Calculation of the dispersion diagram for planar electromagnetic bandgap structures

This paper presents a numerical technique for the accurate calculation of the dispersion diagram of planar electromagnetic bandgap structures. The method is based on coupling the energy of an incident plane-wave in a perturbed structure, which has the same resonance frequencies, and studying the reflection spectra form the structure. In this method, solving the dispersion problem is transformed to solving a diffraction problem accompanied with finding minima of the spectrum. The computation cost to perform this method is so low that a fine scan of the frequencies is possible and highly accurate results can be obtained. Some comparisons with previously published results are also presented and show the importance of a very fine scan for drawing the band diagram.