Rohde & Schwarz SMW200A - How to Optimize the Carrier Leakage and Sidebands Suppression

Simulating Fading, Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMW200A
413User Manual 1175.6632.02 ─ 16
Remote command:
[:SOURce]:BB:IMPairment:BBMM<ch>:DELay on page 1012
[:SOURce]:BB:IMPairment:FADer<ch>:DELay on page 1012
[:SOURce]:BB:IMPairment:IQOutput<ch>:DELay on page 1012
[:SOURce]:BB:IMPairment:RF<ch>:DELay on page 1012
5.3.4 How to Optimize the Carrier Leakage and Sidebands Suppression
Applying linear I/Q impairments helps to improve signal quality in the following cases:
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To suppress a carrier leakage at the current RF frequency
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To improve the attenuation of the unwanted sidebands
In the following examples, we assume that:
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The R&S SMW generates a baseband signal
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A spectrum analyzer is connected to the R&S SMW, the analyzed is configured,
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".
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 4.12.3, "How to Improve Signal Characteristics by Shifting the Wan-
ted Baseband Signal", on page 387 for other related settings.
Impairing the Signal