Ultrabroadband Saline-Based Metamaterial Absorber With Near Theoretical Absorption Bandwidth Limit

Expanding the bandwidth for microwave absorption from L to Ka band with high efficiency remains challenging for broadband impedance matching. To overcome this challenge, an all-dielectric metasurface absorber composed of resin shell and saline structure is proposed to realize above 90% absorption from 0.9–40 GHz with a relative bandwidth of 191% (95.5% of theoretical limiting value) and thickness of 38 mm (115% of the minimum thickness). The extremely large bandwidth originates from coupled multiple resonance modes excited in dispersive saline structure, which can be larger with lower initial frequency by changing the geometry parameters based on the equivalent scale transformation method. Moreover, the polarization-independent and wide-angle broadband absorption are proved by both experimental and simulated results, offering practical potential application in ultrabroadband EM radiation prevention and stealth technology.