MEMS oscillators

摘要

The invention provides MEMS oscillator designs in which the thermal actuation and piezoresistive detection signals are separated.;A first approach splits the frequency of the loop into two distinct components, an actuation frequency and a detection frequency. A second approach modifies the design of the MEMS resonator such that the actuation signal follows a different path through the MEMS resonator than the detection signal.

主权项

1. An oscillator comprising:
a MEMS resonator having a first terminal and a second terminal; an AC current source for providing an AC current to a resonator input coupled to the first terminal, thereby to induce an alternating strain in the resonator by means of the thermal expansion effect to drive the resonator into resonance; and a piezoresistive read out sensor, coupled to the first terminal, for monitoring a resistance of at least a portion of the resonator to derive an oscillating output signal at an output of an oscillator circuit; and wherein the oscillator circuit provides the ac current with a first frequency ω1 to actuate the resonator and wherein a second different frequency ω2 is generated in the resonator by the piezoresistive effect to derive the output signal, wherein the oscillator circuit comprises a converter in a feedback control loop between the oscillator output and the resonator input for converting from the second frequency to the first frequency; and wherein the first terminal of the resonator is configured to both receive the AC current at the first frequency ω1 and output the piezoresistive read out at the second frequency ω2.