Analog Demodulation Option R&S
FSV–K7
R&S
®
FSV-K7/K7S
20
Operating Manual 1176.7561.02 ─ 06
Number of measured values
During a frequency sweep, the R&S
FSVA/FSV increments the first local oscillator in
steps that are smaller than approximately 1/10 of the bandwidth. This ensures that the
oscillator step speed is conform to the hardware settling times and does not affect the
precision of the measured power.
The number of measured values taken during a sweep is independent of the number of
oscillator steps. It is always selected as a multiple or a fraction of 691 (= default num-
ber of trace points displayed on the screen). Choosing less then 691 measured values
(e.g. 125 or 251) will lead to an interpolated measurement curve, choosing more than
691 points (e.g. 1001, 2001 …) will result in several measured values being overlaid at
the same frequency position.
RMS detector and VBW
If the RMS detector is selected, the video bandwidth in the hardware is bypassed.
Thus, duplicate trace averaging with small VBWs and RMS detector no longer occurs.
However, the VBW is still considered when calculating the sweep time. This leads to a
longer sweep time for small VBW values. Thus, you can reduce the VBW value to ach-
ieve more stable trace curves even when using an RMS detector. Normally, if the RMS
detector is used the sweep time should be increased to get more stable trace curves.
2.1.9
Stability of Measurement Results
Despite amplitude and frequency modulation, the display of carrier power and carrier
frequency offset is stable.
This is achieved by a digital filter which sufficiently suppresses the modulation, provi-
ded, however, that the measurement time is ≥ 3 x 1 / modulation frequency, i.e. that at
least three periods of the AF signal are recorded.
The mean carrier power for calculating the AM is also calculated with a digital filter that
returns stable results after a measurement time of ≥ 3 x 1 / modulation frequency, i.e.
at least three cycles of the AF signal must be recorded before a stable AM can be
shown.
2.1.10
Measurement Result Display
In Analog Demodulation mode, the measurement results can be displayed in up to 4
different screens (windows), plus an additional marker table, if applicable. Each screen
shows either the measurement results as a diagram or the results of evaluation func-
tions in a table ("Result Summary").
All displays are determined by the I/Q data set recorded for the measurement.
You can define the display configuration for up to 4 different screens at once using the
Instrument Functions Analog Demodulation
