A high impedance surface (HIS) consisting of metallic square patches electrically connected one to each other with resistors is shown. Tunability of the absorption factor is achieved by the resistor value. The absorbing band of the loaded HIS is determined by the phase of the signal reflected by this structure. The main contribution of the paper is to demonstrate the absorption behavior over a wide range of incidence angle for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Using an equivalent circuit the resistor effect is investigated. It is shown that at resonance, the judicious choice of the resistor may lead to a significant absorption. The use of a waveguide simulator to characterize the performance of the loaded HIS is investigated. These methods have been used to design an ultra-thin absorber about λ8.4 GHz/35 thick.
