An overview of three-dimensional frequency-selective structures

Three-dimensional (3-D) frequency-selective structures are a recent development that exhibit superior filtering responses compared to conventional two-dimensional (2-D) frequency-selective surfaces. A three-dimensional frequency-selective structure typically comprises a two-dimensional periodic array of multimode cavities the modes of which and the coupling of which with air can be controlled to obtain a desired frequency response. Based on their distinct configuration, we seek to classify them as a separate class of high-performance frequency-selective structures, and to highlight their unique features in this paper. We also present a review of recent advances in three-dimensional frequency-selective structures, and suggest a number of related research topics for future exploration.