WLAN TX Measurements (Option K91) R&S FSL
1300.2519.12 2.140 E-11
IQ Impairments
IQ Offset
An IQ–Offset indicates a carrier offset with fixed amplitude. This results in a constant shift of the IQ
axes. The offset is normalized by the mean symbol power and displayed in dB.
Gain Imbalance
An ideal I/Q modulator amplifies the I and Q signal path by exactly the same degree. The imbalance
corresponds to the difference in amplification of the I and Q channel and therefore to the difference in
amplitude of the signal components. In the vector diagram, the length of the I vector changes relative to
the length of the Q vector.
The entry is displayed in dB and %, where 1 dB offset is roughly 12 % according to the following:
Imbalance [dB] = 20log
( | Gain
Q
| / | Gain
I
|)
Positive values mean that the Q vector is amplified more than the I vector by the corresponding
percentage:
Negative values mean that the I vector is amplified more than the Q vector by the corresponding
percentage:
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