Measurements
R&S
®
FSW
180User Manual 1173.9411.02 ─ 19
Fig. 5-28: Dynamic range for ACLR measurements on W-CDMA uplink signals as a function of the
mixer level
The level of the W-CDMA signal at the input mixer is shown on the horizontal axis, i.e.
the measured signal level minus the selected RF attenuation. The individual compo-
nents which contribute to the power in the adjacent channel and the resulting relative
level (total ACPR) in the adjacent channel are displayed on the vertical axis. The opti-
mum mixer level is -12 dBm. The relative adjacent channel power (ACPR) at an opti-
mum mixer level is -77 dBc. Since, at a given signal level, the mixer level is set in 1 dB
steps with the 1 dB RF attenuator, the optimum range spreads from -10 dBm to
-14 dBm.
To set the attenuation parameter manually, the following method is recommended:
► Set the RF attenuation so that the mixer level (= measured channel power – RF
attenuation) is between -10 dBm and -14 dBm.
This method is automated with the "Auto Level" function. Especially in remote control
mode, e.g. in production environments, it is best to correctly set the attenuation param-
eters prior to the measurement, as the time required for automatic setting can be
saved.
To measure the R&S FSW's intrinsic dynamic range for W-CDMA adjacent channel
power measurements, a filter which suppresses the adjacent channel power is
required at the output of the transmitter. A SAW filter with a bandwidth of 4 MHz, for
example, can be used.
Channel Power and Adjacent-Channel Power (ACLR) Measurement
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