A High Q-factor Metamaterial Absorber and Its Refractive Index Sensing Characteristics

High quality (<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>)-factor metamaterial absorbers are an emerging technology, which can be used in refractive index sensing for dielectric coating and in radar cross Section (RCS) reduction for concealment of an object. Nevertheless, angular-sensitive or the required complex structure hampered its application. Here, a metamaterial absorber based on a simple inverted-cross-star (ICS) structure with high <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor operating within microwave frequencies is demonstrated. The metamaterial absorber is composed of ICS metallic pattern and a metal ground plane on the sides of a Rogers RT5880 dielectric slab with a thickness of 0.127 mm. The excellent angular insensitivity for both TE and TM polarizations of the proposed metamaterial absorber is demonstrated by Finite Integeral Technology (FIT) numerical simulation, i.e., the absorptivity is about 85% for TE polarization and more than 99% for TM polarization under the incident angle as wide as 70°. The RCS of a manufactured prototype is measured in an anechoic chamber. In addition, the potential application of the proposed metamaterial absorber in refractive index sensing is also studied. This proposed prototype, with the advantages of high <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor, structural simplicity, small thickness, angular- and polarization-insensitiveness, and frequency flexibility, has potential application in the field of antennas with RCS reduction and metamaterial sensing.