Introduction of a whitener signal in a sigma delta modulator in the

Abstract

A method of injecting a whitening random signal in a Sigma Delta modulator with a high-pass transfer function of a quantization noise filter of a certain order, for converting a digital audio signal sampled at a certain clock frequency into an analog signal, comprises the steps of generating a flat-spectrum dither signal, filtering the dither signal with a high-pass transfer function of an order higher than the order of the transfer function of the Sigma Delta modulator, and summing the filtered signal to the sampled digital audio signal, quantized by the modulator. The method prevents the occurrence of disturbances that would otherwise occur as a result of intermodulation of subtle colorations observable in the vicinity of the Nyquist frequency. The disclosed hardware implementation of the method adds little to the hardware complexity.