Microfabrication of Coaxial Filter without Internal Conductor Support

摘要

In this paper, a fifth order coaxial bandpass filter with out-of-band rejection based on 3D MMFT technique is designed and presented. Short-circuited λ/2 transmission lines are adopted to construct resonators and coupled with each other through λ/4 transmission lines. Additionally, extra supporting structure is needless due to direct connection between internal and external conductor. Meanwhile, the fabrication procedure becomes simplified and more efficient. Coupling coefficients and external quality factor used in filtering design can be reached freely by adjusting positions of intersections among resonators and λ/4 transmission lines, and all the dimensions of the filter can be analytically worked out. Furthermore, attenuation poles are created on the high side of passband due to long branches of λ/2 transmission line resonators. In order to verify the feasibility of the design method, a W-band filter prototype is demonstrated and simulated, showing good agreement with analytical results.