Convert digital filter second-order section data to transfer function form
Transfer Function Representation of a Second-Order Section System
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
sos — Second-order section representation
Second-order section representation, specified as a matrix.
is an L-by-6 matrix
whose rows contain the numerator and denominator coefficients bik and aik of the second-order sections of H(z):
[2 4 2 6 0 2;3 3 0 6 0 0] specifies a third-order
Butterworth filter with normalized 3 dB frequency 0.5π
Complex Number Support: Yes
g — Overall system gain
Overall system gain, specified as a real scalar.
a — Transfer function coefficients
Transfer function coefficients, returned as row vectors.
a contain the numerator and denominator coefficients of
H(z) stored in descending powers of
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.