Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMBV100B
269User Manual 1178.4460.02 ─ 03
4.2 Impairing the Signal
In the R&S SMBV100B, analog and digital linear impairments such as I/Q imbalance
and quadrature error can be added to the generated signal.
The instrument can also simulate the effect of non-linear memoryless effects like
AM/AM and AM/PM conversion.
See user manual R&S SMBVB-K540, R&S SMBVB-K541 Envelope Tracking and
AM/AM, AM/PM Predistortion.
4.2.1 Required Options
The base unit is sufficient. Additional options are not required.
4.2.2 About the Linear I/Q Impairments
Signal impairments (I/Q Impairments) are well-defined arithmetic modifications of the
data. Every data sample is modified in the same way.
Adding linear impairments to the data stream is provided for the following purpose:
●
To simulate frequent sources of distortions in a real signal-processing chain as, it is
required for tests with dirty transmitter conditions (receiver tests)
●
To compensate the faults of the I/Q demodulator in the receiver
See Chapter 4.2.4, "How to Optimize the Carrier Leakage and Sidebands Suppres-
sion", on page 275.
The R&S SMBV100B offers functions to impair the internally generated signal or the
externally fed analog I/Q signal linearly:
●
Each generated I/Q stream can be impaired digitally
●
Analog impairments can be added to the externally applied analog I/Q signal,
before it is passed to in the I/Q modulator (see "Defining the input signal of the I/Q
modulator" on page 277)
●
The internal signal can be impaired twice, analog and digital. If both types of
impairments are enabled, they superimpose each other in the signal.
Impairments caused by the I/Q modulator are automatically corrected by the Adjust I/Q
Modulator Current Frequency function.
See also "Internal Adjustments" on page 928.
4.2.2.1 Gain and Gain Imbalance
An I/Q gain is a multiplication of all I/Q amplitudes by a common factor. The effect is
equivalent to two identical I and Q gain factors. The effect of an increased gain factor
in the I/Q constellation diagram is shown on Figure 4-4.
Impairing the Signal
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