A Lightweight 3-D Printed $X$-Band Bandpass Filter Based on Spherical Dual-Mode Resonators

A 3-D printed fourth-order cavity bandpass filter (BPF) centered at 10 GHz and with a 3% fractional bandwidth is presented in this letter. The BPF was designed using two high-Q spherical dual-mode cavity resonators, and was fabricated using a stereolithography-based 3-D printing technique. Compared to dual-mode filters constructed by square or cylindrical resonators, the use of spherical resonator gives a wider spurious-free region. In order to fully exhibit the light weight advantage of additive manufacturing, the redundant material outside of the filter was removed. In addition, rectangular apertures were added through the cavities and waveguide walls without interrupting the surface current distributions, which further yields reduced filter weight as well as easier electroplating. Measured results of the BPF exhibit an excellent agreement with simulations.