DC Offset Mismatch Calibration for Time-Interleaved ADCs in High-Speed OFDM Receivers
Zero Intermediate Frequency (zero-IF) receivers with two analog-to-digital converters (ADCs) in In-Phase and Quadrature (IQ) branches are widely used in emerging multi-Gigabit wireless Orthogonal Frequency Division Multiplexing (OFDM) systems. Because ordinary ADCs could not meet the demands of sampling rate in the system, two time-interleaved analog-to-digital converters (TI-ADCs) could be an attractive alternative for sampling speed improvement in the receiver. However, the mismatches among the parallel sub-ADCs can degrade the performance significantly without calibration. Targeting the DC offset mismatch of the TI-ADCs, this paper proposes calibration algorithm based on decorrelation least-mean-squares (LMS) and recursive-least-square (RLS) utilizing the comb-type pilots in OFDM frame, which could calibrate the two TI-ADCs in (IQ) branches simultaneously. The calibration algorithm has the property of fast convergence. Simulation results show that the BER performance is improved by the proposed algorithm.
KeywordsMulti-Gigabit time-interleaved ADC mismatch calibration parameter estimation orthogonal frequency division multiplexing (OFDM)
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