Terahertz bandpass frequency selective surface with improved out-of-band response

A second-order bandpass frequency selective surface (FSS) for terahertz applications is experimentally demonstrated in this paper. The proposed FSS is designed using miniaturized element unit cells that enable analysis of their frequency by an equivalent circuit model. A transmission zero is introduced in the upper stopband of the transmission response for improving the out-of-band performance. Numerical and experimental results show a harmonic-free response up to three times the passband center frequency.