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, plans have been time and theoretical bit error rate BER Comparison