Nonlinear mixing in surface-micromachined tuning fork oscillators

This paper discusses the conversion of voltage to frequency in surface-micromachined tuning fork oscillators intended as resonant transducers. First, the sources of nonlinearity in the mechanical structure and electrostatic actuation are discussed. These nonlinearities are analytically combined to show that low-frequency voltage drift in the sustaining amplifier is directly converted into a frequency shift in the oscillator output. Experimental evidence of this effect is presented, and it is shown that this is the dominant source of near-carrier frequency instability in the experimental system