SLM Manufacturing of a Novel Highly Compact Quarter-Sphere Resonator Based Filter

This letter presents a highly compact waveguide-based bandpass filter, which can be used for high-power transmission for satellite communications. The filter consists of a quarter spherical resonator, whose higher-order modes are restricted by introducing four tool cavities. By integrating four spherical resonators into a sphere, a highly compact fourth-order filter with wideband and good out-of-the-band rejection is obtained, whose geometric size is $1.24\lambda \times 1.24\lambda \times 1.24\lambda$. The spherical filter with complex internal structure is manufactured by using the selective laser melting (SLM) technology, which is a 3D printing technique with a low cost-to-complexity ratio. Finally, measurement results validate the good performance and obvious miniaturization of the developed filter.