Design of Balun Bandpass Filter With Ceramic Loaded Triangular Resonator

This paper presents a balun bandpass filter (BBF) with ceramic loaded triangular resonator (CTR) using spatial coupling mechanism. The two triangular dielectric resonators are arranged to realize the coupling between them. The resonator operates in TM11-mode and realizes balanced output by distributing the position of ports reasonably. This design also uses half-cut technology to realize balanced output and reduce the size of structure. In this design, the substrate's existence or not will not affect the performance of this balun but the common ground plane will affect the resonant frequency of resonator. This structure also shows good rejection out of band. The first resonant mode out of band appears at twice the working frequency.