中文说明：
基于matlab，计算信号功率谱，调用了高阶谱分析工具箱的函数 bispecd 和 bispeci计算信号的双谱。
English Description：
Based on MATLAB, the power spectrum of signal is calculated, and bispectrum of signal is calculated by calling bispecd and bispeci functions of high-order spectrum analysis toolbox.