Electromagnetic band gap (EBG) structures in antenna engineering: From fundamentals to recent advances

Periodic structures are abundant in nature, which have fascinated artists and scientists alike. When they interact with electromagnetic waves, exciting phenomena appear and amazing features result. In particular, characteristics such as frequency stop bands, pass bands, and band gaps could be identified. Reviewing the literature, one observes that various terminologies have been used depending on the domain of the applications. These applications are seen in filter designs, gratings, frequency selective surfaces (FSS), photonic crystals and photonic band-gaps (PBG), etc. We classify them under the broad terminology of "electromagnetic band gap (EBG)" structures. EBG structures have provided promising paradigm for novel antenna designs. Due to the complexity of the EBG structures, it is usually difficult to characterize them through purely analytical methods. Instead, full wave simulators that are based on advanced numerical methods have been used in EBG analysis. Dispersion diagram, surface impedance, and reflection phase features are revealed for different EBG structures. These analysis tools have been integrated with modern optimization techniques such as genetic algorithms and particle swarm optimization to synthesis unique EBG structures. The applications of EBG structures in antenna designs have become a thrilling topic for antenna scientists and engineers. This is the central focus of this presentation by initially reviewing the fundamentals and then demonstrating recent advances. Utilizing several representative antenna examples it will be demonstrated that proper utilizations of EBG structures could enhance the performance of low profile antennas; however, considerable care must be exercised to fully appreciate their advantages and disadvantages.