Effect of Offset Mismatch in Time-Interleaved ADC Circuits on OFDM-BER Performance

Abstract

This paper analyzes the effect of the offset mismatch in time-interleaved analog-to-digital converter (TI-ADC) circuits on bit error rate (BER) performance of a receiver for pulse amplitude-modulated or quadrature amplitude-modulated signals in orthogonal frequency division multiplexed systems. Exact BER expressions, as well as simplified BER expressions that hold for high signal-to-noise ratios (SNRs) and large offset mismatch values only, are derived. From the obtained exact BER expressions, a condition is established on the offset mismatch level, under which the BER performance shows an error floor at high SNRs. Numerical results further show that if we keep the offset mismatch level below 25% of the threshold above, which the offset mismatch causes an error floor, there is essentially no BER performance degradation compared with the offset-mismatch free case. Our analysis further evinces that the tolerable level of the offset mismatch is proportional to the square-root of the number of sub-ADCs, indicating that as opposed to what might be expected, the offset mismatch level that can be tolerated actually increases with the number of sub-ADCs.