Digital Compensation of Timing Skew Mismatches in Time-Interleaved ADCs by Source Separation

This article proposes an adaptive all-digital background compensation of timing skew mismatches in time-interleaved analog-to-digital converters (TI-ADCs). The proposed approach uses the orthogonality between the desired component representing ideal samples of the TI-ADC input signal and the timing skew mismatch errors. Our technique is the first attempt to use a source separation mechanism to recover the desired component in the digital output of TI-ADC. A finite impulse response (FIR) filter implementing the Hilbert transform and two separate adaptive FIR (A-FIR) filters are exploited to implement this recovery process. The proposed technique works at frequencies close to the full admissible Nyquist frequency range, and its operation does not depend on the number of sub-ADCs (SADCs). This method operates without any extra SADC. The main cost introduced by the proposed compensation technique is the requirement of two adjustable FIR filters. This cost is proportional to the number of taps in these FIR filters that can be optimized according to the specific application. This technique is validated through various behavioral simulations and a field-programmable-gate-array (FPGA) implementation. With the proposed method, the signal-to-noise and distortion ratio (SNDR) is enhanced from 23.06 to more than 66.82 dB in a 12-bit TI-ADC when the standard deviation of timing skew mismatches is 10% of the TI-ADC’s sampling interval.