Various embodiments are directed to a method and system for mapping or visualizing the magnetic fields and their associated field strengths of an object, such as a mobile computing device. An example source of the magnetic fields may be a near-field communication (NFC) reader configured in the object. A computer vision system or device may track a visual marker arranged near or on a magnetic field strength detector in order to associate, match, or map the magnetic field strength measurement readings of the detector at different positions or locations on the object. The computer vision system may generate and display a heat map of the object based on at least the magnetic field strength measurements and their relative positions.

Various embodiments are directed to a method and system for mapping or visualizing the magnetic fields and their associated field strengths of an object, such as a mobile computing device. An example source of the magnetic fields may be a near-field communication (NFC) reader configured in the object. A computer vision system or device may track a visual marker arranged near or on a magnetic field strength detector in order to associate, match, or map the magnetic field strength measurement readings of the detector at different positions or locations on the object. The computer vision system may generate and display a heat map of the object based on at least the magnetic field strength measurements and their relative positions.

An exemplary method of indicating a condition of grout within a post-tensioned tendon involves positioning a magnet and a metallic sensing plate in close proximity to an outer surface of the post-tensioned tendon; rotating the magnet and the metallic sensing plate around the outer surface of the post-tensioned tendon; measuring an amount of magnetic forces applied to the magnet during rotation of the magnet around the post-tensioned tendon; measuring an impedance between the metallic sensing plate and metallic strands within the post-tensioned tendon during rotation of the metallic sensing plate around the post-tensioned tendon; and generating an image of a cross-section of the post-tensioned tendon indicating one or more grout conditions in spatial proximity to the metallic strands within the post-tensioned tendon based on measurement data using the magnet and the metallic sensing plate.

A method and system of maintaining a trained neural network for mobile device indoor navigation and positioning. The method comprises receiving a set of magnetic measured parameters acquired at a mobile device positioned at a first location of an indoor area; computing, at an output layer of a trained neural network, an output error based on comparing a magnetic input feature in accordance with the magnetic measured parameters to a magnetic output feature generated at the output layer, the magnetic output feature being generated at least in part based on a matrix of weights associated with at least a first neural network layer; and if the output error exceeds a threshold value, re-training the neural network based at least in part upon re-initializing the matrix of weights associated with the at least a first neural network layer.

A method and system of maintaining a trained neural network for mobile device indoor navigation and positioning. The method comprises receiving a set of magnetic measured parameters acquired at a mobile device positioned at a first location of an indoor area; computing, at an output layer of a trained neural network, an output error based on comparing a magnetic input feature in accordance with the magnetic measured parameters to a magnetic output feature generated at the output layer, the magnetic output feature being generated at least in part based on a matrix of weights associated with at least a first neural network layer; and if the output error exceeds a threshold value, re-training the neural network based at least in part upon re-initializing the matrix of weights associated with the at least a first neural network layer.

Systems and methods for providing a visualization capability to map magnetic fields. The system utilizes a high-sensitivity magnetic field sensor (e.g., a magnetometer inside a tube made of magnetic shielding material) disposed on one side of a magnetic field modulation screen to acquire measurement data representing an image of a magnetic field. The magnetic field modulation screen includes a multiplicity of magnetic field-generating pixel elements (e.g., current-carrying loops made of electrically conductive material). Optionally, the system also uses compressive sensing techniques to reduce the amount of measurement data required to reconstruct an image of the original magnetic field. Compressive sensing is enabled by not supplying current to a different selected individual magnetic field-generating pixel element of the magnetic field modulation screen at successive sampling times.

Systems and methods for providing a visualization capability to map magnetic fields. The system utilizes a high-sensitivity magnetic field sensor (e.g., a magnetometer inside a tube made of magnetic shielding material) disposed on one side of a magnetic field modulation screen to acquire measurement data representing an image of a magnetic field. The magnetic field modulation screen includes a multiplicity of magnetic field-generating pixel elements (e.g., current-carrying loops made of electrically conductive material). Optionally, the system also uses compressive sensing techniques to reduce the amount of measurement data required to reconstruct an image of the original magnetic field. Compressive sensing is enabled by not supplying current to a different selected individual magnetic field-generating pixel element of the magnetic field modulation screen at successive sampling times.

In an embodiment, a method for transmitting data from a wireless power receiver to a wireless power transmitter includes: wirelessly receiving power at a first frequency from a transmitter LC tank using a receiver LC tank; rectifying a voltage of the receiver LC tank using a rectifier; and while wirelessly receiving power, controlling a transistor coupled to the receiver LC tank to cause inflections in a transmitter current flowing through the transmitter LC tank to transmit data, detecting time locations of the inflections of the transmitter current within an oscillating cycle of the transmitter current based on a magnitude of the transmitter current, and determining the data based on the detected time locations.

In an embodiment, a method for transmitting data from a wireless power receiver to a wireless power transmitter includes: wirelessly receiving power at a first frequency from a transmitter LC tank using a receiver LC tank; rectifying a voltage of the receiver LC tank using a rectifier; and while wirelessly receiving power, controlling a transistor coupled to the receiver LC tank to cause inflections in a transmitter current flowing through the transmitter LC tank to transmit data, detecting time locations of the inflections of the transmitter current within an oscillating cycle of the transmitter current based on a magnitude of the transmitter current, and determining the data based on the detected time locations.

A magnetic sensor device with an array of magnetic sensors arranged on a common semiconductor substrate to measure the multi-axis magnetic field of an arbitrary region with high spatial resolution, reduced sensing distance, higher measurement throughput, motion tolerance, temperature tolerance, and improved manufacturing yield. A multi-axis magnetic sensor array device fabricated on a common semiconductor substrate is optimized offering additional improvements to reduce measurement time, increase spatial resolution uniformity, and lower thermal compensation cost. Further, the central area of a surface is utilized to measure the normal magnetic field. A perimeter of Hall effect plates measuring the components of the magnetic field in the plane of the measuring surface, which allows for a very high density of normal field measurements allows calculation of the in-plane field components. Error along the edges can be mitigated with the in-plane measured components.