Rohde & Schwarz R&S SMW200A - Applying Digital Predistortion; Frequency Response Correction

Simulating Fading, Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMW200A
447User Manual 1175.6632.02 ─ 30
To optimize sideband suppression
For a given baseband signal, perform the following iterative steps:
1. In the block diagram, select "I/Q Mod > I/Q Digital Impairments".
2. Set the values of the parameters "Gain Imbalance" and "Quadrature Offset" to
adjust the relative amplitude and phase relationship of the baseband signal.
3. Select "State > On".
4. On a connected signal analyzer, monitor the power spectrum.
5. Vary the values of the parameters "Gain Imbalance" and "Quadrature Offset" until
the maximal sideband suppression is achieved.
To optimize the carrier leakage suppression
For a given baseband signal, perform the following iterative steps:
1. In the block diagram, select "I/Q Mod > I/Q Digital Impairments".
2. Set the parameters "I Offset" and/or "Q Offset".
3. Select "State > On".
4. On a connected signal analyzer, monitor the power spectrum.
5. Vary the "I/Q Offset" until the maximal carrier leakage suppression is achieved.
Adjusting the I and Q offsets is one of the possible ways to control carrier leakage.
See Chapter 5.14.3, "How to Improve Signal Characteristics by Shifting the Base-
band Signal", on page 413 for other related settings.
6.5 Frequency Response Correction
Frequency response correction is a method, used to compensate the frequency
response influence of the test setup, for example of the cables, power combiners,
switches or mixers. In the R&S SMW, you can load user-defined scattering parameters
(S-parameters) files and frequency response files and pre-process the infernally gener-
ated baseband signal with them.
See user manual R&S SMW-K544 User-Defined Frequency Response Correction.
6.6 Applying Digital Predistortion
Digital predistortion (DPD) is one of the methods, used to improve the efficiency of RF
power amplifiers. In the R&S SMW, the generated digital signal can be deliberately
AM/AM and AM/PM predistorted.
See user manual R&S SMW-K540, R&S SMW-K541 Envelope Tracking and AM/AM,
AM/PM Predistortion.
Applying Digital Predistortion