Analyses and Full-Duplex Applications of Circularly Polarized OAM Arrays Using Sequentially Rotated Configuration

This paper presents the analyses of circularly polarized orbital angular momentum (OAM) ring arrays using sequentially rotated configurations. For the studied OAM-based microstrip antenna arrays, the relationship between the excitation settings and the generated OAM modes are studied together with the axial ratio (AR) bandwidths at the beam maximums. Furthermore, a dual-OAM-mode circularly polarized array is proposed for full-duplex applications. Based on the presented OAM-mode selection method, the self-interference due to the strong mutual coupling within the array can be well canceled, leading to a high interport isolation. A demonstrator centered at 15 GHz with OAM modes of +1 and +2 is developed and fabricated for verification purposes. The demonstrator uses a sharing antenna scheme for the two OAM modes to realize a compact architecture. Measured results indicate that the demonstrator characterizes good interport isolation within a wide bandwidth from 13.92 to 16.38 GHz referring to a 45 dB level as well as wide AR bandwidths at the beam maximums.