正弦函数的自相关函数是与初相位无关的余弦函数。余弦函数的周期与正弦函数的周期相同。周期信号的自相关函数仍然是同频率的周期信号，但不保留原信号的相位信息，并且在τ=0时的自相关函数为自相关函数最大值。-The autocorrelation function of the sine function is the cosine function of the initial phase. The cosine function is the same as the period of the sine function. Periodic signal self correlation function is still with the frequency of the periodic signal, but does not preserve the phase information of the original signal, and in the tau = self correlation function for self correlation function maximum.