Selectively Generating High-Purity Vortex Beams by a Planar Filtenna With a Compact Integration of Spiral SSPP and HMSIPW

Orbital angular momentum (OAM) waves exhibit orthogonal phase characteristics and have attracted considerable interest in wireless communications, radar imaging, and electromagnetic sensing applications. This paper presents a compact planar OAM filtenna that integrates an incomplete uniform circular array (UCA), a spiral spoof surface plasmon polaritons (SSPPs) waveguide, and a half-mode substrate integrated plasmonic waveguide (HMSIPW) filter. The SSPPs feed excites sequentially rotated circularly polarized elements to generate vortex waves, while the HMSIPW introduces bandpass filtering without increasing the size. Theoretical analysis establishes the mode relation, revealing the OAM generation mechanism. Simulated and measured results confirm frequency-selective radiation from 4.12 to 5.82 GHz, with six modes and mode purities up to 0.96. The proposed filtenna achieves compact, high-purity, and frequency-reconfigurable OAM radiation, showing great potential for wireless communication and radar imaging systems.