Analysis and design of frequency selective absorbers

Summary form only given. Frequency selective surfaces (FSSs) have found wide applications due to their frequency filtering characteristics, such as a radome employing the passband characteristic of an FSS and a reflector using the stopband characteristic of an FSS. However, an FSS usually generate strong reflection at frequencies in its stopband, as shown in Fig. 1(a). Since the strong reflection in the stopband is should be reduced for certain applications, a new structure, named frequency selective absorber (FSA), has been proposed to achieve this objective. In order to absorb the reflected signals in the stopband, an FSA is usually realized by introducing absorbing elements in the FSS. Fig. 1(b) illustrates the performance of an FSA, where one transmission band and two absorption bands at both sides of the transmission band can be observed. Most of the reported FSAs are based on the combination of Salisbury/Jaumann absorbers and conventional FSSs, which are multilayered structures. Single or multiple lossy layers are placed above a metallic FSS layer with dielectric spacers between them. In this work, a new design methodology for FSAs is presented. First, we conduct a brief review of existing FSA designs with a focus on understanding their operating principles and identifying their advantages and limitations. After that, a generalized equivalent circuit model is proposed to explain the operating principle of two new FSA structures. Finally, several design examples of FSA based on 2D and 3-D FSSs are presented and discussed.