Stochastic Resonance in Saturation Nonlinearities

The majority of studies in saturation nonlinearities making use of periodic input signals and signal noise ratio (SNR) measures indicate the possibility of SNR gains due to stochastic resonance (SR). The paper points out that for such circumstances, the SNR measure discards some statistical information due to the saturation. When the shape of input signals is required at the output of the saturation nonlinearities, SNR is not an appropriate measure even for the case of narrowband or periodic signals. A statistical measure based on deflection ratio is proposed, and detectability at the output of the saturation nonlinearities is also considered simultaneously. Although SNR amplification has been shown to exist for periodic input signals, somewhat paradoxically, a gain larger than unity cannot be obtained as far as the deflection ratio or detectability is concerned. The underlying mechanism is revealed, and it is showed that the situations where the SNR gains occur are limited in their potential usefulness.