Convert digital filter second-order section data to transfer function form
[b,a] = sos2tf(sos)
[b,a] = sos2tf(sos,g)
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
the transfer function that describes a discrete-time system given
sos in second-order section form. The second-order
section format of H(z) is given
sos is an L-by-6 matrix
that contains the coefficients of each second-order section stored
in its rows.
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
second-order section form with gain
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 = 1×5 -2 1 2 4 1
a = 1×5 1 10 0 -10 -1
sos2tf uses the
conv function to multiply all of the
numerator and denominator second-order polynomials together. For higher order filters
(possibly starting as low as order 8), numerical problems due to round-off errors may
occur when forming the transfer function.