Holographic leaky-wave antennas with independently controlled multiple counter-rotating vortex beams

A holographic leaky-wave antenna based on modulated anisotropic metasurfaces is proposed for the synthesis of multiple counter-rotating vortex beams. The design employs a generalized aperture field estimation method tailored for anisotropic impedance surfaces, enabling independent control over beam orientation, orbital angular momentum mode, power distribution, and polarization. The proposed approach provides a systematic framework for generating multiple beams with a customizable number of petals and tailored, potentially non-uniform, power distributions. By appropriately adjusting the modulation index, the rate of power leakage along the antenna can be precisely controlled, thereby enabling accurate tuning of the antenna gain. Additionally, the use of anisotropic impedance surfaces in hologram synthesis enables polarization control for each individual beam. To experimentally validate the accuracy of the results, a dual polarized, dual-beam prototype is designed, fabricated and measured. The first beam is directed toward the spherical angle of ( \(θ _1 = 30^∘\) , \(φ _1 = 0^∘\) ) with right-hand circular polarization , and its OAM content is synthesized as a superposition of \(l = -3\) and \(l = +3\) , resulting in a six-lobed, counter-rotating vortex beam. The second beam is pencil type with left-hand circular polarization tilted toward ( \(θ _2 = 30^∘\) , \(φ _2 = 90^∘\) ). The proposed multi-beam configuration enables the simultaneous radiation of distinct beam types, each carrying independent spin and orbital angular momentum states.