Dual High‐Order Orbital Angular Momentum Modes Generation Based on Spoof Surface Plasmon Polaritons With In‐Phase Excitation

ABSTRACT A method for generating dual high‐order orbital angular momentum (OAM) modes by integrating spoof surface plasmon polariton (SSPPs) and spoof localized surface plasmon (SLSPs) is proposed. The proposed design consists of N rotationally arranged SSPP waveguides periodically loaded with SLSP patches, which enables broadband circularly polarized (CP) radiation and introduces a dynamic phase. Unlike conventional approaches that rely on excitation phase control and complex feeding networks, the proposed method utilizes dynamic and geometric phases to synthesize the required phase distribution for high‐order OAM modes, thereby eliminating the need for phase‐shifting networks. Moreover, exploiting the leaky‐wave theory, dual high‐order OAM modes with l = − N + 1 and l = N + 1 are generated by varying the frequency to alter the dynamic phase. The experimental results confirm that the proposed device is capable of generating high‐order l = −7 and l = +9 OAM modes at 9.7 and 13.0 GHz, with gains (divergence angles) of 8.4 dBic (33°) and 5.6 dBic (23°), respectively. This work provides a phase‐network‐free solution for dual high‐order OAM generation with frequency‐controlled mode switching, demonstrating potential for applications in sensing, radar detection, and mode‐division multiplexing systems for wireless communications.