Nautel NX300, Operation And Maintenance Manual

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NX300 Operations and Maintenance Manual Operating the transmitter
Issue 3.0 2012-11-01 Page 2-101
AM-PM Correction
The
AM-PM Correction
page (see Figure 2.77 ) allows you to load or capture a set of AM-PM
correction curves. You can
Load
or
Delete
curves in this list; you can also capture a curve. When you
select
Capture
, the AM-PM Correction instrument panel is displayed. Press
Done
to capture the
curve, type a name for the curve, then press
Save
(or
Cancel
).
Value changes are not typically required.
AM-PM curves correct for a type of non-linearity where a change in input amplitude causes a change
in phase. By applying a test signal and monitoring the output of the transmitter, the exciter will
generate a table of values defining the required phase offset versus input signal level in an attempt to
find the inverse curve to the AM-PM non-linearity, and provide a more linear amplifier. Applying the
proper AM-PM correction will result in better spectral performace in digital modes of operation.
Figure 2.77: Precorrection AM-PM
CAUTION:
Making changes to the AM-PM Correction curves automatically places the
transmitter in analog AM mode, with full-scale sine-wave modulation. To avoid
undesirable output or possible antenna damage, it is highly recommended that
you perform these calibrations while operating the transmitter into a test load.