Angular Momentum Multiplexing via a Shared Aperture Patch Antenna

Angular momentum (AM) multiplexing technique provides multiple information channels for electromagnetic waves (EMWs) modulation at the same frequency, improving spectrum efficiency effectively. Among AM multiplexing techniques, the patch antenna has the advantage of minimization, simple feeding circuits, and easy integration. Nevertheless, limited reports provide theoretical guidance for designing AM multiplexing patch antennas. Herein, we propose a scheme to achieve AM multiplexing via a shared aperture patch antenna. The radiating structure consists of multiple radiating patches sharing a common physical aperture, each of which is responsible for producing different AM-carrying waves. By analyzing the theoretical model built on a dipole representation of the patch antenna, the shapes and the desired current patterns of these patches can be determined according to the AM mode of the expected EMWs. Besides, the sizes and feeding structures of these patches can be studied by investigating their radiating characteristics using characteristic mode (CM) theory. For proof-of-concept, a prototype was designed, fabricated, and measured for the generation of four orthogonal AM-carrying waves coaxially at 5.8 GHz. The experimental results agree reasonably well with the simulated ones, demonstrating that the proposed scheme provides an efficient guidance for the design of AM multiplexing patch antennas.