Generating, multiplexing/demultiplexing and receiving the orbital angular momentum of radio frequency signals using an optical true time delay unit

A scheme for generating and/or eliminating the orbital angular momentum (OAM) of radio frequency (RF) signals based on the true time delay (OTTD) system is proposed for the first time. The central structure of the scheme is the OTTD unit connected with a circular antenna array which can provide or compensate the helical phase variation precisely, and therefore can form or eliminate the OAM radio beam with different states (the topological charges) conveniently. Other prominent advantages of the proposed system are support for multiplexing/demultiplexing the OAM states carried on the RF signals with the same frequency and support for exchange of the OAM states carried on two RF signals. This can be regarded as the analog of various other multiplexing technologies for increasing the capacity and efficiency in radio communication systems. Theoretical analysis and numerical simulations demonstrate the feasibility of the proposed scheme. (paper)