Analysis of metal insulator metal plasmonic transmission lines for improved rectenna's coupling efficiency

The efficient utilization of traveling wave metal-insulator-metal (MIM) tunneling structures promotes the use of rectennas in energy harvesting applications. These MIM structures can be looked at as plasmonic transmission lines. In this paper, different topologies of MIM lines are analyzed with the aim of integrating them with nano-antennas. The effect of geometrical parameters on the transmission lines characteristics, such as effective refractive index, propagation length and characteristic impedance, is investigated. Three types of transmission lines are considered: vertical coupled strips, lateral coupled strips and nanostrip line. Detailed design curves for these transmission lines are presented and discussed. Such curves can be utilized for the efficient matching between the transmission line rectifiers and nantennas. Enhancing the coupling efficiency leads to improving the overall efficiency of the rectenna system.