Some remarks on the stability and performance of the noise shaper or sigma-delta modulator

The stability constraints of the noise shaper are examined for the purpose of coder design. The author shows that the presence of a limiter in the noise shaper strongly influences the stability criteria on the loop filter of a third- or higher-order coder. A third-order coder was designed according to these results for high-fidelity audio. It performs with a dynamic range of over 100 dB, and the measured in-band noise agrees fairly well with the calculated value. The proposed design procedure also applies to the (sigma-) delta modulator, which is in essence the same device. >