Microwave combline-type dual-passband filter

A dual-passband microwave filter topology based on a combline-type arrangement is presented in this paper. The described structure is made up of dual-band resonators formed by the parallel connection of two line segments grounded at one extreme and ended in a lumped capacitor at the opposite edge. The theoretical analysis of the proposed dual-band combline resonator is detailed. Moreover, guidelines for the suitable feeding and coupling of this type of resonator in dual-passband filtering applications are discussed. To validate the concept, simulation and measurement results of a manufactured filter prototype in microstrip technology are also given.