对一个信号文件导入并进行fft变换，显示图形；对信号是否平稳，周期性，采样点数N，有偏无偏处理的估计效果等都做了处理和显示(A signal file is imported and transformed by FFT to display graphics; whether the signal is stable, periodic, sampling point N, the estimation effect of biased and unbiased processing are processed and displayed.)