A fast TIADC calibration method for 5GSPS digital storage oscilloscope

Abstract

Time-interleaved analog to digital convertor (TIADC) is widely used in engineering to increase the sample rate of acquisition system. However, the mismatches between sub-ADCs in TIADC system result in the distortion of sample output and decrease the sample performance. This paper focuses on the calibration of offset, gain and timing skew mismatches. A novel method based on statistical theory is proposed to estimate offset mismatch of each channel. This method can reduce the impact of noise on offset mismatch calibration. The amplitude of main spectrum is utilized to calibrate gain mismatch, and the average value of each sub-ADC is employed to calibrate timing skew mismatch. Meanwhile, gain mismatch and timing skew mismatch are calibrated by STPNM (Simplified Three Point Newton's method). The proposed calibration method is implemented in a four-channel TIADC based digital storage oscilloscope whose sample rate is 5GSPS. The experiment results show that the impact of mismatches can be reduced effectively and the calibration can be finished in a short time because the convergence is very fast.