I/Q Quadrature (Skew) Error - Agilent Technologies ESA-E Series User And Programming Manual

I/Q Quadrature (Skew) Error

Quadrature error is due to lack of a 90 degree phase shift between the I
and Q channels of a transmitter.
For non-scrambled or spread QPSK signals, the symptom of quadrature
error is indicated by parallelogram-shaped groupings of symbol decision
points in each quadrant.
Press
1. Use the I/Q polar constellation diagram first to identify this problem.
Figure 4-18 Polar Constellation Showing I/Q Quadrature Error
The shape of the parallelogram will shift 90° along the two axes and
NOTE
back again in random fashion. This is normal.
The analyzer arbitrarily assigns the demodulated symbols to the I and
Q channels for each new time record; the analyzer acts as an
asynchronous receiver. For this reason, it is not possible to determine
the correct carrier phase reference.
Chapter 4
Meas Control, Pause
Press
I/Q Measured Polar Constln
error is shown in Figure
with the symbol decision points at the rectangle corners. A
quadrature difference of 10° was used to obtain this result.
Although the display indicates a Wideband CDMA format, the signal
shown is a non-scrambled or spread QPSK signal.
Making Modulation Analysis Measurements
Interpreting Measurement Results
to view a single time record.
. A signal with an I/Q quadrature
4-18. A parallelogram shape is indicated
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