# US 2014/0360246 A1 · Micro-electro-mechanical-system resonant sensor and method of controlling the same

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- Number: US 2014/0360246 A1
- Document ID: US20140360246A1
- Status: Published application
- Kind: A1
- Application number: 14/092,202
- Filed: 2013-11-27
- Published: 2014-12-11
- Earliest claimed: 2013-06-07
- Assignees: Hyundai Motor Company
- Applicants: Hyundai Motor Company
- Inventors: Soon-myung Kwon; Sang Gyu Park
- Web page: https://patentgrep.com/patent/US20140360246A1

## CPC

- H03H 9/02433: {Means for compensation or elimination of undesired effects}
- G01N 29/022: {Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices (microdevices per se B81B)}
- G01N 29/036: by measuring frequency or resonance of acoustic waves
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A micro-electro-mechanical-system (MEMS) resonant sensor includes: a MEMS unit that generates an output signal corresponding to a vibration component of a mass body vibratable between a first driving electrode and a second driving electrode; an automatic gain control (AGC) unit that automatically generates a comparative voltage by controlling a gain of the output signal; and a bias unit that receives a reference voltage and generates a bias voltage using the comparative voltage and the reference voltage, wherein a sinusoidal driving voltage is applied to the first driving electrode and the second driving electrode, and the bias voltage is applied to the mass body. It can maintain the amplitude of the mass body stably in the MEMS resonant sensor, and prevent malfunction of an electronic circuit by reducing a response error of the MEMS resonant sensor.

## Claims

### Claim 1

A micro-electro-mechanical-system (MEMS) resonant sensor comprising:
a MEMS unit that generates an output signal corresponding to a vibration component of a mass body vibratable between a first driving electrode and a second driving electrode;
an automatic gain control (AGC) unit that generates a comparative voltage by automatically controlling a gain of the output signal of the MEMS unit; and
a bias unit that receives the comparative voltage and a reference voltage and generates a bias voltage using the comparative voltage and the reference voltage,
wherein a sinusoidal driving voltage is applied to the first driving electrode and the second driving electrode, and the bias voltage is applied to the mass body.

### Claim 2 (depends on 1)

The MEMS resonant sensor of claim 1, further comprising a hold amplifier generating an input signal that is input to the MEMS unit by amplifying the output signal of the MEMS unit.

### Claim 3 (depends on 1)

The MEMS resonant sensor of claim 1, wherein the bias unit generates a sum or a difference of the reference voltage and the comparative voltage as the bias voltage.

### Claim 4

A method of controlling a MEMS resonant sensor using a mass body vibratable by an electrostatic force between a first driving electrode and a second driving electrode, the method comprising:
generating an output signal corresponding to a vibration component of the mass body;
generating a comparative voltage corresponding to the output signal by automatically controlling a gain of the output signal;
adjusting a level of a bias voltage applied to the mass body by using a reference voltage and the comparative voltage; and
controlling the electrostatic force by applying the adjusted bias voltage to the mass body.

### Claim 5 (depends on 4)

The method of claim 4, wherein the generation of the comparative voltage corresponding to the output signal comprises applying a sinusoidal driving voltage to the first driving electrode and the second driving electrode.

### Claim 6 (depends on 4)

The method of claim 4, wherein the generation of the comparative voltage corresponding to the output signal by automatically controlling the gain of the output signal comprises generating a sum or a difference of the reference voltage and the comparative voltage as the bias voltage.

### Claim 7

A method of controlling a MEMS resonant sensor, comprising:
applying a sinusoidal driving voltage to a first driving electrode and a second driving electrode;
applying a bias voltage to a mass body which vibrates in a first direction between the first driving electrode and the second driving electrode by an electrostatic force;
generating an output signal corresponding to a vibration component of the mass body; and
determining a size of a physical quantity input from the outside in a second direction by detecting the output signal,
wherein the applying the bias voltage to the mass body comprises:
generating a comparative voltage corresponding to the output signal by automatically controlling a gain of the output signal;
adjusting a level of the bias voltage applied to the mass body by using a reference voltage and the comparative voltage; and
controlling the electrostatic force by applying the adjusted bias voltage to the mass body.

### Claim 8 (depends on 7)

The method of claim 7, wherein the generation of the comparative voltage corresponding to the output signal by automatically controlling the gain of the output signal comprises generating a sum or a difference of the reference voltage and the comparative voltage as the bias voltage.