Generation of radio orbital angular momentum (OAM) waves with circular metallic waveguide

We present a novel way to generate radio waves bearing Orbital Angular Momentum (OAM) in the horn antenna by using a circular metallic waveguide. The OAM mode ℓ = 1 is generated by combination of two TE₂₁ modes inside a circular metallic waveguide. The resulting electrical field distribution and the radiation patterns evidence the properties of waves carrying OAM. The influences of the horn structure on the properties of the generated OAM waves are also studied.