Compander system having limiter in compressor and expander
US4224581A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 21, 1977 |
| Grant date | Sep 23, 1980 |
| Priority date | — |
| Expiry date | Oct 21, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/025
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
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 …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.