Simultaneous multi-frequency switchable oscillator and FSK modulator based on a capacitive-gap MEMS disk array

An electromechanical circuit constructed from array-composites of capacitive-gap micromechanical resonators with differing frequencies, wired in closed-loop feedback with a single ASIC amplifier, provides a first MEMS-based multi-frequency oscillator generating simultaneous oscillation outputs in the vicinity of 61 MHz. The use of only one amplifier for all frequencies (as opposed to one for each frequency) saves substantial power and is made possible by exploiting softening and damping non-linearities in the MEMS resonators, often considered a limitation, but here providing amplitude limiting that prevents amplifier desensitization to other frequencies. Furthermore, electrical stiffness-based frequency tuning enables Frequency-Shift Keyed (FSK) modulation of the output waveform, offering a space and power-efficient multichannel transmitter, as desired for mobile applications requiring long battery life, such as wireless sensor nodes. Indeed, while capable of multiple simultaneous and independent frequency outputs, this oscillator consumes only 137 μW, which is one-third that of previous multi-frequency efforts that only produce one frequency at a time [1].