Frequency offset and I/Q imbalance compensation for direct-conversion receivers
Frequency offset and I/Q imbalance compensation for direct-conversion receivers
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DOI：
10.1109/twc.2004.842969
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发表时间：
2005-03
影响因子：
10.4
通讯作者：
Guanbin Xing;Manyuan Shen;Hui Liu
中科院分区：
文献类型：
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作者：
Guanbin Xing;Manyuan Shen;Hui Liu
两种类型的无线系统的缺陷，即，频率偏移和同相/正交（I/Q）的不平衡，在本文中解决。射频（RF）直接变频中的I/Q不平衡不仅引入了不希望的带内镜像干扰，而且降低了载波估计的精度。为此，我们提出了一种基于导频的基带频率偏移和I/Q不平衡补偿方案。提出了一种对I/Q不平衡具有鲁棒性的低成本非线性最小二乘（NLS）频率估计器。还推导出一个I/Q不平衡补偿结构，包括两个阶段：有限脉冲响应（FIR）滤波器，补偿频率相关的不平衡;和一个非对称相位补偿器，纠正频率无关的错误。通过利用嵌入在导频符号中的相位旋转来优化补偿系数。计算机仿真和实验结果都验证了该方案在各种I/Q不平衡情况下的有效性。
Two types of wireless system imperfections, namely, frequency offset and in-phase/quadrature (I/Q) imbalance, are addressed in this paper. The I/Q imbalance in radio frequency (RF) direct-conversion not only introduces an unwanted in-band image interference but also degrades the accuracy of carrier estimation. Toward this end, we propose a pilot-based scheme for both frequency offset and I/Q imbalance compensation at the baseband. A low-cost nonlinear least squares (NLS) frequency estimator robust to the I/Q imbalance is developed. Also derived is an I/Q imbalance compensation structure that consists of two stages: a finite impulse response (FIR) filter that compensates the frequency dependent imbalance; and an asymmetric phase compensator that corrects the frequency independent error. The compensation coefficients are optimized by exploiting the phase rotation embedded in the pilot symbols. Both computer simulations and experiment results verify the effectiveness of the proposed scheme in various I/Q imbalance scenarios.