Signal Toolkit - sos2tf

Function File: [b, a] = sos2tf (sos)

Function File: [b, a] = sos2tf (sos, g)

Convert series second-order sections to transfer function.

INPUTS:

• sos = matrix of series second-order sections, one per row:

   sos = [B1.' A1.'; ...; BN.' AN.']
   

  where B1.' = [b0 b1 b2] and A1.' = [a0 a1 a2] for section 1, etc.

  a0 is usually equal to 1 because all 2nd order transfer functions can be scaled so that a0 = 1. However, this is not mandatory for this implementation, which supports all kinds of transfer functions, including first order transfer functions. See filter for documentation of the second-order direct-form filter coefficients Bi and Ai.

• g is an overall gain factor that effectively scales the output b vector (or any one of the input Bi vectors). If not given the gain is assumed to be 1.

RETURNED: b and a are vectors specifying the analog or digital filter H(s) = B(s)/A(s) or H(z) = B(z)/A(z). See filter for further details.

See also: tf2sos, zp2sos, sos2pz, zp2tf, tf2zp.