Spectrum-division analysis of precursor fields propagating in dispersive media

This paper presents a new approach called spectrum-division analysis of electromagnetic precursor field, a wave propagation phenomenon when electromagnetic (EM) waves incident on an absorptive and dispersive medium, which might be exploited in penetration radar imagery. Compared with classical asymptotic techniques of precursor analysis, the proposed method directly derives precursors from the Fourier spectrum with a clear physical picture. By defining the gravity centre of the wave packet, the mechanisms of precursor field and the non-exponential decay are explained. Numerical experiments are made to demonstrate the usefulness of the proposed approach.