Calibration Algorithm Design And Implementation Of Timing Mismatch In Time-interleaved ADC Based On Cross-correlation

With the rapid development of electronic information technology,the demand of speed and precision for Analog-to–Digital Converter(ADC)is higher and higher.The speed of a single ADC is hardly raised because of the limitation of process.Time-interleaved ADC(TIADC)is an effective solution.Unfortunately,the different characteristics of ADCs and the deviation of multiphase clock certainly produce channel mismatches which severely degrade TIADC's performance.So the researches on channel mismatches of TIADC become a hot topic at home and abroad.A background calibration algorithm of timing mismatch using the cross-correlation technique based on standard FIR differentiator is proposed.In the process of seeking the derivation produced by standard FIR differentiator,amplitude errors of standard FIR differentiator will decrease calibration precision.In view of this problem,the module of derivation in calibration algorithm is improved.This algorithm can get a differentiator that has a smaller amplitude error by using two fractional delay filters according to the method of Thiran approximation when the input is in the first Nyquist Band.More accurate derivation can be obtained from the Thiran-based differentiator.So,the calibration precision can be improved.On that basis,the Thiran-based differentiator is optimized by multiplexing sub-filters to obtain a differentiator that has lower complexity to save resource.The paper adopts improved algorithm based on differentiator to estimate the error of timing mismatch.And the output of TIADC is compensated by the first-order Taylor expansion to acquire calibrated value.In this thesis,a four-channel 12 bits,420MSPS time-interleaved system is realized with four AD9233 chips produced by ADI Company to validating the effectiveness of improved algorithm.The experimental results show the system's performance after calibration.The parameter of SFDR reaches to 76.40 dB,and increases 33.61 dB compared with pre-calibration when input frequency is 149.97620 MHz.