Basic Concept of Tuneable MEMS Directional Couplers for Ultra-Wideband Applications

This paper reports on area-efficient, ultrawideband, MEMS-reconfigurable directional couplers, whose coupling is tuned by mechanically changing the geometry of 3D-micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. Devices have been fabricated in an SOI RF MEMS process. Furthermore, to the best knowledge of the authors, we report for the first time on couplers which are reconfigured by changing the geometry of the ground-plane coupling, either alone or including the conventional tuning of the direct coupling between the signal lines. This results in a very uniform and well predictable performance over a very large frequency band as proven in this paper. Two different concepts are presented and compared, along with measured RF performance and actuator characterization of fabricated devices.