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.