Dual-mode dual-band bandpass filter using an new open-loop resonator

This paper presents a dual-mode dual-band microstrip bandpass filter based on an open-loop resonant structure. By introducing a square notch and slots in the resonator, one of the passband can be controlled easily. Several finite transmission zeros are realized to improve the selectivity of the proposed dual-band filter and the isolation between the two passbands. To verify the proposed filter, an experimental filter is implemented. Both the simulated and measured results are presented.