Direct-conversion radio frequency transceivers are well-substantiated structures for today's wireless communication systems due to their ability in complexity reduction, cost, and power consumption. The unavoidable mismatch between the in-phase (I) and quadrature-phase (Q) branch of the analog front-ends in the direct-conversion transceiver leads to degrading the performance of communication systems. In this article, we address the estimation and compensation of the IQ imbalance (IQI) parameters for both the transmitter (TX) and receiver (RX) in multiple-input/multiple-output systems with space-time block code (STBC) in the digital domain. This article proposes a pre-combiner estimation and compensation of the channel and the frequency-independent IQI scheme based on the repetitive transmission of the pilot sequence using the least square technique. It is worth noting that the proposed method can be extended to any orthogonal STBC. Moreover, the study is applied to IQI in other scenarios including only TX and only RX. Simulation results show that the proposed method achieves better performance in comparison with the existing post-combiner technique. Furthermore, the proposed method requires lower computational complexity when the number of receive antennas is limited.

中文翻译：

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空时分组码多输入多输出系统中的IQ失衡估计与补偿

由于其在降低复杂性、成本和功耗方面的能力，直接变频射频收发器是当今无线通信系统的充分证实的结构。直接变频收发器中模拟前端的同相 (I) 和正交 (Q) 支路之间不可避免的失配会导致通信系统的性能下降。在本文中，我们解决了多输入/多输出系统中发送器 (TX) 和接收器 (RX) 的 IQ 不平衡 (IQI) 参数的估计和补偿问题，其中包含空时分组码 (STBC)数字域。本文提出了一种基于导频序列重复传输的信道预组合估计和补偿以及频率无关的IQI方案，采用最小二乘技术。值得注意的是，所提出的方法可以扩展到任何正交 STBC。此外，该研究还应用于其他场景中的 IQI，包括仅 TX 和仅 RX。仿真结果表明，与现有的后合并器技术相比，所提出的方法取得了更好的性能。此外，当接收天线的数量有限时，所提出的方法需要较低的计算复杂度。仿真结果表明，与现有的后合并器技术相比，所提出的方法取得了更好的性能。此外，当接收天线的数量有限时，所提出的方法需要较低的计算复杂度。仿真结果表明，与现有的后合并器技术相比，所提出的方法取得了更好的性能。此外，当接收天线的数量有限时，所提出的方法需要较低的计算复杂度。