This brief introduces a new digital postcorrection technique for calibrating time-interleaved analog-to-digital converters (ADCs). It utilizes one additional sub-ADC to resolve the performance degradation problem near the Nyquist rate that occurred in the conventional multichannel filtering approach. Time skew, gain, offset, and bandwidth mismatches as well as the sub-ADC nonlinearities are all included in the proposed model. One group of coefficients extracted in foreground can be applied to any input frequencies in normal operation. An additional analog subcircuit path is required, but the digital part of the implementation becomes much simpler, which ensures that the overall system complexity does not increase. Furthermore, the digital correction structure can reuse the hardware units in a time-multiplexing manner for further power and resource savings. A 12-b four-channel 1-GS/s ADC is used to demonstrate the performance of the proposed postcorrection.