cbl

代码说明：

   利用fft()进行快速傅立叶变换，得到频谱，画出正弦函数及其频谱  找出频谱中使得Y轴取最大值时的估计频率记为ft  加入白噪声，绘出信噪比和均方误差的关系曲线 ( using fft () for fast Fourier transformation, spectrum, to draw the sine function and its spectrum  find the spectrum makes the Y-axis maximum value when the estimated frequency is denoted by ft  adding white noise, SNR plot and mean square error curve)