Attenuating dead-band for digital closed-loop FOCT based on stochastic resonance effect

For the sake of attenuating dead-band nonlinearity in digital closed-loop fiber-optic current transformers (FOCT), a signal processing model based on stochastic resonance effect (SRE) was proposed based on theoretic analysis. A zero-averaged stochastic noise with normal probability distribution function and adaptable bandwidth was produced by operating thermal noise from a resistor as noise source and processing this noise through adequate circuit. Secondly, introducing this processed noise into as an inputting signal of the A/D converter in the closed feedback loop. Then, an effective stochastic resonance effect was investigated by varying noise intensity, bandwidth and the sampling frequency for A/D converter to get the matching working point. Therefore, the signal to noise ratio (SNR) of the FOCT should be improved and attenuation on dead-band nonlinearity was realized. Finally, theoretic analysis for the proposed model was verified by experimental and simulation results. In addition, this SRE-based method might be in appliance for other closed-loop weak signal detection systems.