Design And Implementation Of Time-interleaved Calibration Algorithm Based On Sine Fitting

With the rapid development of electronic information technology,the demand of precision and speed is higher and higher to the electronic equipment of the signal.The TIADC system can improve the speed of the system and maintain a single slice of the accuracy of the ADC.Nevertheless,due to the inconsistency,it brings the offset mismatch,gain mismatch,time-skew error and bandwidth mismatch between each channel.Time-skew error and bandwidth mismatch will seriously affect the performance of the TIADC system.so accurately estimating and correcting time-skew error and bandwidth mismatch are very important for TIADC system.The principle,model and mismatch problems that exist in the TIADC system are analyzed in this paper.The characteristics of time-skew error and bandwidth mismatch are analyzed.The sine fitting is improved by parameter extraction.After this,time-skew error and bandwidth mismatch can be separated.Firstly,a low frequency test signal is injected to the system,and sine fitting is used to fit the output data.According to the mapping relationship of the mismatched and the parameter of sine fitting,the offset mismatch and gain mismatch of the corresponding channel mismatch are obtained.Then a high frequency test signal is injected to the system,sine fitting is used to estimate the parameters.The SHA circuits of sub-ADCs are approximated to a first-order low-pass single-pole network.The time-skew error and bandwidth mismatch are isolated from the phase parameter extraction and the approximation.Finally,offset mismatch and gain mismatch are calibrated by adder and multiplier.Adjust the delay of input clock to correct time-skew error.Change the phase mismatch of fractional delay filter based on Farrow structure to calibrate the bandwidth mismatch which is real-time correction.According to the mismatch of the separated time-skew error and bandwidth mismatch,mismatches are accurately estimated.Based on this,calibration is carried on.Eventually,the performance of TIADC system is improved.In this paper,a four channel 14bits TIADC system is realized.The dynamic parameters of the system are tested and compared.The test results show that the performance of the corrected system is greatly improved than before correction.The parameter of SNR reaches to 62.2819dB.The parameter of SFDR reaches to 70.0832dB when the input frequency reaches 147.9004MHz.