Long Non-Diffractive-Range Bessel-Beam Launcher with Circular Polarization

Thanks to their self-healing, focusing, and limited diffraction behavior, Bessel-beams are promising candidates for the implementation of next-generation near-field wireless links. Their intriguing properties, however, are maintained only up to the so-called nondiffractive range. For this reason, an original, low-profile circularly polarized Bessel-beam launcher with an extremely long nondiffractive range is proposed in this work by exploiting an open-stopband-suppression technique. In particular, a sinusoidally modulated anisotropic metasurface—typically used for leaky-wave antenna designs—is here originally used to design a Bessel-beam launcher at millimeter waves. The proposed device achieves a radiation efficiency of 90% and a nondiffractive range of approximately 2.9 m, which corresponds to 280 free-space wavelengths and to almost 20 times its aperture radius.