Kaiser window FIR filter design estimation parameters
[n,Wn,beta,ftype] = kaiserord(f,a,dev)
[n,Wn,beta,ftype] = kaiserord(f,a,dev,fs)
c = kaiserord(f,a,dev,fs,'cell
')
kaiserord
returns a filter order n
and beta
parameter
to specify a Kaiser window for use with the fir1
function.
Given a set of specifications in the frequency domain, kaiserord
estimates
the minimum FIR filter order that will approximately meet the specifications. kaiserord
converts
the given filter specifications into passband and stopband ripples
and converts cutoff frequencies into the form needed for windowed
FIR filter design.
[n,Wn,beta,ftype] = kaiserord(f,a,dev)
finds
the approximate order n
, normalized frequency band
edges Wn
, and weights that meet input specifications f
, a
,
and dev
. f
is a vector of band
edges and a
is a vector specifying the desired
amplitude on the bands defined by f
. The length
of f
is twice the length of a
,
minus 2. Together, f
and a
define
a desired piecewise constant response function. dev
is
a vector the same size as a
that specifies the
maximum allowable error or deviation between the frequency response
of the output filter and its desired amplitude, for each band. The
entries in dev
specify the passband ripple and
the stopband attenuation. You specify each entry in dev
as
a positive number, representing absolute filter gain (not in decibels).
Note
If, in the vector |
fir1
can use the resulting
order n
, frequency vector Wn
,
multiband magnitude type ftype
, and the Kaiser
window parameter beta
. The ftype
output
argument is intended for use with fir1
;
it is equal to 'high'
for a highpass filter and 'stop'
for
a bandstop filter. For multiband filters, it can be equal to 'DC-0'
when
the first band is a stopband (starting at f = 0) or 'DC-1'
when
the first band is a passband.
To design an FIR filter b
that approximately
meets the specifications given by kaiser
parameters f
, a
,
and dev
, use the following command.
b = fir1(n,Wn,kaiser(n+1,beta),ftype,'noscale')
[n,Wn,beta,ftype] = kaiserord(f,a,dev,fs)
uses
a sampling frequency fs
in Hz. If you don't specify
the argument fs
, or if you specify it as the empty
vector []
, it defaults to 2 Hz,
and the Nyquist frequency is 1 Hz. You can use this
syntax to specify band edges scaled to a particular application's
sampling frequency. The frequency band edges in f
must
be from 0 to fs
/2.
c = kaiserord(f,a,dev,fs,'
is
a cell-array whose elements are the parameters to cell
')fir1
.
Note
In some cases, Results are inaccurate if the cutoff frequencies are near 0
or the Nyquist frequency, or if |
[1] Kaiser, James F. "Nonrecursive Digital Filter Design Using the I_{0}-sinh Window Function." Proceedings of the 1974 IEEE International Symposium on Circuits and Systems. 1974, pp. 20–23.
[2] Digital Signal Processing Committee of the IEEE Acoustics, Speech, and Signal Processing Society, eds. Selected Papers in Digital Signal Processing. Vol. II. New York: IEEE Press, 1976, pp. 123–126.
[3] Oppenheim, Alan V., Ronald W. Schafer, and John R. Buck. Discrete-Time Signal Processing. Upper Saddle River, NJ: Prentice Hall, 1999.