Design of a Microstrip Line Fed SIW Ring Antenna With Sixth-Order Circular Polarized Conical Pattern

This paper presents the design of a microstrip line-fed substrate-integrated waveguide (SIW) ring antenna designed to excite a sixth-order circularly polarized conical radiation pattern. Characteristic mode theory indicates that antennas can theoretically support an infinite number of Orbital Angular Momentum (OAM) modes; however, practically exciting higher-order OAM beams introduces significant challenges. This work addresses the difficulties associated with generating higher-order OAM waves using a single patch antenna by proposing a straightforward design featuring a single-ring radiator with vias positioned on its inner side. A comparative analysis highlights the advantages of the SIW configuration in effectively realizing the left hand circularly polarized (LHCP) OAM beam with sixth mode order from the proposed antenna. The dual feed single port mechanism successfully radiates the desired radiation pattern at 6.55 GHz, making the design suitable for satellite communication applications. The validation of the theoretical analysis is demonstrated through the prototype, which shows good agreement between simulation and measured performance parameters. The simplicity of the antenna’s configuration, combined with its enhanced radiation performance, distinguishes it from existing designs and offers a promising solution for practical implementation in OAM-based communication systems.