DC-to-RF MEMS Converter

L. Chen, P. Pai, M. Tabib-Azar
University of Utah, US

Keywords: MEMS, DC, RF, oscillator, tunnelling current

Summary:

A novel MEMS device that directly converts dc signal to RF signal was designed and realized. The device is composed of a bridge that can be laterally displaced electrostatically by applying dc voltage to a nearby electrode. Charges will be neutralized with tunnelling current discharging when the bridge moves very close to the electrode. The oscillation cycle is stable provided that time constants associated with electrode-bridge discharging, electrode charging and bridge motion are carefully selected. Microfabricated TiW bridges were used to show feasibility of the design. Switching characteristics were measured, which showed tunnelling current discharging induced bridge oscillations. The micro-bridges were tested in a DC-to-RF testing circuit, with measured output signal spectra showing the oscillations when Vdc is large enough for bridge actuation.