Abstract: Disclosed is a compact, multi-user magnetic tracking system. In an embodiment, a compactness is achieved by using a single coil and inertial sensors at the transmitter and magnetometers and inertial sensors at the receiver for sensing the magnetic field generated by the single coil and for determining a position and attitude of the receiver relative to the transmitter. The transmitter and receiver each include a wireless transceiver for exchanging clock synchronization data and sending transmitter attitude data to the receiver. In another embodiment, frequency or time division multiplexing is used to differentiate between multiple users of the multi-user magnetic tracking system.

Abstract: The enclosed embodiments are directed to a magnetoresistance (MR) sensor with a biased free layer for improved stability of magnetic performance. In an embodiment, an MR sensor comprises: a first antiferromagnetic (AF) pinning layer; a magnetic fixed layer disposed on the first AF layer; a tunnel barrier disposed on the magnetic fixed layer; a magnetic coupled free layer disposed on the tunnel barrier; a AF coupling layer disposed on the magnetic coupled free layer; a magnetic pinned layer disposed on the AF coupling layer; and a second AF pinning layer disposed on the magnetic pinned layer. In an embodiment, a method of unpinning a pinned free layer uses a current pulse through the MR sensor to self-heat above a blocking temperature of the AF pinning layer, and then reading the MR sensor after the current pulse is reduced or removed and the MR sensor cools back below the blocking temperature.

Abstract: Embodiments are disclosed for yoke structures for improved magnetometer performance. In an embodiment, a magnetometer comprises: a yoke structure comprising at least one hard magnetic layer and at least one soft magnetic layer arranged along a dimension of the yoke structure, where a first coercivity of the at least one hard magnetic layer is greater than a second coercivity of the at least one soft magnetic layer; and at least one magnetic sensing element located in proximity to the at least one soft magnetic layer. In another embodiment, a magnetometer comprises: a multilayer yoke structure comprising layers of non-magnetic material and magnetic material along a dimension of the yoke structure; and at least one magnetic sensing element located in proximity to the yoke structure.

Abstract: Aspects of the subject disclosure include a pressure-sensing device consisting of a housing including a membrane and one or more piezoresistive elements disposed on the membrane to sense a displacement due to a deflection of the membrane. A first set of electrodes is disposed over the membrane, and a second set of electrodes is disposed on a permeable port of the device at a distance from the membrane. The first and second sets of electrodes form an electrostatic actuator to exert a repulsive force onto the membrane to reduce the deflection of the membrane.

Abstract: Systems, methods, apparatuses and non-transitory, computer-readable mediums are disclosed for short-range position tracking using a stationary magnetic field gradient. In an embodiment, a method comprises: obtaining, by a sensing array of a device worn or held by a user in an environment, a measurement of a stationary magnetic field generated by a magnetic source in the environment, the stationary magnetic field being independent of an ambient magnetic field in the environment; determining based on the measurement, a change in the magnetic field over time; determining based on the measurement, a change in the magnetic field over distance; obtaining, by the processor, a rotation angle of the device; determining a velocity of the device based on the change in the magnetic field over time, the change in the magnetic field over distance and the rotation angle of the device; and integrating the velocity to obtain a position of the device.

Abstract: Disclosed is a magnetometer architecture that couples one or more coils to a magnetic yoke to allow the reset of the magnetic yoke and one or more magnetic field sensors simultaneously after, for example, exposure to a large stray magnetic field. Also, disclosed is a magnetometer architecture that integrates separate magnetic pole pieces offset from the yoke that are each wound by a reset coil to allow reset of the one or more magnetic field sensors.

Abstract: A head-mounted device or other electronic device may emit an alternating-current magnetic field. A wireless controller may have alternating-current magnetometers for monitoring the alternating-current field. The wireless controller may also have an accelerometer for measuring the orientation of the controller relative to the Earth's gravity and a direct-current magnetometer for measuring the orientation of the controller relative to the Earth's magnetic field. The alternating-current magnetometers may be three-coil magnetometers located at different locations in a controller housing. Using data from the alternating-current magnetometers, the direct-current magnetometer, the accelerometer, and/or other sensors, the wireless controller can determine the position and orientation of the wireless controller. This information can be wirelessly transmitted to the head-mounted device to control the head-mounted device.

Abstract: Aspects of the subject disclosure include a pressure-sensing device consisting of a housing including a membrane and one or more piezoresistive elements disposed on the membrane to sense a displacement due to a deflection of the membrane. A first set of electrodes is disposed over the membrane, and a second set of electrodes is disposed on a permeable port of the device at a distance from the membrane. The first and second sets of electrodes form an electrostatic actuator to exert a repulsive force onto the membrane to reduce the deflection of the membrane.

Abstract: Embodiments are disclosed for various configurations of a hybrid Hall/MR magnetometer with self-calibration. In an embodiment, a method comprises: a circuit coupled to a magnetometer and configured to determine whether the magnetometer is to operate in a sensing operation mode or a self-calibration operation mode. The magnetometer comprises a Hall sensor and MR sensor coupled to the circuit. In accordance with determining a sensing operation mode, the Hall sensor is turned and the MR sensor is turned on; and an external magnetic field is measured using the MR sensor. The magnetic field measurement is calibrated using a MR sensor bias error determined in a self-calibration operation mode of the sensor.

Abstract: Disclosed is a magnetometer architecture that couples one or more coils to a magnetic yoke to allow the reset of the magnetic yoke and one or more magnetic field sensors simultaneously after, for example, exposure to a large stray magnetic field. Also, disclosed is a magnetometer architecture that integrates separate magnetic pole pieces offset from the yoke that are each wound by a reset coil to allow reset of the one or more magnetic field sensors.

Abstract: Aspects of the subject technology relate to an apparatus including a housing, one or more piezoresistive elements and a magnetic actuator. The housing includes a membrane, and the piezoresistive elements are disposed on the membrane to sense a displacement due to a deflection of the membrane. The magnetic actuator is disposed inside a cavity of the housing. The magnetic actuator exerts a repulsive force onto the membrane to reduce the deflection of the membrane.

Abstract: Aspects of the subject technology relate to an apparatus including a housing and a substrate. The apparatus further includes a sensor, an integrated circuit mounted on the substrate, and one or more heating elements configured to adjust a temperature of the sensor to facilitate measurement of temperature sensitivity and calibration of the sensor.

Abstract: Disclosed is a compact 3-axis coil design for a magnetic tracking system. In an embodiment, compactness is achieved by using a 3-axis coil in the transmitter that includes a scaffold design with a side surface having a curved groove for guiding one or more windings of a z-axis coil, such that the physical geometry is not increased.

Abstract: Disclosed is a magnetometer architecture that couples one or more coils to a magnetic yoke to allow the reset of the magnetic yoke and one or more magnetic field sensors simultaneously after, for example, exposure to a large stray magnetic field. Also, disclosed is a magnetometer architecture that integrates separate magnetic pole pieces offset from the yoke that are each wound by a reset coil to allow reset of the one or more magnetic field sensors.

Abstract: An electronic device can include a housing defining an internal volume and a pressure sensor assembly disposed in the internal volume and in communication with an ambient environment. The pressure sensor assembly can include a structure at least partially enclosing a sensor volume, a pressure sensor affixed to a die disposed in the sensor volume, and an exposed moisture detection conductor positioned in the sensor volume.

Abstract: Aspects of the subject technology relate to an apparatus including a housing, one or more piezoresistive elements and a magnetic actuator. The housing includes a membrane, and the piezoresistive elements are disposed on the membrane to sense a displacement due to a deflection of the membrane. The magnetic actuator is disposed inside a cavity of the housing. The magnetic actuator exerts a repulsive force onto the membrane to reduce the deflection of the membrane.

Abstract: Disclosed is a compact 3-axis coil design for a magnetic tracking system. In an embodiment, compactness is achieved by using a 3-axis coil in the transmitter that includes a scaffold design with a side surface having a curved groove for guiding one or more windings of a z-axis coil, such that the physical geometry is not increased.

Abstract: Disclosed is a compact, multi-user magnetic tracking system. In an embodiment, a compactness is achieved by using a single coil and inertial sensors at the transmitter and magnetometers and inertial sensors at the receiver for sensing the magnetic field generated by the single coil and for determining a position and attitude of the receiver relative to the transmitter. The transmitter and receiver each include a wireless transceiver for exchanging clock synchronization data and sending transmitter attitude data to the receiver. In another embodiment, frequency or time division multiplexing is used to differentiate between multiple users of the multi-user magnetic tracking system.

Abstract: Magnetic sensing technology can be used to detect changes, or disturbances (e.g., changes in magnetic field strength), in magnetic fields and can be used to measure the precise location/positioning of an electronic device in proximity to a magnetic source. In order to avoid interference by earth's static magnetic field, a modulated magnetic field can be used for magnetic based proximity sensing. Received modulated magnetic field signals can be demodulated to determine a received magnetic field strength. A drive current of a magnetic transmitter coil can be varied to maintain the detected magnetic field strength at a target value or within a desirable range. The drive current can also be varied to remain below a burnout current level that can cause damage to the transmitter coil.

Abstract: An electronic device can include a housing defining an internal volume and a pressure sensor assembly disposed in the internal volume and in communication with an ambient environment. The pressure sensor assembly can include a structure at least partially enclosing a sensor volume, a pressure sensor affixed to a die disposed in the sensor volume, and an exposed moisture detection conductor positioned in the sensor volume.