Three dimensional micromachining for millimeter-wave circuits

Recent advances in three dimensional metal micromachining processes provide new opportunities for millimeter-wave circuit fabrication. Using these processes, enclosed transmission lines can operate to frequencies over 200 GHz, have very low crosstalk, and be routed arbitrarily. These processes also allow the integration of resonators with quality factors in excess of 500 allowing low loss filters to be fabricated at the same time as the transmission lines. Finally, the precision of the processes allows the design and realization of passive components such as cross-overs and couplers. The further development of these processes will enable highly integrated millimeter-wave systems.