Radially periodic leaky-wave antenna for Bessel-beam generation over a wide frequency range

A radially periodic two-dimensional leaky-wave antenna is studied for the generation of zeroth-order Bessel beams within a limited spatial region and over a wide frequency range. The antenna design is wideband and based on an annular metal strip grating placed on top of a grounded dielectric slab, supporting a cylindrical leaky wave with a fast backward spatial harmonic. The focusing capabilities of the relevant leaky-wave aperture fields are investigated over the considered frequency range (15 to 21 GHz), in conjunction with the dispersion analysis of the optimized structure, which is developed by means of an efficient in-house method-of-moments code. Fullwave simulations using a commercial tool including a simple coaxial feeder are presented and discussed, demonstrating the desired wideband operation. The antenna design is validated by means of measurements performed on a manufactured prototype, considering different frequencies and components of the electric field within the nondiffracting range of the system. The proposed design represents an attractive simple and low-cost solution potentially able to generate arbitrary-order Bessel beams at microwaves as well as in the millimeter-wave and terahertz frequency regions.