An efficient calibration method for digital bandwidth interleaving sampling system

Abstract

Digital bandwidth interleaving (DBI) is a technique that can simultaneously increase system sampling rate and bandwidth. While DBI can reduce the impact of clock jitter on the dynamic performance of the system compared to time-interleaved sampling systems, achieving dynamic performance comparable to time-interleaved analog-to-digital converters (TIADC) remains challenging due to phase misalignment in crossover bands caused by analog filters and nonlinearity in analog mixers. To address these issues, this paper proposes a method to calibrate DBI sampling systems using PRBS signals. This method involves injecting pseudo-random binary sequence (PRBS) signal into the system input as a background signal and calculating the correlation between the output sampling sequence and the PRBS sequence to obtain the response of each sampling channel. Compared with traditional single tone signal or pulse signal, this method offers a more efficient background calibration method. To verify the effectiveness of this method, this paper designed a hybrid parallel sampling system combining DBI and TIADC with a 20 GSPS sampling rate and 8 GHz bandwidth to evaluate the effectiveness of the calibration method. In the performance test of the sampling system before and after calibration, this calibration method improved the system's Signal-to-Noise and Distortion Ratio (SINAD) by up to 13 dB, Spurious Free Dynamic Range (SFDR) by up to 27 dB, and phase response flatness better than 0.3 radians.