The Spectrum Application
R&S
®
FPC
84
User Manual 1178.4130.02 ─ 07
It uses a resolution bandwidth of 1
MHz, a video bandwidth of 1
MHz and the peak
detector. After finishing the automatic measurement, the R&S
FPC sets the optimal
reference level.
Changing the span
Usually, the span that the R&S
FPC selects yields optimal results. But sometimes you
also need to see the spectrum outside the current span to detect other signal compo-
nents that you need to include in the measurement. Therefore, you can adjust the span
to up to ten times the channel bandwidth and hence still be able to see the spectrum
outside the measurement channel.
1. Press the "Span" key to open the span menu.
2. Select the "Manual Span" menu item.
The R&S
FPC opens an input field to define the span.
3. Enter the span you need.
Note:
The largest possible span for the channel power measurement is ten times
the channel bandwidth. At larger spans, the result of the channel power measure-
ment would be increasingly imprecise, because too few points of the trace would
be in the channel you are measuring.
14.2.7
Working with the Spectrogram Result Display
Access
(measurement menu): "Meas" > "Measurement Mode" > "Spectrogram"
Access
(measurement menu): "Meas" > "Measurement Mode" > "Spectrogram Play-
back"
Remote commands to control the spectrogram:
●
not supported
Available with the optional "Advanced Measurements" application.
The spectrogram result display shows the spectral density of a signal in the frequency
domain and over time simultaneously.
Like other result displays, the x-axis represents the
. The y-axis repre-
sents time. Time in the spectrogram runs chronologically from top to bottom. Therefore,
the top of the diagram is the present. A third dimension shows the amplitude for each
frequency by mapping different colors to every power level.
The color the R&S
FPC assigns to a power level that was measured depends on:
●
The color table you have selected.
●
The spectrogram reference level.
●
The spectrogram level range.
The spectrogram consists of horizontal lines, each one pixel high, that are called
frames. In the default state, a frame is added to the spectrogram after each
.
This means that the amount of data in a frame depends on the sweep time. Because
the spectrogram in the R&S
FPC runs from top to bottom, the outdated time line(s)
Measurements and Result Displays
