Design and implementation of a multi triangular microstrip resonator passband filter based on mixed coupling

This article presents the method of designing cascade trisection (CT) filter using triangular resonators instead of quadrangle resonators in previous works. The possibility of adjusting electric and magnetic coupling results in realization of transmission zeroes very close to pass-band region. For two coupled resonators, the coupled sides with the maximum magnetic field are combined with their open gaps, creating mixed coupling. By adjusting the distances between resonators and the positions of open gaps in a mixed coupled filter, the coupling coefficients can be changed, and controllable transmission zeros can be produced in the lower or upper stopband. Simulation results show that this filter has excellent performance with high rejection along with the possibility of realizing very close to pass-band transmission zeros with the aim of mixed coupling between resonators.