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The Spectrum Application (RF Measurements)
R&S
®
FPL1000
256
User Manual 1178.3370.02 ─ 03
A signal analyzer cannot be classified as a true power meter, because it displays the IF
envelope voltage. However, it is calibrated such as to display the power of a pure sine
wave signal correctly, irrespective of the selected detector. This calibration cannot be
applied for non-sinusoidal signals. Assuming that the digitally modulated signal has a
Gaussian amplitude distribution, the signal power within the selected resolution band-
width can be obtained using correction factors. The internal power measurement rou-
tines in a signal analyzer normally use these correction factors to determine the signal
power from IF envelope measurements. These factors apply if and only if the assump-
tion of a Gaussian amplitude distribution is correct.
Apart from this common method, the R&S
FPL also has a true power detector, i.e. an
RMS detector. It displays the power of the test signal within the selected resolution
bandwidth correctly, irrespective of the amplitude distribution, without additional correc-
tion factors being required.
The R&S
FPL1000 software allows you to perform ACLR measurements on input con-
taining multiple signals for different communication standards. A measurement stan-
dard is provided that allows you to define multiple discontiguous transmit channels at
specified frequencies, independent from the selected center frequency. The ACLR
measurement determines the power levels of the individual transmit, adjacent, and gap
channels, as well as the total power for each sub block of transmit channels.
A detailed measurement example is provided in
Chapter 7.2.3.6, "Measurement Exam-
7.2.3.2
Channel Power Results
For channel or adjacent-channel power measurements, the individual channels are
indicated by different colored bars in the diagram. The height of each bar corresponds
to the measured power of that channel. In addition, the name of the channel ( "Adj" ,
"Alt %1" , "Tx %1" , etc., or a user-defined name) is indicated above the bar (separated
by a line which has no further meaning).
Measurements and Results