Quadrature Offset - R&S SGT100A User Manual

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R&S SGT100A
Figure 7-5: 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, which 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.
Figure 7-6: Negative gain imbalance (left) and positive (right) gain imbalance in the I/Q constellation
7.3.2.3

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
angle greater than 90 degrees. The effect of a positive quadrature offset in the I/Q con-
stellation diagram is shown below.
User Manual 1176.8674.02 ─ 07
diagram
Signal Generator Settings
I/Q Modulation and Impairment Settings
134