Adding noise and predistortions, and impairing the signal
R&S
®
SMM100A
282
User Manual 1179.1341.02 ─ 05
Remote command:
[:SOURce]:BB:IMPairment:BBMM<ch>:DELay
[:SOURce]:BB:IMPairment:IQOutput<ch>:DELay
[:SOURce]:BB:IMPairment:RF<ch>:DELay
Phase Offset
Adds an additional phase offset after the stream mapper.
You can shift the phase at the different stages in the signal generation flow, see:
●
"Baseband Offsets" >
●
"I/Q Stream Mapper" >
.
Remote command:
[:SOURce]:BB:IMPairment:BBMM<ch>:POFFset
[:SOURce]:BB:IMPairment:IQOutput<ch>:POFFset
[:SOURce]:BB:IMPairment:RF<ch>:POFFset
5.2.4
How to optimize the carrier leakage and sidebands suppression
Applying linear I/Q impairments helps to improve signal quality in the following cases:
●
To suppress a carrier leakage at the current RF frequency
●
To improve the attenuation of the unwanted sidebands
In the following examples, we assume that:
●
The R&S
SMM100A generates a baseband signal
●
A spectrum analyzer is connected to the R&S
SMM100A, the analyzed is config-
ured, and measures the required signal characteristics.
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".
Impairing the signal