Biomagnetic field measurement device, flux locked loop unit, and biomagnetic field measurement system

An full locked loop (FLL) unit for measuring a biomagnetic field in accordance with a voltage signal output from a SQUID sensor, the FLL unit comprising:

• an amplifier configured to amplify a voltage signal output from the SQUID sensor;
• an analog-to-digital (AD) converter configured to convert the voltage signal amplified by the amplifier into a digital signal;
• a digital multiplier configured to multiply, in accordance with an adjustment value, a signal value of the digital signal converted by the AD converter by a multiplier, the multiplier corresponding to the adjustment value to be set from outside;
• a digital integrator configured to integrate the signal value of the digital signal multiplied by the digital multiplier to generate integrated data;
• a digital-to-analog (DA) converter configured to convert the integrated data generated by the digital integrator into a voltage signal;
• a voltage-to-current converter configured to convert the voltage signal converted by the DA converter into a current signal;
• and
• a coil configured to feed back the current signal converted by the voltage-to-current converter to the SQUID sensor as a magnetic field, and
• wherein the digital multiplier is configured to function as an adjustment device configured to adjust a loop gain of the FLL unit.

An FLL unit for measuring a biomagnetic field according to a voltage signal output from a SQUID sensor, the FLL unit comprising:

• a first amplifier configured to amplify a voltage signal output from the SQUID sensor;
• a second amplifier configured to amplify the voltage signal amplified by the first amplifier at any one of a plurality of amplification factors corresponding to a first adjustment value that can be set from outside;
• an analog-to-digital (AD) converter configured to convert the voltage signal amplified by the second amplifier into a digital signal;
• a digital shifter configured to perform shift processing on a signal value of the digital signal converted by the AD converter by any one of a plurality of shift amounts, the plurality of shift amounts corresponding to a second adjustment value to be set from outside;
• a digital integrator configured to integrate the signal value of the digital signal subjected to the shift processing by the digital shifter to generate integrated data;
• a digital-to-analog (DA) converter configured to convert the integrated data generated by the digital integrator into a voltage signal;
• an amplitude adjuster configured to convert a full scale of an output of the DA converter to any one of a plurality of full scales corresponding to a third adjustment value that can be set from outside to adjust to any one of a plurality of amplitudes;
• a voltage-to-current converter configured to convert the voltage signal whose voltage magnitude is changed by converting the full scale by the amplitude adjuster into a current signal;
• and
• a coil configured to feed back the current signal converted by the voltage-to-current converter to the SQUID sensor as a magnetic field, and
• wherein the second amplifier, the digital shifter, and the amplitude adjuster are each configured to function as the adjustment device configured to adjust a loop gain of the FLL unit.