Ultra-Wideband Dielectric Reflectarray Antenna with OAM beams for mm-Wave Applications

The proposed structure is presented to improve the inherited limited bandwidth and reduce the production of grating lobes in reflectarray antennas (RAs). A dielectric RA with 200 mm $\times 200$ mm is designed and simulated to produce an orbital angular momentum beam (OAM) of the second mode with averaged realized gain of around 20 dBi in the band of 25-40GHz, which covers most of 5G mm-wave bands (n257, n258, n260, and n261). To achieve the mentioned specifications, an inter-element spacing of 0.25$\lambda$ is adopted.