Design of a hexagonal-shaped metamaterial unit cell for L-, S-, and C-band microwave applications

A compact triple-band hexagonal split-ring resonator-based metamaterial unit cell is proposed for multiband microwave applications covering the L-, S-, and C-bands. The designed structure consists of three concentric hexagonal split rings integrated with a parallel double-E-shaped resonator and a cross-shaped ground plane fabricated on an FR-4 substrate. The electromagnetic response of the unit cell was investigated using the finite integration technique in Computer Simulation Technology Microwave Studio through waveguide-port excitation and periodic boundary conditions. The simulated transmission characteristics exhibit three distinct resonances at 1.88, 3.56, and 5.44 GHz, corresponding to L-, S-, and C-band applications. The extracted effective parameters demonstrate epsilon-negative behavior in the ranges of 0–1.77 and 1.85–2.03 GHz, mu-negative behavior between 3.46–4.08 and 4.95–5.53 GHz, and negative refractive index characteristics from 0.63 to 1.23 GHz. The proposed unit cell exhibits excellent compactness with an electrical size of 0.071λ × 0.08λ and an effective medium ratio of 12.4 at the first resonance. Mutual coupling effects were evaluated using 1 × 1 to 4 × 4 array configurations, confirming stable multiband performance. A 15 × 12 prototype array was fabricated and experimentally characterized, showing good agreement between simulated and measured responses. The proposed metamaterial structure provides a promising solution for Sub-6 GHz 5G, GPS, satellite communication, Wi-Fi systems, and gain-enhancing antenna reflector applications. All three measured resonances lie within 1% of the simulated values. Equivalent-circuit, effective-medium dispersion, and parameter-retrieval equations are presented to explain the origin of the negative permittivity and permeability, and fabrication-tolerance and thermal-stability estimates are provided to support the robustness of the design.