Instrument Functions
R&S
®
FSVA/FSV
314Operating Manual 1176.7510.02 ─ 09
● Softkeys for Channel and Adjacent-Channel Power Measurements.................... 324
● Predefined CP/ACLR Standards...........................................................................334
● Optimized Settings for CP/ACLR Test Parameters...............................................336
About Channel Power Measurements
Measuring channel power and adjacent channel power is one of the most important
tasks in the field of digital transmission for a signal analyzer with the necessary test
routines. While, theoretically, channel power could be measured at highest accuracy
with a power meter, its low selectivity means that it is not suitable for measuring adja-
cent channel power as an absolute value or relative to the transmit channel power. The
power in the adjacent channels can only be measured with a selective power meter.
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 correctly display the power of a
pure sine wave signal 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. These correction factors are normally
used by the signal analyzer's internal power measurement routines in order to deter-
mine the signal power from IF envelope measurements. These factors apply if and only
if the assumption of a Gaussian amplitude distribution is correct.
Apart from this common method, the R&S FSVA/FSV also has a true power detector,
i.e. an RMS detector. It correctly displays the power of the test signal within the
selected resolution bandwidth irrespective of the amplitude distribution, without addi-
tional correction factors being required. The absolute measurement uncertainty of the
R&S FSVA/FSV is < 1.5 dB and a relative measurement uncertainty of < 0.5 dB (each
with a confidence level of 95 %).
A detailed measurement example is described in Chapter 2.7.6.1, "Measuring Channel
Power and Adjacent Channel Power", on page 157 and Chapter 4.3, "Remote Control
– Programming Examples", on page 1008.
Measurement Methods
The channel power is defined as the integration of the power across the channel band-
width.
The Adjacent Channel Power Ratio (ACPR), also known as the Adjacent Channel
Leakage Power Ratio (ACLR), is defined as the ratio between the total power of the
adjacent channel to the carrier channel's power. An ACLR measurement with several
carrier (transmission) channels (TX channels) is also possible and is referred to as a
"multi-carrier ACLR measurement".
There are two possible methods for measuring channel and adjacent channel power
with a signal analyzer:
●
IBW method (Integration Bandwidth Method)
●
Zero-span method (Fast ACLR), i.e. using a channel filter
● IBW method.......................................................................................................... 315
● Fast ACLR.............................................................................................................315
Measurement Functions
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