Applying I/Q vector modulation
R&S
®
SMM100A
293
User Manual 1179.1341.02 ─ 05
5. Vary the value of the parameter "Baseband Gain" until the maximal suppression of
the intermodulation products is achieved.
To optimize the characteristics of signals with high adjacent channel power ratio
(ACPR)
For a given baseband signal (e.g. a 3GPP signal) and RF frequency, perform the fol-
lowing iterative steps:
1. In the block diagram, select "I/Q Mod > I/Q Settings > I/Q Modulator > On".
The I/Q modulator is enabled. Modulated is the internal baseband signal.
2. Select "Baseband Gain = 6 dB".
3. On a connected signal analyzer, monitor the signal characteristics.
4. Vary the value of the parameter "Baseband Gain" until the maximal signal-to-noise
ratio (SNR) is achieved.
To trigger the internal correction routine of the I/Q modulator
System error correction of the I/Q modulator permits precise and repeatable measure-
ments.
If a temperature fluctuation of several degrees occurs, trigger the correction routine
using the following:
1. Select "I/Q Mod > I/Q Modulator > Adjust I/Q Modulator Current Frequency"
2. Or select [Setup] > "System > Internal Adjustments > Adjust I/Q Modulator Current
Frequency".
See also
Chapter 16.3.3.2, "How to use the internal adjustments"
To generate a wideband modulation signal
1. In the block diagram, select "I/Q Mod > I/Q Settings > I/Q Modulator > On".
The I/Q modulator is enabled. Modulated is the internal baseband signal.
2. Select "I/Q Wideband > On".
The R&S
SMM100A shifts the switching frequencies of the lowpass filters in the
output section and generates signal with higher I/Q modulation bandwidth.
The harmonic suppression, however, degrades.
Optimizing I/Q modulation performance