A novel miniature dual-mode filter based on modified sierpinski fractal resonator

Miniaturization of the resonator is significant for a compact filter. To meet such requirement, several techniques, for instance, using the high permittivity material or using the step-impedance resonator with multiple resonant modes, can be used. Dual-mode resonators have advantageous features for the bandpass pass filter (BPF) design, such as excellent unloaded Q values, size compactness, low radiation loss and ease of design because transmission-line theory and design tools can easily be employed. Therefore, in this paper, we present a novel miniature dual-mode BPF based on the fractal geometry resonator. The proposed fractal geometry is introduced from the Sierpinski square and described by the generated method. A 3rd order Sierpinski square is adopted as the resonator structure since it has a high quality factor, suitable for the proposed dual mode BPF design. The design procedure is discussed in the following. A dual mode BPF at 2.4 GHz is characterized by using the full-wave electromagnetic (EM) simulator IE3D and verified by the experimented results.