Modeling and optimization of EBG structure using response surface methodology for antenna applications

Electromagnetic Bandgap (EBG) structures are widely used with microstrip antennas for improving antenna efficiency due to their ability to suppress surface waves. To have proper control of surface wave band-gap, it is necessary to have efficient models of the dispersion characteristics of EBG in the irreducible Brillouin zone. A new methodology for optimization of a modified mushroom EBG is presented, based on Response Surface Modeling (RSM) along with Design of Experiments (DoE). Four geometrical parameters which control the surface wave band gap namely the patch width (w), gap between the patches (2g), via radius(r) and the slot width(s) are considered as independent factors and DoE is carried out using Finite Element Analysis (FEA) simulation. The lower (F1) and upper (F2) frequencies of the band gap are extracted from the dispersion characteristics. Mathematical models for F1 and F2 are developed using non-linear regression analysis. Analysis of Variance (ANOVA) is used to study the effect of EBG parameters on the stop band frequencies. The optimum EBG parameters for a stop band in 5-8 GHz frequency range are determined and are found to be: patch width, 6.48 mm, gap, 0.49 mm, via radius, 0.25 mm and slot width, 0.48 mm. The statistical model is validated by experimental results.