A High-Efficiency Optically Transparent Reflectarray Antenna Based on Frequency Selective Surfaces

In this paper, a high-efficiency optically transparent reflectarray antenna based on frequency selective surfaces (FSSs) is proposed. The top patch and the bottom FSS of the reflectarray are designed using fine metal lines (FMLs), with a linewidth of 30 µm. The bottom FSS functions as a band-stop filter, replacing the traditional single-faced metal ground to enhance the overall antenna transparency. At the frequency of 45 GHz, the phase shift range of the reflectarray element reaches 362°, and the return loss is less than 1.9 dB. The final reflectarray antenna achieves a measured gain of 24.51 dBi, corresponding to an aperture efficiency of 43.8%. The measured 1-dB gain bandwidth extends to 17.8% (42-50 GHz). This bandwidth can adapt to the millimeter-wave (mmWave) wireless communication standard IEEE 802.11aj.