Measurement Method of Dispersion Curves for Spoof Surface Plasmon Polaritons

This communication proposes a measurement method of dispersion curves for spoof surface plasmon polariton (SPP) transmission lines (TLs), providing a feasible solution to obtain measured dispersion curves. The proposed method is a generalization of the traditional Bianco-Parodi method, in which general formulas are given to extract the phase constants at different frequencies from the measured S-parameters. The new method can not only eliminate the effect of complicated transition structures, but can also be suitable for higher order modes. In addition, attenuation constants can be extracted, and it can also theoretically provide a possibility to break the limitations of uniform and reciprocal structures. Based on this method, all dispersion curves in different propagation directions are obtained. For example, dispersion curves are measured for two cases, a nearly uniform spoof SPP TL and a single unit of spoof SPP structure, to demonstrate the validity of this method. It is shown that the measured dispersion curves agree well with the simulation results based on eigenmode solver. Hence, the proposed method makes it possible to measure dispersion curves only from a single unit, providing a potential solution to reduce the test error and cost effectively.