SQUID用デジタルFLLシステムの設計法に関する検討 [in Japanese] Examination of a Digital FLL System Design for SQUIDs [in Japanese]
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Biomagnetic field measurements in unshielded environment require both large dynamic range and high slew rate. Noise amplitudes at 50Hz and under 10 Hz of significantly more than 1μT are not at all exotic in an industrial or a hospital environment. A digital FLL (D-FLL) system for a SQUID magnetometer has high resolution and large dynamic range of magnetic field. Slew rate of a D-FLL system by using a double-counter is limited by its digital feedback loop. It can increase the slew rate that optimum feedback loop gain is divided into an analog preamplifier and a digital amplifier on a microcontroller. We show design method of their amplifiers. The slew rate of a D-FLL system with optimum amplifiers is 483 Φ<sub>0</sub>/s , and its noise level is about 50.0fT√Hz@120Hz.
- IEEJ Transactions on Fundamentals and Materials
IEEJ Transactions on Fundamentals and Materials 126(5), 300-305, 2006-05-01
The Institute of Electrical Engineers of Japan