MEMS-tuneable 3D micromachined transmission line components

KTH has developed an RF MEMS technology based on an SOI (silicon on insulator) process flow, for implementing 3-dimensional micromachined transmission lines (coplanar waveguide transmission lines). Integrated MEMS actuators allow for tuning the sidewall geometries of the transmission lies, which results in tuning components with extremely low loss. All devices are characterized by being based on monocrystalline Silicon as structural material, resulting in high reliability.

The following components were implemented:

• Static zero-power consumption microswitches: RF microswitches based on reconfigurable cantilevers with interlocking hooks, which results in a mechanically bi-stable structure with zero-power consumption in both the on and the off states. External energy is only needed for the transistion between the on and the off state.
  Key publication: IEEE Transactions on Electron Devices 2009 (pdf 2.0 MB) .
• A new concept of tuneable capacitors, based on moving the sidewalls of a 3D-micromachined transmission line. Multi-stage actuators have been implemented for large tuning range, for multi-step (up to 7 steps implemented) digitally tuning in well-defined positions, and for improved linearity (over analog tuning) by electrostatic clamping. A Q of 88 at 40 GHz (!), tuning ranges of 2.5:1, high linearity of >65 dBm in all states, high reliability of >1 billion cycles were reported. Best Paper Award IEEE APMC 2010.
  Key publication: IEEE Transactions on Microwave Theory and Techniques 2013 (pdf 2.5 MB)
• A new tuneable/switchable coupler, based on simultaneously tuning the capacitance between the signal lines and the capacitances from signal line to ground, which results in very well matching impedances of the forward and backward travelling waves for a large frequency range, resulting in very large bandwidth, very high directivity, very low return loss.
  Key Publication: IEEE Transactions on Microwave Theory and Techniques 2013 (pdf 2.3 MB)

People involved

Umer Shah
Mikael Sterner
Sergey Dudorov
Joachim Oberhammer (project leader)