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 λl 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 λl, 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.