Compact Dual-Band Independently Modulated Huygens' Metasurface for Full-Space EM Wave Manipulation

Huygens' metasurface (HMS) provides an effective approach for designing high-efficiency metadevices through engineering the interfacial electric and magnetic responses. However, compact Huygens' meta-atom (smaller than one-third lambda(h), lambda(h) is the operating wavelength at the higher band of the meta-atom) with dual-band independent modulation capabilities is rarely reported due to the following challenges: 1) the unbalanced electric/magnetic resonances and 2) the coupling between different resonators. In this article, a novel Huygens' meta-atom with miniaturized structure (0.32 lambda(h)) and dual-band independent modulating capability is proposed. The proposed meta-atom comprises two modified vertical split ring resonators (MVSRRs) and two planar split ring resonators (SRRs) that are separated by two layers of substrate. The SRRs with smaller stripline widths could generate a relatively weak electric resonances, while the capacitor-loaded MVSRRs with larger stripline widths could generate relatively strong magnetic resonances; hence, two pairs of balanced resonances with moderate intensities are obtained. Moreover, the miniaturization design makes two pairs of resonators should be kept at an adequate distance. The moderate resonance intensities together with adequate distance contribute to a considerably low coupling between them. Hence, the transmission/reflection complex coefficient at the upper/lower band of the proposed meta-atom could be independently engineered. Based on the proposed meta-atom, a full-space metasurface (MS) with a reflective focusing function at 11 GHz and a transmissive orbit angular momentum generation function at 16 GHz is designed, fabricated, and measured. There is a good coincidence between the simulation and measurement. The proposed method opens a new avenue toward designing miniaturized dual-band independently modulated meta-devices based on Huygens' principles.