Emerson R&S SGT100A User Manual page 166

®
R&S SGT100A
Figure 6-11: Simplified test setup for power amplifier envelope tracking tests
The R&S SGT in this setup is configured to generate both, an RF signal with complex
modulation scheme and an envelope signal, that follows the envelope variation of this
RF signal. A suitable test signal is, for example, an EUTRA/LTE DL signal.
The R&S SGT generates the envelope signal directly from the baseband signal. The
envelope signal is a voltage signal, with voltage level V
the RF signal (
function, the envelope signal linear dependent follows the variation of the RF signal's
envelope.
The envelope signal is output at the I out and I Bar out rear panel connectors. This
envelope signal is then further fed to an external DC modulator.
The PA receives the RF input signal and the dynamically adapted supply voltage v
Ideally, the PA gain stays constant.
Suitable ARB signal to observe the effect of the envelope tracking settings
To simplify the explanation in the following sections, we use a simple ramp function as
an ARB waveform modulated on the RF carrier.
6.5.2.1 Envelope voltage adaptation modes
In the R&S SGT, you define the voltage of the generated envelope signal using one of
the following modes:
●
Auto Power/Normilized Envelope Voltage Adaptation:
In this mode, you define the desired input characteristics of the power amplifier.
Based on these values and depending on the crest factor of the generated signal,
the R&S SGT calculates:
–
–
The auto voltage adaptation mode is a suitable choice, if you have knowledge on
the power amplifier components and characteristics. Common PA characteristics
User Manual 1176.8674.02 ─ 12
√ [I(t)
2 +Q(t) 2 ]) of the corresponding path. If you do not apply a shaping
The voltage on the I out/I Bar out connectors
The RMS level of the RF signal
Signal generator settings
Generation of envelope tracking signals
proportional to the power of
out
(V Min/Max) and a bias (Bias),
out
.
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