Microstrip filter with H-shaped fractal

Abstract

A microstrip filter with an H-shaped fractal pattern is proposed. It is found that the microstrip filter has multiple gaps and passbands for electromagnetic waves over an ultrawide frequency range, and the band gaps shift to lower frequencies with the increasing first level length of the fractal structure, showing tunable band gap properties. Experimental observations are in good agreement with simulations by the finite-difference-time-domain method. A prototype of the microstrip filter was fabricated by conventional low-cost printed circuit board techniques.