EMC Design for a Ship Borne Real Time Embedded System

Most real time embedded hardware systems are made to operate under harsh electromagnetic interference (EMI) conditions. The problem is more severe if the system is operating in a marine environment where it co-exists with several simultaneous sources of emission such as communication equipments, auxiliary antennas, Satellite Communication (SATCOM) links etc used in the ship. Therefore, it is imperative that the system must be resilient to the EMI happening in the environment, and at the same time it should not be a source of EMI for other systems operating in its vicinity. One way to ensure this is to design the system with adequate diligence so that the system passes the Conducted Emission (CE), Radiated Emission (RE), Conducted Susceptibility (CS) and Radiated Susceptibility (RS) Tests as specified in MIL-STD-461G. We present in this paper a case study for the design of such a real time embedded system with proper Grounding, Shielding and Bonding Schemes implemented in the electromagnetic compatibility (EMC) design. Additional features like Galvanic isolation in I/O Translation board is present for protection against transients. Improved protection by way of EMI gaskets, 360 degree shielding on the system cables, separation of isolated ground from chassis ground, separate shield for each Processing Board (PCB), using isolated power supply, usage of proper Transient Voltage Suppressor (TVS) diodes and EMI Filters, adequate number of ground pins on every connector, usage of differential RS-422 signals are the prominent features which has offered ruggedness to this system from EMI. The real time embedded hardware system has successfully passed the EMI EMC tests to which the unit was subjected.