An Optically Transparent Reflectarray Based on Fine Metal Lines and Low-loss Substrate

A new type of optically transparent reflectarray with fine metal lines (FMLs) and low-loss substrate is investigated in this work. The reflectarray consists of a FML patch, cyclic olefin copolymer (COC) substrate, polyethylene terephthalate (PET) substrate and an indium tin oxide (ITO) ground. The FML patch, with a linewidth of $50 \mu \mathrm{~m}$, adopts a multi-resonant structure to broaden the range of phase variation. At the operating frequency of 29 GHz, the reflection loss and phase change of the proposed reflectarray element are 1.1 dB and 491°, respectively. The fabricated reflectarray achieves a measured gain of $\mathrm{2 3. 3 6} \mathrm{~ d B i}$, a high aperture efficiency of 40.6%, and a $1-\mathrm{dB}$ gain bandwidth of $\mathrm{2 2. 4 1 \%}$, demonstrating great potential in future communication systems.