Design of Planar Dual-Bandstop FSS Using Square-Loop-Enclosing Superformula Curves

A dual-bandstop frequency selective surface (FSS) is designed by unit cells composed of square metallic loops enclosing novel curves generated by a superformula for miniaturization and incident angle stability. The shape of the inner corolla with a constant area may change by the variations of the parameters of the superformula. Consequently, both the resonant frequencies may vary with subject to the limitations of fabrication. At first, each loop (square and corolla) is investigated separately, and then their combination is designed according to the specifications. The dimensions of the unit cell are 10 mm × 10 mm, and their resonance frequencies are 3.46 and 5.14 GHz. The proposed unit cell does not depend on polarization. A prototype of the proposed FSS is fabricated and measured. The simulation results and measurement data agree very well.