Multimodal Transmission-Matrix Analysis of Microstrip Lines with Symmetric and Glide-Symmetric Periodic Loads

We perform a dispersive analysis of periodic microstrip lines by simulating a single unit cell and making use of the multimodal transmission matrix method. Transmission matrices involving one or more higher-order modes are used, and the results are compared with the analysis of a large number of unit cells and with a commercial electromagnetic software. The use of higher-order modes is found to be relevant in geometries with strong asymmetric cross sections, as happens in glide-symmetric microstrip lines.