说明：  运用仿真抽样信号的频谱, 分析满足不同条件下的抽样情况、验证奈奎斯特抽样定理不同量化电平情况下的信噪
(The use of simulation sampling frequency spectrum, analyzing a sample under different conditions to meet the situation, verify the Nyquist sampling theorem under different quantization level of the signal to noise)