Novel Folded Reflectarray and Transmitarray Antenna Generating Long Nondiffractive Bessel Beams Carrying OAM With Integrated Feed

A novel folded reflectarray and transmitarray antenna (FRTA), featuring a long distance, no diffraction, high mode purity, and low profile, is proposed to generate high-order Bessel beams carrying orbital angular momentum (OAM). First, two meta-atoms are designed for a full 2π phase coverage and amplitude variation from 0 to 1. Second, metasurfaces are constructed to adjust amplitude and phase independently, with a horn antenna integrated with the upper metasurface as a feeding source. Finally, the FRTA is simulated, fabricated, and measured to verify its generation efficiency of high-order Bessel OAM beams. The full-wave measurement results coincide well with the simulation results and theoretical derivation. The generated beam is more parallel and has a longer non-diffractive distance than conventional Bessel beams. In addition, mode l = 2, 3, 4 achieves approximately 80% mode purity, and more than 65% mode purity is achieved within 12–15 GHz, covering the 21.4% OAM bandwidth. Our study holds promise for applications in radar detection, beam forming, and wireless communications.