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US 9,209,746 B2Granted
MEMS oscillators
AssigneeNXP B.V.
InventorsKim Phan Le, Jozef Thomas Martinus van Beek, Martijn Goossens
Life of this patent
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Abstract
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.
Claims10
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.
5 more elements
An oscillator comprising:
- a MEMS resonator having a first terminal and a second terminal;
- wherein the first terminal is configured to both input an input signal having a first frequency ω1 and output an output signal a having a second frequency ω2;
- wherein the resonator is configured to resonate and generate the output signal at the second frequency ω2 in response to the input signal at the first frequency ω1;
- and
- an oscillator circuit having a feedback control loop coupled to the first terminal and configured to convert the second frequency ω2 to the first frequency ω1.
2 more elements
Dependencies are inferred from the claim text.