High Isolation Spoof Surface Plasmonic Transmission Line with Underlying Ground at Terahertz and Microwave Frequency

In this paper, a high isolation spoof surface plasmon polariton (SSPP) based RF transmission line using a dumbbell shaped unit cell with improved confinement ability is proposed. The designed SSPP based structure is having under layer ground, which actually helps in obtaining the low insertion loss over a wide frequency range in the microwave and terahertz (THz) frequency range. The isolation capability of the proposed SSPPs structure is studied by designing two SSPP transmission lines on a same substrate, and measuring the coupling between two lines by varying the spacing between these individual lines. For a detailed comparison, an equivalent microstrip structure comprising of two similar transmission lines on the same substrate as that of SSPPs structure are designed. The numerical simulation and measurement studies of these two designed structures shows that the proposed SSPP transmission line exhibits low insertion loss, better isolation and better confinement ability over a wide frequency range as compared to the conventional microstrip transmission line having similar dimensions.