进气道格栅能够避免电磁波进入腔体形成强散射，同时可改善飞行器表面进气道唇口造成的不连续性，有效降低飞行器的电磁散射特性。基于快速多极子算法，以斜切矩形口直腔体为研究对象，利用波导模式传输理论阐述了格栅的电磁屏蔽原理，分析了格栅尺寸与雷达散射截面（RCS）的关系，以及极化角与格栅布局方向的关系。基于干涉相消原理，提出了横向和纵向尺寸非均匀格栅设计，与均匀格栅的RCS进行了对比。数值仿真结果表明：横向非均匀格栅的RCS缩减在前向±15°范围内超过8 dB，纵向非均匀格栅在±35°范围内具有明显的RCS缩减效果，部分角度RCS缩减超过20 dB。此外还提出了双层格栅设计来减小格栅间距和深度，数值仿真结果表明当双层格栅中单层格栅横向间距小于半波长条件时，双层格栅能获得与单层格栅几乎相同的电磁屏蔽效果。
Inlet grilles can prevent electromagnetic waves from entering the cavity to form strong scattering sources, improve the surface discontinuousness of air vehicles, and thereby reduce their scattering characteristics. Taking the leaning rectangular straight cavity as the research object, this study illustrates the principle of electromagnetic shield using the theory of waveguide mode propagation based on the algorithm of fast multi-pole method. The relationship between the size of the grille and the Radar Cross Section (RCS) is analyzed as well as that between the polarization angle and the direction of the grille. The inhomogeneous grille in the longitudinal and horizontal dimensions is designed based on the principle of destructive interference. Numerical simulations indicate that: compared with that of the homogeneous grille, the RCS of the inhomogeneous grille in the horizontal dimension is reduced beyond 8 dB within the range of ±15° in the front direction. The RCS of the inhomogeneous grille in the longitudinal dimension is clearly reduced within the range of ±35°, and the numerical value is beyond 20 dB within partial angles. Additionally, two layers of grilles are proposed to decrease the depth along axis x and the space between adjacent grilles. Numerical simulations show that: when the space between adjacent grilles is smaller than half of the wavelength, almost the same electromagnetic shielding effects as those of dense single layer of grilles is achieved.
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