Design and Optimization of 3-D Frequency-Selective Surfaces Based on a Multiobjective Lazy Ant Colony Optimization Algorithm

Frequency-selective surfaces (FSSs) have many applications in spatial filtering of electromagnetic waves and are commonly used in antennas, polarizers, radomes, and intelligent architecture. Conventional FSS designs have ranged from canonical shapes and fractal patterns on planar surfaces to miniaturized and multilayer designs, with stable filtering responses up to 50°. Much less work has been done on 3-D FSS designs, which include multiresonant structures or cavities that offer improved angular stability, with fields of view up to 60°. Recent advances in additive manufacturing techniques have made fully 3-D FSS designs increasingly popular; however, powerful design tools to exploit such fabrication methods are currently unavailable. In this paper, multiobjective lazy ant colony optimization (MOLACO), an adaptive combinatorial optimization algorithm based on ant colony optimization, is introduced and applied to the problem of polarization and angle independent 3-D FSS design. It will be shown that the MOLACO algorithm generates several innovative and unintuitive unit cell geometries with a single-zero, single-pole response, less than 1% shift from center frequencies and -10 dB rejection and 3 dB transmission bandwidths between 6%-12% for angles of incidence up to 80° in TE and TM polarizations. Comparisons are made between designs generated by MOLACO and existing FSS designs.