中文摘要：

对接收信号进行信噪比估计是许多通信系统要完成的重要工作。具有恒包络特性的MPSK4~号是常见的调制信号，对该类信号提出了一种有效的信噪比估计算法，该算法利用信号包络的均值和方差进行估计，具有计算量小复杂度低的优点。用Matlab仿真了该算法的性能，并与其余几种算法做了比较，结果表明该算法估计准确，有很好的应用价值。

英文摘要：

Estimation of the signal-to-noise ratio（SNR） at the receive side is an important task in many communication sys- tems. The MPSK signal is a common modulation signal, which has constant envelope characteristic. An efficient SNR estimation algorithm for this kind of signal is proposed, which uses the mean value and variance of the signal envelope to estimate, and it has the advantage of small computation and low complexity. The performance of the algorithm is simulated in Matlab, and it is compared with other algorithms. The results indicate that the algorithm estimates the signals accurately and has excellent applica- tion value.