TIADC Digital Calibration Based on apFFT Phase Measurement

The Time-interleaved Analog-to-digital Converter (TIADC) enables higher sampling rates while preserving high resolution. However, mismatches in offset, gain, and particularly time skew across multiple ADCs significantly degrade data acquisition accuracy, with time skew being the most challenging to eliminate. This paper introduces a novel digital calibration method for time skew in TIADC. The high accuracy of all-phase Fast Fourier Transform (apFFT) in phase measurement is leveraged to estimate the phase values of each sub-ADC. By utilizing the first sub-ADC as the reference channel, the relative phase differences and real phase discrepancies are calculated, which allows for accurate estimation and compensation of the time skew. This calibration does not require reference channels and extensive data points. The pilot signal is simple to generate without stringent frequency constraints. Results from simulation data and actual measurements using a TIADC designed with commercial ADCs indicate that this digital calibration method holds great potential in reducing mismatch errors, substantially enhancing the TIADC's metrics of SFDR and SNDR.