Low-Profile Dual Band-pass Frequency Selective Surface with independent bands of operation

A low-profile, modified Complementary Frequency Selective Surface (CFSS) with dual band-pass characteristic is presented. This technique adds independent control of the operation bands, which was a limitation from previous FSSs design based on CFSS concept. The FSS structure utilizes resonant elements and interaction between the layers to deliverer the first operating bandpass response at a low frequency. It is demonstrated that the first order response can achieved miniaturized periodic dimensions of about $\lambda_l/15$ and ultra-thin overall thickness compressed down to $\lambda_l/200$, where $\lambda_l$ is the free space wavelength at the lowest band of operation. An equivalent circuit model (ECM) is presented to explain the working principles of the proposed FSS. This investigation is further supported by parametric studies based on full wave simulation showing how this simple approach allows decoupling of the two bands of operation. A prototype, simultaneously operating at S and C bands is fabricated and tested in a free space environment for validation purpose.