Current-Based Synthesis of Beam Switching Metasurface Antennas

We extend the current-based metasurface synthesis of tensorial surface impedance to demonstrate beam switching with multiple feeds and one-beam-per-feed. The process optimizes the surface current (as opposed to impedance), and impedance determination is carried out as a post-processing. The cost functional encodes tensor-impedance passivity and realizability, and far-field masks. To achieve beam switching, we add a functional enforcing pairwise cross-testing constraints among all excitations to ensure co-existence of multiple currents on the same aperture due to different feeds. The resulting current-only problem is solved with a nonlinear conjugate-gradient method featuring a closed-form line search, and the optimized tensor impedance is realized using unit cells ad-hoc selected from a database of precomputed geometries.