Design and experimental verification of backward-wave propagation in periodic waveguide structures

Experimental results for the demonstration of backward-wave or double-negative (DNG) propagation in waveguide technology combining inductive windows and split-ring resonators are presented and discussed in depth. A novel segmented prototype has been designed, fabricated, and measured, thus allowing the analysis and discussion of different length structures. The experimental characterization proves the DNG nature of the devices by comparing the phase of the transmission coefficient S₂₁ for different length structures. Dielectric and metallic losses linked to the resonators also limit the transmission levels of these very compact structures in the longitudinal dimension, and the sources of such losses are interpreted through the comparison of measured results with full-wave electromagnetic simulations.