www.pudn.com > MATLAB.rar > exa031101_fftfilt.m
>----------------------------------------------------------------------------
> exa031001_fftfilt.m, for example 3.11.1
> to test fftfilt.m,and to finish the convolution of a long sequence with
> a short sequence by DFT.
>----------------------------------------------------------------------------
clear;
> 用叠接相加法，计算滤波器系数h和输入信号x的卷积
> 其中h为10阶hanning窗，x是带有高斯白噪的正弦信号
h=fir1(10,0.3,hanning(11));> h: a short sequence ; h is the impulse response
N=500;p=0.05;f=1/16; > of a low-pass filter.
u=randn(1,N)*sqrt(p); > u:white noise
s=sin(2*pi*f*[0:N-1]); > s:sine signal
x=u(1:N)+s; > x: a long sequence;
y=fftfilt(h,x); > y=x*h
subplot(211)
plot(x);
subplot(212)
plot(y);