Measuring the diffraction loss for high frequencies, long distances, and large diffraction angles is difficult because of the high path loss. Securing a well‐controlled environment to avoid reflected waves also makes long‐range diffraction measurements challenging. Thus, the prediction of diffraction loss at millimeter‐wave frequency bands relies on theoretical models, such as the knife‐edge diffraction (KED) and geometrical theory of diffraction (GTD) models; however, these models produce different diffraction losses even under the same environment. Our observations revealed that the KED model underestimated the diffraction loss in a large Fresnel‐Kirchhoff diffraction parameter environment. We collected power‐delay profiles when millimeter waves propagated over a building rooftop at millimeter‐wave frequency bands and calculated the diffraction losses from the measurements while eliminating the multipath effects. Comparisons between the measurements and the KED and GTD diffraction‐loss models are shown. Based on the measurements, an approximation model is also proposed that provides a simple method for calculating the diffraction loss using geometrical parameters.

中文翻译：

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基于屋顶传播测量的毫米波衍射损耗模型

由于路径损耗高，因此很难测量高频，长距离和大衍射角的衍射损耗。确保良好控制的环境以避免反射波也使长距离衍射测量具有挑战性。因此，在毫米波频带上的衍射损耗的预测依赖于理论模型，例如刀刃衍射（KED）和衍射几何理论（GTD）模型；但是，即使在相同的环境下，这些模型也会产生不同的衍射损耗。我们的观察结果表明，KED模型低估了大菲涅尔-基尔霍夫衍射参数环境下的衍射损耗。当毫米波以毫米波频带在建筑物屋顶上传播时，我们收集了功率延迟曲线，并计算了测量的衍射损耗，同时消除了多径效应。显示了测量值与KED和GTD衍射损耗模型之间的比较。根据测量结果，还提出了一种近似模型，该模型提供了一种使用几何参数计算衍射损耗的简单方法。