Digital SQUID Flux-Locked Loop for Accurate Flux Quantum Measurement
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Solution Overview
Problem
The existing magnetic field measuring apparatus using a superconducting quantum interference device (SQUID) and digital flux locked loop (FLL) circuit faces challenges in accurately measuring flux quantum due to variations in electrical characteristics, leading to nonlinear measurement characteristics and reduced accuracy.
Innovation Solution
A magnetic field measuring apparatus and flux quantum calculating method that includes a digital flux locked loop circuit with an analog-to-digital converter, digital integrator, digital-to-analog converter, voltage-to-current converter, and a coil to generate a magnetic field, allowing for accurate calculation of flux quantum by integrating and converting signals to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a digital FLL circuit is used to measure magnetic field, then ease of data processing and channel consistency are improved, but measurement accuracy of flux quantum deteriorates due to electrical characteristic variations
Solution Approach 1:
The patent applies preliminary action by measuring the flux quantum in advance using the digital FLL circuit before actual magnetic field measurements. This preliminary measurement allows the system to establish a reference value that accounts for electrical characteristic variations, which is then used to correct subsequent measurements, thereby maintaining accuracy while benefiting from digital processing ease
Solution Approach 2:
The patent changes the parameter being measured from direct magnetic field values to flux quantum values that are normalized against electrical characteristic variations. By measuring the flux quantum (which represents one period of periodic change) and using it as a reference, the system compensates for variations in electrical characteristics, thereby maintaining measurement accuracy across multiple channels
2Difficulty of detecting and measuring
If flux quantum measurement is performed using periodic voltage change, then measurement capability is improved, but measurement accuracy deteriorates due to non-constant output value change
Solution Approach 1:
The patent applies feedback by using the measured flux quantum value to correct subsequent measurements. The system continuously monitors the periodic voltage changes, measures the flux quantum, and uses this information to adjust and correct measurement accuracy, compensating for the non-constant output value changes in the analog-to-digital converter
Solution Approach 2:
The patent changes the approach from measuring absolute voltage values to measuring the periodic change in voltage values (flux quantum). By focusing on the periodic variation rather than absolute values, the system overcomes the non-constant output characteristic of the analog-to-digital converter, as the periodic change remains consistent even when absolute values vary
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
This solution enhances the accuracy of flux quantum measurement and improves the dynamic range of the digital FLL circuit, reducing measurement errors and enabling precise biomagnetic field measurements across multiple channels.
Implementation Method 1
a superconducting quantum interference device (SQUID) that is a superconductor ring having a Josephson junction
Implementation Method 2
a first coil configured to generate the magnetic field received by the superconducting quantum interference device, based on the current output from the first voltage-to-current converter
Data Source
AI summary
A magnetic field measuring apparatus includes a digital FLL circuit including ADC that converts a periodically changing voltage output from a SQUID according to a change in a magnetic field into a digital value, a digital integrator that integrates the digital value output from the ADC, a DAC that converts an integrated value output from the digital integrator into a voltage, a converter that converts the voltage output from the DAC into a current, and a coil that generates the magnetic field received by the SQUID, based on the current output from the converter. A calculating device calculates a digital value indicating a flux quantum based on the digital value output from the ADC when the ADC converts the periodically changing voltage output from the SQUID upon receiving the magnetic field generated by a current that is obtained by converting a voltage generated by a voltage generator.