The Window Design Method
The basic idea behind the design of linear-phase FIR filters using the window
method is to choose a proper ideal frequency-selective filter [which always has
a noncausal, infinite duration impulse response] and then truncate its impulse
response hd[n] to obtain a linear-phase and causal FIR filter h[n]. To truncate the
impulse response of the ideal filter a time window w[n] is used. Available windows
in Matlab are rectangular [or boxcar in Matlab], bartlett, HAMMING, hanning
This matlab program compares the results of different window design methods for finite impulse response filters (FIRs): the rectangular window, Blackman window, Bartlett window, HAMMING window and the Hanning window.
Use
the fast Fourier transform function fft to analyse following signal. Plot the original signal, and the magnitude of its
spectrum linearly and logarithmically. Apply HAMMING window to reduce the
leakage.
.
The HAMMING window can be coded in Matlab as
for n=1:N
HAMMING(n)=0.54+0.46*cos((2*n-N+1)*pi/N);
end;
where
N is the data length in the FFT.
