Atec Rohde-Schwarz-EB500 - Manual (Page 18)

Signal processing in panorama scan mode
max. 20 MHz
FFT window 1 FFT window 2
n=1 n = X
f
start
Frequency in MHz
a in dBµV
f
stop
FFT window n
Resolution in panorama scan mode
a in dBµV
max. 20 MHz
Bin width: min. 100 Hz
max. 2 MHz
n = 1 n = X
Frequency in MHz
Bin width and channel spacing
f1 Frequency in MHz
a in dBµV
f2
Signal frequencies
Bin
width
Points for FFT calculation
Channel
spacing
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the R&S®EB500 automatically determines the required FFT
length and the width of the frequency window for each
scan step. The receiver selects these internal parameters
so that the optimum scan speed is achieved for each reso­
lution bandwidth (see figure “Resolution in panorama scan
mode”).
In the panorama scan mode, the resolution bandwidth of
2 MHz yields the maximum scan speed, while the resolu­
tion bandwidth of 100 Hz yields maximum sensitivity.
The resolution bandwidth (bin width) for the panorama
scan (selectable between 100 Hz and 2 MHz) therefore
corresponds to the resolution bandwidth (BW
bin
) used in
the DNL calculation for the IF spectrum (see DNL formula
under “IF spectrum”), and can be used for calculating the
DNL for the panorama scan. Moreover, the user selects
the resolution bandwidth to obtain the desired frequency
resolution (see figure “Bin width and channel spacing”).
The above explanations show that the use of digital signal
processing in a radiomonitoring receiver offers decisive
advantages. Extremely high sensitivity (due to very fine
resolution) combined with a broad spectral overview and
maximum scan speed significantly increases the probabil­
ity of intercept in comparison with an analog receiver.
Basic sequence of steps in fast panorama scan mode.
Selecting the panorama scan resolution by varying the bin width. Selecting a 12.5 kHz bin width to capture a radio service using 12.5 kHz
channel spacing.
The realtime signal processing at the IF level also includes
other high­performance capabilities, such as overlapping
FFT for the optimum capture of pulsed signals and a con­
figurable bin width for adjusting to the channel spacing
of known radio services. These functions are described in
detail in the user manual.
Panorama scan
The receiver’s maximum FFT bandwidth of 20 MHz makes
it possible to perform extremely fast scans across a wide
frequency range (panorama scan). For this purpose, fre­
quency windows of max. 20 MHz width are linked in suc­
cession, so that the complete, predefined scan range is
traversed (see figure “Signal processing in panorama scan
mode”). As is done for the IF spectrum, an FFT is used to
process the broad window with a finer resolution.
The width of the frequency window and the FFT length
(number of FFT points) are variable and are selected by the
receiver.
In the panorama scan mode, the user can select among 24
resolution bandwidths from 100 Hz to 2 MHz. The resolu­
tion bandwidth corresponds to the width of the frequency
slices (bin width) mentioned under “IF spectrum”. Based
on the selected bin width and start and stop frequency,