A resonance dynamical approach to faster, more reliable micromechanical switches

The resonance and nonlinear dynamical properties of micromechanical structures have been harnessed to demonstrate an impacting micromechanical switch with substantially higher switching speed, better reliability (even under hot switching), and lower actuation voltage, all by substantial factors, over conventional RF MEMS switches. The particular resoswitch implementation demonstrated in this work comprises a wine-glass mode disk resonator, driven hard via a 2.5V amplitude ac voltage at its 61-MHz resonance frequency so that it impacts electrodes along an orthogonal switch axis, thereby closing a switch connecting a signal through switch axis electrodes. The 61-MHz operating frequency corresponds to a switching period of 16ns with an effective rise time of ~4ns, which is more than 50 times faster than the mus-range switching speeds of the fastest conventional (non-resonant) RF MEMS switches. Furthermore, with the signal on during switching, a capacitive version of the switch has hot switched for more than 16.5 trillion cycles without failure, which is substantially more than the 100 billion cycles normally posted by conventional RF MEMS switches. The reliability of the present resoswitch benefits from the high stiffness of its actuating disk resonator, which provides a large restoring force with which to overcome sticking forces; and from the energy stored via resonance vibration that provides a momentum that further increases the effective restoring force. Resonance operation in turn allows the actuation voltage amplitude to be a mere 2.5V, despite the large spring restoring force. Such mechanically resonant switches (dubbed ldquoresoswitchesrdquo) used in place of the switching transistors in switched-mode power converters and power amplifiers stand to greatly enhance efficiencies by allowing the use of much higher power supply voltages than allowable by transistors.