Flat-top Vortex Beam Synthesis Based on Multipole Moment Expansion

This paper utilizes the multipole moment expansion (MME) method to synthesize a flat-top vortex beam. Instead of the previous step function, a piecewise function is adopted as the target pattern function to meet the synthesis requirements. Taking a concentric circular array with five rings as an example, the vortex beam with mode +1 can maintain its directivity stably within $8^{\circ}-38^{\circ}$, verifying the effectiveness of the proposed method.