Calibration method considering second-order error term of timing skew for a novel multi-channel ADC

The mismatch of timing skew between ADC channels restricts the performance of time-interleaved analog-to-digital converters (TIADCs) seriously. In our previous work, we proposed a novel 7-channel TIADC and its timing skew calibration based on dual-ADC mutual calibration, in which only the first-order term of timing skew is calibrated. In this paper, insufficiency of first-order calibration for timing skew is discussed and an improved calibration scheme, which calibrates the first two order terms of timing skew, is proposed. Simulation of the 14-bit TIADC with MATLAB shows that with timing skew in the range of ±0.02T_s, and the normalized input frequency f_in/f_s=0.34, SNDR and SFDR of the output signal of the TIADC are only 50.7dBc and 53.2dBc, and reach 74.1dBc and 79.8dBc after first-order calibration. However, SNDR and SFDR achieve 86.1dBc and 105dBc after calibration through the improved scheme, and the TIADC performance is enhanced significantly.