说明：  实现能量检测仿真，由main函数进行能量检测，psk_2实现BPSK调制，pdsnr计算出理论值，最后由main给出理论与仿真之间的画图比较。
(Achieve energy detection simulation, the main function of the energy detection, psk_2 achieve modulation BPSK, pdsnr calculate the theoretical value, and finally given by the main draw between theory and simulation comparison.)