Effective-impedance tensor of a statistically rough ideally conducting surface

It is shown that, in general, a rough surface with an arbitrary spatial-angular roughness spectrum is described by an effective-impedance tensor (obtained here in the approximation of small-perturbation theory) whose nondiagonal elements are responsible for the appearance of a depolarized component in the reflected coherent signal. The phase velocity of the weakly damped surface eigenwave trapped by this surface is a function of its propagation direction, while its polarization is (in general) elliptical. A relationship is obtained between the diagonal elements (describing the coherent-reflection coefficients of vertically and horizontally polarized waves) of the impedance tensor and integrals of the scattering indicatrix of the fluctuation field, analytically continued into the region of complex scattering angles.