Optimal pulse penetration in Rocard-Powles-Debye model dielectrics using the Brillouin precursor

Abstract

When an ultrawideband electromagnetic pulse penetrates into a causally dispersive dielectric, the interrelated effects of phase dispersion and frequency dependent attenuation alter the pulse in a fundamental way that results in the appearance of precursor fields. For a dielectric described by the Rocard-Powles extension of the Debye model, the dynamical field evolution is dominated by the Brillouin precursor as the propagation depth typically exceeds a single penetration depth evaluated at the carrier frequency of the input pulse. This is because the peak amplitude in the Brillouin precursor decays only as the square root of the inverse of the propagation distance. Because of its unique nonexponential peak decay, the Brillouin precursor has direct application to foliage and ground penetrating radar, remote sensing and wireless communications in adverse environments. Of equal importance is the frequency structure of the Brillouin precursor which exhibits a complicated dependence on both the material dispersion and the input pulse characteristics. A Brillouin pulse is then defined and shown to possess near optimal (if not indeed optimal) material penetration.