Consider a two-channel analysis filter bank (Figure 1).
What is the transpose of this system? We can find it by finding
first the matrix representation. To find the matrix
representation, note that we already know the matrix
representation of the two branches individually.
s
0
=
Q
0
x
s
0
Q
0
x
s
1
=
Q
1
x
s
1
Q
1
x
So total system can be represented as a single matrix:
s
0
s
1
=
Q
0
x
Q
1
x=
Q
0
Q
1
x=Qx
s
0
s
1
Q
0
x
Q
1
x
Q
0
Q
1
x
Q
x
where
Q=
Q
0
Q
1
Q
Q
0
Q
1
The transpose of the two-channel analysis filter bank is therefore:
QT=
Q
0
T
Q
1
T
Q
Q
0
Q
1
and
y=QT
s
0
s
1
=
Q
0
T
Q
1
T
s
0
s
1
=
Q
0
T
s
0
+
Q
1
T
s
1
y
Q
s
0
s
1
Q
0
Q
1
s
0
s
1
Q
0
s
0
Q
1
s
1
This corresponds to the diagram in Figure 2: