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.

Calibration for Sample-And-Hold Mismatches in M-Channel TIADCs Based on Statistics

“…where • is the floor operator, and |•| is the absolution operator. In (17), σ 2 stands for the variance of the signal x[n]…”

“…LMS algorithm is adopted to estimate β m . By considering all the distinctions between the mean squared differences indicated by (17), the loss function can be established as…”

“…The results are depicted in Figure 12. One can achieve better SINAD and LSSR along with larger batch size for identification, because the cost function is established under the circumstance where N → ∞ as (17). However, the resource consumption also increases with the batch size.…”

“…In reality, electronic mismatches, which periodically modulate the input signal and degrade the output signal's dynamic performance, are inevitable. In recent years, methods have been put forward to mitigate timing mismatches [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], bandwidth mismatches [18,19], frequency response mismatches [20][21][22][23][24][25][26][27][28][29][30] (frequency response mismatch contains the gain, timing and bandwidth mismatches altogether), and nonlinearity mismatches [31][32][33][34]. To consider all kinds of mismatches, ref.…”

Analysis of TIADC channel mismatch effects on high-resolution range profile

“…In TIADC systems, channel mismatches seriously degrade the signalto-noise and distortion ratio (SNDR) and spurious-free dynamic range (SFDR) [18,19,20,21,22,23,24,25,26,27,28,29]. In published literature, studies of TIADC are based on the effects of channel mismatches on the spectrum or dynamic performance such as SNDR and SFDR [14,16,17,18,19,20,21,22,23,24,25,26,27,29,30,31,32]. Under the condition of large bandwidth, it is impossible to eliminate channel mismatches completely.…”