Tektronix NetTek YBT250, User Manual

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Taking Measurements
3- 100
YBT250 Field Transmitter & Interference Tester User Manual
The EVM measurement is an average of the last ten data points.
When you change a setting, the queue of the last ten data points is
flushed. While the queue is filling, the help link text includes “**”
and the message “**EVM result being averaged - please wait” is
shown. This message goes away after ten data points are available to
average (this might require several seconds). Until this averaging is
completed, the EVM result will exhibit more variation.
Transmit Diversity
Some W-CDMA systems use Transmit Diversity to increase signal
robustness between the Node B and mobile. When enabled in the
downlink signal, Transmit Diversity uses two antennas, referred to as
Antenna 1 and Antenna 2, to transmit two differently-encoded
versions of the same data.
The YBT250 lets you select which antenna signal to measure for
W-CDMA Carrier Frequency, Signal Quality, Code Power,
Codogram, and Pilot Power measurements. To select the transmit
diversity antenna, open the
Edit > Meter tab.
The YBT250 displays an antenna button above the measurement
display to indicate which antenna signal is the source for measure-
ments. (see Figure 3--48.) Tap the button to open the
Edit >
Meter tab.
Measuring 1xEV-DO Signal Quality
Requires Option CDE
Option CDE provides the following 1xEV-DO signal quality
measurements:
H
Waveform Quality (Rho)
H
Error Vector Magnitude (EVM)
H
Data Constellation Type
H
PN Offset (PNOS)
H
Pilot Time Alignment Error (Tau)