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Function List:

C++ API

Function File: [sos, g] = zp2sos (z)

Function File: [sos, g] = zp2sos (z, p)

Function File: [sos, g] = zp2sos (z, p, k)

Function File: sos = zp2sos (...)

Convert filter poles and zeros to second-order sections.

INPUTS:

  • z = column-vector containing the filter zeros
  • p = column-vector containing the filter poles
  • k = overall filter gain factor If not given the gain is assumed to be 1.

RETURNED:

  • sos = matrix of series second-order sections, one per row:
                    sos = [B1.' A1.'; ...; BN.' AN.']
    

    where B1.' = [b0 b1 b2] and A1.' = [1 a1 a2] for section 1, etc. The b0 entry must be nonzero for each section. See filter for documentation of the second-order direct-form filter coefficients Bi and %Ai, i=1:N.

  • g is the overall gain factor that effectively scales any one of the Bi vectors.

If called with only one output argument, the overall filter gain is applied to the first second-order section in the matrix sos.

EXAMPLE:

             [z, p, k] = tf2zp ([1 0 0 0 0 1], [1 0 0 0 0 .9]);
             [sos, g] = zp2sos (z, p, k)
          
           sos =
              1.0000    0.6180    1.0000    1.0000    0.6051    0.9587
              1.0000   -1.6180    1.0000    1.0000   -1.5843    0.9587
              1.0000    1.0000         0    1.0000    0.9791         0
          
           g =
               1

See also: sos2pz, sos2tf, tf2sos, zp2tf, tf2zp.

Package: signal