Analysis Of The Electromagnetic Scattering Characteristic Of Frequency Selective Surfaces

Frequency Selective Surfaces (FSS) are structures which comprise periodic arrays of patches or apertures. The periodic structures can control the transmission and reflection of the electromagnetic wave. For incident electromagnetic waves of different frequencies and angles, they show different scattering characteristic. The periodic structures exhibit total transmission or total reflection for an incident wave in the resonance frequency.The method of moment (MoM) is a method of good accuracy and steadiness, which is suitable for solving problems of scattering and radiation. Because the shape of patch or aperture could be described by matrix when using MoM, arbitrary shapes of FSS can be calculated.In this thesis, the scattering characteristic of the FSS is discussed using the spectral method. For an infinite FSS, the problem is reduced to one cell by Floquet theorem. Then the operator equation is built with the help of Green function. After that, the equation is turned to the spectral domain using Fourier transform. The solution of the equation is gotten employing the method of moment, and the induced current could be found with the solution. Then the fields are divided into the Floquet harmonics of TE and TM polarization. The concept of the normalized voltage is given, and the scattering parameters of the harmonics are available, thus, the scattering matrices are obtained. For the multilayer structures, the composite scattering matrix is gotten by combining the scattering matrices of the elements.The program for analyzing the scattering characteristic of FSS is written using this technique, and several examples are given. The characteristic of FSS with single screen and double screens are calculated respectively, and factors influencing the characteristic of FSS are analyzed, the advantages of double screens are also demonstrated.