Fir filter design using matlab
Design by windowing
The MATLAB function
fir1() designs
conventional lowpass, highpass, bandpass, and bandstoplinear-phase FIR filters based on the windowing
method. The command
b = fir1(N,Wn)
returns in vector
b the impulse response of a
lowpass filter of order
N . The cut-off
frequency
Wn must be between 0 and 1 with 1
corresponding to the half sampling rate.
The command
b = fir1(N,Wn,'high')
returns the impulse response of a highpass filter of order
N with normalized cutoff frequency
Wn .
Similarly,
b = fir1(N,Wn,'stop') with
Wn a two-element vector designating the
stopband designs a bandstop filter.
Without explicit specification, the
Hamming
window is employed in the design. Other
windowing functions can be used by specifying thewindowing function as an extra argument of the function.
For example, Blackman window can be used instead by thecommand
b = fir1(N, Wn, blackman(N)) .
Parks-mcclellan fir filter design
The MATLAB command
b = remez(N,F,A)
returns the impulse response of the length
N+1 linear phase FIR filter of order
N designed
by Parks-McClellan algorithm. F is a vector of frequencyband edges in ascending order between 0 and 1 with 1
corresponding to the half sampling rate. A is a realvector of the same size as F which specifies the desired
amplitude of the frequency response of the points
(F(k),A(k)) and
(F(k+1),A(k+1)) for odd
k . For odd
k , the bands
between
F(k+1) and
F(k+2) is
considered as transition bands.