Effect of segment length modification on localized modes in Cantor bar microstrip lines

Abstract

We investigated the impurity modes in a one-dimensional fractal called Cantor bar by modifying the central and side segment lengths of the microstrip lines to control the propagation properties of the microwaves. It was confirmed, using a vector network analyzer, that there exists several localized modes in the photonic gap regions in the third-stage Cantor bar with self-similar patterns. By simulating the electrical current using the method of moments, the microwaves were found to localize in either the central segment area or in both the end areas of the fractal pattern. The length modification of the segment where the microwave is localized led to large frequency shifts of the localized modes and hardly influenced the gap region. The quality factors of the modes localized in the central area are quite affected by the length modifications of both the first and second segments.