Digital Calibration of Nonlinear Memory Errors in Sigma–Delta Modulators

A digital adaptive calibration technique to linearize sigma-delta (ΣΔ) modulators based on an output-referred distortion analysis of discrete-time integrators (DTIs) is presented. A sequential power series (a special form of Volterra series) is found sufficient to model the nonlinear memory errors in a DTI, which entails the application of adaptive polynomial transversal filtering for error correction of the modulator. Error-parameter identification is accomplished by correlating various moments of the digital output with a 1-bit pseudorandom noise, which is injected into the analog input of each DTI of the modulator. Simulations demonstrate the effectiveness of the technique in compensating the signal-dependent errors of first- and second-order ΣΔ modulators.