Investigation of millimeter (mmWave) and Terahertz (THz) channels relies on channel measurements and estimation of multi-path component (MPC) parameters. As a common measurement technique in the mmWave and THz bands, direction-scan sounding (DSS) resolves angular information and increases the measurable distance. Through mechanical rotation, the DSS creates a virtual multi-antenna sounding system, which however incurs signal phase instability and large data sizes, which are not fully considered in existing estimation algorithms and thus make them ineffective. To tackle this research gap, in this paper, a DSS-oriented space-alternating generalized expectation-maximization (DSS-o-SAGE) algorithm is proposed for channel parameter estimation in mmWave and THz bands. To appropriately capture the measured data in mmWave and THz DSS, the phase instability is modeled by the scanning-direction-dependent signal phases. Furthermore, based on the signal model, the DSS-o-SAGE algorithm is developed, which not only addresses the problems brought by phase instability, but also achieves ultra-low computational complexity by exploiting the narrow antenna beam property of DSS. Simulations in synthetic channels are conducted to demonstrate the efficacy of the proposed algorithm and explore the applicable region of the far-field approximation in DSS-o-SAGE. Last but not least, the proposed DSS-o-SAGE algorithm is applied in real measurements in an indoor corridor scenario at 300~GHz. Compared with results using the baseline noise-elimination method, the channel is characterized more correctly and reasonably based on the DSS-o-SAGE.

翻译：毫米波与太赫兹信道的探究依赖于信道测量及多径分量参数的估计。作为毫米波与太赫兹频段的常用测量技术，方向扫描探测通过解析角度信息并提升可测距离，利用机械旋转变现了虚拟多天线探测系统。然而，该技术引发的信号相位不稳定性和庞大数据规模问题，未被现有估计算法充分考量，导致其应用效能不足。为弥补这一研究空白，本文提出面向方向扫描探测的空间交替广义期望最大化算法，用于毫米波与太赫兹频段的信道参数估计。为精准表征毫米波与太赫兹方向扫描探测的测量数据，该算法将相位不稳定性建模为扫描方向依赖的信号相位。在此基础上，基于信号模型开发的DSS-o-SAGE算法不仅解决了相位不稳定性带来的问题，更通过利用方向扫描探测窄天线波束特性实现了超低计算复杂度。仿真合成信道的实验验证了所提算法的有效性，并探讨了DSS-o-SAGE中远场近似的适用区域。最后，将所提DSS-o-SAGE算法应用于300吉赫兹室内走廊场景的真实测量中。与使用基线噪声消除方法的结果相比，基于DSS-o-SAGE的信道表征更为正确合理。