Design of dual-polarised multiband frequency selective surfaces using fractal elements

A technique is proposed for the design of multiband frequency selective surfaces (FSSs) that is based on the use of fractal screen elements. The authors demonstrate the design methodology by exploiting the self-similarity of the crossbar fractal to implement a tri-band FSS. Another benefit of this design approach, in addition to its multiband performance, is that the frequency response of both the TE and TM modes are exactly the same, owing to the symmetry in the tree-like fractal structure of the screen elements. Dielectric loading effects have been considered for practical implementation of designs with coverage exceeding two bands. Finally, it is noted that the locations of the individual bands can be controlled by the scaling or similarity factor used in the construction of the fractal screen elements.