Analysis and design of a single layer double square slot frequency selective surface with single stopband between double passbands

Square loop and square slot are the simplest and commonly used elements of frequency selective surfaces (FSSs) providing bandstop and bandpass responses, respectively. Despite it is already known that employment of a double square slot structure presents a tunable stopband between two passbands, it is not clear which parameters of the structure are crucial for tunning the inbetween stopband. We propose an analysis of a double square slot FSS considering its element as a parallel connection of square slot and square loop predicting two geometrical parameters of the constituent square loop are crucial for tunning the inbetween stopband. The stopband is tunable by changing geometrical parameters of the constituent square loop and does not depend on geometries of the constituent square slot. The validity of this analytical prediction is verified by full wave EM simulation results.