Design of a Wireless Link at Microwaves in the Radiative Near-field by Using RLSA Bessel Beam Launchers

In this paper, we deal with the proper definition of the near-field wireless power transfer efficiency between two antennas, by adopting both spatial and spectral approaches to evaluate it. Such a figure of merit allows the evaluation of wireless link performances in the radiating near-field by using RLSA launchers. Numerical results to establish the performances of uniform, zero- th order Bessel, and zero- th order first kind Hankel wireless links are presented. In the final part of the paper, an example of RHCP RLSA Bessel beam launcher at f = 30 GHz implementing a zero-th order, first kind Hankel aperture distribution is proposed as building block for a near-field wireless link, showing that its performances can be considered satisfactory in terms of efficiency, provided that a suitable distance between transmitting/receiving antennas is chosen.