Metal-Only 3-D Unit Cell for Reflectarrays With Independent Dual-Band Operation Biedma Pérez, Andrés Pérez Escribano, Mario Parellada Serrano, Ignacio Palomares Caballero, Ángel Padilla De La Torre, Pablo García-Vigueras, María This letter presents a metal-only reflectarray based on a 3-D unit cell with dual-band capability. The 3-D unit cell is a square waveguide whose vertical walls include resonator elements with independent frequency performance. Different resonator geometries are analyzed to obtain a reflected phase variation in the target frequency band and to be feasible for 3-D manufacturing. C-shaped and triangle-shaped resonators are selected to obtain the required phase shift in reflection. A reflectarray prototype is designed, including pairs of resonators where the C-shaped resonator controls the low-frequency band, and the triangle-shaped resonators do so for the high-frequency band. The main reflected beam directions for each frequency band are different to show the independent phase tuning of the resonators. The prototype is manufactured using stereolithography with a subsequent silver coating. Measured results show realized gains of 21.2 dBi in the 18 GHz band and 23.63 dBi in the 26.75 GHz band, with a good agreement with the simulated results 2025-07-24T11:53:38Z 2025-07-24T11:53:38Z 2025-03-05 journal article Biedma-Pérez, A., Pérez-Escribano, M., Parellada-Serrano, I., Palomares-Caballero, Á., Padilla, P., García-Vigueras, M., & Molero, C. (2025). Metal-only 3-D unit cell for reflectarrays with independent dual-band operation. IEEE antennas and wireless propagation letters, 24(7), 1824–1828. https://doi.org/10.1109/lawp.2025.3548310 https://hdl.handle.net/10481/105633 10.1109/lawp.2025.3548310 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional IEEE