Efficient Floquet Port Modeling of Electromagnetic Periodic Structures in a Finite Element Method

This paper presents a method to analyze the electromagnetic periodic structures. This method is based on the Floquet's theorem for modeling Floquet port in finite element method (FEM). The modeling of Floquet port consists of two main parts: the calculation of the Floquet mode field and the imposition of the absorbing boundary condition (ABC). Firstly, using the Floquet's theorem, we derived the general expressions of the field in different modes and different incident angles. Then, the Flqouet multimode ABC is investigated to obtain better absorption and thus improve the computational accuracy and speed. Finally, a frequency selective surface (FSS) is analyzed and compared with commercial software ANSYS HFSS to demonstrate the accuracy of the presented method.