4-D Retro-Directive Antenna Arrays for Secure Communication Based on Improved Directional Modulation

The 4-D antenna arrays combined with retro-directive technique based on an improved directional modulation technique are proposed for physical layer secure communications. The optimized time sequence is designed, which improves the security performance of 4-D antenna arrays greatly. By introducing the retro-directive technique into 4-D antenna arrays, secure communication can be realized without any prior knowledge of the legitimate receiver's location. Moreover, the proposed approach avoids both the heavy computational burden and complex hardware implementation, benefiting from the inherent advantages of retro-directive antenna arrays in automatic target tracking. The numerical and experimental results demonstrate that the proposed transmitter architecture of 4-D retro-directive arrays provides an effective way to achieve wireless secure communication in the scenario with multiple legitimate receivers and under multipath environment.