Surface Waveguides Supporting Both TM Mode and TE Mode With the Same Phase Velocity

Two kinds of surface-wave waveguide (SWG) topologies are proposed in this paper with the objective to achieve the property of supporting both transverse magnetic (TM) and transverse electric (TE) modes with the same phase velocity. The first type is composed of two frequency-selective surfaces (FSSs) as layers whose dominant modes are TM mode and TE mode, respectively. For illustration'C the combination of loop-type FSS and wire-grid-type FSS is analyzed and its dispersion characteristics are examined as well. The second class also consists of two layers. For the top layer, there are gaps in one direction and continuous conducting strips in the orthogonal direction. The bottom layer is created from a 90° rotation of the top layer. As a particular illustration, a modified bow-tie-like SWG structure is investigated. The simulated results show that the two proposed SWG structures exhibit the property of supporting both TM mode and TE mode with the same phase velocity over a broad bandwidth. In addition, the effects of lattice types on dispersion diagrams are discussed in this paper. Near field measurements are also carried out to validate the simulations and good agreements are achieved.