Direct-conversion receivers (DCRs) have been adopted in wideband communication systems owing to their simple structure and low cost, however, their operation is affected by amplitude and phase mismatches between their analog inphase (I) and quadrature (Q) branches, as well as the discrepancy of low-pass filter coefficients between these two channels. In this paper, a blind adaptive frequency-dependent I/Q imbalance compensator is proposed, which exploits the complex properness (second-order circularity) of ideal constellation mappings to provide more enhanced insight into the problem setting within the proposed compensator. This serves as a basis for a novel full second-order performance assessment framework, which is established through a joint consideration of the weight error covariance and complementary covariance in both the transient and steady-state stages. This conjoint analysis is further shown to facilitate accurate quantification of the overall mirror-frequency interference attenuation capability of the proposed compensator. Simulation results in an orthogonal frequency division multiplexing (OFDM) transmission system demonstrate the excellent performance of the proposed compensator.

中文翻译：

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宽带直接变频接收机的复特性启发盲自适应频率相关 I/Q 不平衡补偿

直接变频接收机（DCR）由于其结构简单、成本低而被广泛应用于宽带通信系统，然而，它们的运行受到模拟同相（I）和正交（Q）支路之间幅度和相位不匹配的影响，以及作为这两个通道之间低通滤波器系数的差异。在本文中，提出了一种盲自适应频率相关 I/Q 不平衡补偿器，它利用理想星座映射的复杂特性（二阶循环性）来提供对所提议补偿器内问题设置的更深入的了解。这是新的完整二阶绩效评估框架的基础，这是通过联合考虑瞬态和稳态阶段的权重误差协方差和互补协方差而建立的。这种联合分析进一步显示出有助于准确量化所提出的补偿器的整体镜像频率干扰衰减能力。正交频分复用 (OFDM) 传输系统的仿真结果证明了所提出的补偿器的出色性能。