Design of Dual-Absorptive-Bands Frequency Selective Rasorber With Minkowski Loop Arrays

Abstract

A dual-absorptive-bands frequency selective rasorber with Minkowski loop arrays is proposed in this letter, which has a passband and two absorptive bands on either side of the passband. In our design, this structure consists of a lossy layer and a frequency selective surface (FSS) layer. These two layers are isolated by air. The lossy layer is composed of Minkowski loop arrays with branches and resistors loaded on the loop, and the FSS layer is a metallic array composed of grids and square loops. Based on the equivalent circuit model and the surface current distribution, the electromagnetic characteristics of the frequency selective rasorber (FSR) are studied, and the simulation results show that the structure has a passband with an insertion loss of 0.36 dB at 7.65 GHz. Additionally, the fractional bandwidth of $-$ 10 dB reflection reaches up to 119.3% under normal incidence and has good stability under oblique incidence. Furthermore, the FSR is fabricated and measured to verify our design and demonstrates good agreement with the simulations.