用Fourier变换求取信号的功率谱---周期图法用Fourier变换求取信号的功率谱---分段周期图法用Fourier变换求取信号的功率谱---welch方法功率谱估计----多窗口法(multitaper method ,MTM法)功率谱估计----最大熵法(maxmum entmpy method,MEM法)功率谱估计----多信号分类法(multiple signal classification,music法)Fourier transform to strike a signal to the