公开(公告)号：US4224581A

公开(公告)日：1980-09-23

申请号：US844198

申请日：1977-10-21

申请人： Hiroshi Watanabe ,  Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

发明人： Hiroshi Watanabe ,  Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

IPC分类号： H03G9/02 ,  H04B1/64 ,  H03G7/00

CPC分类号： H03G9/025

摘要： A noise reduction system having an encoder which compresses the dynamic range of an analog audio signal, a transmission medium coupled to the encoder, and a decoder coupled to the transmission medium for expanding and thereby restoring the dynamic range of the compressed analog audio signal. The encoder includes a voltage controlled amplifier (VCA) receiving the audio signal, a high-pass filter also coupled to the analog audio signal, a circuit for obtaining a difference between the outputs of the VCA and the high-pass filter, weighting and level sensing circuits coupled to the encoder output for sensing the level of the compressed analog audio signal, and a limiter circuit coupled to the output of the weighting and level sensing circuits and producing a control voltage applied to the VCA control input in such a manner that the ratio of the gain of the VCA and the gain of the high-pass filter at the pass band thereof does not become less than one. The decoder includes circuits similar to those of the encoder and exhibits a transfer function substantially inverse to the encoder transfer function, with the controlling voltage applied to the decoder VCA such that the loop gain in the pass band of the high-pass filter does not become more than one.

摘要翻译： 一种噪声降低系统，具有压缩模拟音频信号的动态范围的编码器，耦合到编码器的传输介质和耦合到传输介质的解码器，用于扩展并由此恢复压缩的模拟音频信号的动态范围。 编码器包括接收音频信号的压控放大器（VCA），还耦合到模拟音频信号的高通滤波器，用于获得VCA和高通滤波器的输出之间的差值的电路，加权和电平 耦合到编码器输出的感测电路用于感测压缩的模拟音频信号的电平;以及限制器电路，耦合到加权和电平感测电路的输出，并产生施加到VCA控制输入的控制电压， VCA的增益比和通带的高通滤波器的增益的比率不会变得小于1。 解码器包括与编码器类似的电路，并且具有与编码器传递函数基本相反的传递函数，其中控制电压施加到解码器VCA，使得高通滤波器的通带中的环路增益不会变为 超过一个。

公开(公告)号：US3950711A

公开(公告)日：1976-04-13

申请号：US531612

申请日：1974-12-11

申请人： Motokazu Ohkawa

发明人： Motokazu Ohkawa

IPC分类号： H03G5/22 ,  H03F1/36

CPC分类号： H03G5/22

摘要： A frequency characteristics-controlling device which comprises an operational amplifier provided with two input terminals mutually bearing an inversion-noninversion relationship with respect to an output signal; a bridged-T circuit consisting of resistors and capacitors, the input terminal of said bridged-T circuit being connected to the inversion input terminal of said amplifier and the output terminal of said bridged-T circuit being connected to the output terminal of said amplifier; a first gain-controlling circuit connected between the common terminal of the bridged-T circuit and the noninversion input terminal of the amplifier; and a second gain-controlling circuit connected between the common terminal of the bridged-T circuit and the output terminal of the amplifier, whereby the frequency characteristics of an input signal supplied to the noninversion input terminal of the operational amplifier are controlled by the first and second gain-controlling circuits.

公开(公告)号：US4187477A

公开(公告)日：1980-02-05

申请号：US844435

申请日：1977-10-21

申请人： Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

发明人： Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

IPC分类号： H04B1/62 ,  G11B20/04 ,  H03G7/00 ,  H03G9/02 ,  H04B1/64

CPC分类号： H03G9/025

摘要： A noise reduction system including an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude thereof, a transmission medium coupled to the encoder, and a decoder having a transfer function inverse to that of the decoder. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is in low- and middle- levels, sufficient emphasis is made to the signal at high frequencies, and when it is in high-level, the emphasis quantity at high frequencies is restrictive. The decoder includes a voltage-current converting circuit for converting voltage of the reproduced audio signal into current and a second controlled amplifier circuit amplifying the converted current and having a transfer function inverse to that of the first controlled amplifier circuit. The second controlled amplifier includes a variable response amplifier having a capacitor and a resistor in series circuit between the output of the voltage-current converting circuit and the output terminal of the second voltage controlled amplifier, a variable gain current amplifier connected at the input thereof to the output of the voltage-current converting circuit and the series circuit, and means for converting the output current of the variable gain current amplifier into a voltage to be directed to the decoder output terminal.

摘要翻译： 一种降噪系统，包括用于根据其幅度压缩音频输入信号的动态范围的编码器，耦合到编码器的传输介质和具有与解码器的传递函数相反的传递函数的解码器。 编码器包括第一受控放大器电路，其中当输入音频信号处于低电平和中等电平时，对高频信号充分强调，当处于高电平时，高电平处的强调量 频率是限制性的。 解码器包括用于将再现的音频信号的电压转换成电流的电压 - 电流转换电路和放大转换后的电流并具有与第一受控放大器电路相反的传递函数的第二受控放大器电路。 第二受控放大器包括具有电容器的可变响应放大器和在电压 - 电流转换电路的输出与第二压控放大器的输出端之间的串联电路中的电阻器，连接在其输入端的可变增益电流放大器 电压电流转换电路和串联电路的输出，以及用于将可变增益电流放大器的输出电流转换为指向解码器输出端子的电压的装置。

公开(公告)号：US4187478A

公开(公告)日：1980-02-05

申请号：US844436

申请日：1977-10-21

申请人： Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

发明人： Kenjiro Endoh ,  Motokazu Ohkawa ,  Kazuo Kitagawa ,  Hideshi Kira

IPC分类号： H04B1/62 ,  G11B20/04 ,  H03G7/00 ,  H03G9/02 ,  H04B1/64

CPC分类号： H03G9/025

摘要： A noise reduction system is provided with an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude of the input signal and recording the compressed one into a tape-recorder, and a decoder for expanding the dynamic range of a reproduced audio signal from the tape-recorder to the original one in accordance with the amplitude of the reproduced audio signal. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is low- and middle-levels, sufficient emphasis is made to the signal at high-frequencies, and when it is in high-level, the emphasis quantity at high-frequencies is restrictive. The decoder includes a second controlled amplifier circuit having a transfer function related to the character of the first controlled amplifier circuit substantially in inverse-function manner. The first controlled amplifier includes a variable response amplifier having a first resistor connected at one end to an input terminal, a current amplifier with variable gain amplifying current extracted from the other end of the first resistor, a series circuit having a second resistor and a capacitor and connected at one end to the input terminal, and means for adding an output current of the other end of the series circuit with an output current of the current amplifier and means for converting the summed current into voltage directed to an output terminal.

摘要翻译： 噪声降低系统具有：编码器，用于根据输入信号的幅度压缩音频输入信号的动态范围，并将压缩的信号记录到录音机中;解码器，用于扩展再现的动态范围 根据再现的音频信号的幅度从音频记录器到原始音频信号的音频信号。 编码器包括第一受控放大器电路，其中当输入音频信号为低电平和中等电平时，对高频信号进行充分的重视，并且当处于高电平时，高电平处的强调量 - 频率是限制性的。 解码器包括具有与第一受控放大器电路的特性相关的传递函数的第二受控放大器电路，其基本上是反向功能的。 第一受控放大器包括一个可变响应放大器，该可变响应放大器的一端连接到一个输入端;一个电流放大器，具有从第一个电阻的另一端提取的可变增益放大电流，串联电路具有一个第二电阻和一个电容 并且其一端连接到输入端子，以及用于将串联电路的另一端的输出电流与电流放大器的输出电流相加的装置和用于将求和的电流转换成指向输出端子的电压的装置。