A frequency response mismatches estimation method for time interleaved analog-to-digital converter based on chirp-Z transform

This article proposes a novel frequency-response mismatch estimation method for time-interleaved analog-to-digital converters (TIADCs) based on the Chirp-Z Transform (CZT). Unlike the traditional Fast Fourier Transform (FFT)-based estimation, which suffers from fixed frequency resolution and spectral leakage, the CZT offers flexible frequency mapping with adjustable start frequency, bandwidth, and resolution. This flexibility enables high-precision spectral analysis at arbitrary frequency points, significantly improving the accuracy and stability of amplitude and phase mismatch estimation, particularly near sub-ADC Nyquist boundaries. Both simulation and hardware experiments validate the proposed approach. Therefore, the CZT can avoid spectral leakage by flexibly adjusting its computation parameters. Simulation results demonstrate that the CZT-based estimation reduces spectral leakage and improves calibration accuracy by ∼7 dB compared with the FFT-based method in spurious-free dynamic range (SFDR). Furthermore, a 4-channel 12.5 GS/s TIADC prototype is used to verify the feasibility of the proposed algorithm, showing a 20 dB enhancement in SFDR after calibration. The results confirm that the proposed CZT-based estimation provides a high-resolution, leakage-free, and computationally efficient solution for precise channel mismatch calibration in broadband TIADC systems.