High-Gain High-Order Dual-Polarized OAM MG Antenna Based on 3-D Non-Uniform Travelling-Wave Current Source

Orbital angular momentum (OAM) has become a research hotspot in radar, communication, and other fields because of its spatial spiral phase distribution in the azimuthal domain. The non-uniform travelling-wave current source (NTCS) model is a universal and systematic theoretical analysis for OAM generation. However, it is limited to two-dimensional distributed circle sources. In this paper, the NTCS model is generalized to the three-dimensional sphere. The far field distribution and OAM spectrum are theoretically derived. The proposed model is applicable to the analysis of many existing spherical antennas and the design of the expected OAM mode group (MG). As a case, a dual-mode dual-polarization OAM MG antenna modified from a Cassegrain structure is designed based on the proposed model. The simulated results show that the antenna generates four OAM MGs with high beam gains, equivalent OAM orders, and cross-polarization suppression.