说明：  程序实现了基于MATLAB的pi/4 QPSK的仿真,系统在相同条件下，对加噪声和没有噪声的情况，分别画出了它的眼图分析其性能，及已调制信号的时域波形和频谱。
(The program realizes the simulation of pi/4 QPSK based on MATLAB. Under the same condition, the system draws its eye diagram to analyze the performance of the noise and no noise, and the time domain waveform and spectrum of the modulated signal .)