In this letter, we modify the extended advanced integral equation model (EAIEM) for electromagnetic backscattering and bistatic scattering from rough surfaces with small to moderate heights. We extend the first-order approximation of the error function as introduced in the EAIEM model to the second order, in a hope to be more suitable for large roughness and high frequency. In addition, a new transition model for the reflection coefficient is proposed to make the dependences explicit on the mean surface curvature, frequency, and dielectric constant, whereas making no use of the complementary term, the effect of inadequate evaluation of this term is mitigated. Comparison with POLARSCAT data for backscattering and with European Microwave Signature Laboratory (EMSL) measurements for bistatic scattering demonstrates the validity of the updated model.

中文翻译：

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用于从随机粗糙表面散射的扩展高级 IEM 的修改

在这封信中，我们修改了扩展的高级积分方程模型 (EAIEM)，用于从小到中等高度的粗糙表面的电磁反向散射和双基地散射。我们将EAIEM模型中引入的误差函数的一阶近似扩展到二阶，希望更适合大粗糙度和高频。此外，提出了一种新的反射系数过渡模型，以明确平均表面曲率、频率和介电常数的相关性，同时不使用补充项，减轻了对该项评估不充分的影响。与用于反向散射的 POLARSCAT 数据和用于双基地散射的欧洲微波特征实验室 (EMSL) 测量值的比较证明了更新模型的有效性。