A Novel All-Digital Calibration Method for Timing Mismatch in Time-Interleaved ADC Based on Modulation Matrix
Sujuan Liu, Lin Zhao, Shibo Li
Abstract
This paper proposes a novel all-digital background calibration of timing mismatch for a time-interleaved analog-to-digital converter (TIADC). For two different calibration strategies, the absolute calibration and the relative calibration, the inductive expressions of modulation matrices are derived from the coefficient matrices provided by different estimation methods. Based on the modulation matrix, we develop a digital calibration architecture, which enables the output of TIADC to be modulated firstly before being corrected, so the costly matrix multiplication processing can be avoided. This calibration architecture also enables the estimation process of each channel to be independent and can be executed simultaneously, which accelerates the convergence speed of the timing mismatch. We show the efficiency of the calibration structure by simulations, including examples from the literature. Numerical simulation demonstrates that the convergence speed of the timing mismatch has been improved by at least 27%, compared with the estimation method depending on the specified reference channel. The result of FPGA-based hardware implementation shows that the spurious-free dynamic range (SFDR) is improved by 37.63dB.