A Spectral-Correlation-Based Blind Calibration Method for Time-Interleaved ADCs

Abstract

With the quick expansion of signal bandwidth in communication systems, time-interleaved Analog-to-Digital Converters (TI-ADC) provide quick pathway to very high sampling speed. Nonetheless, mismatches among the sub-ADC channels are major performance limiting factors for TI-ADCs. With the scaling of CMOS processes, all-digital background calibration techniques with blind estimation have been actively pursued in recent years to compensate for the mismatches from TI-ADCs. In this paper, a new all-digital background calibration technique is introduced. The technique achieves blind estimation by exploiting the correlation difference between the signal component and the mismatch spurs. This method can process wideband signals and can be implemented with low calibration overhead. The technique is verified with extensive simulations over a 2GS/s 12bit 16-channel ADC. Simulation shows that, with ADC mismatch spurs over −40dBc, the new technique can reliably suppress the spurs to be lower than −80dBc within the duration of about $1.2\times 10^{6}$ samples with a typical wideband OFDM (orthogonal frequency-division multiplexing) signal.