A methodology towards the establishment of a statiscally credible radiated transient immunity level

An approach is required for forming a statistically credible radiated immunity level applicable to Intentional Electromagnetic Interference (IEMI) environments. IEMI and Electromagnetic Pulse (EMP) environments are typically radiated pulsed or transient phenomena, although conducted environments exist they are less common. Whilst new standards and guidance documents are available which provide test methods to generate the required immunity data for IEMI, the vast majority of electronic equipment and systems which are already in use/service are only tested for immunity to relatively benign EM environments provided within Electromagnetic Compatibility (EMC) standards. None of the commonly applied EMC standards directly address radiated transient phenomena, although there are other conducted transient tests which relate back to radiated transients. Comparing the peak radiated fields from IEMI and EMP to the immunity levels in the EMC standards (3 V/m and 10 V/m are common levels) is not only technically flawed since the modulation schemes are very different but also leads to very large estimates of separation distance between IEMI environments and potential victim systems. Primarily based on its broad applicability, frequency content and the transient nature of the test, Electrostatic Discharge (ESD) was selected for investigation to examine the radiated Electric (E) field produced during test for comparison with IEMI and EMP environments. It was found that over 87 % of the E-fields measured were 100 V/m or more, though the radiated waveform was highly variable.