Analog Devices,inc.

Analog Devices Technology

Jiefeng Yan

Ronald Alan Kapusta

William Albert Clark

Jianrong Chen

Barry L Stakely

James Lin

Ting Gao

Gan Guo

Systems and methods for sensing angular motion using a microelectromechanical system (MEMS) gyroscope are described. These systems and methods may be useful for sensing angular motion in the presence of low-frequency noise, which may be noise below 1 KHz. In a system for sensing angular motion, low-frequency noise may give rise to duty cycle jitter, which may affect the demodulation of the sense signal and cause errors in angular motion estimates. The systems and methods described herein address this problem by relying on double-edge phase detection technique that involves sensing when the rising and falling edges of the resonator signal deviate from their expected values in the idealized 50% duty cycle scenario. To prevent the formation of ripples in the double-edge phase detection that may otherwise affect the demodulation of the sense signal, a switch may be used. The switch may be maintained in a non-conductive state when a ripple is received.

Systems and methods for sensing angular motion in the presence of low-frequency noise

Differential electro-mechanical oscillating circuits are described. These circuits may be used in a variety of contexts to produce differential oscillating signals, such as sine waves or square waves. A switched capacitor circuit (SCC) is used to prevent low-frequency locking, whereby the output of the resonator would otherwise lock to a constant value. More specifically, the SCC provides an impedance in parallel to the resonator between the output terminals of oscillating circuit. The SCC is designed so that, at low frequencies, its impedance is lower than the impedance of the resonator. The presence of such an impedance prevents the formation of an open circuit between the output terminals, thus maintaining the oscillating circuit in the oscillation mode. The differential electro-mechanical oscillating circuits described herein may be used to produce clock signals or otherwise to produce periodic reference signals.

Differential electro-mechanical oscillating circuits and related methods

Sense amplifiers for use in connection with microelectromechanical system (MEMS) gyroscopes are described. The sense amplifiers may be configured to change the level of a gyroscope signal, i.e., the signal produced by a gyroscope in response to angular motion, to a level suitable for processing circuitry arranged to infer the angular velocity. The sense amplifier may further provide a DC discharge path allowing for discharge of the DC component of the output signal. The DC discharge path may include an anti-aliasing filter and a resistive circuit. The anti-aliasing filter may filter the output signal to maintain the resistive circuit in the linear region. The anti-aliasing filter may be designed with a frequency response such that discrete frequency sub-bands are blocked or at least attenuated. The frequency sub-bands may be tuned to substantially match the gyroscope's resonant frequency and its integer multiples.

Sense amplifiers for gyroscopes and related systems and methods

A method for detecting frequency mismatch in microelectromechanical systems (MEMS) gyroscopes is described. Detection of the frequency mismatch between a drive signal and a sense signal may be performed by generating an output signal whose spectrum reflects the physical characteristics of the gyroscope, and using the output signal to determine the frequency fof the sense signal. The output signal may be generated by cross-correlating a random or pseudo-random noise signal with a response signal, where the response signal can be obtained by allowing the noise signal to pass through a system designed to have a noise transfer function that mimics the frequency response of the gyroscope. Since the noise signal is random or pseudo-random, cross-correlating the noise signal with the response signal reveals spectral characteristics of the gyroscope. To improve computational efficiency, the cross-correlation can be performed on demodulated versions of the noise signal and the response signal.

Frequency mismatch detection method for mode matching in gyroscopes

Various embodiments provide methods of determining the quality factor of a resonating body in ways that are advantageous over previously known methods. For example, embodiments allow the determination of the quality factors of a resonating body without preventing the simultaneous use of the resonating body. For micromachined ('MEMS') devices, embodiments allow the determination of the quality factors of a resonating body in a manner that is not dependent on transduction parameters of the MEMS device.

Quality factor estimation for resonators

Systems and methods for capacitance multiplication using one charge pump for a phase lock loop employ a digital controlled loop filter that operates in a time division mode. Embodiments of the loop filter block the current from the charge pump according to the digital control, such that the charge pump cannot charge or discharge the integral capacitor when the digital control is enabled. Because at least a portion of the current is blocked, it takes more time for the charge pump to charge or discharge the capacitor to a certain level. The capacitor then appears to be larger than its actual value with respect to operation of the phase lock loop.

Digitally programmed capacitance multiplication with one charge pump

Apparatus and methods are disclosed, such as those involving a high frequency transmitter. One such apparatus includes a pre-amplifier configured to receive an input signal via an input node; and a capacitor block electrically coupled between the pre-amplifier and an output node from which an output signal is transmitted. The capacitor block is configured to provide charge to the output node or pull charge from the output node while the output signal transitions. The apparatus further includes a switch electrically coupled between the output node and a voltage reference, wherein the switch is turned on or off at least partly in response to a signal from the pre-amplifier. This configuration effectively reduces rise and fall time of the output signal for high-frequency transmission.

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Andover, MA, United States of America

Jiefeng Yan