To improve the S/N ratio by overcoming the problem, wherein the S/N ratio gain becomes smaller if the noise intensity is smaller than an appropriate value, when the S/N ratio is improved by using a probability resonance phenomenon.
In an S/N characteristics improving device 1 which acquires an input signal Vin mixed with noise, and acquires an output signal Vout by input of the input signal into a nonlinear function device and making a probability resonance phenomenon to occur, a logistic function, a sigmoid function, or a hyperbolic tangent function is used as the nonlinear function. When these functions are used and when noise is not large, the output changes linearly in response to the magnitude of the input signal, and the S/N ratio gain can exceed at least one. While, if the magnitude of the noise is appropriate, the S/N ratio is greatly improved as the probability resonance phenomenon occurs efficiently by a nonlinear threshold characteristic. Consequently, the S/N ratio (SNRout) of the output signal Vout can be made higher than the S/N ratio (SNRin) of the input signal Vin, in a wide range from a stage in which the noise mixed in the input signal Vin is weak.
Daisuke Nagano
Kentaro Fujii