Compressor-expander circuits and, circuit arrangements for modifying dynamic range, for suppressing mid-frequency modulation effects and for reducing media overload
US4490691A · kind A · utility
Inventor
Key dates
| Filing date | Sep 10, 1981 |
| Grant date | Dec 25, 1984 |
| Priority date | — |
| Expiry date | Sep 10, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/18
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In a first aspect of the invention, compressor and expander circuits are arranged in series, the dynamic actions of the circuits being substantially separated with respect to level. The changing gain portions of the characteristics are staggered among the series circuits such that the resulting overall characteristic has a maximum compression or expansion ratio substantially no greater than that of any single circuit while providing more compression or expansion than for any of the circuits individually. A second aspect, referred to as "spectral skewing", effects a reduction of the influence of signals in the high and/or low frequency extremes of a signal transmission system on the action of a compressor feeding the transmission channel. Consequently, a complementary expander fed by the channel is less likely to be controlled by signals at frequencies subject to transmission channel errors. A third aspect provides an anti-saturation effect. This aspect of the invention takes advantage of the properties of dual path compressors and expanders, in which the output of the circuits at very low signal levels is provided mostly by the further path and at high levels, mostly by the main pa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.