Rohde & Schwarz FSW-K40, Руководство пользователя

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Measurement Basics
R&S
®
FSW-K40
22 User Manual 1173.9286.02 ─ 15
4 Measurement Basics
The measurement basics contain background information on the terminology and prin-
ciples of phase noise measurements.
Phase noise measurements in general determine the single sideband phase noise
characteristics of a device under test (DUT).
● Spurs and Spur Removal ........................................................................................22
● Residual Effects ...................................................................................................... 23
● Measurement Range ...............................................................................................24
● Sweep Modes ......................................................................................................... 25
● Trace Averaging ......................................................................................................25
● Frequency Determination ........................................................................................27
● Level Determination ................................................................................................ 30
● Signal Attenuation ...................................................................................................30
● Using Limit Lines .....................................................................................................31
● Analyzing Several Traces - Trace Mode .................................................................33
● Using Markers .........................................................................................................35
4.1 Spurs and Spur Removal
Most phase noise results contain unwanted spurs. Spurs are peak levels at one or
more offset frequencies and are caused mostly by interfering signals. For some appli-
cations you may want to specifically indentify the location of spurs. However, for some
applications, spurs do not matter in evaluating the results and you may want to remove
them from the trace in order to get a "smooth" phase noise trace.
Spur display
Usually, spurs are visible on the trace as a peak. In addition, the R&S FSW draws a
straight, vertical line to visually represent the position of a spur. The length of these
lines indicate the level of the spur in dBc and refers to the scale on the right side of the
phase noise diagram.
The lines indicating a spur are not part of the trace data. When you export the trace, for
example, the spur data is not exported.
Spur suppression
The application allows you to (visually) remove spurs from the trace. Spur removal is
based on an algorithm that detects and completely removes the spurs from the trace
and fills the gaps with data that has been determined mathematically.
The spur removal functionality separates the actual spur power from the underlying
phase noise and displays the latter in a two-stage process. The first stage of spur
detection is based on an eigenvalue decomposition during the signal processing.
Spurs and Spur Removal