Importance of non-linear processing in a sanguine receiving system

An ELF (extremely low frequeucy) communication system has been proposed for communication from land to submerged submarines. We present an analytical study of conceptual feasibility of such a system and discuss some of its properties. We find no fundamental technical reason why such a system is infeasible. The present work yields the general structure of the receiver, and estimates for the important parameters of such a system, Nonlinear processing ahead of the FSK (frequency shift keying) receiver in the submarine appears essential. Such processing greatly reduces the effects of atmospheric noise due to nearby lightning storms, and hence makes reliable operation possible at much smaller transmitter power.