dfilt.df2sos
Discrete-time, second-order section, direct-form II filter
Syntax
Hd = dfilt.df2sos(s)
Hd = dfilt.df2sos(b1,a1,b2,a2,...)
Hd = dfilt.df2sos(...,g)
Hd = dfilt.df2sos
Description
Hd = dfilt.df2sos(s)
returns a
discrete-time, second-order section, direct-form II filter, Hd
, with
coefficients given in the s
matrix.
Hd = dfilt.df2sos(b1,a1,b2,a2,...)
returns a discrete-time, second-order section, direct-form II object,
Hd
, with coefficients for the first section given in the
b1
and a1
vectors, for the second section
given in the b2
and a2
vectors, etc.
Hd = dfilt.df2sos(...,g)
includes a
gain vector g
. The elements of g
are the gains for
each section. The maximum length of g
is the number of sections plus
one. If g
is not specified, all gains default to one.
Hd = dfilt.df2sos
returns a default,
discrete-time, second-order section, direct-form II filter, Hd
. This
filter passes the input through to the output unchanged.
Note
The leading coefficient of the denominator a(1)
cannot be 0.
The resulting filter states column vector is
For filters with more than one section, each section is a separate column in the vector.
Examples
Specify a second-order sections, direct-form II discrete-time filter with coefficients from a sixth order, lowpass, elliptical filter using the following code:
[z,p,k] = ellip(6,1,60,.4); % Obtain filter coefficients [s,g] = zp2sos(z,p,k); % Convert to SOS Hd = dfilt.df2sos(s,g)
Version History
Introduced before R2006a