Rohde & Schwarz FSQ series, Quick Start Manual

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R&S FSQ Basic Measurement Examples
Measuring Harmonics of Sinusoidal Signals
5.10 Quick Start Guide 1313.9652.62 - 02
5.2.2 Reducing Noise
The R&S FSQ offers three means of effectively differentiating the harmonics of a signal from
the noise:
• Reducing the video bandwidth
• Averaging the trace
• Reducing the resolution bandwidth
Reducing the video bandwidth and averaging the traces cause the noise from the R&S FSQ
or the DUT to be reduced, depending on which component is larger. Both averaging methods
reduce the measurement uncertainty particularly in the case of small signal-to-noise ratios,
because the measurement signal is also separated from the noise.
1. Reducing the noise by reducing the video bandwidth.
➢
Press the BW key.
➢
Press the VIDEO BW MANUAL softkey.
➢
Using the rotary knob (turning it counterclockwise), reduce the video bandwidth to 10
kHz (for example), or enter
10 kHz .
This clearly smooths the noise, and the sweep time will increase to 25 ms. In other
words, the measurement will clearly take more time. The video bandwidth that is shown
in the display is marked with an asterisk (*VBW) to indicate that it is no longer coupled
to the resolution bandwidth (see
Fig. 5-3 ).
Fig. 5-3 Suppression of noise during harmonics measurement by reducing video
bandwidth