Comparison between high altitude EMP and high power electromagnetic effects on equipment and systems

The electromagnetic effects of a High Altitude EMP has been a threat for communications and installations which has been largely studied and documented between 1960 and 1990. During the last decade of the 20(th) century, a new kind of electromagnetic field representing a new threat, has been developed, the High Power Electromagnetic (HPEM) field. The paper will discuss and compare the main features of these two kind of electromagnetic fields, like the spatial coverage, the frequency spectrum, the time-domain behavior and will briefly compare the protection measures which can be taken against these two kind of electromagnetic effects.