David S. Dixon
Electromagnetic Compatibility Branch, Nav. Undersea Warfare Ctr., New London Detachment, New London, CT 06320
Traditionally, the electromagnetic interference (EMI) concerns of submarines have been dominated by the susceptibility of low-frequency subsystems associated with acoustic, control, and electromagnetic systems. The uniqueness of the efforts to ensure the nondegraded operation of these systems is the fact that the frequency range of the susceptible systems and the typical EMI sources overlap. Therefore, many low-frequency, low-amplitude signals can be degraded by low-frequency conducted and radiated EMI created by the power generation and distribution system. Power line rectification and switching harmonics are radiated magnetically as well as conducted along cables, shields, and ground plane components. In addition, the use of modern wideband digital systems coupled with the use of lightweight, low-cost, nonmetallic enclosures has produced an additional concern caused by the rapidly increasing radiated electric field environment. In summary, the electromagnetic environmental (E[sup 3]) concerns associated with acoustic instrumentation in very similar to the E[sup 3] concerns that are required for shipboard systems. This paper will discuss the typical EMI coupling mechanisms that will degrade the expected performance of low-frequency systems, such as audiometers, acoustic instrumentation, telephones, cabling, etc. In addition, it will discuss the EMI models that have been developed for components as well as the latest analysis and predictive EMC design techniques that have been developed to achieve cabinet and compartmental (room) compatibility.