# US 2013/0152686 A1 · System and Method of Reducing Noise in a MEMS Device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0152686 A1 - Document ID: US20130152686A1 - Status: Published application - Kind: A1 - Application number: 13/328,177 - Filed: 2011-12-16 - Published: 2013-06-20 - Earliest claimed: 2011-12-16 - Assignees: Analog Devices, Inc. - Inventors: Srinivasan Venkatraman - Web page: https://patentgrep.com/patent/US20130152686A1 ## CPC - G01P 15/125: by capacitive pick-up - G01C 19/56: Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces - G01C 19/5726: Signal processing - G01P 15/18: in two or more dimensions - H04R 19/005: {using semiconductor materials} - G01P 2015/0865: {using integrated signal processing circuitry} - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract A MEMS system has an input for receiving a plurality of frequency division multiplexed variable capacitance signals, and a readout node electrically coupled with the input. Each variable capacitance signal is produced by a variable capacitor and has data relating to movement of microstructure associated with that variable capacitor. Moreover, each variable capacitance signal is produced by a variable capacitor that is different from the variable capacitor producing any of the other variable capacitance signals. The system further has a mixer electrically coupled with the readout node, and an output electrically coupled with the mixer. The mixer is configured to substantially continuously receive the plural variable capacitance signals. In addition, the output has an output interface for delivering the plurality of variable capacitance signals in parallel. The signals at the output should represent real time signals, as compared to stale sample and hold signals used in prior art systems. ## Claims ### Claim 1 A MEMS system comprising: an input for receiving a plurality of frequency division multiplexed variable capacitance signals, each variable capacitance signal being produced by a variable capacitor and having data relating to movement of microstructure associated with that variable capacitor, each variable capacitance signal being produced by a variable capacitor that is different from the variable capacitor producing any of the other variable capacitance signals; a readout node electrically coupled with the input; a mixer electrically coupled with the readout node, the mixer being configured to substantially continuously receive the plural variable capacitance signals; and an output electrically coupled with the mixer, the output having an output interface for delivering the plurality of variable capacitance signals in parallel. ### Claim 2 (depends on 1) The MEMS system as defined by claim 1 further comprising a frequency division multiplexer for producing the plurality of variable capacitance signals. ### Claim 3 (depends on 2) The MEMS system as defined by claim 2 wherein the frequency division multiplexer produces the plurality of variable capacitance signals to be non-overlapping in frequency. ### Claim 4 (depends on 1) The system as defined by claim 1 further comprising: a plurality of variable capacitors for producing the plurality of variable capacitance signals, the variable capacitors forming an accelerometer. ### Claim 5 (depends on 1) The MEMS system as defined by claim 1 wherein the mixer comprises a demodulator for demodulating at a demodulation frequency, the plurality of variable capacitance signals being driven by drive signals having drive frequencies, the drive frequencies being different than the demodulation frequency. ### Claim 6 (depends on 1) The MEMS system as defined by claim 1 further comprising a plurality of filters electrically coupled with the mixer, the plurality of filters filtering and delivering each of the plurality of capacitance signals to the output interface. ### Claim 7 (depends on 1) The MEMS system as defined by claim 1 wherein the mixer comprises a demodulator. ### Claim 8 (depends on 1) The MEMS system as defined by claim 1 further comprising: a first multiplex signal generator for generating a first multiplex signal at a first frequency; and a second multiplex signal generator for generating a second multiplex signal at a second frequency, the first frequency and second frequency being different, the first and second multiplex signal generators producing at least some of the plurality of variable capacitance signals. ### Claim 9 (depends on 8) The MEMS system as defined by claim 8 wherein the mixer comprises a demodulator for demodulating signals at a demodulation frequency, the demodulation frequency being different from both the first and second frequencies. ### Claim 10 (depends on 1) The MEMS system as defined by claim 1 further comprising: a first multiplex signal generator for generating a first multiplex signal at a first frequency; and a second multiplex signal generator for generating a second multiplex signal at a second frequency, the first frequency and second frequency being the same but phase shifted relative to each other, the first and second multiplex signal generators producing at least some of the plurality of variable capacitance signals. ### Claim 11 A MEMS device comprising: a plurality of variable capacitors for producing a plurality of respective variable capacitor signals; a frequency division multiplexer coupled with the plurality of variable capacitors and being configured to multiplex the plurality of variable capacitor signals to produce a plurality of multiplexed capacitance signals; a readout node electrically coupled with the multiplexer for receiving the plurality of frequency division multiplexed capacitance signals; and an output electrically coupled with the readout node, the output being configured to produce each of the capacitance signals in parallel. ### Claim 12 (depends on 11) The MEMS system as defined by claim 11 wherein the plurality of variable capacitors and the output are on a single chip. ### Claim 13 (depends on 11) The MEMS system as defined by claim 11 wherein the plurality of variable capacitors and the output are on different chips. ### Claim 14 (depends on 11) The MEMS system as defined by claim 11 further comprising a package with an interior, the interior containing the plurality of variable capacitors and the output. ### Claim 15 (depends on 11) The MEMS system as defined by claim 11 further comprising a demodulator for demodulating a carrier signal carrying the multiplexed signals to produce the multiplexed signals, the demodulator configured to demodulate the carrier signal at a demodulate frequency, the multiplexed signals being multiplexed at a plurality of multiplex frequencies, the multiplex frequencies and demodulate frequency being different. ### Claim 16 (depends on 15) The MEMS system as defined by claim 15 wherein the multiplex frequencies are non-overlapping in frequency. ### Claim 17 A method of monitoring movement of microstructure in a MEMS device, the MEMS device having a first variable capacitor configured to produce a first capacitance signal relative to a first frame of reference, and a second variable capacitor configured to produce a second capacitance signal relative to a second frame of reference, the method comprising: modulating the first capacitance signal toward a readout node using a first frequency division multiplex signal; and modulating the second capacitance signal toward the same readout node using a second frequency division multiplex signal, the second capacitance signal being modulated at substantially the same time that the first capacitance signal is modulated toward the readout node, the first and second capacitance signals not interfering with each other. ### Claim 18 (depends on 17) The method as defined by claim 17 further comprising demodulating both signals at substantially the same time to produce a demodulated signal. ### Claim 19 (depends on 18) The method as defined by claim 18 wherein demodulating comprises demodulating at a demodulation frequency, the first frequency division multiplex signal having a first frequency, the second frequency division multiplex signal having a second frequency, the first and second frequencies being different from the demodulation frequency. ### Claim 20 (depends on 18) The method as defined by claim 18 further comprising: filtering the demodulated signal to produce the first and second capacitive signals; forwarding the first capacitive signal to a first interface; and forwarding the second capacitive signal to a second interface, the first and second interfaces being in parallel.