Basic Measurement Examples
R&S
®
FSVA/FSV
123
Quick Start Guide 1321.3066.02 ─ 06
b) Switch the "Trg/Gate Polarity" softkey to "Neg."
The R&S
FSVA/FSV initiates triggering in response to the falling edge of
the burst. This shifts the burst to the left-hand half of the measurement dia-
gram. The power is measured in the deactivation phase. The start of the
burst is shifted to the center of the screen and the power during the deacti-
vation phase is measured.
Figure 7-12: Measurement of the signal-to-noise ratio of a GSM burst signal in
zero span.
7.4.3
Measuring FM-Modulated Signals
Since signal analyzers can display only the magnitude of the measurement signal
by using the envelope detector, the modulation of FM-modulated signals cannot
be measured directly as in the case of AM-modulated signals. The voltage at the
output of the envelope detector remains constant for FM-modulated signals as
long as the frequency deviation of the signal is located within the flat part of the
passband characteristic of the employed resolution filter. Amplitude variation
occurs only if the instantaneous frequency extends into a falling edge of the filter
curve. This behavior can be used to demodulate FM-modulated signals. The cen-
ter frequency of the analyzer is set in such a manner that the nominal frequency
of the measurement signal is located on a filter edge (below or above the center
Measurements in Zero Span
