Title :
Analysis of first-order feedback loop with lock-in amplifier
Author :
Nakanishi, Masakazu ; Sakamoto, Yasuhiko
Author_Institution :
Electron. Meterol. Sect., Electrotech. Lab., Ibaraki, Japan
fDate :
8/1/1996 12:00:00 AM
Abstract :
A dc-SQUID (Superconducting QUantum Interference Device) is usually operated in a first order feedback loop with a lock-in amplifier and this configuration is called “lock-in flux locked loop”. The system response of this configuration was studied. The effect of the phase difference between the modulator and demodulator of the lock-in amplifier was quantitatively examined. The system is stable as long as the phase difference does not exceed π/2. The system response is given as a function of the phase difference. Transfer gains from two input sites to the output were calculated. Analyzes were verified to be correct by experiment
Keywords :
SQUIDs; feedback amplifiers; DC-SQUID; demodulator; first-order feedback loop; flux locked loop; lock-in amplifier; modulator; phase difference; transfer gain; Amplifiers; Circuit noise; Demodulation; Feedback loop; Frequency modulation; Geophysical measurements; Magnetic field measurement; Magnetic flux; Phase modulation; Signal to noise ratio;
Journal_Title :
Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on
