Rohde & Schwarz R&S FSL3 - Page 57

Measurements on Modulated Signals R&S FSL
1300.2519.12 2.32 E-11
Fig. 2-25 Measuring the adjacent channel power of a W–CDMA signal with the fast ACP
mode
Note: With W–CDMA, the R&S FSL's dynamic range for adjacent channel measurements is limited by
the 12–bit A/D converter. The greatest dynamic range is, therefore, obtained with the IBW
method.
Optimum Level Setting for ACP Measurements on W–CDMA Signals
The dynamic range for ACPR measurements is limited by the thermal noise floor, the phase noise and
the intermodulation (spectral regrowth) of the spectrum analyzer. The power values produced by the
R&S FSL due to these factors accumulate linearly. They depend on the applied level at the input mixer.
The three factors are shown in the figure below for the adjacent channel (5 MHz carrier offset).
-80
-75
-70
-65
-60
-55
-50
-45
-40
-35
-30
-40 -35 -30 -25 -20 -15 -10
Mixer Level / dBm
ACLR / dBc
S.R.I.
Optimum Range
Phase
Noise
Total
ACLR
Thermal Noise
Fig. 2-26 The R&S FSL's dynamic range for adjacent channel power measurements on W–CDMA
uplink signals is a function of the mixer level.