Emerson R&S SGT100A User Manual page 152

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R&S SGT100A
6.3.2.2 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 6-7: 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. The imbalance occurs 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.
Figure 6-8: Negative gain imbalance (left) and positive (right) gain imbalance in the I/Q constellation
6.3.2.3 Quadrature offset
Changes the phase angle between the I and Q vectors from the ideal 90 degrees,
while the amplitudes are maintained. A positive quadrature offset results in a phase
User Manual 1176.8674.02 ─ 12
diagram
Signal generator settings
I/Q modulation and impairment settings
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