Design And Implementation Of TIADC Bandwidth Mismatch Calibration Algorithm Based On Adaptive Filtering

With the continuous improvement of technology,Analog-to-Digital Converter(ADC)is more and more widely used in modern information processing systems,but it still cannot meet requirements of accuracy and sampling rate in the field of high-speed signals.The time-interleaved analog-to-digital converter(TIADC)doubles the conversion rate of the ADC by alternately sampling while maintaining the conversion accuracy of sub-ADCs substantially unchanged.However,the various mismatches between channels seriously affect the performance of the sampling system.When the sampling rate is high,the bandwidth mismatch error between channels has a serious impact on performance.Therefore,this thesis mainly studies the calibration algorithm for TIADC bandwidth mismatch.In this thesis,an adaptive filtering algorithm based on autocorrelation is used to correct the bandwidth mismatch in TIADC system.Aiming at the problem that the Least Mean Square(LMS)algorithm converges too slowly in the adaptive iterative process,this thesis analyzes the autocorrelation error factor of the bandwidth mismatch into the iterative process of the LMS algorithm in the form of a linear function.The coordinate descent method is used to optimally solve each parameter in the iterative formula.Based on this,the coefficients of the adaptive filter are obtained and the calibration of the TIADC input signal is completed.So that the algorithm has a higher convergence speed in the initial stage of the iteration,and the iterative step size is reduced to ensure the accuracy when the convergence is completed.In addition,the symbolic bits of the output of the interpolation filter are determined by calculating the correlation coefficient between the sampled signal and the reference signal,thus correcting the possible false convergence in the algorithm.In this thesis,four AD9233 chips are used to form a four-channel,12-bit,420 MSPS TIADC system,and the effectiveness of the proposed bandwidth mismatch adaptive algorithm is verified by hardware.In this thesis,the output spectrum of TIADC before and after calibration is analyzed.The results show that the calibrated TIADC system achieves 69.34 dB SFDR at the input frequency of 198.0064 MHz,which is 35.79 dB higher than the SFDR before calibration.Therefore,the algorithm has better calibration effect.