A Method for Uniform Unit Cell Placement on Complex 3-D Surfaces Using STL for EM Applications

This letter presents a new method for placing frequency selective surface (FSS) unit cells on complex curved surfaces, while uniformly maintaining their geometric dimensions and periodicity using a computer-aided design (CAD) model. The proposed grid-based placement technique eliminates the need for prior knowledge of any surface equation and ensures minimal distortion with high placement accuracy, thereby addressing a key limitation of the existing approaches. To demonstrate its effectiveness, a circular Jerusalem cross unit cell geometry is wrapped on various uniform and non-uniform surfaces (paraboloid, complex 3D surfaces, human head, and sinusoidal surface) for exhibiting diverse electromagnetic (EM) functionalities at microwave frequencies. Each structure is analyzed through full-wave simulations alongside its planar counterpart, followed by 3-D printed fabrication and free-space measurements. The close agreement between measured and simulated results confirms the robustness of the proposed technique for modeling FSS geometries on complex surfaces in advanced defense and wireless communication applications.