Lossy Dual-Mode Bandpass Filter with Non-Uniform Q Method

This paper presents a recent investigation of dual-mode microstrip filter with non-resonating nodes and nonuniform Q lossy technique. By utilizing the dual-path and dual-mode property of dual-mode open-loop resonator, non-uniform Q distribution is deployed for passband flatness improvement. As there is no coupling between even-mode and odd-mode, the odd-mode Q-factor can be properly reduced by loading resistors over the symmetric plane of each resonators. The coupling matrix analysis are described. Design of this type of 4-pole dual-mode bandpass filter is demonstrated experimentally.