Blind Calibration Method for Two-Channel Time-Interleaved Analog-to-Digital Converters Based on FFT

Abstract

Time-interleaved analog-to-digital(TIADC) is an effective way to improve the sampling rate of an analog-to-digital converter(ADC) system. However, the unavoidable timing mismatch, gain mismatch and offset mismatch significantly degrade the performance of TIADC. In this paper, a blind calibration algorithm based on Fast Fourier Transform Algorithm(FFT) is proposed for the gain, offset and timing mismatches in a two-channel TIADC system. The explicit amplitude relationships between the input signal and the spurs caused by mismatches are derived in the frequency domain. With the explicit amplitude relationships, the frequency component of the input signal, which has the maximal energy, is used to estimate the gain and timing mismatches. The amplitude spectrum of the spur caused by offset mismatch is used to estimate the offset mismatch. The proposed algorithm needs no extra circuits and no training signal and can dynamically track the changes of the mismatches. Simulations show that the estimation errors are no more than 4%. Finally, a two-channel TIADC prototype is used to verify and demonstrate the proposed algorithm.