Beijing Institute of Aeronautical Materials， Beijing 100095
为研究电磁波在吸波涂层中的干涉现象，选取了X型羰基铁粉吸收剂，采用同轴法测试了材料电磁参数，通过多次反射方法求解了X型吸波涂层在厚度为1/4波长时反射系数公式；另外，求解了不同厚度X-1型吸波涂层对频率为9.5 GHz平面电磁波反射系数公式，取公式前6项计算了反射系数Γa和反射率Ra。结果表明，多次反射波之间产生了干涉行为，发生了干涉相消现象。Γa、Ra分别与传输线方法计算的Γ和R的值非常接近，表明Γa和Ra可以近似代表X-1型吸波涂层对9.5 GHz电磁波的反射系数和反射率。当X-1型吸波涂层厚度小于1.9 mm或在3.2~6.6 mm时，第二反射波对第一反射波起到干涉相长作用，降低吸波性能，表明优选的吸波涂层厚度应该介于1.9~3.2 mm。
Type X carbonyl iron powder mixed with different proportions of paraffin were used for testing permeabilities and permittivities of these materials to study interference phenomenon of electromagnetic wave in radar absorbing coatings （RACs）. The formula of reflection coefficient of type X RACs to plane electromagnetic wave with the thickness of quarter-wavelength was solved by the method of multiple reflections. And the formula of reflection coefficient of type X RAC to plane electromagnetic wave of frequency at 9.5 GHz with different thickness was also solved in which the first six terms were chosen for calculating reflection coefficient Γa and reflectivity Ra. The results show that interference phenomenon is caused by the multiple reflections of wave. The value of Γa and the value of reflection coefficient Γ calculated by method of transmission line are close to each other which shows Γa and Ra can approximately represent Γ and reflectivity R of type X RAC separately. If the thickness of type X RAC is smaller than 1.9 mm or in the range from 3.2 to 6.6 mm， the second reflected wave will enhance the first reflected wave and increase the reflectivity which indicates the optimum thickness of type X RAC is in the area from 1.9 to 3.2 mm.