Balanced Diplexers Based on Inner-Coupled Dual-Mode Structures With Intrinsic Common-Mode Suppression

In this paper, a novel topology of a balanced diplexer is proposed. It is composed of a dualmode structure and two sets of resonators at distinct frequencies. The dual-mode structure has two resonances serving for two three-pole passbands, respectively, in differential mode (DM) and an intrinsic suppression for full stopband in common mode (CM). Thus, it is perfectly suited to design a filtering network in DM, and conserve suppression in CM. In order to obtain two close DM channels and good CM suppression in the meantime, two inner resonators are coupled together via a specific coupling scheme with intrinsic CM suppression to construct it. Two balanced diplexers utilizing the proposed dual-mode structures with varied configurations are proposed, designed, and fabricated, which have well verified the proposed diplexer topology and a design method.