Agile Bessel Beam Leaky-Wave Launcher With Suppressed Open Stopband and Multiport Feeding

This work investigates the generation of Bessel beams from a double-strip bull-eye planar leaky-wave launcher. The structure offers wideband operation and an extended non-diffracting range, thanks to the suppression of the open stopband, which typically affects periodic leaky-wave antennas. A comparative analysis is reported with a single-strip implementation, which shows the stopband and therefore offers a reduced non-diffracting range. To enhance functionality with respect to conventional bull-eye structures operating in the near-field, the double-strip launcher is excited through a flexible substrate integrated waveguide multiport feeder, which enables dual-polarization and controllable aperture fields and allows for the generation of both zeroth- and first-order Bessel beams. Both simulations and measurements are reported, demonstrating beam focusing over larger distances in the near-field. Also, for the first time, an adaptable and polarization agile launcher is studied and experimentally validated to increase the non-diffractive range of a planar and compact structure.