Estimating Circuit Nonidealities of Continuous-Time Multibit Delta-Sigma Modulators

Circuit nonidealities such as real opamp behavior, coefficient mismatch, excess loop delay or jitter are known to drastically reduce the performance of continuous-time delta-sigma modulators. In this paper, the first step toward a successful correction and therewith compensation of these errors is presented: an online estimation of their real values based on an unscented Kalman filter. Contrary to the classical approach, which makes use of an extended Kalman filter, no linearization of the strongly nonlinear system equation has to be performed as a deterministic set of sampling points is used for the estimation. Therewith, the estimation performance is drastically increased, while the calculation effort still remains the same.