A three-axis upstream-modulated low-noise magnetoresistive sensor comprises an X-axis magnetoresistive sensor, a Y-axis magnetoresistive sensor, and a Z-axis magnetoresistive sensor, wherein the X, Y, and Z-axis magnetoresistive sensors respectively comprise X, Y, and Z-axis magnetoresistive sensing unit arrays, X, Y, and Z-axis soft ferromagnetic flux concentrator arrays, and X, Y, and Z-axis modulator wire arrays. The X, Y, and Z-axis magnetoresistive sensing unit arrays are electrically interconnected into X, Y, and Z-axis magnetoresistive sensing bridges respectively. The X, Y, and Z-axis modulator wire arrays are electrically interconnected into individual two-port X, Y, and Z-axis excitation coils. In order to measure external magnetic fields, the two-port X, Y, and Z-axis excitation coils are separately supplied with high-frequency alternating current at a frequency f, from a current supply. The X-axis magnetoresistive sensor, Y-axis magnetoresistive sensor, and Z-axis magnetoresistive sensor each output harmonic signal components having a frequency of 2f, which are then demodulated to obtain the X, Y, and Z-axis low-noise signals. This device is small in size, has low noise, and a simple structure.

A magnetic field detection sensor includes a magneto-impedance element configured to make use of the magneto-impedance effect, and a negative-feedback bias coil configured to apply a bias magnetic field to the magneto-impedance element. The magnetic field detection sensor is configured to detect an external magnetic field based on an output obtained by applying an alternating-current to the magneto-impedance element. The magneto-impedance element includes a non-magnetic substrate, and a magnetic thin-film that is provided on a surface of the non-magnetic substrate. The magnetic field detecting direction matches the longitudinal direction of the magneto-impedance element, and the magnetic thin-film is configured to have a magnetic anisotropy such that a direction of an axis of easy magnetization thereof matches the magnetic field detecting direction.

A Hall sensor trim circuit includes a current source, a transistor, a reference voltage circuit, an amplifier, and a Hall sensor. The transistor includes a first terminal, a second terminal, and a third terminal. The third terminal is coupled to the current source. The amplifier includes an output terminal, a first input terminal, and a second input terminal. The output terminal is coupled to the first terminal of the transistor. The first input terminal is coupled to the second terminal of the transistor. The second input terminal is coupled to the reference voltage circuit. The Hall sensor is coupled to the current source.

One example includes a sensor system. A cell system includes a pump laser which generates a pump beam to polarize alkali metal vapor enclosed within a sensor cell. A detection system includes a probe laser to generate a probe beam. The detection system can calculate at least one measurable parameter based on characteristics of the probe beam passing through the sensor cell resulting from precession of the polarized alkali metal vapor in response to an applied magnetic field. A pump beam control system pulse-width modulates a frequency of the pump beam to provide a pulse-width modulated (PWM) pump beam, and controls a duty-cycle of the PWM pump beam based on the characteristics of the probe beam passing through the sensor cell in a feedback manner to control polarization uniformity of the alkali metal vapor and to mitigate the effects of AC Stark shift on the at least one measurable parameter.

Methods, computer-readable storage devices, and systems are described for reducing movement of a patient undergoing a magnetic resonance imaging (MRI) scan by aligning MRI data, the method implemented on a Framewise Integrated Real-time MRI Monitoring (“FIRMM”) computing device including at least one processor in communication with at least one memory device. Aspects of the method comprise receiving a data frame from the MRI system, aligning the received data frame to a preceding data frame, calculating motion of a body part between the received data frame and the preceding data frame, calculating total frame displacement, and excluding data frames with a cutoff above a pre-identified threshold of the total frame displacement.

A Hall electromotive force signal detection circuit suppresses variations of spike-like error signals that become obstacles to high-precision detection of Hall electromotive force signals. To this end, in the Hall electromotive force signal detection circuit driving plural Hall elements by spinning current techniques and using plural transconductance amplifiers, a reference signal Vcom is supplied from a feedback network controller to a Hall signal feedback network that performs a feedback control so that common voltages of Hall electromotive force signals from the plural Hall elements match with the reference signal Vcom and to an output signal feedback network that feeds back a voltage obtained by dividing a difference between an output voltage and the reference signal Vcom. In this manner, the variations of spike signals are suppressed.

In one aspect, bridge circuitry includes a first magnetoresistance (MR) element; a second MR element connected in series with the first MR element at a first node; a third MR element; a fourth MR element connected in series with the third MR element at a second node; a first switch connected at one end to a supply voltage and connected at the other end to the third MR element; a second switch connected at one end to ground and connected at the other end to the fourth MR element; a third switch connected at one end to ground and connected at the other end to the third MR element and the first switch; and a fourth switch connected at one end to the supply voltage and the other end to the fourth MR element and the second switch. The first and second MR elements are in parallel with the third and fourth MR elements.

There is provided a magnetic noise rejection apparatus which includes: a plurality of cancellation coils arranged near a target object; a plurality of magnetic sensors disposed inside the respective cancellation coils; an adder circuit configured to take a sum of outputs of the plurality of magnetic sensors; and a feedback control circuit configured to supply the cancellation coils with such a common feedback drive current that the sum of the outputs of the magnetic sensors is equal to a sum of outputs of the magnetic sensors under a zero magnetic field.

A magnetic sensor drive circuit that measures a magnetic field by passing a feedback current, which cancels changes in magnetic flux density using measured magnetic field, through a prescribed coil. The drive circuit includes: a first circuit block which controls the feedback current by using an external power source as a power source; a second circuit block which has an output adjustment circuit adjusting a signal according to the strength of the feedback current to be a signal proportional to the voltage of the power source; a first power source line which supplies the external power source to the first circuit block; a second power source line which supplies the external power source to the second circuit block in parallel to the first power source line; a first low pass filter; and a second low pass filter.

Magnetic field sensors and associated techniques use a Hall effect element in a chopping arrangement in combination with a feedback path configured to reduce undesirable spectral components generated by the chopping.