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In this paper, a triple-band planar absorber with high-impedance surface (HIS) is designed and fabricated. The absorber structure is composed of polyurethane foam sandwiched between a lossy sheet of frequency selective surfaces (FSS) and a perfect electric conductor. The lossy FSS possesses different resistances in a periodic composite unit as compared with typical HIS absorber. Losses in the FSS are introduced by printing the periodic composite square ring pattern on blank stickers using various resistive inks. Physical mechanism of the HIS absorbers is analyzed by equivalent circuit model and electric field distribution studies. The proposed absorber with periodic composite units offers superimposed triple-band absorption as compared with that of the single units having single- or dual-band absorption characteristics. The reflection loss measurements show that the 90% absorption bandwidth of the HIS absorber is increased by 42% by the proposed composite periodic units.

We report the design, simulation, and measurement of a magnetic-type metamaterial absorber with needlepoint-shape pattern in the microwave region. Experimental result shows that the needlepoint-shape pattern expands the absorption bandwidth of the magnetic absorber by more than 65%, which is related to the LC resonances. Different from the non-magnetic metamaterial absorber, the power loss in the proposed absorber is dominated by magnetic loss. The dielectric loss and magnetic loss are both strengthened by the metamaterial resonance. The absorber has applications in the area of eliminating microwave energy.

Resonances of the high impedance surface (HIS) absorber with periodic trapezoid-coupling pattern were studied. The theoretical, numerical, and experimental study showed that a frequency dispersion of the equivalent resistance could break the single resonance limitation. The limitation is induced by the non-dispersive feature of the equivalent resistance in simple patterned HIS absorber. Therefore, multi-resonances originated from the trapezoid-coupling pattern effectively expanded the absorption bandwidth. The proposed absorber had a thickness reduced by 41% and a −15 dB absorption bandwidth broadened by 50% compared with Salisbury screen.