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Errors can result if the proper correction factor is
not applied by the power meter, as shown below.
Correction Factor (%) Error (dB)
1 0.043
3 0.128
5 0.212
10 0.414
It is desirable to set the power control at or near the
minimum (this varies from −20 to−30 dB, depending
upon model) when establishing P, as this provides
the full ALC range for a power sweep.
The vector error correction available in VNAs is de
-
pendent upon ratioed S-parameter measurements.
Power is measured using a single, unratioed chan-
nel; therefore, when power is being measured error
correction is turned off.
Swept Power Gain
Compression
A swept power test is done at a CW frequency. The
input power will be increased with a step sweep
starting at Pstart and ending at Pstop. The step in-
crement is also user defined. This lets you observe
the conventional Po vs. Pi presentation or a display
of Phase vs. Pi. Figure 8-29 (previous page) illus-
trates this process. The SPGC process is imple-
mented in the 37xxxE by following the procedure
that begins on page 8-43. The test setup required for
this procedure is shown in Figure 8-30 (page 8-42).
Swept Frequency Gain
Compression
This is a manual procedure that provides a normal
-
ized amplifier response as a function of frequency at
Pstart and manually increases the input power
while observing the decrease in gain as the ampli
-
fier goes into compression. This lets you easily ob
-
serve the most critical compression frequency of a
broadband amplifier. The SFGC process is imple
-
mented in the 37xxxE by following the procedure
that begins on page 8-52. The test setup required for
this procedure is shown in Figure 8-30 (following
page).
37xxxE OM 8-41
MEASUREMENTS GAIN COMPRESSION