Microwave propagation in round guiding structures based on double negative metamaterials

This paper presents a theoretical study of guided propagation in a waveguide containing ordinary and negative refractive index (NRI) media. The cut-off frequency of positive/negative combined media is examined. It is calculated for each propagating mode as a solution of a characteristic equation that is solved in terms of Bessel functions, taking into account the implications of the negative refraction. In contrast to what happens in ordinary propagation, mode mixing and crossing and no cut-off modes are found for negative values of epsilon, mu and refractive index n. The investigation considers the range 1-80 GHz where metamaterials have been demonstrated to work with negative parameters. The results are also compared with the negative core/negative cladding case. Some applications are suggested for devices operating in the microwave frequency domain.