Digital Signal Processing Reference
In-Depth Information
Fig. 6.9
Simplified frequency-tunable RF PA circuit
Fig. 6.10
Small-signal
model for the circuit of
Fig.
6.9
The equations for the coupled inductors can be arranged in a Z-parameter matrix
representation:
⎡
⎣
⎤
⎦
z
11
i
X
L1
z
12
i
X
M
V
1
V
2
I
1
I
2
.
=
(6.18)
i
X
M
i
X
L2
z
21
z
22
The small-signal equivalent circuit of Fig.
6.12
is obtained by replacing the cou-
pled inductors of Fig
6.10
by the Z-parameter model of Fig.
6.11
. In order to apply
the SFG/DPI method, we recognize that there are
n
=
6 nodes in this circuit with
=
the ground node excluded. There are also
p
3 voltage sources (
V
in
,i
X
M
I
RF
, and
i
X
M
I
ctrl
). According to [
21
,p.82],
n
−
p
=
3 auxiliary voltage sources must be
added to the circuit (
V
out
,V
x
, and
V
y
).
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