Analytical Criteria for Designing Multiresonance Filters in Scattering Systems, with Application to Microwave Metasurfaces

Designing filter devices with precisely desired transmission spectra is of utmost importance in wave physics. For sharp (such as elliptic filters zeros), brute-force methods to directly optimize the spectrum face severe numerical challenges, while circuit models and coupled-mode theory apply only certain limits. The authors provide a set universal analytical criteria based on quasinormal-mode (QNMT) for designing 2-port systems, method variety microwave metasurface configured polarization-preserving transmission, reflective polarization conversion, or diffractive anomalous reflection.