A micromechanical parametric oscillator for frequency division and phase noise reduction

A capacitive-gap transduced micromechanical resonator array has demonstrated a frst on-chip MEMS-based frequency divider with 61-MHz output generated from a 121-MHz electrical drive through use of a parametric oscillation effect that provides not only the 6 dB reduction in close-to-carrier phase noise expected for a frequency divide-by-two function, but also a remarkable 23 dB reduction in far-from-carrier noise provided by fltering with an extremely high mechanical Q of 91,500. Unlike conventional frequency dividers (i.e., prescalers), the parametric oscillator dispenses with active devices and their associated noise, and operates with close to zero power consumption, limited in principle only by the power required to overcome MEMS resonator loss, estimated here at 100 nW. With an output voltage swing of 450 mVpp generated from only 445 mVpp of input swing on a differential version of this MEMS divider, cascaded chains of fully passive dividers are possible, as needed for use in real-world phase-locked loops and frequency synthesizers.