Constructing dual-frequency OAM circular patch antenna using characteristic mode theory

Abstract

The current wavemodes and their distribution features of the circular patch are analyzed by using the characteristic mode theory. Then, the corresponding characteristic modes are selected and the feed structure is designed to generate the vortex waves carrying orbital angular momentum (OAM), based on the idea that the OAM mode can be realized by combining two orthogonal degenerate modes. The experimental results show that the proposed antenna can effectively implement dual-frequency dual-mode OAM waves. The first-order OAM mode of the electric field component in beam axis z direction is realized at low frequencies, while the second-order OAM mode of the z-component field is obtained at high frequencies. The phase fluctuation of the OAM modes can be explained by the excitation coefficient of the characteristic mode with quantitative properties.