Coupled Resonator Band-Reject Filters with All Positive Inter-Resonator Couplings

This work demonstrates the synthesis of band-reject filters comprising cascaded coupled resonator configurations exhibiting all positive inter-resonator couplings. Filters with all positive couplings are easier to manufacture and are less susceptible to temperature & vibration requirements. Several synthesized filter networks are illustrated proving the proposed concept together with the EM implementation of an 8-resonator band-reject filter implemented utilizing coaxial resonators.