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.

Examples

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 
  

Algorithm

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

See Also

latc2tf, sos2ss, sos2zp, ss2tf, tf2sos, zp2tf

sos2ss

sos2zp