The Multiple-Input Multiple-Output (MIMO) radar combines the signals from multiple transmit and receive elements separately to form a virtual array. Consequently, system imperfections in the MIMO radar caused by channel imbalance and mutual coupling are repeatedly present in the virtual array, affecting the beamforming performance. In this paper, the beam pattern deviations caused by these imperfections are described mathematically in relation to a single point target. Furthermore, a nonparametric calibration technique to estimate and compensate for these effects at different angles is presented by exploiting that the same imperfections are present multiple times in the virtual array. The proposed calibration method is applied to measurements with an 8 $\times $ 8 colocated X-band MIMO radar, and the peak sidelobe level (PSL) and the integrated sidelobe level (ISL) are used as performance parameters. The calibration technique is found to improve both the PSL and the ISL by approximately 15 dB within the whole field-of-view (FOV) for antennas that are not minimum scatterers. For angles above ±30° from the antenna boresight, the performance of the proposed calibration method is found to surpass other calibration methods. This is advantageous for MIMO radars as they typically cover a wide FOV.

中文翻译：

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共址 MIMO 雷达的互耦合和信道不平衡校准

多输入多输出 (MIMO) 雷达将来自多个发射和接收元件的信号分别组合成一个虚拟阵列。因此，MIMO雷达中由信道不平衡和互耦合引起的系统缺陷在虚拟阵列中反复出现，影响波束成形性能。在本文中，由这些缺陷引起的波束方向图偏差在数学上与单点目标相关地进行了描述。此外，通过利用虚拟阵列中多次存在相同的缺陷，提出了一种非参数校准技术，用于估计和补偿不同角度的这些影响。建议的校准方法适用于 8 $\次$8个并置X波段MIMO雷达，并以峰值旁瓣电平（PSL）和综合旁瓣电平（ISL）作为性能参数。对于不是最小散射体的天线，发现校准技术在整个视场 (FOV) 内将 PSL 和 ISL 都提高了大约 15 dB。对于天线视轴±30°以上的角度，发现所提出的校准方法的性能优于其他校准方法。这对于 MIMO 雷达是有利的，因为它们通常覆盖较宽的 FOV。