说明：  时频分析中的cohen类中最基本的双线性时频分布式wigner-ville分布，由于在该分布中不含窗函数，因此避免了短时窗傅里叶变换时间分辨率、频率分辨率相互牵制的矛盾
(Time-frequency analysis of the Cohen class of bilinear time-frequency distribution is the most basic Wigner-Ville distribution, because the function in the distribution is not included in the window, so as to avoid the contradiction of short-time window Fourier transform time resolution, frequency resolution of each other)