时变系统的频谱扩展，（信道是平坦的）仿真结果为：滤波后高斯过程的功率谱密度和由滤波器产生的相关高斯序列的时域值-Time-varying system, spread spectrum, (the channel is flat) simulation results as follows: the filtered Gaussian process power spectral density and produced by the filter related to the value of time-domain Gaussian sequence