High Q factor curved X shaped Ultra-thin Polarization Insensitive High Angular Stable microwave absorber as Refractive Index Sensor

This paper presents an ultra- thin microwave absorber with 0.51mm (0.008 λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</inf>) thick substrate for sensing of Refractive Index. The proposed absorber have metallic structure with curved X shaped structure at the center along with a slotted square ring resonator at the edges on top of Roger’s RT5880 as dielectric substrate along with copper at the back. The unit cell is 0.187 x 0.187 ${\lambda _{\text{g}}}^{\text{2}}$ and 0.008 λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</inf> thick. The absorptivity of 99.1% at a frequency of 7.19 GHz is achieved. It exhibits a half maximum bandwidth of 33 MHz (7.17-7.20 GHz). The absorber is angular stable to incidence angles till 60° for transverse-magnetic (TM) and transverse-electric (TE) modes. It is also polarization insensitive. The proposed microwave absorber has a high Q factor of 79.88, which can find potential application as a refractive index sensor.