Murata Manufacturing Co., Ltd.

Lasse Aaltonen

Teemu Salo

Anssi Blomqvist

Jouni Erkkilä

Konsta Wjuga

Tero Sillanpää

Rauli Collin

Teemu Mellin

A gyrocompass device is provided for determining a heading relative to a surface of a rotating planetary body. The gyrocompass device includes one or more MEMS gyroscopes that are each fixed in an orientation on a substrate that is parallel to a first plane and that each provide three or more sense axes that lie within the first plane and are each offset from one another by an offset angle. Moreover, a heading determiner receives rotation rates from the three sense axes and determines the heading of the gyrocompass device relative to the surface of the rotating planetary body by fitting a sine or cosine function to the received rotation rates from the one or more MEMS gyroscopes.

MEMS gyrocompass

A multiplexed sigma-delta analog-to-digital converter (ADC) is provided for digitizing analog input signals of at least two input channels. The ADC includes input circuitry that obtains samples of the input channels and an integrator chain. The integrator chain includes a first delaying integrator and a second delaying integrator. The first delaying integrator processes a sample of one of the two input channels at a time. A first non-delaying integrator is disposed in the integrator chain either between the first delaying integrator and the second delaying integrator or after the second delaying integrator. A clocking arrangement includes a first clock set and a second clock set. Channel selection clocks included in the second clock set are delayed in comparison to the respective channel selection clocks included in the first clock set in order to prevent data from being mixed between consecutive full clock cycles.

Multiplexed higher order sigma-delta analog-to-digital converter

The present invention relates to a method and an apparatus for detecting a failure of a sensor device during operation of the sensor device. A test signal is generated in a first frequency band that is above a signal frequency band of the sensor device and fed into a sensor element of the sensor device. A set of samples is obtained, and a magnitude value is derived from said at least two consecutive samples at the first frequency band. The magnitude value is compared to a magnitude threshold value that defines a minimum for the magnitude value and if the magnitude value is below the magnitude threshold value, it is determined that an error has occurred in the sensor device.

Safety mechanism for sensors

A MEMS gyroscope and a method for compensating drift of sensitivity of a MEMS gyroscope are disclosed. The method comprises demodulating an angular rate signal with an in-phase carrier signal for producing a raw rate signal, and obtaining a DC test signal The DC test signal is filtered for obtaining a raw test signal, and zeroing offset of the raw test signal is performed by comparing each sample of the raw test signal to a test signal normalization value for producing an offset zeroed test signal that represents a deviation of the sample of the raw test signal from the test signal normalization value. A sensitivity compensation multiplier is determined based upon the offset zeroed test signal and a predefined gain coefficient, and drift of sensitivity is compensated by multiplying the raw rate signal with the sensitivity compensation multiplier for providing a sensitivity compensated rate signal.

MEMS gyroscope sensitivity compensation

The present invention relates to a capacitive MEMS gyroscope with drive-signal induced offset cancelling features. In a MEMS gyroscope of the type including force feedback circuitry, the drive signal is modulated according to a known modulation scheme or frequency. The modulation scheme/frequency of the drive signal is used by offset cancelling circuitry to determine the offset in the rate signal caused by the drive signal. The determined offset is subsequently removed from the rate signal.

Offset-cancelling capacitive MEMS gyroscope

A microelectromechanical gyroscope includes a drive loop having a drive element and a drive loop circuitry. The drive loop circuitry includes a clock generating circuitry for generating from the quadrature-phase detection signal a test clock signal, an angular rate phase demodulation signal and a quadrature phase demodulation signal. A sense loop includes a sense element and sense loop circuitry for detecting angular rate and producing a force-feedback signal. A test signal generator receives a quadrature-phase detection signal to be used as a quadrature-phase carrier signal and the test clock signal A summing element sums a test signal with the force-feedback signal to form a sense feedback signal. A rate phase demodulator produces a rate signal by demodulating a sense signal received from the sense loop with the angular rate phase demodulation signal, and a quadrature-phase demodulator produces a quadrature-phase output signal.

Continuous self-test of a gyroscope

A high voltage generating circuitry includes a charge-pump and control loop; the control loop includes a voltage divider which receives a high voltage and provides a divided high voltage output. A first circuit element provides a first voltage difference signal. A controller generates a feedback signal based on the first voltage difference signal. An oscillator generates clock signals for operating the charge-pump circuitry, with the frequency of the clock signals being controlled with a control signal. A feedforward path with a second circuit element combines a second reference voltage and a second voltage generated by inverting the supply voltage for obtaining a second voltage difference signal. A third circuit element generates a feedforward compensation signal inversely proportional to a voltage difference between the supply voltage and the second reference voltage. A fourth circuit element generates the control signal by summing the feedback signal and the feedforward compensation signal.

Charge-pump circuitry and a method for high voltage generation with improved PSRR

A secondary sense loop for a MEMS gyroscope comprises a secondary element comprising at least one mechanical resonator, an analog front end circuitry, a digital secondary loop circuitry and an analog back end circuitry. The digital secondary loop circuitry comprises a signal path receiving at its input an analog secondary input signal representing a detection motion of a mechanical resonator and providing at its output an output signal indicating an angular velocity said MEMS gyroscope is subject to, said signal path comprising an analog-to-digital converter configured to digitize the analog secondary input signal into a digitized secondary signal, and a digital force feedback circuitry controlling operation of a closed force feedback loop configured to adjust response function of the secondary sense loop.

Secondary sense loop with force feedback capability

A digital control circuitry for a MEMS gyroscope is provided. The digital control circuitry comprises a digital primary loop circuitry configured to process a digitized primary signal, a digital secondary loop circuitry configured to process a digitized secondary signal and a digital phase shifting filter circuitry configured to generate two phase shifted demodulation signals from the digitized primary signal. The digital secondary loop is configured to demodulate the digitized secondary signal using the two phase shifted demodulation signals.

Digital controller for a MEMS gyroscope

An improved sensing device comprising micromechanical gyroscope and a feed-back loop with a controller for creating a damp control signal. A frequency generator generates a drive signal for drive mode vibration and a reference signal that is in quadrature-phase in relation to the drive mode vibration. The quadrature reference signal is summed with the damp control signal of the controller. The resulting transducer control signal is fed to the second mechanical resonator. Stable cancellation of the actual mechanical quadrature motion is achieved already at the sensing element level, before the detection of the Coriolis signal.

Vibratory gyroscope

A discrete-time high voltage generating circuitry is described, configured to provide a discrete-time high voltage at a high voltage output only during defined high voltage periods. The discrete-time high voltage generating circuitry includes a current mirror circuitry configured to receive a supply current from a high voltage source and to provide a slew current. The discrete-time high voltage generating circuitry is configured to generate the discrete-time high voltage using the slew current. Further, a method to operate a discrete-time high voltage generating circuitry is described. The circuitry and method may be used to provide a discrete-time self-test bias voltage to at least one capacitive load such as a capacitive MEMS element.

Circuitry and method for generating a discrete-time high voltage

A capacitive sensor device includes capacitive elements for detecting at least two inertial channels. At least one of the inertial channels comprises at least two self-test tones with distinctive fundamental frequencies. Inertial signals in the at least two inertial channels are caused by change of capacitance in the capacitive elements due to movements of rotor masses. Self-test tones are fed into at least one capacitive element under control of a self-test control module and the at least two inertial channels are temporally multiplexed to allow feeding of the self-test tones during normal operation of the capacitive sensor device. Signals in the inertial channels are processed for extracting self-test signals corresponding to the self-test tones, and the self-test signals are analyzed for self-test purposes. Alarm is triggered if multiple consecutive samples of predefined set of self-test signals indicate error with same polarity.

Continuous self-test in capacitive sensor

A closed-loop microelectromechanical gyroscope with a self-test function. At least one test input signal is generated from a signal of the vibrational primary motion and input during operation of the microelectromechanical gyroscope to the sense circuit.

Self-test in a closed-loop vibratory gyroscope

A drive circuit for a MEMS resonator can include closed loop means for detecting and amplifying a signal of the MEMS resonator, and means for feeding the detected and amplified signal as a feedback signal back to the MEMS resonator. The circuitry also comprises DC bias voltage means for generating for the MEMS resonator a first DC bias voltage, and a second DC bias voltage that is controlled according to measured amplitudes of the MEMS resonator, one of the DC bias voltages being summed into the feedback signal. The circuitry comprises also a start-up circuitry adapted to detect a start-up state, and in response to a detected start-up state change at last one of the DC bias voltages to a predefined level. The state of constant oscillation is achieved reliably and in short time.

Drive circuit for MEMS resonator startup

A capacitive sensor that includes at least one capacitive element and a switched-capacitor readout circuit part for detecting at least one signal capacitance that results from motions of the capacitive element. The self-test bias voltage of the actuation circuit part is coupled to the capacitive element during a first period that is synchronized to the front end reset period and occurs when the self-test of the capacitive sensor is enabled by the self-test controller.

Growing community of inventors

Espoo, Finland

Lasse Aaltonen