Application of the coupled-wave method to ground penetration radar

A model problem of impulse radio probing of horizontally-layered dielectric half-space is considered. The receiver antenna registers partial reflections from the interfaces and gradients of the subsurface medium. A time-domain version of the coupled-wave method (two-wave WKB approximation) is developed to describe the reflected signal. The approximate solution, constructed in a closed form, conforms to the exact solutions, radically speeds up the calculations, and explains the protracted reflected pulses observed in the lower part of the GPR frequency band.