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Chapter 5 149
CDMA Measurements - Screens and Control Fields
CDMA Measurements
IQ Constellation Diagram, IS-2000 only
If you have the IS-2000 option installed, you will be able to select the
I/Q PLOT screen from the set of available measurements.
Figure 5-16 IQ Constellation Diagram
The I/Q Constellation Diagram screen graphically shows I/Q decision
points. This is a useful troubleshooting tool when investigating Rho
problems
Visual presentation helps identify IQ errors. Figure 5-16 shows no
errors. However, the 4 point groupings could be skewed away from
perfect square or offset indicating a phase error. This will result in
interference from I to Q and from Q to I. Phase errors can result from
crosstalk between I and Q in the base station baseband processing
section, misaligned LOs or intermodulation between Walsh codes.
PN Offset Search
There are two ways to provide your Base Station’s PN Offset value to
the Test Set:
• Enter the value directly. See “PN Offset” on page 165
• Have the Test Set determine the value from the received signals. See
“PN Incrment” on page 165