A Single-Layer Broadband Reflectarray Using Variable-Width Ring Clover Elements for Millimeter-Wave 5G Applications

A variable-width ring clover element is proposed for the design of a single-layer broadband reflectarray antenna (RA). The proposed element containing a clover patch and a variable-width ring achieves a nearly linear phase curve with a small slope. A set of almost parallel and linear reflection phase curves within the frequency range from 29 GHz to 46 GHz for both TE and TM modes indicates that the proposed element obtains broadband performance for dual-polarization. Finally, an off-set reflectarray prototype consisting of 826 elements is fabricated and measured for both x- and y-polarization. The measured maximum gain exceeds 30 dBi, while the maximum aperture efficiency (AE) surpasses 50%. More importantly, the RA achieves a 2 dB gain bandwidth of over 30% and an AE bandwidth exceeding 30% for both polarizations.