Reliable Systems Design using Current Boundaries

Many years ago, I started my career as an electromagnetic compatibility (EMC) educator. The reason to teach EMC were some irregularities at the company where a fresh crew of young engineers had been assigned to design and build modern 4-layer double-euro sized printed circuit boards (PCBs) using fast digital logic, to save cost and time over the expensive complicated 20+ layer, much smaller company specific PCB versions that were built before. Unfortunately, the logic devices had become much faster than their predecessors and the boards did not work! It turned out that many other companies were facing the same problems: cross-talk and transmission line effects on PCBs made the, originally independent, hardware modules interfere with each other. It was difficult to build the increasingly complex hardware. A true Hardware Crisis. A similar thing had happened to software engineering (SE) two decades earlier: the Software Crisis [1]. It had become increasingly difficult to produce software as the programs became larger. One programmer could no longer solve the problem on his own and many programmers had to work together on the task

Protection against common mode currents on cables exposed to HIRF or NEMP

Above deck, cables on naval ships are exposed to high-intensity radiated fields and nuclear electromagnetic pulse (NEMP) that may cause conducted interference and generate electromagnetic fields that exceed the immunity levels of commercially available equipment above and below deck. Exposed cables, such as open power plugs or lighting cables, are modeled and characterized both as a monopole antenna perpendicular to the deck and as a transmission line, representing a cable close to the deck. The placement of an illuminated cable close to the deck is a good protection measure for long cables at low frequencies, which includes NEMP protection. The coupled pulse from a high-intensity NEMP illumination is not expected to cause damage on electric installations. It is shown that for exposed cable length of maximum 25 cm and not placed in the line of sight of transmitters above 400 MHz, no additional protection measures are needed