Calibration of channel mismatch in time-interleaved real-time digital oscilloscopes

A novel method is proposed for the calibration of channel mismatch in a time-interleaved real-time digital oscilloscope (RTDO). A simple simultaneous equation is derived from the Fourier transform of the time-interleaved signals. Thus, it only requires a transfer function of time-interleaved ADCs (TIADCs), while most of previous works have employed additional filters. A measurement method for the transfer function of a commercial RTDO is also proposed. The accuracy of the calibration method is determined by the noise produced after the interleaving process. To validate the proposed method, we measure two-tone signals using a commercial RTDO. The calibrated results clearly show signals at spurious frequencies are substantially reduced.