Design of a thin and broadband microwave absorber using double layer frequency selective surface

In this letter, a thin and broadband radar absorber structure (RAS) consisting of two frequency selective surface (FSS) layers and dielectric ceramic coating is introduced. The first FSS layer consists of square and circular metal period arrays which couple with each other, and the second layer consists of a period arrays with square patch. Ceramic coating is located below FSS layers. The effects of design parameters on microwave absorption spectroscopy of RAS were discussed, including the size and period of FSS, etc. Moreover, the effects of incidence angles for transverse electromagnetic (TE) and transverse magnetic (TM) waves on the reflection loss of RAS were also investigated. Numerical simulations indicate that the microwave absorbing properties of RAS can be improved by adjusting the unit dimensions of FSS, and reflection loss of RAS is stable from 0 to 35°. Finally, Genetic Algorithm is introduced to obtain a wide-band RAS, simulated results indicate that the absorber based on two FSS layers are better than one and without FSS. Measured reflection loss of RAS below −10 dB (over 90% absorption) is almost up to 7 GHz (7.0 GHz–8.7 GHz and 9.2 GHz–14.8 GHz) in the frequency range from 5.85 GHz to 18 GHz. The simulated results were confirmed by experimental.