Coherence Resonance in Chaotic Electronic Circuits

Random fluctuations (or noise) usually constitute a source of disorder and are considered, in general, as detrimental in, e. g., linear information theory, electrical engineering or neurobiology. However, it has been shown in the recent past that the quality of the response of a system can be improved if a right amount of noise is added. One of the most well known examples is that of stochastic resonance [1], by which a system driven by an external signal optimizes its response for an intermediate value of the noise level. This behaviour has been observed in the information transfer in crayfish mechanoreceptors [2], tunnel diodes [3], electronic circuits [4], amongst other systems. More surprisingly, a quasi-periodic signal can be made to appear just by applying a noise source, without the need of an external forcing, to a system that, otherwise, exhibits a non-periodic behaviour. Again, the periodicity of the signal becomes optimal for some intermediate values of the noise intensity. This effect is called coherence resonance [5] and has been observed in excitable [5,6], bistable and oscillatory [7] and optical systems [8]. A similar phenomenon appears in systems close to a limit cycle [9].