单频信号经过多径时变信道后，输出信号的包络随时间随机起伏，输出信号的频谱从冲激谱变成一个窄带频谱。径数位20，变化频率从0—2HZ随机均匀抽取。-Single-frequency signal through time-varying multipath channel, the output signal envelope random fluctuations over time, the output signal from the impulse of the spectrum into a narrow-band spectrum spectrum. Digital Drive 20, changes in frequency from 0-2HZ uniform random samples.