OAM Multiplexing Using Uniform Circular Array and Microwave Circuit for Short‐range Communication

This chapter focuses on an orbital angular momentum (OAM) multiplexing technique, based on a uniform circular array and microwave circuit, called the Butler matrix, for the short‐range wireless communication. The unique feature of this technique is its ability to solely generate parallel signal streams with a passive configuration that brings significant benefits such as low‐power consumption and system simplification, both of which match the requirement of short‐range communication terminals. This chapter provides a comprehensive design guideline for an optimal OAM‐multiplexing system ranging from an antenna element and array arrangement to circuit design, from the viewpoint of both the electromagnetics and linear algebra. Finally, the feasibility of OAM multiplexing is evaluated in the presence of practical positional gaps, and also by considering the frequency dependency of the system. Finally, the chapter remarks on the critical challenges of the OAM‐multiplexing technique.