Datasheet

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APPLICATION NOTEInterference Hunting
CASE STUDY: WIMAX NETWORK INTERFERENCE
In this example of interstitial channel interference, two WiMAX
operators were running into problems trying to the get the
maximum performance out of their spectrum by utilizing
channels on the edge of the assigned spectrum. The nearly
inevitable result was that the two WiMAX base stations were
interlacing with each other, reducing performance (even
though the systems were still functional) particularly for victim
receivers on the edge of the system coverage area. After failed
attempts to identify the problem using traditional swept tune
spectrum analyzers, the operators turned to a Tektronix RTSA.
As shown in Figure 11 below, the spectrogram clearly showed
the interlacing occurring across the base stations, allowing the
operators to take the proper corrective actions.
CASE STUDY: TRUNK LMR INTERFERENCE
A trunked land mobile radio (LMR) system is a complex type of
computer-controlled two-way radio system that allows sharing
of relatively few radio frequency channels among a large group
of users. This technology is widely used by government entities
to provide two-way communication for fire departments, police
and other municipal services.
In this case, a LMR system in a metropolitan area was
generating spurious broad-banded noise when certain
conditions were met. The interference problem was
particularly difficult to identify because the victim receiver
frequency was > 3 MHz from the assigned frequency of the
transmitter source.
The “DXPOgram” measurement in display in SignalVu-PC was
key to finding the problem because it allowed the operator to
record the spectrum over time with a narrow RBW filter. Record
and playback functionality was used to capture the problem
over the time so the operator could perform a visual correlation
of the impact of the problem on the victim receiver.
FIGURE 11. The spectrogram on the right clearly shows the interlacing occurring
across WiMAX base stations. This is a very good example of how a spectrogram
can monitor spectrum over time. The basic spectrum display does not show
much information about the problem, while the TDMA nature of the WIMAX
signals is clearly observed in the spectrogram.
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FIGURE 12. A spectrogram with record and playback was used to identify a
spurious broad-banded noise source in a trunked LMR system.