Finite-aperture Microwave Bessel Beams with Vortex Twisting, Fracturing, and Dynamic Phase-shift Control

Finite-aperture microwave vortex beams of various structures in the near-, middle-, and far-field propagation zones have been simulated. The decay of external sidelobes leading to the end of non-diffractive propagation within a fraction of the near-field zone is observed. A ring source of the vortex beams with phase-shift and frequency-sweep control of angular modes and polarization patterns through the use of patch antenna arrays of varying polarization is suggested. A new form of the beam wavefront variation with azimuthal undulation has been proposed that allows one to significantly diversify and dynamically control the beam structure. The consequences of a limited number of antenna patches in a circular array have been considered. The effects of a gradual drop of radiation power along the array and the use of multiple feed points for improving the beams have been simulated.