Design and modeling of low-loss symmetric slow-wave transmission lines

This paper theoretically models and experimentally verifies a low-loss spoof surface plasmon (SSP) mode-based transmission line. A circuit model is proposed for a symmetric SSP structure and the dispersion curve, cut off frequency and Bloch impedance of the periodic structure are calculated. A compact mode converter is proposed and verified experimentally for the connection to coplanar waveguides (CPWs) to form a low-loss slow-wave transmission line (SW-TL). The proposed design is compared with a conventional transmission line and its excellent performance is experimentally evidenced. Operating as a low loss TL, the SW-TL is ready for possible MMIC applications, taking advantage of its ultrathin planarity, highly confined fields, and flexible structure.