Defining The Power Level Of The Generated Signal; Defining The Correction Values; Polynomial Function - R&S SGT100A User Manual

®
R&S SGT100A
An AM/AM representation is a standard method that shows the signal power level at
the input of the DUT against the power level at the output of the DUT. The default unit
for both axes is dBm but the AM/AM representation can also be normalized.
An AM/PM curve shows the phase difference in degrees (y-axis) for every input power
level (x-axis).
If your R&S SGT is equipped with the required option R&S SGT-K541, you can define
both, an AM/AM and an AM/PM predistortion and apply them separately or superim-
posed on each other on the generated digital baseband signal.
If your instrument is equipped with the option R&S SGT-K540, you can also apply pre-
distortions on the generated envelope signal.
Refer to
more information.
7.6.2.1

Defining the Power Level of the Generated Signal

You can define the level of the generated signal in one of the following ways:
●
Level Reference > Before DPD
In this mode, the "Level" parameter in the status bar of the instrument defines the
signal level before the DPD is applied.
Signal with selected level is pre-distorted and depending on the selected AM/AM
and AM/PM functions, attenuated or boosted.
●
Level Reference > After DPD
In this mode, you define the resulting signal level. Based on this value and depend-
ing on current predistortion function, the R&S SGT calculates the level of the signal
to be pre-distorted.
The level calculation requires several interaction cycles; the number of iterations is
a trade-off between level accuracy and speed.
7.6.2.2

Defining the Correction Values

In the R&S SGT, you can select the way you define the predistortion function and
choose between:
●
A polynomial function with up to 10 polynomial coefficients
(see
●
A predistortion function defined as a look-up table
(see
●
A normalized data
(see
●
To set the correction values in raw format with a single remote control command
(see

Polynomial Function

The polynomial function is an analytical method to describe a predistortion function.
When using the polynomial function, you do not define the correction values (ΔPower
User Manual 1176.8674.02 ─ 07
Chapter 7.5, "Generation of Envelope Tracking
"Polynomial Function"
"Shaping Table" on page 182)
"Normalized Data" on page 182)
"Predistortion Function in Raw Data Format"
on page 180)
Signal Generator Settings
Applying Digital Predistortion
Signals", on page 146 for
on page 183).
180