A TIADC mismatch calibration method for digital storage oscilloscope

TIADC (Time Interleaved Analog Digital Converter) is widely used in engineering to enhance sample rate. However, in TIADC system, the offset and gain of each sub-ADC are not same and sample interval between two sub-ADCs are not equal. Thus, mismatch error is unavoidable in TIADC, and the system performance will be degraded. A method based on statistics and FFT (Fast Fourier Transform) analysis is proposed to calibrate the mismatch error in TIADC. The statistic value is utilized to get offset error, and FFT is used to estimate gain and time skew error. Finally, we calibrate the mismatch error by set the analog adjustment element integrated in ADC. The proposed method is validated in a TIADC based digital storage oscilloscope whose sample rate is 5GSPS. Experiment results show that SNR is enhanced and the spectrum spurs are reduced after mismatch errors are calibrated by proposed method.