Chapter 3 WCDMA Non-Call Mode
RF Analyzer for modulation quality
92 WCDMA Options Version 6.20
Rho — Displays the waveform quality factor, a measure of modulation accuracy.
A value of 1 indicates perfect waveform quality.
According to WCDMA specifications the minimum Rho value should be 0.994.
I/Q Offset [dB] — Shows the I/Q origin offset. The value displayed here is the
determined ratio between the I/Q offset vector and the average signal vector
corrected by offset and is expressed in dB.
The I/Q offset value shall not exceed –25 dB.
I/Q Imbalance [dB] — Shows the I/Q imbalance value, which is a factor for
assessing the accuracy of the I/Q modulator's modulating signal amplitude
balance. It is the ratio of the power in the desired sideband carrier produced and
the undesired sideband carrier produced due to an amplitude difference between
the input signals to the I/Q modulator, expressed in dB.
The I/Q imbalance value shall not exceed –15 dB.
The limit values for all modulation quality assessment factors are set in the
Measurement Limits Parameter menu. For details on setting or modifying
systems parameters please refer to section “Measurement Limits” on page 71.
The softkey functions are explained in section “Softkeys of the RF Analyzer” on
page 102.
Constellation Display The Constellation Display screen provides a graphical analysis of the modulation
quality measurement’s result. It allows technicians to pinpoint faults of the
terminal for a more detailed failure analysis.
In order to access the constellation display push the [Const. Display] marker tab
from the Modulation Quality menu.
The parameters used for measuring and displaying the modulation quality factors
on this screen are identical to the parameters used on the Modulation Quality
screen. For a parameter description refer to “RF Analyzer parameter fields” on
page 103.
On the right-hand side of the constellation display there are several display fields
showing the channel power value in dBm as well as the measurement results for
the following modulation quality factors: EVM RMS as a percentage, magnitude
error RMS, as a percentage, phase error RMS in degrees, Rho, I/Q offset in dB and
I/Q imbalance in dB. For details on the meaning of these factors and their asso-
ciated valid limits see “Reading the results” on page 91.
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