Novel compact wide-band EBG structure based on tapered 1-D koch fractal patterns

Abstract

This letter presents a novel electromagnetic bandgap (EBG) structure in microstrip technology based on nonuniform one-dimensional (1-D) Koch fractal patterns whose dimensions and period are modulated by a tapering function that significantly improves the width of the bandgap. This wide bandgap is achieved by maintaining the r/a (radius to period) ratio of the Koch fractal patterns larger than 0.5 in the whole structure. In the pass-band region, an improved flat response is obtained by tapering the dimensions of the Koch fractal patterns etched in the ground plane, together with the width of the microstrip line, with a Kaiser distribution which also modulates the periodicity of the fractals. A major consequence of this modulation of the periodicity of the pattern is that this structure is much more compact than a uniform conventional one.