FFT-based FIR Filter is a unit to perform the finite impulse responce filter based on the Fast Fourier Transform (FFT). It performs the convolution of the unlimited signal sequence with the synthesized impulse responce of the length of Ni=N/2 samples

通过计算分析输出信号的自相关函数利用基于自相关函数的方法来估计衰减系数和延迟，并利用快速傅里叶变换将回波信号滤除回声，得到原声音信号，同时根据延迟估计反射物的距离。-Analysis by calculating the autocorrelation function of the output signal utilizing the autocorrelation function based method to estimate the attenuation coefficient a

图象变换　从傅立叶变换的频谱图中可以看出，提高分辨率以后，其边缘更加平滑，锯齿状明显减弱。但其傅立叶变换后的图像没有明显改变。 3》DC系数移动 其系数移动以后，频谱分量都集中到了频谱的中间。 4》滤波器频率响应(Image transform,As can be seen from the spectrum diagram of Fourier transform, the edge is smoother and the serrated is significantly reduc