R&S 1129.7246.03, Operating Manual

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Operating Manual 1302.6163.12 - 03 4.77
R&S ESU Instrument Functions
IF Spectrum Analysis Mode
4.6 IF Spectrum Analysis Mode
In IF spectrum analysis, the spectrum of the RF input signal is displayed in the vicin-
ity of the receiver frequency. The center frequency of the displayed spectrum is
always the current receive frequency.
The IF analysis provides a fast overview of the assignment of the spectrum adjacent
to the measuring channel proper, or, with a large IF bandwidth, the spectral distribu-
tion of a modulated signal in the channel. Interference of the received useful signal
can also be detected quickly, whether it is CW interference appearing as unmodu-
lated carrier or pulse-like interference which is represented in the form of narrow
horizontal lines on the screen.
The IF spectrum analysis is a very comfortable means for exact frequency tuning of
the receiver and for identification of signals and of their bandwidth. The accuracy of
the frequency axis corresponds to the reference used (internal or external). The fre-
quency display range (span) can be selected between 1 kHz and 10 MHz in steps of
1, 2 and 5. With the bandwidths 10 Hz to 100 kHz in steps of 1, 3, 10 the frequency
resolution can be matched to the span.
In contrast to normal spectrum analyzer operation, the measured values are deter-
mined using FFT from samples recorded from the A/D-converter. Thus the receiver
stays tuned to the center frequency. It may continue to measure with the selected
measurement time and display the signal level with the bar graph. For example, the
quasipeak level measured with one second measurement time may be displayed in
the upper half of the display while in the lower half the spectrum may be refreshed
every few milliseconds.