Title: A Cost-Effective Preamble-Assisted Engine With Skew Calibrator for Frequency-Dependent I/Q Imbalance in 4 x 4 MIMO-OFDM Modem
Authors: Lai, Wei-Chi
Liao, Yuan-Te
Hsu, Terng-Yin
Department of Computer Science
Keywords: Clock generator;dynamic frequency scaling;frequency-dependent I/Q imbalance;I/Q mismatch;MIMO-OFDM
Issue Date: 1-Aug-2013
Abstract: Variations in I/Q gains, phases, and filters of the RF frontend, namely frequency-dependent I/Q imbalance (FDI), are an important factor in OFDM-based wireless access. To enable the proper function of a 4 x 4 MIMO-OFDM receiver this work proposes a low-complexity preamble-assisted solution using only one complex divider and one complex multiplier to handle significant FDI distortions. An all-digital multiphase and multi-rate clock generator (MPRCG) was built to support fast dynamic frequency scaling for FDI estimation and compensation and for efficient implementation. Based on the proposed MPRCG, a skew calibration was also realized to tune I/Q timing coherently via multiphase A/D clocking. Performance evaluation showed that the proposed approach incurs an SNR loss of 1.5 dB to maintain a packet-error rate of less than 10% under a 1 dB gain error, 15 degrees phase error and worse filter mismatch. Thus, this solution not only provides adequate performance, but also makes FDI estimation and compensation more cost-effective.
URI: http://dx.doi.org/10.1109/TCSI.2013.2239431
ISSN: 1549-8328
DOI: 10.1109/TCSI.2013.2239431
Volume: 60
Issue: 8
Begin Page: 2199
End Page: 2212
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