Broadband Low-Profile Frequency Selective Rasorber Using Ultraminiaturized Metal-Graphene Structure

In this letter, a broadband and low-profile frequency selective rasorber with an ultraminiaturized metal-graphene structure is proposed. The rasorber is composed of two cascaded layers separated by an air spacer, a top lossy layer and a bottom bandpass layer. By supplying four branches of multiple vias connected stubs across a circular graphene film in the lossy layer, extra inductance and capacitance effects are introduced while guaranteeing the impedance match with the free space at the low frequency range. As a result, a broad absorption bandwidth is ensured from 1.96 to 10.2 GHz with the thickness of only 0.076 λ_l at the lowest absorption frequency, and the passband is at 12.83 GHz with the insertion loss of 0.23 dB. Besides, a miniaturized unit is achieved with the period of 0.039 λ_l , and the oblique angle incidence response is up to 45° for TE and TM modes. To validate the design, a prototype is fabricated and measured, and the screen-printing process of graphene resistive film as omnidirectional resistance is adopted to further reduce the profile. The measured results agree well with the simulation.