Research Of Compensation Algorithms Of Timing Mismatch Error In TI-ADCs

Analog-to-digital converter(ADC)is a bridge between analog and digital systems and an important part of modern signal processing systems,which is widely used in communications,radar,and test equipment.Recently,the performance of ADC has increased rapidly,but it is far from meeting the industry's need for high-speed and wideband signal digitization.Time-interleaved ADC(TI-ADC)uses multi-chip ADCs to alternately sample the input in the time domain,and then combine the outputs in the order of sampling,which can break the limit of a single ADC and increase the overall sampling frequency by multiple times.In addition,under the condition of same sampling frequency,TI-ADC has a great advantage in terms of cost and power consumption compared to single-chip ADC.However,offset mismatch,gain mismatch,and timing mismatch between multiple ADCs will introduce clutter interference that affects the performance of TI-ADC.Among them,the timing mismatch error is more difficult to detect and correct than other mismatch errors.Therefore,it is of great theoretical significance and application value to study the estimation and correction methods of timing mismatch error in a TI-ADC.In this paper,spectral characteristics of the TI-ADC output with timing mismatch are analyzed in detail.Several typical TI-ADC timing error correction methods are studied in depth and their principles are introduced at length.Combined with simulation experiments,their performance and limitations are analyzed and verified.In order to be applied to wideband multi-carrier signal sampling,this paper proposes a pilot-assisted identification and correction method for timing error.The approach correlates local and corresponding received pilot symbols and phase angle is obtained to get a rough estimate.Then,estimation results are averaged at different timedomain locations to further suppress noise and interference to improve the estimation accuracy.Finally,error vector magnitude(EVM)of the signal is utilized as the optimization target and cubic spline interpolation is used for sampling time phase adjustment,which form an adaptive adjustment loop based on stochastic gradient descent method to complete iterative elimination of the time mismatch error.Compared with existing approaches,this scheme does not require a complicated differential filter and its computation is small.Experimental results show that the proposed algorithm can significantly suppress the error spectrum introduced by timing error and effectively improve the reception quality of multi-carrier modulated signals.