High-Q Monolithically-Integrated Bandpass Filters Using Quarter-Spherical Resonators

A new class of monolithically-integrated and high-quality factor (Q) 3D bandpass filters (BPF) is reported. The proposed filter concept is based on compact high-Q quarter-spherical resonators that are significantly smaller than conventional spherical resonators. A mono-block connectorized integration concept is demonstrated using stereolithography apparatus (SLA) 3D printing. The operating principles of the quarter-spherical BPF concept are demonstrated through detailed eigen mode and full-wave electromagnetic simulations. For proof-of-concept demonstration purposes a second-order BPF prototype was manufactured and tested. It exhibited the following transfer function characteristics. Center frequency: 12.28 GHz, minimum in-band insertion loss 0.3 dB, effective quality factor (Qeff) of 1800 and fractional bandwidth of 2.8%