Dual-band filter using half wavelength resonators and dual-mode resonator

In this paper, the design and the fabrication of dual bandpass filter with controllable bandwidth is presented. Two resonators are designed to have different fundamental resonant frequencies, one for the lower passband and the other for the upper passband. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. In the upper band, a dual-mode resonator was used for adjusting bandwidth. Proposed dual band filter at passband center frequency 2.45/5.25 GHz is designed and fabricated.