Estimation of Carrier Frequency Offset With I/Q Mismatch Using Pseudo-Offset Injection in OFDM Systems

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This work presents a novel carrier frequency offset (CFO) estimation algorithm, based on pseudo-CFO (P-CFO), to estimate the CFO value under the conditions of <emphasis>I/Q</emphasis> mismatch for direct conversion structures with 2-dB gain error and 20-deg. phase error in frequency selective fading channels. To circumvent CFO with <emphasis>I/Q</emphasis> mismatch, the proposed P-CFO algorithm rotates three training symbols by adding extra frequency offset into the received sequence to improve CFO estimation. Simulation results indicate that the estimation error of the proposed method is about 0.3 ppm, which is lower than those of two-repeat preamble-based methods. Additionally, the proposed P-CFO algorithm is compatible with the conventional method, and is appropriate for SoC implementation. The proposed scheme is implemented as part of an orthogonal frequency-division multiplexing wireless receiver fabricated in a 0.13-<formula formulatype="inline"><tex>$\mu$</tex></formula>m CMOS process with 3.3<formula formulatype="inline"><tex>$\,\times\,$</tex></formula> 0.4 mm<formula formulatype="inline"> <tex>$^{2}$</tex></formula> core area and 10-mW power consumption at 54-Mbits/s data rate. </para>