利用FFT变换，对sine2进行频谱分析，画出频谱图 利用fir源程序对输入波形sine2进行低通滤波，并将结果输出至result.dat -Using FFT transform, spectral analysis of sine2, draw the spectrum graph fir the use of the input waveform sine2 source for low-pass filtering, and the results output to result