说明：  该算法是经典的信噪比估计算法——误差矢量幅值法，通过计算接收信号中同相分量和正交分量的二、四阶矩，该算法能够很好的估计信号的信噪比
(The algorithm is a classic signal to noise ratio estimation algorithm- the error vector magnitude method, by calculating the received signal with the phase component and quadrature component of the second, fourth-order moment, the algorithm can estimate a very good signal to noise ratio)