Effects of random rough surface on absorption by conductors at microwave frequencies

The effects of a random rough surface on the absorption by a metallic surface at microwave frequencies are analyzed by using two methods: the analytic small perturbation method and the numerical method of moments method. The results show significant difference between absorption of a rough surface and that of a smooth surface. The absorption depends on the root mean square height, correlation length, and correlation function of the random rough surface. The similarities with and differences from Morgan´s classical result and the Hammerstad and Bekkadal formula are discussed. It is shown that for multiscale rough surfaces, saturation of absorption does not occur, or occurs at much higher frequencies.