加性高斯白噪声信道条件下的QPSK信号的调制与解调，观察了调制信号的功率谱图，输入输出信号图，已经时间误码率图与理论误码率的比较-Additive white Gaussian noise channel under the conditions of the QPSK signal modulation and demodulation, observed power spectra of modulated signals, input and output signal maps, pla