A Micromechanical Frequency Controlled Pulse Density Modulator

This work demonstrates, for the first time, frequency-to-pulse density modulation (PDM) functionality in micromechanical resoswitches based on the period doubling bifurcation mechanism. Unlike the previously demonstrated resoswitch-based squegging clock generator of [1] that operates at the squegging oscillation state (low-frequency ringing state), of which the squegging frequency is controlled by the contact structural or material stiffness, this work demonstrates much nonlinear rich dynamical switching behaviors controlled by the period-doubling (PD) bifurcation cascade along with the driving frequency at the tapping region, featuring various M/N impact/motion (M impacts among N motions) combinations. Implemented on a CMOS-MEMS folded-beam comb-driven resoswitch, the period-doubling bifurcation derived M/N impact/motion is directly transferred to a series of pulse trains with a density determined by the M/N ratio. This work not only verifies the nonlinear period-doubled operation in micromechanical resoswitches but also opens a new possibility of designing resoswitch-based communication receivers with more sophisticated modulation schemes based on the frequency controlled PDM in addition to FSK/OOK [2].