sampling

代码说明：

  演示采样定理，时域采样，频谱周期延拓同时演示采样频率小于2*fc时，产生的混叠效应。可作函数应用(Demonstration sampling theorem, time-domain sampling, the spectrum at the same time cycle extension demonstration sampling frequency is less than 2* fc, the resulting aliasing effect. Function can be used for applications)