Revisiting the Calculation of the Early Time HEMP Conducted Environment

The early time high altitude electromagnetic pulse conducted environment calculation is revisited by using the transmission line (TL) theory and including high-frequency corrections that were not present in the earlier studies. Waveform salient parameters, such as the current peak, rise time, and pulsewidth, are studied as a function of a number of parameters involved in the calculation. The obtained cumulative distribution functions of the parameter probabilities are discussed and compared with the existing standards for the HEMP protection. The high-frequency correction to the TL model results in a decrease of the current amplitudes of 15–20%. For the highest currents, rise times in the range of 25 ns are obtained. A less significant impact was found in the calculation of the pulsewidth, which was increased to about 150 ns.