Signal Generator Settings
R&S
®
SGT100A
194
User Manual 1176.8674.02 ─ 07
2
= Resulting AM/AM predistortion function, calculated as AM/AM(x) = abs[P
DPD
(x)]
3
= Ideal AM/PM function (constant phase at 0 degrees)
4
= Resulting AM/PM predistortion function, calculated as AM/PM(x) = tan
-1
{Im[P
DPD
(x)]/
Re[P
DPD
(x)]}
With the provided settings, you can define a polynomial function with up to 10
th
order to describe the predistortion function.
The graphical display updates on-the-fly and visualize of the resulting AM/AM and
AM/PM functions.
5. Select "Polynomial Order = 4" (n = 4).
6. Set the polynomial coefficients a
0
to b
4
.
7. Select "Apply".
The instrument loads the configured values, calculates the correction values, and
displays the predistortion functions.
Figure 7-24: Predistortion Settings > Polynomial: Understanding the displayed information
1a
= Normalized value of the current RF RMS power level
2a
= Normalized value of the current PEP of the generated RF signal
1b, 2b
= Correction values
white dashed line
= Ideal zero function; no correction is necessary
AM/AM yellow curve = AM/AM correction values, calculated as
Δ
AM/AM(x) = AM/AM(x) - x
AM/PM yellow curve = AM/PM correction values, calculated as
Δ
AM/PM(x) = AM/PM(x)
3a, 3b
= X-axis scale, calculated form the
4
= Negative correction coefficients
5
= Values greater than the
are ignored
8. To store the defined predistortion function:
a) Select "Save/Recall Polynomial"
b) Navigate throughout the file system and enter a "File Name", e.g.
MyPolyno-
mial_4thOrder
Applying Digital Predistortion
