Recently, hybrid-polarized Bessel beams have been proposed as a valid solution to radiate focused beams in the near-field region at microwaves and millimeter-waves. As shown by the leaky-wave design proposed in this work, such beams can be excited in a resonant cavity by etching a slot on the ground plane which is fed through a rectangular waveguide (RWG). Matching networks are often required to efficiently couple the waveguide to a highly resonant cavity. We thus propose a semi-analytical technique for such waveguide-fed launchers which saves a significant computational burden with respect to full-wave optimizations. The matching technique consists in the numerical choice of the design parameters of two RWG discontinuities after a single full-wave simulation. Hence an optimum solution is found by numerically minimizing an analytical objective. Theoretical results are in a remarkable agreement with …