有一个信号，如果抽样频率，设计一个M点滑动平均系统，要求虑除信号中500Hz的成分，用MATLAB编程仿真结果，确定M的值并画出滑动平均系统的幅频特性图。-Have a signal, if the sampling frequency, to design a M point moving average systems, requirements, in addition to the composition of 500 hz in signal with MATLAB simulatio