A novel microstrip bandpass filter using triangular open-loop resonators

This paper proposes a new four-pole bandpass filter based on the triangular open-loop resonators structure. The full-wave simulator IE3D has been employed for designing the resonators, and calculating the related coupling coefficients of each resonator pair. The proposed filter circuit has been then finally constructed. It has been found that experimental results of the filter agree very well with simulation expectation. This filter also provides an improved selectivity characteristic with narrow bandwidth and compact size compared with the conventional resonator filters.