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We present a time-coding reconfigurable intelligent surface (RIS) enabled spread-spectrum secure wireless communication system. The time-coding spread-spectrum RIS is realized by altering the RIS between the two states of a perfect electrical conductor (PEC) and perfect magnetic conductor (PMC), according to a pseudo-random time sequence, respectively. This spectrum spreading function of the time-coding RIS can be simply applied to the secure wireless communication systems, providing a low-cost, easy-implementation encrypting architecture with the two key features of interception prevention and interference suppression. These two features together with the overall spread-spectrum secure wireless communication system are demonstrated by both theoretical analysis and experimental results using a designed 8 × 8 time-coding RIS.
Wang et al. (Mon,) studied this question.