Strong scattering of radio waves by a two-layered medium with a rough boundary

Radiowave scattering by a two-layered medium with a rough boundary is studied in the Kirchhoff approximation. We consider the case of oblique incidence of waves and mean square heights of the upper boundary roughnesses, which are nonsmall compared with the wavelength λ. An analytical expression and the conditions under which P₁ turns out to be large are derived for the term P₁ of the two-frequency correlation function P = (E_m(w₁)E_n(w₂)), which is proportional to the first degree of the coefficient of reflection from the lower boundary. Such effect is shown to emerge only for the resonant frequency relation. In particular, the following resonant relationship is written for the mirror reflection direction: w_2,1(√ε-sin²θ/cosθ-1), where θ is the incidence angle and ε is the layer permittivity. Research Institute of Physics, Rostov-on-Don, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 733–743, June, 1997.