A Polarization Insensitive Frequency Selective Surface with Bandpass and Bandstop Response

In this paper, a low-profile multilayer polarization independent frequency selective surface (FSS) has been presented. The FSS comprises three layers, one four-legged metallic cross at the top surface and another at the bottom surface with one Jerusalem cross in the middle layer. The layers are separated by two dielectric substrates of thickness 0.79 mm. The small thickness of the substrates has made the structure thin and less bulky. The proposed FSS structure exhibits both bandpass and bandstop responses. The structure has been designed to realize two notches in the reflection response at 7.15 GHz and 13.02 GHz evincing bandpass response and a notch in the transmission response at 8.22 GHz manifesting the bandstop response. The proposed multilayered FSS provides a 3 dB transmission bandwidth of 25% at 7.15 GHz and 65.6% at 13.02 GHz, whereas reflection bandwidth of 26.3% is achieved at 8.22 GHz. This multilayer FSS structure exhibits polarization insensitive nature with respect to linear polarization. At 7.15 GHz and 8.22 GHz, the resonant frequency shift remains within 5% with the increase in angle of incidence up to 75 degrees. The higher band at 13.02 GHz does not shift more than 12% for differently polarized waves up to the above mentioned angle of incidence. This FSS can be utilized for allowing a particular frequency band to transmit and shielding the other frequency bands at Ku and C band while it is also used to enhance the gain and directivity of an antenna at X band.