Spectrum Analyzer Mode
R&S
®
Cable Rider ZPH
175
User Manual 1321.0950.02 ─ 07
2. Select the "% Power BW" softkey.
The R&S Cable Rider ZPH opens an input field to define the power percentage.
3. Enter the power percentage you need.
The value you enter here is the power percentage that has to be inside the channel
bandwidth relative to the power over the total span (the percentage of the total
power).
The R&S Cable Rider ZPH now displays the occupied bandwidth graphically in the
trace window and numerically above the trace window.
8.1.3.5
Changing the Span
The span that the R&S Cable Rider ZPH usually sets yields optimal results. But some-
times you also need to see the spectrum outside the current span to detect other signal
components that you need to include in the measurement. Therefore, you can adjust
the span to up to ten times the channel bandwidth and still be able to see the spectrum
outside the measurement channel.
1. Press the [CAL/SPAN] key.
In the default configuration, "Auto Span" is active. The R&S Cable Rider ZPH auto-
matically sets the optimal span for the channel power measurement.
2. Select the "Manual Span" softkey.
The R&S Cable Rider ZPH opens an input field to define the span manually.
3. Enter the span you need.
The largest possible span for the channel power measurement is ten times the
channel bandwidth. At larger spans, the result of the channel power measurement
would be increasingly imprecise, because too few points of the trace occur in the
channel to be measured.
4. Select the "Auto Span" softkey.
The R&S Cable Rider ZPH again calculates the span automatically.
8.1.4
Power Measurements on TDMA Signals
When TDMA (time division multiple access) methods are used, e.g. for GSM, several
users share a channel. Each user is assigned a period of time or timeslot. With the
TDMA power measurement, you can determine the power over one of the timeslots
allocated to the user.
The TDMA power measurement is a measurement in the time domain (span = 0 Hz).
You can start it on an external or video trigger and specify the power measurement
time.
To prevent incorrect power measurements in the time domain, make sure that the
whole signal is within the selected resolution bandwidth. If the resolution bandwidth is
too small, the displayed power will be lower than the actual power.
1. Press the [MEAS] key.
Performing Spectrum Measurements
