A High-$Q$ Millimeter-Wave Air-Lifted Cavity Resonator on Lossy Substrates

In this letter, a 3D high-quality-factor millimeter- wave cavity resonator is integrated on the lossy soda-lime glass substrate utilizing surface micromachining technologies. With a height of 300 mum, the air-lifted cavity features a measured
Q
of at least 219 at 30 GHz, demonstrating an improvement by almost an order of magnitude with respect to respective planar resonators on the same substrate. The 3D cavity is monolithically integrated on the top of the substrate, with its side walls consisting of two rows of metalized pillars, while a weak coupling excitation scheme is used to extract the quality factor. This high performance cavity can be easily integrated with other monolithic integrated circuits and planar mm-wave components in multilayer modules.