Realization of Flat-Topped Electromagnetic Orbital Angular Momentum Vortex Wave With a Square Array

Orbital angular momentum (OAM) vortex waves are a potential solution to the issue of scarce spectrum resources. However, most of the OAM waves generated by array antennas are narrow beams, which have uncontrollable beamwidths. To increase the angular coverage of OAM waves, this letter discusses the realization of vortex electromagnetic waves with flat-topped radiation patterns. By constructing a piecewise function of the target flat-topped radiation pattern and adopting the synthesis method of Bessel-Fourier expansion, the radiation patterns of the flat-topped EM vortex wave can be realized. Our results show that the synthesized flat-topped OAM wave can keep the directivity stable in a given wide-angle range. This may provide theoretical support for wide-angle vortex EM communication technology.