Digital Signal Processing Reference
In-Depth Information
Fig. 10.5
Unmatched power amplifier SOLT measurement (
S
21
and
S
12
)
Table 10.1
Summary of the
measured SOLT S and
Z parameters for the
unmatched power amplifier at
5.2 GHz
Parameter
Value
Parameter
Value
S
11
0
.
69
∠ −
136°
Z
11
(
)
10
.
6
−
i19
.
4
S
22
0
.
62
∠ −
134°
Z
22
(
)
13
.
7
−
i19
.
8
S
11
(dB)
−
3.22
S
21
(dB)
2.43
S
22
(dB)
−
4.15
S
12
(dB)
−
22.5
For this example, it is considered that a conjugate match at both input and out-
put is desired so that the amplifier can attain the maximum power gain. From
Figs.
10.3
and
10.4
, it can be noticed that the power amplifier is unmatched at
5.2 GHz, resulting in a power gain of 2.4 dB at this frequency (see Table
10.1
for a
summary of these results). The objective, hence, is to bring the markers at this fre-
quency the closest possible to the center of the Smith chart, where a perfect match
takes place.
10.3.3 Third Step
The network analyzer is then calibrated with the TRL standards fabricated in step 1.
The measured S parameters (
S
trl
) are now referenced to the DUT reference planes
(refer to Fig.
10.1
) and the results are shown in Fig.
10.6
. Comparison of this figure
with Figs.
10.3
and
10.4
reveals that, at 5.2 GHz, the embedding networks change
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