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.