Adiabatic Floquet-Wave Expansion for the Analysis of Leaky-Wave Holograms Generating Polarized Vortex Beams

In this paper we combine the aperture field estimation technique and adiabatic Floquet-wave expansion method for the analysis of leaky-wave holograms capable of generating orbital angular momentum vortex waves. In these formulations the propagation and leakage constants are theoretically estimated and, as a result, the aperture field and far-zone field are calculated. Thus, the conditions required to achieve the desired topological charges for the far-field region are obtained. This theoretical approach significantly reduces the computational complexity in such a way that the analysis of holograms with large dimensions is possible with low memory requirements. Isotropic and anisotropic unit cells are used to realize the holograms. It has been shown that the anisotropic cells give an additional degree of freedom, leading to improved performance in the control of wave polarization. The holograms are designed to generate vortex beams with topological charge of m =2 and circular polarization states in the microwave regime. To evaluate the accuracy of the proposed method, the results of the theoretical model and full-wave simulations are compared, with good agreement.