1D Koch fractal electromagnetic bandgap microstrip structures with r/a ratios higher than 0.5

Abstract

A 1-D Koch fractal electromagnetic bandgap (KFEBG

Novel Compact Wide-Band EBG Structure Based on Tapered 1-D Koch Fractal Patterns

“…The introduction of 1-D Koch fractal electromagnetic band-gap (KFEBG) microstrip structures with r/a ratios higher than 0.5 increases significantly the width of the bandgap, in such a way that wide-band structures with forbidden electromagnetic propagation in a wide frequency range become possible [13]. However, their behavior in the pass-band has been found to be not optimal, due to the appearance of ripples in this region.…”

“…Thus, by combining and etching these level-1 Koch fractal hexagonal cells in the ground plane, instead of circular holes, it is possible to achieve 1-D Koch fractal electromagnetic bandgap (KFEBG) microstrip structures with r/a ratios higher than 0.5, as in Fig. 1 [13]. The design parameters of the 1-D KFEBG microstrip structure are the same as the conventional EBG structure: the distance a between the centers of the Koch fractal hexagonal cells, the radius r of the circumference in which the fractal shape is inscribed (represented by circles in dashed line in Fig.…”

“…In order to achieve the goals outlined in the previous paragraph, a periodic pattern etched in the ground plane with r/a ratios higher than 0.5 is considered [13]. It is based on Manuscript received June 30, 2011.…”

Optimisation of chirped and tapered microstrip Koch fractal electromagnetic bandgap structures for improved low‐pass filter design

“…Tapering techniques can be employed to improve performance in the low-passband, so that the filter characteristics in this frequency range can be comparable with Bragg reflectors with r/a lower than 0.5 [9,10]. We have explained the design of KFEBG filters in a previous paper [7].…”

“…KFEBGs have the remarkable advantage that they allow the realisation of structures with r/a (radius/period) ratios higher than 0.5. This has the important consequence that Bragg reflectors become low-pass filters [7,8]. However, their behaviour in the passband is not optimal, because they present a significant amount of ripple.…”