A new miniaturized fractal bandpass filter based on dual-mode microstrip square ring resonator

Abstract

A novel fractal dual-mode microstrip bandpass filter design has been introduced in an attempt to produce filters with highly miniaturized size for modern wireless applications. The filter structure has been generated based on the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> iteration Minkowski-like pre-fractal geometry, using the conventional dual-mode square ring resonator as the initiator in the fractal generation process. The space-filling property, self-similarity and the diagonal symmetry of the structures corresponding to the successive iteration levels of this fractal geometry have found to produce reduced size filter structures with accepted performance. The bandpass filter structure produced by the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> iteration of this fractal geometry can be considered as a novel design with adequate performance. This design structure possesses a size reduction of about 72% compared with the conventional dualmode square ring resonator operating at the same frequency and using the same substrate material. In addition, the new design technique seems reliable, since it provides the filter designers with more degree of freedom and further size reduction as compared with those reported in the literatures.