Design of a Narrowband Adaptable Filter in Low-Frequency Domain

Abstract

To improve the Signal to Noise Ratio and the precision of data acquisition systems in the condition of broad bandwidth, an adaptive narrow-band filter circuit has been designed for obtaining weak signals in low-frequency domain. And the problems of classic filter circuits, such as wave form distortion and suffering from non-linearity of varactors, can be solved by the novel design in replacing varactor with voltage control capacitor. Simultaneously, by improving LRC filter circuit, our designs also can increase quality factor in traditional RC filter circuit. Therefore, this design has great advantages over classic filter circuits for its narrow frequency band, high quality factor and low signal deformation. The above properties of this circuit can make it used widely in removing noise for modulation and acquisition circuits with high precision, and can be used to obtain accurate band-pass filtering in low frequency bands, which has been verified by experiments showing superior advantages of improving the SNR and filtering effects.