说明：  利用Elman网络对信号的幅度进行检测，能够正确输出时变信号的幅度值。本源码中假设信号由幅度分别为1和2的正弦信号交替变化构成
(Elman network use the magnitude of the signal detection, can correct the output signal range of time-varying value. Assuming the source signal by the magnitude of 1 and 2 constitute a change in the turn of sinusoidal signal)