Ultra-long-range Bessel beams via leaky waves with mitigated open stopband

Open stopband (OSB) mitigation techniques are commonly used to improve the far-field radiating properties of leaky-wave antennas based on periodic structures. Recently, leaky waves have been proposed to focus energy in the near field through Bessel beams. However, the focusing character of Bessel beams is notably limited to a maximum distance known as the nondiffractive range. In this work, an OSB mitigation technique is originally exploited to significantly extend the nondiffractive range of a Bessel beam generated by a leaky-wave launcher in the microwave/millimeter-wave range. A comprehensive analysis of this device is presented, comparing the performance of the proposed launcher with the typical structure of a leaky-wave Bessel-beam launcher where the OSB is not suppressed. Theoretical results, corroborated by full-wave simulations, demonstrate that the proposed device achieves an impressive nondiffractive range of about 25 m. The latter, at 30 GHz, approximately corresponds to 2500 wavelengths (in vacuum) and to 50 times the aperture diameter which is about 50 cm. These results look particularly attractive for, e.g., near-field communications and wireless power transfer applications, where focusing energy in narrow regions and over large distances is a key factor.