3D micro-fabricated high-Q 140 GHz filter

This paper introduces a new fabrication process for the realization of cavity resonators and band pass filters, using additive micro fabrication. 3D air-filled structures with a 195 μm thickness are obtained by using successive electroplating. Thanks to this fabrication process, a 140 GHz cavity resonator with an unloaded quality factor of 511 has been fabricated. A four-pole band pass filter at 140 GHz is presented, with a 3.1% bandwidth at −3 dB, and measured 3.7 dB in-band loss. Measurements are in good agreement with HFSS simulations without any post-processing tuning.