Disturbance Observer Design with a Bode's Ideal Filter for Sigma-Delta Modulators

Abstract

It is usually difficult to design a high performance Sigma-Delta (ΣΔ) modulator due to system noises. In this paper, a disturbance observer (DOB) is utilized to estimate the system noises and eliminate their effects on ΣΔ modulators. The applied DOB is introduced with a Bode's ideal cut-off (BICO) filter used for the Q-filter. The proposed DOB with the BICO filter used in ΣΔ modulators can achieve better noise-shaping ability, resulting from the less phase loss of the BICO filter. Finally, the simulation results show that the proposed BICO filter scheme is a useful additional tool for improving the performance of ΣΔ modulators.