Dispersion and Polarization Control in Below-Cutoff Circular Waveguides Using Anisotropic Metasurface Liners

This article explores the application of metasurface (MTS) liners in perfect-electric-conducting (PEC) circular waveguides for cutoff manipulation and the introduction of controllable chiral properties. A dispersion equation is derived to predict the propagation characteristics of a circular waveguide lined with an MTS exhibiting a general full tensor surface admittance response. A design procedure for the MTS liner is presented and validated with three design examples. Two of the examples use a capacitively loaded grid topology akin to a Jerusalem cross structure aligned with the principal coordinate system of the waveguide, resulting in a diagonal susceptance tensor. These two examples are used to demonstrate how the dispersion properties of the waveguide can be significantly modified based on the geometry of the MTS-lined waveguide system and the surface admittance exhibited by the MTS. The third design consists of a rotated fully printed Jerusalem cross structure with a general tensor susceptance, which is found to produce a separation in the dispersion curves of the left- and right-hand circularly polarized modes in the waveguide while also producing below-cutoff propagation. Theoretically predicted dispersions are validated with full-wave electromagnetic simulations.