微波频段粗糙金属表面等效电导率的数值计算及验证

A Numerical Method of Equivalent Electrical Conductivity of Rough Metal Surface at Microwave Frequency Band and Its Verification

为了评估表面粗糙度对微波频段金属表面等效电导率的影响,提出了一种基于梯度模型的粗糙金属表面等效电导率数值计算方法并进行实验验证。首先基于电导率梯度模型,将粗糙金属表面等效为电导率渐变的若干光滑薄层的叠加;其次基于电磁波在薄层内的损耗及薄层间界面的传输特性,对粗糙金属表面的总损耗进行数值计算并获取等效表面电导率;最后运用替换端板谐振腔法对不同粗糙度的黄铜样片在8.98、10.78GHz进行表面电导率测试。实验结果表明：在0.1-3μm的均方根粗糙度范围内,等效电导率随粗糙度增加而减小,且基于梯度模型的等效电导率计算方法所得理论预测值相比于已有理论更符合实测结果。

A numerical method of equivalent conductivity based on a gradient model is proposed to evaluate the effect of surface roughness on the equivalent electrical conductivity of metal surface at microwave band and experimental verification of the method is performed. Firstly, it is based on the gradient model of conductivity that the surface of a rough metal is equivalent to the superposition of several smooth thin layers. Secondly, the loss and transmission characteristics of the electromagnetic wave in each thin layer is based to calculate the total loss of the rough metal surface and to obtain the equivalent surface conductivity. Finally, the resonant cavity with replaceable end plate is used to measure the surface conductivities of machined brass samples with various roughness at 8.98 GHz and 10.78 GHz, respectively. Results indicate that, the equivalent conductivity decreases as the roughness increases for samples with RMS roughness in the range of 0. 1-3 μm and that the theoretical predicted value of the equivalent conductivity from the proposed numerical method has a better agreement with measurement results than that from existing theories.