New Models for the Calibration of Four-Channel Time-Interleaved ADCs Using Filter Banks

New linear models to calibrate four-channel time-interleaved analog-to-digital converters are proposed and investigated. The ideal four-periodic correction filters, which cancel distortions, are computed as a function of the error filters that model the analog transfer function of each channel, including the sampling time. These correction filters are then approximated as a linear combination of base filters and new accurate models with a limited number of free parameters are proposed. Calibration is performed using the recursive least squares algorithm to estimate the coefficients of the linear combination (and the offset term). The resulting algorithms are tested for accuracy, convergence speed, and stability in a fixed-point implementation, and are compared with previously published linear background calibration techniques. The proposed filter bank significantly improves the accuracy/complexity tradeoff with respect to previously published techniques.