Wideband absorber at X-band adopting trumpet-shaped structures

A wideband single-layer absorber at X-band adopting trumpet structures is presented. One unit of the proposed absorber is composed of a trumpet-shaped resonator loading four chip resistors, a metallic backplane and an FR-4 (ε_r = 4.4-j0.02) substrate between them. The absorption is 99% at 10.9 GHz. The full width at half maximum is 95% at 12.7 GHz (6.7-18.7 GHz). The 90% absorption bandwidth is 65% at 12.75 GHz (8.6-16.9 GHz). The size of the unit cell is 5.6 × 5.6 × 2.4 mm³. The proposed absorber is almost insensitive to polarisations of incident waves due to the symmetry of the structure. The results of EM simulation and measurements are in good agreement.