Tunable thin radar absorber using artificial magnetic ground plane with variable backplane

Experimental verification is provided of the frequency tuning capability of a low-profile radar absorber material based on the high impedance surface principle. The absorber consists of an artificial magnetic ground plane with surface mount resistors interconnecting a textured surface of square patches. It is shown that by displacing the ground plane of the textured surface substrate from 0 to 0.04 lambda(0) better than -15 dB return loss, -42 dB best case, from 3.55 to 5.47 GHz can be obtained when the surface is illuminated by a linearly polarised signal at normal incidence to the surface. In addition, the response of the surface in terms of its axial ratio performance under circular polarised signal excitation at normal incidence is investigated for a fixed ground displacement.