Broadband and Broad-Angle Multilayer Polarizer Based on Hybrid Optimization Algorithm for Low-Cost Ka-Band Applications

We present a method to design planar broadband and broad-angle multilayer polarizers. The proposed procedure is based on a hybrid method that combines the analytical transmission line model and the full-wave Floquet analysis in the frequency domain. The unit-cell analysis allows to create a database that relates the geometry with the metasurface impedances. Thus, any kind of geometries (especially those that do not have an equivalent model) can be used. As the database is created for a single-layer structure, the computation time needed for the design process is reduced (compared with the full-stacked unit-cell). As an example, a polarizer is designed as an add-on device that could be integrated to any linearly polarized antenna (without affecting its behavior) to create circular polarization. Experimental results for a five-metasurface-layer design are given, demonstrating insertion loss lower than 0.5 dB and an axial ratio less than 3 dB over the entire band ranging from 24.84 to 30.24 GHz, which corresponds to a fractional bandwidth of 19.6% for an incidence of 0°-50°.