Prediction of Aircraft Transient Level (ATL) by simulation and comparison to frequency-domain measurements using the minimum phase algorithm

This paper demonstrates the prediction of Aircraft Transient Level (ATL) by simulation, compared to measurements in frequency domain. Dealing with the design of a new aircraft, numerical simulation is nowadays used to reduce the EMC requirement margins for equipment qualification and aircraft certification. An advanced simulation approach is demonstrated in this paper to reduce simulation time and effort by using a Gaussian excitation pulse in time domain. The prediction of the indirect Lightning Electromagnetic Pulse (LEMP) and the Nuclear Electromagnetic Pulse (NEMP) threat by convolution is possible in post processing. The prediction of ATL from scalar measurements in the frequency domain by reconstruction of the unknown phase under minimum phase assumption is also shown. Theoretical and practical examples demonstrate the steps of the minimum phase algorithm (MPA) and the prediction of currents or voltages in time domain from measurements of the magnitude in frequency domain. The paper concludes with the combination of the advanced simulation approach and the phase reconstruction by MPA. This smart combination reduces the effort for measurements to frequency domain magnitudes only which can then be converted to ATL by using MPA. This process has grown to a dominant reduction factor for ATL requirement prediction.