dfilt.df1sos (Signal Processing Toolbox)

Construct a discrete-time, second-order section, direct form I filter object

Syntax

Hd = dfilt.df1sos(s)
Hd = dfilt.df1sos(b1,a1,b2,a2,...)
Hd = dfilt.df1sos(...,g)

Description

Hd = dfilt.df1sos(s) returns a discrete-time, second-order section, direct form I filter object, Hd, with coefficients given in the s matrix.

Hd = dfilt.df1sos(b1,a1,b2,a2,...) returns a discrete-time, second-order section, direct form I filter 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.df1sos(...,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.df1sos returns a default, discrete-time, second-order section, direct form I filter object, Hd. This filter passes the input through to the output unchanged.

Note If a(1) is not equal to 1, the 1/a(1) block is included as shown below. If a(1) is equal to 1, the 1/a(1) block is replaced by a direct connection.

Examples

Specify a second-order section, direct form I dfilt object for a Butterworth filter converted to second-order sections, with the following code:

[z,p,k] = butter(30,0.5);
[s,g] = zp2sos(z,p,k);
Hd = dfilt.df1sos(s,g)
Hd = 
    FilterStructure: 'Direct form I, second-order-sections'
          sosMatrix: [15x6 double]
        ScaleValues: 2.5160e-0087

dfilt.df1 dfilt.df1t