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.

1. Introduction

Frequency-selective surfaces (FSSs) have been studied over the past five decades [1],[2]. They have evolved from simple designs to the complex geometries known today. This evolution has been mainly driven by the increasingly stringent performance requirements of recent applications. Progress on frequency-selective surfaces has also been motivated by the significant improvements in analysis methods, computational power, and fabrication technology. Based on these, a number of interesting designs have recently been reported as three-dimensional (3-D) frequency-selective structures [3]–[12], which are fundamentally different from the conventional frequency-selective surfaces. Three-dimensional frequency-selective structures exhibit many superior performance features, and they hence deserve further research towards the realization of more practical applications. In this paper, we present three-dimensional frequency-selective structures as a distinct and more general class of frequency-selective surfaces. We review the current state of the research, and propose future explorations of three-dimensional frequency-selective structures.