A Low-loss Miniaturized Dual-band Reconfigurable Intelligent Surface Unit Cell with An Integrated RF Choke

In recent years, reconfigurable intelligent surface (RIS) has garnered considerable attention for their ability to manipulate electromagnetic (EM) waves, effectively establishing virtual line-of-sight (LoS) paths to mitigate wireless signal attenuation caused by path loss and shadowing. RIS consists of low-cost, passive, controllable dielectric patches, usually referred to as unit cells. However, RIS often exhibits relatively low gains in practice, necessitating the use of a dimensionally large RIS with hundreds, thousands, or even tens of thousands of unit cells to achieve significant performance improvements. Additionally, most of the existing RIS prototypes are designed to work optimally only at a single frequency, limiting their applicability across different bands. This letter introduces a low-loss, miniaturized, dual-band RIS unit cell design operating at 5.8 GHz and 7.3 GHz. The unit cell is equipped with an integrated radiofrequency (RF) choke to prevent unnecessary losses. Each unit cell measures 13 × 13 mm2, approximately 0.25 ðoe† of the 5.8 GHz frequency. The proposed design is capable of shifting the phase of incident EM waves by 180◦ at both frequencies while maintaining minimal losses. By simulations, we demonstrate the ability of the proposed RIS design to perform beamsteering across various angles in both frequency bands.