Frequency Selective Rasorber and Reflector With Two-Sided Absorption Bands

A design to achieve frequency-selective rasorber (FSR) and reflector with two-sided absorption bands is proposed. The theoretical analysis and the calculation method for the structure parameters are presented by utilizing the equivalent circuit model. The reflector and the rasorber are designed in simple 2-D structures, consisting of only one layer of resistive sheet and a pure ground or a bandpass frequency-selective surface, respectively. Based on the analysis of the condition for realizing two-sided absorption, we found that the parameters of each element in the resistive sheet are correlative and proportional to each other. The calculation method of actual physical dimensions of the proposed structure is provided, so the element sizes of unit cell structure can be calculated and designed to approximate the desired values. Hence, based on these proposed methods, the perfect two-sided absorption FSR or reflector can be realized directly when the deduced relationship of the parameters is satisfied. Therefore, the approach of impedance matching becomes much easier. The simulation results show the two wideband absorption bands located above and beneath the reflection/transmission band. An FSR and a reflector are designed, fabricated, and measured. The measurement results match well with the simulation results and verify the designing principle. The FSR realizes the two-sided absorption bands at 2.1–5.1 and 11.9–17.5 GHz and a transmission band at 9.7 GHz. The reflector shows a wide reflective bandwidth and two wide absorption bands at 2.8–6.5 and 12–17.4 GHz.