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Examination of a digital FLL system design for SQUIDs
Author(s) -
Oyama Daisuke,
Kobayashi Koichiro,
Simizu Takayuki,
Yoshizawa Masahito,
Uchikawa Yoshinori
Publication year - 2007
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/eej.20526
Subject(s) - slew rate , preamplifier , amplifier , dynamic range , magnetometer , microcontroller , electrical engineering , noise (video) , digital signal processing , physics , electronic engineering , wide dynamic range , engineering , computer science , magnetic field , cmos , quantum mechanics , voltage , artificial intelligence , image (mathematics)
Biomagnetic field measurements in unshielded environments require both large dynamic range and high slew rate. Noise amplitudes at 50 Hz 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 means of 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 the method of design of their amplifiers. The slew rate of a D‐FLL system with optimum amplifiers is 483Φ 0 /s, and its noise level is about 50.0 fT/√ Hz @120 Hz. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 1–6, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20526