JP3170796B2 - Active filter circuit - Google Patents
Active filter circuitInfo
- Publication number
- JP3170796B2 JP3170796B2 JP29009390A JP29009390A JP3170796B2 JP 3170796 B2 JP3170796 B2 JP 3170796B2 JP 29009390 A JP29009390 A JP 29009390A JP 29009390 A JP29009390 A JP 29009390A JP 3170796 B2 JP3170796 B2 JP 3170796B2
- Authority
- JP
- Japan
- Prior art keywords
- resistor
- operational amplifier
- input
- filter circuit
- active filter
- 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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Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は、反転型３次ローパスフィルタの特性と、振
幅イコライザの特性とを兼備したアクティブフィルタ回
路に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active filter circuit having both the characteristics of an inverted third-order low-pass filter and the characteristics of an amplitude equalizer.
（従来の技術） この種の従来例のアクティブフィルタ回路は、第２図
に示すように反転型３次ローパスフィルタ２と、振幅イ
コライザ４とで構成されており、それぞれはいずれも演
算増幅器6,8（ただし、振幅イコライザ４はバッファア
ンプとしての演算増幅器）を具備していた。(Prior Art) As shown in FIG. 2, this type of conventional active filter circuit includes an inverting third-order low-pass filter 2 and an amplitude equalizer 4, each of which has an operational amplifier 6, 8 (however, the amplitude equalizer 4 is an operational amplifier as a buffer amplifier).
（発明が解決しようとする課題） しかしながら、このように反転型３次ローパスフィル
タ２と振幅イコライザ４のそれぞれが演算増幅器6,8を
具備しているために、その演算増幅器6,8そのもののが
コスト的に高くつくのみならず、そこでの電力消費も大
きく、しかも構成も複雑化しているとともに、回路基板
などに組み込む場合に小型化には適していないなどの不
具合があった。(Problems to be Solved by the Invention) However, since each of the inverting tertiary low-pass filter 2 and the amplitude equalizer 4 includes the operational amplifiers 6 and 8, the operational amplifiers 6 and 8 themselves are not used. Not only is it costly, it consumes a large amount of power, and its configuration is complicated, and it is not suitable for miniaturization when incorporated in a circuit board or the like.
そこで、本発明の１つの演算増幅器を用いたもので反
転型３次ローパスフィルタと振幅イコライザそれぞれの
特性を備えさせることで、コスト的に安く電力消費も少
なくて済み、しかも簡単かつ小型化可能な構成を有する
アクティブフィルタ回路を提供することを目的としてい
る。Therefore, by using the single operational amplifier of the present invention and providing the characteristics of the inverting third-order low-pass filter and the amplitude equalizer, the cost can be reduced, the power consumption can be reduced, and the size can be simplified and reduced. It is an object to provide an active filter circuit having a configuration.
（実施例） 以下、本発明の実施例を図面を参照して詳細に説明す
る。第１図は本発明の実施例に係るアクティブフィルタ
回路の回路図である。(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of an active filter circuit according to an embodiment of the present invention.
まず、当該アクティブフィルタ回路の入力端INへの入
力電圧をVi、その出力端OUTからの出力電圧をVoとした
ときの合成伝達関数Vo/Vi＝Ｔ（Ｓ）は、次式（１）で
あらわされる。First, when the input voltage to the input terminal IN of the active filter circuit is Vi and the output voltage from the output terminal OUT is Vo, the combined transfer function Vo / Vi = T (S) is given by the following equation (1). Will be revealed.
ただし、 Ｅ＝Ｈ・ω１・ω2 2 Ｆ＝Ｈ・ａ・ω１・ω2 2 X1＝ω１＋ｂ＋ω2/Q、 X2＝ω2 2＋ω１・ｂ＋（ω１＋ｂ）（ω2/Q） X3＝ω１・ω２＋ω２・ｂ＋ｂ・ω１・ω2/Q X4＝ω１・ω２・ｂ また、Ｈはフィルタの利得、ａ、ｂは、振幅イコライ
ザの振幅特性を決定するパラメータ、Ｓはｊωであらわ
される角周波数、Ｑは２次ローパスフィルタの尖鋭度、
ω１は１次ローパスフィルタのカットオフ角周波数、ω
２は２次ローパスフィルタのカットオフ角周波数、でそ
れぞれあらわされる。 However, E = H · ω 1 · ω 2 2 F = H · a · ω 1 · ω 2 2 X 1 = ω 1 + b + ω 2 / Q, X 2 = ω 2 2 + ω 1 · b + (ω 1 + b) ( ω 2 / Q) X 3 = ω 1 · ω 2 + ω 2 · b + b · ω 1 · ω 2 / QX 4 = ω 1 · ω 2 · b H is the gain of the filter, and a and b are the amplitude equalizers. S is the angular frequency represented by jω, Q is the sharpness of the secondary low-pass filter,
ω 1 is the cutoff angular frequency of the first-order low-pass filter, ω
Reference numeral 2 denotes a cutoff angular frequency of the secondary low-pass filter.
つぎに、本実施例のアクティブフィルタ回路は、２入
力型の演算増幅器OAを有し、入力端INから演算増幅器OA
の一方の入力部（−）までの間に第１、第２、および第
４の抵抗R1,R2,R4をこの順序で直列接続し、第１抵抗R1
および第２抵抗R2の第１接続部ＡとアースＥとの間に第
１コンデンサC1を接続し、第２抵抗R2および第３抵抗R3
の第２接続部ＢとアースＥとの間に第２コンデンサC2を
接続し、演算増幅器OAの出力部と第１接続部Ａとの間に
第５抵抗R5と第４コンデンサC4とを直列に接続し、演算
増幅器OAの出力部と第２接続部Ｂとの間に第３抵抗R3を
接続し、演算増幅器OAの出力部と一方の入力部（−）と
の間に第３コンデンサC3を接続し、演算増幅器OAの出力
部とアースＥとの間に第６抵抗R6と第７抵抗R7とを直列
に接続し、第６抵抗R6と第７抵抗R7との第３接続部Ｄを
演算増幅器OAの他方の入力部（＋）に接続してなり、か
つ第１ないし第４コンデンサC1〜C4の容量をそれぞれc1
〜c4とし、前記第１抵抗ないし第７抵抗R1〜R7のコンダ
クタンスをそれぞれg1〜g7とおいた場合、当該アクティ
ブフィルタ回路の伝達関数Ｔ（ｓ）は次式（２）であら
わさる。Next, the active filter circuit of the present embodiment has a two-input type operational amplifier OA, and the operational amplifier OA
The first, second, and fourth resistors R1, R2, and R4 are connected in series in this order until one input section (-) of the first resistor R1
A first capacitor C1 is connected between the first connection A of the second resistor R2 and the ground E, and a second resistor R2 and a third resistor R3 are connected.
A second capacitor C2 is connected between the second connection portion B and the ground E, and a fifth resistor R5 and a fourth capacitor C4 are connected in series between the output portion of the operational amplifier OA and the first connection portion A. And a third resistor R3 is connected between the output of the operational amplifier OA and the second connection B, and a third capacitor C3 is connected between the output of the operational amplifier OA and one input (-). The sixth resistor R6 and the seventh resistor R7 are connected in series between the output of the operational amplifier OA and the ground E, and the third connection D between the sixth resistor R6 and the seventh resistor R7 is operated. It is connected to the other input section (+) of the amplifier OA, and each of the capacitances of the first to fourth capacitors C1 to C4 is c 1
And to c 4, the first case of resistance or the conductance of the seventh resistor R1~R7 placed and g 1 to g 7 respectively, the transfer function of the active filter circuit T (s) is Arawasaru by the following formula (2).
ただし、 Ａ＝［g1・c2・c3・c4＋g2・（c1＋c2）・c3・c4＋g3・
c1・c3・c4 ＋g4・c1・c3・c4＋g5・（c1＋ c4）・c2・c3−α・g4・c1・c2・c4］/P Ｂ＝［g1・（g2＋g3＋g4）・c3・c4＋g1・g5・c2・c3＋ g2・（g3＋g4＋g5）・c3・c4＋g2・g5・（c1＋c2） ・c3＋g3・g4・c1・c4＋（g3＋g4）・g5（c1＋c4） ・c3−α・｛g1・g4・c2・c4＋g2・g4・（c1＋c2） ・c4＋g4・g5・（c1＋c4）・c2｝］/P Ｃ＝［g1・g5・（g2＋g3＋g4）・c3＋g1・g3・g4・ c4＋g2・g3・g4・c4＋g2・g3・g5・c3＋g2・g4・g5 ・（c3＋c4）＋g3・g4・g5・（c1＋c4）−α・｛g1・ g2・g4・c4＋g1・g4・g5・c2＋g2・g4・g5 ・（c1＋c2）｝］/P Ｄ＝［（g1＋g2）・g3・g4・g5−α・g1・g2・g4・g5］
/P Ｅ＝c4・g1・g2・g4/P・（１−β） Ｆ＝g1・g2・g4・g5/P・（１−β） α＝g7/g6 β＝α／（１＋α）＝g7/（g6＋g7） Ｐ＝c1・c2・c3・c4 そして、本実施例のアクティブフィルタ回路は、前記
両式（１）（２）の分母におけるＳの係数が一致し、か
つ分子のＳの各係数の比が等しくなるように前記容量お
よびコンダクタンスを選定していることを特徴とするも
のである。 Where A = [g 1 · c 2 · c 3 · c 4 + g 2 · (c 1 + c 2 ) · c 3 · c 4 + g 3 ·
c 1 · c 3 · c 4 + g 4 · c 1 · c 3 · c 4 + g 5 · (c 1 + c 4 ) · c 2 · c 3- α · g 4 · c 1 · c 2 · c 4 ] / P B = [g 1 · (g 2 + g 3 + g 4) · c 3 · c 4 + g 1 · g 5 · c 2 · c 3 + g 2 · (g 3 + g 4 + g 5) · c 3 · c 4 + g 2 · g 5 · (c 1 + c 2) · c 3 + g 3 · g 4 · c 1 · c 4 + (g 3 + g 4) · g 5 (c 1 + c 4) · c 3 -α · { g 1 · g 4 · c 2 · c 4 + g 2 · g 4 · (c 1 + c 2 ) · c 4 + g 4 · g 5 · (c 1 + c 4 ) · c 2 ｝] / PC = [g 1 · g 5 · (g 2 + g 3 + g 4) · c 3 + g 1 · g 3 · g 4 · c 4 + g 2 · g 3 · g 4 · c 4 + g 2 · g 3 · g 5 · c 3 + g 2 · g 4 · g 5 · ( c 3 + c 4) + g 3 · g 4 · g 5 · (c 1 + c 4) -α · {g 1 · g 2 · g 4 · c 4 + g 1 · g 4 · g 5 · c 2 + g 2 · g 4 · g 5 · (c 1 + c 2 )｝] / P D = [(g 1 + g 2 ) · g 3 · g 4 · g 5 −α · g 1 · g 2 · g 4 · g 5]
/ P E = c 4 · g 1 · g 2 · g 4 / P · (1-β) F = g 1 · g 2 · g 4 · g 5 / P · (1-β) α = g 7 / g 6 β = α / (1 + α) = g 7 / (g 6 + g 7 ) P = c 1 cc 2 cc 3そ し て c 4 The active filter circuit of the present embodiment employs both of the above equations (1) and (2). ), The capacitance and conductance are selected such that the coefficients of S in the denominator match and the ratio of each coefficient of S in the numerator is equal.
したがって、前記（１）（２）式の分母におけるＳの
係数がそれぞれ等しく、かつ分子のＳの各係数の比が等
しくなるように各コンデンサの容量と抵抗のコンダクタ
ンスとを選定することにより、実施例のアクティブフィ
ルタ回路は、１個の演算増幅器でもって前記所望の合成
特性を得ることができることになる。Therefore, the capacitance and resistance conductance of each capacitor are selected so that the coefficients of S in the denominator of the above equations (1) and (2) are equal and the ratio of each coefficient of S in the numerator is equal. In the active filter circuit of the example, the desired combined characteristics can be obtained with one operational amplifier.
なお、この実施例では前記第６抵抗R6と第７抵抗R7と
を共に省略して演算増幅器の出力部と他方の入力部
（＋）とをオープンにするとともに、当該他方の入力部
（＋）をアースしてもよい。In this embodiment, both the sixth resistor R6 and the seventh resistor R7 are omitted, the output of the operational amplifier and the other input (+) are opened, and the other input (+) is opened. May be grounded.
また、この実施例では上記（１）（２）の分子におけ
るＳの係数も等しくなるようにしている。もっとも、こ
の分子間の関係は所望の合成特性をその形を変えずに上
下に平行移動させる、すなわち利得を全体的に変えるの
に関係するだけであるため、必ずしもこの例のように両
係数を一致させなくてもよい。In this embodiment, the coefficients of S in the numerators (1) and (2) are also made equal. However, since this relationship between the molecules only translates the desired synthetic property up and down without changing its shape, that is, it changes the gain as a whole, it is not always necessary to use both coefficients as in this example. They do not have to match.
（効果） 以上説明したことから明らかなように本発明によれ
ば、１個の演算増幅器でもって反転型３次ローパスフィ
ルタの特性と振幅イコライザの特性との両特性が得られ
ることから、コスト的に安く電力消費も少なくて済み、
しかも簡単かつ小型化可能な構成を有するアクティブフ
ィルタ回路を提供することができる。(Effects) As is apparent from the above description, according to the present invention, both the characteristics of the inverting third-order low-pass filter and the characteristics of the amplitude equalizer can be obtained with one operational amplifier. Low cost and low power consumption,
Moreover, it is possible to provide an active filter circuit having a simple and miniaturizable configuration.
第１図は本発明の一実施例に係るアクティブフィルタ回
路の回路図、第２図はは従来例のアクティブフィルタ回
路の回路図である。 OA……演算増幅器、IN……入力端、C1ないしC4……コン
デンサ、R1ないしR7……抵抗。FIG. 1 is a circuit diagram of an active filter circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional active filter circuit. OA: Operational amplifier, IN: Input terminal, C1 to C4: Capacitor, R1 to R7: Resistance.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭57−89336（ＪＰ，Ａ) 特開 平２−183612（ＪＰ，Ａ) 実開 昭47−17530（ＪＰ，Ｕ) 実開 昭57−48727（ＪＰ，Ｕ) 実開 昭64−40921（ＪＰ，Ｕ) 実開 昭64−38828（ＪＰ，Ｕ) 実開 昭62−161424（ＪＰ，Ｕ) (58)調査した分野(Int.Cl.7，ＤＢ名) H03H 11/04 H03H 11/12 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-89336 (JP, A) JP-A-2-183612 (JP, A) Actually open 47-1730 (JP, U) Actually open Showa 57- 48727 (JP, U) Japanese Utility Model Showa 64-40921 (JP, U) Japanese Utility Model Showa 64-38828 (JP, U) Japanese Utility Model Showa 62-161424 (JP, U) (58) Field surveyed (Int. 7 , DB name) H03H 11/04 H03H 11/12
Claims (2)
伝達関数Vo/Vi〔＝Ｔ（Ｓ）〕が、 ただし、 Ｅ＝Ｈ・ω１・ω2 2 Ｆ＝Ｈ・ａ・ω１・ω2 2 X1＝ω１＋ｂ＋ω2/Q、 X2＝ω2 2・ω１＋ｂ＋（ω1/b）（ω2/Q） X3＝ω１・ω２＋ω２・ｂ＋ｂ・ω１・ω2/Q X4＝ω１・ω２・ｂ また、Ｈはフィルタの利得、ａ、ｂは、振幅イコライザ
の振幅特性を決定するパラメータ、Ｓはｊωであらわさ
れる角周波数、Ｑは２次ローパスフィルタの尖鋭度、ω
１は１次ローパスフィルタのカットオフ角周波数、ω２
は２次ローパスフィルタのカットオフ角周波数、でそれ
ぞれあらわされる特性を実現するアクティブフィルタ回
路であって、２入力型の演算増幅器を有し、入力端から
演算増幅器の一方の入力部までの間に第１、第２、およ
び第４の抵抗をこの順序で直列接続し、第１抵抗および
第２抵抗の第１接続部とアースとの間に第１コンデンサ
を接続し、第２抵抗および第３抵抗の第２接続部とアー
スとの間に第２コンデンサを接続し、演算増幅器の出力
部と第１接続部との間に第５抵抗と第４コンデンサとを
直列に接続し、演算増幅器の出力部と第２接続部との間
に第３抵抗を接続し、演算増幅器の出力部と一方の入力
部との間に第３コンデンサを接続し、演算増幅器の出力
部とアースとの間に第６抵抗と第７抵抗とを直列に接続
し、第６抵抗と第７抵抗との第３接続部を演算増幅器の
他方の入力部に接続してなり、 前記第１ないし第４コンデンサの容量をそれぞれC1〜C4
とし、前記第１抵抗ないし第７抵抗のコンダクタンスを
それぞれg1〜g7とおいた場合、当該アクティブフィルタ
回路の伝達関数Ｔ（ｓ）は次式であらわされ、 ただし、 Ａ＝［g1・c2・c3・c4＋g2・（c1＋c2）・c3・c4＋g3・
c1・c3・c4 ＋g4・c1・c3・c4＋g5・（c1＋ c4）・c2・c3−α・g4・c1・c2・c4］/P Ｂ＝［g1・（g2＋g3＋g4）・c3・c4＋g1・g5・c2・c3＋ g2・（g3＋g4＋g5）・c3・c4＋g2・g5・（c1＋c2） ・c3＋g3・g4・c1・c4＋（g3＋g4）・g5（c1＋c4） ・c3−α・｛g1・g4・c2・c4＋g2・g4・（c1＋c2） ・c4＋g4・g5・（c1＋c4）・c2｝］/P Ｃ＝［g1・g5・（g2＋g3＋g4）・c3＋g1・g3・g4・ c4＋g2・g3・g4・c4＋g2・g3・g5・c3＋g2・g4・g5 ・（c3＋c4）＋g3・g4・g5・（c1＋c4）−α・｛g1・ g2・g4・c4＋g1・g4・g5・c2＋g2・g4・g5 ・（c1＋c2）｝］/P Ｄ＝［（g1＋g2）・g3・g4・g5−α・g1・g2・g4・g5］
/P Ｅ＝c4・g1・g2・g4/P・（１−β） Ｆ＝g1・g2・g4・g5/P・（１−β） α＝g7/g6 β＝α／（１＋α）＝g7/（g6＋g7） Ｐ＝c1・c2・c3・c4 そして、前記両式（１）（２）の分母におけるＳの係数
が一致し、かつ分子の各係数の比が等しくなるように前
記容量およびコンダクタンスを選定していることを特徴
とするアクティブフィルタ回路。When the input voltage is Vi and the output voltage is Vo,
The transfer function Vo / Vi [= T (S)] However, E = H · ω 1 · ω 2 2 F = H · a · ω 1 · ω 2 2 X 1 = ω 1 + b + ω 2 / Q, X 2 = ω 2 2 · ω 1 + b + (ω 1 / b) (Ω 2 / Q) X 3 = ω 1 · ω 2 + ω 2 · b + b · ω 1 · ω 2 / QX 4 = ω 1 · ω 2 · b Further, H is the gain of the filter, and a and b are the amplitude equalizers. , S is the angular frequency represented by jω, Q is the sharpness of the secondary low-pass filter, ω
1 is the cutoff angular frequency of the first-order low-pass filter, ω 2
Is an active filter circuit that realizes characteristics represented by a cutoff angular frequency of a secondary low-pass filter, and has a two-input type operational amplifier, and is provided between an input terminal and one input portion of the operational amplifier. A first, a second, and a fourth resistor are connected in series in this order, a first capacitor is connected between a first connection of the first and second resistors and ground, and a second resistor and a third resistor are connected. A second capacitor is connected between the second connection of the resistor and ground, a fifth resistor and a fourth capacitor are connected in series between the output of the operational amplifier and the first connection, A third resistor is connected between the output section and the second connection section, a third capacitor is connected between the output section of the operational amplifier and one of the input sections, and between the output section of the operational amplifier and ground. The sixth resistor and the seventh resistor are connected in series, and the sixth resistor and the seventh resistor are connected in series. A third connection portion between the resistor will be connected to the other input of the operational amplifier, respectively the capacity of the first through fourth capacitors C 1 -C 4
When the conductances of the first to seventh resistors are g 1 to g 7 , respectively, the transfer function T (s) of the active filter circuit is represented by the following equation: Where A = [g 1 · c 2 · c 3 · c 4 + g 2 · (c 1 + c 2 ) · c 3 · c 4 + g 3 ·
c 1 · c 3 · c 4 + g 4 · c 1 · c 3 · c 4 + g 5 · (c 1 + c 4 ) · c 2 · c 3- α · g 4 · c 1 · c 2 · c 4 ] / P B = [g 1 · (g 2 + g 3 + g 4) · c 3 · c 4 + g 1 · g 5 · c 2 · c 3 + g 2 · (g 3 + g 4 + g 5) · c 3 · c 4 + g 2 · g 5 · (c 1 + c 2) · c 3 + g 3 · g 4 · c 1 · c 4 + (g 3 + g 4) · g 5 (c 1 + c 4) · c 3 -α · { g 1 · g 4 · c 2 · c 4 + g 2 · g 4 · (c 1 + c 2 ) · c 4 + g 4 · g 5 · (c 1 + c 4 ) · c 2 ｝] / PC = [g 1 · g 5 · (g 2 + g 3 + g 4) · c 3 + g 1 · g 3 · g 4 · c 4 + g 2 · g 3 · g 4 · c 4 + g 2 · g 3 · g 5 · c 3 + g 2 · g 4 · g 5 · ( c 3 + c 4) + g 3 · g 4 · g 5 · (c 1 + c 4) -α · {g 1 · g 2 · g 4 · c 4 + g 1 · g 4 · g 5 · c 2 + g 2 · g 4 · g 5 · (c 1 + c 2 )｝] / P D = [(g 1 + g 2 ) · g 3 · g 4 · g 5 −α · g 1 · g 2 · g 4 · g 5]
/ P E = c 4 · g 1 · g 2 · g 4 / P · (1-β) F = g 1 · g 2 · g 4 · g 5 / P · (1-β) α = g 7 / g 6 β = α / (1 + α) = g 7 / (g 6 + g 7 ) P = c 1 · c 2 · c 3 · c 4 And the coefficient of S in the denominator of both formulas (1) and (2) is one. An active filter circuit, wherein the capacitance and the conductance are selected such that the ratio of each coefficient of the numerator is equal.
演算増幅器の出力部と他方の入力部とをオープンにする
とともに、当該他方の入力部をアースしたことを特徴と
する請求項（１）に記載のアクティブフィルタ回路。2. An apparatus according to claim 1, wherein said sixth resistor and said seventh resistor are both omitted to open the output section of said operational amplifier and the other input section and to ground said other input section. The active filter circuit according to item (1).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29009390A JP3170796B2 (en) | 1990-10-26 | 1990-10-26 | Active filter circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29009390A JP3170796B2 (en) | 1990-10-26 | 1990-10-26 | Active filter circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04167609A JPH04167609A (en) | 1992-06-15 |
| JP3170796B2 true JP3170796B2 (en) | 2001-05-28 |
Family
ID=17751709
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29009390A Expired - Fee Related JP3170796B2 (en) | 1990-10-26 | 1990-10-26 | Active filter circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3170796B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008252213A (en) * | 2007-03-29 | 2008-10-16 | Pioneer Electronic Corp | Multi-feedback low-pass filter |
| US9877107B2 (en) * | 2015-10-20 | 2018-01-23 | Marvell World Trade Ltd. | Processing audio signals |
-
1990
- 1990-10-26 JP JP29009390A patent/JP3170796B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04167609A (en) | 1992-06-15 |
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