Rohde & Schwarz FSV3000, User Manual

Page: 157 / 1489

Measurements and results
R&S
®
FSVA3000/ R&S
®
FSV3000
157 User Manual 1178.8520.02 ─ 08
● MSR ACLR configuration ......................................................................................182
● How to perform channel power measurements .................................................... 199
● Measurement examples ........................................................................................204
● Optimizing and troubleshooting the measurement ................................................210
● Reference: predefined CP/ACLR standards ......................................................... 211
● Reference: predefined ACLR user standard XML files ......................................... 212
5.3.1 About channel power measurements
Measuring channel power and adjacent channel power is one of the most important
tasks during signal analysis with the necessary test routines in the field of digital trans-
mission. Theoretically, a power meter could be used to measure channel power at
highest accuracy. However, its low selectivity means that it is not suitable for measur-
ing adjacent channel power as an absolute value or relative to the transmit channel
power. Only a selective power meter can measure the power in the adjacent channels.
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 FSV/A 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 FSV/A 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 5.3.7, "Measurement exam-
ples" , on page 204.
5.3.2 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).
Channel power and adjacent-channel power (ACLR) measurement