Abstract: An inertial sensor comprising; a central anchor; a proof mass, wherein the proof mass surrounds the central anchor; a flexure; and a plurality of electrodes is disclosed. The flexure has a shape comprising a first plurality of spiral arms, each winding about the central anchor in a first sense, and a second plurality of spiral arms, each winding about the central anchor in a second sense, the second sense being opposite to the first sense Each of the arms are connected between the central anchor and the proof mass. Advantageously, energy lost through anchor losses and thermoelastic dissipation are reduced in this arrangement, resulting in a higher quality factor for the modes of vibration.

Abstract: There is provided a vibrational energy harvester comprising: a frame, a flexure assembly coupled to the frame, the flexure assembly comprising a flexure configured to flex in a first direction relative to the frame and a mass fixed to the flexure, wherein when the mass is displaced in the first direction from a rest position, the flexure provides a restoring force on the mass to bring the mass back to the rest position, and a transduction assembly configured to convert movement of the mass and flexure into electrical energy, wherein the frame comprises a cavity positioned so that, if the mass is displaced in the first direction beyond a threshold distance, a portion of the flexure assembly extends into the cavity so that compression or restriction of fluid in the cavity applies an additional force on the flexure assembly.

Abstract: An accelerometer comprising: a frame; one or more proof masses suspended from the frame by one or more flexures and movable relative to the frame along a sensing axis; a resonant element assembly, the resonant element assembly comprising a first resonant element and a second resonant element coupled to one another, the first resonant element connected between the one or more proof masses and the frame, the second resonant element connected between the one or more proof masses and the frame, such that movement of the one or more proof masses relative to the frame along the sensing axis results in one of the first and second resonant elements undergoing compression and the other of the first and second resonant elements undergoing tension; and drive circuitry configured to drive the resonant element assembly and a sensing circuit configured to determine a measure of acceleration.

Abstract: An accelerometer comprising: a frame; a first proof mass suspended from the frame by one or more flexures to move relative to the frame along a first axis; a first resonant element assembly fixed between the frame and the first proof mass, wherein movement of the proof mass along the first axis relative to the frame exerts a strain on the first resonant element that affects its resonant behaviour; a second proof mass suspended from the frame by one or more flexures to move relative to the frame along a second axis, a second resonant element assembly fixed between the frame and the second proof mass, wherein movement of the second proof mass along the second axis relative to the frame exerts a strain on the second resonant element that affects its resonant behaviour; wherein the second proof mass surrounds the first proof mass and the first resonant element assembly.

Abstract: An accelerometer comprising: a frame; one or more proof masses suspended from the frame by one or more flexures and movable relative to the frame along a sensing axis; a first resonant element fixed between an anchor on the frame and the one or more proof masses, and extending from the anchor to the one or more proof masses along the sensing axis; a second resonant element fixed between the anchor and the one or more proof masses and extending from the anchor to the one or more proof masses along the sensing axis in a opposite direction to the first resonant element.

Abstract: There is provided a micro electrical mechanical systems device package comprising: a first vacuum enclosure comprising a first enclosure wall; a micro electrical mechanical systems device being positioned within the first vacuum enclosure on a first side of the first enclosure wall; and a second vacuum enclosure, the second side of the first enclosure wall being within the second vacuum enclosure. Advantageously, the first vacuum enclosure is entirely within the second vacuum enclosure.

Abstract: A gravimeter or inertial sensor system and method of operating such a system is provided. The system comprises a variable frequency signal source (100, 101, 102) configured to provide first and second signals, a resonant sensor (103) connected to receive the first signal, a phase comparator (111) connected to the output of the resonant sensor and to receive the second signal, and a controller (114) connected to the phase comparator. In a first mode, the controller controls the desired frequency of the signals from the variable frequency signal source based on a value of the phase comparator output signal to lock the frequency of the input signals to a resonant frequency of the resonant sensor. In a second mode, the controller disconnects from the variable frequency signal source and records an open loop output signal indicative of the physical parameter to be measured based on the response of the resonant sensor.

Abstract: There is provided a vibrational energy harvester comprising: a frame, a flexure assembly coupled to the frame, the flexure assembly comprising a flexure configured to flex in a first direction relative to the frame and a mass fixed to the flexure, wherein when the mass is displaced in the first direction from a rest position, the flexure provides a restoring force on the mass to bring the mass back to the rest position, and a transduction assembly configured to convert movement of the mass and flexure into electrical energy, wherein the frame comprises a cavity positioned so that, if the mass is displaced in the first direction beyond a threshold distance, a portion of the flexure assembly extends into the cavity so that compression or restriction of fluid in the cavity applies an additional force on the flexure assembly.

Abstract: A gravimeter or inertial sensor system and method of operating such a system is provided. The system comprises a variable frequency signal source (100, 101, 102) configured to provide first and second signals, a resonant sensor (103) connected to receive the first signal, a phase comparator (111) connected to the output of the resonant sensor and to receive the second signal, and a controller (114) connected to the phase comparator. In a first mode, the controller controls the desired frequency of the signals from the variable frequency signal source based on a value of the phase comparator output signal to lock the frequency of the input signals to a resonant frequency of the resonant sensor. In a second mode, the controller disconnects from the variable frequency signal source and records an open loop output signal indicative of the physical parameter to be measured based on the response of the resonant sensor.

Abstract: A method of energy harvesting from an electromechanical device providing alternating current (AC) electrical power via a rectifier. The method comprises: identifying when a current flow from the device is substantially zero and, responsive to this identifying: connecting and disconnecting a first charge storage capacitor in parallel with the device with a first sense, such that charge on the device is shared with the first charge storage capacitor, to collect charge from the device on the first charge storage capacitor; preferably clearing the remaining charge on the electromechanical device; and then connecting and disconnecting the first charge storage capacitor in parallel with the device in a second, opposite sense to the first sense, such that the collected charge on the first charge storage capacitor is shared with opposite polarity with the device, to replace opposite polarity charge from the first charge storage capacitor onto the device.

Abstract: A temperature-compensated resonant MEMS device comprises a first and second oscillator circuits comprising a first and second resonant MEMS devices and providing a first and second oscillator outputs. One of the resonant MEMS devices is a temperature reference for the other. A level-sensitive mixer circuit has first and second inputs coupled to the first and second oscillator outputs and has a mixer output to provide a signal responsive to a level of the first and second oscillator outputs. The mixer output comprises sum and difference frequency components of the first and second oscillator outputs. A low-pass filter is coupled to the mixer output to attenuate the sum frequency component of the mixer output. An output coupled to an output of said low-pass filter provides a signal responsive to the difference frequency component.

Abstract: The invention comprises an inertial sensor comprising a frame, a proof mass, a first resonant element, the first resonant element being fixed to the frame and electrostatically coupled to the proof mass, and a second resonant element, the second resonant element being fixed to the frame, adjacent to the first resonant element such that there is substantially no electrostatic coupling between the second resonant element and the proof mass. A coupling is provided between the first resonant element and the second resonant element. A drive means is coupled to the first and second resonant elements for vibrating the first and second resonant elements and a sensor assembly is provided for detecting the amplitude of vibration of at least one of the resonant elements.

Abstract: The invention comprises an inertia! sensor comprising a frame, a proof mass; a first resonant element having a proximal end and a distal end, the first resonant element being fixed to the frame at its proximal end and coupled to the proof mass at its distal end, a second resonant element having a proximal end and a distal end, the second resonant element being fixed to the frame at its proximal end, adjacent to the first resonant element such that there is no coupling between the second resonant element and the proof mass, a means for coupling the first resonant element to the second resonant element; a drive means coupled to the first and second resonant elements for vibrating the first and second resonant elements; and a sensor assembly for detecting the amplitude of vibration of the resonant elements.

Abstract: The invention comprises an inertial sensor comprising a frame, a proof mass, a first resonant element, the first resonant element being fixed to the frame and electrostatically coupled to the proof mass, and a second resonant element, the second resonant element being fixed to the frame, adjacent to the first resonant element such that there is substantially no electrostatic coupling between the second resonant element and the proof mass. A coupling is provided between the first resonant element and the second resonant element. A drive means is coupled to the first and second resonant elements for vibrating the first and second resonant elements and a sensor assembly is provided for detecting the amplitude of vibration of at least one of the resonant elements.

Abstract: The invention comprises an inertia! sensor comprising a frame, a proof mass; a first resonant element having a proximal end and a distal end, the first resonant element being fixed to the frame at its proximal end and coupled to the proof mass at its distal end, a second resonant element having a proximal end and a distal end, the second resonant element being fixed to the frame at its proximal end, adjacent to the first resonant element such that there is no coupling between the second resonant element and the proof mass, a means for coupling the first resonant element to the second resonant element; a drive means coupled to the first and second resonant elements for vibrating the first and second resonant elements; and a sensor assembly for detecting the amplitude of vibration of the resonant elements.

Abstract: A semiconductor device such as a resonant device has a capacitive, non-piezoelectric, actuator, the actuator comprising a depletion region. A capacitive actuator for a semiconductor device, a method for fabricating such an actuator, and a method for operating a semiconductor device are also provided. In the operating method, a drive voltage is applied across the depletion region of the semiconductor device, such as a drive voltage having an alternating voltage component for driving a resonant semiconductor device.