Upconverter Settings
R&S
®
SGU100A
80
User Manual 1176.7726.02 ─ 09
7.3.1
I/Q Impairments
Signal impairments are well-defined arithmetic modifications of the data. Every data
sample is modified in the same way. The purpose of adding impairments to the data
stream is to simulate frequent sources of distortions in a real signal-processing chain to
generate a test signal with dirty transmitter conditions.
7.3.1.1
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 below.
Figure 7-1: Effect of an increased amplitude in the I/Q constellation diagram
An I gain multiplies the I amplitudes by a factor, leaving the Q amplitudes unchanged.
A Q gain has the opposite effect. Different I and Q gain factors result in an I/Q imbal-
ance. This is usually due to different gains of the amplifiers in the I and Q channels of
the I/Q modulator. The effect of a positive and negative gain imbalance is shown
below.
I/Q Modulation and Signal Impairment