3D Printed Compact High-Q_u Inline Mixed Coupling Filter Based on Deformed Square Coaxial Resonator

Abstract

This paper presents a kind of novel deformed square coaxial resonator (DSCR) that exhibits a more compact size and maintains high unloaded (Q_u) factors. Specifically, compared with the graded dumbbell coaxial resonator (GDCR), the proposed resonator can achieve an 11% reduction in volume and an 11% increase in Q_u values. Furthermore, through reserving a small section surface, the proposed resonator can be applied to design inline mixed coupling filters with conventional metal coupling windows. The mixed coupling coefficients can be adjusted simply by changing the width of the coupling window. To validate the advantage, a four-pole inline mixed coupling filter was designed. For rapid demonstration, the 3D metal printing technology was adopted to print the filter. The printing tolerance is pretty good, and the measured results agreed well with the simulated results.