Broad-Passband Rasorber With Ultrawideband Absorption Incorporating Graphene-Based Resistive Films and Via-Based Winding Inductors

A multilayer frequency-selective rasorber (FSR) with both broad passband and ultrawide absorption band is proposed in this letter, utilizing graphene-based films and via-based winding inductors. It is constructed by two lossy layers with a broad passband and a third-order frequency selective surface (FSS) placed at the bottom. The unit cell of the top lossy layer is composed of a square graphene film at the center and four arms of via-based winding inductors terminated with a gap capacitor, which extends the absorption band at low-frequency and broadens the transmission band at medium and high frequencies. The second lossy layer contains a square graphene film at the center and four strip lines connected to spiral inductors with parasitic capacitance, which enables absorption at high-frequencies while maintaining transmission at low and medium frequencies. The bottom FSS consists of two square patches coupled through a square ring slot for third-order wideband transmission and acts as the ground of the lossy layers. The proposed FSR achieves ultrawideband impedance matching from 1.56 GHz to 18 GHz (168%), with a passband range of 7.15 GHz to 12.4 GHz (54%) and a minimum insertion loss of 0.56 dB.