Time-Invariant and Localized Secure Reception With Sequential Multicarrier Receive-FDA

Secure communication in the physical layer (PHY) using frequency diverse array (FDA) antennas has become a prominent research topic in recent years due to the unique range–angle-dependent beam pattern exhibited by FDAs. However, the time-varying and periodic nature of the FDA beam pattern prevents the achievement of a time-invariant range–angle-focused beam pattern. Consequently, a range–angle-focused beam is only achieved at a specific time instant. Therefore, it is not yet possible to focus a beam on a specific point or area in space permanently in a time-invariant manner, due to both natural propagation mechanisms and the independent time parameter. Once a wave is transmitted, time variation cannot be altered. Thus, for the FDA beam pattern, it continues to propagate over time indefinitely. However, in the case of receiving, the time parameter is under the control of the receiver. The receiver can set the time at which the incoming wave is sampled or acquired. In this study, a cross-linear array structure called the sequential multicarrier receive FDA (SMCR-FDA) and a relevant methodology are proposed to obtain a three-dimensionally localized time-invariant range–angle-focused receive beam pattern. Additionally, several novel concepts, including the cross-linear array structure, the secure reception concept, and the positional modulation (PoM) technique, are introduced.