A miniaturized frequency selective surface by using vias to connect spiral lines and square patches

In this paper, a new miniaturized frequency selective surface (FSS) structure is proposed. Compared with previous FSSs, the proposed structure has promising miniaturization features. The array element is implemented by using vias to connect structures on two surface layers. The dimensions of the proposed array element are only 0.035λ×0.035λ. The top layer is constructed by four spiral-shaped structures; the bottom is made of four square-shaped patches. They are connected in series by vias. In so doing, the values of the resonant component values are increased; thus the resonant frequency is shifted downwards. The frequency response is insensitive to the oblique incidence angle. Also, the proposed design is symmetric rotationally on the xy (the surface) plane and can be applied for circular polarization applications.