rotation amount becomes zero.
Therefore, the characteristic frequency Fo of the bandpass filter 12
Will be linked to the reference frequency fr.
【0030】この場合、帯域通過フィルタ12の特性周
波数Foと、能動フィルタ1の特性周波数Faとの間
に、互いに強い相関を与えるように、それぞれの回路を
構成することで、上記のように位相比較回路13の出力
信号Scにより帯域通過フィルタ12の特性周波数Fo
が制御され、かつその位相比較回路13の出力信号Sc
により能動フィルタ1の特性周波数Faが調整されるこ
とによって、能動フィルタ1の特性周波数Faも基準周
波数frに連動することになり、能動フィルタ1の特性
周波数Faを調整することができる。In this case, by configuring the respective circuits such that the characteristic frequency Fo of the bandpass filter 12 and the characteristic frequency Fa of the active filter 1 are strongly correlated with each other, the phase is changed as described above. The characteristic frequency Fo of the band pass filter 12 is determined by the output signal Sc of the comparison circuit 13.
Is controlled and the output signal Sc of the phase comparison circuit 13 is controlled.
By adjusting the characteristic frequency Fa of the active filter 1 by the above, the characteristic frequency Fa of the active filter 1 also interlocks with the reference frequency fr, and the characteristic frequency Fa of the active filter 1 can be adjusted.
【0031】そして、レベル検出回路15の出力信号S
dによって、帯域通過フィルタ12の出力信号Sbのレ
ベルが一定となるように、利得制御回路14が制御され
るので、上記のように帯域通過フィルタ12の尖鋭度Q
を十分に高くしても、その尖鋭度Qのばらつきや帯域通
過フィルタ12の振幅特性による、帯域通過フィルタ1
2の出力信号Sbの振幅のばらつきや変動が抑止され
る。Then, the output signal S of the level detection circuit 15
Since the gain control circuit 14 is controlled by d so that the level of the output signal Sb of the bandpass filter 12 becomes constant, the sharpness Q of the bandpass filter 12 is as described above.
Is sufficiently high, the bandpass filter 1 may be affected by variations in the sharpness Q and the amplitude characteristics of the bandpass filter 12.
Variation or fluctuation of the amplitude of the second output signal Sb is suppressed.
【0032】したがって、位相比較回路13に供給され
る信号SrおよびSbの振幅が常に一定となり、位相比
較回路13は常に正しく動作する。そのため、帯域通過
フィルタ12の尖鋭度Qを十分に高くすることによっ
て、能動フィルタ1の特性周波数Faの調整精度を十分
に確保することができる。Therefore, the amplitudes of the signals Sr and Sb supplied to the phase comparison circuit 13 are always constant, and the phase comparison circuit 13 always operates correctly. Therefore, by sufficiently increasing the sharpness Q of the bandpass filter 12, the adjustment accuracy of the characteristic frequency Fa of the active filter 1 can be sufficiently ensured.
【0033】[0033]
【発明の効果】上述したように、この発明によれば、帯
域通過フィルタの尖鋭度Qを高くした場合においても、
位相比較回路が常に正しく動作する。したがって、帯域
通過フィルタの尖鋭度Qを高くすることによって、帯域
通過フィルタの特性周波数の近傍における周波数の変化
に対する位相の変化の割合を大きくすることができ、能
動フィルタの特性周波数の調整精度を十分に確保するこ
とができる。As described above, according to the present invention, even when the sharpness Q of the bandpass filter is increased,
The phase comparator circuit always works correctly. Therefore, by increasing the sharpness Q of the bandpass filter, it is possible to increase the rate of change in the phase with respect to the change in the frequency in the vicinity of the characteristic frequency of the bandpass filter, and to sufficiently adjust the characteristic frequency of the active filter. Can be secured.
【図1】この発明の特性周波数調整装置の一実施形態を
示すブロック図である。FIG. 1 is a block diagram showing an embodiment of a characteristic frequency adjusting device of the present invention.
【図2】図1の装置に用いる帯域通過フィルタの特性の
一例を示す図である。FIG. 2 is a diagram showing an example of characteristics of a bandpass filter used in the apparatus of FIG.
【図3】従来の特性周波数調整装置を示すブロック図で
ある。FIG. 3 is a block diagram showing a conventional characteristic frequency adjusting device.
【図4】図3の装置に用いる帯域通過フィルタの特性の
一例を示す図である。FIG. 4 is a diagram showing an example of characteristics of a bandpass filter used in the apparatus of FIG.
1 能動フィルタ 1c 制御端子 10 特性周波数調整装置 11 基準周波数信号発生器 12 帯域通過フィルタ 12i 入力端子 12c 制御端子 13 位相比較回路 14 利得制御回路 15 レベル検出回路 1 Active Filter 1c Control Terminal 10 Characteristic Frequency Adjustment Device 11 Reference Frequency Signal Generator 12 Band Pass Filter 12i Input Terminal 12c Control Terminal 13 Phase Comparison Circuit 14 Gain Control Circuit 15 Level Detection Circuit
Claims (1)
し、その入力端子に上記基準周波数信号発生器からの基
準周波数信号が供給される帯域通過フィルタと、 上記基準周波数信号発生器からの基準周波数信号と上記
帯域通過フィルタの出力信号の位相を比較し、その比較
結果出力を上記帯域通過フィルタの制御端子に供給し
て、上記帯域通過フィルタの特性周波数を制御する位相
比較回路と、 上記基準周波数信号発生器と上記帯域通過フィルタの入
力端子との間に挿入接続された利得制御回路と、 上記帯域通過フィルタの出力信号レベルを検出し、その
検出結果出力によって、上記帯域通過フィルタの出力信
号レベルが一定となるように、上記利得制御回路を制御
するレベル検出回路と、を備え、 上記位相比較回路の出力信号が、特性周波数が調整され
るべき能動フィルタの、特性周波数を変化させる制御端
子に供給される、 能動フィルタの特性周波数調整装置。1. A band pass filter having a reference frequency signal generator, an input terminal, and a control terminal for changing a characteristic frequency, and the reference frequency signal from the reference frequency signal generator is supplied to the input terminal. , Comparing the phase of the reference frequency signal from the reference frequency signal generator and the output signal of the band pass filter, and supplying the comparison result output to the control terminal of the band pass filter, the characteristic frequency of the band pass filter , A gain control circuit inserted between the reference frequency signal generator and the input terminal of the band pass filter, and detecting the output signal level of the band pass filter, the detection result A level detection circuit that controls the gain control circuit so that the output signal level of the bandpass filter becomes constant depending on the output, and A characteristic frequency adjusting device for an active filter, wherein an output signal of the phase comparison circuit is supplied to a control terminal for changing the characteristic frequency of an active filter whose characteristic frequency is to be adjusted.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP31004695A JP3393522B2 (en) | 1995-11-02 | 1995-11-02 | Active filter characteristic frequency adjustment device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP31004695A JP3393522B2 (en) | 1995-11-02 | 1995-11-02 | Active filter characteristic frequency adjustment device |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH09130206A true JPH09130206A (en) | 1997-05-16 |
JP3393522B2 JP3393522B2 (en) | 2003-04-07 |
Family
ID=18000520
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP31004695A Expired - Fee Related JP3393522B2 (en) | 1995-11-02 | 1995-11-02 | Active filter characteristic frequency adjustment device |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP3393522B2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100662584B1 (en) * | 1998-08-06 | 2007-01-02 | 후지쯔 가부시끼가이샤 | Filter characteristic regulating apparatus and regulating method therefor |
JP2011215128A (en) * | 2010-03-16 | 2011-10-27 | Denso Corp | Glonass receiving device |
-
1995
- 1995-11-02 JP JP31004695A patent/JP3393522B2/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100662584B1 (en) * | 1998-08-06 | 2007-01-02 | 후지쯔 가부시끼가이샤 | Filter characteristic regulating apparatus and regulating method therefor |
JP2011215128A (en) * | 2010-03-16 | 2011-10-27 | Denso Corp | Glonass receiving device |
Also Published As
Publication number | Publication date |
---|---|
JP3393522B2 (en) | 2003-04-07 |
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