用matlab仿真随机信号的调制解调，并绘制调制信号、已调信号、解调信号、输出信号的频谱、功率谱密度，自相关函数-Matlab simulation of random signals with modulation and demodulation, and draw the modulation signal, modulated signal, the demodulated signal, the output signal spectrum, power spectral density, autocorrelation function