Measurement Basics
R&S
®
FSW-K40
23
User Manual 1173.9286.02 ─ 15
Spur threshold
During the second stage, the application uses statistical methods to remove a spur. A
spur is detected, if the level of the signal is above a certain threshold. The spur thresh-
old is relative to an imaginary median trace that the application calculates.
If parts of the signal are identfied as spurs, the application removes all signal parts
above that level and substitutes them with the median trace.
Figure 4-1: Spur detection and removal principle
4.2 Residual Effects
Residual noise effects are modulation products that originate directly from the phase
noise. It is possible deduct them mathematically from the phase noise of a DUT.
The application calculates three residual noise effects. All calculations are based on an
integration of the phase noise over a particular offset frequency range.
Residual PM
The residual phase modulation is the contribution of the phase noise to the output of a
PM demodulator. It is evaluated over the frequency range you have defined.
[dBc/Hz]
noise
phase
sideband
single
with
PM
Residual
)
(
)
(
2
f
L
rad
df
f
L
stop
start
f
f
m
m
Residual Effects
