A Dual-Band Independent Modulated Huygens’ Metasurface With Small Frequency Ratio Under In-Plane Coupled Resonance

Huygens’ metasurfaces have attracted significant interest due to high-efficiency EM wave front manipulation capability. However, dual-band independently modulated Huygens’ metasurface with extremely small frequency ratio and ultrathin profile is still rarely reported due to following challenges: 1) strong coupling between two closely located Huygens’ resonances 2) insufficient magnetic resonance intensity within ultrathin profile. Herein, a novel in-plane decoupling method is proposed to effectively tackle issues discussed above. By introducing an extra strong electric resonance between two closely located resonances as a “baffle”, the coupling between them has been significantly suppressed, hence enabling dual-band independent modulation capability. By increasing the miniaturized magnetic resonators, sufficient magnetic resonance has been obtained within an ultrathin profile, which in turn contributes to complete complex- amplitude modulation on transmission/reflection wave. Based on the proposed concept and three-layer cascaded structure, a dual-band Huygens’ unit cell is designed with an overall size of 0.28 × 0.28 × 0.06 λ<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (where λ is the free space wavelength at higher operation band) and an extremely small frequency ratio of 1.21. As proof-of-concept demonstration, a dual-band Huygens’ metasurface is designed to independently perform different functions i.e. transmissive bifocal lens and reflective single focal lens at two closely located frequencies. Both simulation and measurement results are provided and the good coincidence between them verifies the proposed method. This work possesses promising application prospect in multifunctional and bi-directional wireless communication systems.