Signal Processing Toolbox

sos2tf

Convert digital filter second-order section data to transfer function form.

Syntax

[b,a] = sos2tf(sos)
[b,a] = sos2tf(sos,g)

Description

sos2tf converts a second-order section representation of a given digital filter to an equivalent transfer function representation.

[b,a] = sos2tf(sos) returns the numerator coefficients b and denominator coefficients a of the transfer function that describes a discrete-time system given by sos in second-order section form. The second-order section format of H(z) is given by

sos is an L-by-6 matrix that contains the coefficients of each second-order section stored in its rows.

Row vectors b and a contain the numerator and denominator coefficients of H(z) stored in descending powers of z.

[b,a] = sos2tf(sos,g) returns the transfer function that describes a discrete-time system given by sos in second-order section form with gain g.

Algorithm

sos2tf uses the conv function to multiply all of the numerator and denominator second-order polynomials together.

Example

Compute the transfer function representation of a simple second-order section system.

sos = [1  1  1  1  0 -1; -2  3  1  1 10  1];
[b,a] = sos2tf(sos)
b =
   -2     1     2     4     1
a =
    1    10     0    -10    -1 

See Also

latc2tf	Lattice filter to transfer function conversion.
sos2ss	Convert digital filter second-order sections data to state-space form.
sos2zp	Convert digital filter second-order sections data to zero-pole-gain form.
ss2tf	Convert state-space data for a filter to transfer function form.
tf2sos	Convert transfer function data for a digital filter to second-order sections form.
zp2tf	Convert zero-pole-gain data for a filter to transfer function form.

sos2ss

sos2zp