Suppression of the A-f-mediated noise at the top bifurcation point in a MEMS resonator with both hardening and softening hysteretic cycles

We study the nonlinear behavior of a microelectromechanical resonator implemented using the SilTerra MEMS on CMOS platform. The resonator shows, in a same frequency response, two hysteretic cycles of different origin: mechanical and electrical. We observe that, by increasing the resonator DC voltage, the resonator goes from having a purely mechanical (hardening) nonlinear response to a purely electrical (softening) one, experiencing a mixed regime where mechanical and electrical nonlinearities coexist and partially compensate. We explain how the compensation between nonlinearities can be used to improve the phase noise of an MEMS-based oscillator. Specifically, we show that it is possible to operate the resonator at the top bifurcation point, while at the same time suppressing the amplitude-mediated frequency noise.