ABSTRACT
Energy transfer is the movement of radiated energy through a medium with minimum dissipation. Media sensing is the selective interaction and characterization of the media. The pivotal concept is the matching of pulse envelope, frequency, amplitude, phase, and polarization to the media characteristics. The important dielectric characteristics of the media include excitation time constants, relaxation time constants, and specific polarization requirements. Reflection, absorption, and transmission of short duration pulsed radiation depend on the transient media dielectric characteristics and the temporal characteristics of the radiation determined by the pulse envelope. Precursors are responses transmitted through media and targets due to the rapid, or ultrafast, rise and fall time of the envelope of probing pulses. The signal velocity, on the other hand, which applies to transient signals is identical to the group velocity in dispersive media, but differs from the group velocity in absorptive media.
