Anordning och förfarande för reducering av periodiskt brus i en sigma-delta modulator

摘要

The present invention relates to an apparatus and a method for sigma-delta modulation with a reduced periodic noise (idle noise) in a sigma-delta modulator. The reduction is achieved by means of addition of two different Dither signals (217,218) to the sigma-delta modulator. A first Dither signal (218) is constituted by a particular bit pattern of a certain period while a second Dither signal (217) is constituted by a pseudo-random signal of a certain other period.