3-D-Printed Diplexer Using “ $\Gamma$ ”-Shaped Coaxial Resonator for Realization of Electric and Magnetic Coupling

This article presents a
$\Gamma$
-shaped coaxial resonator (
$\Gamma$
SCR), which is purposely designed to effectively control the electric and magnetic coupling. Traditional electric and magnetic coupling of coaxial resonator encounters complicated coupling structure with coupling windows. Especially electric coupling always requires extra metal probe structure to provide enough electric coupling strength. The proposed
$\Gamma$
SCR provides a solution of simple structure and easy design approach of filter and diplexer. This increases the design flexibility and size reduction by only arranging the orientations of the resonators to realize electric and magnetic coupling without coupling windows or extra coupling structure. This article provides a comprehensive description of the coupling mechanism and designs transmission zeros (TZs) at prescribed frequencies. It is noteworthy that a cascaded triplet (CT) filter using our proposed method has 73.1
$\%$
size reduction when compared with traditional CT. To demonstrate this concept, a fifth-order bandpass filter (BPF) and a third-order diplexer were designed and manufactured using additive manufacturing 3-D printing techniques. The tested results agreed well with the simulated ones, validating the proposed approach.