System for the reconstruction by filtering of an analogue signal from a pseudoanalogue signal obtained by double analogue/digital, digital/analogue conversion of said analogue signals with a possible processing of the digital signal

摘要

Method for the reconstitution, by filtering, of an analog signal, from a pseudo-analog signal obtained by a double, analog to digital, digital to analog conversions of the analog signal, with processing of the digital signal. In greater detail, the pseudo-analog signal, obtained by double analog to digital, digital to analog conversion of an analog signal, is applied to an active filter the impedance of which is controlled by the absolute derivative of the positive value of the pseudo-analog signal. The derivative is obtained by a circuit comprising an RC filter receiving the pseudo-analog signal and a memory controlling the value of the impedance of the filter. The invention has particular application to the restitution of graphic or iconographic documents which have been previously digitally encoded.