On the Use of Single-Layered Subwavelength Rectangular Patch Elements for Broadband Folded Reflectarrays

The feasibility of using single-layered subwavelength rectangular patch elements for broadband folded reflectarrays is studied in this letter. The antenna is made of a feed horn, a planar lower reflector, and an upper polarizer. Different to existing folded reflectarray designs in the literature where a halfor near-halfwavelength unit cell is used for lower reflectors, this work employs subwavelength rectangular patch elements on a single-layered substrate for achieving a wide bandwidth of folded reflectarrays. The design is conducted at 10 GHz and composed of 1976 elements on a 405 × 405-mm2aperture. The effect of the polarizers on the antenna's performance is also examined when they are integrated with folded reflectarray structures. The proposed folded reflectarray features a broadband performance with a compact and lowprofile structure. The measured results show that the folded reflectarray with a 0.3λ grid spacing realizes a 1-dB gain bandwidth of 16% with an aperture efficiency of 44%, which demonstrates better behavior than various existing folded reflectarrays. In addition, this superior performance is also comparable to the previous traditional reflectarray design, whereas the antenna depth has been reduced in half.