Bird Technologies VPM3 User Manual
Page 48
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Poor amplifier linearity caused by amplifier compression. This results in
signal distortion and poor fidelity of transmitted waveforms.
Antenna damage or degradation resulting in high transmission system
reflections.
Issues with transmitter modulator performance resulting in high error
vector magnitude (EVM).
Many of the above transmission system issues may be identified through the
use of the statistical techniques mentioned above. For example, if a particular
LTE radio system was known to be dropping calls at a higher rate than expected,
a service technician will need to know whether the problem is with the radio
itself, or with some element of the transmission system, or with the air inter-
face. Measuring the CCDF statistics of the base station radio, while terminated
with a high quality 50 ohm termination, and then again with the radio con-
nected to the transmission and antenna system will provide clues as to where
the issues may be.
Another useful technique is to compare live data from the system with a known
“reference” transmission, as is demonstrated above using Gaussian waveforms.