A Digital Adaptive Calibration Method of Timing Mismatch in TIADC Based on Adjacent Channels Lagrange Mean Value Difference

摘要

This paper presents a digital adaptive calibration method to overcome the effect of timing mismatches in the time-interleaved analog-to-digital converter (TIADC). The structure of the channel splitting-recombining is proposed. The TIADC with M channels is divided into log(2)M stages for calibration, and each stage is composed of one or more two-channel sub-systems. The Lagrange mean value difference of adjacent channels is constructed by arithmetical approximation to estimate the timing mismatch. It does not need to oversample the bandlimited input signal with an oversampling ratio. And it does not require the input signal to have significant power over its bandwidth for identification. Timing mismatches are corrected by the cascaded differentiator-multipliers. A reuse structure is developed to reduce the consumption of hardware resources. Simulation results of the four-channel TIADC show that the spurious-free dynamic range (SFDR) can be improved from 31.19 to 73.39 dB. Hardware implementation based on FPGA is also carried out, and the corrected SFDR is measured at 72.29 dB. The approach has low complexity, and the bandwidth of the input signal can reach the Nyquist bandwidth of the complete TIADC system.