Modeling and application of 2D photonic band gap structures

Photonic band gap (PBG) structures have originally been explored in electro-optics. During the last five years, 2D planar PBG circuits have also been used at microwave frequencies. PBG structures behave as high impedance surfaces and suppress surface waves in one or more frequency ranges. Until now, these circuits have only been reliably modeled by numerical methods. A new equivalent circuit model is proposed. The model is based on the transmission line theory and periodic structures. The model is simple, but limited as it only allows for determination of the stop bands for the two principal directions of wave propagation. Nevertheless, it is a useful first step in the design of PBG structures. If this model is coupled with a simple numerical modeling using the FDTD method, it predicts the complete characteristics of the structure. The proposed analytical and numerical modeling is applied to improve the performance of a broadband circularly polarized patch antenna.