Feedback Loop Low Pass Filter Magnetometer

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Solution Overview

Problem

Conventional magnetic field measurement systems, particularly those using optically pumped magnetometers, face challenges in accurately measuring low amplitude magnetic fields in unshielded environments due to interference from ambient background magnetic fields, requiring costly and impractical cryogenic cooling and large, immobile setups.

Innovation Solution

A magnetic field measurement system incorporating a feedback loop filter with low pass filters and PID elements to compensate for low-frequency magnetic field variations, allowing for the rejection of high-frequency noise and enabling measurement of low amplitude fields in wearable, cost-effective devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional magnetic field measurement systems use unshielded environments to enable wearable applications, then device portability and cost are improved, but measurement precision deteriorates due to ambient magnetic field interference

Engineering Contradiction:

Improvewearable capabilityVSAvoidlow amplitude magnetic field detection

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a feedback loop where the magnetometer continuously measures the background magnetic field, and the system generates compensating magnetic fields through coils to nullify detected variations. This closed-loop feedback mechanism enables the system to operate in unshielded environments while maintaining measurement precision by actively canceling ambient interference.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces an intermediary processing stage between the magnetometer and the measurement output, where signal processing techniques and filtering are applied to separate neural signals from background interference. This intermediary processing enables accurate detection of low-amplitude neural signals despite the presence of ambient magnetic fields.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If feedback loops compensate for low-frequency magnetic field variations, then measurement precision for neural signals is improved, but device complexity increases due to additional filtering components

Engineering Contradiction:

Improveneural signal detectionVSAvoidfeedback circuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent utilizes programmable digital filters with adjustable cutoff frequencies and transfer functions that can be modified based on the specific measurement requirements. This parameter adjustability allows the system to optimize performance for different neural signal frequencies without requiring hardware redesign, thereby managing complexity while maintaining precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The feedback circuit is designed to handle multiple frequency ranges and measurement conditions using a unified architecture. The same feedback loops and filtering mechanisms serve both low-frequency drift compensation and high-frequency neural signal enhancement, reducing overall system complexity compared to having separate dedicated circuits for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the dynamic range of optically pumped magnetometers to facilitate the measurement of neural signals outside magnetically shielded rooms, separating low-frequency noise from high-frequency neural signals, thus enabling wearable and commercially viable magnetoencephalography applications.

Implementation Method 1

at least one magnetometer having a vapor cell, a light source to direct light through the vapor cell

Methodology Applied

Scientific EffectOptical pumping:

Implementation Method 2

a detector to receive light directed through the vapor cell

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 3

at least one magnetic field generator disposed adjacent the vapor cell and configured to modify a magnetic field experienced by the vapor cell

Methodology Applied

Scientific EffectMagnetic field generation: Electromagnet

Implementation Method 4

The first low pass filter rejects magnetic field variations having a frequency higher than the first cutoff frequency

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS11480632B2Magnetic field measurement systems and methods employing feedback loops with a loops with a low pass filter

Publication Date: 2022.10.25 HI LLC

AI summary

A magnetic field measurement system includes at least one magnetometer having a vapor cell, a light source to direct light through the vapor cell, and a detector to receive light directed through the vapor cell; at least one magnetic field generator disposed adjacent the vapor cell; and a feedback circuit coupled to the at least one magnetic field generator and the detector of the at least one magnetometer. The feedback circuit includes a first feedback loop that includes a first low pass filter with a first cutoff frequency and a second feedback loop that includes a second low pass filter with a second cutoff frequency. The first and second feedback loops are configured to compensate for magnetic field variations having a frequency lower than the first or second cutoff frequency, respectively.