Rohde & Schwarz R&S SMW200A - About the Linear I;Q Impairments; Required Options

Simulating Fading, Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMW200A
440User Manual 1175.6632.02 ─ 30
The instrument can also simulate the effect of non-linear memoryless effects like
AM/AM and AM/PM conversion.
See user manual R&S SMW-K540, R&S SMW-K541 Envelope Tracking and AM/AM,
AM/PM Predistortion.
6.4.1 Required Options
The equipment layout for signal impairments includes:
●
Option Standard or Wideband Baseband Generator (R&S SMW-B10/-B9) per sig-
nal path
●
Option Baseband main module, one/two I/Q paths to RF (R&S SMW-B13/-B13T) or
option Wideband baseband main module two I/Q paths to RF (R&S SMW-B13XT)
Sufficient for impairment of the analog and the digital I/Q signal output at the DIG
I/Q interfaces
6.4.2 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 6.4.4, "How to Optimize the Carrier Leakage and Sidebands Suppres-
sion", on page 446.
The R&S SMW offers functions to impair the internally generated signal or the exter-
nally 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 448)
●
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 Chapter 17.3.3.2, "How to Use the Internal Adjustments", on page 1282.
6.4.2.1 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 6-6.
Impairing the Signal