Absorptive frequency-selective reflection and transmission structures

Tailoring methodology is proposed in this communication to achieve an arbitrary frequency response within a wide absorption band. An ultrawideband (UWB) absorber utilizing multiple resonances in the unit cell of 3-D frequency-selective structure is utilized as the textile for the proposed designs. Two types are proposed: one is absorptive frequency-selective reflection structure (AFSR) and the other is absorptive frequency-selective transmission structure (AFST). These structures have reflection/transmission band within a wide absorption band. Two prototypes are designed, fabricated, and measured to validate the proposed methodology. The first one is an UWB absorber with 155.7% absorption bandwidth from 1.8 to 14.4 GHz with structure's thickness of 0.12 λ {0} at the lowest absorption frequency. The second one is an AFST with wide absorption bands at both sides of its transmission window. It exhibits 54% and 76% for the lower and upper absorption bands, respectively, with 1 dB insertion loss in the transmission window. A good agreement is achieved between simulation and measured results.