User`s guide
Biquadratic Filter
5-38
The SOS matrix parameter specifies the filter coefficients as a second-order
section matrix of the type produced by the
ss2sos and tf2sos functions in the
Signal Processing Toolbox.
This is an L-by-6 matrix whose rows contain the numerator and denominator
coefficients b
ik
and a
ik
of each second-order section in H(z). Use the ss2sos and
tf2sos functions to convert a state-space or transfer-function description of the
filter into the second-order section description used by this block. Note that the
filter uses a value of 1 for the zero-delay denominator coefficients (a
11
to a
1L
)
regardless of the value specified in the
SOS matrix parameter.
The
Initial conditions parameter sets the initial filter states, and can be
specified in the following different forms:
•Scalar to be used for all filter states (v
11
, v
12
, ..., v
1L
, v
21
v
22
, ..., v
2L
) in all
channels. An empty vector,
[], is the same as the scalar value 0.
•Vector of length 2
∗L (row or column) to initialize the filter states for all
channels.
Each pair of elements specifies v
1k
and v
2k
for second-order section k in every
channel.
•Matrix of dimension (2
∗L)-by-N containing the initial filter states for each of
the N channels.
b
11
b
21
b
31
a
11
a
21
a
31
b
12
b
22
b
32
a
12
a
22
a
32
MMMMMM
b
1L
b
2L
b
3L
a
1L
a
2L
a
3L
a
11
a
12
…= a
1L
1===
v
11
v
21
v
12
v
22
… v
1L
v
2L
H
1
(z) H
2
(z) H
L
(z)