Chapter 2 WCDMA Call Mode
Testing User Equipment on WCDMA channels
WCDMA Options Version 6.20
51
Modulation Quality test
menu
This test menu provides you with all relevant parameters required to judge the
modulation quality, i.e. the modulation accuracy, of the UE. The Modulation
Quality results display shows the numeric results and the statistical evaluation
of the test.
To gain access to the Modulation Quality menu, select the [Mod. Quality] marker
tab.
How to read the modulation quality results display
The modulation quality parameters are displayed in a table showing the current,
minimum, average and maximum values of the measurements taken. The Count
field shows the number of iterative tests over which average values are calcu-
lated. To the right-hand side of the table a bar display allows for a quick and easy
identification of limit violation by providing violation indicators. For a detailed
description of the bar display refer to section “Display fields” on page 25.
EVM RMS
[%]
Shows the RMS value of the Error Vector Magnitude, i.e.
the RMS value of the error vector measured divided by
the RMS value of the reference signal, also expressed as
a percentage value. The EVM shows the deviation of the
measured signal vector from an ideal, calculated signal
vector, i.e. the error vector (magnitude and phase). As the
error vector value changes countinously and besides the
peak value a mean value is needed for facilitating the
assessment of modulation quality, the root mean squared
Error Vector Magnitude is determined as a measure of
modulation accuracy at the decision points. The RMS
value is an average of all the decision points (symbols)
across a whole measurement interval.
The EVM value shall not exceed 17.5% at an output
power of equal to or greater than –20 dBm and a power
step size of 1 dB under normal operating conditions.
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