A split-based fully digital feedforward background calibration technique for timing mismatch in TIADC

摘要

This paper presents a split-based feedforward calibration technique for timing mismatch of Time-Interleaved Analog-to-Digital Converter (TI-ADC). The timing mismatch is estimated by using the difference between corresponding sample points of paired split-sub-ADCs, and compensated by a non-derivative interpolation method. Compared with traditional feedback methods with LMS iterative, the proposed feedforward calibration method can achieve much higher calibration speed and the complexity of digital post-processing is greatly relaxed without using of any dummy channel or filters. In addition, it has good calibration effects in both single-tone and multi-tone input conditions. Applied in a 1 GS/s 12-bit TIADC, the simulation result shows a convergence time of 1 x 10(4)Ts under Nyquist frequency input with 2%Ts initial timing mismatch, and the peak signal to noise and distortion ratio of TI-ADC is improved from 37.54 dB to 67.60 dB with a normalized frequency of single-tone input signal f(i)(n)/f(s) = 0.474. For a multi-tone input signal which contains 10 evenly distributed frequency points in the Nyquist frequency range, after calibration, the signal to noise and distortion improves 28.33 dB.