Joint Estimation of Carrier Frequency Offset and I/Q Imbalance in the Presence of Time-Varying DC Offset

Umut YUNUS  Hai LIN  Katsumi YAMASHITA  

IEICE TRANSACTIONS on Communications   Vol.E93-B    No.1    pp.16-21
Publication Date: 2010/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.16
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Transmission Systems and Transmission Equipment for Communications
OFDM,  carrier frequency offset,  I/Q imbalance,  time-varying DC offset,  direct-conversion receiver,  

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Due to the importance of maintaining the orthogonality among subcarriers, the estimation of carrier frequency offset (CFO) is a crucial issue in orthogonal frequency division multiplexing (OFDM) systems. The CFO estimation becomes complicated in OFDM direct-conversion receivers (DCRs), where additional analog impairments such as I/Q imbalance and time-varying DC offset (TV-DCO) exist. In this paper, we propose a novel joint estimation method for CFO and I/Q imbalance in the presence of TV-DCO. By using the linear property of the TV-DCO and employing a periodic pilot sequence, the desired estimates can be obtained in closed-form. Simulation results confirm the validity of the proposed method.