The imbalance between in-phase (I) and quadrature (Q) branches of quadrature down-conversion receivers creates interference between the mirror frequencies in baseband. We introduce two new adaptive algorithms for compensating frequency-dependent IQ imbalance in orthogonal frequency-division multiplexing (OFDM) systems. The proposed algorithms utilize frequency-domain observations to update filter weights of a time-domain IQ mismatch compensator (IQMC) based on a mini-batch gradient descent search approach. The update rule in the first algorithm is based on the kurtosis criterion, which is a blind adaptation method. The second algorithm is based on minimizing the Euclidean distance (ED) between the frequency-domain impaired signal and the known received reference signal, which is a pilot-aided method. A low-complexity method is introduced to obtain the gradient of cost functions that are only based on the IQMC coefficients and the frequency-domain observations. Numerical results demonstrate that the proposed algorithms reduce IQ imbalance considerably. The proposed adaptation schemes outperform conventional time-domain IQMC schemes in high signal-to-noise ratio region and also use a much smaller number of adaptation parameters than the previous frequency-domain IQMC methods.

中文翻译：

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使用频域观测的时域自适应 IQ 失配补偿


正交下变频接收器的同相 (I) 和正交 (Q) 分支之间的不平衡会在基带中的镜像频率之间产生干扰。我们引入了两种新的自适应算法，用于补偿正交频分复用 (OFDM) 系统中与频率相关的 IQ 不平衡。所提出的算法利用频域观测来更新基于小批量梯度下降搜索方法的时域 IQ 失配补偿器 (IQMC) 的滤波器权重。第一种算法中的更新规则基于峰度准则，这是一种盲自适应方法。第二种算法基于最小化频域受损信号与已知接收参考信号之间的欧几里得距离（ED），这是一种导频辅助方法。引入了一种低复杂度方法来获取仅基于 IQMC 系数和频域观测值的成本函数的梯度。数值结果表明，所提出的算法大大减少了 IQ 不平衡。所提出的自适应方案在高信噪比区域优于传统的时域 IQMC 方案，并且比以前的频域 IQMC 方法使用更少数量的自适应参数。