A cost-effective preamble-assisted engine with skew calibrator for frequency-dependent I/Q imbalance in 4 ×4 MIMO-OFDM modem

Wei Chi Lai, Yuan Te Liao, Terng-Yin Hsu

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

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 ×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° phase error and worse filter mismatch. Thus, this solution not only provides adequate performance, but also makes FDI estimation and compensation more cost-effective.

Original languageEnglish
Article number6428662
Pages (from-to)2199-2212
Number of pages14
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume60
Issue number8
DOIs
StatePublished - 5 Feb 2013

Keywords

  • Clock generator
  • dynamic frequency scaling
  • frequency-dependent I/Q imbalance
  • I/Q mismatch
  • MIMO-OFDM

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