中文说明：
线性调频信号的维格纳分布，伪WVD，平滑WVD比较，并且给出维格纳分布三维表示。方便学习LFM信号。
English Description：
Wigner distribution, pseudo WVD and smooth WVD of LFM signal are compared, and three-dimensional representation of Wigner distribution is given. It is convenient to learn LFM signal