Relation between cut-off frequency and equivalent circuit of spoof surface plasmon polariton and its applications

Abstract This paper reveals a relation between the cut-off frequency and the simplified equivalent circuit of a spoof surface plasmon polariton (SSPP). An SSPP transmission line (TL) with low upper cut-off frequency is proposed based on the relation. In this SSPP-TL, a double-layer interdigital strip is constructed to increase the capacitance in the simplified equivalent circuit model, and in turn the cut-off frequency is decreased. The proposed SSPP-TL features an upper cut-off frequency of only 2.75 GHz, which indicates that the proposed relation is instructive to design the geometry of an SSPP with low cut-off frequency.