A square root unscented Kalman filter for estimating DAC and loopfilter nonidealities in continuous-time sigma-delta modulators

In this work, an unscented Kalman filter with improved numerical properties is shown to be able to simultaneously estimate the major nonidealities of continuous-time sigma-delta modulators. Circuit imperfections in sigma-delta modulators like, e.g., nonlinearities in the feedback digital-to-analog converters are known to highly reduce the modulators´s performance. The state of the art shows several techniques to compensate for some of these nonidealities, whereby most of the methods only focus on single parameters or can only be applied to specific modulator structures. The presented method is capable of estimating the most serious nonideal circuit parameters concurrently whilst not being limited to specific modulator structures.