3-D Printed mm-Wave Filter Using Increased-Height DGS Resonator for Spurious Suppression

A 3-D printed quasi-elliptic waveguide bandpass filter (BPF) for 5G mm-wave application is proposed in this letter. First, by adjusting the coupling topology based on the typical 4th-order cross-coupled filter, the spurious mode below the passband is eliminated. Second, an increased-height resonator is proposed to decrease the electric coupling strength to avoid extremely small features, hence effectively reducing the sensitivity to the fabrication tolerances. Third, two types of defected ground structures (DGSs) on the filter shell are introduced to suppress two spurious modes above the passband. The stereolithography apparatus (SLA) 3-D printing with the electroplating copper plating technique is utilized to fabricate this filter for demonstration. A good agreement between simulated and experimental results verifies this design method.