A Compact Triple Band BSF Design Based on Minkowski Fractal Geometry

In this paper, Minkowski fractal based open-loop resonators are adopted to design triple band microstrip bandstop filters (BSFs). The suggested filter structures are primarily based on that of the conventional open-loop rectangular microstrip resonators. The resonators of the proposed BSF structure are made in the form of Minkowski fractal geometry with different iteration levels. Many filter structures have been modeled, and their performances have been evaluated using the commercially available EM simulator, Sonnet. Each of the modeled filter structures contains two pairs of open loop fractal based resonators with different iteration levels. The lower frequency bandstop performance is attributed to the resonators with higher iteration level while the higher frequency bandstop performance is due to the resonators with lower iteration levels. Simulation results for the proposed microstrip filters have confirmed the validity to realize compact multiband narrow-stopband microstrip filters. Measured results of a fabricated filter prototype are found to be in reasonable agreement with those predicted by numerical computation. The results presented show that the proposed fractal based resonators can be used to construct compact multiband filters with narrow stopbands