Shao-Bo Qu,1,2,[1]) Olivier Robert,1,[2]) Philippe Lognonné,1 Ze-Bing Zhou,2 and Shan-Qing Yang2
1Institut
de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, CNRS,
F-75013 Paris, France
2MOE Key Laboratory of Fundamental Physical Quantities
Measurement, School of Physics, Huazhong University of Science and Technology,
Wuhan 430074, People’s Republic of China
Low frequency 1/f noise is one of the key limiting factors
of high precision measurement instruments. In this paper, digital correlated
double sampling is implemented to reduce the offset and low frequency 1/f noise
of a data acquisition system with 24-bit sigma delta (Σ-Δ) ADC. The input
voltage is modulated by cross-coupled switches, which are synchronized to the
sampling clock, and converted into digital signal by ADC. By using a proper
switch frequency, the unwanted parasitic signal frequencies generated by the
switches are avoided. The noise elimination processing is made through the
principle of digital correlated double sampling, which is equivalent to a time
shifted subtraction for the sampled voltage. The low frequency 1/f noise
spectrum density of the data acquisition system is reduced to be flat down to the
measurement frequency lower limit, which is about 0.0001 Hz in this paper. The
noise spectrum density is eliminated by more than 60dB at 0.0001 Hz, with a residual
noise floor of (9±2) nV/Hz1/2 which is limited by the intrinsic
white noise floor of the ADC above its corner frequency.
[1]) Now at MOE Key Laboratory of
Fundamental Physical Quantities Measurement, School of Physics, Huazhong
University of Science and Technology, Wuhan 430074, People’s Republic of China. Electronic mail: qushaobo@hust.edu.cn
