Multiuser Communication by Electromagnetic Vortex Based on Time-Modulated Array

A novel multiuser communication system based on the time-modulated circular array (TMCA) has been proposed in this letter. Different modes of electromagnetic vortex waves are generated through TMCA by the transmitter, and each mode carries a different user's signal. To realize this mode-division multiplexing method, users' messages are modulated to different intermediate frequencies beforehand. Users' signals are received also by TMCA. Because of the modulation of the TMCA, different users' signal are moved to different frequencies so they can be distinguished by bandpass filters. The proposed method implements the mode-division multiplexing with a single RF channel, which has advantages in the hardware complexity and cost. The process of transmitting and receiving is analyzed, and the drawbacks are discussed. Simulations are conducted to verify its effectiveness.