Wave transmission lines and networks – Amplitude compression and expansion systems
Patent
1977-10-21
1980-02-05
Gensler, Paul L.
Wave transmission lines and networks
Amplitude compression and expansion systems
307264, 328168, 330126, 330295, 325 62, H04B 164
Patent
active
041874773
ABSTRACT:
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.
REFERENCES:
patent: 3757254 (1973-09-01), Takahashi et al.
patent: 3795876 (1974-03-01), Takahashi et al.
patent: 3989897 (1976-11-01), Carver
Endoh Kenjiro
Kira Hideshi
Kitagawa Kazuo
Ohkawa Motokazu
Gensler Paul L.
Tokyo Shibaura Electric Co. Ltd.
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