In this paper, the concept and recent development of exploiting frequency diverse array (FDA) and its variants for the physical-layer wireless security have been revisited and carefully examined. Following rigorous analytical derivation and illustrative simulations, the authors argue that the investigations performed in some recent works did not reveal one critical issue facing the real-world applications, and system models established and used before were based on an unrealistic assumption, i.e. that the legitimate and eavesdropping users at different ranges sample the signal waveforms at the same time instant. This misunderstanding results in conclusions that are misleading. The authors aim to take the first step to divert research efforts and rectify the previous problematic analyses. The authors prove that the FDA cannot secure a free-space wireless transmission in range domain, because the previously claimed ‘secure reception region’ propagates in range domain as time elapses.
