A Vector Modulation Approach for Secure Communications Based on 4-D Antenna Arrays

A vector modulation approach based on 4-D antenna arrays is proposed for the directional modulation (DM) of physical-layer secure communication. This approach utilizes the time modulation function of 4-D arrays to generate identifiable vector information in desired directions while the vector information is distorted in undesired directions, thus increasing the transmission security as compared to previously reported DM schemes. The mutual coupling of antenna elements is taken into consideration for the accurate analysis of various scenarios. Moreover, in order to achieve multiuser secure communication and improve their security capability simultaneously, the dual-channel DM and dynamic DM are separately proposed and only high-speed radio frequency (RF) modulation switches are needed. Numerical and experimental results are presented for the demonstration of the capability and superiority of the proposed physical-layer secure communication based on 4-D arrays.