Transmission-Line Model and Propagation in a Negative-Index, Parallel-Plate Metamaterial to Boost Electron-Beam Interaction

A negative-index metawaveguide (NIMW) comprised of stacks of planar metal sheets loaded with periodic split-ring resonator apertures is modeled using a transmission-line (TL) analysis, and analyzed in detail. The proposed model provides a useful tool to extract the wave impedance and effective homogenized parameters of the metamaterial, ideal for design and optimization purposes. The dominant mode of the NIMW is transverse-magnetic, with a large longitudinal component of the electric field that enables its strong interaction with an electron beam and opens new opportunities for microwave generation and radiation detection. The inherent bi-anisotropy of its loaded inclusions is also examined within our TL theoretical framework, and a solution design to suppress its effect is presented. Finally, since the proposed geometry is shown to support an additional transverse-electromagnetic mode due to strong spatial dispersion, proper excitation of the NIMW is discussed and simulated.