A center frequency adjustable narrow band filter for the detection of weak single frequency signal.
We describe and implement a center frequency adjustable narrow band filter based on the crystal filter for the detection of weak single frequency signal. It is formed by a multiplier, a direct digital frequency synthesizer, a multi-stage crystal bandpass filter, and a micro control unit which is used to set the center frequency of the filter. A theoretical study is proposed and experimentally validated. The test results show that the 3 db and 20 db bandwidths are 0.84 Hz and 2.73 Hz, respectively, and the filter system can effectively detect the signal with amplitude below 1 μV and a frequency which ranges from 10 Hz to the frequency that is mainly limited by the components applied.
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
Yunhong
Y
Xin
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
ZhenMing
Z
Xiang
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
LeMing
L
Dong
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
Bing
B
Zhu
School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
Hui
H
Cao
School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
Yu
Y
Fang