级联双稳系统的随机共振特性

研究了两个双稳系统级联的随机共振特性，由于第一级双稳系统的作用是将白噪声转变为色噪声，因此它是整个级联系统中最重要的环节，以后各级系统近似按洛伦兹分布将噪声能量不断向低频区域集中，从而减弱高频抖动，突出波形的基本轮廓.频谱中信号谱峰随噪声强度的变化规律表明，级联双稳系统只在有限的低频范围内，通过一定量的噪声强度来增强信号频率处的谱峰高度，如果前一级系统未达到随机共振状态，那么其后一级并不能对前一级的输出进行“优化”而形成随机共振.级联双稳系统级数的增加，会使噪声能量集中的低频区域变窄，信号谱峰易被压缩和受到噪声干扰.虽然可以用二次采样方法进行改善，但其改善程度有限.因此对于信号检测而言，使用单级双稳系统即可. 关键词： 级联双稳系统 随机共振 频谱 噪声

Stochastic resonance behaviors of bistable systems connected in series

The stochastic resonance(SR) characteristics of two bistable systems connected in series have been investigated. It is deduced that the first bistable system of the cascaded system is most important because of its converting a white noise into a color one, and the subsequent bistable systems continuously concentrate noise energy into low frequency area in terms of Lorentzian distribution, which weakens the high frequency dithering of the last output waveform and outlines the basic shape of the wave. The law of the signal spectral amplitude varying with noise intensity indicates that within a limited low frequency band, the cascaded system is able to promote the height of the signal spectral spike by a certain amount of noise. If the former of the cascaded system does not stay in SR, the latter could not optimize the former output to become a SR state. With the increase of the number of the bistable systems in the cascaded system, the low frequency area where most of the noise energy is collected will be narrowed gradually, and hence the signal peak is easily reduced and submerged in noise. For this case, in spite of using the twice-sampling technique to improve the signal spectral spike, the improvement is limited. Therefore, a single bistable system is effective for signal detection.