Active frequency tuning for micro resonators by localized thermal stressing effects

Abstract

A method of active frequency tuning on comb-shape micro resonators has been successfully demonstrated by means of localized stressing effects. A mechanical beam structure that can be resistively heated to generate thermal stress, is integrated as part of the comb-shape micro resonator for frequency tuning. Experimentally, a frequency change up to 6.5% is measured for resonators with a central frequency at around 31 kHz. The required tuning power is 25 mW in the form of localized Joule heating. Analytically, both a one-dimensional electrothermal model and a dynamic model are established to characterize the electrical, thermal and frequency responses of active frequency tuning. The simulation results of frequency spectrum are consistent with experimental measurements. A reliability test, conducted for more than 300 million cycles under 6.5% of frequency tuning range, reveals no observable material damages on the micro resonator. This scheme enables active frequency tuning under low power consumption and independent of the input/output function of a micro resonator. As such, it has potential applications to resonator-based MEMS devices, such as rate gyroscopes and microelectromechanical filters.