Comparison of analytical descriptions for early time high-altitude electromagnetic pulse waveform (E1)

The mathematical description of High-altitude Electromagnetic Pulse (HEMP) waveform (E1) in the standard IEC 61000-2-9 is the difference of double exponentials (DEXP). The quotient of double exponentials (QEXP), p-power of double exponentials (PEXP), complementary error function with an exponential (EEXP) are introduced because DEXP has the drawback of the first derivative discontinuity at the initial time. This paper makes a comparison of four descriptions of HEMP waveform (E1) in temporal domain and frequency domain, and makes some comments.