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.