In this article, miniaturized dual-mode bandpass filters using Koch fractal-shaped slots and sinuous spurlines are proposed. Because of the space-filling property of the fractal geometry, the transmission characteristics of this filter can be adjusted by the iteration order of the Koch fractal curve. Moreover, asymmetrical sinuous spurlines are adopted to tune the degenerate modes. Compared with the conventional square-patch filters, fractal slots and sinuous spurlines can also provide more current distribution distortions which improve the electrical length and realize a compact design. Experimental data in agreement with the theoretical data verify the design methodology. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 745-747, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24167
